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The Bad Astronomer
2003-Jun-16, 09:41 PM
Hey BABBers-

As part of my day job, I am possibly going to write a black hole FAQ. There already is one on the web (http://cosmology.berkeley.edu/Education/BHfaq.html), but I am looking to be more up-to-date, make it my style, cover other topics, etc.

So (seriously here), what kind of frequently asked questions would you like to see covered in a FAQ? I have my own list, but I want to see what others have. Check out the other one first and see if it didn't answer your questions.

Thanks!

The BA

Glom
2003-Jun-16, 09:45 PM
Does your style mean the trademark bad/good format?

Lets see:
Bad: Sol will collapse into a black hole.
Bad: When it does, Earth will be sucked in.

The Bad Astronomer
2003-Jun-16, 09:50 PM
No, this will be like a real astronomer wrote it. :wink: It'll be a straightforward FAQ, with a question-and-answer format.

tngolfplayer
2003-Jun-16, 09:56 PM
I am interested in knowing how far the gravity from a black hole extends, what the suppossed size of the one in the center of the Milky way is, and how different types of stars become black holes.
Thanks.

Grendel
2003-Jun-16, 10:16 PM
I have only the most rudimentory understanding of how black holes are theorized to work... so any FAQ info will be great from my point of view, as I find them fascinating. The question that has always vexed me... and forgive me if I display my ignorance of current theories on black holes... what happens to matter once it hits the singularity? I was always taught that matter can neither be created nor distroyed... it simply changes states. So what happens to the matter contained within, say, a star that crosses the event horizon and eventually hits the singularity? Is it compressed into the same infintessimally small space as the singularity itself?

Russ
2003-Jun-16, 10:22 PM
1) Is a black hole really black or is it that we just can't see what color it is and it might as well be black? ;)

2) If all of the energy emitted by the accretion disk around a black hole is highly red shifted, shouldn't black holes look red?

3) Could the elusive "dark matter", that is supposed to be most of the mass in the universe, be small, stellar/planet mass, black holes?

4) If a black hole is spinning, wouldn't the space around it be dragged around too, like someone rolling themself up in a blanket? If this is true, does space itself get dragged into the black hole?

These are all questions that I've been asked and to which I wish I'd had a better answer.

Jigsaw
2003-Jun-16, 10:28 PM
My first question is, "How do they know black holes really exist?" So I read this:

Suppose you have found a region of space where you think there might be a black hole. How can you check whether there is one or not? The first thing you'd like to do is measure how much mass there is in that region.
And then my next question is, "How do they do that?" So then I read this:


The mass is measured by observing the speed with which stars and gas orbit around the center of the galaxy: the faster the orbital speeds, the stronger the gravitational force required to hold the stars and gas in their orbits. (This is the most common way to measure masses in astronomy. For example, we measure the mass of the Sun by observing how fast the planets orbit it, and we measure the amount of dark matter in galaxies by measuring how fast things orbit at the edge of the galaxy.)


Which doesn't help.

Still wanna know "howdeydodat?"

:D

As in, "Measure it with what? And howzitwork?" Pretend I have no clue what "very-long-baseline interferometry" is...

Donnie B.
2003-Jun-16, 10:47 PM
I'd like a good, clear explanation of the "negative energy" that's involved in Hawking radiation. I think I have a handle on it, but I feel like I'm on pretty shaky ground.

The simple explanation is that the BH radiates from the event horizon because "negative energy" virtual particles fall into the hole, leaving the "positive energy" particles outside to become Hawking radiation. Somehow the gravitational gradient at the EH makes the inflowing particles seem to be lower than zero energy. That seems pretty, uh, funky...

aporetic_r
2003-Jun-17, 12:10 AM
I would like to see a discussion of the relationship between black holes and galaxy formation. I recall reading an article about a pretty well theorized and researched relationship between black hole mass and galaxy mass, but recently I read something on the web (at space.com, or someplace similar) that new evidence weakens this theory.

Thanks in advance.

Aporetic
www.polisci.wisc.edu/~rdparrish

RBG
2003-Jun-17, 12:10 AM
Yes, Grendel took the words right out of my keyboard.

Paint us a picture of how all this sucked-in matter can exist (?) as a point (or whatever it is.) If I could somehow tour around this point as an imaginary point myself- what would life be like there? This would be one of those exercises like living with 2-D entities.

Cheers,
RBG

tracer
2003-Jun-17, 12:17 AM
Ooh! Ooh! Mista Kotta!

I'd like to see this FAQ delve into the nits of black hole formation. Specifically: What's the upper limit for the mass of a neutron star before it would collapse into a black hole?
Could a neutron star become a black hole by accreting more material in a mass-exchange binary? (I.e. like the way a white dwarf can become a neutron star by exceeding 1.4 solar masses?)
If so, is there any cataclysmic event associated with this collapse of a neutron star into a black hole, like the way a collapsing white dwarf becomes a Type 1a Supernova?
When a big star collapses into a black hole at the end of its life, can it go supernova? Hypernova? Gamma ray burster?
In the case of a white dwarf or neutron star, not all of the progenitor star's mass gets bound up in the white dwarf/neturon star. A star in the process of becoming a white dwarf can shed up to half its mass as a planetary nebula, and a star that becomes a neutron star blasts a lot of itself into deep space as a Type II Supernova. When a star becomes a black hole, does all of its mass get sucked into its event horizon, or will a good deal of it escape into deep space? If the latter, how much will escape?

ToSeek
2003-Jun-17, 12:40 AM
I don't care what you say so long as you start it off properly:



"Well, the thing about a black hole - its main distinguishing feature - is it's black. And the thing about space - your basic space colour - is it's black. So how are you suposed to see them?."
- Holly, Red Dwarf

Klausnh
2003-Jun-17, 01:04 AM
Would a spinning star increase it’s rate of spin as it collapses into a black hole? Could the centrifugal force of the spinning, collapsing stars prevent a collapse into a singularity?

dgruss23
2003-Jun-17, 01:18 AM
A discussion of the time effects for a person falling into a black hole vs. a person observing someone falling into a black hole.

nebularain
2003-Jun-17, 03:15 AM
Well, looking through the list of questions, I do not see:

"Where do black holes come from?" / "How are black holes created (or formed)?"

Then there is the question about the different types of black holes (i.e. supermassive black holes, other massed black holes). Just what are the different ones, are their properties different, location, ...?

There needs to specifically something about the black holes at the centers of the galaxies.

I also wonder about the "picture" we have of black holes: the accretion disk and two jets. Why is it like that? If gravity pulls in from all sides, why is matter coming in from only the disk - or is it only that? Why the disk? How does the disk form? What about those jets? (Not sure how to put all of this into one neat little question, though.)

beskeptical
2003-Jun-17, 03:22 AM
I'd like to see an update on the latest sky surveys as to where and how many black holes or potential back holes appear to be out there.

Massive black holes seem to be in the center of many galaxies, so do we know yet if that is the norm? And have exceptions been found, and are those galaxies different? Is it a time/distance phenomonon? Or not?

Eta C
2003-Jun-17, 03:26 AM
You could add something about the possibility of using black holes as the entry for wormholes. In particular, under what conditions will this be possible. This was a question in some threads about a month ago and despite the SF connotations has been the subject of some recent articles in PhysRevLett. In any case, it's a common question.

Glom
2003-Jun-17, 10:50 AM
I think a question about the formation of black holes (hypernovae, collapsing neutron stars) and the mechanisms behind them would be really good as well as the size of black holes and stuff (Schwarzchild radius).

BTW, what website will this FAQ be posted? (ducking and running) :wink:

Klausnh
2003-Jun-17, 11:15 AM
Difference between Kerr black hole, Kerr-Newman black hole, Reissner-Nordström black hole and Schwarzschild black hole

gbaikie
2003-Jun-17, 11:20 AM
Once a singlarity has formed is there any way in which it can made to be not a singlarity?
If a tiny blackhole evaporates, would it evenually disappear? What's the smallest mass, that black hole could have?

Rue
2003-Jun-17, 01:33 PM
How about dealing with the publics conceptions/misconceptions of what a blackhole would look like. Is a swirling whirlpool of light accurate?
Differences between rotating and non-rotating BH.

WorseAstronomer
2003-Jun-17, 02:59 PM
I'd like to see the similarities and differences between a black-hole singularity and the beginning of time, pre-Big Bang singularity.

SkyEyeGuy
2003-Jun-17, 03:41 PM
What is the difference (okay, besides the obvious) between rotating and non-rotating black holes? Ditto for charged vs. uncharged black holes. I never figured out how a singularity could have any spare electrons, which means I probably missed the whole point of the concept.

I seem to recall reading a discussion of the above, though it was a long time ago, and honestly I couldn't follow much of it.

Another good question might be this -- How common are black holes? How many are you likely to find in a mythical 'average' block of space, say, ten light years on each side?

Too, is it true that every black hole is really the doorway to fantastic adventures (hey, that's what the Sci-Fi channel implies...)

Donnie B.
2003-Jun-17, 05:23 PM
Hehhehheh... Phil, I think you may have opened Pandora's box here. Black holes seem to attract as many questions as they do particles!

Colt
2003-Jun-17, 08:29 PM
This may have already been asked but here goes:

Are Black Holes really circular "drain-type" where there is a flat face toward which everything is being pulled or is it a point at the very center neither above or below the material disk?

I can explain more if no one understands, I don't think I would. -Colt

Chip
2003-Jun-17, 09:59 PM
Hi Phil,

Here are a couple of (loaded) questions:

Do astronomers and physicists think of the singularity within a black hole as a representation for a zone where theory breaks down, or as an actual location of infinite mass?

Does the current understanding of black holes allow for alternative theories about the singularity, and if so, what are they? :wink:

Chip

Klausnh
2003-Jun-18, 12:21 AM
Difference between space and space-time.

Pi Man
2003-Jun-18, 05:14 AM
I would love to see more people educated about black holes and time/space warping such as:

Q: If time slows to zero as one reaches the event horizon of a black hole, how can one say the things fall all the way in?

Q: If time goes "backwards" within the EH of a BH,(Yes, using abbreviations like EH, BH, GR, BABB, BA, etc... makes me feel smart :D ) don't things "fall" back to the EH and get stuck there?

Q: What is a worm hole, and what does it have to do with BH's?

Q: What is Hawking Radiation?

Q: What does "Black holes have no hair" mean?

Q: What is the difference between a white dwarf, a neutron star, and a BH?

Q: Will the sun ever turn into a black hole?

etc... etc... etc...

I'm most interested in astro-physics, posmology and particle physics. You may be wanting stuff that requires a little less math, but these are some questions that interest me. :D

Grand Vizier
2003-Jun-18, 12:20 PM
I'd be interested in the state of play as to actual black hole candidates. The puzzle seems to be that we have many observational candidates in the sense of black holes at galactic centres (particularly spiral galaxies, I think), but very few candidates outside the centres - in our Galaxy, as far as I know, Cygnus X-1 and a mere handful of others.

It seems to say something about the likelihood of black hole formation - i.e. perhaps, outside a galactic centre, this cannot happen as result of a hypernova or supernova, and requires some unusual process (for example a neutron star accreting matter from a companion star). I guess therefore it falls under the FAQ section for 'How do black holes form?'...

earendur
2003-Jun-18, 02:19 PM
Q. What are the relationships between the density and mass of an object as it collapses to form a black hole?

logicboy
2003-Jun-18, 04:24 PM
Q. Are we in any danger, where is the closest black hole that we know of?

informant
2003-Jun-18, 06:46 PM
Something that puzzles me is when people say that inside a black hole space coordinates and time co-ordinates become interchangeable (I'm probably not using the proper terminology).

Russ
2003-Jun-18, 07:01 PM
I know this will sound like a smarta__ questions but it popped to mind as I was reading the suggestions of others.

Do black holes have an upper mass limit? I mean. is there a point at which the mass of a BH cannot increase? I know this seems silly but, I doubt that we have "seen" a BH with a mass exceeding say 6 billion solar masses. So, why not? Why not 60 billion, 600 billion, 6 trillion? Is there a point at which the physics causes it to accelerate everything away? Has there just not been enough time for a bigger one to acrete? Whatsthelimit?

beskeptical
2003-Jun-18, 08:58 PM
Difference between Kerr black hole, Kerr-Newman black hole, Reissner-Nordström black hole and Schwarzschild black hole

There's always a geek in the bunch. :wink:

daver
2003-Jun-18, 10:30 PM
Difference between Kerr black hole, Kerr-Newman black hole, Reissner-Nordström black hole and Schwarzschild black hole

There's always a geek in the bunch. :wink:

Hmm, I don't remember Reissner-Nordstrom black holes from college. You sure those aren't something you get while shopping? :)

honestmonkey
2003-Jun-19, 02:59 PM
This has sorta been asked, but my question is

What does a black hole really look like?

Might be hard to answer in a FAQ. I mean, if you were floating out in space at a safe distance (what is a safe distance? Earth orbit, Jupiter?), what would you see, both with a companion star and without?

I always see pictures that have this squat black ball with a bright swirling thing around its equator, sometimes with the magnetic pole lines drawn in blue. But what would a human see? How much extra equipment would one need to see something interesting?

Pi Man
2003-Jun-20, 05:05 AM
Darn! If HTML/JavaScript was still enabled, I could do this:


<a href="JavaScript:document.write('<body bgcolor=black>');">click here to see what a black hole looks like</a>


P.S. For those who can't make any sense of this, it will create a link that, when clicked, will turn the whole window black. :) :)

Pinemarten
2003-Jun-20, 08:07 AM
If a mime entered a black hole, would it make a noise?
Would anyone care?

Reacher
2003-Jun-20, 04:41 PM
If a mime entered a black hole, would it make a noise?
Would anyone care?
You sound a lot like a disgruntled man who runs a very funny website:
maddox.xmission.com
You'll have to find your own way to the mime page.

And my question:
If two black holes about the same mass were to collide for some reason, what would be the result?
[Edit: The url thing hates me.]

informant
2003-Jun-20, 04:52 PM
And my question:
If two black holes about the same mass were to collide for some reason, what would be the result?
[Edit: The url thing hates me.]

A bigger black hole.
That question's been asked, and answered, here before. I don't have the time to find a link right now.

Klausnh
2003-Jun-20, 09:53 PM
Difference between Kerr black hole, Kerr-Newman black hole, Reissner-Nordström black hole and Schwarzschild black hole

There's always a geek in the bunch. :wink:
Sorry, I did not take my anti-geek medication that day. I'm muuuch better now. Is it true that black holes are responsible for missing socks in the washer. One sock gets pressed to the side and the other gets sucked into the black hole in the spin cycle? :wink:

Klausnh
2003-Jun-20, 09:57 PM
Difference between Kerr black hole, Kerr-Newman black hole, Reissner-Nordström black hole and Schwarzschild black hole

There's always a geek in the bunch. :wink:

Hmm, I don't remember Reissner-Nordstrom black holes from college. You sure those aren't something you get while shopping? :)
You can't buy a Reissner-Nordström black hole. You have to pay for a Schwarzschild black hole with your credit card and then it transforms into a Reissner-Nordström black hole. :wink:

Espritch
2003-Jun-21, 04:55 AM
Why don't black holes all spin at nearly the speed of light? All stars spin. When a star collapses the angular momentum has to be preserved. Wouldn't that imply that the rotation rate would have to increase to something near the speed of light as the matter collapsed down to an infinitely small point?

gethen
2003-Jun-25, 10:57 PM
What about the whole idea of black holes and wormholes and time travel?
At one time someone (Hawking?) speculated about a connection, but I've lost track of the development of that idea. Is it just a mathematical model with no realilty? It's an idea that keeps turning up in bad sci-fi movies and books. Sorry if someone has already suggested this line of thought.

