4 ms·
Reference frames are local constructs, they cannot be used to (uniquely) define simultaneity over large distances. The time of any single event is just a "tag"
by dsqrt 10y ago
Reference frames are local constructs, they cannot be used to (uniquely) define simultaneity over large distances. The time of any single event is just a "tag" in relativity. In fact there are infinitely many surfaces of simultaneity that contain the merger of those two stars and meet the Earth at a particular time "t" in the range ~[-2000, +5] from now, so that it is equally valid to state that the merger happened ~2000 years ago or ~20 years ago, or that it has not happened yet.
For this reason, to avoid confusion, it is much better and customary to "tag" astronomical events by the time we observe them. That is to say that they happen when we observe them.
- pif 10y ago> Reference frames are local constructs, they cannot be used to (uniquely) define simultaneity over large distances. Large distances? Please, we are talking about a couple thousand years: what's that compared to the age of the universe?
- dsqrt 10y agoLarge and close is respect to the light-crossing time and the accuracy with which you want to timestamp an event. If you care about years, 1 light year is already a large distance.