Celestial Motion: Understanding the Ancient Theories of the Universe - Prof. Yelle, Papers of Astronomy

Download Celestial Motion: Understanding the Ancient Theories of the Universe - Prof. Yelle and more Papers Astronomy in PDF only on Docsity! More about Celestial Motion “The reality which scientific thought is seeking must be expressionable in mathematical terms, mathematics being the most precise and definite kind of thinking that we are capable of” -- Plato This photo from space demonstrates pretty well that the Earth is round. NASA to beam Beatles song to « Montoy, NASA wi North Star > The North Stor Pe It will take 431 yea Ment Articie In Techn TEXT SIZE WASHINGTON (AP) — The Beatles are about to become radio stars. in a whole mew wary. NASA on Monday will broadcast the Beathes' song "Across the Universe" across the galaxy to Polaris, fhe North Star. This first-ever beaming of a radio song by the space agency directly inio deep space is nostalgia-driven. lt celebrates the 40th anniversary of the song, the 45th anniversary of NASA's Deep Space Network, which communicates with its distant probes, and fhe 50th anniversary of MASA. "Send my love to the aliens," Paul McCartney told MASA through a Beatles historian. “All fhe best, Paul." The song, written by McCartney and John Lennon, may have a ticket to ride and will be flying at the speed of light. But tt will take 43:1 years along a long and winding road to reach its final destination. That's because Polaris is 2.5 quadriliion miles away. Polaris Facts Polaris is 431 light years away from Earth. Light travels at 3.0×108 m/s (meters per second) 431 years = 431 × 3.1×107 seconds/year = 1.3×1010 s Distance = velocity x time Distance = 3.0×108 m/s x 1.3×1010 s = 4.0×1018 m Polaris is 0.7 degrees away from the Earth’s rotation pole and so moves only slightly as the Earth’s rotate. Metric System and SI units • Metric system refers to use of meters or kilometers, grams, or kilograms, centigrade, etc. irrespective of prefix. • SI (System Internationale) refers to a very specific set of units including only meters (not kilometers), kilograms (not grams), Kelvins. ae MAIN PAGE WORLD us. LOCAL POLITICS WEATHER BUSINESS SPORTS TECHNOLOGY HEALTH ENTERTAINMENT BOOKS TRAVEL FOOD ARTS & STYLE NATURE IN-DEPTH ANALYSIS Headline News brief news quiz daily almanac video video archive audio multimedia showcase scitech> space> story page explodagmanrs. Metric mishap caused loss of NASA orbiter September 30, 1999 Web posted at: 4:21 p.m. EDT (2021 GMT) [in-depthspocials|€ eee In this story: Metric system used by NASA for many years Error points to nation's conversion lag RELATED STORIES, SITES ¥ NASA’s Climate Orbiter was lost September 23, 1999 By Robin Lloyd CNN Interactive Senior Writer (CNN) -- NASA lost a $125 million Mars orbiter because a Lockheed Martin engineering team used English units of measurement while the agency's team used the more conventional metric system for a key spacecraft operation, according to a review finding released Thursday. Why do we believe that the Earth is round? Your suggestions please…using only low technology observations… Aristotle (384-322 BC) A student of Plato, but quite different in his approach. Used physical arguments to explain nature. For example, the Earth must be a sphere because; • ships disappear over the horizon, • the shadow of Earth on the moon is round, •travelers see new stars above the horizon. Earth's shadow A Sunlight Figure 3.6 Curvature of the Earth’s shadow on the Moon. Only a spherical body can cast a circular shadow for all alignments of the Sun, Moon, and Earth. l = Distance from Alexandria to Syene D = Circumference of the Earth l = (7.2/360)*D l = 5000 stades D=(360/7.2)*l D=250,000 stades 1 stade = 157 meters (a Greek stadium at, for example, Olympia) D=157*250000 meters D=39,250,000 meters D = 39,250 kilometers Modern Value = 40,070 kilometers SIZE OF THE EARTH Moon Movie Phases of the Moon Figure from Astronomy Today by Chaisson and McMillan Planets known to the Ancients • Mercury (Hermes), dim and close to the horizon, Mercury is difficult to see. He moves quickly across the sky. Messenger of the gods. • Venus (Aphrodite), the morning and evening star, very bright but variable, goddess of love. • Mars (Ares), the red planet, god of war. • Jupiter (Zeus), very bright, king of the gods. • Saturn (Kronos), bright and pale yellow, first of the Titan’s, father of Zeus. Layout of the Solar System From Astronomy: from the Earth to the Universe by Pasachoff Retrograde Motion The Movie Arguments for a Geocentric Universe • If the Earth were moving, we would have a sense of motion. There is no sensation of motion; therefore, the Earth is not moving. • We don’t fall off as the Earth speeds ahead. • The apparent positions of the stars do not change, i.e. we see no parallax. • The Earth is an important place and it is natural that it is at the center of the Universe. Ptolemy’s Own Defense • Ptolemy’s model can be criticized on the grounds that it is cumbersome and lacking in beauty and symmetry. • “Let no one, seeing the difficulty of our devices, find troublesome such hypotheses. For it is not proper to apply human things to divine things from such dissimilar examples.” • Translation: What seems complicated to humans may seem simple to the gods. Summary and a Look Ahead • The concept of Celestial Spheres allows us to predict the motion of the stars. • If we add epicycles and several other “fixes” it is possible to predict the motion of the planets. • Ptolemy’s geocentric model provided the most accurate predictions of celestial motion. It allowed people to navigate to distant parts. • The geocentric model is cumbersome and inelegant. The symmetry that so drove the ancient Greeks has been lost. Is there an alternate, simpler model, that can explain the observations?