Is the universe infinite?


by QuantumJG
Tags: infinite, universe
brerabbit
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#73
Feb26-12, 03:07 AM
P: 11
Quote Quote by Chalnoth View Post
No, it actually isn't. Energy isn't conserved in an expanding universe, and mass can be both produced and destroyed.
thanx, Chalnoth

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.
Chalnoth
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#74
Feb26-12, 03:12 AM
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Quote Quote by brerabbit View Post
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.
Except as I pointed out, this just isn't true. Why did you repeat it?

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.
brerabbit
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#75
Feb26-12, 08:58 AM
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Quote Quote by Chalnoth View Post
Except as I pointed out, this just isn't true. Why did you repeat it?

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.
Chainoth:

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
Deuterium2H
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#76
Feb26-12, 09:56 AM
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Quote Quote by brerabbit View Post
Chainoth:

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
Chalnoth is correct. Energy is NOT conserved in an expanding Universe. Space can be both infinite and expanding.
Deuterium2H
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#77
Feb26-12, 10:13 AM
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Quote Quote by Radrook View Post

Even this very large number would count as nothing when compared with infinity, because infinity is NOT A LARGE NUMBER be absolutely clear on this point, IT IS NOT A LARGE NUMBER, infinity is ALL THERE IS, it is NOT a number. You could keep counting (or measuring) for ever, and never reach infinity, it is only a description. Infinity describes a thing as having no end, no limit, no boundary or edge, it literally goes on FOREVER, ad infinitum.

An infinite universe for example would exist in every direction forever, there could be nothing else, ONLY the universe. It is then very easy to understand why our universe cannot be infinite, it is because it is expanding. It cannot be both infinite and expanding. It could be infinite OR expanding, but CANNOT possibly be both, that is a contradiction in terms, and we do know it is expanding. For an explanation of the Big Bang and why we know the universe is expanding.


http://www.thekeyboard.org.uk/What%20is%20infinity.htm
Radrook, the link/source you cited appears to have a rather naive (incorrect) view of the mathematical concept of infinity. Infinity is not a "number" in the sense that it is not a member of the Natural Numbers, or the Reals, for that matter. However, both Analysis and Set theory deal with infinite numbers ALL THE TIME. The extended Reals, as well as the Hyperreals and especially the Surreal Numbers include infinite (and infinitesimal) numbers. Foundationally, the first infinite ordinal number is omega (w), which is the order type of the set of Natural Numbers. All Natural numbers are finite ordinals. The first infinite ordinal number "w" is followed by w+1, w+2,...w+n = w x 2,...w x 3,...w^2, etc. In fact, there is an uncountable number of "countably" infinite ordinals before we reach the first "uncountable" infinite ordinal (w1).
laaylowww2
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#78
Feb26-12, 10:21 AM
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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
Deuterium2H
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#79
Feb26-12, 10:33 AM
P: 59
Quote Quote by laaylowww2 View Post
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
There is an equation (FLRW metric), and when it includes a cosmological constant term, which fits within observational parameters, yields a homogeous, isotropic Universe that is accelerating in it's expansion.

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".
laaylowww2
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#80
Feb26-12, 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
brerabbit
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#81
Feb26-12, 11:27 AM
P: 11
Quote Quote by Deuterium2H View Post
Chalnoth is correct. Energy is NOT conserved in an expanding Universe. Space can be both infinite and expanding.
thanx, deuterium

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
Chalnoth
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#82
Feb26-12, 11:30 AM
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Quote Quote by brerabbit View Post
thanx, deuterium

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
Please read this before continuing:
http://math.ucr.edu/home/baez/physic...energy_gr.html
brerabbit
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#83
Feb26-12, 12:10 PM
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Quote Quote by Chalnoth View Post
Please read this before continuing:
http://math.ucr.edu/home/baez/physic...energy_gr.html
Will do, thanx. Would you give us the URL s on the sciences and academic credentials that they have in astro sciences, I can't find any other than Baez is a mathematician in Riverside and has an interest in protesting as did his relatives.

brer
Deuterium2H
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#84
Feb26-12, 01:23 PM
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Quote Quote by Chalnoth View Post
Please read this before continuing:
http://math.ucr.edu/home/baez/physic...energy_gr.html
The link Chalnoth provided is excellent, and it shows that the question of "energy" and "energy conservation" is both complicated and subtle in GR. Depending on the conventions or model one chooses may yield a different answer to the question of "energy conservation", especially in a global context. The easiest (and I think the correct) interpretation is simply this:

Question: If a photon is red-shifted 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.
brerabbit
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#85
Feb26-12, 02:38 PM
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Quote Quote by Deuterium2H View Post
The link Chalnoth provided is excellent, and it shows that the question of "energy" and "energy conservation" is both complicated and subtle in GR. Depending on the conventions or model one chooses may yield a different answer to the question of "energy conservation", especially in a global context. The easiest (and I think the correct) interpretation is simply this:

Question: If a photon is red-shifted 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.
The link is only as good as its author. Red-Shift energy is a phenomena of prospective differences in velocities and wave lengths. We are discussing an atom's mass and energy after it passed thur the "Big Bang". Then looses energy due to entropy particularly in the working Black Holes. ... thus the Universe and Universes are finite.

brer
Chalnoth
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#86
Feb26-12, 02:43 PM
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Quote Quote by brerabbit View Post
The link is only as good as its author. Red-Shift energy is a phenomena of prospective differences in velocities and wave lengths. We are discussing an atom's mass and energy after it passed thur the "Big Bang". Then looses energy due to entropy particularly in the working Black Holes. ... thus the Universe and Universes are finite.

brer
This does not follow.
Deuterium2H
Deuterium2H is offline
#87
Feb26-12, 03:07 PM
P: 59
Quote Quote by brerabbit View Post
The link is only as good as its author. Red-Shift energy is a phenomena of prospective differences in velocities and wave lengths. We are discussing an atom's mass and energy after it passed thur the "Big Bang". Then looses energy due to entropy particularly in the working Black Holes. ... thus the Universe and Universes are finite.

brer
Huh?? I don't even understand what you are trying to say.

But as a possible correction, do not confuse a doppler red-shift (which IS a measure of relative velocity between two objects in space), and Cosmological Red-Shift, 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.
ilsley
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#88
Feb26-12, 05:37 PM
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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.
Chalnoth
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Feb26-12, 07:33 PM
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Quote Quote by ilsley View Post
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?
No, not quite. There are two problems with this:
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 negatively-curved space-time 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?
phinds
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#90
Feb26-12, 08:39 PM
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Quote Quote by darkside00 View Post
space is infinite, energy/matter has a maximum value
That is unsupported speculation on your part and should be stated as an opinion, not a fact.


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