science: The Americas the customer’s dish is mounted, it has to be pointed at the satellite; otherwise, it fails to pick up the signal But satellite dish installers not have a single, fi xed angle at which they mount the dish This is because while the satellite is in a fi xed place relative to the horizon, usually over the equator, homes are located at various points north or south of the equator For a home near the equator, the satellite dish would have to point upward at a severe angle; for homes in Alaska, the dish would point at a much lower, flatter angle This angle is the azimuth Like the azimuths used to point to satellites, the azimuths of the sun at the summer and winter solstices—that is, the dates when the sun is highest in the sky in summer and lowest in the sky in winter—differ depending on latitude Evidence shows that many ancient American structures were positioned with their angles lined up with the point in the sky that marked the azimuths of the summer and winter solstices The purpose in doing so was probably part religious, part practical From a religious perspective, it reflected the ancient Americans’ view that all of creation is unified From a practical perspective, it enabled ancient Americans to take maximum advantage of light and warmth from the sun SOUTH AMERICA: THE SEARCH FOR RESOURCES The ancient South Americans, particularly the people of Peruvian Andes, made remarkable technical advances in metalwork, agriculture, and energy production, all based on early understanding of science In the field of metallurgy, archaeologists have discovered that the Peruvians began to exploit deposits of copper beginning sometime around 1400–1100 b.c.e They created an alloy called tumbaga, which was a mixture of gold and copper, though the ratio of these elements varied widely, from 97 percent copper to 97 percent gold A chief technical innovation was adding the element mercury, which hardened the metal and made it more durable Additionally, the Peruvians found gold and silver resources and developed complex technologies for mining, purifying, smelting, and craft ing them into useful and decorative objects Along the way they found uses for other minerals they mined, including hematite (an iron oxide), limonite (a mineral with various combinations of other minerals, including hematite), and manganese oxide The many varieties of hematite, including rainbow hematite, kidney ore, martite, bloodstone, iron rose, and paint ore, suggest that depending on the mineral’s composition, it had different appearances, making it a versatile mineral for objects with differing aesthetic properties With regard to energy, the ancient Americans, like people throughout the world, burned wood, along with dried dung and charcoal In time, however, they also discovered and mined coal, particularly as some of the forests became depleted Archaeologists disagree about whether the Peruvians used coal in the metal-smelting process Some argue that little evidence suggests that they did, but others claim to have found coal ash in ancient Peruvian smelting sites The Peruvians also found uses for bitumen, a substance that is similar 949 to asphalt or tar and can occur naturally or as a byproduct of a refining process The Peruvians used this sticky material as a sealant in coffins and as caulking for ships The effectiveness of that sealant, along with the Peruvians’ skill in mummifying bodies, has given modern scientists unique insight into the physical condition of the ancient Peruvians The Peruvians learned to make use of guano, or bat dung, on nearby islands as fertilizer Guano is still used as a fertilizer because it is high in nitrogen, phosphate, and potassium, all substances essential to healthy plant growth and abundant crops It is believed that the Peruvians used small reed boats to travel to the islands and transport the guano back to the mainland for use on fields In some places the guano is believed to have been as much as 65 feet thick MEDICINE An important part of the scientific achievements of any civilization is its ability to find treatments for illness and disease Again, much of what might have been known about medical lore in ancient Mesoamerica has been lost because the invading Spaniards destroyed the manuscripts that recorded their various branches of knowledge Some of this ancient knowledge was later reconstructed, and modern paleopathologists—those who study disease and illness by examining preserved tissues from ancient times—have been able to add to that knowledge Generally, medical practitioners in the ancient Americas were shamans Like the astronomer-shamans discussed earlier, shamans who practiced medicine were believed to have had access to supernatural power and wisdom In common with ancient civilizations the world over, the ancient Americans made wide use of herbs and other medicinal plants One early colonial manuscript catalogues 204 medicinal plants from a wide variety of climate zones While this manuscript was copied much later, it doubtless reflects insights into medicinal cures that were hundreds, if not thousands, of years old Modern people who think of themselves as addicted to chocolate might take heart in knowing that ancient healers of Mesoamerica recognized the therapeutic benefits of chocolate and cacao They used it not only to deliver other medicines but as a medicine in its own right It was thought to help people gain weight, stimulate the nervous system, and improve digestion and elimination Ancient Americans also used cacao to treat anemia, poor appetite, gout, kidney stones, fevers, and, in paste form, burns Interestingly, modern medical researchers have confirmed what the ancient Americans knew Chocolate has been shown to be an effective cough medicine More important, consumed in moderation, it is a good source of polyphenols—chemicals that protect the heart See also agriculture; architecture; astronomy; building techniques and materials; calendars 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