There does arise, however, a strange difficulty. The interpretation of
the galactic line-shift discovered by Hubble as an expansion (which can
hardly be doubted from a theoretical point of view), leads to an origin
of this expansion which lies only about 109 years ago, while physical
astronomy makes it appear likely that the development of individual
stars and systems of stars takes considerably longer. It is in no way
known how this incongruity is to be overcome.
I further want to remark that the theory of expanding space, together
with the empirical data of astronomy, permit no decision to be reached
about the finite or infinite character of (three-dimensional) space,
while the original static hypothesis of space yielded the closure
(finiteness) of space.
_K_ = co-ordinate system
_x, y_ = two-dimensional co-ordinates
_x, y, z_ = three-dimensional co-ordinates
_x, y, z, t_ = four-dimensional co-ordinates
_t_ = time
_I_ = distance
_v_ = velocity
_F_ = force
_G_ = gravitational field
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