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chivis
2003-Feb-25, 04:32 AM
Hello folks,

After I almost brought the house down on my first couple posts, i figured I should try to gain a small amount of credibility by starting my own thread.

I have many solid questions that I would like to hear views on. I do not want to start a flame war, but rather get some valuable feedback.

There are definately some smart folks around this board and I'm sure some will love to take sink there teeth into some good convo.

My first question is this:

Where are we in terms of our social & technological development as a civilization and how far is mankind from being able to survive a major event such as a Planet X type object or some form of natural, mass extinction event?

This would mean either colonization of another planet or the technology to survive an event such as this on Earth.

~Chivis

g99
2003-Feb-25, 04:39 AM
I think that to survive a cataclysmic "planet killer" type event like PX is supposed to be, we would have to have a self sustaining colony on another world. They would need to be significant in number (several thousand) for a genetically viable population and have the ability to make their own food. untill then we will go extinct.

We currently have no weapon (other than a NU-KU-LAR weapon /phpBB/images/smiles/icon_smile.gif) that could stop, or destroy a planet. Even if we did, the effects of the extra gravity well or the debris from its destruction would probobly kill us anyways.

The only thing would be to get to someplace else.


Now this is all basing that PX is real (it isn't).

canadianfury
2003-Feb-25, 04:51 AM
On 2003-02-24 23:39, g99 wrote:

We currently have no weapon (other than a NU-KU-LAR weapon /phpBB/images/smiles/icon_smile.gif) that could stop, or destroy a planet. Even if we did, the effects of the extra gravity well or the debris from its destruction would probobly kill us anyways.



An excellent point. It would not even need to hit us or be that large of a body. The extra gravity of a near passer could throw off the Earth's somewhat delicate equillibrium and that would be the end. Colonization of the moon would be out as well, for obvious reasons. Time to build a Titan AE. /phpBB/images/smiles/icon_smile.gif

chivis
2003-Feb-25, 04:56 AM
Then why are we still here? Mankind has to have survived such an event before.

There must be a reoccuring event that "refreshes" our planet. You can't dispute the evidence to support this. (ie Ice Ages, Pole Shifts, Great Floods, lost civilizations)

Mankind surely has encountered these events before and survived. Otherwise, we would not be having this conversation.

The problem is this each event is different. Some more severe then others....32 million, 64 million, 96 million....can we survive the big one? I think not!

~Chivis

canadianfury
2003-Feb-25, 05:01 AM
We probably will not survive the "big one" (whatever that is). I would look to man's own record here on Earth before I would look to the skys. Given our current population trend and our speed of consumption we are probably closer to a mass extinction due to ourselves, than due to that of the Universe.

PS another good point by g99 NUKES!!

Lexx_Luthor
2003-Feb-25, 05:21 AM
Not sure if a near miss by even the most massive asteroid (Ceres) would affect Earth. Interesting idea though.


Where are we in terms of our social & technological development as a civilization...? /phpBB/images/smiles/icon_biggrin.gif hehehe http://www.worldbank.org/depweb/ http://www.worldbank.org/depweb/images/dep-small2.gif





Given our current population trend and our speed of consumption we are probably closer to a mass extinction due to ourselves, than due to that of the Universe.If you are going to quote Secretary of State Henry Kissenger, please give him credit. Thank you. /phpBB/images/smiles/icon_biggrin.gif

For those not familiar with demographic "science," here is Kissenger's population memo that you refer to. Full text at bottom of this introduction.

http://www.africa2000.com/INDX/nssm200.htm



_________________
Stanly is a moron, kai is a walking dead beet, Xev just want sex.

<font size=-1>[ This Message was edited by: Lexx_Luthor on 2003-02-25 00:26 ]</font>

canadianfury
2003-Feb-25, 05:29 AM
On 2003-02-25 00:21, Lexx_Luthor wrote:
Not sure if a near miss by even the most massive asteroid (Ceres) would affect Earth.


Just think about the moon size. If we had a larger or smaller one it would effect the Earth. How bad it would be is up for debate. Also I was a little loose with the term "near miss" given the size of our solar system. I was thinking within 3.84X10^8 meters (within the moon's orbit.)

chivis
2003-Feb-25, 05:39 AM
I really dont think it would take much to do serious damage here.

Wouldnt an equal gravitational pull as the moon raise the oceans like 10 ft or so? Surely some of the "big" comets out there are much bigger and denser then our moon. imagine 5 times the dinsity and pull....50-100 ft possibly?

canadianfury
2003-Feb-25, 05:43 AM
On 2003-02-25 00:39, chivis wrote:
I really dont think it would take much to do serious damage here.

Wouldnt an equal gravitational pull as the moon raise the oceans like 10 ft or so? Surely some of the "big" comets out there are much bigger and denser then our moon. imagine 5 times the dinsity and pull....50-100 ft possibly?




