Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Bill S on 22/06/2018 23:20:00
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I’ve tried on a number of occasions to get an answer to this, including in a recent thread. Perhaps separating it from other material might do the trick.
Consider the statement: “The total amount of energy in the universe is zero.”
Are there two ways in which this could be interpreted?
1. There is no energy in the Universe.
2. There is a specific amount of positive energy in the Universe. There is also a specific amount of negative energy in the Universe. These amounts are equal, therefore, the balance is zero.
In the case of our Universe, there is, manifestly, an energy content, therefore 1 cannot apply.
If 2 is the appropriate interpretation, although the positive and negative energies cancel each other, they cannot destroy each other; thus, there must be a difference between “zero energy” and “a zero balance of energy”.
I’m prepared to acknowledge that my reasoning could be wrong, but I would appreciate knowing how/where.
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Howabout we start with this:
There is the same amount of energy before the big bang as there is now. The total amount of energy in the universe is zero. That's how energy remain conserved as it was created. There's two kinds of energy; positive and negative. Negative energy comes from gravitational potential energy and positive energy comes from particles. You can read about it in The Inflationary Universe by Alan Guth. I can make those pages available to you if you'd like?
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Thanks Colin.
I started with that, and it all seems to have gone down hill from there. :(
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Are you thinking of transformations Bill?
Entropy?
And how it can exist?
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During the big bang there was a period when there was only one force. This was a combination of the strong, weak, electromagnetic and gravitational forces. As the big bang progressed these forces separated out. The question to ask is what was the energy balance during this process and how does it relate to the current state of the universe?
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Are you thinking of transformations Bill?
No. I'm thinking: is there a difference between no energy and two lots of energy, each of which cancels out the other, but both of which remain.
The question to ask is what was the energy balance during this process and how does it relate to the current state of the universe?
OK, so I asked the wrong question! Does this mean that no one knows the answer to my question; there is no answer to my question; or, my question is so silly, it makes no sense to anyone other than me?
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What is (an example of) "energy balance"?
Would it be kinetic energy versus potential energy?
In what sense can it be said that the energy balance of the universe (or any "closed" system) is zero?
@the OP is my "Why is energy observer dependent?" thread connected possibly?
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What is (an example of) "energy balance"?
There's two kinds of energy; positive and negative. Negative energy comes from gravitational potential energy and positive energy comes from particles.
I have no quarrel with this as an example of energy types that might balance. I don't see it as answering the original question.
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I have no quarrel with this as an example of energy types that might balance. I don't see it as answering the original question.
Are you assuming energy is a "thing" rather than a property?
Just because it may be zero (on overall balance) does not mean that it is a property of nothing. (a misunderstanding of "energy is zero"?)
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Are you thinking of transformations Bill?
No. I'm thinking: is there a difference between no energy and two lots of energy, each of which cancels out the other, but both of which remain.
The question to ask is what was the energy balance during this process and how does it relate to the current state of the universe?
OK, so I asked the wrong question! Does this mean that no one knows the answer to my question; there is no answer to my question; or, my question is so silly, it makes no sense to anyone other than me?
No it wasn't the wrong question at all. I just extended it. There can never be just zero energy. Otherwise nothing exists. The energies can balance out. Imagine an object at its apex of a trajectory upwards in a gravitational field. The kinetic and potential energies balance. This does not mean that the energy of the object is gone. It still has rest energy.
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If the fundamental energy in the universe were electrical then it could balance if the negatively charged matter balanced the positively charged stuff?
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No. There's no difference.
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No. There's no difference.
Can you make a (useful) distinction between global energy and local energy?
Haven't got around to looking at your link yet...
http://www.newenglandphysics.org/physics_world/cm/what_is_energy.htm
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I was addressing his comment
1. There is no energy in the Universe.
2. There is a specific amount of positive energy in the Universe. There is also a specific amount of negative energy in the Universe. These amounts are equal, therefore, the balance is zero.
Which to me are sentences saying the exact same thing in two different ways. I don't know what you mean by global and local. Energy is energy. To me there's little difference in calculating the energy of a charge sphere (global) and that in an immediate area such as between the plates of a capacitor.
By the way. I hear that the person who wrote that page is a crackpot. :)
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I don't know what you mean by global and local
Well, a small system might have the energy of the interactions between its elements measured and the result might sum up to a positive or a negative amount ** depending on the frame of reference within the system.
As the system is decreased in size and corresponding energetic measurements are made then the outcome might be described as "local" compared to the outcome if the system was increased in size infinitely (then it would be "global").
But then ,I think you may have correctly understood my meaning judging that from your " charge sphere (global) and that in an immediate area such as between the plates of a capacitor" comment.
**eg potential energy would be the negative of kinetic energy ,perhaps.
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There can never be just zero energy. Otherwise nothing exists. The energies can balance out. Imagine an object at its apex of a trajectory upwards in a gravitational field. The kinetic and potential energies balance. This does not mean that the energy of the object is gone. It still has rest energy.
