# How can the cosmos be eternal?

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Hello Dear Scientists,

I kindly ask for your patience with me as Im no scientist, but I'm learning.

I have a few questions here.

Today I came across this video on the BBC:

http://www.bbc.com/earth/story/20161021-why-there-could-be-many-copies-of-you

The scientist in this documentary says that the cosmos is eternal.

But it cannot be according to basic scientific theory and understanding:

a) Matter cannot be created. It is finite. Do we agree on this, or have I misunderstood the 1st law of Conservation of matter:

According to the law of conservation of mattermatter is neither created nor destroyed, so we must have the same number and type of atoms after the chemical change as were present before the chemical change

If matter cannot be created - then there is a finite (given quantity) of matter to begin with. The Cosmos cannot be eternal because matter is not being created. If matter could continually be created, then sure, we agree - the cosmos would or could be eternal.

In fact, if I'm, not mistaken, there are scientific theories pertaining to the boundary of the universe. I.e. that the Universe is finite, and hence, the universe must have a boundary.

b) for the cosmos to be eternal, it means time would have to be eternal. We know that time cannot be eternal. Is that correct?

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Most scientists agree that the universe is about 14 billions years old, so it is not eternal.

Matter can be destroyed (converted into energy) and matter can be created (converted from energy)..

AFAIK most scientist do not believe there is a boundary of the universe,

Edited by Bufofrog

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12 minutes ago, Bufofrog said:

Most scientists agree that the universe is about 14 billions years old, so it is not eternal.

Matter can be destroyed (converted into energy) and matter can be created (converted from energy)..

AFAIK most scientist do not believe there is a boundary of the universe,

I don't think BBT precludes the universe being eternal. It just describes it emerging from a hot, dense state, which happened 14BY ago.

Edited by StringJunky

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2 minutes ago, StringJunky said:

I don't think BBT precludes the universe being eternal. It just describes it emerging from a hot, dense state, which happened 14BY ago.

Fair enough, but before the BB the universe was in a state with no matter no dimensions(?) and no decoupled forces - it is hardly what i would call a universe as we know it.  That would be like me saying I am 14 billion years old because my molecules are from the energy of the big bang, on some level you can say that is true, but I am not making a birthday cake large enough for that amount of candles.

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5 minutes ago, Bufofrog said:

Fair enough, but before the BB the universe was in a state with no matter no dimensions(?) and no decoupled forces - it is hardly what i would call a universe as we know it.  That would be like me saying I am 14 billion years old because my molecules are from the energy of the big bang, on some level you can say that is true, but I am not making a birthday cake large enough for that amount of candles.

That's what Relativity says, which is believed to be beyond its limits as one approaches T=0.

Edited by StringJunky

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49 minutes ago, Hobs said:

According to the law of conservation of mattermatter is neither created nor destroyed, so we must have the same number and type of atoms after the chemical change as were present before the chemical change

Hobs, you are correct about mass balances in most cases.  In chemistry and most processes the use of mass balances ( the goes ins = the goes outs) is a great tool for figuring out what is going on in a reaction or process.  In the case of fusion or fission you will find that the mass before the reaction does not equal the mass after the reaction.

Edited by Bufofrog

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There is no law of conservation of matter that applies over the time scale of the universe.

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15 minutes ago, Bufofrog said:

Hobs, you are correct about mass balances in most cases.  In chemistry and most processes the use of mass balances ( the goes ins = the goes outs) is a great tool for figuring out what is going on in a reaction or process.  In the case of fusion or fission you will find that the mass before the reaction does not equal the mass after the reaction.

Your way of formulating can be confusing. E = mc2 is valid universally, so also in chemical reactions. However, the mass differences are so small, that they cannot be weighed (or did I miss something?). That we notice it in nuclear reactions, as in fusion and fission, is because the strong nuclear force is so much stronger than the electromagnetic forces, which are involved in chemical reactions.

To give a simple example: a full battery is slightly (= inmeasurable) heavier then an empty one. Not because some netto outflux of particles, but because the particles of the battery 'found' an energetic lower state, and because E = mc2 the battery is slight lighter.

