One of the biggest questions about our universe had long been just how big it is. Of course the stars we see are far away, but just how far was unknown for most of human history. Figuring out the answer to this question was an enormous challenge: it isn’t the case that the brightest stars are the closest, and what does “close” mean to our brains, when we are dealing with light years?.
Henrietta Swan Leavitt was the person who figured out how to solve this problem. Before Leavitt, astronomers were using methods that could measure hundreds of light years away (namely, trigonometry/triangulation and seeing which stars in the celestial spheres moved in front of each other/star parallax).
Leavitt was scientifically minded and independently wealthy, and she ended up working at Harvard for Edward Charles Pickering as one of the computers cataloguing the brightness of stars in the sky (she earned $0.30 cents an hour, about half the American minimum wage today). Her biggest breakthrough came from noticing a type of star that pulsated in brightness regularly — this was the “Cepheid variable” that led to the measurement of distant space.
Using the knowledge of the stars with Cepheid variables, Leavitt could start to figure out how much space was between star clusters in a given area of the sky. And then this knowledge could be expanded, like pieces of a table puzzle across the celestial sphere, thus creating the first “standard candle” which could measure distances up to 20 million light years away.
Leavitt died in 1921 from stomach cancer, but her technique was used later that decade by Edwin Powell Hubble to show conclusively that there were galaxies beyond our own with the Andromeda Galaxy. The universe was far vaster for humans after that.
Source(s): Wikipedia, _Wired_ Randy Alfred “Dec 30, 1924: Hubble reveals we are not alone,” Dec 30, 2009.
