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  • The Eclipse of the Century:A Story of Science, Money, and Culture in Saharan Africa and the American Southwest
  • David A. Conrad (bio)

Cécile DeWitt-Morette sat on a roof in a sandstorm in the Sahara Desert. It was 10:30 a.m. on June 30, 1973, and nearly 100 degrees Fahrenheit. If the storm did not let up soon, all was lost. A year and a half of preparation and approximately $100,000 in grants would be for naught, and a similar opportunity would not come for another 18 years. But Cécile had no power over the wind or sand or time. She could only wait. Beneath her feet, inside the structure she and her colleagues from the University of Texas (UT) McDonald Observatory built, her husband Bryce DeWitt—head of the expedition—and five other men waited for the storm to abate. The clock ticked off the seconds, and still the sand blew. All the money and effort spent to send these people here, to the oasis of Chinguetti in the Islamic Republic of Mauritania, could not alter the forces of nature.1

It was a natural phenomenon, but not a terrestrial one, that brought these researchers to Africa. Sandstorm or no, at 10:45:41 a.m. the sun would go dark as the moon passed directly between it and Chinguetti. A brief, dusky night would fall over the oasis, and stars would appear in the sky. This total solar eclipse offered a rare opportunity to photograph, through an Earth-based telescope, the sun and distant background stars simultaneously. If the resulting images were of sufficiently high quality, physicists and astronomers could use them to solve a decades-old physics problem. This problem concerned perhaps the most famous scientist of all time, Albert Einstein, and his influential theory of relativity.2

Einstein’s theory, the key ideas of which he formulated between 1905 and 1916, in part described how the gravity of a massive object like the [End Page 603] sun warped the space around it. This gravitational distortion caused everything, including light itself, to bend toward the massive body. By the 1970s, no serious scientist objected to Einstein’s ideas in principle. But there was still substantial disagreement over just how severely gravity bent light. If Einstein’s prediction of the value of this “light deflection” was correct, then his theory of relativity might describe the true nature of the physical universe. If, on the other hand, his theory predicted a light deflection value that was substantially greater or less than that which occurs in reality, as some scientists suspected, then Einstein’s model would contain serious flaws.3

For decades, solar eclipses offered the best chance to observe the gravitational deflection of starlight in action. Usually, the sun makes all other stars impossible to see through Earth’s atmosphere. But during a total eclipse, in which the moon blocks nearly all of the sun’s light over a particular spot on Earth, stars in the background of the sun become visible. The stars appear to occupy a slightly different space in the sky than they do when the sun is not there to warp their light. The first opportunity to measure this phenomenon during a solar eclipse came in 1919. That year, a total solar eclipse took place over Brazil, the Portuguese-controlled island of Principe, and parts of French and Belgian Africa. Britain’s Royal Greenwich Observatory sent astronomers to some of these far-flung locales to photograph the event. However, the equipment and techniques of the day were insufficient to determine the deflection of light with precision. For the moment, Einstein’s theories outmatched scientists’ ability to test them.4

The scientists who endured a Saharan sandstorm in 1973 hoped to set the record straight at last. Ten minutes before totality, the moment the moon completely covers the sun, the wind finally stopped. The sky still contained loads of fine sand particles, but Cécile saw the dark disk of the eclipsed sun from the roof of the hut that housed the team’s telescope and photographic equipment. The team prepared for totality. At 10:45:41 it happened, and everyone...


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