On May 8, 12:52 pm, wrote:

Everything is not relative but the speed of light in vacuo is the one
constant in the universe.

Mitch Raemsch

everything is not relative? is that right -- is that what relativity
is really is? I thought even in Newton's physics, speed is relative,
so maybe Einstein's theory is different in this regard? When we say
"something approaches the speed of light", is that absolute speed or
relative to the observer?