9. A “Man in the Moon”?
(…No, I’ve never really seen it, looking up in the sky…)
10. Even the ejected pieces
(“tektites”) from old craters,
have their own new “craters”!
Many Lunar Craters = scars from
“Heavy Bombardment” period
in the early Solar System…!
Older surfaces More Heavily Cratered!
11. http://vimeo.com/15610496
But where does the Moon come from?
(Numerical Simulation)
(Video)
Our Moon was formed by a collision!
(…we think…)
Within the first ~50 Million Years (or so)
of the Solar System’s history,
a ~Mars-sized object hit the Earth…
12. How do we know that our Moon
was formed by a collision?
…just like good (bad?) pizza, our Moon is mostly crust!
Similar to Earth’s crust, that is.
• (Plus hints from its isotopic composition, fast angular momentum…)
13.
14. The Cycle of
Lunar Phases
(Depending upon
the positions of
the Sun, Moon, Earth,
and the Observer…)
Moon-Rise/Set times
for different phases:
15. Sidereal Month
(“by the Stars”)
vs.
Synodic Month
(“by the Phases”)
What exactly is a “Month”, anyway?
16. What is a “Blue Moon”?
The term blue moon originates in folklore.
One “lunation” (an average lunar cycle) is 29.53 days.
Therefore, 12.37 lunations occur in a solar year.
Different traditions place the “extra" blue full moon at diff. times:
• The Maine Farmers' Almanac – An extra full moon in a season.
One season was normally three full moons.
If a season had four full moons,
then the third full moon was called a blue moon.
• In calculating the dates for Lent and Easter, the Christian clergy identified a Lenten moon.
Historically, when the moons arrived too early, they called the early moon
a betrayer (belewe) moon, so the Lenten moon came at its expected time.
• Folklore named each full moon according to its time of year. A moon that came too early was
called a blue moon; the rest of the moons that year retained their customary seasonal names.
• The second full moon in one calendar month is sometimes called a blue moon.
This usage results from a misinterpretation, in the March 1946 issue of Sky and Telescope,
of the traditional definition of blue moon.
Blue moon of Dec. 31, 2009,
with partial lunar eclipse
30. Tidal “Friction” #2:
• “Tidal Braking” slows Earth’s daily rotation about its axis!
• Conservation of Angular Momentum…
Earth experiences Longer Days!
Causes Lunar orbit to spiral out, farther & farther
away from Earth! (No more Total Solar Eclipses!)
(…from the solid Earth bulging
~tens of cm each high tide…)
