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Author Topic: Is the total energy in the Universe conserved?  (Read 17175 times)

Offline thedoc

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Is the total energy in the Universe conserved?
« on: 20/10/2014 14:30:01 »
Manogrie Golden  asked the Naked Scientists:
   
   -  Is the total enegy in the Universe today the same as the total energy of the universe at the time of the Singluarity?  
 
And, if not, why was energy not conserved?
   - Does the Law of the Conservation of Energy still hold if the vacuum is filled with virtual particles, which are popping into and out of existence, and if empty space is producing increasingly more vacuum energy as it expands?
 
Regards,
Manoo


What do you think?
« Last Edit: 20/10/2014 14:30:01 by _system »


 

Offline JohnDuffield

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Re: Is the total energy in the Universe conserved?
« Reply #1 on: 20/10/2014 15:50:11 »
Is the total energy in the Universe today the same as the total energy of the universe at the time of the Singularity?
I think so. Energy is the one thing we can neither create nor destroy. Conservation of energy is something of a "golden rule" in physics. Some people say that dark energy is being continuously created, and/or that conservation of energy does not hold true, but I'm not one of them.

Does the Law of the Conservation of Energy still hold if the vacuum is filled with virtual particles, which are popping into and out of existence, and if empty space is producing increasingly more vacuum energy as it expands?
This is something of a popscience myth. Empty space is empty space. It isn't full of particles popping in and out of existence. Virtual particles are "field quanta". It's like you divide the field up into little squares and say each one is a virtual particle. See Matt Strassler's article here and note this:

"The best way to approach this concept, I believe, is to forget you ever saw the word “particle” in the term. A virtual particle is not a particle at all. It refers precisely to a disturbance in a field that is not a particle."

Virtual particles aren't the same thing as vacuum fluctuations either. For an analogy, think of them as something like the little ripplets on the surface of a sea, think of vacuum energy as the water itself, and think of energy density as the depth of the water. If the sea is getting bigger, then conservation of energy says it's getting shallower. I think the universe is something like this, but many cosmologists will claim it isn't, and that energy is being created ex-nihilo.   
 

Offline syhprum

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Re: Is the total energy in the Universe conserved?
« Reply #2 on: 20/10/2014 16:30:52 »
I have always believed that the energy in radiation and that locked up in matter is counterbalanced by the negative gravitational energy so that the net sum is zero.
 

Offline chiralSPO

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Re: Is the total energy in the Universe conserved?
« Reply #3 on: 20/10/2014 17:28:23 »
I believe that the net zero energy universe theory is currently compatible with our observations of the universe, and I like the idea of that simplicity. But I would feel much more comfortable if we had a way of better measuring dark energy and dark matter, and a better understanding of the energy-matter-dark energy-dark matter equivalence...
 

Offline JohnDuffield

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Re: Is the total energy in the Universe conserved?
« Reply #4 on: 20/10/2014 17:35:00 »
I have always believed that the energy in radiation and that locked up in matter is counterbalanced by the negative gravitational energy so that the net sum is zero.
That's another myth I'm afraid. For the life of me I don't understand why any cosmologist advocates it, because gravitational field energy is positive. See The Foundation of the General Theory of Relativity and look at page 185 where Einstein says "the energy of the gravitational field shall act gravitatively in the same way as any other kind of energy". Gravitational binding energy is said to be negative, but there's no actual negative energy anywhere, just less positive energy. When an object falls down, gravitational potential energy is converted into kinetic energy, and when this is radiated away the mass-energy you're left with is less than what you started with. But no energy has disappeared, conservation of energy applies.
 

Offline jeffreyH

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Re: Is the total energy in the Universe conserved?
« Reply #5 on: 20/10/2014 22:08:37 »
Manogrie Golden  asked the Naked Scientists:
   
   -  Is the total enegy in the Universe today the same as the total energy of the universe at the time of the Singluarity?   
 
And, if not, why was energy not conserved?
   - Does the Law of the Conservation of Energy still hold if the vacuum is filled with virtual particles, which are popping into and out of existence, and if empty space is producing increasingly more vacuum energy as it expands?
 
Regards,
Manoo


What do you think?

Yes and no. The time dilation effects of gravity slow energy down. Time moves more slowly so the apparent energy of a system appears to decrease from the point of view of a distant observer. Within a frame local to the energy source this is not apparent.
 

