Henrietta Leavitt Finds a Way to Measure the Universe

In the opening years of the twentieth century, measuring the vastness of the heavens remained one of the central dilemmas in astronomy. Scientists relied principally on stellar parallax, a geometric technique that calculated distances by observing how a star appeared to shift position against more distant objects as the Earth orbited the Sun. While reliable for nearby celestial bodies, parallax became ineffective for all but relatively nearby stars, leaving the scale of the broader cosmos fundamentally uncertain.

Henrietta Swan Leavitt addressed this limit from her desk at the Harvard College Observatory. After studying at Oberlin College and earning a bachelor's degree in 1892 from Radcliffe College, she had joined the observatory staff as a human computer under director Edward Charles Pickering. Women at the institution were barred from operating the telescopes, working instead to analyze photographic glass plates captured by instruments such as the Bruce Astrograph at the observatory station in Arequipa, Peru.