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The Glass Universe: How the Ladies of the Harvard Observatory Took the Measure of the Stars by Dava Sobel
Albert Einstein, card file, Cepheid variable, crowdsourcing, dark matter, Dava Sobel, Edmond Halley, Edward Charles Pickering, Ernest Rutherford, Harlow Shapley and Heber Curtis, Harvard Computers: women astronomers, index card, invention of the telescope, Isaac Newton, Johannes Kepler, John Harrison: Longitude, luminiferous ether, Magellanic Cloud, pattern recognition, QWERTY keyboard, Ralph Waldo Emerson, Solar eclipse in 1919
The large female staff, sometimes derisively referred to as a harem, consisted of women young and old. They were good at math, or devoted stargazers, or both. Some were alumnae of the newly founded women’s colleges, though others brought only a high school education and their own native ability. Even before they won the right to vote, several of them made contributions of such significance that their names gained honored places in the history of astronomy: Williamina Fleming, Antonia Maury, Henrietta Swan Leavitt, Annie Jump Cannon, and Cecilia Payne. This book is their story. PART ONE The Colors of Starlight I swept around for comets about an hour, and then I amused myself with noticing the varieties of color. I wonder that I have so long been insensible to this charm in the skies, the tints of the different stars are so delicate in their variety. . . . What a pity that some of our manufacturers shouldn’t be able to steal the secret of dyestuffs from the stars.
Glass plates are moved to new fireproof Brick Building Williamina Fleming prepares “A Field for Woman’s Work in Astronomy” for presentation at the Columbian Exposition in Chicago; discovers her first nova on plates from Arequipa Bruce telescope sees first light at Cambridge. 1895 Edward Pickering institutes the Harvard College Observatory Circular to describe news of the observatory, beginning with Williamina Fleming’s discovery of Nova Carinae (her second nova) from photographs taken at Arequipa; her third such discovery, Nova Centaurus, follows a few months later. Henrietta Swan Leavitt volunteers at the observatory Solon Bailey discovers many variables within certain star clusters of the Southern Hemisphere. 1896 Annie Jump Cannon joins the observatory as a research assistant, commences her study of the spectra of bright southern stars. Bruce telescope arrives at Arequipa. 1897 Antonia Maury publishes “The Spectra of Bright Stars” in the Annals, vol. 28, and is acknowledged as the author on the title page. 1898 National professional organization of astronomers, later named the Astronomical and Astrophysical Society of America, established at a meeting held at Harvard.
Solon Bailey completes a provisional catalogue of 76 globular clusters in the Annals, vol. 76. 1918 First of nine volumes of the greatly expanded Henry Draper Catalogue is published in the Annals, beginning with vol. 91. 1919 Edward Pickering dies. Solon Bailey serves as interim director. 1920 Harlow Shapley and Heber Curtis debate the scale of the universe. 1921 Harlow Shapley is named fifth director. Henrietta Leavitt dies Harlow Shapley and Annie Cannon explore the relation between spectral type and magnitude. 1922 International Astronomical Union adopts Harvard’s Draper stellar classification, representing the work of Williamina Fleming, Antonia Maury, and especially Annie Jump Cannon. 1923 Adelaide Ames enrolls as Harvard’s first graduate student in astronomy. Cecilia Payne arrives from England as Harvard’s second graduate student in astronomy Harvard Reprints series initiated to disseminate staff members’ published articles in professional journals. 1924 Harlow Shapley issues the first in a series of papers detailing the distance, size, and structure of the Magellanic Clouds.
