Energy cannot be created. Then where did it all come from?

  • #1
Someone asked me this question: If energy cannot be created then where did the Universe come from?
Are there any websites, papers or documents concerning this question, answer?
The first law of thermodynamics which is a version of the law of conservation of energy, adapted for thermodynamic systems. The law of conservation of energy states that the total energy of an isolated system is constant; energy can be transformed from one form to another, but cannot be created or destroyed.

I have researched all thermodynamic processes to no avail.

Thank You
 
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Answers and Replies

  • #2
russ_watters
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It isn't really known where the universe came from. But the statement that energy can't be created or destroyed does not apply to the universe's creation, it applies only in the universe after it was created. It wouldn't make logical sense for conservation of energy to apply to the creation of the uinverse since before the creation of the universe there was no universe for conservation of energy to be applied to!
 
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  • #3
Danger
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There is also no reason that the laws including those of thermodynamics, gravity, and whatnot came out as they did. In a different big bang, the speed of light (if light even existed) could very well be half of what it is here. If the charge of an electron was -1.3 instead of -1, you'd have a difficult time trying to find something to build a house out of. Things are the way they are just because... they are... :oldcool:
 
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  • #4
Bandersnatch
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There's also the issue of applicability of conservation of energy to cosmological scales.
Have a look at these two articles:
http://www.preposterousuniverse.com/blog/2010/02/22/energy-is-not-conserved/
http://math.ucr.edu/home/baez/physics/Relativity/GR/energy_gr.html

And perhaps this might help too:
http://www.talkorigins.org/faqs/astronomy/bigbang.html#firstlaw
in the absence of a proper definition of gravitational potential energy, the law of conservation of energy from classical mechanics clearly does not hold in GR. Thus, for any theory based on GR, like BBT, conservation of energy is clearly not something that can be held against it. Hence, the first law of thermodynamics argument becomes moot.
 
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  • #5
ChrisVer
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Who said anything about violation of energy?
The total energy of the universe is conserved in BBT.
http://machineslikeus.com/news/big-bang-beginners-13-does-big-bang-theory-violate-law-conservation-energy [Broken]
 
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  • #6
PeterDonis
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The total energy of the universe is conserved in BBT
As the second article Bandersnatch linked to says, it depends on how you define "energy" and how you define "conserved". These terms aren't as simple as you and the article you have linked to appear to believe.

I strongly recommend reading both of Bandersnatch's links, but the basic error the article you linked to makes is to assume that "gravitational potential energy" is a well-defined term for the universe as a whole. It isn't; it is only well-defined in a stationary spacetime, and the universe is not stationary because it is expanding. (The first article Bandersnatch linked to goes into this in some detail.) So the analogy the article makes between analyzing the orbits of satellites around the Earth, and analyzing the universe as a whole, is not really valid.

It turns out that, for a closed universe, you can finesse this point by coming up with a way to define "gravitational potential energy" that works similarly enough to the orbiting satellite scenario to make the analogy valid. However, note that I said "a closed universe"; the article you linked to says this too. According to our best current model, our actual universe is not closed, so this way out doesn't work.

Btw, I should emphasize that I am in sympathy with the desire of the writer of the article you linked to, to not give religious people an excuse to say that the Big Bang theory requires something to be created out of nothing. But there is a much simpler way of doing that, which the article doesn't mention: point out that the law of conservation of energy is really a local law, not a global law: it says that energy can't be created or destroyed in any small volume of spacetime. Our current theories obey this law: in General Relativity it shows up as an identity, the Bianchi identity, which is obeyed by the Einstein Field Equation.
 
  • #7
Who said anything about violation of energy?
The total energy of the universe is conserved in BBT.
http://machineslikeus.com/news/big-bang-beginners-13-does-big-bang-theory-violate-law-conservation-energy [Broken]
"In any big bang model, one must deal with the problem of 'creation'. This problem has two aspects. One is that the conservation laws of physics forbid the creation of something from nothing. The other is that even if the conservation laws were inapplicable at the moment of creation, there is no apparent reason for such an event to occur."

I suppose if every matter has an antimatter then infinite "m" created "c". Annihilation is a release of energy available to do work, proportional to the total matter and antimatter mass, in accord with the mass-energy equivalence equation, E=mc2
 
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  • #8
ChrisVer
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I am sorry, I don't understand what you mean by "infinite m created c" ... it doesn't make sense.
 
  • #9
Drakkith
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"In any big bang model, one must deal with the problem of 'creation'
This statement is wrong. The current big bang model doesn't deal with creation. At all. It merely states that the very early universe was extremely hot and dense and expanded from there. There is no 'creation' event in the model like people think there is.
 
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  • #11
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One is that the conservation laws of physics forbid the creation of something from nothing.
That's not quite correct - photons for example are not conserved.

