Recent content by DanielK

The reason for why people call the magnitude of a timelike spacetime displacement the proper time is that it has no spacelike component in the frame of the observer. In other words, the spacetime interval, which is invariant, is decomposed into a clear timelike and a clear spacelike interval...

OK, I just wanted to emphasize that the concept of mass is clear in relativity and there is nothing to worry about.

I don't see the point of this debate. According to relativity mass is invariant because it is the "length" of the energy-momentum four vector (mass-shell condition). That is rest mass is what relativity calls "mass". "Mass increasing", "longitudinal and transverse mass" are concepts that come...

I think that every relativist agree that your two-ship-paradox is essentially nothing more than a modern version of Einstein's classic thought experiment with the trains. It involves nothing more than the basic concepts of relativity with the usual LT equations. If it still looks paradoxical...

An answer to Yogi's argument on twin paradox: That is right. But the situation becomes more weird if we consider different spaceships traveling at the same uniform speed but different distances. Then the extent of the final time dilation in twin paradox depends entirely on the lengths of...

There is still nothing to be resolved. B* and E* are in sync in S*, but not in S, B and E are in sync in S, but not in S*. This is because events that happen simultaneously in their rest frame don't happen simultaneously in another frame which is moving relative to the previous one. Just...

Let's say I'm located at point B on the ship denoted by S. If the relative velocity of the two ships is high enough it is possible that my muon (M) will have just decayed when the end of the other ship (E*) passes me. This means that the Lorentz contracted length of S* equals the relative speed...

These are two distinct events in both frames. From frame S the other ship (S*) seems to be Lorentz contracted and - if their relative speed is almost c - it is possible that just after B and B* have coincided E* reaches B too, in less than 2 microseconds. The scenario is the same from S* where E...