Exactly!

Lexx_Luthor
2003-Feb-25, 06:08 AM
Granted. But would the effect be permanent (for Earth not humans /phpBB/images/smiles/icon_biggrin.gif )? Would it make the Earth tip over or something?

Just thinking, say the limit for a near miss is 100 kilometers (Ceres limb cutting into upper atmosphere) and so it would appear about...

hold on....

I'm BACK!!!

Okay, I whipped out my fortran90 sim and set the Moon's radius as 500km at an altitude of 600 km above Earth (thus 100km between Earth~n~Moon (call the Moon Ceres in this case)

I landed on Moon/Ceres and then hopped directly down to Earth just 100km below and Ceres appeared 56.4 degrees in radius or 2x56.4 degrees in diameter. Ceres stretched across the sky big time.

If the effects on ocean are temporary, the buzz through the atmosphere would be pretty bad too but surely not permenent (for Earth not humans /phpBB/images/smiles/icon_biggrin.gif ).

The Earth as a planet is pretty strong; much stronger than advertised at the World Bank website. /phpBB/images/smiles/icon_biggrin.gif

sarongsong
2003-Feb-25, 06:34 AM
Lexx says:"...If you are going to quote Secretary of State Henry Kissenger, please give him credit. Thank you.
For those not familiar with demographic "science," here is Kissenger's population memo that you refer to...."
So where's the source of Henry's quote?
Certainly not in your reference.

Lexx_Luthor
2003-Feb-25, 07:19 AM
Here is the direct link beyond the introduction...my mistake

http://www.africa2000.com/SNDX/nssm200all.html


I. Introduction - A U.S. Global Population Strategy

There is no simple single approach to the population problem which will provide a "technological fix." As the previous analysis makes clear the problem of population growth has social, economic and technological aspects all of which must be understood and dealt with for a world population policy to succeed....
:
:
:
A. Basic Global Strategy

The following basic elements are necessary parts of a comprehensive approach to the population problem which must include both bilateral and multilateral components to achieve success. Thus, USG population assistance programs will need to be coordinated with those of the major multilateral institutions, voluntary organizations, and other bilateral donors.

HENRY A. KISSINGER /phpBB/images/smiles/icon_biggrin.gif

Sorry, I guess the quoted words just sounded familiar to me from somewhere. I don't know what's going on either (if you do let us know).



Lexx...
I love that name. Thanks! /phpBB/images/smiles/icon_biggrin.gif
_________________
Stanly is a moron, kai is a walking dead beet, Xev just want sex.

<font size=-1>[ This Message was edited by: Lexx_Luthor on 2003-02-25 04:17 ]</font>

Lazlar
2003-Feb-25, 08:49 AM
"""...like a blazing comet, seems destined either to inspire with fresh life and vigour, or to scorch up and destroy the
shrinking inhabitants of the earth, have all concurred to lead many able men into the opinion that we were touching on a period big with the most important changes, changes that would in some measure be decisive of the future fate of mankind.

It has been said that the great question is now at issue, whether man shall henceforth start forwards with accelerated
velocity towards illimitable, and hitherto unconceived improvement, or be condemned to a perpetual oscillation between happiness and misery, and after every effort remain till at an immeasurable distance from the wished-for goal. """

Twin fools: Kissenger and Malthus

Both think that people are a problem.

Neither consider human creativity in their economic calculations.

Both think resources are static.

Both are fools.

Malthus is dead.

Kissenger (and his ilk) remains a danger to all that is good about people.

Lexx_Luthor
2003-Feb-25, 09:42 AM
whether man shall henceforth start forwards with accelerated velocity towards illimitable, and hitherto unconceived improvement, or be condemned to a perpetual oscillation between happiness and misery,Sweet quote Laz. I was thinking I had gone off topic, but that quote made me think again. Where is it from?

The old online LM magazine had a beautiful article entitled "Has the Moon Shrunk?" that offered opinion on why people have forgotten the Apollo landings. Basically, the idea was that we have become a risk averse society. It crushes human endeavors. I don't have the article anymore.

I guess you have seen Julian Simon http://www.africa2000.com/RNDX/simon.html

The Epilogue is pretty funny. World Bank called him a "Criminal" during one conference.

I fought the Bank and the Bank won. /phpBB/images/smiles/icon_biggrin.gif

You know, considering the amount of money we dump into the "institutions" mentioned by Kissenger above, there is money enough for a vast space program we could share with most of the world. I just don't know what is going on. Something bizzare. I hope that was back on topic.

Lazlar
2003-Feb-25, 10:46 AM
The quote is from some page I found on a Google, sorry, should have posted the link while I had it.

Below is another Google - Malthus link that illuminates his perverted way of thinking.

I think we will not get very far into space until some greedy ******* finds some way to get rich from it. Government will never do it.

I want to retire to a condo on the Moon.