DALeffler
2003-Jun-26, 03:56 AM
Is the rate of black hole formation going up or down? Or maybe: Is the rate the mass of the universe is "losing" behind an event horizon increasing or decreasing?

(I'd think it's going up, but then I dun' thought a lotta things...)

And could the rate disappearing behing an EH be correlated to the rate of the universal expansion? Or maybe, can black holes be a yardstick to the age of the universe?

(I tol' you I thought a lotta differnt' things....)

How many black holes are thought to be in the Milky Way?

Are all black holes inside galaxies?

Do all black holes originate from stars?

If black holes have no hair, then how come all'a different types?

TYVM for your time & patience...

Bill S.
2003-Jun-26, 06:46 PM
I've got a question I'd like to see addressed in the FAQ:

If Time and Space are coterminous, and if due to gravity space is infinitely compressed within a black hole, does time itself cease to be linear within the confines of a black hole, and if so, why then does the black hole not simply wink out of existence the minute it reaches the mass required to start supercompression?

Karthesios
2003-Jun-28, 11:05 AM
Difference between Kerr black hole, Kerr-Newman black hole, Reissner-Nordström black hole and Schwarzschild black hole

There's always a geek in the bunch. :wink:
Sorry, I did not take my anti-geek medication that day. I'm muuuch better now. Is it true that black holes are responsible for missing socks in the washer. One sock gets pressed to the side and the other gets sucked into the black hole in the spin cycle? :wink:

If you live in the Bermuda Triangle, the socks mysteriously multiply in the dryer. Conclusion: White holes exist, and there's one somewhere there.

Klausnh
2003-Jul-01, 01:03 PM
How about a question that's been asked here on the BABB, "Is our space-time inside a blackhole of another space-time? (http://www.badastronomy.com/phpBB/viewtopic.php?t=5760) What evidence do we have to prove or disprove this idea?".

jokergirl
2003-Jul-02, 02:39 AM
Another question I have not seen here (probably because we're all too much geeks for that):

How or what is the matter inside a black hole made of? And how does it differ from, say, the matter inside a neutron star?

;)

Bill S.
2003-Jul-02, 03:18 AM
Another question I have not seen here (probably because we're all too much geeks for that):

How or what is the matter inside a black hole made of? And how does it differ from, say, the matter inside a neutron star?

;)

Hydrogen sans electron shell, isn't it?

jokergirl
2003-Jul-02, 03:23 AM
Another question I have not seen here (probably because we're all too much geeks for that):

How or what is the matter inside a black hole made of? And how does it differ from, say, the matter inside a neutron star?

;)

Hydrogen sans electron shell, isn't it?

Please note the text in the brackets ;) I think we haven't asked that because most of us would know, but others may not.

;)

Glom
2003-Jul-08, 08:39 PM
So when is this piece due to arrive?

cyswxman
2003-Jul-11, 12:27 AM
I asked this in another thread, but I still have difficulty conceiving of an "infinite implosion" which is what the singularity is, theoretically. ](*,)
I would think that due to the subatomic and especially the quantum binding forces, matter would have some lower limit of compaction. Thus, would there be a tiny but incredibly (though not infinitely) dense object in the "center" of the hole. I mean, there must be something in there producing the gravity field, right??? :-k

Bill S.
2003-Jul-12, 12:16 AM
I asked this in another thread, but I still have difficulty conceiving of an "infinite implosion" which is what the singularity is, theoretically. ](*,)
I would think that due to the subatomic and especially the quantum binding forces, matter would have some lower limit of compaction. Thus, would there be a tiny but incredibly (though not infinitely) dense object in the "center" of the hole. I mean, there must be something in there producing the gravity field, right??? :-k

They hit this point, but eventually the "weight" against space/time is so intense that the black hole "dies" via quantum tunneling - the material is literally spit out into a different place in the universe. So I've heard.

Of course I could be misremembering.

AKONI
2003-Jul-17, 08:49 AM
I've never read the actual answer to this question:

What happens to the matter that is sucked inside of a black hole? I know we would get torn apart, but what happens to the atoms that make us up? Where does this mass go? What happens to it?

skyglow1
2003-Jul-18, 10:06 PM
I think the atoms just get torn apart and go "splat!" on the black hole and become a part of it. But what substance is it now?

skyglow1

Jetmech0417
2003-Jul-21, 08:53 AM
There's many many many good questions here, but I'll add my own anyway.

Q: Is there any way that some of these questions could be answered here while the FAQ is being written?

It seems that with so many questions, it's gonna take a looooong time for the BA to actually get the BH FAQ up and running. *shrug* I'm just curious when they'll be answered, 'cause I'm extremely interested.

Another question (may be a bit off topic):
Q: Since something traveling near the speed of light gains mass as it accelerates, if an object ever were to reach C, would it form it's own black hole? (Answers from the resident experts are encouraged.)

digitalspector
2003-Jul-22, 03:54 AM
how about an opinion from someone who has a pretty nice scope...who has a basic understanding...of nature, the universe...and who is willing to learn??

I would like to know.....ultimately what a "black hole" is... i see it as a star that fails...implodes...and its gravity implodes on itself. I understand that the totatl gravity is /was the ultimate mass of the star.....

but what causes the theory of a black hole forming a inter-dimensional portal?

what happens ...if positive matter *light* gets *sucked* in...

i ask on a privy matter.

as I think a black hole, is not a hole...but a star that does not give off light. its matter that is so "negative" it sucks light, matter, neg matter...around it, ultimaltely the gravititational mass must equal the ultimate mass of the orignial star/object. Basically i cant see a star imploding and gaining mass, i see it gaining its original mass in a smaller object.

Explain if i am wrong?

but to the BA i would like to understand the idea that a BH leads to a white hole...or alternate dimension

Since in theory..."?" time is a dimension....and the dimensions relate to each other..so all dimensions lay on each other but at different "time" fragments.......maybe im spinnin to deep.
I hope you guess my basic question.....
which is..
"where does the idea that black holes (which arent holes) lead to alternate universes, dimensions, stem from?????????

sorry for my mass confunsion.

newt
2003-Jul-22, 04:25 PM
Further to AKONI's post:

Would the gravity gradient be able to reduce objects to their constituent atoms in a sufficiently short region of space such that some of the higher elements (or lighter ones for that matter) might escape? Would this result in detectable spectra?
Would a high initial object velocity make a difference (at a tangent)?
Would the reduction release sufficient energy to make any difference to the outcome of some atoms?
Is there a survivable (in terms of the BH's gravity) area near the jets?Kind of a "null" zone?

Thanks, BA. Keep us updated on your progress. Cheers. Newt.

TinFoilHat
2003-Jul-25, 10:55 PM
What's the deal with the Hawking radiation emitted by a black hole?

If we somehow created a small black hole (1 ton size or so), what would the output radiation flux and/or temperature be? Could we use it as a source of power? How long would it take for that black hole to completely evaporate?

Can a black hole hold a charge? Could we use electrostatic or magnetic effects to move or levitate a small black hole?

If you were to drop a black hole into the center of the earth, how large would it have to be for the gravitational pull to overcome the radiation pressure from the hawking radiation sufficiently for the black hole to absorb more mass than it loses by radiation? That is, the minimum size for a black hole that would swallow the earth if dropped rather than just evaporating.

If you had a very large black hole, and were falling into it, what would you see/feel/experience as you fell across the event horizon?

If you had a spaseship with a FTL drive, could you fly in and out of a very large black hole's event horizon without harm?

Ring
2003-Jul-27, 04:05 AM
To a far away stationary observer time comes to a stop at the event horizon. To an observer falling through the event horizon time passes normally. How does the Finkelstein FoR reconcile this seeming contradiction? The FAQ addresses this but I don’t get it.

Since we (Earthlings) are far away stationary observers does this mean all black holes are frozen stars (wrt to us)?

Would an observer closely approaching a BH see the event horizon rushing towards him at the speed of light? Light must travel at light speed and light is trapped at the EH.

At the event horizon the light cone closes up, does this mean an observer suspended just outside the EH would *not* see all time pass for the rest of the universe? Would he be fried by the blue-shifted incoming radiation?

Edited to emphasize "not" in last paragraph

JimTKirk
2003-Jul-30, 09:55 PM
I remember seeing a Discovery Science program about black holes that made a statement that made me wonder.

Basically they said as the mass of the black hole increases to the super-massive level, the gravitational influence decreases.

Would the gravitational influence eventually become zero or produce a negative gravity field?

Would this eventually produce a 'white hole' spewing previously consumed matter back into normal space?

Thanks for producing a great wesite and putting up with our(especially my) many questions! :D

John Kierein
2003-Aug-01, 08:53 AM
FAQ Do Black Holes REALLY exist? Are there more "conventional" alternative explanations that don't require a black hole to explain the observations?

Doodler
2003-Aug-01, 06:46 PM
To a far away stationary observer time comes to a stop at the event horizon. To an observer falling through the event horizon time passes normally. How does the Finkelstein FoR reconcile this seeming contradiction? The FAQ addresses this but I don’t get it.



Would a distress call sent from just outside the event horizon move at less than the speed of light? Given that the effect of a black hole's gravity extends beyond the event horizon, would the still VERY heavy gravity affect the velocity of a photon?

Kaptain K
2003-Aug-01, 07:11 PM
No. The lost energy results in a redshift, not a speed reduction. 8)

Doodler
2003-Aug-01, 08:21 PM
No. The lost energy results in a redshift, not a speed reduction. 8)

One day I gotta ask a photon how it does that, if I could just run faster by blushing, I'd save hundreds of dollars on gas money jogging to work.

John Kierein
2003-Aug-05, 01:54 PM
How about this one. What happens as antimatter encounters a black hole formed by regular matter? Does the black hole get lighter as the matter anti-matter annihilate?

Kaptain K
2003-Aug-05, 02:02 PM
How about this one. What happens as antimatter encounters a black hole formed by regular matter? Does the black hole get lighter as the matter anti-matter annihilate?
Nope! E=mc^2. Or to rewrite it, m=E/c^2. The energy released by the annihilation of matter and antimatter is still trapped inside the black hole, so the total "mass equivalent" does not change. 8)

vivek
2003-Aug-05, 07:30 PM
Hi

My two newbie questions :

1. Why do black holes exist in the center of galaxies ?

2. What would happen if a black hole was not surrounded by matter ? i.e. nothing to 'feed' the black hole.

or

What would happen to a black hole if it finishes 'swallowing' all matter around it ?

-Vivek

daver
2003-Aug-06, 09:55 PM
What would happen to a black hole if it finishes 'swallowing' all matter around it ?

-Vivek

It would s-s-s-s-l-l-l-l-o-o-o-o-w-w-w-w-l-l-l-l-y-y-y-y evaporate. Depending on its size, over time periods that make the current age of the universe seem like the blink of an eye.

At least, this was the story before dark energy. Now, i don't know.

nokton
2003-Aug-13, 06:21 PM
Hey BABBers-

As part of my day job, I am possibly going to write a black hole FAQ. There already is one on the web (http://cosmology.berkeley.edu/Education/BHfaq.html), but I am looking to be more up-to-date, make it my style, cover other topics, etc.

So (seriously here), what kind of frequently asked questions would you like to see covered in a FAQ? I have my own list, but I want to see what others have. Check out the other one first and see if it didn't answer your questions.

Thanks!

The BA
Anyone serious about grasping the concept of a black hole in 3 dimensions,ever considered that space may differ in density
determined by gravity,and the concept of this can be understood
by relating gravity to a colour?
Nokton

Kaptain K
2003-Aug-13, 06:25 PM
??????????

nokton
2003-Aug-13, 07:16 PM
Hi Mon Capitan,
There are no gods,thought you would have grown
beyond diatribe and embraced science and new concepts.
The opponents of Darwin welcome you

nebularain
2003-Aug-14, 11:59 PM
OK, my turn.

??????????????????


OK, seriously,
*nokton - KaptainK was saying that he did not understand what you were saying.

And I think you missed the point of his signature line. It's a bit of an artistic expression.
8-[

Kaptain K
2003-Aug-15, 12:49 PM
Thanks Neb!

My sig is merely a quote that caught my eye. It is one of several I have used since I joined this board. Whether I believe in God (or gods, for that matter) is immaterial and irrelevant!

?????????? means that I did not (and still do not) understand nokton's first post. :-? :-s

Rue
2003-Aug-19, 08:59 PM
Anyone serious about grasping the concept of a black hole in 3 dimensions,ever considered that space may differ in density
determined by gravity,and the concept of this can be understood
by relating gravity to a colour?
Nokton

Do you mean illustrating the relationship of gravity and distance with colours?

nokton
2003-Aug-19, 09:17 PM
Hi Rue,
Was trying to grasp space,not as a fabric,but a colour,with density.
Gravity controlling the depth of the colour.Hope you understand my concept Rue.Thankyou

The Bad Astronomer
2003-Aug-21, 12:07 AM
These are all really good questions! I appreciate the help.

This FAQ will actually be a part of my day job websites (GLAST (http://glast.sonoma.edu), Swift (http://swift.sonoma.edu), XMM-Newton (http://xmm.sonoma.edu)). These satellites observe lots of objects that have black holes in their hearts, so a FAQ seems like a good idea.

There already is a FAQ out there (Ted Bunn's Black Hole FAQ (http://cosmology.berkeley.edu/Education/BHfaq.html)) but I wanted one with more popular-level appeal, maybe even for schoolkids.

I am also developing a popular-level public talk on black holes, and I'm trolling (!) for ideas. I have it mostly drafted out, but a couple of topics brought up here may make good things to mention in the talk too.

I knew y'all would come through! Thanks!

bachus
2003-Aug-24, 10:27 AM
Taking the risk of being called an idiot:

Since we know neutrino's hardly interact with normal mass, is it for a neutrino possible to escape from beyond the event horizon?

nokton
2003-Aug-24, 06:41 PM
Hi Bachus,never would regard you as an idiot,an enquiring mind yes.
Read Hawkings theory of how black holes will eventually dissipate.
Think he makes sense.Am not into understanding,or venturing opinions
about that I do not understand,but do question the 'experts' at times.
Try to think always in reason and logic,not tied to rote learning.
This really is what this site is all about,and what a wonderful site it is.
You and I can express our opinions here,we may not have PHDs,
but by hell we have brains and intellect,this is what the founder of
this site in his wisdom realised.Thanx,BA.

Zamboni
2003-Aug-31, 05:08 AM
If quantum theory says that an event must be observed to exist then can we just say by the same logic that black holes do not exist since nothing can be observed beyond the horizon.

Chip
2003-Aug-31, 08:17 AM
If quantum theory says that an event must be observed to exist then can we just say by the same logic that black holes do not exist since nothing can be observed beyond the horizon.

Hi,

To paraphrase Einstein’s criticism of the Copenhagen interpretation: "Do you really think a black hole isn't there if you aren't looking at it?" :wink:

Zamboni
2003-Aug-31, 02:05 PM
@Chip... or Einstein:
No, I'm saying that it's not there even when I do look at it. Although the fact that we can observe its gravitational field defeats my last post...

numbskull
2003-Sep-02, 04:57 PM
Dear Mr Bad Astronomer,

Question for the Black Hole FAQ here (http://www.badastronomy.com/phpBB/viewtopic.php?t=7795) in General Astronomy. (Didn't want to repeat the question.)

RickNZ
2003-Sep-05, 12:28 AM
Id like to see a case comparing how much we THINK we know vs how much we KNOW we know thru direct observation.

pghnative
2003-Sep-06, 01:06 AM
Hope this isn't a repeat, but one question I'm interested in is how convinced are scientists that there are no sub-atomic particles denser than neutrons.

In other words, why do the things we observe as black holes actually have to be considered singularities of zero volume. If they had a smidgen of volume (forgive the technical jargon), wouldn't they still attract mass at a tremendous rate, causing X-ray emissions and all of the other phenomena associated with "black holes"

vuo
2003-Sep-09, 01:31 AM
Not that I had problems with these questions, but finding answers was difficult.

