# Anti-Mass and Speed of Light

#### T.O.E Dream

So some questions have been made around why does the speed of light have to be the cosmic speed limit. well to answer this, any object with zero rest mass moves at c (read more about invariant mass for details). but here's another question: Mass has always been referred to as positive like +2 kg or +3 kg since after all what can weigh less than nothing, but what happens if something does? some thing like Anti-mass. so if something weighs -1kg then if we complete the equation E=mc2 then we should get -1x300,000,000 x 300,000,000 which is -90 000 000 000. this means two things: firstly, there is negative energy which i have no idea does. secondly, this might be able to move faster than the cosmic speed limit.
What do you think?

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#### Mentallic

Homework Helper
The only way I would be able to fathom anti-mass is if the object itself moves against gravity. But then again, depending on your frame of reference, this object will still have +1kg mass anyway, so it should be that its $v < c$

#### T.O.E Dream

Well. according to general relativity a mass warps spacetime and so creates gravity. What happens if instead of an object warping of spacetime to create gravity if it warped it so that it sort of avoids the affects of gravity? i have no idea, just throwing stuff out there.

#### T.O.E Dream

but either way it doesn't change it's mass it just doesn't feel gravity so i'm wrong

#### Mentallic

Homework Helper
This is just being thrown out there, but what if the anti-mass were to bend the space-time in the opposite direction? I can't think of how this anti-mass would interact with other masses, but it might be possible that the mass and anti-mass both repel each other.

#### T.O.E Dream

again, i dont think it might actually change its actual mass it might though create anti-gravity which i think is almost just as rewarding.

#### T.O.E Dream

its all about manipulating spacetime in different ways that we havent yet discovered, it might be out there in the universe (or multiverse) and it might actually explain most the phenomena that we encounter. in fact im hoping i might grow up and actually write a paper on Spacetime that might lead us to explain the forces of the universe.

#### T.O.E Dream

also i have opened another thread talking about the manipulation of spacetime.

#### Bob S

We believe that there are more galaxies than antigalaxies, but we do not know how to determine which is which. We have not discovered any pair of galaxies that have mutual repulsive gravitational force. We do know that when a galaxy passes through an antigalaxy, based on our experiments with antimatter (e.g., positrons and antiprotons), they annihilate one another. I suspect we would see extra gamma rays, 510 keV and 67 MeV, from positron annihilation and pi zero decay. But unfortunately, positrons are ubiquitus in electromagnetic showers, and pi zeros do not need antimater to create them. When protons annihilate with antiprotons, we get lots of pions of all flavors, including pi zeros. We have created lots of antimatter like antiprotons ( but less than a microgram), but other forces (electromagnetic) are so high, we cannot weigh them. Antihydrogen and antineutrons offer the best hope. Is dark energy related to antimatter?

#### T.O.E Dream

probably, but on one point we already know what antimatter is (i.e.positron).
we don't know if dark energy exists but it might explain some weird things.
you probably know more about it than i do.

#### cragar

i dont know anti-mass is kinda hard for me to comprehend but maybe it exists
i dont know if we could escape the effects of gravity cause it permeates space to an
infinte distance. and im just wondering what would a place with anti-gravity be like.

#### Dmitry67

I think you are mixing antimatter (rare, but ordinary thing) and exotic matter.
antimatter has positive mass!!! like an ordinary matter!!!
exotic matter should have negative mass... but the only candidate now is a slit between 2 casimir plates.

#### Fredrik

Staff Emeritus
Gold Member
What we call the "mass" of a particle is defined as the possitive square root of m2. So mass is positive by definition, at least in (special) relativistic quantum mechanics, where the different particle species correspond to irreducible representations of the covering group of the Poincaré group. Those representations are labeled by the values of spin and m2. There are representations with m2<0 (i.e. with an imgaginary mass), but there are good reasons to believe that particles corresponding to such representations don't exist in the real world. Those particles are called tachyons and they would only be able to move faster than the speed of light.

So I don't think "exotic matter" can have a negative mass. It might have a negative pressure though, i.e. it would suck.

#### Dale

Mentor
Here is a link on http://en.wikipedia.org/wiki/Exotic_matter" [Broken]; negative mass should still fall down. But since you are still learning the math you need to properly understand physics, I would recommend that you stay away from this kind of speculative stuff for now. Learn the basic laws of physics which are experimentally validated. Once you have a strong foundation in the things that we know about how the universe works then you can start stepping out into things that we do not know.

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