Government will never make that possible, with greedy *******s, there is a chance.

Lazlar

Lazlar
2003-Feb-25, 10:49 AM
http://www.fordham.edu/halsall/mod/1798malthus.html

Kaptain K
2003-Feb-25, 12:27 PM
Surely some of the "big" comets out there are much bigger and denser then our moon.
Chivis,
I don't know where you are getting your information, but there are no comets that are either bigger or denser than our moon. The nucleus of a comet is a small chunk of "dirty snow". Most of them have a diameter of a few kilometers to several tens of kilometers. Their density is less than 1 gram/cc. The largest known "comet-like" object is Chiron aka asteroid 2060, which orbits the Sun between Saturn and Uranus. It is between 148 and 208 kilometers in diameter - far smaller than the Moon. The coma of a comet (the visible head of a comet) can be several million kilometers in diameter, but is only slightly denser than interplanetary space (i.e. a better vacuum than we can create on Earth). The tail of a comet can stretch over 1 AU (150 million kilometers), but again, it is very thin.

informant
2003-Feb-25, 12:54 PM
On 2003-02-24 23:39, g99 wrote:

We currently have no weapon (other than a NU-KU-LAR weapon /phpBB/images/smiles/icon_smile.gif) that could stop, or destroy a planet. Even if we did, the effects of the extra gravity well or the debris from its destruction would probobly kill us anyways.



I am guessing that a lot depends on how far away the object is when it is detected. Even if we can't destroy it, could we change its course if we identified it soon enough? And how soon would that be?

kilopi
2003-Feb-25, 01:07 PM
I see that Kaptain K has answered your claim about "big comets." I have another disagreement:


On 2003-02-24 23:56, chivis wrote:
Then why are we still here? Mankind has to have survived such an event before.
Not necessarily, depends upon what you mean by "such an event." It appears that you're talking about the "planet killer" type events that g99 mentioned.


There must be a reoccuring event that "refreshes" our planet. You can't dispute the evidence to support this. (ie Ice Ages, Pole Shifts, Great Floods, lost civilizations)

Mankind surely has encountered these events before and survived. Otherwise, we would not be having this conversation.
Some of those are a lot less destructive than a Planet X would be--and there's no evidence that mankind has survived a disaster on the order of a Planet X impact. And quit calling me Shirley.

sts60
2003-Feb-25, 02:48 PM
Ahh, we haven't had a "Pole Shift" anytime recently (I mean way longer than proto-humans have been around). True, the magnetic pole has flipped, but that's waaaay different than the spin axis of the Earth getting knocked over, which would require enough energy that nobody would have to worry about their supply of water-purification tablets.

I date myself, but there was a toy which consisted of a shallow dish with four stations around it, where you wound up these little tops with string and then sent them forth to do battle with one another. Should have labeled one "Earth" and another "Planet X" /phpBB/images/smiles/icon_smile.gif, but that was before the twinkies got fired up on PX...

<font size=-1>[ This Message was edited by: sts60 on 2003-02-25 09:50 ]</font>

chivis
2003-Feb-25, 03:16 PM
On 2003-02-25 07:27, Kaptain K wrote:
...there are no comets that are either bigger or denser than our moon. The nucleus of a comet is a small chunk of "dirty snow". Most of them have a diameter of a few kilometers to several tens of kilometers.

I'm sorry but I have a VERY hard time believing that comet are simply "dirty snowballs". There has to be more to it then that.

Where do comets originate?

~Chivis

logicboy
2003-Feb-25, 03:20 PM
I would think they have been around since the Big Bang or possibly from some collision. Dirty Snowballs is just a saying for ICE and ROCK mixture which is what a comet basically is.

TriangleMan
2003-Feb-25, 03:29 PM
On 2003-02-25 10:16, chivis wrote:
I'm sorry but I have a VERY hard time believing that comet are simply "dirty snowballs". There has to be more to it then that.


Actually, I am having trouble thinking of anything else that comets could be made of other than ice and rock.

Chivis, can you suggest some other things that you believe that comets might be made of?

nebularain
2003-Feb-25, 03:32 PM
Here's some info on what is known about comets:

http://science.howstuffworks.com/comet.htm

It is correct that they are more than "dirt and H20." They can have methane, ammonia, and CO2. (See page 2 of the link.)

logicboy
2003-Feb-25, 03:39 PM
Ice is a broad term frozen H2O, CO2, Methane etc.

chivis
2003-Feb-25, 03:47 PM
On 2003-02-25 10:29, TriangleMan wrote:
Actually, I am having trouble thinking of anything else that comets could be made of other than ice and rock.

Chivis, can you suggest some other things that you believe that comets might be made of?


Thanks for asking.....I have thought of one possible scenario...

When our sun or another star has a CME how much matter is ejected out into space? I have seen some very large CMEs. There must be enough matter to build a object the size of our moon.

