1. ## What is anti-gravity?

Can someone please provide the mainstream definition of anti-gravity?

2. Since there is no evidence for the concept of anti-gravity, your question is meaningless.

3. OK ... what is the Ricci Tensor? Is that the tensor that defines the curvature of the topology in GR?

4. Originally Posted by tommac
Can someone please provide the mainstream definition of anti-gravity?
It is a figment of your imagination.

5. Originally Posted by tommac
OK ... what is the Ricci Tensor? Is that the tensor that defines the curvature of the topology in GR?
http://en.wikipedia.org/wiki/Ricci_curvature

Topology does not have curvature per se. Curvature is associated with geometry. Two manifolds with very different curvature can be topologically isomorphic (homeomorphic).

Rather than asking a bucket full of questions that you don't understand with answers beyond your present state of knowledge, you might try reading a no-kidding book and doing some study. For these sorts of questions a good book is Gravitation by Misner, Thorne and Wheeler. You might have to go back to a bit more basic mathematics before you fiind yourself ready to tackle differential geometry.

6. Originally Posted by DrRocket
Gravitation by Misner, Thorne and Wheeler. You might have to go back to a bit more basic mathematics before you fiind yourself ready to tackle differential geometry.
Fortunately MT&W has identified easy and advanced parts of every chapter.

7. Originally Posted by antoniseb
Fortunately MT&W has identified easy and advanced parts of every chapter.
They have identified two tracks in the book. One more rigorous than the other.

Neither would be a cake walk for someone who understands little mathematics and physics.

"Easy" here is indeed a relative term.

However, there is no royal road to understanding and MTW is as good as it gets.

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Basically, anti-gravity is removing the forces of gravity.

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Now isn't this the Q&A section? What about string/superstring theory with specific regards to gravitons? What if a higher order of sentience were capable of "transiting" gravitons between their naturally linked branes? Would mutability possibly not then be a very intrinsic trait of gravity as we know it? I'm not sayin' to go chasing fairy tales, but sheesh, show me your answer for the quantum field theory problem already so we can all be learned men.

10. ## self fulfulling

Gravity: A mutual attraction between objects of substance.

Anti-Gravity: A mutual attraction of thoughts with zero substance

I wonder if there has ever been a thread specifically for those who need to go back and study a bit, to quote:
Originally Posted by DrRocket

Rather than asking a bucket full of questions that you don't understand with answers beyond your present state of knowledge, you might try reading a no-kidding book and doing some study. For these sorts of questions a good book is Gravitation by Misner, Thorne and Wheeler. You might have to go back to a bit more basic mathematics before you find yourself ready to tackle differential geometry.
Originally Posted by antoniseb
Fortunately MT&W has identified easy and advanced parts of every chapter.
There are a lot of resources on this forum for those who might want to take DrRocket's advice. Perhaps I should start one? What do you think?

Oh, and welcome to the forum asbakwod and MrPibb
Last edited by sirius0; 2009-Nov-24 at 06:59 AM. Reason: Add question and politeness

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Originally Posted by sirius0

Gravity: A mutual attraction between objects of substance.

Anti-Gravity: A mutual attraction of thoughts with zero substance

Sorry to the OP for taking this thread as seriously as you apparently did.
Hilarious! But really, this guy may be fishing for kelp, but so what? If the good doctor above is continually disgusted by this guy's lack of knowledge, why bother to respond? What was in the previous post, something about a navel? Great for humor, but if you are wasting your time, then don't bother wasting your time?!

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But in retrospect, I wonder if anti- gravity is strong enough to push a thread into oblivion?

13. Tolerance and understanding. The need to be compassionate and to treat others as you would expect to be treated yourself... Single minded pig headiness is not a crime. The question is not silly. We have seen it before. Its been altered a bit but its the same idea. It has not been answered. That might be because it can not be. No such animal does exist. There is no anti-gravity. I will accept that you could remove yourself from the force of gravity. Its still there. There does not seem to be any proof of a force that could be construed as anti-gravity. No example of a white Hole has been found. No change in the procession of time has been found. No edge of the Universe, No Dark Energy, No dark mater... Higgs particle... Oops no hold the phone, That last one could be wrong... Its going again.LHC
As a mathematical concept it might be a feasible probability to reverse time or the force of gravity or both...In the real nuts and bolts world that we live on..Its not .
To those of you that find it amusing to ridacule... don't.
Use the science.It is why we are here... Its both real and kinder

14. "What is the Ricci Tensor?" to me seems one of those questions, where if you have to ask, you probably won't understand the answer.

