When quizzed about the origins of modern scientific computing, many of us will think of the vast ENIAC installation completed at the University of Pennsylvania in 1946. It filled nearly 2,000 square feet of floor space, boasted 18,000 vacuum tubes, and weighed in at almost 50 tons. Today, several ENIACs would fit onto circuitry the size of an average human fingernail. Or we might think back over a hundred years earlier to Charles Babbage’s visionary Difference Engine, conceptualized in 1822 though not actually built as hardware until the 1990s. But when a Harvard Observatory astronomer in the 1870s requested computer access, it came to him on two brisk, sensibly shod feet, topped by a long skirt and prim shirtwaist blouse, pencil and paper in hand, and led by a brain with remarkable numerical and analytical skills.

THE GLASS UNIVERSE is renowned science writer Dava Sobel’s meticulous and engaging account of the pioneering work accomplished over nearly a century by a remarkable dynasty of creative and enduring women. Little known, and all but forgotten in our era of digital marvels, the collective vocation and personal passion of Harvard’s “lady computers” fully equaled that of their male colleagues in unraveling the mysteries of the stars.

The first telescopic photograph of a star was an image of Vega made at the Harvard Observatory in 1850 when the institution was barely a decade old and photography itself was still in its infancy. From then on, every night when the sky was clear, stellar images captured by astronomers were developed onto bulky and fragile glass plates, each about a foot square, and turned over to assistants to be examined, written on and documented in detail. From painstaking comparative analysis, measurable differences in the locations and behavior of celestial bodies could be tracked and later reveal unique patterns of spectral density, distance, rotational speed, magnitude, chemical composition and numerous other traits.

"THE GLASS UNIVERSE is one of those rare nonfiction books that held my heart and mind with equal intensity from start to finish, a must-read for anyone who has ever looked up at the night sky."

It soon became obvious that managing the observatory’s “glass universe” library of photographic plates --- which grew to more than 500,000 before film and digital photography took over --- was a demanding profession in itself, and one for which women showed a particular and patient aptitude. And this is where Sobel’s comprehensive research over more than two decades has borne such abundant fruit. THE GLASS UNIVERSE not only tracks a fascinating century of Harvard-led breakthroughs in international astronomy, but does so with a rich and vibrant personal focus that sets each woman’s life in its own distinct context.

The scores of young, middle-aged and even elderly women who contributed numerous discoveries, techniques and refinements to the advancement of astronomy and astrophysics came from a surprising diversity of backgrounds. While a number were recruited from the families of Harvard astronomers (like Anna Winlock, whose father was an early director), one of the most celebrated was Williamina Fleming (1857-1911). A Scottish immigrant and single mother who started life in North America as a maid, she went on to become the leading expert of her time in stellar spectral analysis and the first woman ever to hold an official position at Harvard. Other bright lights in this energetic female galaxy included Anne Jump Cannon (1863-1941), who classified hundreds of thousands of stars and whose spectral cataloguing system is still in use today, and Henrietta Swan Leavitt (1868-1921), who achieved major discoveries in the behavior of variable-intensity stars, which led to methods for accurately measuring vast distances across space.

As Sobel found, Fleming, Cannon and Leavitt were just three among this small army of persevering and motivated women who discovered that the “glass universe” was not limited by a glass ceiling. While usually paid less than their male counterparts for similar work (a situation that unfortunately still holds today), and not even able to vote until 1920, by and large the world of late 19th- and early 20th-century astronomy offered them challenges, camaraderie, respect, travel, recognition (published and financial), security, and even the occasional interstellar romance.

Much of Harvard Observatory’s success in the recruitment and development of its female army of computers lay in the foresight and enlightened leadership of male directors such as Edward Charles Pickering (1846-1919), who served from 1877 until his death --- an unprecedented four decades in which he managed to overturn numerous obstacles to the advancement of women in the sciences. After a short hiatus, he was followed in the post by Harlow Shapley (1885-1972), who continued advocating for women with the same zeal as his predecessor.

At the end of THE GLASS UNIVERSE, along with an astronomy timeline, glossary, chapter notes and index, Sobel thoughtfully includes alphabetical thumbnail biographies of all the principals in her book, male and female. It’s both interesting and gratifying to note that most of the “lady computers,” whether they became leading astronomers or not, lived long and full lives beyond the average for their time. Not only did they meet demands of unrelenting work in deciphering the glass plate signatures of stars, they were also extraordinary multi-taskers who ran households, cared for families and loved ones, volunteered their knowledge to the public, mentored other women, and took on numerous speaking engagements.

So what became of the original “glass universe”? Fortunately, most of the half-million imprinted and annotated photographic plates have physically survived the ravages of time, but the chemical coatings containing their precious images are threatened by deterioration. A vast project is now underway to scan them all (in order to preserve their millions of hand-printed annotations) and then clean and stabilize them. In a recent CBC Radio interview, Sobel noted the bittersweet irony of having to remove the womens’ imprint from the original glass plates in order to save them for the future, while at the same time releasing their digitally scanned images to the entire world. And so the legacy of Harvard Observatory’s “glass universe” lives on.

THE GLASS UNIVERSE is one of those rare nonfiction books that held my heart and mind with equal intensity from start to finish, a must-read for anyone who has ever looked up at the night sky.