Day We Found the Universe by Marcia Bartusiak
Albert Einstein, Albert Michelson, Arthur Eddington, California gold rush, Cepheid variable, Copley Medal, cosmic microwave background, cosmological constant, Edmond Halley, Edward Charles Pickering, Fellow of the Royal Society, fudge factor, Harlow Shapley and Heber Curtis, Harvard Computers: women astronomers, horn antenna, invention of the telescope, Isaac Newton, Louis Pasteur, Magellanic Cloud, Occam's razor, orbital mechanics / astrodynamics, Pluto: dwarf planet, Solar eclipse in 1919, William of Occam
Resembling assembly-line workers in a factory, with their plain, unadorned dresses, these dedicated women—swiftly, accurately, and cheaply—numbered each star on a given plate, determined the star's exact position, and assigned it either a spectral class or photographic magnitude. Annie Jump Cannon, who established the stellar classification system adopted internationally in the course of this work, praised Pickering's modern outlook. “He treated [the computers] as equals in the astronomical world,” she claimed (somewhat Pollyannishly), “and his attitude toward them was as full of courtesy as if he were meeting them at a social gathering.” He was their gallant Victorian gentleman. Pickering's first hire was his housekeeper, Williamina Fleming, who had displayed a keen intelligence in carrying out her duties. Frustrated one day by a male assistant's ineptitude, Pickering had declared that his maid could do a better job, and he found out she could.
Cambridge, Mass.: Harvard University Press. Babcock, A. H. 1896. “Completion of the Big Crossley Reflector Dome for the Lick Observatory.” San Francisco Chronicle, September 27. Baida, P. 1986. “Dreiser's Fabulous Tycoon.” Forbes 400 (October 27): 97-102. Bailey, S. I. 1919. “Variable Stars in the Cluster Messier 15.” Annals of the Astronomical Observatory of Harvard College 78: 248-50. ——. 1922. “Henrietta Swan Leavitt.” Popular Astronomy 30 (April): 197-99. Ball, R. S. 1895. The Great Astronomers. London: Isbister. Barnard, E. E. 1891. “Observations of the Planet Jupiter and His Satellites During 1890 with the 12-inch Equatorial of the Lick Observatory.” Monthly Notices of the Royal Astronomical Society 51: 543-56. Belkora, L. 2003. Minding the Heavens. Bristol: Institute of Physics Publishing. Bennett, J.
(Roger Smith/NOAO/AURA/NSF/WIYN) With the huge number of photographic plates of the northern and southern skies stacking up at the observatory on Garden Street in Cambridge, Massachusetts, Pickering shrewdly recognized the value of smart young women yearning to make contributions in an era that generally denied them full access to scientific institutions. Here was a ready workforce, he noted in one annual observatory report, entirely “capable of doing as much and as good routine work as astronomers who would receive much larger salaries. Three or four times as many assistants can thus be employed, and the work done correspondingly increased for a given expenditure.” Williamina Fleming (standing) directs her “computers” while Harvard Observatory director Edward Pickering looks on (Harvard College Observatory) These women “computers,” as they were called, many with college degrees in science, were situated in two cozy workrooms, pleasantly decorated with flowered wallpaper and star charts. Working at ma hogany writing tables, crammed together, each woman through the day might peer through a magnifying glass at her selected plate or industriously record her findings in a notebook.
Coming of Age in the Milky Way by Timothy Ferris
Albert Einstein, Albert Michelson, Alfred Russel Wallace, anthropic principle, Arthur Eddington, Atahualpa, Cepheid variable, Commentariolus, cosmic abundance, cosmic microwave background, cosmological constant, cosmological principle, dark matter, delayed gratification, Edmond Halley, Eratosthenes, Ernest Rutherford, Gary Taubes, Harlow Shapley and Heber Curtis, Harvard Computers: women astronomers, Henri Poincaré, invention of writing, Isaac Newton, Johannes Kepler, John Harrison: Longitude, Karl Jansky, Lao Tzu, Louis Pasteur, Magellanic Cloud, mandelbrot fractal, Menlo Park, Murray Gell-Mann, music of the spheres, planetary scale, retrograde motion, Richard Feynman, Search for Extraterrestrial Intelligence, Searching for Interstellar Communications, Solar eclipse in 1919, source of truth, Stephen Hawking, Thales of Miletus, Thomas Kuhn: the structure of scientific revolutions, Thomas Malthus, Wilhelm Olbers
At Harvard College Observatory, a leader in the dull but promising business of stellar taxonomy, photographic plates that revealed the color and spectra of tens of thousands of stars were stacked in front of “computers”—spinsters, most of them, employed as staff members at a university where their sex barred them from attending classes or earning a degree. (Henrietta Leavitt, the pioneer researcher of the Cepheid variable stars that were to prove so useful to Shapley and Hubble, was a Harvard computer.) The computers were charged with examining the plates and entering the data in neat, Victorian script for compilation in tomes like the Henry Draper Catalog, named in honor of the astrophotographer and physician who had made the first photograph of the spectrum of a star. Like prisoners marking off the days on their cell walls, they tallied their progress in totals of stars cataloged; Antonia Maury, Draper’s niece, reckoned that she had indexed the spectra of over five hundred thousand stars. Theirs was authentically Baconian work, of the sort Newton and Darwin claimed to practice but seldom did, and the ladies took pride in it; as the Harvard computer Annie Jump Cannon affirmed, “Every fact is a valuable factor in the mighty whole.”3 It was Cannon who, in 1915, first began to discern the shape of that whole, when she found that most stars belonged to one of about a half-dozen distinct spectral classes.
