# Is this possible?

Well, but it's not as though helium, or other lighter-than-air gases have no mass, or weight, they still have 'weight' as in positive gravity attraction.

While that is true I think people tend to think of weight as the net downward force you apply to the surface of the earth, or basically, what the scale says when you stand on it. If you think of it that way, the balloon has a negative weight.

If by weight you mean the force of gravity between the balloon and the earth, then you have a very different picture.

Also, negative mass would create negative weight because it would be repelled by positive mass (supposedly, if it weren't, why would the mass be negative?).

It's negative because it has less than no mass, like a rip in space. However, I really don't think it would be possible...if there were signifigant amounts of negative matter wouldn't it change the universal amount of matter, then we'd need *alot* more dark matter to make up for it.

No negative mass.

If you think of mass as that which works against acceleration, there does not seem to be a possibility for negative mass.

If you think of mass as that which works against acceleration, there does not seem to be a possibility for negative mass.

Oooh, I hadn't even thought of that. A negative mass would have negative inertia and when moving, negative momentum. Yeah, I think negative mass is too screwy to even think about.

Are the formulas such as p = mv based on the assumption of positive mass? I mean, anything developed from there would obviously be wrong, correct?

No, a few have been found in special reactions.

Do you think you could find a supporting reference?
I don't mean to offend, but I don't want to base a major shift in viewpoint on an unsupported assertion from "someone on the Internet".

Is it good question - about negative mass?
Why?
What is atribut of good question?
Which questions are more attractive: trivial, or magic complicate?

Emil