Could this matter, through gravity, come together and create a comet? Is that possible?

Over millions of years would this comet continues to collect matter ejected from CMEs and other matter in space and become larger and denser.

I think comets are created...not just remnants of some "big bang" or planetary breakup....usually things start small and grow bigger over time...rather then start big and get smaller over time.

~Chivis

logicboy
2003-Feb-25, 04:07 PM
On 2003-02-25 10:47, chivis wrote:


On 2003-02-25 10:29, TriangleMan wrote:
Actually, I am having trouble thinking of anything else that comets could be made of other than ice and rock.

Chivis, can you suggest some other things that you believe that comets might be made of?


Thanks for asking.....I have thought of one possible scenario...

When our sun or another star has a CME how much matter is ejected out into space? I have seen some very large CMEs. There must be enough matter to build a object the size of our moon.

Could this matter, through gravity, come together and create a comet? Is that possible?

Over millions of years would this comet continues to collect matter ejected from CMEs and other matter in space and become larger and denser.

I think comets are created...not just remnants of some "big bang" or planetary breakup....usually things start small and grow bigger over time...rather then start big and get smaller over time.

~Chivis





I dont want to handle responding to the rest of this post but answer me this.

In order for things to get bigger something else has to become smaller. Explain what starts small and grows bigger?

Lexx_Luthor
2003-Feb-25, 05:38 PM
I would imagine stellar discharges dissipate into space. Not enough gravity to collapse it into a comet. Unless electrical charges help in the plasma helps. I dunno.


Ice is a broad term frozen H2O, CO2, Methane etc.
Yeah, I think "dirty snowball" is meant to include volatiles and non~volatiles...or volatiles, Si/C, and metals.

Basically, planet stuff. /phpBB/images/smiles/icon_biggrin.gif

I thought comets are like outer solar system moons until they come close to the sun enough times and they lose their volatiles and then are like basic asteroids: dirt~n~metals.

Something I've been wondering:: what is the mass of the Oort Cloud. Could that affect the debate on the angular momentum of the Solar System? Just popped into my mind again.

aurorae
2003-Feb-25, 06:56 PM
On 2003-02-25 10:47, chivis wrote:
Could this matter, through gravity, come together and create a comet? Is that possible?


This matter would be composed of elements. Stuff like hydrogen, oxygen, etc.

Asteroids tend to be more rocky, because they probably formed close enough to the sun that the volatiles were driven off.

Comets tend to have more volitile material, because they formed in the far reaches of the solar system (think Kuiper belt and Oort cloud). That is why comets have tails that form when they get close to the sun.

You are right that early on in our solar sytem, objects grew by accretion. I think there might be some confusion over the chemistry of it all.

traztx
2003-Feb-25, 07:22 PM
On 2003-02-25 10:47, chivis wrote:

When our sun or another star has a CME how much matter is ejected out into space? I have seen some very large CMEs. There must be enough matter to build a object the size of our moon.

Could this matter, through gravity, come together and create a comet? Is that possible?

Over millions of years would this comet continues to collect matter ejected from CMEs and other matter in space and become larger and denser.


Yes. Mainstream astronomy suggests that we are made of "star stuff". The immense pressures of stars fuse light elements like hydrogen into heavier elements like helium, oxygen, carbon, silicon, etc. Mass is ejected from stars (CME) or at the end of the star's life a nova can eject huge mass into space.

Oxygen and hydrogen (steam/water/ice) are highly attracted to each other. So are oxygen and silicon (lava/rock). Thus we get a lot of ice and rock in the coldness of space. Other molecules that are normally gases here on Earth are frozen solid in deep space because there is little star heat that far out.

In deep space, free floating objects eventually collide and stick together. The solid pieces might have rock, metal, ice, anything. But there are a lot of small particles of frozen water and gas floating around that can stick to the clumps. As more small pieces collect into clumps, the object gets bigger and bigger.

In near space, the sunlight heats up objects. Water ice and frozen gases sublime into gas vapor. This carries heat away from the central clump, keeping it very cold. This makes it a gradual process and is why the coma grows when comets are thrown into orbits that take them nearer to the sun.



On 2003-02-25 10:47, chivis wrote:

I think comets are created...not just remnants of some "big bang" or planetary breakup....usually things start small and grow bigger over time...rather then start big and get smaller over time.


I agree. They grow in deep space, but when they are perturbed to fly by the sun, they get smaller because many of their materials only stay solid far away from the sun's heat.

<font size=-1>[ This Message was edited by: traztx on 2003-02-25 14:25 ]</font>

chivis
2003-Feb-25, 08:28 PM
On 2003-02-25 14:22, traztx wrote:

I agree. They grow in deep space, but when they are perturbed to fly by the sun, they get smaller because many of their materials only stay solid far away from the sun's heat.