If, for instance, we have two Cepheid variables with the same period, we may assume that they have about the same absolute magnitude. If the apparent magnitude of one is four times that of the other, we conclude (barring complications such as the interference of an intervening interstellar cloud) that the dimmer star is twice as far away. The relationship between the periodicity and the absolute magnitude of Cepheid variable stars was discovered in 1912 by Henrietta Swan Leavitt, one of a number of women hired at meager wages to work as “computers” in the Harvard College Observatory office in Cambridge, Massachusetts. Leavitt spent her days examining photographic plates taken through the twenty-four-inch refracting telescope at the Harvard station in Arequipa, Peru. One of her tasks was to identify variable stars. This involved comparing thousands of pinpoint star images on plates taken on different dates, looking for changes in brightness.
Noteworthy Events: Jacobus Kapteyn, studying the proper motions of twenty-four hundred stars, finds evidence of what he calls “star streaming”—that stars in our neighborhood move in a preferred direction—an early clue to the rotation of our galaxy. Time: 1911 Noteworthy Events: Ernest Rutherford determines that most of the mass of atoms is contained in their tiny nuclei. Time: 1912 Noteworthy Events: Henrietta Swan Leavitt discovers a correlation between the absolute magnitude and the period of variability of Cepheid variable stars, opening the door to their use as intergalactic distance indicators. Time: 1913 Noteworthy Events: Niels Bohr develops theory of atomic structure, in which electrons are said to orbit the nucleus in a manner somewhat akin to that of planets orbiting the sun. Noteworthy Events: Henry Norris Russell presents a plot of the luminosities and colors of stars, extending work done in 1911 by Ejnar Hertzsprung.
Big Bang by Simon Singh
Albert Einstein, Albert Michelson, All science is either physics or stamp collecting, Andrew Wiles, anthropic principle, Arthur Eddington, Astronomia nova, Brownian motion, carbon-based life, Cepheid variable, Chance favours the prepared mind, Commentariolus, Copley Medal, cosmic abundance, cosmic microwave background, cosmological constant, cosmological principle, dark matter, Dava Sobel, Defenestration of Prague, discovery of penicillin, Dmitri Mendeleev, Edmond Halley, Edward Charles Pickering, Eratosthenes, Ernest Rutherford, Erwin Freundlich, Fellow of the Royal Society, fudge factor, Hans Lippershey, Harlow Shapley and Heber Curtis, Harvard Computers: women astronomers, Henri Poincaré, horn antenna, if you see hoof prints, think horses—not zebras, Index librorum prohibitorum, invention of the telescope, Isaac Newton, Johannes Kepler, John von Neumann, Karl Jansky, Kickstarter, Louis Daguerre, Louis Pasteur, luminiferous ether, Magellanic Cloud, Murray Gell-Mann, music of the spheres, Olbers’ paradox, On the Revolutions of the Heavenly Spheres, Paul Erdős, retrograde motion, Richard Feynman, scientific mainstream, Simon Singh, Solar eclipse in 1919, Stephen Hawking, the scientific method, Thomas Kuhn: the structure of scientific revolutions, unbiased observer, Wilhelm Olbers, William of Occam
But at least the women could now examine the photographic results of night-time observations and contribute to astronomy, a discipline that had largely excluded them in the past. Figure 43 The Harvard ‘computers’ at work, busy examining photographic plates while Edward Pickering and Williamina Fleming watch over them. On the back wall are two plots that show the oscillating brightness of stars. Although Williamina Fleming’s team of women computers were supposed to focus on the drudgery of harvesting data from the photographs so that the male astronomers could conduct the research, it was not long before they were reaching their own scientific conclusions. Endless days spent staring at the photographic plates had given them an intimate familiarity with the stellar objects that they were surveying. For example, Annie Jump Cannon catalogued roughly 5,000 stars per month between 1911 and 1915, calculating the location, brightness and colour of each one.
