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kq6up
2008-Sep-09, 04:04 AM
I was teaching my chemistry students the definition of matter today. (Something that has mass and takes up space).

By this definition is a black hole matter? It seems that size is a bit ambiguous for a black hole. However, I consider an electron matter and its size is ambiguous as well.

Thanks,
Chris Maness
KQ6UP

Neverfly
2008-Sep-09, 04:11 AM
Yes, and that Matter is what warps space and creates the gravity well.

Ambiguous is a good term, since no one can see inside of one or predict mathematically what goes on. But the observations that can be made from the outside include the gravitational pull of a black hole which can only be a result of mass.

Jeff Root
2008-Sep-09, 09:07 AM
Hello, Chris!

I'd say that a black hole is not matter. But matter makes the black hole.

On the other hand... Distinguishing between matter and energy is a bit
harder. Since energy is the real source of gravitation, not matter, I can
as well say that energy, not matter, is what makes the black hole. But
all matter has energy -- it wouldn't be matter if it didn't -- and a very
characteristic property of matter that you specified -- mass -- is the
most concentrated form of energy. So the vast majority of the energy
of a collapsing star is in the form of mass.

I consider light to be matter, even though it has no proper mass and
takes up no space by any measure that I know of.

-- Jeff, in Minneapolis

astromark
2008-Sep-09, 10:18 AM
Hmmm... I'm a bit concerned that this is going down the gurggler a bit here. No worries, I am sure yous will put me straight.
Is it matter. Yes it must be., but in what form is this matter? I do not think we know. What do we know? Its very hot. Its very dense. Just by calculating the gravity well we can judge great mass. We think we know about event horizons and singlarities... but we can only observe and calculate. I accept that information has been scrutinized and tested... A great deal of reading has led me to this. I do not know we can answer this question with a definitive absolute. Yes it is matter. I think.

grant hutchison
2008-Sep-09, 10:29 AM
The singularity, depending on your definition, is either a dimensionless point mass (in the maths), or a knot of some unknown quantum gravitational nature (in the physics). So describing that as "matter" seems a little odd.
The rest of the black hole is just a gravitational field. So again "matter" doesn't seem like it does the job.
For distant observers, there's this complex thing going on a Planck length above the event horizon, which Susskind calls the "stretched horizon", storing entropy and information and emitting Hawking radiation.
Is that matter? If it is, is it part of the black hole, or is it a residue of stuff that has fallen into the black hole? And none of that structure is actually there for a free-falling observer crossing the event horizon. So it occupies space under some circumstances, but not under others.

I think I'm not seeing anything in that mix which qualifies as matter according to the provided definition.

Grant Hutchison

Jeff Root
2008-Sep-09, 11:59 AM
To entertain Chris, Mark, and myself, I'll put forth more of my views.



The singularity, depending on your definition, is either a dimensionless
point mass (in the maths), or a knot of some unknown quantum
gravitational nature (in the physics). So describing that as "matter"
seems a little odd.
The matter falling into a black hole reaches the singularity in a short
period of its own proper time. For a few-solar-mass black hole, that
would be milliseconds after crossing the event horizon. It could be
several hours in the case of a supermassive black hole. However,
time in a strong gravity field is slow compared to time elsewhere.
What would be milliseconds or hours to an infaller would be eternity
to others. As matter collapses to create the black hole, it becomes
denser and denser, without limit, since there is nothing to stop the
collapse. But while it is squeezed circumferentially, it is stretched
radially. Everything falling into a black hole ends up getting farther
and farther from everything else. If I fall into a black hole feet-first,
after I have been thoroughly spaghettified the atoms which once
were in my toes will be trillions of miles away from the atoms which
once were in my skull, and getting farther away at an ever-increasing
rate. They will each quicky move beyond the other's horizon. Every
particle will accelerate away from every other particle until light from
one can no longer reach the other.

