Massless universe?

1. Mar 9, 2008

Xbehave

How would a universe with a total mass of zero behave?
By comparing the expected result for a zero mass universe, can we be sure that our universe has total mass?

2. Mar 9, 2008

Mike Cookson

A universe with zero mass, if you mean a universe where the particles are masses would be dull. There would be no interaction due to gravity as it wouldn't exist. It would also take no energy to accelerate anything to any speed at any rate of acceleration. There are just simple effect so. Without mass lot, if not most, or the physics we know would be useless or not exist.

3. Mar 10, 2008

Xbehave

actually i meant a universe where we exist along side negative-matter, to give a total mass of zero, but i wondered if there was a solution for general relativity in this situation more than the physical implications of the fact there could be no matter in the universe.

4. Mar 11, 2008

jnorman

this is a valid question, and is tied directly to "where is the anti-matter?"

5. Mar 11, 2008

Mike Cookson

Ahhhh, right ok, makes slightly more sense.

The only issue now is if you consider this negative-matter to be anti matter then at some point anti-matter and matter will eliminate each other leaving nothing...

6. Mar 12, 2008

Xbehave

anti-matter is electrically the opposite of normal matter, and it can be shown that any anti-matter that collided with its particle.
this negative matter would be the gravitational opposite of normal matter, im not sure if it would be destroy on contact with its postive-particle. but as the same processes that form galaxies would push the negative-matter out it wouldn't be found inside galaxies, only between them (or visa-versa if a galaxy was formed by negative matter). Also as neg-mass-particles and normal ones always repel eachother, it would take a very energetic event to cause a colision.

But my main question was if a solution to general relativity existed for a massless universe, and if this could describe our universe?

7. Mar 12, 2008

Wallace

Anti-matter is not 'negative' matter. It still has the same gravitational effect as regular matter, i.e. it attracts and is attractive to all other matter (whether 'anti' or normal). The only way to get a zero mass universe is to have nothing in it at all.

Edit: There is a solution to GR for a massless Universe (in a way) that is known as the Milne Model. Google/Wiki that if you are interested. It has nothing to do with anti-matter though.

8. Mar 12, 2008

Marco_84

correct wallace....
and to be more correct, when matter and anti-matter annhilate they transform in radiation energy (photons)....

marco

9. Mar 12, 2008

Mike Cookson

I bow down to superior knowledge, thinking about it now there would be a release of energy...a substantial one too...my bad. I'm just a humble electronic engineer ;)