Why isn't the gravity - and acceleration into the hole - infinite if density and the gravitational well are infinite?

Is there any more analysis on the quantum mechanics of a black hole than the Hawking radiation theory?

Does general relativity _necessarily_ imply black holes?

Is the singularity a particle?

The state-of-the-art wormhole research results and ideas?

Can you see black hole accretion disks with an optical telescope? If so, how big a telescope?

(There is one quasar you can see with an amateur telescope. It'd be cool if there were accretion disks to see.)

Pinemarten
2003-Sep-12, 10:38 AM
I just became curious as to another question.

Is there a minimum or maximum size for black holes?

Can we make a little one in 'the lab'?

Would a 'granddaddy' take out the universe?

I think I will post this in the "Black Hole FAQ" sticky thread as well.

http://www.badastronomy.com/phpBB/viewtopic.php?p=139759#139759

Solfe
2003-Sep-12, 10:46 AM
If a distant observer cannot see objects fall into a black hole, instead they see a fainter and fainter object approaching the event horizon, how long until this object disappears from sight? How long could an image be viewed with instrumentation?

Solphe

George
2003-Sep-17, 01:23 PM
Can a BH and it's EH oscillate? (Say from the impact of a massive star)

If so, might it resonate? (If the EH expanded breifly would it "gulp" enough matter to cause another EH expansion and another "gulp"?)

If so, could we not determine much about it from this resonance?

If so, would it cause the B flat note as per this
>>> thread <<< (http://www.badastronomy.com/phpBB/viewtopic.php?t=7969).

If so, what tune does the Milky Way sing? :-({|=

Visitor
2003-Sep-17, 08:09 PM
I am interested in knowing how far the gravity from a black hole extends, ...

Maybe a small epilogue about the force "gravitation", or even about the 4 basic forces (hope this means in english what i want to say) would be desirable.

The question should IMHO be something like "What is the safe distance from a black hole".
And the answer should begin with "It depends on..." ;)

George
2003-Sep-18, 02:40 PM
I did not see this question asked yet (if it was, here's a provisional oops... :-?)....

How many black holes may be out there (in the universe)?

Wouldn't the early universe spawned many?

If so, would there be many rogue BH's?

If so, would they leave some sort of detectable "vapor trail" as they trek through galactic disks?

If so....well, do you even want another "if so"?

Have you had enough questions yet? :D

Ari Jokimaki
2003-Oct-09, 05:05 PM
I have often seen mentioned, that when matter reaches the singularity in black hole, it sort of disappears from this universe. I'm just wondering that if this is true, wouldn't the gravity of that matter disappear too? And since all the matter lies in the singularity, wouldn't this mean that gravity of the black hole would be zero?

brian1905
2003-Oct-13, 03:03 PM
my main question was mentioned by Pi Man:
GR predicts a complete stopping of time inside the event horizon. Does this mean everything (from an outside POV) would never reach the singularity? If so how could it's mass increase?
Could this problem be overlooked if we considered the entire black hole as a macroscopic point in space? (macroscopic to an outside observer, but a dimentionless point from the inside). is this a fool's question?

wrd999
2003-Oct-14, 06:04 PM
I hope I'm not too late with this question...I remember a remark by Isaac Asimov in one of his books (from many years ago) that the overall density of a black hole would decrease as it increases in size. He conjectured that if the hole were big enough, the density at any point could be slight - he even threw out the suggestion that the universe itself might be a black hole. Unfortunately, I can't recall which book I read it in (he only wrote hundreds of them!) But I thought it was an interesting point, and always wondered how valid it was.

The Bad Astronomer
2003-Oct-21, 10:19 PM
Just a note to let y'all know I am still thinking about all this.

I'll also point out again that there is a BH FAQ on the web (http://cosmology.berkeley.edu/Education/BHfaq.html), which answers quite a few of the questions asked in this thread! :D

Sister Ray
2003-Nov-01, 06:36 PM
If you talk about black holes, you have to also explain what a neutron star is and how it is created. I'm an English major (I also have a science geek aspect, as well as a history and musical one. My math gene mutated so much I can't be without a calculator) and wrote a poem for a class about a neutron star. Everyone in class got a copy, and I got 25 pages back with the exact same question on them - "What's a neutron star?" (I won't even get into the pseudo-villanelle I wrote about color rays.)

JohnD
2003-Nov-03, 10:39 PM
Would an antimatter black hole be distinguishable from one formed from normal matter?
Is this where all the antimatter created in the Big Bang has gone?
Why?
John

Espritch
2003-Nov-06, 12:00 AM
There was a discussion thread on JREF that got me thinking. Is it possible to have a black hole that is not massive enough for complete collapse. I.e. could a neutron star or quark star have enough mass to keep light from escaping but not enough to overcome the resistence to collapse caused by the neutron or quark degeneracy? I imagine such a black hole would be pretty much indestinquishable from a true black hole from the outside. However, if it lost enough energy due to Hawking radiation it's mass could drop below the Swartchild radius and suddenly the black hole would revert to a neutron star or quark star.

On the other hand, if it swallowed enough additonal matter to cause a total collapse, would an outside observer register anything besides a slight increase in the radius of the event horizon (due to the added mass)?

Kaptain K
2003-Nov-06, 12:36 PM
Would an antimatter black hole be distinguishable from one formed from normal matter?
No! Antimatter has mass, not antimass. A black hole has only three distinguishing characteristics: mass, charge and spin. As Hawking said, "A black hole has no hair".

Is this where all the antimatter created in the Big Bang has gone?
Probably not.

Hat Monster
2003-Nov-15, 03:33 AM
Some more basic level questions. Of course, anybody reading this should know the answer. But Phil mentioned he wanted to maybe include school kids in the reading audience.

Q: Where's the nearest black hole?
A: An object designated V4641 Sgr in Saggitarius at a distance of 1,500 light years.

Q: What's a microquasar?
A: A stellar black hole which blasts out jets from each pole behaves a little like a quasar but is billions of times smaller and less powerful.

Q: How big does a star have to be to form a black hole?
A: The core remnant has to be massive enough to collapse against neutron degeneracy pressure. The exact value is unknown, but seems to be over 2 solar masses. This corresponds to a star greater than 18 solar masses.

Q: If black holes are so black, how can we see them at all?
A: Black holes are named because they absorb everything that passes the event horizon. Outside the event horizon is a very energetic place and may glow strongly across the electromagnetic spectrum. From doppler shifts we can calculate the orbit of material around the black hole and so deduce how massive the black hole has to be to hold the material in this orbit. From this we can also work out a diameter for the event horizon or surface. If the calculated density is greater than a neutron star can be, then we probably have a black hole.

Q: Does our galaxy have a supermassive black hole?
A: A star was tracked within seventeen light hours of the suspected supermassive black hole in our galaxy. Some space probes are further from the Sun than seventeen light hours! The velocity of the star was so great that a very small object with an extremely huge mass must have pulled it along the orbit, inferring the presence of a supermassive black hole.

Q: Could the "missing mass" or "dark matter" be small black holes?
A: We know that stars of the sort of mass needed to create a stellar black hole are formed and don't live very long. However, it's theorised that stellar black holes are transient objects and evaporate over time. It's certainly worth considering that there could be lots of smaller black holes out there and galactic halo microlensing studies are looking for them.

There we go. And damn, those icons at the left of the post box are sure distracting.

H@

Oops
2003-Nov-27, 01:39 AM
I'm not up to reading all of the proposed questions. Can someone with more time compile them and point me to the list?

Not all of these questions are about black holes, but they are related:

How does the spread of matter affect gravity?
If you can theoritically create a black hole .9cm across out of Earth's mass, would it be stable, and if so, why doesn't the Earth become one (i.e., what does this hypothetical crushing scenario leave out or oversimplify)?

Can black holes/neutron stars have magnetic fields/How can a black hole/neutron star have a magnetic field?

What is a Planck Particle?

How big is a singularity?

What is negative gravity? What has negative gravity?

What is a graviton? How do black holes interact with gravitons?

What are quasars? How do they form, and why are they all so old?

Can we create black holes? How big would they be? What would be the dangers of creating one?

What is the minimum density required for something to become a neutron star/quark star/black hole?

I read that black holes actually suck in spacetime. If they do, what observable effect does this have? Is there a limit to how much spacetime can stretch?

What is orbital velocity just outside the event horizon?

Glom
2003-Nov-27, 12:19 PM
How does the spread of matter affect gravity?

Outside the mass, it has no affect. If the Sun were to collapse cleanly into a black hole, aside from the fact it would be darker, we wouldn't notice it. It's only within the mass that the distribution changes.


If you can theoritically create a black hole .9cm across out of Earth's mass, would it be stable, and if so, why doesn't the Earth become one (i.e., what does this hypothetical crushing scenario leave out or oversimplify)?

The electrostatic repulsion of the electron clouds (for classical mechanics fans), or the Pauli Exclusion Principle (for quantum mechanics fans) means that there is far too much resistance to Earth being crushed down to a centimetre.


Can black holes/neutron stars have magnetic fields/How can a black hole/neutron star have a magnetic field?

Yes and they do. Neutron stars have powerful magnetic field that are responsible for the polar jets. It's all to do with movement of neutrons of something.


How big is a singularity?

I doesn't have size. It's singular.


What is a graviton? How do black holes interact with gravitons?

The graviton is the theoretical exchange particle between masses that causes them to attract gravitationally.


What are quasars?

They are distant galaxies with supermassive black holes that are on a feeding frenzy. As superheated materials spirals towards the event horizon, the materials outshines the galaxy itself.


Can we create black holes? How big would they be? What would be the dangers of creating one?

I believe the guys with the big accelerators are trying to create microscopic singularities. I doubt they'd be that much of a problem. They wouldn't have much mass.


What is orbital velocity just outside the event horizon?

Presumably approaching c.

ToSeek
2003-Nov-27, 03:48 PM
What is orbital velocity just outside the event horizon?

Presumably approaching c.

If escape velocity at the event horizon is c (by definition), then orbital velocity would be c/sqrt(2).

Oops
2003-Nov-28, 10:22 PM
How does the spread of matter affect gravity?

Outside the mass, it has no affect. If the Sun were to collapse cleanly into a black hole, aside from the fact it would be darker, we wouldn't notice it. It's only within the mass that the distribution changes.

This question isn't directly about black holes. I'm really confused about gravity in general.


If you can theoritically create a black hole .9cm across out of Earth's mass, would it be stable, and if so, why doesn't the Earth become one (i.e., what does this hypothetical crushing scenario leave out or oversimplify)?

The electrostatic repulsion of the electron clouds (for classical mechanics fans), or the Pauli Exclusion Principle (for quantum mechanics fans) means that there is far too much resistance to Earth being crushed down to a centimetre. :-s Can you give me more detail? Remember, I'm still in high school.



Can black holes/neutron stars have magnetic fields/How can a black hole/neutron star have a magnetic field?

Yes and they do. Neutron stars have powerful magnetic field that are responsible for the polar jets. It's all to do with movement of neutrons of something.Do we know what nucleons are made of? The quark explanation seems to have giant gaps in it.



What is a graviton? How do black holes interact with gravitons?

The graviton is the theoretical exchange particle between masses that causes them to attract gravitationally.What I meant is, how is gravity transmitted if it moves at the speed of light? After all, light itself can't escape a black hole.



Can we create black holes? How big would they be? What would be the dangers of creating one?

I believe the guys with the big accelerators are trying to create microscopic singularities. I doubt they'd be that much of a problem. They wouldn't have much mass.
I'm looking for something more specific.

Thanks for responding, but I don't need the answers here. These are just my suggestions. I'm responding to the response because I got one, but I don't need another one. 8)

Glom
2003-Nov-28, 11:38 PM
This question isn't directly about black holes. I'm really confused about gravity in general.

According to Newton's Law of Universal Gravitation, all masses attract other masses according to the law

F = GMm/r²

This law refers to the attractive force between two point masses (ie particles). A particle is an object that considered to have no size in space (essentially a singularity, but since this is pre-GR, we don't have to worry about this black hole crap). From this simple law, we can, with the help of loads of complicated mathematics, we can derive the behaviour of gravity when dealing with real objects that actually have volume in space.

Now, lets assume we have a point mass, a satellite, in orbit of a large perfect, uniform sphere. We can imagine that the sphere is composed of a whackload of point masses (it is this treatment that allows us to use a lot of important principles like centres of mass and moment of inertia). When we add up the attractive force of all constituent point masses of the sphere on the satellite, we find that the resultant is a gravitational force directed towards the centre of mass of the sphere, of magnitude corresponding to the sum mass of the sphere.

Without all the verbal diarrhoea, what that means is that the force of gravity from the sphere is as though the sphere were really a point mass. Hence, as long as the satellite remains outside the sphere, we can ignore that fact that the sphere has volume, and hence mass distributed all over the place, and treat it as though it was a point mass located at the centre of mass.

Removing even more diarrhoea, the spread of mass makes no difference as long as you're outside the object. Once inside, things get trickier because you have attractions from all sides.

No doubt someone will bring up lots of weird shapes that could violate this rule, but I'll elaborate further when they do.


:-s Can you give me more detail? Remember, I'm still in high school.

Pauli is difficult, I've read briefly about it, but don't know much. I myself am only a first year university student. Basically, the Pauli Exclusion Principle says something about electrons not wanting to be doing the same thing in the same place and that somehow makes it worse.

Using the classical model, although not entirely accurate, will probably paint a better picture.

Let me put it this way. Gravity is crap! There are four fundamental interactions and gravity is the weakest. Two of them have no prescence beyond about a nuclear radius so they aren't that related. That just leaves the electromagnetic interaction. Electromagnetic vs gravitational? That's like pitting Mr. Burns against McBane! Think about the apple that hangs above Newton's head. It's being held on the tree by the forces of the electric attractions in the stalk and they are enough to balance the gravitational attractions of the entire planet! The reason why gravity seems so prominent in space is because the EM interaction can be both attractive and repulsive and over large scales, these two facets tend to cancel each other out.

But when you get onto the scale of atoms, gravity doesn't stand a chance. It's all EM. As you read this, sitting on your chair, why don't you fall through it? A honkin' great big planet is pulling you down. Why do you stay up? It's because all atoms are surrounded by clouds of electrons, negatively charged particles. You know the rule: like charges repel. So the electron cloud in you butt is repelled by the electron cloud in you chair. That pushes you up and allows you to not fall through it. It's a similar thing that keeps large masses from collapsing into black holes and the like. The electron clouds in the atoms repel each other and keep a safe distance. It's only when complicated stellar stuff happens that puts a whack load of energy into the system can these forces be briefly overcome to change the tables a bit.

The point is that the Earth is held in its shape by the repulsion of the subatomic particles. This is more than sufficient to overcome gravity's piddly influence.

But if you were to put in the energy required for the compression to make a black hole, that would involve changing the form of the matter such that the electron clouds were no longer present. In neutron star formation, the enormous shock compression from the complicated stellar stuff compresses the atoms and essentially shoves the electrons into the nucleus. Protons and electrons combine to form neutrons. Hence you get a honkin' great big ball of neutrons: the neutron star. But, at this point, the electron clouds are gone and so we're talking different stuff here.

If it were possible to compress Earth into a neutron star, it would be okay and would be stable (I think), but that's because the matter has undergone a change.


Do we know what nucleons are made of? The quark explanation seems to have giant gaps in it.

We're getting really frontier and perhaps the particle physicists on the board could give a better response. If you state the problems you have with the quark model, I'm sure they'd be able to respond. And I'm sure they could give a better explanation of the source of the B-fields in black holes and neutron stars.


