I feel like I may have asked this before but search didn’t turn it up. Sorry if this is a repeat.
When you get enough mass together in a small enough space, it collapses into a black hole. (right?)
As an object’s speed increases in a frame of reference, its mass also increases in that frame of reference. (right?)
So you can create a black hole by accelerating any piece of matter sufficiently. (right?)
But the black hole will exist only in certain frames of reference, since its existence depended on its speed, which depends on frame of reference (right?).