The Astronomer Who Brought Us the Universe

StartsWithABang writes If all we were able to do was look up at the sky and see what we can see, no matter how powerful our instruments became, we would be extraordinarily limited in what we could learn about the Universe. But if we could know some intrinsic properties about what we were looking at, then simply by measuring things like how bright these objects appear, we could figure out the cosmic distance scale; all it would require is knowledge of a "distance indicator" or "standard candle." The very first one ever discovered — by Henrietta Leavitt — is not only still in use today, but taught us the galactic nature of the spiral nebulae and gave us the expanding Universe.