Gravitons... Are there anti-gravitons?

[5614]

The best I can do of imagining 3D is using a 3D graph, like the corner of a cube (like the inside corner of a shoe box or something).

 

But the problem with the whole examle thing is that spacetime is not a flat surface or even a bunch of perpendicular flat surfaces (representing different dimensions) spacetime is everywhere.

 

When trying to get realistic trying to imagine a solid cube of spacetime and warping that... just gets confusing.

 

From which I can conclude that visualising 4D or even 3D spacetime is not something I'm going to spend hours over, because it just aint gonna work!

 

What Atheist was saying is that what you're asking is effectively:

"within GR, can spacetime be warped differently that it is warped within GR"

by differently he is referring to antigravity. The obvious answer is no. GR says spacetime is warped in a specific way. Antigravity would violate this, or put differently antigravity would violate GR.

[[Tycho?]]

Are you guys sure that GR doesn't allow for anti-gravity? The original idea of mass that curves space in the "opposite" way is something I have heard before. Are you sure this sort of curvature cannot yeild an effect opposite to normal gravity?

[swansont]

'']Are you guys sure that GR doesn't allow for anti-gravity? The original idea of mass that curves space in the "opposite" way is something I have heard before. Are you sure this sort of curvature cannot yeild an effect opposite to normal gravity?

 

GR isn't my area, so factor that in to anything I say.

 

I recall reading some of Einstein's papers from the period during which he was formulating GR. The Lorentz contraction of a spinning disk means that the circumference is less than ^{[math]2\pi R[/math]}, which makes the geometry curved, and seemed to be an influence on his idea for GR. To have the opposite curvature, you would have to have the circumference be longer than ^{[math]2\pi R[/math]}. The view starting from SR, using this example, doesn't allow for that. And I don't think positive mass allows for the opposite curvature.

[5614]

I remember reading something like what Swansont said.

 

And I don't think positive mass allows for the opposite curvature.

I agree. And just to state the obvious as far as we know negative mass does not exist.

[ydoaPs]

I remember reading something like what Swansont said.

 

I agree. And just to state the obvious as far as we know negative mass does not exist.

if we could play with the Higgs field, could we not produce negative mass?

[RyanJ]

if we could play with the Higgs field, could we not produce negative mass?

 

Thought negative mass was actually impossible? If it were possible I'd like to have some, it would have some interesting properties such as it accelerating in the opposite direction to which it was pusched ([math]F=ma[/math]), [math]E=mc^2[/math] would have a huge negative value (negative energy?!)... confusing.

 

Cheers,

 

Ryan Jones

[[Tycho?]]

GR isn't my area' date=' so factor that in to anything I say.

 

I recall reading some of Einstein's papers from the period during which he was formulating GR. The Lorentz contraction of a spinning disk means that the circumference is less than [sup'][math]2\pi R[/math][/sup], which makes the geometry curved, and seemed to be an influence on his idea for GR. To have the opposite curvature, you would have to have the circumference be longer than ^{[math]2\pi R[/math]}. The view starting from SR, using this example, doesn't allow for that. And I don't think positive mass allows for the opposite curvature.

 

Negative mass? I'm not sure if this even has a definition in modern physics, but that is how I've heard it reffered to for these anti gravity things. And what has negative mass? Well "exotic matter". And whats that? Well, .... its exotic.

 

Is there any reason to believe this "exotic matter" (whether it is possible or not) could actually have such an effect? If negative mass exists, would it have an opposite effect to normal gravity?

[Ragib]

It is impossible to have negative mass, or negative energy. Maybe possible to have an antigravity which can repel as well as attracts but that remains to be seen. You have to think what mass and energy actually are. They are what Makes everything! they are the building blocks of things. You cant build a house with -500 bricks.

[insane_alien]

thats because you need way more than 500 negative bricks. with -500 you might have -half a wall.

[Edtharan]

What about the energy level between the plates in the casimir effect? The nature of the plates means that there is less energy between the plates than ther is outside of them. And if out side of the plates is considdered to have 0 energy, then this would constitue negative energy (although it would be so small that the mass of the plates and aperatus would swamp it)?

[Ragib]

either way, dusnt matter, -500000 bricks still won't get you a house, maybe a negative house, but not a house. The building blocks of matter must have a positive mass, a building block with 0 mass is non existant matter, mass with a negative value is like..is more not there then not there!!

[swansont]

What about the energy level between the plates in the casimir effect? The nature of the plates means that there is less energy between the plates than ther is outside of them. And if out side of the plates is considdered to have 0 energy, then this would constitue negative energy (although it would be so small that the mass of the plates and aperatus would swamp it)?

