Natural Science Forum / Physics / General Physics / July 2008

Though one observer might calculate that
two events separated in space are simultaneous,
there exist some positions and velocities that
another observer could have, to calculate correctly
that one of the events happened first; and there
exist other positions and velocities than an obverver
could have, to correctly calculate that the other of
the two events happened first.

The maximum that this disparity between correct
calculations of the time of two events is the time
it takes light to travel between the two positions in
space.

Thus, since it takes light about a second and a half
to travel between the earth and the moon, the
minimum uncertainty between the time of two events,
on the earth and the moon, is a second and a half.

This uncertainty is not because an observer on one
of the bodies can't see an event on the other body
when it happens.  The observer can correct for the
time it takes, say, a light flash to get to him.  And
the observer with one of those different positions and
velocities also can make similar corrections.  But
after the corrections, the two observers each have
correctly calculated different times for the same
two events.

This is the 'simultaneity' issue.

Now, does the action at a distance that we hear
about, associated with quantum theory, take into
account the 'simultaneity' issue?  There is no
'now' for two positions at a distance from each
other in space.  What does quantum theory say
about that when making its statements concerning
'action at a distance'.