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The Universe theories


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#1    Ghostboo

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Posted 27 September 2002 - 12:02 AM

The open Universe theory states that after the Big Bang,(For those who believe in that)the Universe started expanding forever and will never stop.
The closed Universe theory states that after the Big Bang,the Universe will expand until gravity reaches its limit(if there is one)and everything will be forced back to the middle of space again and fuze into one thing.Therefore awaiting yet another Big Bang.

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#2    Pale_Horse

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Posted 27 September 2002 - 12:27 AM

I say open.  But what I want to know is, if you are at the "edge" of the continuing expansion, with the universe behind you, what is in front of you?  In other words, what is the universe expanding into?  Is it pushing something else out of the way or what?  Man, makes me nausous to think about infinity! :s5  

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Guess you could say we've always been red, white and blue.


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#3    Saru

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Posted 27 September 2002 - 12:16 PM

The answer to this question relies on whether the mean density of matter in the universe is greater or lower than the "Critical Density". If the matter in the universe has a lower mean density than the critical density, then it will continue to expand indefinately - an open universe. This would actual result in our universe undergoing "Heat Death" after a very long time, once all the stars in the universe have burned out, and all the materials required for star formation have been used up.

If however, the mean density of the matter in the universe is greater than the critical density, then gravity will halt the universe's expansion, and it will contract, resulting in a "Big Crunch".

Visible matter in the universe accounts for only about 20% of the critical density, however it is widely believed that a great deal more exists in the form of dark matter. If this were true, the actual density of the universe would be very close indeed to the critical density.

We will have to wait until more concrete methods for measuring and detecting dark matter become available, before the ultimate fate of our universe will be known for sure.

:sk


#4    Bizarro

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Posted 28 September 2002 - 11:07 AM

i say closed.  i also believe that we are relative to everything, so even when the universe contracts we will never notice it at all.  

if there was a meteor,
adrift amongst space,
set about on a collision course
not with Earth, but my face...
i wonder if id even know,
at what time i might,
be passed off like an old style
and by the meteor be smite?

- me, 1997

#5    Homer

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Posted 28 September 2002 - 07:39 PM

To answer the original question, I believe the universe will expand forever. I say that only because the expansion of the universe is still accelerating, and by the time the acceleration stops(if it stops), the distances might be too great to contract. Without further information on dark matter, that's my position at this time(always subject to change as new evidense presents itself ;D)

DScwartz,
Everything is relative to everything else in the cosmos as it relates to space/time. The reason we won't notice the Big Crunch is because we will all be dead. The earth and the sun will both be dead, so of course we won't notice.

SaRuMaN,
It will be interesting to know if neutrinos have matter. Neutrinos are so numerous that even if their mass is only trace, it could answer a lot of questions about dark matter. Of course, if they do have mass, then the laws of physics will not only have a new chapter, but may have to be tweaked here and there to fit this exotic property of mass into the laws of known physics. Dark Matter against Dark Energy...which will prevail?

Pale_Horse,
I know what you mean. It's difficult to fathom nothingness. According to the theory, before the Big Bang, there was nothing. No time, no space. Just nothing. Even empty space is something, I guess. Is space that is void of all matter, such as a vacuum, subject to time? Although I contemplate it from time to time, it is beyond my comprehension.

Which leads me to this, is a vacuum void of all matter? Or does it have so little matter, that it has no gravitational influence? If space and time are related, and if a vacuum can be void of all matter, would there be time in the vacuum? If time requires matter to be present, does it matter how much matter? If there was a vacuum the size of the Grand Canyon, which had one atom in it, would it be considered a vacuum? Would it be subjected to time? :s9

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#6    Kismit

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Posted 29 September 2002 - 01:27 AM

Stephen Hawkins has a theory that when the Universe finally contracts time will actually appear to move backwards, I should think it would be an interesting thing to experience.
(as Mr Hawkins appears to be one of the greatest minds of our time I,m going with the closed universe theory) :sq


#7    Bizarro

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Posted 29 September 2002 - 04:34 AM

Is space that is void of all matter, such as a vacuum, subject to time? Although I contemplate it from time to time, it is beyond my comprehension- Homer.

i am astonished this could be beyond your comprehension, Homer.  after all, you seem to speak with such authority on these matters, as if you knew what you say to be an absolute certainty.  

please tell me how you know we will all be dead when the big crunch comes?  it could come tomorrow afternoon at 4:33:32 EST for all you know.  im glad you could enlighten us all with your omniscient knowledge of the ways of the cosmos.  maybe someone will take your words down for posterity's sake...

if there was a meteor,
adrift amongst space,
set about on a collision course
not with Earth, but my face...
i wonder if id even know,
at what time i might,
be passed off like an old style
and by the meteor be smite?

- me, 1997

#8    Homer

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Posted 29 September 2002 - 05:38 AM

DSchwartz,  
I speak with authority on either the things that I know to be true, or of things that are true in accordance with the current laws of astrophysics.  
 
If you point a gun straight up and shoot, will the time it takes the bullet to reach it's highest point be greater than or less than the time it takes for gravity to bring it back to the same level from which it was fired? Keep in mind gravity is the only force to bring it back, and gravity will be the only force to contract the universe as well. That being said, the universe has been expanding for about 15 billion years(give or take a few months ;D), and would be a mathematical impossibility for the crunch to happen in earths lifetime, much less tomorrow.  Of course I know you know this, and would rather put me to some test instead of answer a single question I asked.    
 
 
Kismit,  
Can you give more information on Hawking's theory? And what was it about the thoery that either impressed you or you found most believable?  

