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The hourglass uses the flow of sand to measure the flow of time. They were used in navigation. Ferdinand Magellan used 18 glasses on each ship for his circumnavigation of the globe (1522). Incense sticks and candles were, and are, commonly used to measure time in temples and churches across the globe. Waterclocks, and later, mechanical clocks, were used to mark the events of the abbeys and monasteries of the Middle Ages. Richard of Wallingford (1292–1336), abbot of St. Alban's abbey, famously built a mechanical clock as an astronomical orrery about 1330. Great advances in accurate time-keeping were made by Galileo Galilei and especially Christiaan Huygens with the invention of pendulum driven clocks along with the invention of the minute hand by Jost Burgi.

Who is credited with the invention of the minute hand?
Answer: Jost Burgi.
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Before World War II, Guam and three other territories – American Samoa, Hawaii, and the Philippines – were the only American jurisdictions in the Pacific Ocean. On December 7, 1941, hours after the attack on Pearl Harbor, Guam was captured by the Japanese, and was occupied for thirty months. During the occupation, Guamanians were subjected to culture alignment, forced labor, beheadings, rape, and torture. Guam endured hostilities when American forces recaptured the island on July 21, 1944; Liberation Day commemorates the victory. Since the 1960s, the economy is supported by two industries: tourism and the United States Armed Forces.

How long did the Japanese occupation last?
Answer: thirty months
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Since the 1970s, an important focus of study has been the ozone layer in the atmosphere above Antarctica. In 1985, three British scientists working on data they had gathered at Halley Station on the Brunt Ice Shelf discovered the existence of a hole in this layer. It was eventually determined that the destruction of the ozone was caused by chlorofluorocarbons (CFCs) emitted by human products. With the ban of CFCs in the Montreal Protocol of 1989, climate projections indicate that the ozone layer will return to 1980 levels between 2050 and 2070.

What chemical was discovered to have caused the hole in the ozone?
Answer:
chlorofluorocarbons