OK...Then how can we be sure that there isnt any bigger or denser comets then our own moon?

Isnt the time a comet spends near a heat source like our sun, a small comparison to the amount of time spent out in deep space...So theoritically, a comet has the potential to keep building mass while in deep space..

What about comet NEAT with a 37,000 year orbit. Wouldnt that be eoungh time through the Oort Cloud to produce a larger sized comet?

~Chivis

traztx
2003-Feb-25, 09:14 PM
On 2003-02-25 15:28, chivis wrote:
OK...Then how can we be sure that there isnt any bigger or denser comets then our own moon?


I'll let someone else answer that one. All I know is that none have been discovered yet.



On 2003-02-25 15:28, chivis wrote:
Isnt the time a comet spends near a heat source like our sun, a small comparison to the amount of time spent out in deep space...So theoritically, a comet has the potential to keep building mass while in deep space..


Good question. I'll leave that to the experts. My guess is that this can happen for very long period comets in early star systems that still have a lot of little stuff. Over billions of years, the little stuff gets blown out so there is less to accrete.



What about comet NEAT with a 37,000 year orbit. Wouldnt that be eoungh time through the Oort Cloud to produce a larger sized comet?


No, that one came in closer than Mercury. It's doomed.

g99
2003-Feb-25, 09:24 PM
On 2003-02-25 09:48, sts60 wrote:

I date myself, but there was a toy which consisted of a shallow dish with four stations around it, where you wound up these little tops with string and then sent them forth to do battle with one another. Should have labeled one "Earth" and another "Planet X" /phpBB/images/smiles/icon_smile.gif, but that was before the twinkies got fired up on PX...



I have played that game in the 80's. Very fun. /phpBB/images/smiles/icon_smile.gif

----------------------------
We would all be dead if PX was real. I am not talking about a 5 mile wide asteroid, i am talking about a planet.

How do you stop something that big? If you did, even if it was out near pluto, it would really mess with the orbits of Neptue, Uranus, and Pluto. Maybe sending one of the planets inwards towards the inner planets. This could mess up our orbit or send a few asteroids from the belt inot a orbit that could collide with us in a few hundred years.

Now this would be a very long process of chain reactions. Most of us will be long gone by then. But it would be a unstoppable chain reaction. It would take a planet a long time,(years) to travel throught our solar system. Unless it was traveling near light speed. (and that can't be done)

If the Planet was stopped near earth, the gravity well of the planet would knock us off our orbit. (Off topic: The same reason why artificial gravity would not work. Could you imagine a earth sized gravitational mass suddenly apearing in Earth orbit? Ouch!)

We could not launch a Nuklear weapon,(there is a difference b/t Nuklear weapons and NU-KU-LAR weapons. /phpBB/images/smiles/icon_smile.gif) but very few of them could reach orbit. Let alone deep space. Most were built to hit the surface of the earth, not a extra planetary object.

Even if we could launch every one into space all they would do is irradiate the surface and vaporize a few thousand tons of mass. There would still be much more mass to deal with.

chivis
2003-Feb-26, 02:57 AM
On 2003-02-25 15:28, chivis wrote:
Isnt the time a comet spends near a heat source like our sun, a small comparison to the amount of time spent out in deep space...So theoritically, a comet has the potential to keep building mass while in deep space..


Good question. I'll leave that to the experts. My guess is that this can happen for very long period comets in early star systems that still have a lot of little stuff. Over billions of years, the little stuff gets blown out so there is less to accrete.
[/quote]

Is there someone out there that can answer this one for me?


<font size=-1>[ This Message was edited by: chivis on 2003-02-25 22:00 ]</font>

RichField
2003-Feb-26, 05:23 AM
Ok, here's my attempt at an answer, with lots of assumptions.

Given:
Long period comet on 37,000 year orbit with eccentricity of 0.7. (I don't know the feasibility of these parameters, but they should give a nice long orbit)

We can calculate its major and minor axes and then get a rough estimate for its path length. I get 8.82E14 m

I need a density for the dust and mass spread throughout space. I couldn't find one so I assumed that 99% (probably low) of the solar system's mass is contained in the sun an planets within pluto's orbit. That gives a density for the 'empty space' of 2.31E-11 kg/m^3

Assume at its closest approach to the sun the comet is 10 km in diameter. For simplicity I also assumed that it had a density of 2000 kg/m^3 giving a total mass of 8.38E15 kg. Rather than try to account for growth effects over time I just assumed it would accumulate any mass within a 100 km radius of itself along its path.

We get the total volume of the accumulated path as V = piR^2 = 2.77E25 m^3.

To find the mass accumulated just multiply density times volume, I get 6.39E14 kg accumulated by the comet over 37,000 years.

That's not even enough to double the mass of the comet, let alone come close to the mass of the moon ~ 10^22 kg

I've tried to make 'worst case' assumptions to get as much mass as possible over the trip and still can't get a significant increase. My feeling is this is an upper bound on mass and that refinements would lead to a lower value.

