Bug riding on a ball moving at almost the speed of light A ball with a bug on it is thrown at almost the speed of light. The bug looks back and observes the thrower throwing the ball. 
In the context of special relativity, what is the weight and the height of the thrower that is observed by the bug?
Edit: In the reference frame of the bug.
 A: The thrower's height doesn't change i.e. it is the same in both the reference frames of the thrower and the bug. That's because distances normal to the direction of motion are not changed by Lorentz transformations. In the bug's frame the thickness of the thrower decreases, so the thrower is flattened in the direction of motion, but the height is unchanged.

Re the weight of the thrower, this is an issue that keeps coming up in questions about special relativity. The convention these days is that the word mass means rest mass, and the rest mass is an invariant. Therefore by definition the mass of the thrower is the same in all reference frames. In the bug's frame the energy of the thrower is given by:
$$ E^2 = p^2c^2 + M_t^2 c^4 $$
where $M_t$ is the (invariant) rest mass of the thrower and $p$ is their momentum (measured in the bug's frame). You can, if you wish, divide the energy by $c^2$ to get a relativistic mass that will be greater than the rest mass. However this is not generally a useful thing to do.
