Not until the empirical resources are exhausted, need we pass on to the dreamy realms of speculation.

The great spirals, with their enormous radial velocities and insensible proper motions, apparently lie outside our Solar system.

Past time is finite, future time is infinite.

The outstanding feature, however, is the possibility that the velocity-distance relation may represent the de Sitter effect, and hence that numerical data may be introduced into discussions of the general curvature of space.

The great spirals... apparently lie outside our stellar system.

Astronomy is something like the ministry. No one should go into it without a call. I got that unmistakable call, and I know that even if I were second-rate or third-rate, it was astronomy that mattered.

Observation always involves theory.