Regarding my assumptions:

I think the 'density of space' is several orders of magnitude too high
I make attempt to determine if this is even a valid orbit, I only use it to get an orbit length which I think is within an OoM. (It is only linearly dependent on length in any case)
The calculation neglects the time when it is still close to the sun and losing mass.


If you disagree with any of my assumptions let me know which one, and why.

Hope this helps.

Rich

Kaptain K
2003-Feb-26, 03:09 PM
OK...Then how can we be sure that there isnt any bigger or denser comets then our own moon?

Because, if it were bigger and denser than our moon, it would be a planet.

kilopi
2003-Feb-26, 03:36 PM
On 2003-02-26 00:23, RichField wrote:
I need a density for the dust and mass spread throughout space. I couldn't find one so I assumed that 99% (probably low) of the solar system's mass is contained in the sun an planets within pluto's orbit. That gives a density for the 'empty space' of 2.31E-11 kg/m^3
That does seem high. It's only 10^10 less than normal Earth air at sea level, no?


On 2003-02-26 10:09, Kaptain K wrote:

OK...Then how can we be sure that there isnt any bigger or denser comets then our own moon?
Because, if it were bigger and denser than our moon, it would be a planet.

I'd still like to know what people would do if we found a KBO bigger than Earth.

Would we demote ourselves? /phpBB/images/smiles/icon_smile.gif

chivis
2003-Feb-26, 03:40 PM
On 2003-02-26 10:09, Kaptain K wrote:

OK...Then how can we be sure that there isnt any bigger or denser comets then our own moon?

Because, if it were bigger and denser than our moon, it would be a planet.



Wow...thats scientific!

chivis
2003-Feb-26, 04:07 PM
I need a density for the dust and mass spread throughout space. I couldn't find one so I assumed that 99% (probably low) of the solar system's mass is contained in the sun an planets within pluto's orbit. That gives a density for the 'empty space' of 2.31E-11 kg/m^3


For one, I think this assuption is flawed. I'll agree that there isnt much dust and mass in free space left now...This is not a young stystem. What about earlier on, there was certainly a lot more matter floating around then.

A comet back in those days would be living in a whole different environment with new variables.

Am I totally out to lunch?

~Chivis

RichField
2003-Feb-26, 04:39 PM
On 2003-02-26 10:36, kilopi wrote:
That does seem high. It's only 10^10 less than normal Earth air at sea level, no?

Having looked that up this moring, that seems about right wrt air. That being the case I'm satisfied that it was an upper bound and don't see a need to repeat the calc.



On 2003-02-26 11:07, Chivis wrote:
For one, I think this assuption is flawed. I'll agree that there isnt much dust and mass in free space left now...This is not a young stystem. What about earlier on, there was certainly a lot more matter floating around then.

A comet back in those days would be living in a whole different environment with new variables.

Am I totally out to lunch?

I see two issues here that really don't change the results.
First, even if the mass was more spread out most of it probably went to the known large bodies in the system. You'd still need an awful lot of mass out there to make much difference. As kilopi pointed out, my assumption probably was flawed, to the high side. Now we'd have even more OoM to make up and it's linearly dependent, to get up around 10^22 kg we'd need a 7 OoM increase in density. That seems pretty thick for space. Actually, looking back at my calculations: The mass of the solar system distributed spherically out to pluto is only 2.308E-9 kg/m^3. Remember, I took 1% of that and distributed it, which I also think is an extremely generous estimate.

Second, if it got that big that long ago, I would estimate we're now talking bilions of years. Let's say 100 milion years as a minimum. That means it passes by the sun at least 2700 times where it is losing mass with less mass to pick up on the rest of its trip.

I'm not commenting on the possibility that there are large objects a long distance from us that we don't know about yet. And I'm not even attempting to get into how things would form early on. I'm trying to demonstrate that there isn't much left for something like that to pick up.

Rich

darkhunter
2003-Feb-26, 07:18 PM
If pluto were somehow pushed into a cometary orbit, would it be a really big comet?

Comets are just big, dirty snowballs--do we know enough about Pluto to know if I've weven asked a logical question?

chivis
2003-Feb-26, 08:40 PM
Actually, looking back at my calculations: The mass of the solar system distributed spherically out to pluto is only 2.308E-9 kg/m^3. Remember, I took 1% of that and distributed it, which I also think is an extremely generous estimate.


OK...before I go any further...I need someone to answer this...How far would a comet such as C/2002 V1 with a 37,000 year orbit travel outward from our sun into the Kuiper Belt or Oort Cloud? Where would the comet be at that time?

~Chivis

Kaptain K
2003-Feb-27, 06:19 PM
OK...before I go any further...I need someone to answer this...How far would a comet such as C/2002 V1 with a 37,000 year orbit travel outward from our sun into the Kuiper Belt or Oort Cloud? Where would the comet be at that time?