The matter which formed the black hole in the first place is far, far
below my atoms. It is all even more spaced-out than my atoms.
The whole mess is falling forever into a gravity well which is becoming
deeper and deeper, without limit. But to each particle, the time is
very short, because the increasing radial distance is compensated for
by increasing speed and time dilation. A million years after you see
me disappear into the black hole, the fundamental particles that once
were me will be strung out over a radial distance of perhaps millions
of light-years, but squashed circumferentially to less than the size
of an atomic nucleus. From the point of view of the particles, though,
only a few milliseconds may have passed since I crossed the event
horizon.

So I think the matter is still there, from the point of view of outsiders.
It hasn't reached the singularity yet, and never will, since it has an
infinite distance to fall.



For distant observers, there's this complex thing going on a Planck
length above the event horizon, which Susskind calls the "stretched
horizon", storing entropy and information and emitting Hawking radiation.
Is that matter? If it is, is it part of the black hole, or is it a residue of
stuff that has fallen into the black hole? And none of that structure is
actually there for a free-falling observer crossing the event horizon.
So it occupies space under some circumstances, but not under others.
My understanding is that virtual particles form everywhere -- no more
so near a black hole than anywhere else. What is special at the event
horizon is that the particle pairs can get separated from each other
so that they can't recombine, and one particle may escape. That is
a very rare event for large black holes, only partially compensated
by the larger surface area. The higher gravitational gradient at the
event horizon of a smaller black hole makes separation of the particles
far more common. When the particles separate, they become physical,
and the one which escapes can carry away some of the black hole's
energy and, therefore, reduce its gravity.

-- Jeff, in Minneapolis

transreality
2008-Sep-09, 12:20 PM
if matter, anti-matter and radiation are indistinguishable within a blackhole then they must be reduced to something more fundamental.

Hornblower
2008-Sep-09, 12:30 PM
if matter, anti-matter and radiation are indistinguishable within a blackhole then they must be reduced to something more fundamental.
I would say that fundamental something is energy in its ultimate concentration.

The terms matter and energy, as commonly used in entry-level chemistry among other scientific and technological fields, are holdovers from the era preceding the discovery of their fundamental equivalence.

Digix
2008-Sep-09, 12:47 PM
I suppose fundamental energy container is photon, since it is easy to make and you can create anything from photons alone

so if symmetry is allowed to break in the singularity, all mater will annihilate into photons.
if symmetry remain unbroken singularity will be made of overlapping quarks electrons photons and all other fundamental particles

also we can calculate singularity wavelength which is in same order of of singularity diameter it will be valid for all possible cases.

Digix
2008-Sep-09, 12:52 PM
My understanding is that virtual particles form everywhere -- no more
so near a black hole than anywhere else. What is special at the event
horizon is that the particle pairs can get separated from each other
so that they can't recombine, and one particle may escape. That is
a very rare event for large black holes, only partially compensated
by the larger surface area. The higher gravitational gradient at the
event horizon of a smaller black hole makes separation of the particles
far more common. When the particles separate, they become physical,
and the one which escapes can carry away some of the black hole's
energy and, therefore, reduce its gravity.

-- Jeff, in Minneapolis

there is question in that case what makes that virtual particle pair
is it negative + positive energy? or positive + positive energy.
in any case positive and negative energy is going to fall in same direction according to simple Newtonian physic.

so black hole have equal chance to emit positive or negative energy particles then

Hornblower
2008-Sep-09, 12:55 PM
I suppose fundamental energy container is photon, since it is easy to make and you can create anything from photons aloneI would say that a photon is just one of many manifestations of the fundamental "stuff" that we call energy.


so if symmetry is allowed to break in the singularity, every mater will annihilate into photons.

also we can calculate singularity wavelength which is in same order of of singularity diameter
Can you illustrate that line of thought in appropriate mathematical detail comparable to that of Einstein, Feynman, Hawking, et. al.?

