Becoming a black hole at high velocities?

Question

Imagine an object approaching the speed of light relative to a certain observer. As the mass tends towards infinity and the length(and thus the volume, ) drops to zero, won't the object reach a point where it can collapse to form a black hole?

And yet, from a third inertial frame of reference where the object is moving at a smaller relative velocity, won't the object be still unable to collapse?

Answer 1

This question gets asked from time to time, and the answer is, "No, things do not become a black hole because they're going so close to the speed of light". As an analogy, let's say that I have a teapot in a spaceship, and the spaceship is going really fast. The teapot to me isn't even hot enough to boil, but are you saying that it could be boiling relative to YOU? No, neither one of us is going to see it boiling if it isn't hot enough, regardless of how fast I'm going relative to you. NOR it is going to freeze, "because, golly, my clock is going so slow now!"

FYI, in general relativity, it's the REST mass of the object, relative to its own size, that determines if it'll form a black hole.

Answer 2

Yes.

I think the new atom smasher they're building at CERN is going to be able to accelerate protons fast enough that they'll become black holes.

However such tiny blackholes 'evaporate' almost instantly. There's no danger of one growing bigger and bigger and devouring the planet.