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Author Topic: Is there a gravity anti-particle?  (Read 6586 times)

Alex Havers

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Is there a gravity anti-particle?
« on: 22/11/2008 18:16:26 »
Alex Havers asked the Naked Scientists:

Hi, I'm a science teacher from beautiful Vancouver. My class always
listens
, and always comes up with tricky questions...

Here's one: is the force of gravity made up of some kind of particle?  If so, can these particles be interfered with or cancelled out, to make upside-down gravity or zero gravity?  

Thanks!

What do you think?


 

Offline DoctorBeaver

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Is there a gravity anti-particle?
« Reply #1 on: 23/11/2008 13:39:20 »
Some theories postulate the graviton; a particle that mediates the force of gravity. Like the photon, this would be its own anti-particle (in fact I think I am correct in saying that no force-carrying bosons are thought to have anti-particles).
 

lyner

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Is there a gravity anti-particle?
« Reply #2 on: 23/11/2008 15:47:22 »
Just remember that we're not necessarily looking for a 'spatially small bullet'. That could be a very potentially confusing picture of a graviton - or any other energy carrying 'particle', for that matter.
 

Offline lightarrow

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Is there a gravity anti-particle?
« Reply #3 on: 23/11/2008 21:04:45 »
About anti gravity, there is something very strange we could say, but it's not current science, is something at the border between science and speculation. If you want to have a headache I can talk about it a little. (I don't advise it to you, however).
 

Offline Physics Dilettante

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Is there a gravity anti-particle?
« Reply #4 on: 25/11/2008 15:00:52 »
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(I don't advise it to you, however).
You had me at "very strange," but this resolved any doubt. Please continue!
 

Offline lightarrow

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Is there a gravity anti-particle?
« Reply #5 on: 25/11/2008 20:20:17 »
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(I don't advise it to you, however).
You had me at "very strange," but this resolved any doubt. Please continue!
Why should I always get into these things? I should learn to be silent... :-X
Ok, it's my responsibility...

Ehm, the anti-gravity is...

the gravitational field itself!

Explanation (easy part, and OF COURSE, you WON'T ask me to get into the not-easy part too  :)):
1. A static field as electrostatic field has mass. I mean real invariant mass. I don't want to go in the demonstration of it, trust me.
2. At this point one should ask: but then, has the static gravitational field a mass too? The answer is yes, for the same reason. BUT: because of the "minus" sign in the formula of the field, the mass of the field is negative!

At this point we have an incredible amount of problems, because the behaviour of a negative mass' object is "mind blowing" (can I say so?):
a) if you push an object with negative mass, it accelerates in the opposite direction!
b) Two bodies, one with positive mass and the other with negative mass, will move indefinitely one after the other: the positive mass attracts the negative but the negative repels the positive (Yes, I've written correctly!) so the positive will "escape" the other, which will go after it!
...
http://www.negative-mass.com/
http://www.concentric.net/~pvb/negmass.html
Any headache?
« Last Edit: 25/11/2008 20:36:56 by lightarrow »
 

Offline DoctorBeaver

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Is there a gravity anti-particle?
« Reply #6 on: 25/11/2008 20:30:04 »
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the positive mass attracts the negative but the negative repels the positive

A bit like me & women. Women attract me...  :(
 

Offline Bikerman

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Is there a gravity anti-particle?
« Reply #7 on: 25/11/2008 20:34:02 »
There is no proposed 'particle' with negative mass in quantum field theory. I understand what you are proposing (it is basically the Hermann Bondi/Robert Forward proposal) but I remain to be convinced that it has any practical application.
In GR negative mass can also be assumed to be a spatial solution to GR where the stress component of the stress-energy tensor is larger than the mass density - that makes more sense to me....
 

Offline lightarrow

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Is there a gravity anti-particle?
« Reply #8 on: 25/11/2008 20:37:53 »
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the positive mass attracts the negative but the negative repels the positive

A bit like me & women. Women attract me...  :(
...you too?  ;)
 

Offline lightarrow

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Is there a gravity anti-particle?
« Reply #9 on: 25/11/2008 20:40:28 »
There is no proposed 'particle' with negative mass in quantum field theory. I understand what you are proposing (it is basically the Hermann Bondi/Robert Forward proposal) but I remain to be convinced that it has any practical application.
In GR negative mass can also be assumed to be a spatial solution to GR where the stress component of the stress-energy tensor is larger than the mass density - that makes more sense to me....
dark energy?
http://www.negative-mass.com/darkenergy.htm
« Last Edit: 25/11/2008 20:50:27 by lightarrow »
 

