January 1, 1925: The Day We Discovered the Universe

What's in a date? Strictly speaking, New Year's Day is just an arbitrary flip of the calendar, but it can also be a cathartic time of reflection and renewal. So it is with one of the most extraordinary dates in the history of science, January 1, 1925. You could describe it as a day when nothing remarkable happened, just the routine reading of a paper at a scientific conference. Or you could recognize it as the birthday of modern cosmology--the moment when humankind discovered the universe as