I frequently read that accelerating a rest mass to c is impossible because it requires infinite energy. I just read another such post a moment ago. Surely, this must be a perception ONLY! That something's mass increases, I mean. It seems to me its mass does not actually increase, only appears to from the perspective a a relatively at rest observer. That in fact it is tied up with time dilation. To a photon, which is travelling at c, the universe must be perceived as having infinite mass. We would argue that any given object has some specific, measurable mass. So it is just perception, right? The mass is not actually increasing?