What I meant is, how is gravity transmitted if it moves at the speed of light? After all, light itself can't escape a black hole.

Congratulations, you've hit upon the one barrier in the completion of the Grand Unification Theory. Theoretical physicists are having trouble with quantum gravity. Black holes were predicted by GR, which is classical. Gravitons are a part of quantum mechanics. The two have yet to be reconciled, although I'm sure there will be those who'll correct me.


Thanks for responding, but I don't need the answers here. These are just my suggestions. I'm responding to the response because I got one, but I don't need another one. 8)

Well, I read as I replied so I read this after I'd already responded, hence you're getting one! :P The questions are good though.

Oops
2003-Nov-30, 05:55 AM
How big is a singularity?

I doesn't have size. It's singular.
I just remembered why I suggested this question. Consider Planck Length and the resolution of the Universe (or whatever the technical term is for this stuff). Now, what is the answer to the original question?

The Supreme Canuck
2003-Nov-30, 06:13 AM
I'm not sure, but that may be wrong. Behind an event horizon, physics break down. They don't work the way they should. The Planck Length may not apply.

Glom
2003-Nov-30, 11:16 AM
The idea of the singularity is classical while the Planck length is quantum. The two concepts have yet to be reconciled.

Cunninglinguist
2003-Dec-03, 04:03 AM
Light cannot escape?

So this proves that light is made of a particle not a wave? Right?

tuffel999
2003-Dec-03, 05:09 AM
No light acts as both.
http://www.nobel.se/physics/articles/ekspong/

Diamond
2003-Dec-03, 08:50 AM
Can I ask: What is dark matter and what behavior of galaxies (and the Universe) does it help explain?

Glom
2003-Dec-03, 11:47 AM
Can I ask: What is dark matter and what behavior of galaxies (and the Universe) does it help explain?

Probably a bit OT. Some have explored the possibility that black holes are one explanation for dark matter so it might be worth commenting on that.

Lorcan Faol
2003-Dec-04, 08:30 AM
I don't have the time at the moment to look through every question that was asked, so if this one was already asked, ignore it.
How fast would something be pulled into a blackhole? I know it would probably depend on the weight of the object and the size of the blackhole, as well as how far inside the object has been pulled, but is there any kind of formula to determine this yet?

Diamond
2003-Dec-04, 09:59 AM
I don't have the time at the moment to look through every question that was asked, so if this one was already asked, ignore it.
How fast would something be pulled into a blackhole? I know it would probably depend on the weight of the object and the size of the blackhole, as well as how far inside the object has been pulled, but is there any kind of formula to determine this yet?

That's a really difficult question to answer. It depends on the frame of reference. From a far away observer, the object would appear to redden and slow down, and from that point of view the object would end up on the event horizon with zero velocity.

Try Exploring Black Holes by Taylor and Wheeler (http://www.amazon.com/exec/obidos/tg/detail/-/020138423X/qid=1070531894/sr=1-3/ref=sr_1_3/102-7528096-5970553?v=glance&s=books) and find out.

Lorcan Faol
2003-Dec-04, 06:01 PM
I don't have the time at the moment to look through every question that was asked, so if this one was already asked, ignore it.
How fast would something be pulled into a blackhole? I know it would probably depend on the weight of the object and the size of the blackhole, as well as how far inside the object has been pulled, but is there any kind of formula to determine this yet?

That's a really difficult question to answer. It depends on the frame of reference. From a far away observer, the object would appear to redden and slow down, and from that point of view the object would end up on the event horizon with zero velocity.

Try Exploring Black Holes by Taylor and Wheeler (http://www.amazon.com/exec/obidos/tg/detail/-/020138423X/qid=1070531894/sr=1-3/ref=sr_1_3/102-7528096-5970553?v=glance&s=books) and find out.

Yeah, I knew about that much. Isn't it true that from the outside observer, the object would never actually seem to get to the event horizon? I could be mistaken, though.

russ_watters
2003-Dec-04, 08:48 PM
If you can theoritically create a black hole .9cm across out of Earth's mass, would it be stable, and if so, why doesn't the Earth become one (i.e., what does this hypothetical crushing scenario leave out or oversimplify)?

The electrostatic repulsion of the electron clouds (for classical mechanics fans), or the Pauli Exclusion Principle (for quantum mechanics fans) means that there is far too much resistance to Earth being crushed down to a centimetre. I could be wrong here, but I think you're looking at the question backwards, Glom. How it becomes a black hole isn't the question. The question is: would a black hole of earth's mass be stable? The answer is yes.

The earth will never FORM a black hole due to its gravitational field not being strong enough to crush it, but it is possible for there to BE a stable black hole with earth's mass.

It is possible (for example) for a star to go supernova, form a black hole, then evaporate for a while to become the same mass as the earth.

Is that what you were looking for, Oops?

Glom
2003-Dec-04, 09:55 PM
I am aware of that, but part of Oops's question was, if a singular Earth is a stable state, why doesn't Earth become one? The answer is that there is a great big honkin' potential energy peak seperating the current state, with the singular state. I was attempting to address that question.

Kaptain K
2003-Dec-04, 10:42 PM
russ_watters,
An "Earth mass" black hole would not be "stable" (at least, long term). It would eventually evaporate due to Hawking radiation. A stellar mass black hole cannot evaporate down to Earth mass and then stop. In fact, the evaporation goes up exponentially with decreasing mass.

Oops
2003-Dec-05, 02:13 AM
On the Earth black hole question:
If a tiny black hole with Earth's mass could exist, does the same apply to a neutron star? Is the size equilibrium determined by the state of matter (atoms, neutrons, black hole)? (Is there a technical term for this type of state, or does it get lumped in with temperature dependent states?)

Why would smaller black holes evaporate faster?

russ_watters
2003-Dec-05, 06:37 AM
russ_watters,
An "Earth mass" black hole would not be "stable" (at least, long term). It would eventually evaporate due to Hawking radiation. A stellar mass black hole cannot evaporate down to Earth mass and then stop. In fact, the evaporation goes up exponentially with decreasing mass. I'm aware of that but I think thats a little nitpicky. No black hole is really "stable" then unless there is a source of matter feeding it at exactly the rate it is evaporating.

In any case, that leads to a question: how long WOULD an earth-mass black hole last and at what mass does a black hole 'explode'? Meaning, does the energy emission just go up exponetially until there is nothing left or is there a certain threshold at which all thats left goes off in one shot?
I am aware of that, but part of Oops's question was, if a singular Earth is a stable state, why doesn't Earth become one? Oops- I missed the second part of the question. My bad.

Kaptain K
2003-Dec-05, 12:24 PM
On the Earth black hole question:
If a tiny black hole with Earth's mass could exist, does the same apply to a neutron star?
No.

Is the size equilibrium determined by the state of matter (atoms, neutrons, black hole)?
Yes.

Is there a technical term for this type of state, or does it get lumped in with temperature dependent states?
Degeneracy.

Why would smaller black holes evaporate faster?
The "surface area" of the event horizon is proportional to the square of the Schwartzchild radius, but the volume is proportional to the cube. So, the surface area decreases more slowly than the volume with decreasing radius (proportional to the mass).

Oops
2003-Dec-06, 03:36 AM
On the Earth black hole question:
If a tiny black hole with Earth's mass could exist, does the same apply to a neutron star?
No.

Is the size equilibrium determined by the state of matter (atoms, neutrons, black hole)?
Yes. Could you elaborate?

Oops
2003-Dec-06, 03:41 AM
I am aware of that, but part of Oops's question was, if a singular Earth is a stable state, why doesn't Earth become one? The answer is that there is a great big honkin' potential energy peak seperating the current state, with the singular state. I was attempting to address that question.There is a little more here. What keeps electrons from being sucked into the nucleus, and what keeps electrons that have been crushed into the nucleus from popping back out? The answer to this will be the answer to the original question (I think).

Kaptain K
2003-Dec-06, 01:01 PM
On the Earth black hole question:
If a tiny black hole with Earth's mass could exist, does the same apply to a neutron star?
No.

Is the size equilibrium determined by the state of matter (atoms, neutrons, black hole)?
Yes. Could you elaborate?
In "normal" matter, atoms and molecules are held apart by the electrostatic repulsion of the electrons surrounding the nuclei. In plasma, it gets a little more complicated. The (free) electrons still repel each other. Protons (and other nuclei) also repel each other. Electrons are prevented from merging with nuclei by the nuclear forces. Although white dwarfs are extremely dense (thousands of kilograms per cubic centimeter), they are still plasma. If the pressure gets high enough, the electrons combine with protons and a neutron star (degenerate matter) results. Normal stars range in size from a few hundred thousand kilometers in diameter (red dwarfs) to a couple of billion of kilometers (super giants). White dwarfs are a few thousand kilometers in diameter. Neutron stars are only a couple of kilometers across. Once the nuclear forces that keep the neutrons separate is overcome, there is nothing to stop the matter from collapsing completely It shrinks to a point mass of infinite density, surrounded by an event horizon, that we call a black hole.

Glom
2003-Dec-06, 02:25 PM
There is a little more here. What keeps electrons from being sucked into the nucleus, and what keeps electrons that have been crushed into the nucleus from popping back out? The answer to this will be the answer to the original question (I think).

You bring up the question that led to quantum mechanics. At a time before QM, scientists were trying to find out the nature of matter. It first began with the Ancient Greek Democritus, who, unlike his peers at the time who believed that matter would always exist no matter how small, believed that matter was made of indivisible sphere, called atoms (Greek for indivisible).

In the modern era, scientists were able to determine that there was indeed a discreet subdivision of matter and they were able to measure its size.

JJ Thomson discovered the electron at the turn of the twentieth century and, modifying Democritus, came up with the so called Plum Pudding model of the atom. The atom was composed of a more or less homogeneous positively charged material, kind of like a cytoplasm, and these electrons were dotted around inside it. This leads to a neutral atom, as observed.

Then Rutherford came along, or more appropriately, his apprentices, Geiger and Marsden came long. They conducted the famous gold foil experiment, where they allowed a collimated stream of alpha-particles to strike a thin leaf of gold foil. They then detected the directions in which the alpha-particles were scattered. Most went straight through and were detected on the other side of the foil, indicating the atom was mostly empty space. Some, however, were deflected, through surprising great angles. From Coloumb's Law, the Thomson model of the atom wouldn't be sufficient to provide such high energy changes, such that the alpha-particles would be scattered that much. Indeed, the only way this would be possible would be if the positive charge of the atom was much smaller than originally believed and hence much more concentrated.

But, this led to problems. If the positive charge, rather than being a cytoplasm, was more of a nucleus, then what about the electrons? Something was causing the atom to claim a much larger volume of space than the nucleus alone. So, the solar system model of the atom was born. This depicted electrons orbiting the nucleus like a nanoscopic solar system.

But, this too didn't work. Electrons are charged particles and when charged particles are accelerated, they radiate electromagnetic radiation. This would mean that as the electrons orbited, they'd lose energy and spiral into the nucleus.

Hail, Niels Bohr. He supposed quantisation. He suggested that electrons in the atom can only occupy discreet energy levels and the only time energy is transferred is when an electron moves between these energy levels.

Loads of scientists, nobel prizes and complicated maths later and the electron is now described as a probability wave in the atom. It can only exist as a standing wave, which means in order for it to be a standing wave in the atom, it must have certain wavelengths and therefore certain energies. Those energies don't include ones where the electron would fall into the nucleus.

Oops
2003-Dec-06, 07:20 PM
In "normal" matter, atoms and molecules are held apart by the electrostatic repulsion of the electrons surrounding the nuclei. In plasma, it gets a little more complicated. The (free) electrons still repel each other. Protons (and other nuclei) also repel each other. Electrons are prevented from merging with nuclei by the nuclear forces.What exactly do you mean by this last sentence?

...Neutron stars are only a couple of kilometers across. Once the nuclear forces that keep the neutrons separate is overcome, there is nothing to stop the matter from collapsing completely It shrinks to a point mass of infinite density, surrounded by an event horizon, that we call a black hole. Then why do neutron stars exist in the first place? Why can't a neutron star of Earth's mass exist?

Oops
2003-Dec-06, 07:26 PM
...Loads of scientists, nobel prizes and complicated maths later and the electron is now described as a probability wave in the atom. It can only exist as a standing wave, which means in order for it to be a standing wave in the atom, it must have certain wavelengths and therefore certain energies. Those energies don't include ones where the electron would fall into the nucleus.So how do neutron stars form?

What is Coloumb's Law?

Glom
2003-Dec-06, 07:30 PM
In massive stars, during its main sequence, the explosive pressure of the hydrogen reaction is balanced by the implosive pressure of gravity. When the hydrogen is exhausted, there is no more explosive pressure and so the star begins to collapse. This collapse generates heat and is sufficient to start up helium fusion, which again gives explosive pressure. When the helium runs out, it works onto lithium and so on until the core becomes made of iron. Iron is the peak of nuclear stability and fusing it into heavier elements consumes more energy than it releases. Hence, you don't get any more explosive pressure and so the star collapses without remit. Remember, this happens in massive stars, so you have a lot of mass now undergoing a catastrophic collapse. The implosive pressure is enough to cause everything to go haywire and the iron core is crushed into a neutron star.

Glom
2003-Dec-06, 07:33 PM
Coulombs law:

Electric force = Product of charges ÷ (Distance squared × 4 × pi × permitttivity of free space)

Kaptain K
2003-Dec-06, 07:58 PM
Oops wrote:

Kaptain K wrote:


In "normal" matter, atoms and molecules are held apart by the electrostatic repulsion of the electrons surrounding the nuclei. In plasma, it gets a little more complicated. The (free) electrons still repel each other. Protons (and other nuclei) also repel each other. Electrons are prevented from merging with nuclei by the nuclear forces.

What exactly do you mean by this last sentence?
It has been 30 years since I studied this seriously in college. Since then, I have just been an interested layman, so I may be a little rusty. If I have made any serious errors, I'm sure that somebody will jump in and correct me. There are four forces in the universe: Gravity, electromagnetic, weak nuclear and strong nuclear. Gravity and electromagnetic forces are infinite in scope and fall off with the inverse square of distance. The nuclear forces are short range and are only effective at distances on the order of the size of the nucleus. The strong nuclear force is an attractive force at the limit of its range, but becomes repulsive at very short ranges.

Glom
2003-Dec-06, 09:46 PM
Quite true, although the electromagnetic interaction and the weak interaction have been unified into the electroweak interaction. But, for many purposes, they are kept seperate as it is simpler, as is the case with electrostatic and magnetic.

Kaptain K
2003-Dec-06, 10:11 PM
Quite true, although the electromagnetic interaction and the weak interaction have been unified into the electroweak interaction. But, for many purposes, they are kept seperate as it is simpler, as is the case with electrostatic and magnetic.
In the current state of the universe, EM and WN are separate forces with different rules. Things were different in the early stages. The "electroweak" unification applies only at energy levels orders of magnitude higher than currently exist. During the very early stages of the big bang, there were only three forces (gravity, electroweak and strong). There are signs that even before that, there were only two, gravity and electronuclear. Perhaps, when we finally develop a quantum gravity theory, we will find that there was once only one force and we will truly have a TOE (theory of everything).

Glom
2003-Dec-06, 11:25 PM
I thought exp(pi×i)+1=0 was the theory of everything.

Kaptain K
2003-Dec-06, 11:31 PM
I thought exp(pi×i)+1=0 was the theory of everything.
Nope! Can't be, because the answer must be 42. :o

Glom
2003-Dec-06, 11:33 PM
Okay then.

exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) -exp(pi×i) = 42

That's the theory of everything!

ZaphodBeeblebrox
2003-Dec-07, 11:06 AM
That's the theory of everything!

Yeah, but what's the question?

And

Can The Answer and The Question, ever both be known, in the Same Universe?

