Dear Brian,

In The Elegant Universe, you write, "Einstein found that precisely
this idea--the sharing of motion between different dimensions--
underlies all of the remarkable physics of special relativity, so long
as we realize that not only can spatial dimensions share an object's
motion, but the time dimension can share this motion as well. In
fact, in the majority of circumstances, most of an object's motion is
through time, not space. Let's see what this means."

The sharing of motion between different dimensions occurs because the
fourth dimension is expanding relative to the three spatial
dimensions.

The simple proof is as follows:

The only way to stay stationary in the fourth dimenion is to translate
with a velocity c through the three spatial dimensions.

The only way to stay staionary in the three spatial dimensions is to
translate with a velocity c through the fourth dimensions.

Ergo, the fourth dimension is translating relative to the three
spatial dimensions.

A THEORY OF MOVING DIMENSIONS

even academics make silly errors;
this does not a theory make!

to quoth Bucky,
"Time is the only dimension," but
it's really just phase-space, if
you're going to get on your knees to make dieagrams
on the Big Dymaxion (tm) Map.