Offline PmbPhy

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Re: Is the total energy in the Universe conserved?
« Reply #6 on: 21/10/2014 01:11:20 »
Quote from: Manogrie Golden
Is the total enegy in the Universe today the same as the total energy of the universe at the time of the Singluarity?
Yes. The total energy of the universe started out being zero and has remained so. See:
http://en.wikipedia.org/wiki/Zero-energy_universe

Quote from: JohnDuffield
...but there's no actual negative energy anywhere, just less positive energy. When an object falls down, gravitational potential energy is converted into kinetic energy, and when this is radiated away the mass-energy you're left with is less than what you started with. But no energy has disappeared, conservation of energy applies.
This is wrong. It can be shown the gravitational potential energy is negative:
http://en.wikipedia.org/wiki/Gravitational_energy

This claim goes against mainstream physics - please provide a mathematical derivation.

It's now accepted that the total energy of the universe is zero:
http://en.wikipedia.org/wiki/Zero-energy_universe

Alan Guth explained why in his book The Inflationary Universe. For those who really understand this and want to hear what Guth has to say on it, I uploaded it only my personal website. It's at:
http://home.comcast.net/~peter.m.brown/ref/guth_grav_energy.pdf

The reason is simple: as a gravitational field is created there is a corresponding release of energy. Guth explains all of this in that link.
« Last Edit: 28/10/2014 19:45:48 by evan_au »
 

Offline JohnDuffield

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Re: Is the total energy in the Universe conserved?
« Reply #7 on: 21/10/2014 11:05:16 »
Yes. The total energy of the universe started out being zero and has remained so. See: http://en.wikipedia.org/wiki/Zero-energy_universe
That's a hypothesis, not fact.

It can be shown the gravitational potential energy is negative: http://en.wikipedia.org/wiki/Gravitational_energy
No it can't. Gravitational field energy is positive. The gravitational potential energy is only negative by convention because the zero is set at infinity. The potential energy of a falling brick is being converted into kinetic energy. This is positive, and it doesn't vanish when the brick hits the ground, instead it's radiated away.

Your claim goes against mainstream physics - please provide a mathematical derivation.
This is a popscience myth that contradicts general relativity, and you're claiming it's mainstream to bolster your position.

Alan Guth explained why in his book The Inflationary Universe. For those who really understand this and want to hear what Guth has to say on it, I uploaded it only my personal website. It's at:
http://home.comcast.net/~peter.m.brown/ref/guth_grav_energy.pdf

The reason is simple: as a gravitational field is created there is a corresponding release of energy. Guth explains all of this in that link.
This is like the energy that's radiated away when the brick hits the ground. Only it's positive energy, as is the mass-energy of the brick and the Earth, and the Earth's gravitational field energy. Guth says "since the negative energy of the gravitational field is crucial to the notion of a zero energy universe". Only he's wrong, because "the energy of the gravitational field shall act gravitatively in the same way as any other kind of energy". He also says the region began with no energy, which is wrong, because matter is present. All in all, his "explanation" is no explanation at all.
« Last Edit: 28/10/2014 19:49:35 by evan_au »
 

Offline acsinuk

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Re: Is the total energy in the Universe conserved?
« Reply #8 on: 21/10/2014 11:54:03 »
The strings and SUPSYM theories are debunked because the CERN collider found no particles to support the theory.  What we need is a new approach to look for the source of CMBR which in an old thread the doc calls space vacuum energy.

The doc asked the question must energy be conserved throughout the universe and my answer is no it can evolve over time.
 What must be conserved is the electric charge and its 3D magnetic balance; which is what fundamental energy is comprised of anyway.
CliveS
« Last Edit: 28/10/2014 19:51:34 by evan_au »
 

Offline yor_on

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Re: Is the total energy in the Universe conserved?
« Reply #9 on: 25/10/2014 09:27:29 »
I think it's a very neat idea what Pete refers to. To me it speaks about a universe in a equilibrium, in where you find a 'energy' that you gain work from, by transforming 'energy' from one form to another, (useful energy versus unusable from the point of entropy). One problem I have with it is whether there can be a assumed cost involved in transforming, if there is one or not? Then again, that one could be about a ground state of that 'energy' possibly? As if we have a hierarchy of states that all 'falls down' to that ground state, in entropy called heat. As if the energy you can manipulate has been 'concentrated' by a Big Bang, but when transformed by you, spread out into another equilibrium/state. But there is still this nagging feeling that a transformation should mean that something is lost, and how to define it.
=

maybe you can call it 'change', and then the question I have is if change can be without loss?

you could possibly want to define a arrow this way, but then it becomes a self fulfilling definition as change now drives the arrow, that in its turn must be there to drive the change, ad infinitum. This one demands some sort of containment too, to be kept simple. What's not simple from such a definition is how to define a 'outside'.
==