He was still blocked from conducting military research, but within a few months his curfew was lifted and Baade had complete control of the world’s best telescope under ideal viewing conditions. He also made the most of the increasingly sensitive photographic plates that were becoming available, creating images of unparalleled sharpness. Baade spent the war years studying a particular type of star known as an RR Lyrae star, a type of variable star similar to a Cepheid variable star. Williamina Fleming, who worked alongside Henrietta Leavitt at the Harvard Observatory, had shown that the variability of RR Lyrae stars could be used, like Cepheids, to measure distances. So far her technique had been used only within the Milky Way, because RR Lyrae stars are less luminous than Cepheids. However, Baade’s ambition was to use the ideal viewing conditions to find RR Lyrae stars in the Andromeda Galaxy, our nearest large galaxy.
Bailey, History and Work of the Harvard Observatory 1839-1927 (McGraw Hill, 1931) An interesting and largely non-technical (if somewhat dry) account of the research projects pursued at the Harvard College Observatory from its founding until the mid-1920s. It covers the work of Henrietta Leavitt and Annie Jump Canon, and explains the techniques and instruments they employed. Harry G. Lang, Silence of the Spheres (Greenwood Press, 1994) Subtitled The Deaf Experience in the History of Science, this book includes sections on John Goodricke and Henrietta Leavitt. Edwin Powell Hubble, The Realm of the Nebulae (Yale University Press, 1982) A somewhat technical book, based on the 1935 Silliman Lectures delivered by Hubble at Yale University. It is an interesting snapshot of cosmology soon after Hubble’s major breakthroughs.
Broad Band: The Untold Story of the Women Who Made the Internet by Claire L. Evans
"side hustle", 4chan, Ada Lovelace, Albert Einstein, British Empire, colonial rule, computer age, crowdsourcing, dark matter, dematerialisation, Doomsday Book, Douglas Engelbart, Douglas Engelbart, Douglas Hofstadter, East Village, Edward Charles Pickering, game design, glass ceiling, Grace Hopper, Gödel, Escher, Bach, Haight Ashbury, Harvard Computers: women astronomers, Honoré de Balzac, Howard Rheingold, HyperCard, hypertext link, index card, information retrieval, Internet Archive, Jacquard loom, John von Neumann, Joseph-Marie Jacquard, knowledge worker, Leonard Kleinrock, Mahatma Gandhi, Mark Zuckerberg, Menlo Park, Mother of all demos, Network effects, old-boy network, On the Economy of Machinery and Manufactures, packet switching, pets.com, rent control, RFC: Request For Comment, rolodex, semantic web, Silicon Valley, Skype, South of Market, San Francisco, Steve Jobs, Steven Levy, Stewart Brand, subscription business, technoutopianism, Ted Nelson, telepresence, Whole Earth Catalog, Whole Earth Review, women in the workforce, Works Progress Administration, Y2K
In the 1880s, for example, the astronomer Edward Charles Pickering hired only women to analyze and classify stellar data for his Harvard lab, including his own maid, Williamina Fleming. Although he would later champion the women working in the observatory, even presenting papers on Fleming’s behalf at astronomical conferences, Pickering didn’t hire them out of advocacy. He’d just wanted twice as many workers on the job, given that women were paid half the going rate. “The Harvard Computers are mostly women,” complained the director of a competing observatory, which employed only men, to a colleague, and they can be “got to work for next to nothing.” Known to history as “Pickering’s Harem,” the Harvard Computers cataloged ten thousand stars; Williamina Fleming, the erstwhile maid, discovered the Horsehead Nebula and helped develop a common designation system for stars, while her colleague Annie Jump Cannon could classify spectra at a rate of three stars a minute, and with a remarkable consistency that allowed her to discover a number of new and unusual stars.
