NATS 1745 Lecture 2: Lecture 2b
22 Feb 2019
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Introduction: what can we really observe with the naked eye, roots of astronomy. Motions: earliest astronomy: study of how bodies around us moved, watching motions in the sky, why they are happening. A day is measured in how long it takes to return to the meridian: synodic: more easily observable. Time it takes earth to turn 360 degrees. Takes a bit less than a day: compare it to a distant things. Take more careful observations against background stars: mark of more sophisticated observers. Earth"s orbit: slightly elliptical, sun is off center, sun is sometimes farther and sometimes closer, farther: aphelion, closer: perihelion, full moon: moon is at perigee, observations can"t be made without telescope, no noticeable effects without it. When the sun returns to the vernal equinox (on the tropic line) Calendar: measuring against when the sun on the meridian passes across the tropic line (around march 21st, everyone has the same amount of daylight during the equinox.
