Digital SAT: Fact 1

1. In the early 1900s, astronomer Henrietta Swan Leavitt studied thousands of stars recorded on photographic plates at the Harvard College Observatory. She noticed that for a certain type of variable star, those with longer periods of brightening and dimming were intrinsically brighter than those with shorter periods. Because astronomers could measure how long a star took to complete its cycle, Leavitt’s finding gave them a way to estimate how far away such stars were.

According to the text, why was Leavitt’s discovery useful to astronomers?

2. During the construction of the Panama Canal in the early twentieth century, workers faced major outbreaks of mosquito-borne diseases such as yellow fever and malaria. Physician William Gorgas organized large-scale sanitation efforts that included draining standing water, fumigating buildings, and installing window screens in living quarters. After these measures were introduced, disease rates among workers declined substantially, allowing construction to proceed more efficiently.

According to the text, how did Gorgas help canal construction continue more effectively?

3. In the 1700s, watchmaker John Harrison worked to solve one of the greatest navigation problems of his era: determining longitude at sea. While sailors could estimate latitude relatively easily, accurately measuring longitude required knowing the precise time difference between a ship’s location and a fixed reference point. Harrison designed increasingly accurate portable clocks that continued keeping reliable time even during long ocean voyages. His inventions eventually allowed navigators to calculate longitude much more precisely.

According to the text, why were Harrison’s clocks important to navigation?

4. In the nineteenth century, mathematician Ada Lovelace wrote notes about Charles Babbage’s proposed Analytical Engine, a mechanical device designed to perform calculations. In one note, Lovelace described a method by which the machine could calculate a sequence of Bernoulli numbers. More broadly, she recognized that the machine might one day manipulate symbols according to rules, not merely perform arithmetic with numbers.

According to the text, what was significant about Lovelace’s view of the Analytical Engine?

5. In the late nineteenth century, photographer Eadweard Muybridge used a series of cameras placed along a racetrack to study animal movement. When a horse ran past the cameras, it triggered each one in sequence, producing separate images that showed different moments in the horse’s stride. These photographs helped settle a debate about whether all four of a galloping horse’s hooves ever leave the ground at the same time.

According to the text, how did Muybridge’s camera setup help answer a question about horse movement?

6. In the early twentieth century, physicist Lise Meitner worked with chemist Otto Hahn to study the behavior of uranium atoms when they were struck by neutrons. After Hahn’s experiments produced barium, a much lighter element, Meitner and her nephew Otto Frisch interpreted the result: the uranium nucleus had split into smaller parts, releasing a large amount of energy. They named this process nuclear fission.

According to the text, what role did Meitner and Frisch play in understanding Hahn’s experiment?

7. In the 1800s, geologist Mary Anning uncovered numerous fossils along the cliffs near Lyme Regis, England. Among her most important finds were nearly complete skeletons of marine reptiles that had lived millions of years earlier. At the time, some scientists argued that unfamiliar fossils were simply remains of animals still living somewhere on Earth, but Anning’s discoveries helped support the idea that entire species had disappeared from the planet.

According to the text, why were Anning’s fossil discoveries important?

8. In the 1950s, computer scientist Grace Hopper helped develop one of the first compilers, a program that translates instructions written in a more human-readable form into machine code that a computer can execute. At the time, many programmers believed computers should be programmed only with numerical instructions closely tied to the machine’s hardware. Hopper argued instead that programming languages should be easier for people to read and write, making computers more accessible to a wider range of users.

According to the text, why was Hopper’s work on compilers important?

9. In the 1930s, engineer Beatrice Hicks worked on devices that could sense changes in pressure and activate electrical controls in response. One of her inventions was a gas-density switch, which helped detect when sealed electrical equipment was leaking insulating gas. Because such leaks could make the equipment less reliable or unsafe, Hicks’s device gave operators a way to identify problems before the equipment failed.

According to the text, why was Hicks’s gas-density switch useful?

10. In the early twentieth century, agricultural scientist George Washington Carver encouraged farmers in the American South to plant crops such as peanuts, sweet potatoes, and cowpeas. Many farmers had grown cotton year after year, a practice that depleted nutrients from the soil. Carver promoted alternative crops partly because they could help restore soil fertility while also giving farmers products they could sell or use at home.

According to the text, why did Carver recommend that farmers grow crops other than cotton?