3 ms·

In a reply I also just made alongside yours, I mention that we're actually measuring the speed of causality - so you could think of "the speed of a massless ob

• petewailes 10y ago
  To be pernickety (because we like that around here), what I think you're referring to is the transmission of information, which is still down to the maximum velocity at which something of no mass can propagate through spacetime to interact with something else within its light cone[0][1]. The important thing in causality is the concept of the light cone. For things that happen far apart enough that the light cones don't interfere with each other, causality doesn't matter. One could happen first, or the other. It's only when you consider two things where the interaction occurs that the propagation matters. Clearing this up a little further, having just read your other comment, the causal link between events and the speed by which information propagates is as a result of c, not the cause of it. 0: https://www.wikiwand.com/en/Light_cone https://www.wikiwand.com/en/Light_cone 1: http://www.pitt.edu/~jdnorton/teaching/HPS_0410/chapters/spacetime/ http://www.pitt.edu/~jdnorton/teaching/HPS_0410/chapters/spa...