Launch Pad: Facts about the Moon

On Sunday, we returned from Launch Pad, the astronomy workshop for writers. Our minds are overflowing with facts and ideas. Our first post about Launch Pad dealt with how Earth experiences seasons. (Hint: It’s not the distance; it’s the angle.) Now, we’ll take a small step—in astronomical terms—and share five things we learned about the Moon.

The far side of the Moon is not the same as the dark side of the Moon.

converted PNM fileThe Moon always shows the same face to Earth; it is, as astronomers say, tidally locked to Earth. In other words, the Moon rotates on its axis at almost exactly the same rate as it orbits Earth—synchronous rotation—so we always see the same side. The side facing away is, of course, the far side of the Moon.

The dark side of the Moon, on the other hand, is the side that faces away from the Sun and doesn’t get sunlight. This side is always changing, as the Moon’s position in relation to the Sun changes. The Dark Side of the Moon is also a 1973 album by Pink Floyd, and Wikipedia is more accurate on the musical version of this term than on the astronomical version.

These terms matter to astronomers, and terms matter to writers too. It’s important to get language right, to not confuse our terms.

The Moon is gibbous when more than half (but not all of it) is bright; the Moon is crescent when it is, well, crescent shaped, as viewed from Earth.

First Photo of Earth from Moon (NASA)
First Photo of Earth from Moon (NASA)

The Moon phase cycle is 29.53 days. The Moon phases are created by the angular relationships among the Moon, Earth, and the Sun. The New Moon is the first phase; the Moon appears dark because, during this phase, the Moon is between Earth and Sun, so the Sun is shining on the far side of the Moon.

The Full Moon—like the one you saw on Monday night, if you looked up and didn’t have cloud cover—occurs halfway through the cycle, when the Moon is on the opposite side of Earth than the Sun. The so-called Super Moon, which looked great last month, occurs when the Full Moon is closest to Earth.

At the First Quarter and Third (or Last) Quarter, we see a half circle of Moon, or half of half of the Moon’s surface.

So, here’s the full list of Moon phases in order: New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Third Quarter, Waning Crescent, New Moon. But other cultures parse the phases with greater detail. Hawaiians, for whom fishing and navigation have been important, have a system designating thirty phases.

Writers can find the Moon phase for any date and place (by time zone) HERE.

Earth’s Moon isn’t the biggest natural satellite in our Solar System.

Photo of Launch Pad Participants Taken by Cassini from Other Side of Satrun (NASA)
Photo of Launch Pad Participants Taken by Cassini from Other Side of Satrun (NASA)

Earth is a terrestrial—or rocky—planet, not a gas planet, and we do have the biggest Moon among the terrestrial planets that also include Mercury, Venus, and Mars.

Four natural satellites in our Solar System are bigger than our natural satellite: Ganymede, Callisto, and Io, which orbit Jupiter, and Titan around Saturn. In fact, those four moons are bigger than the planet Mercury. Size alone does not make a planet.

That said, the Moon is the largest satellite in the Solar System relative to the planet it orbits. The Moon is  influenced by the Sun’s gravity as well as by Earth’s. As a result, the Moon is drifting slowly away from Earth, and its barycenter—the center of gravity for Earth and Moon as a system (one of many cool terms we discussed at Launch Pad)—is moving in such a way that some have argued that it might one day need to be classified as a planet. As writers, we wonder what the Moon’s new name might be. After all, we couldn’t call a planet Moon, could we?

Easter falls on the first Full Moon after the vernal equinox.

The date of some religious holidays shifts on the calendar because the date selection is tied to the phases of the Moon. The Jewish holiday Purim, for instance, begins on a Full Moon. Ramadan, which Muslims are celebrating right now, falls between Crescent Moons. And the Crescent Moon and a star appear on the national flags of several Muslim countries.

From Earth, you can’t see the American flag that Neil Armstrong and Buzz Aldrin planted on the Moon’s surface.

Shuttle with Earth and Moon (NASA)
Shuttle with Earth and Moon (NASA)

The flag is so small and the Moon is so bright that Earth-based telescopes can’t make it out. Think about whether you can see a speck of dust on a shining light bulb from across the room. However, the camera on NASA’s Lunar Reconnaissance Orbiter (LRO) has taken high-resolution images of the Apollo landing sites and, by extension, the lunar flags. Analysis of the landing sites showed that it’s likely that some of the six Apollo flags are still standing. Flag photography wasn’t the LRO’s mission, of course; its mission was to map the lunar surface. The images of the Apollo landing sites were just a bonus, and bonus discoveries and spinoffs are part and parcel for NASA.

For a different take on this subject, check out Facts about the Moon, a poetry collection by Dorianne Laux.


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