The discussion centers around the concept of massless objects, particularly in relation to their ability to remain stationary while other massive bodies, like Earth, move. Participants explore the implications of mass on motion, specifically questioning whether an object with zero mass could exist at rest or would necessarily travel at the speed of light.
Participants generally agree that massless objects must travel at the speed of light, but there is disagreement regarding the implications of mass and the possibility of adjusting mass to achieve a stationary state.
The discussion includes unresolved questions about the definitions of mass and the conditions under which massless objects might behave differently. There is also ambiguity regarding the adjustment of mass and its implications for motion.
dulrich said:I am curious how you would "adjust" a body to change its mass at all. An object with zero mass must move at the speed of light or it wouldn't exist at all.
cubud said:I just wanted to know if objects without mass will always be traveling at the speed of light.
There is more than one sort of mass in relativity, e.g. "invariant mass" and "relativistic mass". Most physicists nowadays mean "invariant mass" when they say "mass". "Relativistic mass" is really just another name for "energy" (divided by c2) and the term is deprecated.FeDeX_LaTeX said:Why not faster? I was told that the photon traveled at the speed of light but it has a very, very small mass that is almost negligible (but still exists). So why wouldn't a smaller mass go faster?