Oops
2003-Dec-07, 06:53 PM
Glom, I'm looking for the quantum mechanical explanation of how a neutron star forms.

Can I get a more detailed explanation of the strong and weak nuclear forces? I'm especially confused about the weak nuclear force.

Kaptain K
2003-Dec-08, 07:49 AM
That's the theory of everything!

Yeah, but what's the question?

What do you get when you multiply 6 by 9?


And

Can The Answer and The Question, ever both be known, in the Same Universe?

Obviously, No!

Glom
2003-Dec-08, 02:04 PM
What do you get when you multiply 6 by 9?

54? How did that get into the picture?

ZaphodBeeblebrox
2003-Dec-08, 03:55 PM
What do you get when you multiply 6 by 9?

54? How did that get into the picture?

Towards the end of The Restaurant at The End of The Universe, Douglas Adams has his characters attempt to derive the Ultimate Question of Life, the Universe, and Everything.

Unfortunately, Arthur wasn't actually even really supposed to be on The Earth, so he has a flawed copy.

It should probably be, "What do you get when you multiply six by seven?"

harlequin
2003-Dec-10, 12:14 AM
Question for FAQ:

Why was the Big Bang not a black hole?

Oops
2003-Dec-10, 02:07 AM
Question for FAQ:

Why was the Big Bang not a black hole? This is where my Planck Particle question comes from. :)

dgavin
2003-Dec-11, 04:53 AM
I've always wondered exactly what the matter collapses into in a black hole. Is it possible that a black hole might not be a singulaity but just super dense matter existing as quarks? For lack of better term a quark star.

This leads to another question, if enough supermassive black holes merged, might there be a quark degeneracy threshhold where once this is past, the quarks degenerate into thier smallest particle, gravitons perhaps forming a graviton star that is so intense it actually starts pulling space time itself into the star. A true singularity.

And as even more and more matter is collected, it eventylly reaches another point of degeneracy and finally collapses into pure energy.

Leading to another question, if that is the case, would not this enegery thats no longer constrained by gravity, suddenly expand in a rather startling spectaular massive big bang?

Much like how our universe started perhaps?

Just wondering...

§rv
2003-Dec-23, 11:38 PM
dgavin said:
This leads to another question, if enough supermassive black holes merged, might there be a quark degeneracy threshhold where once this is past, the quarks degenerate into thier smallest particle, gravitons perhaps forming a graviton star that is so intense it actually starts pulling space time itself into the star. A true singularity.


I was going to ask how do singularities form but I see it has been answered already. But I still wonder:

Can singularities form outside of black holes? If so how?

granolaeater
2004-Jan-05, 05:57 PM
Glom, I'm looking for the quantum mechanical explanation of how a neutron star forms.

Can I get a more detailed explanation of the strong and weak nuclear forces? I'm especially confused about the weak nuclear force.

Ok, let's try:
For a basic understanding You can handle the strong and weak forces just as normal forces like you understand the electromagnetic force. Particles with certain properties are subject to the accordant forces. If a particle holds electric charge it is subject to electromagnetic forces, if it holds 'strong charge' it is subject to strong forces, if it holds 'weak charge' it is subject to weak forces. This is a little bit oversimplified but it will suffice here.
Now quarks are holding electric, strong and weak charges and are subject to all three forces. The nucleons are composed of quarks and and thus subject to the same forces (in the neutrons the electric forces cancel out each other internally). Leptons (like electrons and neutrinos) are only holding weak and somtimes electric charges but never strong charges. This makes them 'see' the electromagnetic and the weak forces but not the strong.

If you want to know if an ensemble of nucleons and leptons(to simplify it even further: electrons) is stable you need to know how much energy the particles are holding in the forcefields of the three forces. To compute this you need quantum mechanics. Then you add these energies together and get the total energy of your ensemble. If there is another possible alternative ensemble with less total energy your ensemble will decay into the lower energy ensemble, releasing the energy.

If you count only the three mentioned forces any ball of only neutrons (neutron star) would be of much higher energy then a corresponding ball of neutrons, protons and electrons (white dwarf star). Thus a neutron star would decay into a white dwarf (on the level of atomic nuclei this is known as beta-decay) and thus no neutron star would exist. Stars would only collapse into white dwarfs.

But a ball of neutrons, protons and electrons (white dwarf star) would be much bigger in diameter then a ball only of neutrons (neutron star). (Again this has quantum mechanical reasons, the additional electrons in the white dwarf are needing much more space then neutrons) This is where gravity comes into play. More diameter means that many of the nucleons are far more outside from the center thus beeing on a much higher gravity potential - they have much higher gravitational energy.

For low masses gravity is much weaker then the other three forces and the contribution of gravitational energy to the total energy is negligible. But if you come to higher masses the fraction of gravitational energy will rise. When the mass is high enough that the fraction of gravitational energy exceeds the other fractions the neutron star will have less total energy than the corresponding white dwarf and the dwarf will collapse.

To say it short: A star will only collapse into a neutron star when its mass is high enough that the collapse will release enough gravitational energy to convert the protons of the star into neutrons (and the electrons into neutrinos).

Spaceman Spiff
2004-Jan-17, 05:32 AM
To say it short: A star will only collapse into a neutron star when its mass is high enough that the collapse will release enough gravitational energy to convert the protons of the star into neutrons (and the electrons into neutrinos).

In massive stars, two processes harken the doom of the central iron core. First, any fusion involving iron removes energy from the environment. This causes the pressure to drop, and gravity squeezes down on the core. If the pressure and gravity were to fall too far out of equilibruim, the core would begin to collapse (literally fall into itself) --- searching for a new equilibrium at higher pressure, density, and temperature if it can find one. Second, as the temperature rockets past 5 billion K, the process known as photodisintegration takes off like gangbusters. At these temperatures, there are plenty of gamma rays energetic enough to knock iron nuclei apart into lots of helium nuclei (and even some of these into simple hydrogen). A third process can happen in really a massive stars: electron/positron pair production, whereby the local thermal energy density of the star's core is sufficient to pull pairs of particles out of the vacuum. All three of these processes are endothermic (photodisintegration is like fusion run backwards), and the poor iron core has a twin-engined refrigerator turned on. :(

But when I say refrigerator, I mean a process that removes energy from the environment. The core of the star is bound by gravity and so must shrink in response --- and this process increases the temperature! This is a property of any bound system (like a satellite orbiting earth). Remove energy from it, and its new equilibrium configuration will have a higher kinetic energy because the matter sits lower in the potential well.

The hotter and denser the core gets, the more rapid photodisintegration becomes, reducing pressure still further relative to what is necessary to offset gravity, and gravity's stranglehold becomes ever stronger --- the process begins to run away, like the beginnings of an avalanche. :o

Electron degeneracy pressure (that which supports white dwarf stars) steps in to say hello for a bit, but is soon shown the door....because a process known as neutronization kicks in at about this point. Also, the layer above the iron core is rapidly converting silicon into iron, thereby increasing the mass of the iron core, exacerbating the above problems, even to the point where the degenerate core mass exceeds the Chandrasekhar mass for electron degenerate configurations. Regardless, at sufficiently high densities (for a given temperature), this process known as neutronization sets in, and occurs as follows:

proton + electron --> neutron + neutrino.

This can happen with lonely protons or with protons inside of heavier nuclei (such as helium or even iron). This in fact is the last straw that dooms the central core to collapse, as the last major player generating significant pressure in the core (electrons via mainly electron degeneracy pressure) are removed. Rapid collapse of the inner core ensues. This is a bad day in the life of a star. :( :(

So you probably have a big ball of neutrons before the core becomes dense (small) enough to become neutron degenerate (aka a neutron star), although I am splitting hairs because all of this happens on the time scale of roughly 1 second.

Kaptain K
2004-Jan-17, 11:30 AM
And, if the star is massive enough, even neutron degeneracy is not enough and the collapse continues to singularity. :o

Daro
2004-Jan-17, 07:40 PM
I remember seeing a documentry on Black holes ages ago and remember something about there being 4 massive black holes at the center of the galaxy. Am I right in saying that this is what makes the galaxy spin and keep its shape?

Is there any evidence of the existence of white holes?

what happens when black holes collide? Are they sucked in to each other. Perhaps they are reppelled like magnets.

How far away is the nearest black hole?

are black holes like a sphere, oval ball (Australian Foot Ball ball) or perhaps exists in 2 dimensions.

Kaptain K
2004-Jan-17, 08:00 PM
I remember seeing a documentry on Black holes ages ago and remember something about there being 4 massive black holes at the center of the galaxy.

Nope, only one.

Am I right in saying that this is what makes the galaxy spin and keep its shape?
No. The galaxy spins due to residual angular momentum from the material it formed from.


Is there any evidence of the existence of white holes?
No.


what happens when black holes collide? Are they sucked in to each other. Perhaps they are reppelled like magnets.
They coalesce into a larger black hole.


How far away is the nearest black hole?
Cygnus X-1 - 2.5 Kpc (8,150 light years).


are black holes like a sphere, oval ball (Australian Foot Ball ball) or perhaps exists in 2 dimensions.
Non-rotating black holes are spherical. Rotating black holes are (to a first approximation) oblate spheroids.

granolaeater
2004-Jan-17, 08:10 PM
So you probably have a big ball of neutrons before the core becomes dense (small) enough to become neutron degenerate (aka a neutron star), although I am splitting hairs because all of this happens on the time scale of roughly 1 second.

You didn't split hairs here. You just choosed a different approach to the problem. You described the dynamics and mechanism of the reaction, while I discussed the stability of the possible endproducts.
The problem is that all the reactions you mentioned in your description are reversible. This makes it impossible to judge alone by dynamics in wich direction the reaction will go and wich product you get.
Even if a big ball of neutrons is formed intermediary, this ball would decay into protons and electrons, if the energy released by this process would be sufficient to blow up your ball of matter back into a white dwarf.
If this energy would be sufficient you can judge by discussing the stability of the endproducts. Since the reaction is reversible and fast in both directions and the system looses energy in the process (by electromagnetic and neutrino radiation) the endproduct will be the product with less energy (independent of the exact mechanism).
But you need the dynamics to know the speed of the reaction.



And, if the star is massive enough, even neutron degeneracy is not enough and the collapse continues to singularity
To understand under wich cicumstances this happens is much more complicated. Here You need the dynamics.
First this reaction is irreversible. Normal matter can collapse into a black hole but black holes can not recollapse into normal matter.
On the first glance this means all matter should collapse into a black hole earlier or later.
So why doesn't our sun collapses into a black hole? (or even earth or a bowling ball?) Here the dynamics comes in. To compress matter under its schwartzschild radius you have to overcome the extremely high repulsive potential of the nuclear forces at short distances. Even the core of our sun is by far to cold to achieve this. At these temperatures the reaction would need billions of more time then the age of the universe. (The hawking radiation makes the problem even far worse. An initial 'seed black hole' would have to be big enough to radiate away slowlier then it sucks in the surrounding matter.)
This means normal matter is matastable against collapsing into a black hole. Only in the collapsing core of the biggest stars you get temperatures high enough to create a black hole in a reasonable time.

granolaeater
2004-Jan-17, 08:49 PM
Am I right in saying that this is what makes the galaxy spin and keep its shape?
No. The galaxy spins due to residual angular momentum from the material it formed from.
The galaxy is kept in shape by its entire matter. The galaxys entire matter is more then 100 billion times the matter of the sun. The central black hole has only a few 10 millons the mass of the sun. This is less then one per thousand of the galaxys mass.



are black holes like a sphere, oval ball (Australian Foot Ball ball) or perhaps exists in 2 dimensions.
Non-rotating black holes are spherical. Rotating black holes are (to a first approximation) oblate spheroids.
Since all stars are rotating all black holes that are created by the collapse of the stars will rotate too. Due to the conservation of rotational momentum they will rotatate indeed extremely fast. On the other hand since black holes have no surface features (there is indeed no surface at all) you will see no rotation but only the distortions of shape created by the rotational momentum.

granolaeater
2004-Jan-17, 10:37 PM
I've always wondered exactly what the matter collapses into in a black hole. Is it possible that a black hole might not be a singulaity but just super dense matter existing as quarks? For lack of better term a quark star.

This leads to another question, if enough supermassive black holes merged, might there be a quark degeneracy threshhold where once this is past, the quarks degenerate into thier smallest particle, gravitons perhaps forming a graviton star that is so intense it actually starts pulling space time itself into the star. A true singularity.

There is indeed a theory that there is a next degeneracy threshold beyond neutron matter called quark matter. But such a hypothetical quark star would be more like a superdense neutron star then a black hole. It would have a surface just like a neutron star. This means that infalling matter would create X-ray Bremsstrahlung. In Black holes there is no Bremsstrahlung because there is no surface. In black holes spacetime is so much distorted that matter looses all its properties expect mass, momentum and rotational momentum. This makes it senseless to speak of a composition of black hole matter.
The problem is that no one knows exactly wich density such a quark star would have (We do not now enough about quark matter to calculate this). But it is supposable that the theoretical radius of a quark star would be smaller than its schwartzschild radius. This would mean that a star would collapse into a black hole before it would create a quark star and thus no quark stars would exist. (Even when the theretical radius of a quark star would be high enough for a quark star to exist the dynamics of the collaps could it make unlikely to stop the collapse at the quark star level.)


And as even more and more matter is collected, it eventylly reaches another point of degeneracy and finally collapses into pure energy.

Excuse me, but 'pure energy' is only a concept of bad science fiction (and of new age esoterics), not of real world science. In physics 'energy' is not an object by itself but a property of an object, much like 'temperature', 'momentum' or 'speed'.
This makes the term 'pure energy' as silly as 'pure temperarure', 'pure speed' or 'pure momentum'.

By the way, since black hole matter has no inner structure like stated above, it is the last possible step of collapse.
Maybe having no inner structure is what you mean by the term 'pure energy'?


Leading to another question, if that is the case, would not this enegery thats no longer constrained by gravity, suddenly expand in a rather startling spectaular massive big bang?

Much like how our universe started perhaps?

Just wondering...

This is impossible because energy is constrained by gravity the same way like mass is. Mass and energy are equivalent. This is described by the famous formula e = mc^2.
Even if you would destroy all the matter of an object and add the equivalent energy to it, its mass would remain the same.

Spaceman Spiff
2004-Jan-22, 02:58 PM
So you probably have a big ball of neutrons before the core becomes dense (small) enough to become neutron degenerate (aka a neutron star), although I am splitting hairs because all of this happens on the time scale of roughly 1 second.

You didn't split hairs here. You just choosed a different approach to the problem. You described the dynamics and mechanism of the reaction, while I discussed the stability of the possible endproducts.
The problem is that all the reactions you mentioned in your description are reversible. This makes it impossible to judge alone by dynamics in wich direction the reaction will go and wich product you get.
Even if a big ball of neutrons is formed intermediary, this ball would decay into protons and electrons, if the energy released by this process would be sufficient to blow up your ball of matter back into a white dwarf.
If this energy would be sufficient you can judge by discussing the stability of the endproducts. Since the reaction is reversible and fast in both directions and the system looses energy in the process (by electromagnetic and neutrino radiation) the endproduct will be the product with less energy (independent of the exact mechanism).
But you need the dynamics to know the speed of the reaction.