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27 minutes ago, Eise said:

Your way of formulating can be confusing.

IMO my explanation is much less confusing based on the level of knowledge indicated by the OP.  [Shrug]

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5 hours ago, Hobs said:

The scientist in this documentary says that the cosmos is eternal.

Eternal means existing for an infinite amount of time.

Even if the universe had a beginning (we have no evidence of that) then it could still go on existing for an infinite time n the future.

5 hours ago, Hobs said:

But it cannot be according to basic scientific theory and understanding:

a) Matter cannot be created. It is finite. Do we agree on this, or have I misunderstood the 1st law of Conservation of matter:

According to that law, whatever matter exists now must always exist so the universe must always exist and so it must be eternal.

But ... it is actually a law of conservation of matter and energy (matter can be converted to energy and vice versa).

Quote

a) Matter cannot be created. It is finite. Do we agree on this, or have I misunderstood the 1st law of Conservation of matter:

The fact that matter cannot be created or destroyed does not mean that it is finite.

If the amount of matter is currently finite, then it must always have been finite (ignoring some being converted to energy and back).

If the amount of matter is currently infinite, then it must always have been infinite.

5 hours ago, Hobs said:

In fact, if I'm, not mistaken, there are scientific theories pertaining to the boundary of the universe. I.e. that the Universe is finite, and hence, the universe must have a boundary.

Current theories say that the universe does not have a boundary. Either it is infinite or it is curved back on itself.

6 hours ago, Hobs said:

b) for the cosmos to be eternal, it means time would have to be eternal. We know that time cannot be eternal. Is that correct?

No, we don't know that.

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7 hours ago, Hobs said:

If matter cannot be created - then there is a finite (given quantity) of matter to begin with. The Cosmos cannot be eternal because matter is not being created. If matter could continually be created, then sure, we agree - the cosmos would or could be eternal.

In fact, if I'm, not mistaken, there are scientific theories pertaining to the boundary of the universe. I.e. that the Universe is finite, and hence, the universe must have a boundary.

b) for the cosmos to be eternal, it means time would have to be eternal. We know that time cannot be eternal. Is that correct?

Firstly like you I aint no scientist, but I have read plenty of stuff I believe to be reputable and based on the scientific methodology.

In actual fact, we are not sure one way or the other, whether the universe is finite or infinite.   Experiments like WMAP have shown us that the universe is topologically flat, to within very small margins of error, and on face value that tells us that in actual fact the universe is infinite. But it also does not take into account exotic geometries like torus shapes.

Worth mentioning at this time that the BB applies to the observable universe, and that as I often like mentioning, that the BB tells us that space and time [as we know them] evolved from a hot dense state, at t+10-43 seconds.

### Joseph Silk

"No. We do not know whether the Universe is finite or not. To give you an example, imagine the geometry of the Universe in two dimensions as a plane. It is flat, and a plane is normally infinite. But you can take a sheet of paper [an 'infinite' sheet of paper] and you can roll it up and make a cylinder, and you can roll the cylinder again and make a torus [like the shape of a doughnut]. The surface of the torus is also spatially flat, but it is finite. So you have two possibilities for a flat Universe: one infinite, like a plane, and one finite, like a torus, which is also flat.

Edited by beecee

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If the universe is like a torus, then it has to be very big to look flat locally.

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Based on current curvature ie the error margin. If the universe were finite and you halted expansion it would take roughly 880 billion years to arrive back at the original point of departure (treating as a finite sphere).

The LCDM model hasn't completely eliminated the possibility of a finite universe as there is that error margin.

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Confused.

Arrive back where?

The start of the Big Bang. Why 880 billion years instead of 13 billion.

Sorry if I'm being ignorant.

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33 minutes ago, Curious layman said:

Confused.

Arrive back where?

The start of the Big Bang. Why 880 billion years instead of 13 billion.

If the universe is finite, then it is curved such that if you went off in a straight line you would eventually end up back where you started. Like flying round the world; you eventually get back to the place you left.

And the very large time is because the universe is very nearly flat. So if it is curved, it is like a very large sphere that looks nearly flat (a bit like the Earth when you look around you) so it would take a long time to go all the way round.