AIQ: How People and Machines Are Smarter Together by Nick Polson, James Scott
Air France Flight 447, Albert Einstein, Amazon Web Services, Atul Gawande, autonomous vehicles, availability heuristic, basic income, Bayesian statistics, business cycle, Cepheid variable, Checklist Manifesto, cloud computing, combinatorial explosion, computer age, computer vision, Daniel Kahneman / Amos Tversky, Donald Trump, Douglas Hofstadter, Edward Charles Pickering, Elon Musk, epigenetics, Flash crash, Grace Hopper, Gödel, Escher, Bach, Harvard Computers: women astronomers, index fund, Isaac Newton, John von Neumann, late fees, low earth orbit, Lyft, Magellanic Cloud, mass incarceration, Moneyball by Michael Lewis explains big data, Moravec's paradox, more computing power than Apollo, natural language processing, Netflix Prize, North Sea oil, p-value, pattern recognition, Pierre-Simon Laplace, ransomware, recommendation engine, Ronald Reagan, self-driving car, sentiment analysis, side project, Silicon Valley, Skype, smart cities, speech recognition, statistical model, survivorship bias, the scientific method, Thomas Bayes, Uber for X, uber lyft, universal basic income, Watson beat the top human players on Jeopardy!, young professional
Decades later, in 1990, when the space shuttle Discovery carried the Hubble Space Telescope into low Earth orbit, it also carried something whose value was entirely sentimental: a copy of Hubble’s original photograph of V1 from 1923.8 It was a photograph that made Hubble a household name and that changed the course of astronomy forever. But it was also a photograph whose significance Hubble could have seen only by standing on the shoulders of Henrietta Leavitt—for she was the one who showed Hubble, and everyone else, how to measure the size of the universe. Fitting Prediction Rules to Data We’ll return to the story of Henrietta Leavitt at the very end of the chapter. For now, however, let’s keep her great discovery in mind as we revisit the two key ideas about pattern recognition that we mentioned at the beginning of the chapter. 1. In AI, a “pattern” is a prediction rule that maps an input to an output. 2. “Learning a pattern” means fitting a good prediction rule to a data set. We hope that Henrietta Leavitt’s pulsating stars have taught you the value of a good prediction rule for describing a pattern. But we also expect that you still have some questions.
Therefore, both sides recognized that no matter who was right, the distance to Andromeda was too far to measure using parallax. Astronomers were desperate for a better way to measure distance, but nobody had one. Nobody had one, that is, until a little-known astronomer named Henrietta Leavitt made a wonderful discovery. Leavitt found a new prediction rule that would allow astronomers to measure distances over millions of light-years, much farther than they had ever thought possible. She didn’t find the rule using trigonometry, the way the parallax rule had been found. Instead, she found it using data, by applying the same principle that Google, Apple, and Facebook use today to build their pattern-recognition systems. Leavitt’s Great Discovery Henrietta Leavitt ended up as an astronomer almost by chance. Born into a large family in Lancaster, Massachusetts, in 1868, she entered Radcliffe College in 1888 to study the humanities.
Postscript We’ll close with one final story about stereotypes—one especially relevant to a world in which only 17% of computer-science majors at American universities are women, a fraction that’s been declining for decades. You’ll recall that Edwin Hubble used Henrietta Leavitt’s prediction rule for pulsating stars—the standard candles of the universe—to prove conclusively that the Milky Way wasn’t the only galaxy out there. In doing so, he settled a question that astronomers had debated for centuries. When he announced his discovery to the world, Hubble became an instant celebrity. Scientists and journalists clamored for his attention. He would go on to win medals and prizes, to walk among movie stars and heads of state, to have Einstein call at his home, and to have a great telescope that orbits Earth named in his honor. None of these plaudits went to Henrietta Leavitt. She died of cancer in 1921, four years before Hubble announced his discovery. Professional astronomers, all of them men, certainly knew about her breakthrough equation that showed them how to use pulsating stars to measure the size of the universe.
