Download The Evolution of Astronomy: From Ancient Times to Modern Science and more Study notes Physics in PDF only on Docsity! Modern astronomy: From Ancient Times to Today Lecture 6 PH 1040: Astronomy Shane L. Larson Weber State University 1 • Ancient astronomy (archaeoastronomy) • Birth of “Modern Astronomy” • Telescopes • Telescopes for all kinds of light Storyline 2 • There are other Anasazi solstice markers at Chaco Canyon which are obviously quite deliberate Chaco Sun Dagger (anasazi) 5 • Near Powell, Wyoming. 75 Foot in Diameter Big Horn Medicine Wheel 6 HORN MEDICINE WHEEL
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• Tycho Brahe was the last great naked eye astronomer. He observed at his castle Uraniborg using enormous devices for measuring angles and positions, and he kept time using the motion of the stars themselves Tycho, Last of the Ancients 10 • I: Planets travel on ellipses with the Sun at one focus • II: Planets sweep out equal areas in equal times • III: The square of a planet’s orbital period is proportional to the third power of its semi- major axis Laws of Planetary Motion 11 • 8 years after Tycho died, Galileo invented the first astronomical telescope (having heard of one built by the Danes), changing astronomy forever Revolution in Astronomy 12 • Newtonian gravity was the first great physical law deduced • Isaac Newton (1642-1726) • Lucasian Professor at Cambridge • 1687 — Principia published with Laws of Motion, Calculus, and Universal Gravitation • Invented the reflecting telescope in ~1670 Isaac Newton 15 • Strength of the gravitational force depends on the masses involved, and the distance separating them • This is an “inverse square law” Universal Law of Gravitation M m r 16 • Galielo’s telescope was a refractor (light is focused through a clear piece of glass) • Making accurate large pieces of clear glass is hard! • Newton built his reflecting telescope in 1670 (possibly after seeing Robert Hooke’s). Mirror making is easier than lensmaking! Newtonian reflector 17 Optical Telescopes Human Pupil (5mm) 32 cm Telescope (Equinox, Shane’s Telescope) 5 meter Telescope (Hale Telescope, Mt. Palomar) • Optical telescopes have light gathering power. They help see dim objects; magnification is usually variable. 20 Optical Telescopes • Increasing the size of a telescope does two things: • Can see dimmer objects • Better angular resolution (see smaller details) • L = size of object telescope can see (in meters) • R = distance to object (in meters) • λ = wavelength of light telescope can see (in meters) • D = diameter of telescope (in meters) 21 Hubble & the Moon • If Hubble looked at the Moon, what could it see? Small craters? Apollo landers? Astronaut footprints? • R = distance to Moon = 384,000 km = 3.84 x 108 m • λ = wavelength of light = 500 nm = 5.0 x 10–7 m • D = diameter of telescope = 2.4 m 22 Earthbound Telescopes Boomerang Parkes VLA Mauna Kea LBT Yerkes Bell Labs µWave Antenna 24 Space Telescopes HubbleChandra Compton Spitzer COBE WMAP 25 Non-Light Telescopes • Some telescopes don’t even look a the Cosmos with light; instead they use other exotic phenomena like neutrinos, cosmic rays, and gravitational waves Fly’s Eye 2 LIGO SNO SuperK Milagro Auger 26