 

 

The energy outside is infinite by some calculations. We just subtract the infinity and call it zero, because most of the time that's the convenient thing to do. What we measure as energy is a relative quantity — it's always an energy difference between two states that we measure — so the choice of zero is arbitrary, and you usually choose the value that makes the calculation easiest. Since the infinity is not an energy reservoir that can be tapped, it makes no sense to call it anything but zero.

[5614]

RyanJ:

 

Although if you consider [math]E^2 = (mc^2 )^2 + (pc)^2 [/math] then a negative mass would just be squared out.

 

But I still don't think negative mass exists.

[Dark Photon]

light doesnt experience time, only motion through spacetime, as all motion is shared.

[Ragib]

RyanJ:

 

Although if you consider [math]E^2 = (mc^2 )^2 + (pc)^2 [/math] then a negative mass would just be squared out.

 

But I still don't think negative mass exists.

 

The reason a negative mass would just be squared out by this equation is due to the fact that when Eienstein came up with this' date=' he never intended there to be a negative mass. Otherwise [math']E = mc^2 [/math] would have been different, because, say you set your negative massed particle to rest, one equation gives negative energy, the other gives a positive one. You can't just simply square then square root to get a positive answer, thats cheating . And you can't just say, [math]E^2 = (mc^2 )^2 + (pc)^2 [/math] is the more correct version and [math]E = mc^2 [/math] simplified version because Eienstein Assumed there wasnt negative mass. [math]E^2 = (mc^2 )^2 + (pc)^2 [/math] includes kinetic energy as well, but that doesn't make [math]E = mc^2 [/math] wrong when a particle is at rest.

[5614]

[math]E = mc^2[/math] is not wrong, but it can only be applied in certain circumstances. For example it cannot be used for a photon. If negative mass existed (it doesn't, but say it did) then this would just be another case when you can't use the simplified version of Einstein's equation, nothing wrong with that.

 

Einstein's forumla was not [math]E = mc^2[/math]. Einstein said that [math]E^2 = (mc^2 )^2 + (pc)^2[/math] and he did realise that the powers would allow for a postive or negative answer. He did not rule out the possibility of negative energy. I don't know his thoughts on negative mass.

 

You can't just simply square then square root to get a positive answer, thats cheating

I see what you mean it is kind of cheating. But using that method is succesful in many physics and statistics formulae. It works.

[the tree]

He did not rule out the possibility of negative energy. I don't know his thoughts on negative mass.

Considering one is just a different manifestation of the other, surely he wouldn't have ruled out negative mass either?

[RyanJ]

So the equations do not strictly forbid negative mass (and negative energy from existing)? I also agree with 5614, I don't think there is negative mass.

 

Too me it makes no sence that something can have less then no mass.

 

Cheers,

 

Ryan Jones

[Ragib]

Personally, i dont think there is negative mass, but you never know, less than even 600 years ago Negative numbers were being debated to exist. How could you have less than nothing!?!?! And though negative numbers aren't physically possible, eg You cant have -5 of anything, its still been really useful in calculations. Same for the imaginary unit.

[abskebabs]

I don't think I can make any useful comment on this at the moment as I feel my knowledge of physics is insufficient at the moment, however; I have found a powerpoint presentation on the internet talking about negative energy, hawking radiation and black holes. Make of it what you will.

http://www.uta.edu/physics/main/resources/stpr/ppt/Presentation2-7.ppt

[GuardianTech]

It's like Einstein said, you can't claim you understand something, until you can explain it to your grandmother.

 

We live in a universe of opposites, following logic, there would have to be an opposite to a graviton...

[timo]

We live in a universe of opposites' date=' following logic, there would have to be an opposite to a graviton...[/quote']

Just like the anti-photon, the anti-zero and the frightening anti-rabbits

No, honestly. The question about anti-gravitons really depends on the definition of the term. Normally, anti-particles are partners with exactly the same properties except for a sign-inverted electrical charge. So if you say that particles with a zero electrical charge (like the gravitons) are their own anti-particles or say that they don´t have any anti-partner is pure semantics for that definition of an anti-partner.

 

And while I´m at posting in here I can as well correct a typo in a former post: When I talked about "dark matter" giving rise to an acceleration in the universe´s expansion the correct term would of course have been "dark energy".

[GutZ]

So what the hell an electron spinning or with opposite spin would give it a positive charge?, I always thought they had the same spin with positive charge, but I guess that doesn't make sense.

 

Damn it, I hate you all, and your understand of this. I guess it takes more then 2 months.

[Klaynos]

An electron can have +1/2 or -1/2 spin, this does not effect their charge. Positrons can also have +1/2 or -1/2 spin.

[Ragib]

I think people are confused. Photons, gravitons, regardless, are not their own anti particles. It is just that it is impossible to tell them APART from their anti particles. If they were their own anti particles, photons in laser would destroy each other, which they don't. However, if we had a method of making anti-photons, they would. Just because we can tell them apart, doesn't mean their all the same.