We know that at
0 K, particles of matter almost stop vibrating/moving completely. Also, as we increase temperature of the system, the particles gain energy (in the form of the heat supplied) which gets converted to kinetic energy, and the motion of the particles become faster.
Since it is practically impossible for an object to get to the speed of light, it is just possible for it to have a speed near the speed of light.
My question is,
What is the temperature, at which, particles of matter gain so much energy that they start vibrating/moving with a speed near the speed of light?
Also, what would our observation be, on looking at such a piece of matter? What would it look like?