Chapter 19-1:

Sun, Earth, and Moon

Sun

• Geocentric vs heliocentric view• Solar rising/setting governs biological

processes• Sun’s energy heats atmosphere,

determines weather patterns• Solar flares; magnetic field distortions• Other systems around other stars =>

other planets => other life forms?

Gravity• Every object

w/mass attracts every other w/mass– More mass =

more attraction– More distance =

MUCH less attraction

Gravity• Orbits

– Johannes Kepler (1600s) originally thought orbits were perfectly circular (“Spheres” of the heavens)

– Just slightly elliptical - agrees with observations

Our Moon

• Was thought perfectly smooth until the invention of the telescope– Another of Galileo’s heresies!

• Phases– Time to spin around once on its axis (one Moon

“day”) = Time to orbit Earth once• . . . We always see the same side

“Dark Side of the Moon”• Not really “dark”; explored extensively by Russian (then

Soviet) spacecraft in the 1960’s - 1970’s.

• Causes tides• Eclipses

– Solar– Lunar

Moon Legends

• Mythology• “Bad” Science• Blue Moon• Selene, Moon goddess (Greek)• Artemis, Moon goddess (Greek)• Diana, Moon goddess (Roman)

Selene

• In Greek mythology, Selene (Σελη ́νη, "moon") (Roman equivalent: Luna) was an ancient lunar goddess, daughter of Hyperion and Theia. She was eventually largely supplanted by Artemis.

• Though she was usually a daughter of Hyperion and Theia, Selene was occasionally described as a daughter of Zeus, or of Pallas in the Homeric Hymn to Hermes. where she is "bright Selene, daughter of the lord Pallas, Megamedes' son." Helios is more often her brother. She has a sister, Eos, goddess of the dawn.

• She loved a handsome shepherd (or, more rarely, a king or a hunter) named Endymion from Asia Minor. He was so beautiful that Selene asked Zeus to grant him eternal life so he would never leave her. Alternatively, Endymion made the decision to live forever in sleep.

• Either way, Zeus blessed him by putting him into an eternal sleep. Every night, Selene visited him where he was buried on Mt. Latmus near Milete, in Asia Minor. Selene and Endymion had fifty daughters including Naxos.

Galilean Satellites

Solar Eclipse

Lunar Eclipse

For next time:

• Read all of 19-1 if you haven’t already• Answer #1-10, p. 636