Thanks for that further clarification of the situation. I agree. Free neutrons decay with a time constant of about a dozen minutes. And while I hadn't considered it before, an energy density equivalent to that present in the environment at nuclear densities are required to keep that from happening. But let me offer a comment to your comment about the reactions being reversible. The reactions, though reversible, do not necessarily go at the same rate in both directions (statistical equilibrium). A "leakage" favoring one direction over the other is often (usually) the case.

nokton
2004-Jan-25, 05:22 PM
Hi Spaceman,grasp your concept,but not agree with your
conclusions.You grasp present learning as the epitomy of
understanding,'tis not.What is,is the intelect you have in
addressing the problem is all

Spaceman Spiff
2004-Jan-27, 02:59 PM
Hi Spaceman,grasp your concept,but not agree with your
conclusions.You grasp present learning as the epitomy of
understanding,'tis not.What is,is the intelect you have in
addressing the problem is all

My post has nothing to do with anybody's intellect or opinion or philosophy. All of the processes I discussed are those that can be measured in a laboratory, predicted by self-consistent physical theory, and often both. Given the physical conditions, physics predicts matter and energy behave in certain ways. My post was simply a partial and qualitative explanation for the series of physical events that lead up to the collapse of a massive star's iron core. I never stated that we have a complete understanding of what happens; I merely outlined a scenario that describes our current understanding of such.

nokton
2004-Jan-27, 08:44 PM
Spaceman wrote,'free neutrons decay with a time constant.'Would
Spaceman please describe time within the constant described.
A muon has a life of two millionths of a second,a few yards into
our atmosphere it is changed,to us,yet it passes through our atmosphere
unchanged,because time to it,as it is to us,is relative.The muon passes
through us,and in some cases,causes cancer by doing so.In our time frame,such things are not consistant,thus we are blind

Spaceman Spiff
2004-Jan-28, 08:53 PM
Spaceman wrote,'free neutrons decay with a time constant.'Would
Spaceman please describe time within the constant described.
A muon has a life of two millionths of a second,a few yards into
our atmosphere it is changed,to us,yet it passes through our atmosphere
unchanged,because time to it,as it is to us,is relative.The muon passes
through us,and in some cases,causes cancer by doing so.In our time frame,such things are not consistant,thus we are blind

Taken on whole, you are mistaken.

Give a physicist the kinetic energies of the cosmic rays (or energies of the gamma rays) whose collision with matter in our atmosphere initiates the cascading shower of muons (and other particles) and he/she can tell you the average rate of muons striking per unit area of ground per second. In fact we can also compute such after penetration of so many feet of ocean or earth. We know how to transform the mean life time of a muon in its restframe to our frame of reference. We can compute the mean flux of such particles striking the average human being, and so estimate their effect on our health (a much more difficult problem). I don't mean to imply that we understand all, but we are not blind. There is a universe of difference between knowing nothing and not knowing everything.

In regards to the neutron. The dozen minute mean life time of a free neutron is measured in a frame of reference wherein the neutron is not moving relativistically or sitting in a deep gravitational well relative to us (the measurer). Or, if you will, it is the mean life time of a neutron in its own frame. Neutrons whizzing around an accelerator at speeds appreciable fractions of c will indeed "last longer" as measured by our clocks. However, the neutrons found in most astrophysical environments do not have relativistic kinetic energies. Even the gravitational redshift at the surface of a neutron star is just ~0.1.

§rv
2004-Jan-29, 04:32 AM
:o .........I must say this is all rather.... #-o enlightening??? I am thoroughly confused here but I guess your explanations didn't cater to those of lesser intelligence... :o

Kaptain K
2004-Jan-29, 11:06 AM
Minor nit pick.

Neutrons whizzing around an accelerator at speeds appreciable fractions of c will indeed "last longer" as measured by our clocks.
Neutrons do not whiz around an accelerator. Since they are neutral, any neutrons created in an accelerator will fly out in a straight line (actually a space-time geodesic).

Kaptain K
2004-Jan-29, 11:15 AM
... your explanations didn't cater to those of lesser intelligence...
It is not a matter of intelligence. It is a matter of education. I am sure that Spaceman Spiff was not trying to either confuse you or go over your head. Hang in there. :wink:

Spaceman Spiff
2004-Jan-29, 02:54 PM
Minor nit pick.

Neutrons whizzing around an accelerator at speeds appreciable fractions of c will indeed "last longer" as measured by our clocks.
Neutrons do not whiz around an accelerator. Since they are neutral, any neutrons created in an accelerator will fly out in a straight line (actually a space-time geodesic).

Yes, I should have chosen my words more carefully. Physicists who do neutron collision experiments have this "extra" difficulty. I am not one of them, but I do know that there are facilities that create linear neutron beams (but I don't know the details behind that). These beams are even used in killing cancer cells. Of course, those neutrons still inside of nuclei can be accelerated in the usual way...and there are unstable nuclei and various nuclear reactions that spit out free neutrons. But for the most part this is out of my league.

Spaceman Spiff
2004-Jan-29, 03:08 PM
... your explanations didn't cater to those of lesser intelligence...
It is not a matter of intelligence. It is a matter of education. I am sure that Spaceman Spiff was not trying to either confuse you or go over your head. Hang in there. :wink:

Thanks Kaptain K, that is exactly correct. This is not about intelligence. I am not trying to confuse anyone. I do try to explain things so that most readers, who've had some science background, can understand (otherwise I wouldn't bother posting anything). However, I imagine that I do not always succeed, and for that I apologize. There are people who post here that know a heck of a lot more than I do about some things, and I contribute when I think I can help.

Just to let you know where I am coming from...I am a professor of astronomy by profession. I teach astronomy, some astrophysics, and do research in the spectroscopy of quasars.

nokton
2004-Jan-31, 06:00 PM
With respect,I mean that,would question Kaptain Ks assertion that
education is more important than intelligence.
Used to live next door to a much respected brain surgeon,a great man,
but wiring a three point mains plug,was totally beyond him.
I come on this site to explore ideas that are against the mainstream.
I feel that any new 'ideas' that are in conflict with current thinking and
education,encourage a response our host was trying to avoid.Hence
this site here.All I ask,is an open mind,mine is,I have much to learn.
Look to this site to learn more,and hopefully find friends who I can
discuss concepts with,without the trappings of the rewards of'education'

Kaptain K
2004-Feb-01, 04:05 AM
Used to live next door to a much respected brain surgeon, a great man, but wiring a three point mains plug,was totally beyond him.
Education in one field does not confer knowledge in another. I do not assume that a brain surgeon would be competent to wire my house nor an astrophysicist to do the plumbing although it would be possible for either to have enough general knowledge of the fields to discuss the subjects. By "education", I do not necessarily mean a "formal education". The information is out there (in books and online) for a layman to get enough of the basics to discuss the fields inteligently.

PS Spaces after periods and commas make posts much easier to read.

nokton
2004-Feb-01, 09:18 PM
Thanx Captain K,you both make and explain my point here.
I read in New Scientist,Nature,over years,the contradictions
and alternative ideas proposed by peers,to the 'current truth,'
What am I to understand by this,that teaching is flawed?
What is teaching based on? A proposed truth et al?That is not to
be questioned,just accepted?No Captain K,I question everything
until I understand it.I regard 'education'as a short cut to understanding
that does'nt work,except with with a good memory and diploma....

FrankFSmokey
2004-Feb-05, 04:51 AM
Maybe you could explain how a Black Hole is shaped, I mean, Its a point, But where does all the matter go? You can't create or destroy matter.

Kaptain K
2004-Feb-05, 10:46 AM
Maybe you could explain how a Black Hole is shaped, I mean, Its a point, But where does all the matter go?
It doesn't go anywhere, it's all there in a point of zero dimensions and infinite density.


You can't create or destroy matter.
Sure you can. E = mc^2.

nokton
2004-Feb-05, 08:02 PM
Hi Smokey,you raise an interesting point.I don't think black holes
go anywhere in our perception of time.The gravity well is so intense
as to slow time down to almost zero.The mistake is,to evaluate what
we see in our time frame,as true reality.

JohnOwens
2004-Feb-14, 02:39 AM
There is indeed a theory that there is a next degeneracy threshold beyond neutron matter called quark matter.... In black holes spacetime is so much distorted that matter looses all its properties expect mass, momentum and rotational momentum. This makes it senseless to speak of a composition of black hole matter.

*cough* charge *cough*

Russ
2004-Feb-18, 03:13 PM
Hey TBA, I don't mean to put undue pressure on you,but, I'd like a status update on the FAQ page you are intending to create. I would like, very much, to know the answers to all of these questions. If you have posted this page please post the URL. If not HURRY UP AND GET ON IT! :D

pelzo63
2004-Feb-23, 08:41 AM
First post here, and it's a question, of course. ;-)

I keep reading everywhere that to an observer outside the event horizon, an object falling in to a black hole would appear frozen at the event horizon(forever? so long it might as well be?). so the question is, if this is true, then why are black holes....black? should a supermassive black hole(which presumably swallowed many stars) not be surrounded by the "ghost" light from all of those swallowed stars at it's event horizon? or at the very least, having the "ghost" light from the last star to enter it lingering there, until a new star gets swallowed causing the EH to expand again?

ok, so maybe it wasn't A question. :-)

...Chris

Glom
2004-Feb-23, 01:46 PM
I keep reading everywhere that to an observer outside the event horizon, an object falling in to a black hole would appear frozen at the event horizon(forever? so long it might as well be?). so the question is, if this is true, then why are black holes....black? should a supermassive black hole(which presumably swallowed many stars) not be surrounded by the "ghost" light from all of those swallowed stars at it's event horizon? or at the very least, having the "ghost" light from the last star to enter it lingering there, until a new star gets swallowed causing the EH to expand again?

Welcome. Good question. I would guess that the light from the star has been gravitationally redshifted beyond the visible spectrum.

Yumblie
2004-Feb-25, 03:42 AM
Also, most matter falls in from the accretion disc, so while there may be some frozen images of light, there's so much other matter spinning around it that you wouldn't be able to see it.

nokton
2004-Feb-26, 07:34 PM
My point indeed.Don't have crystal ball,but do my best to get my
head around this concept.To the one on the event horizon,to us,
not moving,yet to him/her,moving,how does their concept of the passage
of time,see us?Just a blink of an eye,in his/her time frame?
I look at the night sky,the stars therein give me so much joy.
But what am I looking at?An image that is not reality.I look at stars
that died a million years ago,but the light they shed still shines here,
for me.I look at a black space in the night sky,and cannot see the birth
of new stars there,because the light from their birth has not reached me
yet.Don't envy future of star chart creators,if we ever reach that need.

Kaptain K
2004-Feb-26, 08:02 PM
Your posts would be much more readable if you would follow the convention of putting a space after each comma and period.

nokton
2004-Feb-27, 08:06 PM
Commers,spaces,you have written before Mon Capitan.
Relate to the question posed if you will.We exist in a certain
time frame,our view of the universe is determined by it.
Was posing a viewpoint relative to someone with a different
time frame,such as one on the event horizon of a black hole.
Just exploring ideas,your input regarding the finer points of
literacy,betray your lack of understanding or confluence with
the question posed.

Kaptain K
2004-Feb-27, 09:25 PM
](*,) #-o

nokton
2004-Feb-28, 05:55 PM
Hi Kaptain,
Am in here on this forum in persuit of learning,and understanding,to exchange ideas and concepts,with people of
like mind.To use this forum with intelligence,and respect for
anothers opinion.You betray both concepts,perhaps you should
share your thoughts with someone who can help you.........

Kaptain K
2004-Feb-28, 07:30 PM
All I suggested was that in the interest of clear communication, you use the accepted conventions of punctuation. It is difficult to communicate clearly if you spend more time deciphering posts that are difficult to read than in actually answering questions. If that is too much to ask, then fine. I shall ignore your hard to read posts from now on.

nokton
2004-Feb-29, 07:54 PM
Kaptain,
Thanx much Kaptain for your response,much appreciate,
Would like dialogue with you,if that is your wish,my hand is open
to shake yours,in the spirit of friendship and understanding.
Tell me more of yourself,your ideas,and concepts.

kikisonic
2004-Feb-29, 08:37 PM
The black hole no hair theorem states that charge, angular velocity, and mass are the only properties a black hole can have. My question is why?
Shouldn’t it have a color charge or a hypercharge? And how ca a black hole have charge, isn’t the force carrier of electricity a photon which is what light is made of, and light can escape a black hole, and electrons cant either so how is there charge. In addition, what is rational of the black hole no hair theorem?

nokton
2004-Mar-01, 06:31 PM
Hi kikisonic,read your post with interest,the points you raise,and
the questions you pose,interest me too.The thing I am trying to
evaluate at this time,is when two black holes collide,Alberts equations
regarding gravity,and it's effect regarding time in the above scenario.
Would we,in our time frame ever see it happening?
Keep posting kiki,the object of this site really is against current
thinking,and exploring new ideas that are not constrained by rote
learning.The creator of this site is a light in the darkness that would
betray the truth.Thats how I see it.

kikisonic
2004-Mar-01, 11:40 PM
i dont think that 2 black holes would ever collide. they would distort time to the point that they never collide. i think they'd radiate themselves out of existence or the universe would end before it happend.

JohnOwens
2004-Mar-02, 09:25 AM
Who'd'a thunk it?
http://researchnews.osu.edu/archive/fuzzball.htm
Assuming it's correct, of course.

nokton
2004-Mar-02, 06:39 PM
Kikisonic assumes two black holes would never meet,and if they ever did
the universe would collapse.Galaxies collide,the black holes within them
merge.Kikisonic,have on my coffee table March issue of 'Astronomy'.
With respect,suggest you read the main article within,concerning the
current theories regarding the creation of massive black holes.
Please do not regard my response as a negative post to your post,
rather an attempt to express my feelings,that the contributers to this
site,are the ones who do not accept dogma at face value,rather
challenge it,with new ideas,and theories,even tho' tis' against
'the mainstream'.Feel that is what our host created this site for.
Learning is one thing,enlightenment another.

kikisonic
2004-Mar-03, 02:44 AM
I'm sorry you misinterpreted my post :( , I meant that space time would be so messed up that they would never actually occur, because of relativity and the like. So the black holes of the 2 galaxies would get very close, but would never actually touch because time was slowed down, and because of that the universe would end or the black hole would radiate themselves out of existence before they actually touched. Please refer to discoverer science almanac 2004. I did not mean that they would never interact or that the universe would end. And feel free to correct me, rather be wrong than ignorant.

nokton
2004-Mar-03, 07:11 PM
Hi kikisonic,forgive my misunderstanding of your penultimate post.
You raise points in your last that I am presently trying to find a concept
to explain.We accept that a black hole has two attributes,the singularity
at it's core,and the theory of the event horizon.One aspect of the latter
is that anything on the event horizon,to us,would appear stationary,
because the intense gravity field slows time down to almost zero.
So take your point about a collision between two black holes.I agree
with you within the frame of reference.It is said that the laws of physics
break down at the event horizon,I prefer to think that they not complete.
This weeks 'New Scientist' contains an article about a flaw in Newtons
'clockwork' universe.I have a gut feeling kikisonic,that we are missing
something here,because we are so convinced about 2 and 2 making 4

kikisonic
2004-Mar-04, 02:24 AM
What’s easily forgotten is the fact that most black holes are Kerr-Newman black hole (with some Kerr black holes), while when thinking of black holes most people think of Schwarzschild black holes (which I think are almost impossible to occur in nature). The fact is that they have radically different properties. So when dealing with collisions of black holes, remember to think of everything. For example, maybe time would slow to the point where so much time would pass that hawking radiation would be enough to push them away from each other. Also, an interesting question is what happens when they get close enough so there event horizons overlap each other (it doesn’t seem like a problem at first but think about it for a while). Everyone is bent on 2+2 always equaling 4, but when 2+2 equals 5, there’s a 1 hiding somewhere.

kikisonic
2004-Mar-04, 03:25 AM
hey try this site for black hole collisions
[ url=http://images.google.com/.... ]LINK[ /url ]

JohnOwens
2004-Mar-04, 07:02 AM
hey try this site for black hole collisions
(enormous three-page-wide URL)

Could you shrink that URL a bit, maybe using [ url=http://images.google.com/.... ]LINK[ /url ] or something like that? It's distorting all the rest of the page there.

