On 20060317, John Bell <john.bell@accelerators.co.uk> wrote:
> chronon wrote:
>> island wrote:
>>
>> >
>> > No, Galileo showed that some handy massive objects fall "down" at the
>> > same rate, regardless of clear differences in their masses. This can be
>> > generalized to other massive objects, but relativity tells us that a
>> > negative mass object would curve spacetime in a way that bends geodesics
>> > away from it... which means that negative mass would have negative
>> > presssure and produce an "antigravitational effect" like a positive
>> > cosmological constant.
>>
>> True, a negative mass would repel other objects from it, but it would
>> still be attracted towards a positive mass. If you had one positive and
>> one negative mass of the same magnitude then the positive mass would be
>> repelled but the negative mass would follow it, and the pair would
>> constantly accelerate.
>>
> Now that is an interesting conclusion, since you have just 'invented' a
> perpetual motion machine from which energy can be extracted for
> nothing.
>
> This begs the question: what mistake have you made in the physics to
> arrive at such a verboten (absolutely forbidden) conclusion?
>
> (I think I know the answer, but want to see if you guys can work it out
> for yourselves)
Nah, energy is conserved. The negative mass has a negative kinetic energy...

Aaron Denney
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