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Author Topic:   Does the universe have total net energy of zero?
designtheorist
Member (Idle past 2774 days)
Posts: 390
From: Irvine, CA, United States
Joined: 09-15-2011


Message 153 of 404 (644616)
12-19-2011 2:52 PM
Reply to: Message 152 by Modulous
12-19-2011 1:40 PM


Re: Is net zero energy universe "not even wrong?"
Negative pressure is not 'anti gravity' in the technical sense (which may require negative mass) - only in a colloquial sense. It's easy to get confused on that, though.

Poor terminology leads to poor thinking. I'm certainly open to corrections in my terminology. A more heinous error in terminology is calling dark energy the "cosmological constant." It is used quite commonly but Einstein used the term as a way to keep the universe from changing. Dark energy is the opposite of Einstein's idea.

There are several ideas afloat about the nature of dark energy. Truthfully, we don't know exactly what it is. What we do know, unequivocally, is that the influence of dark energy completely overpowers the effects of gravity on a cosmological scale. Is dark energy subject to gravity? Possibly, but the repulsion effects of dark energy are greater than the effects of gravity. How can one believe gravity has the same energy as all of matter and dark energy combined when we can see that dark energy alone is more powerful than gravity?

Edited by designtheorist, : No reason given.

Edited by designtheorist, : No reason given.


This message is a reply to:
 Message 152 by Modulous, posted 12-19-2011 1:40 PM Modulous has acknowledged this reply

Replies to this message:
 Message 154 by cavediver, posted 12-19-2011 5:55 PM designtheorist has responded

  
designtheorist
Member (Idle past 2774 days)
Posts: 390
From: Irvine, CA, United States
Joined: 09-15-2011


Message 156 of 404 (644643)
12-19-2011 6:14 PM
Reply to: Message 154 by cavediver
12-19-2011 5:55 PM


Re: Is net zero energy universe "not even wrong?"
Charming.

This message is a reply to:
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Replies to this message:
 Message 158 by cavediver, posted 12-19-2011 6:24 PM designtheorist has responded

  
designtheorist
Member (Idle past 2774 days)
Posts: 390
From: Irvine, CA, United States
Joined: 09-15-2011


Message 159 of 404 (644647)
12-19-2011 6:27 PM
Reply to: Message 155 by cavediver
12-19-2011 6:04 PM


Re: On the nature of negative gravitational energy – Part II
You really do need to realise just how little you understand here, and just how much pure gibberish you are spouting.

I asked you to bring your A game. This isn't it. Minor differences in expression is a matter of semantics.

Gravitation is not energy so the question makes no sense.

I was, of course, referring to gravitational field energy. Your comment may seem witty to you, but will strike the average reader as an attitude which is not in line with the purpose of this website -"Understanding through discussion." You seem to think you have understanding, but your not sharing any.

The gravitation field is described by a tensor field, and so cannnot be simply "negative".

Are you agreeing with me then that the net energy of the universe cannot be zero?

Regarding my observation that gravitational field energy is dependent on the existence of matter, you write:

No, it most certainly is not. Consider any of the vacuum solutions of General Relativity.

Now here you may be making a contribution. But perhaps not. Can you provide me with any link of explanation of this pithy statement?

For future reference, I do try to save key strokes. If you see me refer informally to gravity when you know I have in mind gravitational field energy, please address the actual question I am raising. Lots of question marks in a line do not advance understanding.


This message is a reply to:
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designtheorist
Member (Idle past 2774 days)
Posts: 390
From: Irvine, CA, United States
Joined: 09-15-2011


Message 160 of 404 (644648)
12-19-2011 6:29 PM
Reply to: Message 158 by cavediver
12-19-2011 6:24 PM


Re: Is net zero energy universe "not even wrong?"
The ad hominem attacks do not help your cause, whatever that cause may be. If you have an answer for the argument I raise, let's hear it.

This message is a reply to:
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 Message 162 by subbie, posted 12-19-2011 6:49 PM designtheorist has responded

  
designtheorist
Member (Idle past 2774 days)
Posts: 390
From: Irvine, CA, United States
Joined: 09-15-2011


Message 161 of 404 (644649)
12-19-2011 6:37 PM
Reply to: Message 157 by cavediver
12-19-2011 6:18 PM


Re: On the nature of negative gravitational energy – Part I
I see you disagree with my reading of Guth's explanation. Have you actually read the appendix? Have you seen the illustration?

Guth does not say he is reducing the volume occupied by the mass. The circle does not get thicker. The space inside the hollowed out ball is smaller but the implications of this are uncertain if he is reducing the mass as well.

How would energy be extracted from the ball if he is only reducing the volume occupied by the mass? It would seem to me reducing the volume would require an input of energy such as the compaction of making a snow ball.

