patcl@tekecs.UUCP (Pat Clancy) (06/21/85)
This is prompted by a description of the inflationary
universe model which I came across in a book by H. Pagels
called Perfect Symmetry (a recent addition to the
new-physics-for-non-physicists genre). Anyway, this has
bothered me before. Why is it that the radius of the
universe can expand at faster than c, and yet galaxies do
not (of course) move apart this fast? The analogy given in
the book is to a one-dimensional universe represented by
a circle (ie., line), expanding in two dimensions. We are told that
"the radius of the circle can expand as fast as it wants;
it is not limited by the speed of light because no energy
is being transported by such an expansion". As I recall,
the circumference grows as a product of the radius, so wouldn't
things on the circumference have to move away from each other at some
multiple of c? The inflationary universe model calls for an
expansion equivalent to the growth of a circle starting out
as big as your finger, and ending up many orders of magnitude
(possibly 20) larger than the current observable universe,
taking place in the period between 10**-35 and 10**-33 seconds
after time 0. How is it that the c limit is maintained?
I'm obviously missing some essential concept, and I hope
someone who really understands this stuff can supply it.
By the way, there's also a fairly recent (within the last year)
Scientific American article on the inflationary universe
model, which was even less clear (at least to me) on this point.
Pat Clancy, Tektronix
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