Or maybe it doesn't? If you define it locally, and build your observations of change from that, then time is change, and what you see, locally, is what you get. But it still becomes properties to me, 'magnifying' locality, as QM like to do. Maybe that could be the 'loss' I'm wondering about? I just want to avoid defining a container here :) It becomes soo complicated if you believe in one.

and then the 'loss' comes from interactions, and so causality. The arrow would then belong to the causality we see, and as I define the arrow equivalent to 'c', that should mean both being a result of interactions, which is how I think I like it too. Weird idea :)
« Last Edit: 25/10/2014 10:34:38 by yor_on »
 

Offline PmbPhy

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Re: Is the total energy in the Universe conserved?
« Reply #10 on: 25/10/2014 10:37:11 »
Quote from: JohnDuffield
That's a hypothesis, not fact.
Of course it's an hypothesis and not a "fact." A physicist stays away from using the term "fact" as much as he can. It doesn't have a real place in physics or science as a whole. E.g. no cosmologist in his right mind would claim that the cosmological principle is a fact.

Both the zero-energy universe and the cosmological principle can be thought of as axioms, hypotheses or principles. So you're not really saying anything whatsoever when you say that its an hypothesis and not a fact.

Quote from: JohnDuffield
No it can't. Gravitational field energy is positive. The gravitational potential energy is only negative by convention because the zero is set at infinity.
All physicists know that gravitational energy is negative. This is the context where we can use the term "fact" because it's a "fact" that gravitational energy is negative.
« Last Edit: 28/10/2014 19:53:44 by evan_au »
 

Offline yor_on

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Re: Is the total energy in the Universe conserved?
« Reply #11 on: 25/10/2014 22:45:41 »
Hmm, think you're a little hard on us there Pete. It's not only John that gets confused thinking of gravity as negative energy. I saw someone arguing that Stephen Hawking defined it this way. "Two pieces of matter that are close to each other have less [positive] energy than the same two pieces a long way apart, because you have to expend energy to separate them against the gravitational force that is pulling them together,"

But if we look at frame dependencies imagining a far away 'inertial' observer, observing the gravitational acceleration of a black box, from his frame finding the the box to gain energy as it falls to earth.  So, how does it gain a constantly building, positive energy, from this negative?

And for the observer inside that black box, there is no 'new energy' to be measured as I know of. And from his frame it's Earth coming to get him, as he have no way to define a motion.

could be that there is a simpler definition of it than Hawking's, but reading his argument I get confused too. Also, inside that black box there shouldn't be a thing differing his 'free fall' from any other uniform motion, that as far as I can see, no matter if our inertial observer defines it as accelerating. Is there no other way to define it than using gravity as negative energy to get to a equilibrium?
=

(all of it ideally, ignoring spin.)
« Last Edit: 25/10/2014 23:02:36 by yor_on »
 

Offline PmbPhy

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Re: Is the total energy in the Universe conserved?
« Reply #12 on: 25/10/2014 23:20:49 »
Quote from: yor_on
Hmm, think you're a little hard on us there Pete.
In another forum several others and myself demonstrated to him why gravitational energy is negative. We explained it in many different ways. He never claimed that he didn't understand it. All he did was claim there's no such thing.

I even showed a demonstration of this given by Alan Guth in the appendix of his book The Inflationary Universe. It's online at http://home.comcast.net/~peter.m.brown/ref/guth_grav_energy.pdf if you want to read it.

« Last Edit: 28/10/2014 19:56:06 by evan_au »
 

Offline Ethos_

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Re: Is the total energy in the Universe conserved?
« Reply #13 on: 25/10/2014 23:42:41 »
Quote from: yor_on
Hmm, think you're a little hard on us there Pete.
Please never confuse what I say to JD with what I'd say or think about anybody else. In another forum I saw that he didn't understand this so several others and myself demonstrated to him why gravitational energy is negative. We explained it in many different ways. He never claimed that he didn't understand it. All he did was claim there's no such thing, he ignored all the arguments and proofs given to him and never attempted to demonstrate that he was right with a solid proof. And we kept on trying and trying and trying. We showed him multiple sources so that he'd understand
Agreed Pete, and Wiki also says the following about this question:


"The choice of U=0 at infinity may seem counterintuitive, but this choice allows gravitational potential energy values to be finite, albeit negative."

And: "the choice of U=0 at infinity is by far the more preferable choice, even if the idea of negative energy in a gravity well appears to be peculiar at first."

