Physics can be pretty complicated, but what makes physics different from lesser sciences, like Calvinball, is that physics has rules that are absolute. In the case of relativity there are two big starting rules:#1) All of physics works exactly the same whether you’re moving or sitting still. No matter how fast or slow something is moving, it will always behave exactly the same way it would if it were sitting still. So, if you accelerate a rock to 99.99999999% of light speed (or thereabouts), then it will do exactly what a rock at 0% of light speed does: be a rock. So if a thing isn’t a black hole when it’s sitting still, then it isn’t a black hole when it’s moving.