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#9    Loonboy

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Posted 29 September 2002 - 12:22 PM

[blue] :s2 <--- I'm laughing because although I took offence at Dschwartz's words to our good friend Homer, I realised that the total arrogance directed at him is supposed to be Dschwartz's attempt at 'humour'...
[/blue]
:s9


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#10    Kismit

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Posted 29 September 2002 - 01:15 PM

Homer it would be a pleasure ,
I,t was a late night documentary called "Hawkings theories of or on the Universe" What Impressed me the most was the fact that he believed time would move backward when the Universe contracts unfortunately my meager I.Q didn't grasp a lot of the facts and I am certainly  not going to claim that I have any kind of grip on the Idea's of dark matter density's , but I'll check to see if I can find a site with the Info on it and attempt to post a link. :sq


#11    Kismit

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Posted 29 September 2002 - 01:35 PM

Here goes fingers crossedhttp://www.pbs.org/wnet/hawking/universes/html/univ.html


#12    Homer

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Posted 29 September 2002 - 08:49 PM

Thank you Kismit,
I seen that one before but didn't know if there was another more recent. Hawkings theory about the "no boundary universe" is very interesting. Using imaginary time, the theory states that the universe didn't begin with a singularity at all.

Thanks again Kismit  :)

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#13    Bizarro

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Posted 30 September 2002 - 05:43 AM

oh yes, the almighty 'current laws of astrophysics'.  just the fact that you say they are 'current' and not just the 'laws of astrophysics' proves my point exactly.  in 2002, we  happen to be at the peak of our understanding of astrophysics also, considering we all spend so much time in space studying it.  those laws couldnt possibly be wrong now could they?  when i made my statement about why i think we live in a closed universe i said 'i believe' and not 'i know' for precisely this reason.  i am glad you can be so confident that you feel you can put my belief down as wrong and your's as correct.  

please don't think you can belittle my statements at will, Homer.  i don't happen to ascribe to the belief that you have a superior intellect, as much as you wish i would.  

as for your little analogy of firing a gun up into the air, you are assuming that the universe follows the same rules of gravity that we experience on the earth.  how do you know the universe is affected by gravity?  you can't even prove it is expanding, much less that it will compress upon itself due to gravity.  also, you want me to answer a hypothetical question about a bullet where you rule out all the other possible influences on the bullet besides gravity alone?  is that reality, Homer?  i think not.  the fact that we do not live in a vacuum would affect the bullet, and as far as we understand the nature of the universe i see us as being in no position to make authoritative claims on anything.  you're an arrogant fool, Homer.   its one of the best types of fools to be, in comparison to say a bumbling fool or a jumping fool (who wants to be a jumping fool anyways?), but youre still a fool. :)

if there was a meteor,
adrift amongst space,
set about on a collision course
not with Earth, but my face...
i wonder if id even know,
at what time i might,
be passed off like an old style
and by the meteor be smite?

- me, 1997

#14    Homer

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Posted 30 September 2002 - 07:54 AM

DScwartz stated "oh yes, the almighty 'current laws of astrophysics'.  just the fact that you say they are 'current' and not just the 'laws of astrophysics' proves my point exactly.  in 2002, we  happen to be at the peak of our understanding of astrophysics also, considering we all spend so much time in space studying it.  those laws couldnt possibly be wrong now could they?"  You speak as if I have something to do with those laws. The laws are based on what we know about the physical properties of the universe based on experiments and instruments. But there are exotic materials in the universe that we know nothing about. Take my neutrino example. They are particles that pass through matter as if it wasn't there. Neutrinos from the sun pass right through the earth as if earth wasn't even there. It's not known for sure exactly what they are or if they are even made up of matter. That discovery could be very profound. The believed date of the universe has changed only this year. Does that mean it's an absolute certainly? Of course not, but it's using current evidence. Granted the laws didn't change with that discovery because it didn't change what we know about the physical properties, but it's still an important discovery in terms of how much expansion the universe has had.

You also stated "when i made my statement about why i think we live in a closed universe i said 'i believe' and not 'i know' for precisely this reason.  i am glad you can be so confident that you feel you can put my belief down as wrong and your's as correct"   I never put your belief about a closed universe down. In fact I myself stated that "I believe" and that my belief was subject to change when further evidence presents itself. So the reality is, that I didn't put down or disagree in anyway anything you said in your first post.

You also stated "how do you know the universe is affected by gravity?  you can't even prove it is expanding, much less that it will compress upon itself due to gravity."    Everything in the universe is affected by gravity. Everything. It has been PROVEN that the universe is expanding. Nobody can prove or disprove the universe won't compress upon itself, and I never stated the universe will compress upon itself due to gravity. What I stated was that if the universe does compress, it will be because of gravity. If you remember, my original reply was an open universe, meaning I don't believe the universe will compress.

So you have yet to prove me a fool, and I stand by everything that I have said. But I'm curious as to why you feel the need to insult me and challenge me.  

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#15    Bizarro

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Posted 30 September 2002 - 10:22 AM

i also believe that we are relative to everything, so even when the universe contracts we will never notice it at all. -DSchwartz

Everything is relative to everything else in the cosmos as it relates to space/time. The reason we won't notice the Big Crunch is because we will all be dead. The earth and the sun will both be dead, so of course we won't notice. -Homer


you sound an awful lot like a know-it-all to me here.  will you stop arguing now?  tossing around big words like neutrinos isnt making you sound any less a fool, btw.  im glad you felt like telling me what a neutrino was, since  im such an idiot i wouldnt know.  OMG, they can pass through the earth?  how is that possible?  OMG, that's amazing, Homer, thank you...

if there was a meteor,
adrift amongst space,
set about on a collision course
not with Earth, but my face...
i wonder if id even know,
at what time i might,
be passed off like an old style
and by the meteor be smite?

- me, 1997




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