I look forward to your insightful answers.


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 Message 163 by Dr Adequate, posted 12-19-2011 7:06 PM designtheorist has responded

  
designtheorist
Member (Idle past 2774 days)
Posts: 390
From: Irvine, CA, United States
Joined: 09-15-2011


Message 164 of 404 (644654)
12-19-2011 7:32 PM
Reply to: Message 162 by subbie
12-19-2011 6:49 PM


Re: Is net zero energy universe "not even wrong?"
Ad hominem attacks come in different types. Wikipedia says:

Abusive ad hominem (also called personal abuse or personal attacks) usually involves insulting or belittling one's opponent in order to attack his claim or invalidate his argument...

And yes, calling me a twit is an ad hom attack.


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 Message 162 by subbie, posted 12-19-2011 6:49 PM subbie has responded

Replies to this message:
 Message 166 by subbie, posted 12-19-2011 8:03 PM designtheorist has responded

  
designtheorist
Member (Idle past 2774 days)
Posts: 390
From: Irvine, CA, United States
Joined: 09-15-2011


Message 165 of 404 (644655)
12-19-2011 7:38 PM
Reply to: Message 163 by Dr Adequate
12-19-2011 7:06 PM


Re: On the nature of negative gravitational energy – Part I
Can you please explain this portion for me?

Part (b) shows how energy can be extracted as the shell is allowed to uniformly contract. Each piece of the shell is tied by a rope to an electrical generator, producing power as the piece is “lowered” toward its final position.

How is energy extracted? What effect does the rope have when "tied" to an electrical generator? Isn't there an energy output in "allowing" the mass to uniformly contract?


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 Message 163 by Dr Adequate, posted 12-19-2011 7:06 PM Dr Adequate has responded

Replies to this message:
 Message 168 by kbertsche, posted 12-19-2011 9:20 PM designtheorist has responded
 Message 181 by Dr Adequate, posted 12-20-2011 1:38 PM designtheorist has not yet responded

  
designtheorist
Member (Idle past 2774 days)
Posts: 390
From: Irvine, CA, United States
Joined: 09-15-2011


Message 169 of 404 (644668)
12-19-2011 10:28 PM
Reply to: Message 168 by kbertsche
12-19-2011 9:20 PM


Re: On the nature of negative gravitational energy – Part I
The basic idea is that gravity "wants" to pull things together. If no other forces counteract it, gravity will do so. In principle, this gravitational force could be harnessed to do work on an external device such as a generator. (Force times distance equals work or energy.). This extracts energy from the gravitational field.

I still don't get it. Can you answer the individual questions I asked? I don't understand how gravitational field energy could be used to run a generator as in Guth's analogy.

Okay, you have added a new paragraph. I still don't get it. You write:

But since energy is conserved, and positive energy has been extracted to the generator, the gravitational field must contain negative energy.

Are you saying that as you extract energy from the gravitational field then the negative gravitational field energy becomes stronger? That seemed to be Guth's claim as well. It is an interesting thought but I still don't see how energy would be extracted without an energy expenditure.

Edited by designtheorist, : No reason given.


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designtheorist
Member (Idle past 2774 days)
Posts: 390
From: Irvine, CA, United States
Joined: 09-15-2011


Message 170 of 404 (644669)
12-19-2011 10:43 PM


Is negative energy a mathematical convention or something different?
From Wikipedia article on Potential Energy:

Why choose a convention where gravitational energy is negative?

Gravitational potential is a scalar potential energy per unit mass at each point in space associated with the force fields. Notice at r tends to infinity, ϕ tends to 0 :.
As with all potential energies, only differences in gravitational potential energy matter for most physical purposes, and the choice of zero point is arbitrary. Given that there is no reasonable criterion for preferring one particular finite r over another, there seem to be only two reasonable choices for the distance at which U becomes zero: r = 0 and . The choice of U = 0 at infinity may seem peculiar, and the consequence that gravitational energy is always negative may seem counterintuitive, but this choice allows gravitational potential energy values to be finite, albeit negative.
The singularity at r = 0 in the formula for gravitational potential energy means that the only other apparently reasonable alternative choice of convention, with U = 0 for r = 0, would result in potential energy being positive, but infinitely large for all nonzero values of r, and would make calculations involving sums or differences of potential energies beyond what is possible with the real number system. Since physicists abhor infinities in their calculations, and r is always non-zero in practice, the choice of U = 0 at infinity is by far the more preferable choice, even if the idea of negative energy appears to be peculiar at first.
The negative value for gravitational energy also has deeper implications that make it seem more reasonable in cosmological calculations where the total energy of the universe can meaningfully be considered; see inflation theory for more on this.

So is the claim then that all of the positive energy of matter and energy is offset by the potential negative energy of the gravitational field? Are Krauss and the others who hold to zero energy universe offsetting real energy in the universe with potential gravitational energy?


