It’s not really possible to ever know as you can’t reach the speed of light if you have mass. Only things like photon (tiny packets of light) can travel at the speed of light because they have no rest mass. In order to accelerate something with mass (even something that weighed very little) to the speed of light you would need an infinite amount of energy.
As per the einstein’s relativity theory
E=mc squared, now if u travel at a speed of light with your mass than it is equal to energy, but u can obtain energy when everything i.e mass here is destroyed. no other waY to get that energy!
Practicaly saying it is impossible to move a big mass at such a high speed. kinda impossible for now………………may b in future!!!
Well it is generally accepted that noting can travel at the speed of light (except light of course).
However, if you were travelling close to the speed of light you wouldn’t notice much yourself. However, the things around you that were not travelling at your speed would be terribly distorted from your point of view in terms of both their size and mass. Equally, a stationary observer looking at you would also see both your size and mass distorted massively (mass would increase and size would shrink). The key word here is that everything is relative, hence the general and special theories of relativity. The closer you get to the speed of light the worse this would get.
We actually know this happens from both theory and from real life. Satellites are travelling quite fast compare to us, fast enough in fact that small corrections need to made to their orbits because their masses appear to change to us and thus very small corrections are needed to calculate where they will be at a set time. So relativity has some relevance in real life!