Digix
2008-Sep-09, 01:13 PM
I would say that a photon is just one of many manifestations of the fundamental "stuff" that we call energy.
nobody can suggest anything more fundamental


Can you illustrate that line of thought in appropriate mathematical detail comparable to that of Einstein, Feynman, Hawking, et. al.?
there is no need for big math.

just according to wave particle duality each particle have wavelength which is approximately same as particle size because collisions are most likely to happen in that volume

so you can easily calculate wavelength from Planck formula E=h*(wavelength) E-can be calculated using e=mc from black hole mass

of course you may need to adjust it according to time dilution but that may cancel.

of course that will be very small but finite size
aslo it is not strictly defined as with size of planet or star, it is just wavelenghth but that is about same as size

Jeff Root
2008-Sep-09, 01:24 PM
there is question in that case what makes that virtual particle pair
is it negative + positive energy? or positive + positive energy.
in any case positive and negative energy is going to fall in same
direction according to simple Newtonian physic.

so black hole have equal chance to emit positive or negative energy
particles then
Both particles have positive energy when they are separated and
become physical. It doesn't... uh... matter whether an antimatter
particle or an ordinary matter particle escapes. If either particle
escapes, some energy will be carried away.

-- Jeff, in Minneapolis

grant hutchison
2008-Sep-09, 03:27 PM
Both particles have positive energy when they are separated and
become physical. It doesn't... uh... matter whether an antimatter
particle or an ordinary matter particle escapes. If either particle
escapes, some energy will be carried away.I think Digix is perhaps referring to a conversation we've been having elsewhere.
Since the emitted particle escapes to infinity with positive energy, and since the black hole loses a corresponding amount of mass with the absorption of the trapped particle, a distant observer has to conclude that the trapped particle had negative energy.
It's just energy book-keeping, nothing mysterious, and it certainly means (as you say) that it's a positive quantity of energy that escapes, whichever and whatever particle is involved.

Grant Hutchison

Digix
2008-Sep-09, 04:03 PM
Both particles have positive energy when they are separated and
become physical. It doesn't... uh... matter whether an antimatter
particle or an ordinary matter particle escapes. If either particle
escapes, some energy will be carried away.

-- Jeff, in Minneapolis
both matter and antimatter are positive energy, and also they have equal chances to escape.

but looks at energy conservation then:
one positive escape + another positive fell in to black hole. what do we get?
black hole became even bigger because it gained more mass and also we have one particle for free.
in that case black holes are supposed to grow instead during evaporation.

something seems wrong, don't you think so?

Digix
2008-Sep-09, 04:20 PM
I think Digix is perhaps referring to a conversation we've been having elsewhere.
Since the emitted particle escapes to infinity with positive energy, and since the black hole loses a corresponding amount of mass with the absorption of the trapped particle, a distant observer has to conclude that the trapped particle had negative energy.
It's just energy book-keeping, nothing mysterious, and it certainly means (as you say) that it's a positive quantity of energy that escapes, whichever and whatever particle is involved.

Grant Hutchison

you conclude that indirectly, just because we require energy conservation and hawking radiation to be correct.
but try to think without energy conservation first. if we had observed evaporating black holes and we could measure that they are loosing energy during that then you can conclude that what you say is correct

but currently we have no experimental evidence on that case, so you cant make conclusion from that are based in speculations only.

grant hutchison
2008-Sep-09, 04:57 PM
you conclude that indirectly, just because we require energy conservation and hawking radiation to be correct.
but try to think without energy conservation first. if we had observed evaporating black holes and we could measure that they are loosing energy during that then you can conclude that what you say is correct

but currently we have no experimental evidence on that case, so you cant make conclusion from that are based in speculations only.You've got the logic wrong, there. The theory of Hawking radiation includes energy conservation: it's part of the package. Work is done on virtual particle pairs by tidal gravity forces near the event horizon. This input of energy is sufficient to produce two "real" particles. One ends up inside the event horizon, and one is radiated. The black hole loses mass as a result.
The conservation of energy, and the loss of black hole mass, is part of the theory.

