AST 2002 Lecture Notes - Lecture 2: Top, The Moons, Ecliptic
Document Summary
Highest point of sun is summer solstice june 21st. Earth"s axis points in the same direction (to polaris) all year round, so its orientation relative to the sun changes as earth orbits the sun. Equinoxes: sun arises precisely due east and sets precisely west. Although the axis seems fixed on human time scales; processes over 26,000 years. Earth"s axis processes like the axis of spinning top. Synchronous rotation: the moon rotates exactly once each orbit. This is why we only see one side. Study moon cycles, and degrees of moon points in correlations to the sun. When either passes the other"s shadow, we have an eclipse. Lunar eclipses can be penumbral, partial, or total. Why (cid:449)e do(cid:374) t ha(cid:448)e a(cid:374) eclipse at e(cid:448)ery (cid:374)e(cid:449) a(cid:374)d full (cid:373)oo(cid:374): The moon"s orbit is tilted at 5 degree to the ecliptic plane. So we have about eclipse seasons each year, with a lunar eclipse at full moon.
