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Offline andy054

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Why is there a universe?
« on: 24/01/2009 18:15:26 »
Why is there a universe?

If there was a big bang, what came before it, and before that, and so on?

Surly nothing should be, but it is, why?   


 

Offline Vern

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Why is there a universe?
« Reply #1 on: 24/01/2009 19:16:04 »
I am one of those who suspect there was no Big Bang; so for me the universe always existed. As to why it exists; who knows, but if it didn't exist we wouldn't be here to ponder over it. :o :o
 

Offline Bored chemist

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Why is there a universe?
« Reply #2 on: 24/01/2009 19:41:14 »
Vern,
It gets dark at night.
That may not seem a very important observation but it proves that the universe is in some way finite.
If it were not then, along any given line that you might look along at night, there would be a star.
The ideea that the universe is always here and always has been can be ruled out every time the sun sets.
 

Offline Vern

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Why is there a universe?
« Reply #3 on: 24/01/2009 20:11:49 »
Vern,
It gets dark at night.
That may not seem a very important observation but it proves that the universe is in some way finite.
If it were not then, along any given line that you might look along at night, there would be a star.
The ideea that the universe is always here and always has been can be ruled out every time the sun sets.
That is true only if you consider light to be ageless. The tired light scheme has light continuously converting to mass. When starlight contributes to the temperature of space debris it becomes less energetic eventually being completely consumed.
 

Offline angst

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Why is there a universe?
« Reply #4 on: 26/01/2009 22:57:13 »
Vern,
It gets dark at night.
That may not seem a very important observation but it proves that the universe is in some way finite.
If it were not then, along any given line that you might look along at night, there would be a star.
The ideea that the universe is always here and always has been can be ruled out every time the sun sets.

You had me thinking there....but this is not necessarily true. Light gets bent, light gets blocked out, our own atmosphere filters out great swathes of starlight. Not to mention that if mere streetlighting can so adversely affect the amount of light we perceive from beyond their range, that closer stars and galaxies might equally be seen to do likewise.

(this isn't an argument that the universe is infinite because of that, merely that the point - though initially compelling - doesn't necessarily stand up to scrutiny.  :))
« Last Edit: 26/01/2009 22:59:58 by angst »
 

Offline Soul Surfer

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Why is there a universe?
« Reply #5 on: 31/01/2009 00:21:36 »
Olbers paradox requiring the universe to be in some way limited in space or time only applies to our observable universe.  there is absolutely no reason why that represents the entire universe.
 

Offline Vern

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« Reply #6 on: 31/01/2009 16:21:14 »
Olbers paradox requiring the universe to be in some way limited in space or time only applies to our observable universe.  there is absolutely no reason why that represents the entire universe.
I feel the same way. But the argument that is hard to dispose of is the red shift which, if it represents the speed of receding galaxies, would place everything in the same place some time in the past.
 

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Why is there a universe?
« Reply #7 on: 31/01/2009 18:43:11 »
It gets dark at night.
That may not seem a very important observation but it proves that the universe is in some way finite.
If it were not then, along any given line that you might look along at night, there would be a star.

Finite or expanding or both.
Olber's Paradox is not really a paradox any more because we don't have to believe that the Universe is ageless.


You had me thinking there....but this is not necessarily true. Light gets bent, light gets blocked out, our own atmosphere filters out great swathes of starlight. Not to mention that if mere streetlighting can so adversely affect the amount of light we perceive from beyond their range, that closer stars and galaxies might equally be seen to do likewise.

This is actually a red herring because if the energy didn't reach us it would be heating up the dust etc.  in between until it was white hot and we'd still end up with an infinitely bright sky if that were all there is to it.

 

Offline angst

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« Reply #8 on: 31/01/2009 23:41:20 »


You had me thinking there....but this is not necessarily true. Light gets bent, light gets blocked out, our own atmosphere filters out great swathes of starlight. Not to mention that if mere streetlighting can so adversely affect the amount of light we perceive from beyond their range, that closer stars and galaxies might equally be seen to do likewise.

This is actually a red herring because if the energy didn't reach us it would be heating up the dust etc.  in between until it was white hot and we'd still end up with an infinitely bright sky if that were all there is to it.