A Short History of Nearly Everything by Bill Bryson
Albert Einstein, Albert Michelson, Alfred Russel Wallace, All science is either physics or stamp collecting, Arthur Eddington, Barry Marshall: ulcers, Brownian motion, California gold rush, Cepheid variable, clean water, Copley Medal, cosmological constant, dark matter, Dava Sobel, David Attenborough, double helix, Drosophila, Edmond Halley, Ernest Rutherford, Fellow of the Royal Society, Harvard Computers: women astronomers, Isaac Newton, James Watt: steam engine, John Harrison: Longitude, Kevin Kelly, Kuiper Belt, Louis Pasteur, luminiferous ether, Magellanic Cloud, Menlo Park, Murray Gell-Mann, out of africa, Richard Feynman, Stephen Hawking, supervolcano, Thomas Malthus, Wilhelm Olbers
Hubble's luck was to come along soon after an ingenious woman named Henrietta Swan Leavitt had figured out a way to do so. Leavitt worked at the Harvard College Observatory as a computer, as they were known. Computers spent their lives studying photographic plates of stars and making computations—hence the name. It was little more than drudgery by another name, but it was as close as women could get to real astronomy at Harvard—or indeed pretty much anywhere—in those days. The system, however unfair, did have certain unexpected benefits: it meant that half the finest minds available were directed to work that would otherwise have attracted little reflective attention, and it ensured that women ended up with an appreciation of the fine structure of the cosmos that often eluded their male counterparts. One Harvard computer, Annie Jump Cannon, used her repetitive acquaintance with the stars to devise a system of stellar classifications so practical that it is still in use today.
Bodanis, E = mc2, p. 83. 26 “the ultimate sagging mattress . . .” Overbye, p. 55. 27 “In some sense, gravity does not exist . . .” Kaku, “The Theory of the Universe?” in Shore, Mysteries of Life and the Universe, p. 161. 28 “Edwin enjoyed a wealth of physical endowments, too.” Cropper, p. 423. 29 “At a single high school track meet . . .” Christianson, Edwin Hubble, p. 33. 30 “One Harvard computer, Annie Jump Cannon . . .” Ferris, Coming of Age in the Milky Way, p. 258. 31 “elderly stars that have moved past their ‘main sequence phase' . . .” Ferguson, Measuring the Universe, pp. 166–67. 32 “They could be used as ‘standard candles' . . .” Ferguson, p. 166. 33 “was developing his seminal theory . . .” Moore, Fireside Astronomy, p. 63. 34 “In 1923 he showed that a puff of distant gossamer . . .” Overbye, p. 45; and Natural History, “Delusions of Centrality,” December 2002–January 2003, pp. 28–32. 35 “no one had hit on the idea of the expanding universe before.”
The Cancer Chronicles: Unlocking Medicine's Deepest Mystery by George Johnson
Atul Gawande, Cepheid variable, Columbine, dark matter, discovery of DNA, double helix, Drosophila, epigenetics, Gary Taubes, Harvard Computers: women astronomers, Isaac Newton, Magellanic Cloud, meta analysis, meta-analysis, microbiome, mouse model, Murray Gell-Mann, phenotype, profit motive, stem cell
I was surprised how easy it was to roam at random without a hospital ID. I walked outside, where orderlies and other staff stood smoking cigarettes. I walked by the emergency room, where victims of knives, automobiles, and guns arrived in ambulances. I walked back up the steps to the surgical floor and sat again. I took out my laptop and tried to work on a book I was writing. It was about Henrietta Leavitt, the woman who in the early 1900s discovered the blinking stars astronomers use as beacons to measure the emptiness of the universe. She died, childless, of stomach cancer. Before long Nancy’s brother arrived. The earth had continued to rotate and it was dark outside. The cafeteria closed, and the lights were turned off. We were shooed into a hallway where a family—the only other visitors still on the floor—waited for the outcome of someone else’s long surgery.
