So the other day I had a random thought that I think is has not been asked on this forum before.
so the faster you go the denser you get according to relativity.( you gain mass but your length shrinks) so if you are going fast enough shouldn't you collapse into a black hole? and since it is all relative isn't there a reference frame where we all collapse into a black hole? does anyone know how relativity deals with this? I am probably missing something obvious...
It would depend on what you are trying to move so quickly. The only known objects dense enough to collapse into singularities are stars. There is no reference frame where we all collapse into singularities, I think you are defining reference frame incorrectly.
The only time relativistic mass truly becomes a problem is when the object you are moving approaches the speed of light (rather than reach the speed of light, all energy it receives will simply make it more massive, rather than increase its velocity.). This means something would have to be giving you an infinite amount of energy that exponentially increases as it gives it to you. Therefore, say we are actually moving momentously fast, but we don't know it since we have no "slow object" to reference ourselves to, we would never have to worry about becoming too massive. If we were receiving infinite amounts of energy at an exponential rate, the universe would have collapsed itself billions of years ago.