I'd suggest that that is a red herring, for there would be infinite space within which to dissipate that energy. You are placing the limits of the finite upon the infinite.
 

Offline Vern

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« Reply #9 on: 01/02/2009 01:27:12 »
Quote
This is actually a red herring because if the energy didn't reach us it would be heating up the dust etc.  in between until it was white hot and we'd still end up with an infinitely bright sky if that were all there is to it.
Actually if you do the arithmetic it comes out to about 4 degrees K. I think it was Sir Arthur Stanley Eddington who did it.

It was some years ago that I read about this, it was before the discovery of the CMBR which was predicted back then to be in the range of 20 degrees K. Eddington postulated that starlight would warm space debris which would then radiate black body radiation at about 4 degrees K.


« Last Edit: 01/02/2009 01:54:32 by Vern »
 

Offline LeeE

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Why is there a universe?
« Reply #10 on: 01/02/2009 13:32:41 »
Why is there a universe?

Because somewhere was needed in which to put everything.

Quote
If there was a big bang, what came before it, and before that, and so on?

With the "and before that, and so on" qualifier it becomes an infinitely layered question, which I'll skip as I haven't the time to fully answer it  ;D

Quote
Surly nothing should be, but it is, why?

If it is, then it evidentially must be, so why shouldn't it be?
 

Offline Andrew K Fletcher

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Why is there a universe?
« Reply #11 on: 01/02/2009 15:24:40 »
Space is not empty. Light will collide with particles smaller than atoms and as big as planets and become spent as it travels long distances, lending people to believe the universe is finite.
Vern,
It gets dark at night.
That may not seem a very important observation but it proves that the universe is in some way finite.
If it were not then, along any given line that you might look along at night, there would be a star.
The ideea that the universe is always here and always has been can be ruled out every time the sun sets.

Vern,
It gets dark at night.
That may not seem a very important observation but it proves that the universe is in some way finite.
If it were not then, along any given line that you might look along at night, there would be a star.
The ideea that the universe is always here and always has been can be ruled out every time the sun sets.
That is true only if you consider light to be ageless. The tired light scheme has light continuously converting to mass. When starlight contributes to the temperature of space debris it becomes less energetic eventually being completely consumed.
 

Offline Andrew K Fletcher

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Why is there a universe?
« Reply #12 on: 01/02/2009 15:26:27 »
I agree Angst

Vern,
It gets dark at night.
That may not seem a very important observation but it proves that the universe is in some way finite.
If it were not then, along any given line that you might look along at night, there would be a star.
The ideea that the universe is always here and always has been can be ruled out every time the sun sets.

You had me thinking there....but this is not necessarily true. Light gets bent, light gets blocked out, our own atmosphere filters out great swathes of starlight. Not to mention that if mere streetlighting can so adversely affect the amount of light we perceive from beyond their range, that closer stars and galaxies might equally be seen to do likewise.

(this isn't an argument that the universe is infinite because of that, merely that the point - though initially compelling - doesn't necessarily stand up to scrutiny.  :))
 

Offline Vern

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Why is there a universe?
« Reply #13 on: 03/02/2009 13:30:13 »
Quote from: Andrew K Fletcher
Space is not empty. Light will collide with particles smaller than atoms and as big as planets and become spent as it travels long distances, lending people to believe the universe is finite.
Hey; I like that; we've finally found something we can agree about. :)
 

Offline DoctorBeaver

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Why is there a universe?
« Reply #14 on: 03/02/2009 17:28:43 »
Why is there a universe?

Because somewhere was needed in which to put everything.

Like an overgrown garden shed
 

Offline DoctorBeaver

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« Reply #15 on: 03/02/2009 17:31:06 »
Quote from: Andrew K Fletcher
Space is not empty. Light will collide with particles smaller than atoms and as big as planets and become spent as it travels long distances, lending people to believe the universe is finite.

Surely, it collides with particles that make up the planet, not the planet itself.
 

Offline Andrew K Fletcher

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« Reply #16 on: 03/02/2009 23:13:26 »
Thast's what I said didle I

Quote from: Andrew K Fletcher
Space is not empty. Light will collide with particles smaller than atoms and as big as planets and become spent as it travels long distances, lending people to believe the universe is finite.