Originally Posted by MrPibb
Hilarious! But really, this guy may be fishing for kelp, but so what? If the good doctor above is continually disgusted by this guy's lack of knowledge, why bother to respond? What was in the previous post, something about a navel? Great for humor, but if you are wasting your time, then don't bother wasting your time?!
Welcome to BAUT, MrPibb. There's quite some history from the person posting this question, and that's what some of the other posters may be referring to. This may not be obvious to someone who just joined the board.

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Originally Posted by slang
"What is the Ricci Tensor?" to me seems one of those questions, where if you have to ask, you probably won't understand the answer.

Welcome to BAUT, MrPibb. There's quite some history from the person posting this question, and that's what some of the other posters may be referring to. This may not be obvious to someone who just joined the board.

Thanks all for the welcome, and slang, I had some idea of that beforehand, and I do understand the frustration here, but on the other hand, I think I can identify with poster in trying to (sometimes vainly) visualize things where 1) one must entrench themselves in the math to gain even a subtle understanding, or 2) problems which lie well beyond the human(or my) capacity for understanding given our(mostly mine) current levels of knowledge. The only point to my thread drift is that the pursuit of knowledge, though a necessity for being well regulated and empirical exists, should not be discouraged in any form. Given the mathematical divergences that present themselves in our current theory, we may eventually find our understanding now to be as antiquated in its understanding as the "plum- pudding" atomic model. But I suppose that would indeed not be a suited discussion for a "mainstream" thread as it were.

Sorry for the rant, and I do hope for future conversations to be a little more pointed... cripes...

16. MrPibb, welcome to BAUT, please take some time to read the rules for posting linked at the bottom of this post.

Q&A is for asking about and receiving answers on the Mainstream of Astronomy. 'Meta' discussion of the type you have posted should be confined to the Forum Introductions and Feedback forum

General note to all posters. Stick to answering questions. If you have a problem with a post or poster then report using the reporting triangle.
Attacks on other posters will result in Moderator Action

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An answer to the original question which completely ignores general
relativity is that antigravity, if there is or were such a thing, would be
a repulsive gravitational force between matter. Similar to how opposite
electric charges attract and similar electric charges repel each other
by the electric force, similar gravitational masses attract each other,
and opposite gravitational masses would repel each other.

That antimatter actually has this anti-mass and anti-gravity property is
a pet hypothesis I have been nurturing since the mid-1970's. It should
be tested in an experiment wth anti-hydrogen at CERN in about 2015 at
the earliest. It is unlikely to be a correct hypothesis, but one hopes.

-- Jeff, in Minneapolis

18. Originally Posted by Jeff Root
SAn answer to the original question which completely ignores general
relativity is that antigravity, if there is or were such a thing, would be
a repulsive gravitational force between matter.
imilar to how opposite
electric charges attract and similar electric charges repel each other
by the electric force, similar gravitational masses attract each other,
and opposite gravitational masses would repel each other.

That antimatter actually has this anti-mass and anti-gravity property is
a pet hypothesis I have been nurturing since the mid-1970's. It should
be tested in an experiment wth anti-hydrogen at CERN in about 2015 at
the earliest. It is unlikely to be a correct hypothesis, but one hopes.

-- Jeff, in Minneapolis
Wouldn't repulsive gravity be more like a property of negative mass, though? Or did I just make that up?

19. Originally Posted by Fiery Phoenix
Wouldn't repulsive gravity be more like a property of negative mass, though? Or did I just make that up?
Negative mass would be even more weird.

Negative mass would accelerate to the left when you push it to the right.

20. Originally Posted by Fiery Phoenix
Wouldn't repulsive gravity be more like a property of negative mass, though? Or did I just make that up?
It's a little more complex than just having negative mass. Just looking at Newtonian gravity:
F = G*m1*m2/r^2
A1 = F/m1 = G*m2/r^2
A2 = F/m2 = G*m1/r^2

A negative mass object would experience a force in the opposite direction...but would still accelerate in the same direction in a gravity field around a positive mass. It would however push either positive or negative masses away from it, and a mass and an "antimass" paired together would accelerate indefinitely.

Originally Posted by Jeff Root
That antimatter actually has this anti-mass and anti-gravity property is
a pet hypothesis I have been nurturing since the mid-1970's. It should
be tested in an experiment wth anti-hydrogen at CERN in about 2015 at
the earliest. It is unlikely to be a correct hypothesis, but one hopes.
And I'll give my standard objection to this:
Gravity is actually proportional to *mass-energy*, not just mass.

The mass of a proton is not just that of its component quarks, it is in fact mostly due to the binding energy of those quarks. The binding energy of an antiproton should be the same, so if the quarks themselves had negative mass, we would measure a notable difference in mass between protons and antiprotons...the antiprotons as a whole still having positive mass.

