Understanding through Discussion


Welcome! You are not logged in. [ Login ]
EvC Forum active members: 66 (9035 total)
92 online now:
dwise1, kjsimons, PaulK, ringo, Tangle (5 members, 87 visitors)
Newest Member: Barry Deaborough
Post Volume: Total: 885,602 Year: 3,248/14,102 Month: 189/724 Week: 38/93 Day: 3/6 Hour: 0/1


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
Author Topic:   Does the universe have total net energy of zero?
kbertsche
Member (Idle past 1024 days)
Posts: 1427
From: San Jose, CA, USA
Joined: 05-10-2007


Message 17 of 404 (643690)
12-10-2011 11:48 AM
Reply to: Message 11 by designtheorist
12-10-2011 10:19 AM


Re: Is the total net energy in the universe zero?
quote:
So Krauss, Hawking, Silk, Davies - all of the leading authors in physics and astronomy - seem to agree that the net total energy for the universe is zero or close to zero.

I am extremely skeptical of this. The total net energy of the universe looks to be strongly, strongly positive.


I'm interested in this question, too. I hope Cavediver or someone else who really understands it can explain it to us.

The popular "history of the universe" graphic on NASA's WMAP site has the universe starting with a "quantum fluctuation". By Heisenberg's uncertainty principle, this would only be possible for a 13.7 billion year old universe if the total energy of the universe were almost exactly zero.

As Designtheorist says, the mass energy is large, and dark matter makes it even larger. Gravitational energy is negative, but is it enough to balance the mass energy? And what about dark energy? Since it is repulsive rather than attractive, it should add more positive energy that would have to be balance by gravity.

Can someone explain how the total mass-energy can be zero?


"Science without religion is lame, religion without science is blind." – Albert Einstein

“I am very astonished that the scientific picture of the real world around me is very deficient. It gives us a lot of factual information, puts all of our experience in a magnificently consistent order, but it is ghastly silent about all and sundry that is really near to our heart, that really matters to us. It cannot tell us a word about red and blue, bitter and sweet, physical pain and physical delight; it knows nothing of beautiful and ugly, good or bad, God and eternity. Science sometimes pretends to answer questions in these domains, but the answers are very often so silly that we are not inclined to take them seriously.” – Erwin Schroedinger


This message is a reply to:
 Message 11 by designtheorist, posted 12-10-2011 10:19 AM designtheorist has not yet responded

  
kbertsche
Member (Idle past 1024 days)
Posts: 1427
From: San Jose, CA, USA
Joined: 05-10-2007


Message 47 of 404 (643757)
12-11-2011 12:39 PM
Reply to: Message 40 by cavediver
12-11-2011 8:04 AM


Re: Does any of this matter or even make sense?
Cavediver,

Thanks for the explanations. This is another of the times that I wish I had taken the GR course in grad school!

As far as I know, the experimental data is consistent with a flat universe (reference; see Fig 5).

Apparently, the claim of zero net energy is equivalent to the claim of perfect flatness to the universe? Can you explain this relationship to us a bit better?

(BTW, the claim that the universe arose from an initial "quantum fluctuation" has the same problems (but worse, IMO) as the claims that the universe "began to exist". A fluctuation is something that occurs in time; how can a "fluctuation" occur if time and space do not yet exist?)

Edited by kbertsche, : No reason given.


"Science without religion is lame, religion without science is blind." – Albert Einstein

“I am very astonished that the scientific picture of the real world around me is very deficient. It gives us a lot of factual information, puts all of our experience in a magnificently consistent order, but it is ghastly silent about all and sundry that is really near to our heart, that really matters to us. It cannot tell us a word about red and blue, bitter and sweet, physical pain and physical delight; it knows nothing of beautiful and ugly, good or bad, God and eternity. Science sometimes pretends to answer questions in these domains, but the answers are very often so silly that we are not inclined to take them seriously.” – Erwin Schroedinger


This message is a reply to:
 Message 40 by cavediver, posted 12-11-2011 8:04 AM cavediver has not yet responded

  
kbertsche
Member (Idle past 1024 days)
Posts: 1427
From: San Jose, CA, USA
Joined: 05-10-2007


Message 125 of 404 (643955)
12-13-2011 11:36 AM
Reply to: Message 120 by cavediver
12-13-2011 2:53 AM


Re: Hamiltonian definition of energy always equals net zero
Cavediver--any answer or comments to my earlier question of how flatness is related to zero net energy? We have experimental evidence of flatness, so if there's a relationship to zero net energy, this would help to give zero net energy some experimental grounding.