So, once again JD is reluctant to accept mainstream physics and stays with his own personal interpretations even though they are in error.
« Last Edit: 25/10/2014 23:44:42 by Ethos_ »
 

Offline yor_on

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Re: Is the total energy in the Universe conserved?
« Reply #14 on: 25/10/2014 23:47:34 »
Looked at it, and will reread it later, again. I definitely need to read more about it, at least if this negative energy should be taken at 'face value', as being equivalent (negative energy) to what this article discuss? Becoming somewhat of a wormhole to me :) http://www.bibliotecapleyades.net/ciencia/negativeenergy/negativeenergy.htm
 

Offline yor_on

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Re: Is the total energy in the Universe conserved?
« Reply #15 on: 26/10/2014 07:56:59 »
I would prefer 'negative energy' to just be a result of states. Meaning that there is nothing differing 'energy' from 'energy' more than a equilibrium. If one look at it that way then a vacuum is the equilibrium, as it is 'friction less' and classically empty. Indeterminism or 'virtual particles' then becomes something coming from 'nothing', although you might be able to refer to where it come from as 'negative. Like drawing a line defining the vacuum, calling everything above it 'positive', everything under it 'negative'. Then the equilibrium I see is a result of of a fragile balance on that line, also a symmetry break, called a universe. If I would to adopt this idea. that makes the universe into something using no 'energy' at all, defined from the line, looking both ways.

But keeps energy as energy.
 

Offline yor_on

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Re: Is the total energy in the Universe conserved?
« Reply #16 on: 26/10/2014 08:10:13 »
Doing so, a gravitational potential becomes something under that line, if  I want it to be 'negative energy'. The link I gave treat 'negative energy' as something opposite 'positive energy', making me wonder why they then won't 'annihilate' each other. Don't think that is correct myself.
=

actually it is us defining that line, looking out at the universe. We define the vacuum, we define it as neutral, which it is to us, then split 'energy' in two parts. Above and under that imaginary line.
=

Or looked at another way. Energy become a stream, it 'moves'. And although the directions of energy can be said to go opposite ways split at that line, it's still the same energy doing so. We have a arrow that takes us one way, under that imaginary line the arrow becomes very questionable.
==

In a very weird way it's like charge. Charge is not that 'gopher' you shot, stealing another close to you to to put into that now empty hole, charge is a break of a equilibrium to me, the 'hole' coming into existence, needing a equilibrium, or a symmetry consisting of both the gopher and the hole, under a arrow.
« Last Edit: 26/10/2014 09:26:32 by yor_on »
 

Offline yor_on

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Re: Is the total energy in the Universe conserved?
« Reply #17 on: 26/10/2014 10:20:50 »
So no, and yes, Manogrie. Whatever happened at a Big Bang was a symmetry break, and that is change. Change should have a cost to me. But that change doesn't involve what exist defined by us today. We have very good reasons to assume that conservation laws will hold true, although, to me, that's not the exact same as assuming a 'bubble' in where they do so. It's a symmetry, our symmetry break finding its own symmetry and equilibrium. To do it, it possibly :) invented a arrow?

As Pete once pointed out, there's only a 'inside'. That's where we find ourselves, and it's from there we measure.
 

Offline JohnDuffield

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Re: Is the total energy in the Universe conserved?
« Reply #18 on: 28/10/2014 14:50:25 »
JD stays with his own personal interpretations.
It isn't my personal interpretation. Again see The Foundation of the General Theory of Relativity and look at page 185 where Einstein says "the energy of the gravitational field shall act gravitatively in the same way as any other kind of energy". Gravitational field energy is positive. Pmb hasn't demonstrated why gravitational energy is negative, he hasn't explained it in many different ways, or given any arguments or proofs. And he won't give any explanation/argument/proof here because there isn't any. 

Quote from: yor_on
Hmm, think you're a little hard on us there Pete. It's not only John that gets confused thinking of gravity as negative energy. I saw someone arguing that Stephen Hawking defined it this way. "Two pieces of matter that are close to each other have less [positive] energy than the same two pieces a long way apart, because you have to expend energy to separate them against the gravitational force that is pulling them together"
That's pretty much it. You need to add energy to pull them apart. Then when you let them fall back together, potential energy is converted into kinetic energy, and it isn't negative. Conservation of energy applies, you radiate this kinetic energy away, and then you're back to the original situation. At no point did any positive energy get cancelled out by any negative energy. That's just a popscience myth from people who don't understand general relativity.
« Last Edit: 28/10/2014 19:59:10 by evan_au »
 

Offline jeffreyH

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Re: Is the total energy in the Universe conserved?
« Reply #19 on: 28/10/2014 20:03:33 »
Now I am going to put the cat right amongst the pigeons. Some of what John says above I agree with. Not in the way it is said but what it implies. So don't get excited John I am not exactly backing you up and I would appreciate you not promoting it that way.
 

