Negative Mass (Part 2)

I’m trying to lose weight. I was so happy when I saw my local pastry shop sold negative-mass doughnuts! But what happened next really freaked me out. Hear the tale here:

This is the second of my Edinburgh Explorations videos. See if you can spot the dumb mistake at 14:25.

In this video, I examine the strange concept of negative mass in Newtonian mechanics, special relativity and relativistic quantum mechanics. I emphasize that to fool around with strange ideas like negative mass, it helps to work within in some specific theory, and the answers you get will depend on the theory you use. For example Newtonian mechanics allows for negative mass, but special relativity seems to make the concept more or less meaningless, because mostly what shows up is the mass squared.

I still have some questions about that, though… like what happens if you make the mass negative in the usual Lagrangian for a relativistic point particle. For a single particle, I think switching the sign of the Lagrangian doesn’t change the solutions, either classically or quantum-mechanically. But for an interacting two-particle system, the relative signs can matter.

For more on all this, see:

• Negative mass (part 1).