## Negative Mass

Interesting physics explained with many thought experiments and little math.
SsDd
Science Officer
Posts: 113
Joined: Sat Dec 05, 2009 1:06 am
AKA: Abhi
Location: Michigan Tech

### Negative Mass

The lecture video is embedded below.

Additionally, slides used in the lecture are embedded below, or can also be downloaded directly from here.

Questions after the lecture? Please feel free to post them in the same thread.

Click to play embedded YouTube video.

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yakovina_ivan
Asternaut
Posts: 4
Joined: Wed Nov 24, 2010 2:23 pm

### Re: Negative Mass

Can a graviton (which is still not prooved to exist) have a negative mass?
Theoretically, of course.

maplebayou1
Ensign
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Joined: Tue Oct 05, 2010 9:45 pm

### Re: Negative Mass

If they exist, gravitons would have to have zero rest mass.

MrNelson
Asternaut
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Joined: Mon Nov 29, 2010 3:00 am

### Re: Negative Mass

I think that since gravitons need to be able to travel FTL to escape a black hole (or, more generally, an event horizon), they possess "imaginary mass" as mentioned briefly in the lecture.

yakovina_ivan
Asternaut
Posts: 4
Joined: Wed Nov 24, 2010 2:23 pm

### Re: Negative Mass

So, they should be some kind of tachyons, right?

maplebayou1
Ensign
Posts: 25
Joined: Tue Oct 05, 2010 9:45 pm

### Re: Negative Mass

A "real" graviton in general relativity cannot escape from a black hole. It travels at light speed and therefore has insufficient velocity. The problem is avoided by recourse to virtual gravitons. A virtual graviton can travel at any speed.

The same "loophole" applies to the interaction of a charged black hole with its surroundings. Virtual photons mediate the electromagnetic force and they can escape the black hole. Thus a charged black hole does "express" this charge in its environment.