# Consequences of a negative mass universe

1. Oct 19, 2012

### olso4051

If a universe existed where all the mass was negative but everything else was the same as our universe in terms laws of physics what would happen? To be more specific it appears that all the mass would repel each other, would negative mass atoms form, would these particles absorb or emit light? What else might be interesting about this universe?

2. Oct 19, 2012

### phinds

What is "negative mass" ? Anti-matter, which is the only thing I can think of that you might mean, does not have negative mass.

3. Oct 20, 2012

### olso4051

Well right it would be a hypothetical situation, and you're right it would not be anti-matter. In every equation you can think of the mass would have a negative value, what would happen?

4. Oct 20, 2012

### phinds

If unicorns existed, they would have horns.

I mean, really ... if you want to just make stuff up, then make up whatever characteristics you like. It has nothing to do with physics.

5. Oct 20, 2012

### Staff: Mentor

It's important to realize that our equations describe the real universe. I wouldn't expect negative mass to still use the equation F=MA do relate force, mass, and acceleration. For example, if you put -M in there, does that mean you are applying a negative force now? What does it physically mean? Is the acceleration negative?

E=MC2, how could you possible have negative energy? What does that even mean?

See what I mean? It just leads to nonsense.

6. Oct 20, 2012

### mrspeedybob

Gravity would be repulsive, kind of...

F=GmM/r2 so if both masses were negative then F would still be positive, however...

F=ma so a=F/m

F would still point downward but since m is negative a would be negative so an object would accelerate in a direction opposite the force, so upward.

I suspect the same logic would apply to the other forces which hold stuff together so stable matter would not be possible in a universe with negative mass. In such a universe there would be no one to wonder what would happen if the sign of mass were opposite.