So this:

but looks at energy conservation then:
one positive escape + another positive fell in to black hole. what do we get?
black hole became even bigger because it gained more mass and also we have one particle for free.
in that case black holes are supposed to grow instead during evaporation.

something seems wrong, don't you think so?
is not the theory of Hawking radiation; and, yes indeed, there's something wrong with it because it violates conservation of energy. But that's entirely your doing, not Hawking's.

Grant Hutchison

Digix
2008-Sep-09, 05:28 PM
ok thos dipute id probably solbet
http://en.wikipedia.org/wiki/Hawking_radiation
i found proof that all that hawking evaporation is just simple tunneling since as I expected that is only reasonable way.

so no need for any bizarre stuff like virtual particles or negative energy. Photons from the singularity just tunnel outside.

because if that absurd "no escape from blackhole" and attempts to comply with space time curving hawking decided to use lots of calculations just for one simple result

grant hutchison
2008-Sep-09, 07:04 PM
ok thos dipute id probably solbet
http://en.wikipedia.org/wiki/Hawking_radiation
i found proof that all that hawking evaporation is just simple tunneling since as I expected that is only reasonable way.

so no need for any bizarre stuff like virtual particles or negative energy. Photons from the singularity just tunnel outside.

because if that absurd "no escape from blackhole" and attempts to comply with space time curving hawking decided to use lots of calculations just for one simple resultI think you'll find that the "quantum tunnelling" is also part of Hawking's calculations. It's just a different way of looking at the same quantum events described by the virtual pair/negative energy formulation.

Whoever wrote the current version of the Wikipedia article summarizes the virtual pair/negative energy formulation nicely:
A slightly more precise, but still much simplified, view of the process is that vacuum fluctuations cause a particle-antiparticle pair to appear close to the event horizon of a black hole. One of the pair falls into the black hole whilst the other escapes. In order to preserve total energy, the particle that fell into the black hole must have had a negative energy (with respect to an observer far away from the black hole). By this process, the black hole loses mass, and, to an outside observer, it would appear that the black hole has just emitted a particle.All of which is exactly as I've been describing it to you, Digix, for some time.

But I suspect the first two words of the next sentence in Wikipedia need to be taken with a pinch of salt:
In reality, the process is a quantum tunnelling effect, whereby particle-antiparticle pairs will form from the vacuum, and one will tunnel outside the event horizon."In reality" isn't a phrase you often hear with regard to quantum mechanics, and the Wiki writer seems to be striving to make one interpretation "real" and the other "not real".


Just as a "reality" check (pun intended ;)) here's Kip Thorne:
There are several different ways to picture black hole evaporation, corresponding to the several different ways to formulate the laws of quantum fields in a black hole's curved spacetime. However, all the ways acknowledge vacuum fluctuations as the ultimate source of the outflowing radiation. Perhaps the simplest pictorial description is one based on particles rather than waves.
(Black Holes and Time Warps: Einstein's Outrageous Legacy, Chapter 12.)He then goes on to give the same virtual pair/negative energy picture Wiki uses, but in more detail. (I can't seem to find any mention of the quantum tunnelling picture in his book, but it's a big book and I haven't searched it assiduously.)

Edward Harrison takes the same tack. Having given the virtual pair/negative energy description of Hawking radiation, he goes on:
Particles in their wavelike manner penetrate seemingly impenetrable barriers.This behaviour offers another way of looking at particle emission by black holes. A particle can tunnel through the event horizon and emerge as a wave.
(Cosmology: The Science of the Universe Chapter 13.)So: the "virtual pair/negative energy" and "quantum tunnelling" descriptions seem to be complementary views of the same quantum events, despite the Wiki writer's effort to label just one of them "real".

To illustrate the continuity between the two descriptions, I've seen another version that falls halfway between them. In that description, the tunnelling take place by time-reversing the virtual anti-particle that falls into the event horizon. It is treated as a particle which moves backwards in time to get out of the event horizon, and then becomes the forward-in-time particle that escapes.