"Science without religion is lame, religion without science is blind." – Albert Einstein

“I am very astonished that the scientific picture of the real world around me is very deficient. It gives us a lot of factual information, puts all of our experience in a magnificently consistent order, but it is ghastly silent about all and sundry that is really near to our heart, that really matters to us. It cannot tell us a word about red and blue, bitter and sweet, physical pain and physical delight; it knows nothing of beautiful and ugly, good or bad, God and eternity. Science sometimes pretends to answer questions in these domains, but the answers are very often so silly that we are not inclined to take them seriously.” – Erwin Schroedinger


This message is a reply to:
 Message 120 by cavediver, posted 12-13-2011 2:53 AM cavediver has not yet responded

  
kbertsche
Member (Idle past 1024 days)
Posts: 1427
From: San Jose, CA, USA
Joined: 05-10-2007


Message 168 of 404 (644662)
12-19-2011 9:20 PM
Reply to: Message 165 by designtheorist
12-19-2011 7:38 PM


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


This is called a "thought experiment" and has a grand tradition in physics. Thought experiments are very helpful in figuring out how to think about a problem.

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. Thus the gravitational field loses energy.

Imagine two masses that are infinitely far apart. There is no gravitational force between them, and no gravitational energy in the system. As they move closer together, they can do work on (supply energy to) an external device like a generator. But since energy is conserved, and positive energy has been extracted to the generator, the gravitational field must contain negative energy.

Edited by kbertsche, : Add last paragraph


"Science without religion is lame, religion without science is blind." – Albert Einstein

“I am very astonished that the scientific picture of the real world around me is very deficient. It gives us a lot of factual information, puts all of our experience in a magnificently consistent order, but it is ghastly silent about all and sundry that is really near to our heart, that really matters to us. It cannot tell us a word about red and blue, bitter and sweet, physical pain and physical delight; it knows nothing of beautiful and ugly, good or bad, God and eternity. Science sometimes pretends to answer questions in these domains, but the answers are very often so silly that we are not inclined to take them seriously.” – Erwin Schroedinger


This message is a reply to:
 Message 165 by designtheorist, posted 12-19-2011 7:38 PM designtheorist has responded

Replies to this message:
 Message 169 by designtheorist, posted 12-19-2011 10:28 PM kbertsche has not yet responded
 Message 177 by designtheorist, posted 12-20-2011 12:03 PM kbertsche has responded

  
kbertsche
Member (Idle past 1024 days)
Posts: 1427
From: San Jose, CA, USA
Joined: 05-10-2007


Message 176 of 404 (644741)
12-20-2011 11:58 AM
Reply to: Message 137 by designtheorist
12-17-2011 2:18 PM


Re: On the nature of negative gravitational energy – Part I
I'll try again to answer your questions, but I'm not sure that I can explain it any better than I've already tried to do.

quote:
Part (a) is a three-dimensional sphere, represented in Figure A2 as a large circle. The gravitational field lines pointing at the circle end at the point of the circle. They do not proceed to the center of the hollow sphere.

Part (b) is a somewhat smaller circle (intermediate-sized) circle. Outside of the circle are figures representing ropes and generators. This is the stage at which energy is extracted.

Part (c) shows a smaller circle. The ropes and generators are gone. The original larger circle is represented by a dotted line. The area between the smaller circle and the dotted circle is shaded. The gravitational lines now extend past the dotted circle and stop at the smaller circle.

According to Dr. Guth, energy is extracted and the gravitational field is enlarged and together this proves gravitational field energy is negative. Really, Dr. Guth?



Yes, really. If energy is conserved, and positive energy was extracted from the gravitational field, then the gravitational field energy must have become more negative.

quote:
According to this thinking, the smallest particle would have the largest gravitational field.

If the mass is held constant, then as it shrinks to a smaller and smaller volume, the gravitational field becomes stronger and the gravitational field energy becomes more negative. As your wiki article said, if the mass were to shrink to a size of zero the gravitational field energy would become infinite.

quote:
Perhaps I am missing the point, but let’s examine this. It appears that energy is extracted from the hollow shell of mass by reducing the size of the mass. If one reduces the mass, then the strength of the gravitational field is reduced. The fact the region of the field is increased is meaningless.