The aphelion distance is a little over 2,000 AU or 320 billion kilometers. This is approximately 50 times the distance of Pluto. Definitely in the Kuiper belt, but not in the Oort cloud.


On 2003-02-26 10:09, Kaptain K wrote:
Quote:

OK...Then how can we be sure that there isnt any bigger or denser comets then our own moon?
---------------------------------------------

Because, if it were bigger and denser than our moon, it would be a planet.
---------------------------------------------

Wow...thats scientific!


Actually, it is scientific. Comets, because of their low mass, have shallow gravity wells. because of this, gas and dust that is boiled off by radiation is lost and becomes the huge coma and long tail that we associate with comets. Planets, being massive and dense, have deep and steep gravity wells and do not lose their volatiles to space. The Earth and Venus are well within the perihelion of many comets, but neither has a coma or tail.

_________________
"There's a whole lotta things I've never done, but I ain't never had too much fun."
Commander Cody and the Lost Planet Airmen

<font size=-1>[ This Message was edited by: Kaptain K on 2003-02-27 13:22 ]</font>

RichField
2003-Feb-27, 09:11 PM
On 2003-02-27 13:19, Kaptain K wrote:

OK...before I go any further...I need someone to answer this...How far would a comet such as C/2002 V1 with a 37,000 year orbit travel outward from our sun into the Kuiper Belt or Oort Cloud? Where would the comet be at that time?

The aphelion distance is a little over 2,000 AU or 320 billion kilometers. This is approximately 50 times the distance of Pluto. Definitely in the Kuiper belt, but not in the Oort cloud.


Thanks, the 2,000 AU agrees with the number I have. I wasn't sure what Chivis meant when he asked where it was. Numbers I found have the Kuiper Belt from 20 to 100 AU but didn't really say where the Oort cloud began, (Kaptain, do you have numbers for this?) only that it likely extends well beyond 50,000 to 100,000 AU. Even then, I wasn't sure if Chivis was asking in what is it located or where in some coordinate system it would be positioned.

Also, I was able to find space density estimates from 5 to 100 particles/cm^3. That's much less than my original assumption.

Rich

zwi
2003-Feb-28, 01:07 AM
People have been dissing other people about the size of comets, and the significance of their appearance

Let me tell you a story from my youth. When I was in sixth grade the teacher told us that an asteroid called Eros was very close to the Earth, and that we would actually be traveling through the tail of a comet whose name at this time escapes me It was about 1936

They told us these events would be harmless and that superstitious people would be worried and take them for portents

So my friends and I were not at all worried

And guess what? Along came World War 2. Was that purely a coincidence?

If people had worried at that time, could not WW2 and the Holocaust have been avoided?

Dont you think that the comet's tail may have affected Neville Chamberlain, W Churchill and F Roosevelt?

Non-serious answers only please

Zwi

Zwi

chivis
2003-Feb-28, 03:39 AM
[quote]
On 2003-02-27 13:19, Kaptain K wrote:
The aphelion distance is a little over 2,000 AU or 320 billion kilometers. This is approximately 50 times the distance of Pluto. Definitely in the Kuiper belt, but not in the Oort cloud.

[quote]

Ok...so it would basically take light about 7.5 days to get there right?

Thats a really long trip through space...you guys cant really say for sure what a comet travels through in its orbit...Pluto is a KBA and I'm sure its not the only one out there...some probably bigger....Hey, heres a concept! Maybe Pluto is a dead comet...isnt that a big snowball too? The possiblity of a bigger, denser and badder comet is definately possible.

My eyes tell me that NEAT is hell of a lot bigger then some people claim. I have to agree with James McCanney on this one...

listen for yourself...http://mysteriesofthemind.com/ he's on right now....10:30pm eastern Feb 27

Lexx_Luthor
2003-Feb-28, 05:27 AM
Tunguska. I would imagine if they wanted to, comets could end wars better than they could cause them. /phpBB/images/smiles/icon_biggrin.gif

1936
Wasn't that about the time of the Jap invasion of China?

Spanish Civil War???

Mainframes
2003-Feb-28, 11:27 AM
On 2003-02-27 13:19, Kaptain K wrote:

The Earth and Venus are well within the perihelion of many comets, but neither has a coma or tail.



You could say that Earth and venus do have comas, we just redefine them as atmospheres, because the coma is held close to the planet by it's steep gravity well.

nebularain
2003-Feb-28, 12:45 PM
Now that you mention it, I was just at a program for teachers at the MD Science Center which subject matter was Auroras, and our speaker showed us a diagram of the Earth's magnetic shpere, and it is coma-and-tail shaped (the tail goes out pretty far, too
).