Grant Hutchison

Digix
2008-Sep-09, 07:36 PM
To illustrate the continuity between the two descriptions, I've seen another version that falls halfway between them. In that description, the tunnelling take place by time-reversing the virtual anti-particle that falls into the event horizon. It is treated as a particle which moves backwards in time to get out of the event horizon, and then becomes the forward-in-time particle that escapes.


never mind that, since result is mostly same anyway.
just I am allergic to time machines and imaginary green gnomes, so if someone will use some of these words in their theory I will declare it as nonsense. especially if something "moves backwards in time".
also there is actually no need for that since we have nice and clean alternative explanation.

however in any case there is some small possibility that this hawking radiation will not work as expected

grant hutchison
2008-Sep-09, 08:08 PM
... so if someone will use some of these words in their theory I will declare it as nonsense ...Ah.
I always greatly admire a well-reasoned argument.

Grant Hutchison

Neverfly
2008-Sep-09, 08:12 PM
Well, I am a bit baffled so since Grant is coming under high recommendations...:
If you can say that a Black Hole does not contain "matter" then how do you account for the gravity which can only be a product of mass?

Hornblower
2008-Sep-09, 08:16 PM
Well, I am a bit baffled so since Grant is coming under high recommendations...:
If you can say that a Black Hole does not contain "matter" then how do you account for the gravity which can only be a product of mass?
Grant was saying that it does not fit the definition used by the opening poster.

tdvance
2008-Sep-09, 08:29 PM
It seems to depend really heavily (ha ha) on the precise definition of matter. If it's just something that warps space, black holes, and all forms of energy, are matter. If it is something with nonzero rest mass (whatever "rest" means near something that bends space--and time--all up) I'd think a black hole is matter.

"takes up space"--that has to be defined too--what is the volume of a black hole? Is it a function of the surface area of the event horizon? Or is it 0 (the singularity) or perhaps even "Plank volume"?

My HS chemistry teacher--I blame him for destroying my belief--all through elementary and the start of high school, I was told, electrons orbit the nucleus like planets around the sun. Then the HS teacher starts talking about the various types of quantum orbitals (which I used to have memorized but not anymore)--all the previous teachers lied to me!!! :)

Digix
2008-Sep-09, 08:32 PM
Ah.
I always greatly admire a well-reasoned argument.
Grant Hutchison

do not take two words out of context please.

grant hutchison
2008-Sep-09, 09:22 PM
do not take two words out of context please.I'm sorry you feel I've taken two words out of context, although I'm not sure which two words you feel I've singled out in this way.

Declaring a theory to be "nonsense" simply because it contains certain words or phrases is ... um ... nonsense.
You've already demonstrated how badly wrong that can go, by using "negative energy" and "virtual particles" as an excuse to dismiss one mainstream description of Hawking radiation. But when pressed it's pretty clear that your objections are to what you think these expressions mean, rather than what they actually mean.

Grant Hutchison

grant hutchison
2008-Sep-09, 09:23 PM
do not take two words out of context please.I'm sorry you feel I've taken two words out of context, although I'm not sure which two words you feel I've singled out in this way.

Declaring a theory to be "nonsense" simply because it contains certain words or phrases is ... um ... nonsense.
You've already demonstrated how badly wrong that can go, by quoting "negative energy" and "virtual particles" as an excuse to dismiss one mainstream description of Hawking radiation. But when pressed it's pretty clear that your objections are to what you think these expressions mean, rather than what they actually mean.

Grant Hutchison

Digix
2008-Sep-09, 09:56 PM
I'm sorry you feel I've taken two words out of context, although I'm not sure which two words you feel I've singled out in this way.
Declaring a theory to be "nonsense" simply because it contains certain words or phrases is ... um ... nonsense.
Grant Hutchison

again please understand that I don't say that hawking radiation does not exist for sure it just possible that his theory is wrong.
everything that involves "time going backwards" or interaction with "imaginary" stuff looks unserious.if you use such thing in your explanation i will try to isolate them and analyze independently in that case effects will not cancel and logical problems will arise. like with "negative energy", if you use such concept I like to take it out of the whole situation and analyze it independently.
i wonder how will you look into design of spaceship that has word "perpetual motion engine" somewhere in the text?