Thanks Jeffrey, that seems to say quite clearly that there is a difference between zero energy and a zero balance.
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1. There is no energy in the Universe.
2. There is a specific amount of positive energy in the Universe. There is also a specific amount of negative energy in the Universe. These amounts are equal, therefore, the balance is zero.
Pete, I’m probably confused, but I have to ask if you are saying that statements 1 & 2 above are “saying the exact same thing in two different ways”.
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There is a difference between the absence of energy and a balance of energy types. I think elsewhere @chiralSPO made the point that even at absolute zero there is still motion. The zero point energy. So that does make the distinction. If we ignore zero point energy then we are left considering a state without any relative motion between objects. Not a tenable position with the known forces.
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Not a tenable position with the known forces.
Consider the statement: “The total amount of energy in the universe is zero.”
Are there two ways in which this could be interpreted?
1. There is no energy in the Universe.
2. There is a specific amount of positive energy in the Universe. There is also a specific amount of negative energy in the Universe. These amounts are equal, therefore, the balance is zero.
In the case of our Universe, there is, manifestly, an energy content, therefore 1 cannot apply.
This was my "low-tech" way of expressing the same idea.
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If a concept is becoming complicated then it is losing its merit.
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It's a weird concept Bill. Semantically a zero balance of energy seems to implicate 'different types' of energy?
That doesn't make sense if 'energy' is a coin of exchange?
If it isn't?
then 'energy' is something in itself, and very tentatively can have different values
I don't think that is right though
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It's a weird concept Bill. Semantically a zero balance of energy seems to implicate 'different types' of energy?
That doesn't make sense if 'energy' is a coin of exchange?
Are you saying that there cannot be negative and positive energy?
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I’ve tried on a number of occasions to get an answer to this, including in a recent thread. Perhaps separating it from other material might do the trick.
Consider the statement: “The total amount of energy in the universe is zero.”
Are there two ways in which this could be interpreted?
1. There is no energy in the Universe.
2. There is a specific amount of positive energy in the Universe. There is also a specific amount of negative energy in the Universe. These amounts are equal, therefore, the balance is zero.
In the case of our Universe, there is, manifestly, an energy content, therefore 1 cannot apply.
If 2 is the appropriate interpretation, although the positive and negative energies cancel each other, they cannot destroy each other; thus, there must be a difference between “zero energy” and “a zero balance of energy”.
I’m prepared to acknowledge that my reasoning could be wrong, but I would appreciate knowing how/where.
Are both (1 and 2) just mathematical abstractions?
If you take the first then we are talking about a situation vanishingly close to no relative motion between any object in the Universe (cannot be "none" ) and the second case ,similarly applies (presumably) to our present situation where energy measurement balance out almost exactly ( such a measurement could not be made to any degree of accuracy bearing in mind that an unknowable(?) amount of the universe is unobservable.
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There can never be just zero energy. Otherwise nothing exists.
There can always be zero energy even in classical physics. The universe may have started out with zero energy wherein the creation of matter consisted of positive energy the associated gravitational energy was negative making the total energy zero.
Seems like people ignored me on that one (or I forgot to mention it). This is explained by Guth in his book on inflation.
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Well, one argument for negative energy is, as Pete points out, gravity. To get out of a gravitational 'field/hole' you need to expend energy. And the energy spent then becomes a opposite, a so called 'positive energy' (rocket f.ex). It's a difficult definition though to accept, as 'energy', to me then, doesn't seem to be anything specific in itself
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Then again. if you look at transformations there must be some sort of loss aka going from useful energy to unusable. one main idea is that nothing is ever lost in this universe, it just transforms. But if something goes from being able to do work in some way, to lose that ability? It's a difference, and even if nothing measurable is 'lost' something definitely has disappeared, hasn't it? The ability to do further work
Now let's take that reasoning one step further, I think we both would agree on this rocket expending/losing energy climbing the gravity well. But can the same be said for the gravity well? I don't think so, it stays the same, loosely speaking neither losing nor gaining anything by the rocket leaving. The mass of that rocket could be said to be lost to this gravity well but I don't see that balancing out the energy spent from the rockets point of view. Just think of it leaving a neutron star.
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the main point being that if you have a definition split into opposites, positive and negative, they should act the same although from different sides of the fence (balance out). So positive energy transforms and lose the ability to do work, but this negative energy represented by gravity?
You can also think of it in terms of 'virtual particle pairs' spontaneously appearing, are they consisting of one 'positive' and one 'negative'? Aren't those particles both, if able to stay, 'positive', then meaning able to do work?
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There is one more hurdle to it from my perspective. The way I think of 'gravity' is as geodesics, there is no 'force' acting on a thrown ball, it's just following its geodesic. Now, I'm not sure how to see this 'negative energy' but it can't be a force if it is to fit that.