Suppose we have a helium atom. The nucleus is composed of
four baryons, two dressed up as neutrons and two dressed up as protons. The
whole assembly is held together by the strong nuclear force, one of the four
fundamental forces of nature, the others being gravity, electrostatic and weak
nuclear. The baryons have existed since the Big Bang but their assembly into a
helium nucleus has been a relatively recent event. Prior to coming together in
the nucleus the baryons had different relativistic histories so it would be
very unlikely that they would all be the same age.
Since no particle can participate in an interaction at any
time other than its now, the ongoing participation of all four baryons
in the same interaction holding the nucleus together means that now for
all of them must have the same time coordinate, regardless of their different
ages. The same analysis applies to the electrons interacting with the
nucleus. Also the analysis applies to atoms interacting in an object so the
Earth and everything on it is constrained to have every particle’s now time
coordinate be identical.
Of course we have demonstrated that the now of a satellite in orbit
and of the Earth share the same time coordinate by the fact that the GPS does indeed
work. We can confirm that this extends to the Moon by noticing that the Moon’s
orbit about Earth is an ellipse. If now on the Moon was at a different
time than now on Earth, one of the bodies would be in the other’s future
and therefore unavailable for the gravitational interaction, as well as unable
to scatter light to its partner.
It is beginning to seem that all the particles in every
object that we can see or otherwise sense must share the same now time
coordinate. Perhaps we have come the long way around to Newton’s third law: “For
every action there is an equal and opposite reaction”. If objects are out of
phase in time, the action and reaction cannot be always equal and opposite.
How about galaxies far, far away beyond our
Since every observers observable universe must overlap with that of her
distant friend, there is no place for a transition to take place. Every
particle in the universe experiences now at the same time coordinate and
I am betting it is the age of the universe.
Even though all their nows are in phase there is not a single now
covering all the particles in the universe. Each particle’s now is a
point on its own world line. That may seem like an unnecessary complication but
the line of simultaneity paradox dictates that each particle have its