Surely, it collides with particles that make up the planet, not the planet itself.
 

lyner

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« Reply #17 on: 04/02/2009 23:42:46 »
Angst / Vern
The Olber Paradox is not resolved on the grounds of dust and gas in between*. It is only resolved by, either a finite or expanding situation. That's what I meant by a red herring. As soon as you accept that light energy reaching us from distant stars is less and less OR that there are no stars beyond a certain distance, the paradox disappears.

* In an infinite Universe, each grain of dust would be receiving energy from all directions from stars and would heat up to the same temperature as the average star - thermal equilibrium would be reached. The dust would appear white hot to us.
« Last Edit: 05/02/2009 15:26:41 by sophiecentaur »
 

Offline Vern

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« Reply #18 on: 05/02/2009 00:50:59 »
I think that if light loses energy to mass as it ages the paradox will also go away. Maybe someone has detailed the math to show the paradox; I have never seen the math to see what their given values are. We might find a problem with the given values.
 

lyner

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« Reply #19 on: 05/02/2009 09:56:06 »
I think that if light loses energy to mass as it ages the paradox will also go away. Maybe someone has detailed the math to show the paradox; I have never seen the math to see what their given values are. We might find a problem with the given values.
I don't see that this can be correct. After a long enough period, the 'mass' to which you refer will reach a temperature at which it radiates as much power as it receives; it will reach thermal equilibrium by being at the same temperature as the sources surrounding it. Each speck of mass will glow like a star - filling in the gap / shadow which it presented when it was first introduced.
 

Offline Vern

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« Reply #20 on: 06/02/2009 03:33:48 »
Yes; it will radiate as much power as it receives; it is continually doing this; its radiating ability is not cumulative since it radiates constantly. So it simply radiates at the temperature of ambient space.  This is as Eddington postulated.
 

Offline LeeE

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« Reply #21 on: 06/02/2009 11:31:17 »
Why is there a universe?

Because somewhere was needed in which to put everything.

Like an overgrown garden shed

Yes, or a loft.
 

Offline angst

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« Reply #22 on: 07/02/2009 00:42:54 »
Angst / Vern
The Olber Paradox is not resolved on the grounds of dust and gas in between*. It is only resolved by, either a finite or expanding situation. That's what I meant by a red herring. As soon as you accept that light energy reaching us from distant stars is less and less OR that there are no stars beyond a certain distance, the paradox disappears.

* In an infinite Universe, each grain of dust would be receiving energy from all directions from stars and would heat up to the same temperature as the average star - thermal equilibrium would be reached. The dust would appear white hot to us.

This makes no sense. If the universe is finite, and we say that we measure that finite value and call it U. A universe that is 2U would not be hotter or brighter at any given location - unless you suggest otherwise? A universe 4U would, likewise, not be hotter or brighter at any given location. Extrapolate onward....
 

lyner

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« Reply #23 on: 07/02/2009 17:25:25 »
Are you just asserting that or have you a proof?
Where is the error in the following?

If the Universe is finite, there will be gaps in between the stars that you see, If you make it bigger, then some of these gaps will have stars in them, providing more energy to the observer or to a piece of dust. The temperature of the dust will be high enough for thermal equilibrium -  until
energy in = energy out.
The bigger you make the Universe, the more energy arrives at your piece of dust so the temperature of the dust will be higher. For infinite size, the temperature would be the same as the stars.

If what you said were true then, with just one star and one piece of dust, the sky would be just as bright as it is at a point in our galaxy.
« Last Edit: 07/02/2009 17:27:14 by sophiecentaur »
 

Offline Vern

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« Reply #24 on: 08/02/2009 01:01:48 »
But you can't have it both ways. You can't say that the CMBR is the remnants of the Big Bang and the contribution from star light is negligible while still maintaining that starlight would cause a blazing hot universe if the universe was infinitely large.

Warmed space debris would gain energy from starlight and radiate it back into space. It could never reach the temperature of the stars. It must be a process, not a cumulative effect.

I have not crunched the numbers, but the Eddington group claimed to have done so. I don't have access to the Eddington study; and I can't produce my reference. So we may have to just agree that we disagree.  :)

« Last Edit: 08/02/2009 01:16:11 by Vern »
 

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