You've already demonstrated how badly wrong that can go, by quoting "negative energy" and "virtual particles" as an excuse to dismiss one mainstream description of Hawking radiation.But when pressed it's pretty clear that your objections are to what you think these expressions mean, rather than what they actually mean.
I used words in standard definition by dictionary and by also choosing any of available mainstream definitions that I like if physic have dual meaning definitions then it is not my problem
http://en.wikipedia.org/wiki/Virtual
http://en.wikipedia.org/wiki/E%3Dmc

anyway there is no need to argue further about topic, that hawking radiation is not so impossible, because I found anther mainstream theory which is ok for me to accept.

Jeff Root
2008-Sep-10, 05:11 AM
Grant,

Ah! Acknowledged that I didn't fully understand what Digix was asking,
and I depended entirely on WRAM (wet random access memory) when I
said that both particles have positive energy. I agree that the particles
falling in have negative energy relative to distant observers.

I'll bet that Ken and Richard wish I would concede to their corrections
of my statements, too. The difference is that their arguments, while
effective at shutting me up, sometimes don't convince me, so I have
to think about them for a while. Yesterday I came up with a rejoinder
to a statement made last April having to do with planet rotation.

-- Jeff, in Minneapolis

eburacum45
2008-Sep-10, 07:58 AM
Well, I am a bit baffled so since Grant is coming under high recommendations...:
If you can say that a Black Hole does not contain "matter" then how do you account for the gravity which can only be a product of mass?
Gravity is the product of 'mass/energy', which need not be matter. Energy alone is enough. If you (for instance) were to shine a light beam into a black hole, the energy content (and therefore the gravity) of the hole would increase.

Jeff Root
2008-Sep-10, 10:01 AM
I'll repeat that as far as I'm concerned, light is a form of matter.

Lest you infer that I think everything is matter, I'll list a few examples
of things that are not matter:

Color, brightness, time, temperature, angle, distance, speed, loudness,
happiness, nervousness, cost, return on investment, life, and death.

To possibly help clarify this, I'll add a few more:

Information, value, satisfaction, greed, digestion, indigestion, hiccups,
forgetfulness, strength, quantity, quality, evolution, Boyle's law, music,
choreography, wisdom, taste, discretion, valor, good, beauty, and evil.

-- Jeff, in Minneapolis

eburacum45
2008-Sep-10, 11:34 AM
Life isn't matter? An interesting idea- but not, I fear, one for this thread.

grant hutchison
2008-Sep-10, 11:41 AM
Well, I am a bit baffled so since Grant is coming under high recommendations...:
If you can say that a Black Hole does not contain "matter" then how do you account for the gravity which can only be a product of mass?Sorry, Neverfly, I missed this one. Hornblower and eburacum45 seem to have addressed it, though.

Grant Hutchison

tdvance
2008-Sep-10, 03:58 PM
Living things are made of matter, but I figure JR is talking about the concept "life'--which is no more matter than "information" is, despite the latter living inside a material computer or brain.

Neverfly
2008-Sep-10, 04:09 PM
Sorry, Neverfly, I missed this one. Hornblower and eburacum45 seem to have addressed it, though.

Grant Hutchison

Yeah, for all my whining about misconceptions about Black Holes floating around, it seems I have a few myself.

Time to hit the books...

loglo
2008-Sep-10, 06:26 PM
everything that involves "time going backwards" or interaction with "imaginary" stuff looks unserious.if you use such thing in your explanation i will try to isolate them and analyze independently in that case effects will not cancel and logical problems will arise.