Kaptain K
2003-Feb-28, 01:08 PM
Numbers I found have the Kuiper Belt from 20 to 100 AU but didn't really say where the Oort cloud began, (Kaptain, do you have numbers for this?) only that it likely extends well beyond 50,000 to 100,000 AU.
I too am having trouble finding definitive numbers (maybe, because there are none /phpBB/images/smiles/icon_smile.gif ). 20 AU is definitely out as an inner edge of the Kuiper belt, since Neptune is 30 AU from the Sun. So, figure 30-40 AU as the inner edge. As for the outer bounds of the Kuiper belt, I have seen anywhere from 100 to a couple of thousand AU. The boundaries of the Oort cloud are as vague (if not more so). I have seen numbers for the inner boundary from 100 to 10,000 AU. It may extend as far as three light-years.

Edited for typos.

_________________
"There's a whole lotta things I've never done, but I ain't never had too much fun."
Commander Cody and the Lost Planet Airmen

<font size=-1>[ This Message was edited by: Kaptain K on 2003-02-28 08:15 ]</font>

Anonymous
2003-Feb-28, 05:07 PM
chivas.


“I'm sorry but I have a VERY hard time believing that comet are simply "dirty snowballs". There has to be more to it then that.”


Fortunately, you don’t have to take anyone’s word on this. The body of established fact on the subject is rather extensive. In 1985-1986, several countries launched a flotilla of spacecraft to fly-by Halley’s Comet. The Soviet Union sent two probes (Vega 1 + Vega 2), Japan sent two probes (Sakigake and Suisei), and the European Space Agency sent one probe (Giotto).


As each probe flew by the comet, the gravitational influence of the comet changed the path of each probe. This alteration of the probes flight paths was confirmed by the slight changes in the travel time of the radio signals being beamed to Earth. From this information, the researchers could deduce a ballpark figure for the mass of Halley’s Comet. This is only half the picture. Now we need to know the physical dimensions of the comet to work out the density. Thousands of photographs were taken to assist in answering just this question. Here’s one of the more popular pictures:

http://www.imagesofspace.com/images/Halley's%20Comet%20400.JPG

Here is a map of Halley’s Comet;

http://www.solarviews.com/raw/comet/halmap.gif

Note; because a comet’s surface is changing a great deal when it is close to the Sun (inside the orbit of Jupiter) the map is no longer current, but is a fair rendition of what it looked like at the time.

Here is a link displaying the basic findings on the size, shape, mass and density of Halley’s Comet.

http://itss.raytheon.com/cafe/qadir/q918.html

So, Halley’s Comet is mostly ice(s) with some dust tossed into the mix. Hence the phrase “dirty snowball”.


“Where do comets originate?”


The majority of comets have been observed entering the inner solar system from beyond the orbit of Neptune. In plain language, I guess we would say the “boondocks” of the solar system is where comets originate. No comet has ever been observed to be ejected by the sun. To the contrary; every comet we’ve observed which came close to the sun was destroyed completely or disrupted beyond recognition.


“There must be a reoccuring event that "refreshes" our planet. You can't dispute the evidence to support this. (ie Ice Ages, Pole Shifts, Great Floods, lost civilizations)”

There have been a number of severe ice ages, but I would describe the effects more like a “cull” rather than“refreshment”. Ice ages take decades, even centuries to set in. Most animals simply migrate to warmer latitudes. The few remaining either adapt to the cold (Wooly Mammoth, Wooly Rhino) or die out.

A great flood is a relative concept. If you only know of a few thousand humans and see them all die, you may write that “everybody died”. This would be an accurate account from your point of view but would over look the fact that there were millions of humans that you did not know about. The geologic record is fairly clear on this. Although there is evidence of periodic, regional floods, there is no evidence of widespread, global flooding. So, only small portions of the Earth could be refreshed in this manner.

As for lost civilizations, some are conquered and assimilated by the victors while others simply stagnate and die out or disperse. This leaves pole shifts. There is no evidence for such an event, if you mean what I think you mean. The crust of the Earth sliding around on the mantle would leave behind some form of evidence. There is direct evidence that this has not occurred recently; Hawaii. The chain of islands we call Hawaii is the result of hot-spot volcanism. The crust slowly migrated over the hot-spot allowing volcanoes to form over the hot-spot. But we don’t call this gradual migration pole shifting; we call it “plate tectonics”. The migration of the continents riding on the tectonic plates.

sarongsong
2003-Mar-01, 09:44 AM
Curious source classification:
Observable Comets -- from the Harvard Minor Planet Center
http://spaceweather.com/
(under Essential Web Links)
Could those Harvard "lefties" (Yale "righties") be on to something?

sarongsong
2003-Apr-24, 03:11 AM
This Web site is for those who do not believe that comets are dirty snow balls:
" ... Comet Neat had a planet sized nucleus and was a very powerful energetic comet ... "
http://www.jmccanneyscience.com/