Dear friends, There is something related to the history of theory relativity that has been bothering me this whole time. This is about the two postulates of special relativity. At the time of its invention, probably even up to now (I'm not sure since I'm not theoretical physicist), there had been no firm proof that lightspeed in vacuum is the same for all inertial reference frame. My question is why did it seem like there had been no notable objections from other scientists to this radically new assumption at the time? Or is there actually such heavy objection, only that I simply dont know it? I bring this up because I notice there are a couple of cases where a new idea in science was proposed followed by mocks by other scientists because it sounded stupid, too radical, or lacking evidence. Examples would be the first proposal that earth was round, which leads to the death sentence of the inventor if I remember it correctly and the proposal of the concept of quanta by Max Planck. I'm sure there are still more to those. But again why did Einstein seem to gain a smooth acceptance for his theory from physics community at the time?