Offline evan_au

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Re: Is the total energy in the Universe conserved?
« Reply #20 on: 28/10/2014 20:30:36 »
In my simple understanding, Gravity is a field, which creates a force, with a direction which always seems to be attractive. (Electric charge produces another field which can be attractive or repulsive.)

You require energy to move an object against a field - or turn the field's potential energy into kinetic energy when you allow an object to "fall" in the field.

If we are interested in Energy (as per the original post), what matters is the potential difference between two points in the field. The absolute value of the field does not affect the Energy required to move between two points in the field with a given potential difference.
  • With an electric field, because it is "bipolar" (attracts and repels), we have a "natural" zero potential, where all surrounding matter has no excess or shortage of electrons. We can easily create a uniform zero electric field in the laboratory, inside a Faraday cage.
  • However as the gravitational field is "unipolar" (always attractive, as far as we know), has infinite range and cannot be shielded, there is nowhere in the reachable universe that we can use as a "natural" zero potential. So we must pick an arbitrary point to make our calculations easier. 
For myself, as a person who is unlikely to ever travel into space, I might choose my arbitrary zero potential as the surface of the Earth, knowing that if I am climbing a tree which is well above my zero potential, I am likely to break something if I fall. Similarly, if I am standing at the top of a mine, which ends well below my zero potential, I could do myself an injury if I slipped.

Of course, if I were plotting the orbit of Philae landing on a comet or the structure of the galaxy, it would be sensible to select a very different gravitational reference point!

Like all good conventions, they don't make the answer "right" or "wrong", but they do make some calculations easier (simplifying communication), and others more difficult (hindering communication), so by all means choose your convention with care and state which convention you are using - but be aware of its limitations.
« Last Edit: 29/10/2014 11:50:06 by evan_au »
 

Offline jeffreyH

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Re: Is the total energy in the Universe conserved?
« Reply #21 on: 28/10/2014 21:49:39 »
It is in the picking of an arbitrary point that we create difficulties. The universe contains a gradient of forces of varying magnitudes that overlap. The point we choose must equalize all these forces.
 

Offline jeffreyH

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Re: Is the total energy in the Universe conserved?
« Reply #22 on: 28/10/2014 22:35:47 »
Gravitation takes energy away from mass. Not only the kinetic energy but the energy of action. This not only slows the froward momentum but the rates of change. For the photon at the event horizon all its forward momentum has been transferred to the gravitational field which still travels at c when light itself comes to a stop. Only at infinity does the speed of the photon match the speed of gravity. This means that gravity is apparently superluminal right up to infinity due to its dilation effects on the action of energy. Gravitation robs mass of its forward momentum until the mass stops moving forward. It is only then that gravitation can be considered a negative force as it is now subtracting momentum and propelling the mass in an opposite direction. There is a balance in the system so energy is conserved. Before this is kicked into new theories give it a good deal of consideration.
 

Offline acsinuk

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Re: Is the total energy in the Universe conserved?
« Reply #23 on: 29/10/2014 12:20:00 »
Why are we considering gravity energy instead of vacuum energy?
 

Offline JohnDuffield

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Re: Is the total energy in the Universe conserved?
« Reply #24 on: 29/10/2014 14:02:35 »
Because people say gravitational energy is negative, and cancels out all the vacuum energy to leave a universe with a net energy of zero. The trouble with this is that it contradicts general relativity. 

Now I am going to put the cat right amongst the pigeons. Some of what John says above I agree with. Not in the way it is said but what it implies. So don't get excited John I am not exactly backing you up and I would appreciate you not promoting it that way.
No problem, like you said, energy is conserved. If you can find anybody who can actually explain why gravitational energy is negative energy and therefore Einstein was wrong, do let me know.

Quote from: evan_au
You require energy to move an object against a field - or turn the field's potential energy into kinetic energy when you allow an object to "fall" in the field.
The point to remember is that when you lift a brick you do work on the brick. You add energy to it. Then when you drop the brick some of its internal kinetic energy is converted into external kinetic energy. There's no magical mechanism by which kinetic energy somehow flows into the brick from the surrounding space. 
 

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Re: Is the total energy in the Universe conserved?
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