If antiprotons actually have net negative mass-energy, that poses different problems. In pair production from a photon, the system would lose two protons worth of mass-energy. Proton-antiproton annihilation would add that amount of energy to the system. A container full of 1 kg of matter and 1 kg of antimatter would start with zero net gravitational effect from its contents, and would gain 2 kg as the two annihilated and it absorbed the resulting gamma radiation. You would have a closed system changing in mass-energy.

Also, if they have negative mass they should react in an opposite way to electromagnetic forces. Despite being electrically negative, anti-mass antiprotons should be attracted to negative charges. They should also bend the "wrong" way in magnetic fields. This sort of behavior would be quite difficult to miss. This should also allow you to do things like construct perpetual motion machines...

And in fact, measurements have been done, and they all point to an actual mass equal to that of protons. Jeff, I'm not sure why you reject the measurements that have been made.

21. Originally Posted by Jeff Root
An answer to the original question which completely ignores general
relativity is that antigravity, if there is or were such a thing, would be
a repulsive gravitational force between matter. Similar to how opposite
electric charges attract and similar electric charges repel each other
by the electric force, similar gravitational masses attract each other,
and opposite gravitational masses would repel each other.

That antimatter actually has this anti-mass and anti-gravity property is
a pet hypothesis I have been nurturing since the mid-1970's. It should
be tested in an experiment wth anti-hydrogen at CERN in about 2015 at
the earliest. It is unlikely to be a correct hypothesis, but one hopes.

-- Jeff, in Minneapolis
Where I really would like to ask is how would the expansion of the universe be different from this? I understand that mass isnt pushing everything apart but could empty space or dark energy have such an effect accelerating all matter away from it.

NOTE: I am not suggesting this ... just asking the question of how different would this be, as an attempt to understand the expansion of the universe as well as zero point energy.

22. Originally Posted by DrRocket
Negative mass would be even more weird.

Negative mass would accelerate to the left when you push it to the right.
where can I buy some of this stuff?

23. Originally Posted by cjameshuff
It's a little more complex than just having negative mass. Just looking at Newtonian gravity:
F = G*m1*m2/r^2
A1 = F/m1 = G*m2/r^2
A2 = F/m2 = G*m1/r^2

A negative mass object would experience a force in the opposite direction...but would still accelerate in the same direction in a gravity field around a positive mass. It would however push either positive or negative masses away from it, and a mass and an "antimass" paired together would accelerate indefinitely.

And I'll give my standard objection to this:
Gravity is actually proportional to *mass-energy*, not just mass.

The mass of a proton is not just that of its component quarks, it is in fact mostly due to the binding energy of those quarks. The binding energy of an antiproton should be the same, so if the quarks themselves had negative mass, we would measure a notable difference in mass between protons and antiprotons...the antiprotons as a whole still having positive mass.

If antiprotons actually have net negative mass-energy, that poses different problems. In pair production from a photon, the system would lose two protons worth of mass-energy. Proton-antiproton annihilation would add that amount of energy to the system. A container full of 1 kg of matter and 1 kg of antimatter would start with zero net gravitational effect from its contents, and would gain 2 kg as the two annihilated and it absorbed the resulting gamma radiation. You would have a closed system changing in mass-energy.

Also, if they have negative mass they should react in an opposite way to electromagnetic forces. Despite being electrically negative, anti-mass antiprotons should be attracted to negative charges. They should also bend the "wrong" way in magnetic fields. This sort of behavior would be quite difficult to miss. This should also allow you to do things like construct perpetual motion machines...

And in fact, measurements have been done, and they all point to an actual mass equal to that of protons. Jeff, I'm not sure why you reject the measurements that have been made.
My thought that I am trying to rule out was that if empty space ( or maybe one of the following: cosomlogical constant, zero point energy, dark energy ) had an intrinsic tendency to accelerate mass away from it. And only when energy exists in quanties above the cosmological constant would this repulsive energy be negated as the sum of the curvature ( Ricci tensor) would be 0.

Please dont knock this into ATM as I am not going to defend that ... but I dont understand why this wouldnt work.

24. Originally Posted by tommac
My thought that I am trying to rule out was that if empty space ( or maybe one of the following: cosomlogical constant, zero point energy, dark energy ) had an intrinsic tendency to accelerate mass away from it. And only when energy exists in quanties above the cosmological constant would this repulsive energy be negated as the sum of the curvature ( Ricci tensor) would be 0.

Please dont knock this into ATM as I am not going to defend that ... but I dont understand why this wouldnt work.
It won't work because it makes no sense at all.

Nothing is "accelerating mass away from it". What is happening can be explained in terms of expansion of a space-like slice of space-time with distance measured from the metric inherited from the full space-time.

There is no such thing as the "sum of the curvature", although there is such a thing as Ricci curvature.