What you are probably talking about is conservation of energy where if photons for example are created then energy must be supplied. These days that's associated with the celebrated Noether's Theorem - the application of which to the entire universe is a bit problematical as the link I gave previously detailed.

Also, interestingly, gravitational energy in the entire universe is negative, while the energy of matter is positive and the interesting thing is they cancel to give a big fat zero - that leads to the rather interesting view of the universe from nothing.

Thanks
Bill
 
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  • #12
timmdeeg
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Btw, I should emphasize that I am in sympathy with the desire of the writer of the article you linked to, to not give religious people an excuse to say that the Big Bang theory requires something to be created out of nothing. But there is a much simpler way of doing that, which the article doesn't mention: point out that the law of conservation of energy is really a local law, not a global law: it says that energy can't be created or destroyed in any small volume of spacetime. Our current theories obey this law: in General Relativity it shows up as an identity, the Bianchi identity, which is obeyed by the Einstein Field Equation.
I understand that the conservation of energy is a local law. But from a pars pro toto point of view it's not clear to me why this holds for "any small volume of spacetime". Because as I understand it the ideal fluid models require that the spacetime expands at any scale, so also locally. So, something should be the reason that energy conservation in expanding spacetime is obeyed locally, though any local volume expands. Could you kindly explain?
 
  • #13
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I understand that the conservation of energy is a local law. But from a pars pro toto point of view it's not clear to me why this holds for "any small volume of spacetime". Because as I understand it the ideal fluid models require that the spacetime expands at any scale, so also locally. So, something should be the reason that energy conservation in expanding spacetime is obeyed locally, though any local volume expands. Could you kindly explain?
Its related to the curved space-time of GR that breaks the symmetry required of Noethers theorem which is the modern basis of energy conservation -
http://motls.blogspot.com.au/2010/08/why-and-how-energy-is-not-conserved-in.html
'The main lesson here is that general relativity is not a theory that requires physical objects or fields to propagate in a pre-existing translationally invariant spacetime. That's why the corresponding energy conservation law justified by Noether's argument either fails, or becomes approximate, or becomes vacuous, or survives exclusively in spacetimes that preserve their "special relativistic" structure at infinity. At any rate, the status of energy conservation changes when you switch from special relativity to general relativity.'

There are ways around the problem, but, as the link explains there is no clear consensus on what to do about it.

It would be wrong to say that energy is not conserved in GR - its much closer to the truth to say the issue isn't clear eg its not clear energy can even be defined.

Thanks
Bill
 
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  • #14
ChrisVer
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point out that the law of conservation of energy is really a local law, not a global law: it says that energy can't be created or destroyed in any small volume of spacetime.
However I have one question. The conservation of entropy used in cosmology comes from the conservation of energy. How is the conservation of energy used in that scheme?
Also I'm not sure about the global thing. The vacuum energy density is constant in the universe as a whole, that means that is is always increasing with the expansion of the universe, and at a naive level it can be described by the matter/antimatter creation and annihilation happening in the vacuum which is a local thing (of course this doesn't work out fine leading to the cosmological constant problem)
 
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  • #15
PeterDonis
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as I understand it the ideal fluid models require that the spacetime expands at any scale, so also locally
Spacetime does not expand. Spacetime just is. It's a 4-dimensional geometric object. The local energy conservation law applies in each infinitesimal 4-dimensional patch of that 4-dimensional object. The fact that a particular spacetime has geometric properties that are referred to by the word "expansion" doesn't change any of that; from the 4-d point of view, "expansion" is just another word for a particular kind of geometry.
 
  • #16
PeterDonis
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The conservation of entropy used in cosmology comes from the conservation of energy.
Can you give a reference? I'm not sure what you're referring to here.
 
  • #17
timmdeeg
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Thanks, bhobba, for providing this linked article, very interesting.

The local energy conservation law applies in each infinitesimal 4-dimensional patch of that 4-dimensional object.
Thanks for clarifying, I was interpreting "any small volume of spacetime" erroneously.
 
  • #19
PeterDonis
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At eq. 3.2.59
and above where they use the 2nd thermodynamical law [=the conservation of energy]
The second law is the one about entropy; conservation of energy is the first law. The reference does clarify what you meant by "conservation of entropy", however; it's just the approximation (which, as the reference notes, is a good one for the universe as a whole) that the expansion of the universe is adiabatic.
 
  • #20
ChrisVer
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I think adiabatic implies the conservation of energy?
 
  • #21
PeterDonis
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I think adiabatic implies the conservation of energy?
As has already been discussed in this thread, you have to be careful with the concept of "energy" when dealing with the universe as a whole, for two reasons: first, it isn't closed (according to our best current model), so its "total energy" is infinite; second, it's expanding, so it's not stationary, which means the whole idea of "conservation of energy" is problematic.

