The discussion revolves around the implications of simultaneity as perceived by two observers, A and B, who are at rest relative to each other. The focus is on whether observer B would measure different times for two objects falling from a height, considering the effects of light travel time and the principles of relativity.
Participants generally agree that simultaneity is preserved for observers at rest relative to each other, but there is a recognition of the complexities introduced by light travel time and the implications for absolute time, indicating a nuanced discussion without full consensus.
The discussion touches on the limitations of classical notions of time in light of relativity, and the need for experimental validation of theoretical concepts, but does not resolve the broader implications of these ideas.
I think i get it. The difference come when they move relative to each other. This is why we can't have an absolute time ? Thanks for the response.Ibix said:You mean that A and B are at rest with respect to one another? In that case no, if the impacts are simultaneous for one then they are simultaneous for both (although strictly the presence of gravity makes this more complicated, we can easily arrange things so we can neglect that). B will certainly receive light from the impacts at different times, but relativity is about what happens after you correct for the travel time of light. Observers in relative motion turn out to get different results if they use the same procedure to correct for the travel time, but observers at relative rest (like your A and B) get the same result.
I assume you've heard of Einstein's train thought experiment? The point is not that the observers receive the light at different times, but that they put different interpretations on what they see.
Strictly, it's one way to show that a global notion of time is inconsistent with an invariant speed of light and the principle of relativity. You then need to go out and do an actual experiment to see if it's consistent with reality. Which we've done, and so far it is consistent.adosar said:This is why we can't have an absolute time ?