Man has long wondered where the moon came from. The accepted theory now is that the moon formed from material thrown out after a Mars-size object impacted the earth.
The earth and moon have things in common. They have the same minerals. That the moon is made of material similar to the earth's mantle suggests that it formed from stuff that was ejected. The impactor sunk into the young earth and merged with it.
There are differences! Earth is a water planet. The only water on the moon may be ice at its poles. The earth has an iron core. The moon has no iron and therefore no magnetic field.
The earth and moon affect each other. The earth has a greater gravitational effect on the moon because of its mass. Earth slowed the moon's spin so that the same side faces us. The moon rotates once in its orbit. The earth had a huge tidal effect on the moon's near side, thinning its crust so that lava flowed to create the maria.
It is easier to understand the tides if you live near the ocean. We see illustrations with water bulging toward the moon. A second bulge appears on the opposite side of the earth because the earth is being pulled away from the water. The bulges follow the moon's cycle. The moon is slowly leaving us. A billion years from now, there will be no total solar eclipses.
Living in the heart of Nashville, I cannot see the stars. I am aware of the moon, however. I watch it from my balcony as it crosses the night sky from east to west. This is an illusion caused by the earth spinning from west to east.
The moon orbits from west to east as it goes through its monthly cycle. As it orbits, its appearance changes. We call these changes, "phases." There are 8 of them. A new moon becomes a full moon after 2 weeks.
Phases are the result of angles formed by the moon, earth & sun. When the 3 line up with the moon in the middle, there is a new moon. We do not see the moon at this time because its night side faces us. When they line up with the earth in the middle, there is a full moon.
First quarter and last quarter occur when the 3 are at right angles. At first quarter, the right side of the moon is lit. At last quarter, the left side is lit.
Phases can be confusing until we visualize them. A waxing crescent follows a new moon. A waning crescent precedes a new moon. When a new moon covers the sun, there is a solar eclipse. When the earth covers a full moon, there is a lunar eclipse.
"Gibbous" is a strange word. The only time I see it is in relation to a waxing or a waning moon. It means lopsided.
Both the moon and the earth reflect sunlight. Standing on the moon, we would see the stationary earth go through phases. The earth is not seen from the moon's far side.
The sky on the moon is dark because there is no atmosphere. There is no sound because sound waves travel through air.
1 Aristarchus - Named after the Greek astronomer, Aristarchus of Samos, it is the brightest crater on the moon. It has a central peak and a wall covered with ejected material spreading into rays.
2 Copernicus - This impact crater in the Ocean of Storms has a ray system and a circular rim. Apollo 12 landed nearby.
3 Kepler - Named after the astronomer Johannes Kepler.
4 Grimaldi - Named after the Italian physicist, Francesco Grimaldi, this crater sits near the moon's western limb.
5 Eratosthenes - Named for the ancient Greek who estimated the Earth's circumference. There is a well-defined rim and a central peak.
6 Plato - Plato stands out with its dark floor and circular rim. Transient lunar phenomena have been seen, colors and flashes of light.
7 Tycho - Named after Danish astronomer Tycho Brahe, this crater in the southern highlands is young at 108 million years. Its ray system is stunning!
APOLLO LANDING SITES
Apollo 11 (Sea of Tranquillity) - Apollo 11 landed here, July 20, 1969. Neil Armstrong told Houston, "The Eagle has landed." Early astronomers thought the lava plains were water and called them seas. Riccioli's nomenclature is still used.
Apollo 12 (Ocean of Storms) - The only ocean on the moon because of its size: 1600 miles across. Alan Bean was on board Apollo 12.
Apollo 13 returned to earth when an oxygen tank blew up. Jim Lovell was the commander. It was 1970, and I was on my way to Germany.
Apollo 14 (Fra-Mauro Formation) - This crater was to be Apollo 13's landing site.
Apollo 15 (Hadley Rille) - A rille is a valley created by lava.
Apollo 16 (Descartes Highlands) - Descartes Crater is in the highlands, an area covered with sharp-rimmed craters.
Apollo 17 (Taurus-Littrow) - The crew named this site in the Taurus mountains.