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Is the universe infinite? 
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#73
Feb2612, 03:07 AM

P: 11

The question was "Is the universe infinite". I think we agree that it is not infinite. The mass and energy is limited by the fixed amounts produced in the big bang. Mass and energy reduce by enthalpy increases but change among each other as Dark Matter, Galaxies and black holes are formed. Energy is conserved as the Universe as it expands but entropy reduces it and thus mass also. 


#74
Feb2612, 03:12 AM

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There's also no reason to believe that the universe was ever finite. It may be finite, it may be infinite. We just don't know. 


#75
Feb2612, 08:58 AM

P: 11

You say, "Why did you repeat it?" . ...I didn't repeat anything. I did try to help you along and pointed to the thread theam. ... but alas you seem to avoid the question by skirting the premis if the Big Bang spewed out an infinate amount of mass and energy or not. ..... brerabbit 


#76
Feb2612, 09:56 AM

P: 59




#77
Feb2612, 10:13 AM

P: 59




#78
Feb2612, 10:21 AM

P: 2

there has to be equation for why the universe has a end...it has to and lets all agree that the univese is expanding at whatever speed what is it expanding into hummm



#79
Feb2612, 10:33 AM

P: 59

As to your final question...the Universe isn't expanding into anything. Expansion of the Universe (and its global geometry) are intrinsic properties of the Universe, itself. Just as there is no "center" to the Universe, there is no "edge". 


#80
Feb2612, 11:17 AM

P: 2

that we know off..... or is it so big that nobody has an explanation so the attach to word like infanity isnt that another word for we dont no the number so big the space so large....bringing it back down to my level....it just seems to me that something has to be in something now that my go on forever ,,,,just cant wrap my brain around that



#81
Feb2612, 11:27 AM

P: 11

The Universe or possibly the many Universes each with its own Big Bang all reside in Space at the same time. IMHO, Space is quite different, and can be finite and both expands and contracts. Energy is conserved but degrades as Entropy within the Black Holes dominate. http://arxiv.org/abs/0801.1847 


#82
Feb2612, 11:30 AM

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#83
Feb2612, 12:10 PM

P: 11

brer 


#84
Feb2612, 01:23 PM

P: 59

Question: If a photon is redshifted due to the Cosmological expansion of space, it loses energy. Where does the energy go? Answer: It doesn't go anywhere...because in expanding space, energy is not conserved. 


#85
Feb2612, 02:38 PM

P: 11

brer 


#86
Feb2612, 02:43 PM

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#87
Feb2612, 03:07 PM

P: 59

But as a possible correction, do not confuse a doppler redshift (which IS a measure of relative velocity between two objects in space), and Cosmological RedShift, which is NOT a measure of relative velocity, but is a result of the expansion of space itself. They are goverened by two very different formulas/equations. 


#88
Feb2612, 05:37 PM

P: 1

I have read that, if the universe is flat or hyperbolically curved, then it must be infinite. I've also read that all observations to date suggest that the universe is flat. Would that make it infinite? If it is indeed flat, then to be finite, it would have to have an edge and this would seem to contradict quite a few well accepted ideas in cosmology. If the universe is infinite now, then, looking back towards the big bang, it must always have been infinite  you can never halve the size of an infinite object and make it finite. It seems to a simple mind like mine, therefore, that the big bang didn't start with an infinitely small infinitely dense single point, but with an infinitely large infinitely dense affair. Is there any reason why that can't be the case? It would mean of course that the universe isn't actually getting bigger  it's just spreading out.



#89
Feb2612, 07:33 PM

Sci Advisor
P: 4,836

1. Even if the universe is flat, it can still be finite as it is entirely possible for a flat universe to wrap back on itself. An example of this type of universe is displayed in the old arcade game Asteroids, which is entirely flat, but move the ship off one side of the screen and it appears on the other. This is known as a toroidal topology, and it is entirely possible for our universe to be flat and finite in this way. I'm reasonably sure that you can do similar things with a negativelycurved spacetime as well. 2. Unfortunately, our vision is limited both in time and space. We cannot observe the whole of the universe. And in practice, our local, observable region can easily have a curvature that deviates somewhat from the average curvature of the universe. So measuring some curvature or no curvature actually doesn't say much of anything about the curvature of the universe as a whole: the curvature we measure could just be a local feature. However, let me just end with a little statement. As far as we know, our universe will expand forever into the future. This means that at least in one dimension, our universe is infinite: the time dimension. So if our universe is infinite in one dimension, why can't it be infinite in the other dimensions as well? 


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