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50 minutes ago, Mordred said:

Based on current curvature ie the error margin. If the universe were finite and you halted expansion it would take roughly 880 billion years to arrive back at the original point of departure (treating as a finite sphere).

I presume that's travelling at "c" ?

41 minutes ago, Curious layman said:

The start of the Big Bang. Why 880 billion years instead of 13 billion.

While the BB happened around 13.83 billion years ago, our observable universe is around 94 billion L/years in diameter, due to spacetime expansion over those years.

Correct

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13 hours ago, Bufofrog said:

Fair enough, but before the BB the universe was in a state with no matter no dimensions(?) and no decoupled forces - it is hardly what i would call a universe as we know it.

I'm unsure why the universe would stop being the "universe" simply because its characteristics are different than "we know it". Is there some accepted definition of the universe you are referring to that excludes what existed prior to the beginning of the BB?

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13 hours ago, Bufofrog said:

the universe was in a state with no matter no dimensions(?) and no decoupled forces - it is hardly what i would call a universe as we know it

No dimensions implies no geometry, and consequently, no time.

30 minutes ago, zapatos said:

you are referring to that excludes what existed prior to the beginning of the BB?

In which case...
What does 'prior' mean ?

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24 minutes ago, MigL said:

In which case...
What does 'prior' mean ?

When..

14 hours ago, Bufofrog said:

the universe was in a state with no matter no dimensions(?) and no decoupled forces

at a smaller time increment than...

8 hours ago, beecee said:

t+10-43 seconds.

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I don't think I was very clear, Zap.

If dimensions are lacking, i.e. a state of quantum foam, then there is no geometry.
And geometry IS space-time.

Without spacetime there is no 'prior'.
Nor a 'when', or even a smaller 'time' increment.

( of course this is all based on Bufofrog's presumption of 'no dimensions' )

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You were probably clear but I was not able to understand it.

Does that mean there was no t+10-44 seconds? And if there was that point in time, why wouldn't it be considered 'prior' to t+10-43 seconds?

(I recognize that perhaps I am mistakingly trying to apply simplistic logic to a more complex situation.)

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2 hours ago, zapatos said:

You were probably clear but I was not able to understand it.

Does that mean there was no t+10-44 seconds? And if there was that point in time, why wouldn't it be considered 'prior' to t+10-43 seconds?

(I recognize that perhaps I am mistakingly trying to apply simplistic logic to a more complex situation.)

A better question is why $10^{-43}$. Would it help to recognize that number is one unit of Planck time with our current observable universe to the volume of 1 Planck length. The temperature being equivalent to Planck temperature. The Planck units are in essence boundary conditions on which our ability to mathematically describe in essence breaks down into Infinities and nonsensical results. You often only hear the space and time axis in essence flipping roles for the GR descriptive but cosmology must also include both macro and quantum effects. So its good to understand how the limits of the macro and quantum theories apply. (String theory also recognizes these limits) One detail as mentioned in this thread is were describing our Observable portion in essence the limits of shared observable causality with our current universe.

Time being a measure of rate of change or duration you in essence need a dimension in order to have something to measure or even something that must be able to change. However one must also realize that the t=0 represents the collective worldlines of all particles in our observable portion extrapolated from the closest we can mathematically describe and potentially measure. In the closest to pointlike we can describe.

It does not represent any time outside our region of shared causality. In essence $10^{-43}$ is the origin of time for all potential worldlines in our observable universe that are extrapolated to the beginning of our observable universe (as the emitter event).

Edited by Mordred

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That was very helpful Mordred. Thank you.

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On 2/19/2020 at 6:55 AM, Bufofrog said:

Matter can be destroyed (converted into energy) and matter can be created (converted from energy)..

To my knowledge energy was never isolated in a pure form by any scientists. According to modern generally accepted views energy is just a varieties of a matter movement forms and as such it cannot exist in a completely isolated form. Also there is a potential energy as well, it cannot exist separately from the matter. When matter and antimatter annihilate - they create gamma photons which are just another kind of matter.

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