Offline Bikerman

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Is there a gravity anti-particle?
« Reply #10 on: 25/11/2008 23:35:22 »
Hmm...I see where you are going but I'm not convinced. OK, we can regard dark energy as -ve energy and we can even posit that it cancels out the positive energy (in the form of energy and mass) in the universe to give a universe of 0 total energy. That appears to me to be very interesting (especially since it would appear to allow the entire universe to be a 'quantum fluctuation' of infinite pay-back time and, thus, give us a mechanism for 'something from nothing'). The pages you cited, however, seem to conclude that the entire energy sum of the observable universe is negative....that seems somehow wrong to me. I'll have to read it in more detail before I can properly critique it....
 

Offline Physics Dilettante

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Is there a gravity anti-particle?
« Reply #11 on: 26/11/2008 01:40:39 »
Any headache?
Actually, no. But, that probably means I don't understand it properly!

I think the papers' discussions about the behavior of negative mass make for fascinating thought experiments. For example, I'd love to see where a bit of negative mass would go, if it we could follow its journey around the universe. I suppose it would have to end up, eventually, wherever gravity is weakest. Care to speculate about where that might be?
 

Offline lightarrow

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Is there a gravity anti-particle?
« Reply #12 on: 26/11/2008 15:34:46 »
I think the papers' discussions about the behavior of negative mass make for fascinating thought experiments. For example, I'd love to see where a bit of negative mass would go, if it we could follow its journey around the universe. I suppose it would have to end up, eventually, wherever gravity is weakest. Care to speculate about where that might be?
If negative mass really exists, it should be located in the space itself among the massive bodies (the gravitational field), but where a piece of concentrated NM would go, it's not very clear to me: it is attracted from positive mass, but repelled from other negative mass, as if positive mass would be positive electric charge and negative mass would be negative electric charge, but with the difference that two positive mass bodies attracts each other instead of repel (as in the case of charge). Or two positive mass bodies attracts themself just because there is negative mass between them (sort of the attraction between two protons if there are electrons in between)? High speculation, here!
 

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Is there a gravity anti-particle?
« Reply #13 on: 26/11/2008 15:46:54 »
Hmm...I see where you are going but I'm not convinced. OK, we can regard dark energy as -ve energy and we can even posit that it cancels out the positive energy (in the form of energy and mass) in the universe to give a universe of 0 total energy. That appears to me to be very interesting (especially since it would appear to allow the entire universe to be a 'quantum fluctuation' of infinite pay-back time and, thus, give us a mechanism for 'something from nothing'). The pages you cited, however, seem to conclude that the entire energy sum of the observable universe is negative....that seems somehow wrong to me. I'll have to read it in more detail before I can properly critique it....
I really don't know how much scientific exactness we can ascribe to these concepts, but I have to admit that the reasonings they have made don't seem blatantly wrong...
 

Offline Bikerman

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Is there a gravity anti-particle?
« Reply #14 on: 26/11/2008 17:28:13 »
I really don't know how much scientific exactness we can ascribe to these concepts, but I have to admit that the reasonings they have made don't seem blatantly wrong...
One of the nicest accessible examples along these lines is the thought experiment of the 'hollow shell', first told to me by a friend on another forum

Imagine a hollow spherical shell of matter. Now we know (Gauss' Law) that spacetime inside the shell is essentially flat and we know that, outside the shell, there is a region of warped spacetime corresponding to the mass of the shell.
Now imagine we 'winch' the shell outwards, so the radius increases.
The volume of warped spacetime remains constant, since the mass is constant. The volume of 'flat' spacetime has increased, and we have put energy into the system.

Conclusion - warped spacetime has less energy than flat spacetime.

Supplementary hypothesis - the entire energy of the universe is 0. (if we assume that perfectly flat spacetime has 0 energy then it follows that warped spacetime has negative energy in direct proportion to mass/energy...)
« Last Edit: 26/11/2008 17:29:53 by Bikerman »
 

Offline lightarrow

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Is there a gravity anti-particle?
« Reply #15 on: 27/11/2008 15:14:49 »
Very interesting, I didn't know it.
 

Offline Bikerman

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Is there a gravity anti-particle?
« Reply #16 on: 27/11/2008 15:36:11 »
Very interesting, I didn't know it.
Yes, it's a nice thought experiment isn't it? The logic seems irrefutable..
 

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