Edit: Erm, not quite what I meant. Put the rest of your URL in where I have ellipses ("...."), but it would just be me making the page wide then if I typed the whole thing out! And take out the spaces between the brackets and "url=...." and "/url". If it helps to explain the whole shebang to you, click on that little "BBCode is ON" link to the left while you're editing, underneath the smilies.

nokton
2004-Mar-04, 07:22 PM
Kikisonic wrote'what is easily forgotten is the fact' and invokes
Kerr -Newman. the whole point of this topic is that there are no
'facts', that a math expression of the dynamics to explain a black
hole,do not exist.
Why do so many contributors to this site express the opinions of
contemporaries to make and justify their point?Have they no opinion,
or concept,that they can attribute to themselves?
Tell me if you will,if I am wrong here,this site,and our host who
created it,is about people who think for themselves,challenge current
'theory',and propose alternative thinking and concepts about what to
the establishment is dogma.

kikisonic
2004-Mar-04, 10:22 PM
alright its not a fact, it was a expression

nokton
2004-Mar-05, 09:16 PM
Hi Kiki,Take your point.Prime thing is,are we as one in our
discourse of our quest in grasping the concept of a black hole?
Yes Kiki,2+2 make 4,was just trying to explain that physics as we
understand,break down at the event horizon.Math is one thing,
and a very powerful tool,but comprehension,understanding,concept,
is not related to math,but to the emotion of the individual

Russ
2004-Mar-10, 09:59 PM
Hey TBA, I don't mean to put undue pressure on you,but, I'd like a status update on the FAQ page you are intending to create. I would like, very much, to know the answers to all of these questions. If you have posted this page please post the URL. If not HURRY UP AND GET ON IT! :D
As I said above, I don't mean to put undue pressure on you BUT.......

RSVP :D :/

nokton
2004-Mar-12, 06:09 PM
Russ,the creator of this site is no idiot,and deserves respect
for creating a site wherein we can communicate our ideas and
concepts,that will further the development of science and understanding,
This site is about challenge to conventional thinking,and I respect our
hosts remit.More,I agree with it.

Russ
2004-Mar-15, 07:10 PM
Russ,the creator of this site is no idiot,and deserves respect
for creating a site wherein we can communicate our ideas and
concepts,that will further the development of science and understanding,
This site is about challenge to conventional thinking,and I respect our
hosts remit.More,I agree with it.
Dear nokton:

1) Please refer to my signature.

2) I have been a regular on this site since 1996 and am VERY familiar with Phil and his motives and intent. The LAST thing I would consider Phil is an idiot. Unlike someone who shall remain nameless.

3) While I try not to bug him now, as he is obviously very busy, Phil and I have exchanged many amiable emails and postings on this medium. This is just one more.

4) You will note from my profile on the sidebar that I have been registered with this BB since it was installed (I'm serial #64) but I have relatively few postings. This is because I attempt to avoid just blathering for the sake of seeing my own postings.

5) Thank you for your time and attention in these matters. :) :D :lol:

nokton
2004-Mar-16, 09:07 PM
Russ,
Am unimpressed with your response to my expression
of appreciation about our hosts ideals,and his commitment to what I regard as a very laudable cause,the persuit of truth in the face of
current dogma.
I don't 'know' the host of this site,and if i did,would never make an
issue out of it.But I do grasp the concept of his endeavour.
That is to provide a forum wherein ideas and concepts that are not
accepted in 'the mainstream',are evaluated by those of like mind,
to further understanding of the truth,and challenging current perception
of what we are told,is true.

Russ
2004-Mar-16, 09:40 PM
Russ,
Am unimpressed with your response to my expression
of appreciation about our hosts ideals,and his commitment to what I regard as a very laudable cause,the persuit of truth in the face of
current dogma.
I don't 'know' the host of this site,and if i did,would never make an
issue out of it.But I do grasp the concept of his endeavour.
That is to provide a forum wherein ideas and concepts that are not
accepted in 'the mainstream',are evaluated by those of like mind,
to further understanding of the truth,and challenging current perception
of what we are told,is true.

:o :o :roll: :roll: :roll: :roll: :roll: :roll:

:lol:

nokton
2004-Mar-18, 07:29 PM
Thanx Russ,feel we are both of the same mind.
I will take your advice,and 'lighten up'.
Was never one to bear a grudge,or have a closed mind to
anothers opinion.
On a more serious note,would value your opinion on the
time frame of black holes relative to the gravity constant
that is relative to their size.Seems to me,in simple terms,that
the bigger the'hole',the greater the gravity well,the slower the time.
Appreciate your contact

Brady Yoon
2004-Mar-20, 03:47 AM
Nokton, why do you have to make your posts so hard to read? :-?

Russ
2004-Mar-20, 09:04 PM
Thanx Russ,feel we are both of the same mind.
I will take your advice,and 'lighten up'.
Was never one to bear a grudge,or have a closed mind to
anothers opinion.
On a more serious note,would value your opinion on the
time frame of black holes relative to the gravity constant
that is relative to their size.Seems to me,in simple terms,that
the bigger the'hole',the greater the gravity well,the slower the time.
Appreciate your contact
If I had one darn clue what you are talking about I wouldn't be bugging TBA to post his FAQ page so I could read the answers. :lol: :roll:

nokton
2004-Mar-21, 04:27 PM
Am unimpressed by recent posts about the lack of spaces after
commas and periods in my posts.How that makes it harder to read,
cannot imagine.
Kiki made an evaluation about the time frame of two black holes colliding,and would we ever be in a position to observe it.In my humble
opinion,Kiki is on the right path to understanding something unique
that may explain the fact that we have dialogue here.

Glom
2004-Mar-21, 04:35 PM
Good punctuation costs nothing, nokton.

nokton
2004-Mar-21, 07:14 PM
Sorry,have I missed the bus here.This site as I understand it,is
about challenging current theory and ideas of cosmology,and
proposing an alternative and viable point of view,within the constraints
of reason and logic.
What have we here?Semantics focussed on,not the subject,but the
expression in language of the subject,that is not accepted because
there is some fault in punctuation?My heart bleeds for humanity.
As for our host posting FAQ,would propose 'tis better to understand
the question, than find the answer'

Normandy6644
2004-Mar-21, 07:55 PM
It's just being polite, that's all. I don't really care how you post, it makes no difference. The point is if a bunch of people find your posts difficult to read and ask you nicely to add spaces so that they may read them more easily, it's just a polite request.

Glom
2004-Mar-22, 01:14 PM
Just because we discuss astronomy here, it doesn't mean we don't use proper punctuation.

nokton
2004-Mar-22, 07:40 PM
Normandy,how eloquent your reason.How well mannered your
response.I value you,and what you are about.As a Knight,my cloak
is at your feet,my sword in my hand to defend you and your honour.
Many smiles,just messing.But what can you give me in my quest for
understanding the enigma of a black hole? Thakyou anyway.
You are special.

Normandy6644
2004-Mar-23, 03:28 AM
Normandy,how eloquent your reason.How well mannered your
response.I value you,and what you are about.As a Knight,my cloak
is at your feet,my sword in my hand to defend you and your honour.
Many smiles,just messing.But what can you give me in my quest for
understanding the enigma of a black hole? Thakyou anyway.
You are special.

Thanks, my mom always said I was special too. 8) What "enigma" would you like to know about? There are plenty of people here who can either answer your questions or point you in the right direction.

nokton
2004-Mar-23, 07:44 PM
Normandy 6644, if you have nothing but the diatribe
you exhibit here to make your point, by destroying
anothers point of view, to justify and make up for your
lack of understanding, feel free. You will be judged by your
words, and your lack of understanding, which I feel is at the heart of
your post.
Hope I got the spaces correct between the commas and periods.
Smile.Am learning to accept what fork to use, and when.

countrywideoptionone
2004-Apr-01, 11:16 PM
I didn't read every post, so these may have already been asked:

- The difference between a primordial black hole and a 'regular' black hole.

- A White hole - could this be what is inside a black hole?

- Star Trek science - "Warp Speed" By traveling at nearly the speed of light, your mass increases without bound. The higher the mass the higher your gravitational effect, right? Eventually, wouldn't you turn into a singularity? Alternatively, once you were going fast enough that your mass was many times great than that of the (nearby) universe, presumably everything nearby would be sucked into your self made black hole, so you could just point your ship where you wanted to end up, slow down, and presto! You got where you wanted to be in "no" time.

Glom
2004-Apr-02, 12:22 PM
- Star Trek science - "Warp Speed" By traveling at nearly the speed of light, your mass increases without bound. The higher the mass the higher your gravitational effect, right? Eventually, wouldn't you turn into a singularity? Alternatively, once you were going fast enough that your mass was many times great than that of the (nearby) universe, presumably everything nearby would be sucked into your self made black hole, so you could just point your ship where you wanted to end up, slow down, and presto! You got where you wanted to be in "no" time.

It's the difference between gravitational mass and inertial mass. Besides, quick travel isn't a problem. If you travel fast enough, time dilation and length contraction run their course to make it so that the entire universe is within a few years reach.

nokton
2004-Apr-02, 05:23 PM
Glom poses an interesting post, based upon Newton and Albert.
Would contend that lightspeed as related to the above, is but
one aspect determined by current knowledge.
There are many references describing space as a fabric.
A fabric has dimension that we choose to describe determined
by our limited understanding.
Spacetime does not conform to present concepts of 'fabric'.
Still contend my initial contention, spacetime distorts relative to
local gravity, and relative speed of an object.
I believe, Glom, that we will, one day, understand the many
dimensions of time, that appear singular now.

countrywideoptionone
2004-Apr-03, 12:15 AM
- Star Trek science - "Warp Speed" ...

It's the difference between gravitational mass and inertial mass. Besides, quick travel isn't a problem. If you travel fast enough, time dilation and length contraction run their course to make it so that the entire universe is within a few years reach.

Okay, but wouldn't the time dilation cause time to go by more slowly for the traveler than those at the origin or destination? So even if only a few years went by for the traveler, huge amounts of time could have gone by for other. Is that correct? If yes, than that makes many travel options not quite as good as "Star Trek" (no offense).

dakini
2004-Apr-03, 01:13 AM
- Star Trek science - "Warp Speed" By traveling at nearly the speed of light, your mass increases without bound. The higher the mass the higher your gravitational effect, right? Eventually, wouldn't you turn into a singularity? Alternatively, once you were going fast enough that your mass was many times great than that of the (nearby) universe, presumably everything nearby would be sucked into your self made black hole, so you could just point your ship where you wanted to end up, slow down, and presto! You got where you wanted to be in "no" time.

actually, this was mentioned in my modern physics class last semester. the warp drive used in star trek is supposed to create a bubble around the ship (or whatever's going warp speed) and this bubble travels faster than the speed of light, but inside the bubble, mass and time are unaffected. thus the people on the ship age at the same rate instead of being time dilated to be aging very slowly or anything. it's a purely theoretical thing though. one of my friends in theorietical physics says that they're only one piece of the puzzle from figuring it out though.

nokton
2004-Apr-03, 06:31 PM
Okay,take the points and concepts posed.Lets reverse time dilation,
to an intelligent lifeform existing on the event horizon of a black hole,
our sun and planets and life here would be just a wink of an eye.
To anyone who has interest in my past posts,would contend that
gravity and spacetime are interactive.
We are all well aware of the effect of diffraction within a medium
such as water.Water does not change it's nature as a variable.
Gravity does.Would propose to anyone of interest,that gravity,
in a way,has a diffraction constant that may explain Aberts theory
of light as a curve in certain situations.

Tensor
2004-Apr-07, 07:44 PM
I didn't read every post, so these may have already been asked:

- The difference between a primordial black hole and a 'regular' black hole.


A primordial black hole is a small black whole that theoretically could have formed just after the Big Bang due to the extremely high pressures at that time. While they are theoretically possible, they have not been observed as of yet. A regular black hole is a black hole that forms from the collapse of a massive star.


- A White hole - could this be what is inside a black hole?

Not quite, GR calculations show it is possible (but extremely unlikely) that the sigularity inside a black hole could be a bridge to another part of the universe. The energy and mass discharged from the white hole would come through the bridge from the black hole. The highly unlikely part is due to the requirements (the negative energy condition, among others) to keep the bridge open between the black hole and the white hole. It is thought (the calculations aren't clear on this as of yet due to not having a quantum gravity theory) that quantum fluctuations would cause the bridge to close just after it is formed (I believe the range of time is from 10^-43 sec to 10^-95 sec).

darkdev
2004-Apr-12, 03:59 PM
Can there be a region of space that is dense enough to attract some light (i.e. light which would have been emited by it or which passes close enough), but not be a black hole? For instance, maybe a close-to-critical mass without any addition mass near by. Would you then have an almost black hole which would be detected as black hole by current instruments but not truely be what we define a black hole to be?

Ricimer
2004-Apr-12, 05:37 PM
You can have an object that attracts light, but isn't a black hole. Anything with matter will doe this.

Take a look at "gravitational lensing" when you get a chance to see examples.

I'm also sure that there are some objects that are close, say Neutron stars, that could be considered BH's.

They're small, basically non-visible since they cannot radiate much light (while really hot, they have a limited surface area), and pretty massive (up to 3.5 x the sun's mass).

However, they probably won't be classified as BH's. Why? Because the objects may not be BH"s, so, at best, they'll be black hole candidates until somethings says they are black holes, or they are neutron stars (which, in this case, they are).

Something isn't considered a BH, beyond a reasonable doubt, unless what we can see cannot be explained by anything else.

SO it may be a BH, but if it could be a neutron star (also small, dim and massive) it'll probably be called the other (but with the question left open).

Of course, if the object turns out to be...5 x the sun's mass, or something like that, well, it can't be a nuetron star anymore, so it's a BH (the only other thing that fits the bill)

The Bad Astronomer
2004-Apr-12, 09:20 PM
Just an update:

I have not been able to keep up with this thread, and I will read the whole thing... eventually. :o But remember, I never said I would answer questions here! The purpose of this thread was to see what questions everyone had.

We're still working on the proposal for all this now. I'll post an update when I get one.

Glom
2004-Apr-12, 10:30 PM
A ha. BA's lost track of this thread. Quick! Everyone swear, talk about politics and religions, insult each other, post bandwidth stealing images and advertise adult sites! :-$ :wink: :^o

darkdev
2004-Apr-14, 07:27 AM
Why do I keep seeing planular depictions of black holes?

Isn't the idea that it attracts everything from all directions? And then there are streams from each "pole" of the planes axis, which makes some sense, but how fast is that matter/energy moving to escape the black hole if light itself can not? Is the gravitational force weaker at the poles?

I bet those poles are magnetically polarized as is earth, if infact magnetism is like gravity and is not bound to space like light is. Then again, if magnetism is due to overall polarity of matter, and inside the black hole matter is broken down into primary components, I would have to say magnetism would no longer be relevant. That's a good question... are BH's magnetically polarized?

I apologize if this has already been asked, I haven't read all 224 posts on this thread. [-X

Kaptain K
2004-Apr-14, 09:42 AM
The jets are not escaping from the black hole, they are escaping from the accretion disk. Big difference!

darkdev
2004-Apr-14, 10:07 AM
The jets are not escaping from the black hole, they are escaping from the accretion disk. Big difference!

Okay, so after some googling I think I have an idea of what an accretion disc is, but isn't that all around and not at the center, as the jets always appear to be from center point of the axis? Is it implied that the disc stops at the event horizon? And so the jets are steaming from a circle matching the event horizon's diameter and at 90's to accretion, and why?

If you have a good link to an existing reference on accretion and jets, that'd be great... I am rather disappointed with my Google results today. :cry:

Ricimer
2004-Apr-14, 10:02 PM
Things can enter from all directions, but tend to get concentrated near the B.H.'s equator, in a disk 90 degrees to the spin axis (so the poles are perpendicular to the axis).

