AST101H5 Lecture Notes - Lecture 4: Apsis
Document Summary
What would cause no season on earth: no tilt. We can track the moon in the sky using the background star patterns = constellations. The moon returns to the same constellation of stars after 27. 321 days= the (cid:373)oo(cid:374)"s orbit period. (cid:374)ote: the (cid:373)oo(cid:374)"s (cid:272)ha(cid:374)gi(cid:374)g a(cid:374)gular size tells us that the (cid:373)oo(cid:374)"s or(cid:271)its arou(cid:374)d earth is. Phases are also caused by the moo(cid:374)"s or(cid:271)it arou(cid:374)d earth. The moon does not emit light of its own, it only reflects sunlight. The moon has a day side facing away from the sun. As the (cid:373)oo(cid:374) or(cid:271)its earth, (cid:449)e see differe(cid:374)t a(cid:373)ou(cid:374)ts of the (cid:373)oo(cid:374)"s day a(cid:374)d (cid:374)ight sides. Phases depend on 3 objects: earth, moon and the sun that provides the light. As the moon orbits earth, earth is also orbiting around the sun. Because earth has moved, the moon need about 2 more days to return to the same phase = relative alignment of the moon, earth and sun.
