THE OBSERVATIONAL APPROACH TO COSMOLOGY

THE OBSERVATIONAL APPROACH TO

COSMOLOGY



Most of the theoretical investigators adopt this point of view, and accept without question the

interpretation of red-shifts as velocity-shifts. They are fully justified in their position until evidence to

the contrary is forthcoming. But these lectures will present a remarkable situation. The familiar

interpretation of red-shifts seems to imply a strange and dubious universe, very young and very small.

On the other hand, the plausible and, in a sense, familiar conception of a universe extending indefinitely

in space and time, a universe vastly greater than the observable region, seems to imply that red-shifts are

not primarily velocity-shifts.

In view of this possible conflict, whether of facts or theories or speculations, the observer is inclined to

keep an open mind and to adopt parallel working hypotheses for the interpretation of his explorations.

He may assume, first, that red-shifts are velocity-shifts, or, secondly, that red-shifts result from some

unknown principle that does not involve actual motion, and always, of course, he will search for some

empirical, critical test for distinguishing between the two assumptions, between motion and no motion.



https://ned.ipac.caltech.edu/level5/Sept04/Hubble/paper.pdf