I suppose that we need more identical twins in the astronaut program.
What about GPS satellites? I think they are bit bit "larger than an entire
molecule".
I guess I have to explain in a little more detail. I'm keeping in mind a
misinterpretation of special relativity that I've run into several
times, in various forms. It does not deny that clocks run at different
rates in frames of reference that are accelerated relative to each
other, but claims that this is somehow distinct from the actual passage
of time, which continues at the same rate regardless of how fast the
clocks tick. This implies, in particular, that people will actually be
able to perceive that they are in an rapidly moving frame of reference,
by observing physical processes (other than their own aging, which is
"somehow" not a physical process). Implicit in this concept is the
existence of a preferred frame of reference in which the clocks click at
the fastest possible rate - the "rest frame" of the entire universe, so
to speak.
The net result is that, according to this interpretation, the twin who
was accelerated to high velocity relative to Earth, accelerated again to
reverse his velocity relative to Earth, and accelerated again to match
his velocity with Earth's at the same time that he returns to Earth,
will indeed see his clocks measuring out a smaller amount of time than
the twin who stayed on Earth. However, both twins will have aged by
precisely the same amount.
Feel free to point out the logical inconsistencies of this point of
view; there are too many to easily count. It is, however, the point of
view that I tend to think of as the opposition who needs to be convinced
in any twin-paradox discussion.
No matter how many successful measurements you make of time-dilation
using high precision clocks, they won't refute this interpretation. It's
"just" a change in the clock speed, not an actual change in the rate of
passage of time. What's needed is a biological system actually aging at
a noticeably slower rate, and systems that are actually subject to aging
tend to be vary large - there's no such thing as "old age" for a
bacterium. It would be very difficult to accelerate such organisms up to
velocities high enough to show significant differences in the actual
rate of aging.
However, I feel that there's a certain symbolic similarity between the
spontaneous decay of unstable particles (such as neutrons), and the
death of a human being. That this decay occurs less rapidly for rapidly
moving particles that for slower moving ones seems, to me, to more
directly attack the misinterpretation that I've described, than the fact
that rapidly moving clocks tick more slowly. I suppose that I'm probably
being optimistic about the openness of those people to accepting
relevant evidence.