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designtheorist
Member (Idle past 2774 days)
Posts: 390
From: Irvine, CA, United States
Joined: 09-15-2011


Message 171 of 404 (644670)
12-19-2011 10:58 PM
Reply to: Message 166 by subbie
12-19-2011 8:03 PM


Re: Is net zero energy universe "not even wrong?"
Please compare these two comments from you:

Not only do you know nothing about the topic, you don't even know what an ad hominem is.

and

Calling you a twit for the sole purpose of alerting others to your twithood with no intent to attack your claim or invalidate your argument is not ad hominem...

As you can plainly see, you were trying to "attack" my claim by saying I don't know anything about the topic even as you called me a twit. Personal abuse and name-calling is always an ad hom attack. Just so you know.


This message is a reply to:
 Message 166 by subbie, posted 12-19-2011 8:03 PM subbie has responded

Replies to this message:
 Message 172 by subbie, posted 12-19-2011 11:34 PM designtheorist has responded

  
designtheorist
Member (Idle past 2774 days)
Posts: 390
From: Irvine, CA, United States
Joined: 09-15-2011


Message 173 of 404 (644676)
12-19-2011 11:47 PM
Reply to: Message 172 by subbie
12-19-2011 11:34 PM


Reply to subbie
I was originally grateful for the offer, but I should not have that attitude.

Any on topic post from you would be welcome.

Edited by designtheorist, : No reason given.


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 Message 172 by subbie, posted 12-19-2011 11:34 PM subbie has acknowledged this reply

  
designtheorist
Member (Idle past 2774 days)
Posts: 390
From: Irvine, CA, United States
Joined: 09-15-2011


Message 177 of 404 (644743)
12-20-2011 12:03 PM
Reply to: Message 168 by kbertsche
12-19-2011 9:20 PM


Reply to kbertsche
I like thought experiments. The one you proposed is not clear to me but a very similar thought experiment is clear.

Imagine an asteroid on a near collision course with an earth-like planet. As the asteroid approaches the planet, the gravitational field energy is increased and the kinetic energy (velocity) is increased. Based on the conservation of energy, the gravitational field energy must be negative.


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 Message 179 by kbertsche, posted 12-20-2011 12:12 PM designtheorist has not yet responded

  
designtheorist
Member (Idle past 2774 days)
Posts: 390
From: Irvine, CA, United States
Joined: 09-15-2011


Message 183 of 404 (644807)
12-20-2011 8:33 PM


How much energy is in empty space?
I still have not gotten my hands on the original paper published in 1962 or 1963 by Richard Feynman on zero net energy. Business has kept me away from the local university library (shorter hours during the Christmas vacation).

However, I did come across an interesting description/analysis/report of Feynman's calculations attributed to Arthur C Clarke. See http://www.checktheevidence.com/...rehouse%20of%20energy.htm

That some energy is stored is empty space is a reasonable, even inevitable, conclusion. But to say empty space has more energy than U-238... well, that seems a bit much to me.

If Feynman believed empty space stored that much energy, how could he hold to a net zero energy universe? Or, did Feynman later reject the idea of a zero energy universe?


Replies to this message:
 Message 184 by hooah212002, posted 12-20-2011 9:20 PM designtheorist has responded
 Message 186 by Percy, posted 12-20-2011 9:36 PM designtheorist has not yet responded

  
designtheorist
Member (Idle past 2774 days)
Posts: 390
From: Irvine, CA, United States
Joined: 09-15-2011


Message 185 of 404 (644813)
12-20-2011 9:36 PM
Reply to: Message 184 by hooah212002
12-20-2011 9:20 PM


Re: How much energy is in empty space?
I happen to be a big fan of Feynman, but that does not mean I think he is infallible. There is another possibility of course... that Clarke has misunderstood Feynman or that Cano has misunderstood Clarke.

I linked the website because I thought other inquiring minds here might be interested in it. If you are not interested, don't read it.


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 Message 184 by hooah212002, posted 12-20-2011 9:20 PM hooah212002 has responded

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designtheorist
Member (Idle past 2774 days)
Posts: 390
From: Irvine, CA, United States
Joined: 09-15-2011


Message 187 of 404 (644815)
12-20-2011 9:40 PM


Some interesting papers on dark energy
I am not claiming to have digested these papers yet, but I thought others here might be interested in how they might inform our discussion.

http://arxiv.org/pdf/astro-ph/0207347

http://arxiv.org/pdf/hep-th/0603057

http://arxiv.org/PS_cache/astro-ph/pdf/0406/0406504v2.pdf

The first two papers are highly cited and provide some interesting background to the topic. The third is not highly cited; it simply proposes research but is interesting in its own way.


  
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