Myths
Absolute Space
Points of View
Twin Paradox
Einstein's Train
Andromeda Paradox
Time in Spacetime
Clocks & Time
Velocity of Light
The Andromeda Paradox
The Andromeda Paradox is similar to the Einstein's Train example but extends the concept of differences in simultaneity into planes of simultaneity which extend throughout spacetime. These are thought to be affected by the velocity and direction of motion of the observer, and the distance between the observer and an object.
All these factors combine, so if the observer A has a small velocity towards a very distant object (such as Andromeda), this can move the plane of simultaneity such that events in the future of Andromeda (e.g. the launch of an invasion fleet of spaceships towards Earth) become simultaneous with events in the present local to the observer.
Similarly, if observer B has a small velocity away from the object (Andromeda), this moves the plane of simultaneity into the past (e.g. before the decision to send the fleet was made). Thus in B's present, the spaceships have not been launched. A fuller explanation of the paradox is given here.
This idea may arise from a fundamental misunderstanding of the nature of spacetime. We deal with that later when we look at Zero Spacetime Intervals, but here it is sufficient to note that, if, as I suggest, the diferences in simultaneity are not a real phenomenon, then the concept of planes of simultaneity collapses.