This is because:

1) Any existing disk will exhibit drag forces, and non-symettric gravitational forces, that work to pull new infalling material in line with the disk.

2) The black hole, due to its intense gravitation and rapid rotation, creates a phenomena called "frame dragging" which wraps spacetime around the BH in the direction of its rotation. This has an effect of causing all the material around the BH to spin in the same direction, and Conservation of angular momentum shapes it into a disk (like how proto-stars form planet spawning disks).

Thats my take and understanding.

darkdev
2004-Apr-14, 10:18 PM
Pretty concise, thanks! I think I even got it the first time through ;)

So what's you take on the polar jets?

[edit: omitted word "it"]

Ricimer
2004-Apr-14, 10:49 PM
Merely infalling material that gets accelerated to escape velocity (when it's outside the event horizon and the escape velocity is slower than C)

Methods:

1) Gravity alone gets it close.

2) Frame dragging provides a boost

3) Odds are, its charged by the time it gets to near the BH (afterall, the jets are of ionized gases), so the magnetic field, being rapidly rotated by the BH, help move it along

4) The magnetic field also acts to funnel the now rapidly moving charged gases towards teh magnetic poles (like an aurora, but with particles leaving instead of comming).

5) Since 1-3 all imparted more speed to the gas, its at escape velocity at this point, and gets shot up along the magnetic poles and out into space.


This is, btw, how Active Galactic Nuclei, and Quasars (same things, just bigger really) are supposed to work (in part).

Brady Yoon
2004-Apr-15, 12:18 AM
Has the BA written the FAQ yet? :oops:

Tensor
2004-Apr-15, 12:04 PM
Has the BA written the FAQ yet? :oops:

Brady, a couple of days ago, on the previous page (Page 9), the BA gave an update as to what was going on as far as the BH faq was concerned.

nokton
2004-Apr-16, 08:37 PM
Ricimers evaluation is not wrong.Gloms cheap shot at our host is.
Hawking and Penrose deduced that the sigularity of a black hole
was the termination of matter,space and time.That the opposite
must have been a bang,true to a point,and a good point it is.
My point is,as ever,we evaluate the known universe within our
current timeframe.Time is dynamic.Alberts equations show this.
We evaluate our known universe within our singular reference
to time as we know it.Our timeframe is dependent upon our speed,
and local gravity conditions.To some other entity where speed and
gravity are different,the universe is a different scenario

Brady Yoon
2004-Apr-20, 05:21 AM
I'd like to know what the gravitational limits are, say, before a human feels pain, threshold of human survival, when trees are crushed, when rocks are crushed, etc.

Brady Yoon
2004-Apr-20, 05:26 AM
Explaining what gamma-ray bursts are. :o

Glom
2004-Apr-20, 10:41 AM
Ejection hurts and that's around 15G. 20Gs would probably be fatal.

The Supreme Canuck
2004-Apr-20, 07:56 PM
Now here's a question; I know that it's far easier to pass out under negative g forces, but are negative g's fatal at a lower intensity than positive ones? (I don't know, maybe something would pop under negative g's)

Ricimer
2004-Apr-20, 08:23 PM
I'd like to know what the gravitational limits are, say, before a human feels pain, threshold of human survival, when trees are crushed, when rocks are crushed, etc.

Well, if you're in free fall, there is no limit, since you have to be pushed up against something to experience the "g force" described above. You can fall, due to gravity, at any "G" you wish.

Now, you should probably look out for tidal gravitational forces, those pull on different parts of you harder than others (thus tearing you in half!). Don't know what the limit on that is though.

darkdev
2004-Apr-20, 09:02 PM
Now here's a question; I know that it's far easier to pass out under negative g forces, but are negative g's fatal at a lower intensity than positive ones? (I don't know, maybe something would pop under negative g's)
Negative and positive G's are only due to orientation. You have less room in your head for blood, so if you direct the blood up there, you pass out very quickly... however if you divert blood, it's a different type of pass-out, and you have a lot more area to store blood in your legs. Incedentally, they have special suits that squeeze the legs of pilots to keep the blood from gathering there... But no head-squeezing helmets (to prevent that pop!)

Ricimer is probably correct in that you must attempt to overt your "G's" before they become painful, although I'm sure there's a point were your heart would not be able to pump against gravity.

However I do not agree in the summation that you can fall at any "G". Freefall is exactly 1 G, minus drag caused by air pressure underneath the object.

As for tidal forces, these, to the best of my knowledge, require large bodies... a person does not "feel" tidal forces because we do not generate enough gravity ourselves, and the tidal gradient covers a large area... So I'm not really worried about my body as much as I am the planet I live on.

JohnOwens
2004-Apr-20, 11:48 PM
However I do not agree in the summation that you can fall at any "G". Freefall is exactly 1 G, minus drag caused by air pressure underneath the object.

As for tidal forces, these, to the best of my knowledge, require large bodies... a person does not "feel" tidal forces because we do not generate enough gravity ourselves, and the tidal gradient covers a large area... So I'm not really worried about my body as much as I am the planet I live on.
Remember, though, we're talking about all this in the context of black holes. So freefall will very likely be significantly more than 1 G (assuming you define 1 G as the acceleration of gravity at Earth's surface, rather than the acceleration of gravity wherever you happen to be at the moment), and tidal forces will likely be very, very significant indeed. (I know this is all different for super-supermassive hypothetical black holes with a mass around a trillion solar masses, but I don't see any of those around here; do you? :wink: )

The Supreme Canuck
2004-Apr-21, 02:44 AM
Thanks, darkdev, makes sense.

Ricimer
2004-Apr-21, 05:52 PM
Ricimer is probably correct in that you must attempt to overt your "G's" before they become painful, although I'm sure there's a point were your heart would not be able to pump against gravity.

However I do not agree in the summation that you can fall at any "G". Freefall is exactly 1 G, minus drag caused by air pressure underneath the object.

As for tidal forces, these, to the best of my knowledge, require large bodies... a person does not "feel" tidal forces because we do not generate enough gravity ourselves, and the tidal gradient covers a large area... So I'm not really worried about my body as much as I am the planet I live on.

Umm, free fall is exactly 1 G near the surface of the earth.

A more accurate definition of "Free fall" is one falling freely due to gravity. No force other than gravity acts upon a freely falling body.

You can free fall with an acceleration of 100 x the acceleration due to gravity (thats what a g is, g isn't a force, but an acceleration) and have no ill effects. Just like you can jump from a plane and fall at 1g and not care. Until a force arises that rapidly decelerates some parts of you more than others (i.e. like the leading portion of your head hitting the dashboard before the back) do you get any ill effects.

nokton
2004-Apr-21, 06:29 PM
Dark Dev,T.S Canuck, have you lost the plot or the understanding
of the topic? The discourse here is not about the next generation of
fighter pilots, and the G forces they may experience.
As an aside, and am sure those who know will understand.
The Ruskies test and evaluate would be pilots as to their G force
tolerance, before spending much money training them.
Thought this forum was about grasping the concept of a three dimensional gravity well, and ideas and concepts to understand it.
Roger Penrose, I think, would agree, pictures and concepts in the
mind mean more than equations on a blackboard.
Tell me I am wrong in my concept that space varies in density
according to local gravity and relative speed.

darkdev
2004-Apr-21, 07:12 PM
Dark Dev,T.S Canuck, have you lost the plot or the understanding
of the topic? The discourse here is not about the next generation of
fighter pilots, and the G forces they may experience.
Actually, since you're so observant, it was

I'd like to know what the gravitational limits are, say, before a human feels pain, threshold of human survival, when trees are crushed, when rocks are crushed, etc.
And so you resond with yet another off-topic informative post...


As an aside, and am sure those who know will understand.
The Ruskies test and evaluate would be pilots as to their G force
tolerance, before spending much money training them.
So do we! But that's off-topic... (BH's)


Thought this forum was about grasping the concept of a three dimensional gravity well, and ideas and concepts to understand it.
Roger Penrose, I think, would agree, pictures and concepts in the
mind mean more than equations on a blackboard.
You are probably right, a new topic should have been spawned. But if someone has less of an understanding of gravity and poses the question, I will gladly respond if it's something I think I know... and am more than happy to find out I'm wrong or my notions aren't completely correct. I agree with the Roger Penrose quote. Shouldn't this suggest that the better one understands gravity on earth, the better their conceptual thinking process will be for pure thought experiments?


Tell me I am wrong in my concept that space varies in density according to local gravity and relative speed.
Define density as used in this instance. Mass per volume? Amount of spacetime in a given region as compared to a flat configuration (empty space)?

darkdev
2004-Apr-21, 07:34 PM
You can free fall with an acceleration of 100 x the acceleration due to gravity (thats what a g is, g isn't a force, but an acceleration) and have no ill effects.

How? If I'm in a plane that is accelerating toward earth at 986 m/s^2, I'm pretty sure I'll be pinned to the back wall, and experience 100G's of "squeeze". The only way to feel "free fall" is if the plane is accelerating at ~ 9.8 m/s^2 towards the surface, given a small correction for actual start altitude. This suggests that there is no critical speed, just a critical deceleration factor, as in 100 to 0 mph in 0.01s is likely fatal. If there is a critical deceleration, it stands to reason that there is a critical acceleration as well. Would 0 to 100mph in 0.01s present the same impact to the back as 100 to 0 presents to the front?

What is the G force equivelent at the center of the earth as opposed to at the surface?

Mathematicians... what is the distance covered from the center of the earth to the point where earths gravity becomes negligable, say .001m/s^2? What is the maximum speed you can reach given that distance with a start speed of 0?

Glom
2004-Apr-21, 07:43 PM
darkdev, we speak of freefalling. 100G acceleration in freefall to Earth isn't likely, but 100G freefall into a white dwarf is very likely and if that were the case, you wouldn't feel any adverse effects because you're falling at the same rate as your craft. We're talking acceleration due to gravity, not powered acceleration.

darkdev
2004-Apr-21, 07:45 PM
ahh. I though we were still on earth. That makes sense then.

nokton
2004-Apr-21, 07:45 PM
Hi Dark Dev. Value your imput, mean it.
I have a concept that describes space, not as a 'fabric',
but as a medium, hope that makes some sort of sense.
The point am trying to make is that space varies in density
according to local conditions, and that time is variable according
to the same local conditions, those conditions are determined by
the speed of the observer and the local gravity circumstance
determinating the objectivity of the observer.
Look forward to your comment.

Ricimer
2004-Apr-21, 07:53 PM
You can free fall with an acceleration of 100 x the acceleration due to gravity (thats what a g is, g isn't a force, but an acceleration) and have no ill effects.

How? If I'm in a plane that is accelerating toward earth at 986 m/s^2, I'm pretty sure I'll be pinned to the back wall, and experience 100G's of "squeeze". The only way to feel "free fall" is if the plane is accelerating at ~ 9.8 m/s^2 towards the surface, given a small correction for actual start altitude. This suggests that there is no critical speed, just a critical deceleration factor, as in 100 to 0 mph in 0.01s is likely fatal. If there is a critical deceleration, it stands to reason that there is a critical acceleration as well. Would 0 to 100mph in 0.01s present the same impact to the back as 100 to 0 presents to the front?

What is the G force equivelent at the center of the earth as opposed to at the surface?

Mathematicians... what is the distance covered from the center of the earth to the point where earths gravity becomes negligable, say .001m/s^2? What is the maximum speed you can reach given that distance with a start speed of 0?

You did read my post right? Where I said free fall is falling under the influence of gravity alone? Having a jet strapped to your back isn't gravity my friend.

And if the gravity is stronger than earth, no problem, if its weaker no problem. You can free-fall about the sun at acclerations greater than (or less than, depending on distance) 9.8 m/s^2.



There is no "critical" acceleration, unless it acts on different parts of you in different amounts. In a collision, going from 100 mph to 0 in 1s, the impactin part of you is stopped first, then the trailing edge stopped (by running into the front half!) thats what hurts.

Now, if the entire body is stopped, the same amount, you don't notice a thing.

Remember, damage to the human body is done by stressing it, by stretching or crushing.

Think of two balls (connected by a rod), dropped in a vacuum, under the influence of gravity alone. Do those two objects get any closer? Do they hit eachother? Do they get pulled apart? Not really, no. They both accelearate at the same amount, and so there is no stress on the rod. No damage is done.

You cannot be hurt by "free-fall" for this very reason, all parts of you are accelerated the same amount, at the same time.

You can be hurt by collision (something that opposes the free-fall) and even tidal forces (the difference in gravity between you head and toes can rip you apart if its big enough).

darkdev
2004-Apr-21, 08:22 PM
I have a concept that describes space, not as a 'fabric',
but as a medium, hope that makes some sort of sense.
The point am trying to make is that space varies in density
according to local conditions, and that time is variable according
to the same local conditions, those conditions are determined by
the speed of the observer and the local gravity circumstance
determinating the objectivity of the observer.
I think the same, that time is variable, dependant on speed and local gravity. I read an interesting paper that concluded that as your speed approaches C, the speed at which time transpires (noted by measuring the speed at which atomic processes take place) is varied. In this theory, if you reach C, an electron will stop spinning around the nucleus and actually run into it (the space between the electron and nucleus decreases with acceleration).

I also ponder that a galaxy with a different speed than ours will experience time differently, and may evolve life faster or slower than here.

But back to your question... let me take a stab at your "spacial medium"... if space is a fluid (for analogy), then space is flowing towards all mass. The more fluid [space] matter "absorbs", the more space must flow to replenish it (otherwise there is a vacuum somewhere). For a large object, like earth, we "absorb and compact" a lot of space, and so on the surface there should be more "fluid flow by volume (like CFM)" than 1000 miles from the surface. This much I get, to an extent, and agree could be viewed as density... but, if we use space as an everlasting water supply, and matter as a "sink hole" to drain the water, then the reverse is true. The water will not be more dense near the sink holes, and if anything will be less dense, since water will be accelerating. I picture an aerofoil. Where air is coerced into moving faster, it is less dense, and the wing "lifts" into the less dense region... therefore as space moves into matter, it becomes less dense, and matter would have a tendancy to move toward the less dense region (in this case, other matter). Since the flow is less dense but an increasing amount of flow is found closer to the sink hole, would the average density remain constant?

Hmm. I just went both ways on that. Did that help at all? Maybe it'll open the door for a more concise explaination from one of our more learn-ed colleages. =)

Ricimer, I missed something there... I was stuck on earth while you were not...


You can free-fall about the sun at acclerations greater than (or less than, depending on distance) 9.8 m/s^2.
There is no "critical" acceleration, unless it acts on different parts of you in different amounts. In a collision, going from 100 mph to 0 in 1s, the impactin part of you is stopped first, then the trailing edge stopped (by running into the front half!) thats what hurts.

(emphasis added, white space clipped)

Makes complete sense now. 8)

Disinfo Agent
2004-Apr-22, 11:26 AM
Here's an interesting link:

Virtual trips to black holes and neutron stars (http://antwrp.gsfc.nasa.gov/htmltest/rjn_bht.html)

nokton
2004-Apr-23, 06:05 PM
Thanx darkdev, at last, an open mind that is not constrained by
current dogma. You take my point well darkdev, indeed, express
it better than I. My feeling is that the dynamics of 'time' cannot be
expressed by an equation, only a concept in a mind, feel you understand.
I look at the night sky, darkdev, what do I see. Black space where stars
are born, so far away, their light not reach me yet. See other stars long
dead now, glowing in their prime. I will not expand this darkdev. feel I
don't have to. Thanx anyway for your response, much appreciate.

Kaptain K
2004-Apr-23, 10:27 PM
My feeling is that the dynamics of 'time' cannot be
expressed by an equation...
If it canot be "expressed by an equation", it is not science.