A quick look at the basis of Feynman(/Stuckelberg) diagrams may rid you of this notion. The idea of antiparticles moving backwards in time has been useful for the renormalisation of quantum theory for over 50 years.

grant hutchison
2008-Sep-10, 07:38 PM
Yesterday I came up with a rejoinder
to a statement made last April having to do with planet rotation.That's the worst case of esprit de l'escalier I've ever encountered. it must have been a very long staircase. :)

Grant Hutchison

transreality
2008-Sep-10, 10:10 PM
When hawking et al talk about information being possibly lost or conserved in a blackhole, doesn't this mean that information is a component of matter? So that when matter enters a blackhole the information may be stripped from it, such that it is no longer matter.

tdvance
2008-Sep-10, 10:25 PM
Not really--information is essentially the combined state matter is in--charge, spin, position, momentum, etc. for each fundamental particle. (and to make it more complex, the state is a quantum state so what's observed is uncertain).

Now, I don't know--is the collapsing of a waveform the destruction of information? Or the creation of information?

transreality
2008-Sep-10, 11:54 PM
All those properties charge spin, etc they aren't retained by the individual particle in the singularity are they, but contribute to the total measurement expressed by the blackhole?

Hornblower
2008-Sep-11, 12:37 AM
Not really--information is essentially the combined state matter is in--charge, spin, position, momentum, etc. for each fundamental particle. (and to make it more complex, the state is a quantum state so what's observed is uncertain).

Now, I don't know--is the collapsing of a waveform the destruction of information? Or the creation of information?
If we can develop a workable theory which unifies gravitation and quantum mechanics, the singularity at the center may go away, and we might find and answer one way or the other.

Jeff Root
2008-Sep-11, 03:10 AM
Yesterday I came up with a rejoinder to a statement made last
April having to do with planet rotation.
That's the worst case of esprit de l'escalier I've ever encountered.
it must have been a very long staircase. :)
Oh, I've had much longer delays than that, although I don't think I
can cite any specific examples. A year or two ago I was thinking
about something somebody said fifteen or twenty years earlier, and
I realized that during that entire time I had misunderstood what they
meant. New knowledge I had acquired in the interval enabled me to
give it the correct interpretation once I thought about it again.

The present case is more a delay between being given a problem
and coming up with a solution. In April, I asked why planets rotate
in the same sense as they orbit the Sun. Considering that speeds
of particles in circular orbits in the protoplanetary nebula decreased
with distance from the Sun, it seemed to me that the resulting planet
rotation should be in the opposite direction. I sent an e-mail to a
local astronomer, who replied that the cause is conservation of
angular momentum.

I already knew that angular momentum would be conserved, and
I was fairly sure that angular momentum of particles farther from
the Sun is greater (confirmed for me today by Ken G), but I didn't
see how that was an answer to my question. Yesterday, while
reading a post asking the same question, I came up with a possible
solution: The particles which hit the forming planet are *not* in
circular orbits, but very slightly elliptical orbits, in which the speeds
are different. So this morning I finally composed and sent a reply
to the astronomer, and I'll have to go check my e-mail now to find
out if he has replied to me in turn.

-- Jeff, in Minneapolis

astromark
2008-Sep-11, 08:25 AM
Not being the fastest flame on the cake some times is frustrating, but. This time I agree with 'Digex'

Posted by Digix
everything that involves "time going back-wards" or interaction with "imaginary" stuff looks unserious.if you use such thing in your explanation i will try to isolate them and analyze independently in that case effects will not cancel and logical problems will arise... and, thank you.

Firstly I have lost how this is related to the OP of Does a Black Hole contain matter?
It would seem that you must at first decide on the parameters of what matter is. For me thats easy, If its a object of any substance then it is matter. Having gravity would seem a good indercation. As complex as definitions can be. This idea of plasma state or super heated dense matter becomes some thing other than matter is not the way I see it. Pure energy is matter at a higher state than we are used to finding it. The rules of nuclear structures are changed in that what we imagine a BH is.
When a conclusion is reached, or a test conferms... then we can be said to have prov-en a theorie... it mater's not where in the universe we are, the rules are the same.