You are just throwing out words, with no apparent understanding of their meaning. It is not ATM. It is just word salad.

If you want to ask sensible questions or make meaningful conjectures you are simply going to have to learn some real physics, with real mathematics. Some references have been provided for you in earlier posts. No go read them.

25. Originally Posted by tommac
My thought that I am trying to rule out was that if empty space ( or maybe one of the following: cosomlogical constant, zero point energy, dark energy ) had an intrinsic tendency to accelerate mass away from it. And only when energy exists in quanties above the cosmological constant would this repulsive energy be negated as the sum of the curvature ( Ricci tensor) would be 0.

Please dont knock this into ATM as I am not going to defend that ... but I dont understand why this wouldnt work.
It doesn't work because if you take a look at the observations the observations don't match what you are suggesting.

Nothing is being moved in the universe when we talk about cosmic expansion. Relative to other objects everything is in the same position just the distances are the same. You can not think of it classically with a directional force unless we where the centre of the universe.

The analogy that dark energy = anti gravity falls down on this point. While they have some similar properties they are not the same.

Again anti-gravity should follow an inverse square law. Dark Energy has an effect that is observed to be linear in nature.

$4\pi r^{2} != rx \therefore Anti-gravity != Dark Energy$

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First we have to understand gravity itself. We don't. We can describe some of its effects and associations and they are fairly easy to understand as effects and associations but that's different from understanding gravity itself. Many people mistake understanding descriptions of effects and associations with understanding causes. Some of the primary effects and associations of gravity that can be described are that masses move through space and are attracted in their motion to each other. To understand gravity completely we have to have a complete understanding of all the elements from which the effects and associations emerge. A crucial instance is that we have to understand matter which has a primary association with mass. Our descriptions of matter (based as they are on our flawed and incomplete ability to observe it and interpret our observations of it) have fundamental flaws that result in theories that, even the best of which, are at present mutualy exclusive.

Since we don't fundamentaly understand matter we can't understand its motion and since a fundamental characteristic of motion is the space in which to move we don't understand space either.

Absent those fundamental understandings we have a way to go before understanding gravity let alone anti-gravity. If we did understand gravity well enough to either confirm anti-gravity or prove it impossible would not neccesarily stem from an absolutely consistant understanding of matter, motion and space. If we did have that we would know it (some of us anyway). At present we don't know enough to either strictly confirm or deny anti-gravity. At present we are absent conclusive evidence either way (though some with less strict standards of conclusive evidence would differ). But absence of evidence is not evidence of absence.
Last edited by aastrotech; 2009-Nov-25 at 09:38 AM.

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Well, I guess it must be hard for you to get to work. How do you manage to type using a computer, since it relies on so many principles that we do not understand?

28. What is the difference between a ricci curvature in empty space vs the riccie curvature in nearly empty space? How can one describe the minimum amout of curvature via the terms of ricci curvature?

Originally Posted by DrRocket
It won't work because it makes no sense at all.

Nothing is "accelerating mass away from it". What is happening can be explained in terms of expansion of a space-like slice of space-time with distance measured from the metric inherited from the full space-time.

There is no such thing as the "sum of the curvature", although there is such a thing as Ricci curvature.

You are just throwing out words, with no apparent understanding of their meaning. It is not ATM. It is just word salad.

If you want to ask sensible questions or make meaningful conjectures you are simply going to have to learn some real physics, with real mathematics. Some references have been provided for you in earlier posts. No go read them.

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Originally Posted by Kwalish Kid
Well, I guess it must be hard for you to get to work. How do you manage to type using a computer, since it relies on so many principles that we do not understand?
Because I understand the association of pressing keys with the effect of letters appearing on the screen. In the case of the typing I don't need to understand the cause. If I want to understand the cause well enough to do more than type I have to understand more than the association and the effect. It's kind of like understanding Bohr's atom is a good enough understanding of the atom as well as convienient to understand chemistry but insufficient to understand nuclear physics. Although nuclear physics is a more accurate description of the atom than Bohr's atom it is awkward to use for chemistry. Likewise nuclear physics specificly as applied under the Copenhagen interpretation (a convention) is convienient to understand nuclear physics but is insufficient to understand gravitational physics. Gravitational physics does not as yet exist as does nuclear physics. Our understanding of gravity completly falls apart under nuclear physics as applied under the Copenhagen interpretation.
Last edited by aastrotech; 2009-Nov-25 at 09:47 PM.

30. Originally Posted by WayneFrancis
Nothing is being moved in the universe when we talk about cosmic expansion. Relative to other objects everything is in the same position just the distances are the same.
What is the difference of two things moving away from each other or the space between two objects are moving away from each other?

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