My understanding is that mass is a property of energy. The faster an object goes, the more energy it has which corresponds to a loss of mass.
You don't mean loss, do you?
So massless particles such as photons travel at the speed of light. Anything traveling faster than the speed of light has a negative mass, which is, for me, a bit hard to grasp.
Actually, the facts are harder to grasp then that.
A particle travelling faster than light needs to have the
square of its mass negative. This means that its
mass is ...
imaginary. (The imaginary numbers are the square roots of negative real numbers. If you've not come across them, you might want to look them up.)
Now, the way to cope with this is to adopt a positivist attitude. What does it
mean, you ask, to have an imaginary mass? Well, it means that if you plug an imaginary number into the equations of physics where it says
m, then they will describe how a faster-than-light particle behaves and what we'd observe if we looked at one. Hence, it is a perfectly meaningful concept: "What does it mean for a particle to have imaginary mass?" --- "It means that it'll behave like
this, unlike particles with real mass, which behave like
that."
After all, how do we ascertain that a particle has real non-zero mass? Because it behaves like the laws of physics predict that it would if it did. It's easier to turn the predictions back into your everyday experience only because you hang out with stuff with real mass.
Edited by Dr Adequate, : No reason given.
™ Version 4.2