Suppose you have two patients with the same kind of cancer. One responds to a drug and the other does not. Using a device like Hillis’s, you could take their proteomic snapshots and lay one on top of the other and look for something that is different. Even if you don’t know what the pattern means, it might be used as a marker to identify which patients will most likely benefit from the drug. I was reminded of Henrietta Leavitt, the astronomer who had died of stomach cancer but not before discovering Cepheid variables, the pulsating stars cosmologists use to measure the universe. She would start with two images of the same patch of sky—glass photographic plates taken a few weeks apart. One would be a negative with the stars glowing in black. She would place that plate on top of the other and hold the glass sandwich to the light.
Extraterrestrial Civilizations by Isaac Asimov
Albert Einstein, Cepheid variable, Columbine, Edward Charles Pickering, Harvard Computers: women astronomers, invention of radio, invention of the telescope, invention of writing, Isaac Newton, Johannes Kepler, Louis Pasteur, Magellanic Cloud, Search for Extraterrestrial Intelligence
They were first described in 1521 by the chronicler accompanying Magellan’s voyage of circumnavigation of the globe—so they are called the Large Magellanic Cloud and the Small Magellanic Cloud. They were not studied in detail until John Herschel observed them from the astronomic observatory at the Cape of Good Hope in 1834 (the expedition that fueled the Moon Hoax). Like the Milky Way, the Magellanic Clouds turned out to be assemblages of vast numbers of very dim stars, dim because of their distance. In the first decade of the twentieth century, the American astronomer Henrietta Swan Leavitt (1868–1921) studied certain variable stars in the Magellanic Clouds. By 1912, the use of these variable stars (called Cepheid variables because the first to be discovered was in the constellation Cepheus) made it possible to measure vast distances that could not be estimated in other ways. The Large Magellanic Cloud turned out to be 170,000 light-years away and the Small Magellanic Cloud 200,000 light-years away.
Origin Story: A Big History of Everything by David Christian
Albert Einstein, Arthur Eddington, butterfly effect, Capital in the Twenty-First Century by Thomas Piketty, Cepheid variable, colonial rule, Colonization of Mars, Columbian Exchange, complexity theory, cosmic microwave background, cosmological constant, creative destruction, cuban missile crisis, dark matter, demographic transition, double helix, Edward Lorenz: Chaos theory, Ernest Rutherford, European colonialism, Francisco Pizarro, Haber-Bosch Process, Harvard Computers: women astronomers, Isaac Newton, James Watt: steam engine, John Maynard Keynes: Economic Possibilities for our Grandchildren, Joseph Schumpeter, Kickstarter, Marshall McLuhan, microbiome, nuclear winter, planetary scale, rising living standards, Search for Extraterrestrial Intelligence, Stephen Hawking, Steven Pinker, The Wealth of Nations by Adam Smith, Thomas Kuhn: the structure of scientific revolutions, trade route, Yogi Berra
Unfortunately, even the nearest star, Proxima Centauri, is so distant (about four light-years from Earth) that you cannot detect any motion without fancy equipment. Not until the nineteenth century were astronomers able to measure the distance to nearby stars using parallax. But in any case, the objects Vesto Slipher was studying were much more distant. Fortunately, in the early twentieth century, Henrietta Leavitt, a Harvard Observatory astronomer, found a way to measure the distance to remote stars and nebulae using a particular type of star known as a Cepheid variable, a star whose brightness varies with great regularity (the polestar is a Cepheid). She found a simple correlation between the frequency of the variations and the star’s luminosity, or brightness, so she could calculate a Cepheid’s absolute brightness.
