The Universe Within Read Online Free

Computers at the turn of the twentieth century.Edward Charles Pickering, then director of theHarvard College Observatory, had a problem that required serious computation and analysis. The observatory was collecting reams of pictures ofconstellations, stars, andnebulae—so many that just managing and plotting the images was a daunting task. Of course, digital computers as we know them didn’t exist at this time and the calculations had to be done by hand. Pickering was famously cheap and once declared in a fit of exasperation with his existing staff that he could hire his maid to do this work at half the cost. He fell in love with his new idea and ended up pressing his real maid,Williamina Fleming, into service at the observatory.
    At age twenty-one and with a young son, Williamina Fleming was abandoned by her husband, leaving her penniless and without a trade. Pickering first hired her to clean house. Then, after his boast, he brought her to the observatory to manage his celestial images. Upon receipt of a large donation, Pickering was able to add a number of other women to the group. What Pickering could never have planned was that from this team grew some of the greatest astronomers of the time, or any time for that matter. These women collectively became known as the Harvard Computers: they sat with the raw data of astronomy, pictures of the heavens, and made sense of them.
    Henrietta Leavitt, the daughter of a Congregational minister, came to the observatory in 1895, first volunteering and later earning a salary of thirty cents an hour. She developed a love for astronomy in school, a passion that served her well during the long years she had the mind-numbing task of cataloging photographic plate after plateof stars and nebulae.
    As Leavitt knew, the different stars in the sky vary incolor and magnitude of their light. Some stars are dim or small, others bright and big. Of course, there was no real way of knowingwhat magnitude meant for the real brilliance of a star, because an apparently dim star could be a big and bright one far away or a faint one relatively close.
    Edward Charles Pickering (upper row) and the “Harvard Computers.”Williamina Fleming is in the front row, third from left;Henrietta Leavitt is just to the right of Pickering. (Illustration Credit 2.1)
    Leavitt became fascinated by one type of star that changed regularly from bright to dim over the course of days or months. Mapping seventeen hundred stars, she charted every property she could measure: how bright they were, where they sat in the sky, and how rapidly thesevariable stars went from bright to dim. With all of these data, Leavitt uncovered an important regularity: there is a constant relationship between how fast some stars cycle from bright to dim and their
real
brightness
.
    Leavitt’s idea seems awfully esoteric, but it is profound. Starting with the principle that light travels at a constantspeed, and knowing how bright the star actually was and how bright it appeared, meant that thedistance of the star from Earth couldbe estimated. With this insight, Henrietta Leavitt gave us a ruler with which to measure distances in deep space.
    We have to imagine astronomy in that era to appreciate the transformative power of Leavitt’s discovery. From the time of Galileo to Pickering, people observed the sky and saw theplanets,nebulae, and fuzzy patches of light with ever-increasing clarity. But the central questions remained. How big is the universe? Is our own galaxy, theMilky Way, all there is?
    No sooner had Leavitt proposed her idea in 1912 than other astronomers began to calibrate and apply it to the heavens. One Dutch scientist used Leavitt’s ruler to measure the distances between individual stars. It gave him a big number. The galaxy is vast almost beyond imagination. ThenEdwin Hubble, armed with Leavitt’s idea, used the biggesttelescope of the time to change our view of the universe almost overnight.
    In 1918, Hubble, a Rhodes scholar