Reading this comment makes me ask what does that actually mean that
In fact, if you are close enough to $c$, the mass-equivalent of your kinetic energy may be enough to make you appear as a black hole to an external observer
? Does it mean that any object travelling at a near the speed of light will act as a black hole even if its mass isn't contained within the necessary Schwartzschild Radius? If yes, then what would cause the regular properties of the black hole (such as event horizon as point of no return etc) to appear just because the object is moving fast?
Or what does "appear as a black hole" mean in this case?