No, the volume is reduced, but the mass remains fixed. The mass does not reduce.

quote:
None of these illustrations or descriptions of gravity show persuasively that gravitational energy is negative.

Then you haven't quite grasped the arguments yet. Guth's and wikipedia's arguments should be persuasive.

quote:
But even if they did, all the illustrations are dealing with local effects. Everyone agrees that the local effects of gravity are about one-billionth of the positive energy of the local mass.

If the universe-wide effects of gravitational energy are so strongly negative, where are the illustrations and descriptions of that negative energy?



Good points. I agree that it seems incredible that gravitational energy can offset the mass energy of the universe. I don't have a simple explanation or illustration for this. But I have no solid reason to doubt or deny it, either. It may well be true. Physics offers many examples of things which challenge our intuition until we learn how to think about them correctly.

"Science without religion is lame, religion without science is blind." – Albert Einstein

“I am very astonished that the scientific picture of the real world around me is very deficient. It gives us a lot of factual information, puts all of our experience in a magnificently consistent order, but it is ghastly silent about all and sundry that is really near to our heart, that really matters to us. It cannot tell us a word about red and blue, bitter and sweet, physical pain and physical delight; it knows nothing of beautiful and ugly, good or bad, God and eternity. Science sometimes pretends to answer questions in these domains, but the answers are very often so silly that we are not inclined to take them seriously.” – Erwin Schroedinger


This message is a reply to:
 Message 137 by designtheorist, posted 12-17-2011 2:18 PM designtheorist has not yet responded

  
kbertsche
Member (Idle past 1024 days)
Posts: 1427
From: San Jose, CA, USA
Joined: 05-10-2007


Message 178 of 404 (644744)
12-20-2011 12:04 PM
Reply to: Message 170 by designtheorist
12-19-2011 10:43 PM


Re: Is negative energy a mathematical convention or something different?
quote:
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?


Yes, that's the claim. They are offsetting the positive mass energy of the universe with the negative, potential gravitational energy. (Note: both are equally "real" and physical). Dark matter and dark energy must also be added into the equation.

"Science without religion is lame, religion without science is blind." – Albert Einstein

“I am very astonished that the scientific picture of the real world around me is very deficient. It gives us a lot of factual information, puts all of our experience in a magnificently consistent order, but it is ghastly silent about all and sundry that is really near to our heart, that really matters to us. It cannot tell us a word about red and blue, bitter and sweet, physical pain and physical delight; it knows nothing of beautiful and ugly, good or bad, God and eternity. Science sometimes pretends to answer questions in these domains, but the answers are very often so silly that we are not inclined to take them seriously.” – Erwin Schroedinger


This message is a reply to:
 Message 170 by designtheorist, posted 12-19-2011 10:43 PM designtheorist has not yet responded

  
kbertsche
Member (Idle past 1024 days)
Posts: 1427
From: San Jose, CA, USA
Joined: 05-10-2007


Message 179 of 404 (644746)
12-20-2011 12:12 PM
Reply to: Message 177 by designtheorist
12-20-2011 12:03 PM


Re: Reply to kbertsche
quote:

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.


This is a reasonable example. As in Guth's example, if the ropes and generators were absent and the mass shell were allowed to freely contract, then the elements of the mass shell would be accelerated toward the center and would gain kinetic energy. This kinetic energy comes from the gravitational field, the energy of which becomes more negative.

"Science without religion is lame, religion without science is blind." – Albert Einstein

“I am very astonished that the scientific picture of the real world around me is very deficient. It gives us a lot of factual information, puts all of our experience in a magnificently consistent order, but it is ghastly silent about all and sundry that is really near to our heart, that really matters to us. It cannot tell us a word about red and blue, bitter and sweet, physical pain and physical delight; it knows nothing of beautiful and ugly, good or bad, God and eternity. Science sometimes pretends to answer questions in these domains, but the answers are very often so silly that we are not inclined to take them seriously.” – Erwin Schroedinger


This message is a reply to:
 Message 177 by designtheorist, posted 12-20-2011 12:03 PM designtheorist has not yet responded

  
Newer Topic | Older Topic
Jump to:


Copyright 2001-2018 by EvC Forum, All Rights Reserved

™ Version 4.0 Beta
Innovative software from Qwixotic © 2021