Fool Me Twice: Fighting the Assault on Science in America by Shawn Lawrence Otto
affirmative action, Albert Einstein, anthropic principle, Berlin Wall, Brownian motion, carbon footprint, Cepheid variable, clean water, Climategate, Climatic Research Unit, cognitive dissonance, Columbine, commoditize, cosmological constant, crowdsourcing, cuban missile crisis, Dean Kamen, desegregation, different worldview, double helix, energy security, Exxon Valdez, fudge factor, ghettoisation, global pandemic, Harlow Shapley and Heber Curtis, Harvard Computers: women astronomers, informal economy, Intergovernmental Panel on Climate Change (IPCC), invisible hand, Isaac Newton, Louis Pasteur, mutually assured destruction, Richard Feynman, Ronald Reagan, Saturday Night Live, shareholder value, sharing economy, smart grid, Solar eclipse in 1919, stem cell, the scientific method, The Wealth of Nations by Adam Smith, Thomas Kuhn: the structure of scientific revolutions, transaction costs, University of East Anglia, War on Poverty, white flight, Winter of Discontent, working poor, yellow journalism, zero-sum game
What he saw changed humanity’s view of the universe forever—and would further roil the controversy over science’s role in defining the origins of creation. A conservative Baconian observer, Hubble photographed a small blinking star in the Andromeda nebula that he identified as a Cepheid variable. This observation would become iconic in its power. Another astronomer, Harvard College Observatory’s Henrietta Leavitt, had in 1912 shown something remarkable about Cepheid variable stars: The longer their period, the brighter they appeared to be. This made sense. Stars were very faint, and to probe deeply, astronomers began to mount cameras to their telescopes and take very-long-exposure photographs on glass plates so they could capture light from stars that were too faint to see with the human eye. A blinking star that has a longer “on” period deposits more light on the plate than one with a shorter period.
What We Cannot Know: Explorations at the Edge of Knowledge by Marcus Du Sautoy
Albert Michelson, Andrew Wiles, Antoine Gombaud: Chevalier de Méré, Arthur Eddington, banking crisis, bet made by Stephen Hawking and Kip Thorne, Black Swan, Brownian motion, clockwork universe, cosmic microwave background, cosmological constant, dark matter, Dmitri Mendeleev, Edmond Halley, Edward Lorenz: Chaos theory, Ernest Rutherford, Georg Cantor, Hans Lippershey, Harvard Computers: women astronomers, Henri Poincaré, invention of the telescope, Isaac Newton, Johannes Kepler, Magellanic Cloud, mandelbrot fractal, MITM: man-in-the-middle, Murray Gell-Mann, music of the spheres, Necker cube, Paul Erdős, Pierre-Simon Laplace, Richard Feynman, Skype, Slavoj Žižek, Solar eclipse in 1919, stem cell, Stephen Hawking, technological singularity, Thales of Miletus, Turing test, wikimedia commons
Now astronomers could look at the stars whose distances were too far away to apply parallax. By measuring the missing frequencies and their apparent luminosity, astronomers could work out how far the stars were from us. This gave astronomers a much clearer idea of the true depth of space. However, it was a very special pulsating star that turned out to provide the best way to measure distances across the universe. A Cepheid star twinkles, and in 1912 American astronomer Henrietta Leavitt discovered how to use these twinkling stars to navigate the universe. She was employed at the time not as an astronomer but as a ‘computer’ at the Harvard College Observatory, extracting data from the photographic plates for 30 cents an hour. Women weren’t allowed to operate the telescopes. She’d been assigned the task of analysing stars that grew brighter and dimmer over a period of time.
Elemental: How the Periodic Table Can Now Explain Everything by Tim James
Twenty-seven years later, William Ramsay extracted it from terrestrial rocks, making it the only element to be discovered in space before it was isolated on Earth.7 The next breakthrough happened in 1925 when the American astronomer Cecilia Payne-Gaposchkin successfully calculated how much of each element was present in a typical star. Payne-Gaposchkin studied astrophysics at Harvard under Harlow Shapley, one of the only astronomers in the world to let women take the subject, and wrote her PhD thesis on the star classes identified by another astronomer, Annie Jump Cannon (possibly the greatest name in science). Cannon was completing her nine-volume catalog of every known star when Payne-Gaposchkin began perusing the data. Being well versed in the new science of quantum mechanics (which most astronomers weren’t), Payne-Gaposchkin showed that the amounts of each element in stars were vastly different to the amounts found on Earth. Stars weren’t just hot planets, as was suggested by the world’s leading astronomer Henry Norris Russell, they were something else entirely.8 On Earth, the most abundant elements are oxygen, silicon, aluminum, and iron but stars are made almost entirely from hydrogen and helium.