"Adiabatic", strictly speaking, means no heat transfer (or matter transfer) between the system under study and anything else. The "system under study" in this case is the "cosmological fluid", the homogeneous, isotropic, continuous system of stress-energy that fills the universe in the standard cosmological model. The adiabatic assumption means there is no significant heat transfer between this system and any other matter or energy in the universe. However, that does not necessarily mean the energy of that system is constant (see below).

In the reference you gave, since the key focus of the section you pointed out is entropy, the main component of the "fluid" under study is the CMBR--a photon bath which is taken to be in thermal equilibrium, and which contains the vast majority of the entropy in the universe. However, that does not mean it contains the vast majority of the energy in the universe; and, in fact, it doesn't--it contains a couple of orders of magnitude less energy than ordinary matter (which is itself only a few percent of the total energy according to our best current model--the rest is dark matter and dark energy).

Also, since the universe is expanding, even if we restrict attention to the photon "fluid", and treat its expansion as adiabatic, the total energy of the fluid is not constant, because the expansion redshifts the photons. Before the "surface of last scattering", when the CMBR was emitted, the photons were in thermal equilibrium with the matter (which was a plasma then), so heat was being transferred from the matter to the photons to counteract the redshift of the photons as the universe expanded. But when the matter "recombined" (a strange term since it had never been "combined" before) into atoms and stopped being a plasma, the photons became decoupled from the matter, and ever since, they have been losing energy relative to the matter because of the redshift. This "lost" energy has not been transferred anywhere; it is a manifestation of the fact that, as noted above, global "conservation of energy" is a problematic concept in a non-stationary spacetime.

As far as I can tell, the reference you gave does not use global energy conservation to justify the adiabatic approximation; it only uses continuity of mass-energy and equation 3.2.58, which relates pressure and temperature in equilibrium.
 
  • #22
Ken G
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A lot of very good answers have been given about why it is hard to define a concept of energy such that it is conserved for the universe as a whole, given general relativity. I think there's a deeper issue here, however, because one way to frame the OP question is simply to ask, how can the laws of physics describe the creation of the laws of physics? This is similar to the first answer given, but the point I want to make is that this issue befuddled physicists for a long time. I believe it must have been the reason that Newton, Einstein ,and Hoyle expected the universe as a whole to be unchanging (and infinitely old), they just didn't think that laws of physics could have an origin, as any such origin would be outside the laws of physics.

So the question here is deeper-- it is, how can physics describe its own origin, and if it cannot, does this imply that any origin of a universe requires that something occur that is outside of physics? The Big Bang model finds an astonishingly ingenious solution to this, which some regard as its greatest weakness but I regard it as its greatest strength: it automatically sweeps "under the rug" the whole issue by being a model that always breaks down at some point in time, before you get to the origin. We might even be tempted to assert that any story of the history of the universe, including any that could replace the Big Bang, must either have the property that it has no origin, or it has an origin that is built to make the model itself break down at that point. If we take the first approach, we might imagine some kind of conservation law that never breaks down, and if we take the second approach, it is required that any conservation law must break down at that origin, because all laws do.
 
  • #23
ChrisVer
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The origin cannot be answered by BBT of course. There are still unknown open-questions in the High energy particle physics....(eg GUT scale, Planck Scale etc).
I am not an expert on the particular topic but... people, who work with strings, tend to claim that string theory allows for the origin to happen by itself and without an exterior factor. Since they do so, string theory should be able to give such an answer (in parallel to "infinite" many universes), but we don't know whether the theory is true or not...
 
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Btw, I should emphasize that I am in sympathy with the desire of the writer of the article you linked to, to not give religious people an excuse to say that the Big Bang theory requires something to be created out of nothing. But there is a much simpler way of doing that, which the article doesn't mention: point out that the law of conservation of energy is really a local law, not a global law: it says that energy can't be created or destroyed in any small volume of spacetime. Our current theories obey this law: in General Relativity it shows up as an identity, the Bianchi identity, which is obeyed by the Einstein Field Equation.
Why should a physicist seeking empirical knowledge be worried about what religious people think? Energy is either conserved at the big bang or it isn't. Using physics to put down religiously held worldviews is a bad way of doing science. It is as bad as a young Earth creationist trying to use physics to prove the Earth is only 6000 years old. Neither person is doing science objectively at this point. They are trying to prove something with an a-priori assumption. Just do objective science, and let people sort it out for themselves instead of making this a competition about whose worldview is correct.

Chris
 
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  • #25
PeterDonis
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Why should a physicist seeking empirical knowledge be worried about what religious people think?
He shouldn't. But a citizen worried about how large a segment of the US population believes things that have been scientifically falsified, and translates those false beliefs into counterproductive social and political actions, should.
 
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