Tales from the Man who would be King

Rex Jaeschke's Personal Blog

A Little Bit of Astronomy: The Moon

© 2016 Rex Jaeschke. All rights reserved.


A few years ago, after living in cities for more than 40 years, I moved out into the countryside. As a result, I rediscovered the night sky. So much so, that since then I even sit out on my deck in winter, wrapped in a blanket sipping hot chocolate or port wine gazing at the Heavens. Of course, the biggest and brightest object one can see is the Moon. After I watched a most interesting documentary video on the Moon, I was inspired to research the topic and to write this essay.

When we say the Moon, of course, we're talking about the natural satellite that goes around the Earth. As it happens there are other moons going around other planets, both in our solar system and in others. So, Earth's moon is but one of many moons. In general, a moon is a celestial body that orbits another body.

According to Wikipedia, in our solar system, "Of the inner planets, Mercury and Venus have no natural satellites; Earth has one large natural satellite, known as the Moon; and Mars has two tiny natural satellites, Phobos and Deimos. The large gas giants have extensive systems of natural satellites, including half a dozen comparable in size to Earth's Moon: the four Galilean moons, Saturn's Titan, and Neptune's Triton."

The Moon rotates synchronously with Earth. As such, we always see the same side, called the near side. The opposite side is—da da—the far side, sometimes incorrectly referred to as the dark side, although it receives sunlight each day. [A very popular music album is Pink Floyd's Dark Side of the Moon.]

The Moon's Makeup and Environment

So, just what is the moon made of? Why cheese, of course! Anyone who's seen the Wallace and Gromit movie A Grand Day Out knows that! Although the moon's makeup is not quite the same as Earth's, the prevailing theory is that the Moon was created from the debris left behind after a collision between Earth and Theia, a large ancient planet.

Even though the moon looks quite white, its surface soil is quite dark. The brightness comes from the sunlight reflected off the silicon compound in the soil.

The moon has no active volcanoes, no tectonic plates, no earthquakes, and no appreciable atmosphere. Regarding gravity, an object on the surface of the Moon has only 16.6% of its Earth weight.

Compared to the Earth, the moon has a weak magnetic field.

Earth's Poles, Tropics, Seasons, and Tides

The Earth rotates around its axis at a tilt between 22.1 and 24.5 degrees. This gives rise to the two polar circles, the two tropical lines, the equator, and the seasons. The gravitational interaction between the Earth and Moon prevents the Earth's axis from wobbling.

The gravitational influence of the Moon (along with the weaker gravitational influence of the Sun, and the Earth's rotation) is what causes the tides in our oceans. The oceans closest to the Moon experience high tides, as they are attracted to the Moon, while those on the opposite side of the Earth experience low tides. Some shorelines experience two high and two low tides per day, while others have only one of each.

The difference between a high and low tide over a 12-hour period is called the tidal range. This range is at its largest twice a month, during a new moon and a full moon, when we have spring tides. This range is at its smallest at the first quarter and third quarters of the Moon, when we have neap tides. [I grew up in the Australian state of South Australia, which has a unique term, dodge tide. This is a neap tide with very little rise and fall over a one- or two-day period.] The Bay of Fundy, located between the Canadian provinces of New Brunswick and Nova Scotia, has the largest tidal range on Earth, of up to 53.5 feet (16.3 meters).

The Moon's Phases

A phase of the Moon relates to the shape of the part of the Moon we can see from some given place on the Earth. As the Moon orbits the Earth, the phase changes.

In the West, we refer to four primary lunar phases: new moon, first quarter, full moon, and third quarter (or last quarter). These are interspersed with four intermediate phases: waxing crescent, waxing gibbous, waning gibbous, and waning crescent.

Throughout history, attempts have been made to correlate certain human and animal behaviors (including madness) with phases of the Moon. This field of study is called lunar effect. Note that the word lunacy is derived from the Latin word for moon, luna.

Craters and Seas

The surface of the Moon has numerous craters from impacts of asteroids, comets, and such. The largest crater has a diameter of 1,390 miles (2,240 km)—about half the size of the United States—and a depth of 8.1 miles (13 km). Click here for more information about these craters.

Although there is no water at the Moon's surface, early astronomers thought the Moon contained seas, and named them each a mar, which is Latin for sea. One of the best known is the Sea of Tranquility, the landing site of the first manned mission, Apollo 11. Click here for more information about these so-called seas.


An eclipse occurs when an object in space is hidden temporarily, either because it passes into the shadow of another body—as with a lunar eclipse when the Earth comes between the Sun and the Moon–or by having another object pass between it and the viewer—as with a solar eclipse when the Moon comes between the Sun and the Earth. Given the Moon's size and its proximity to the Earth, during a solar eclipse the Moon completely hides the Sun. [Dazzle your friends by using the word syzygy in a conversion.]

The ancients often thought of eclipses as omens. Click here and here for further information on this regarding lunar and solar eclipses, respectively.

Time and Lunar Calendars

The gravitation force between the Earth and Moon slows the Earth's rotation ever so slightly, which resulted in the introduction of the leap second to our time-keeping systems back in 1972. As necessary, to compensate for this slowdown, at midnight on the last day of June and/or December of each year, an extra second is added, resulting in that final minute having 61 seconds. So, some minutes are more equal than others!

A prominent theory of Earth's creation (No; not the 7-day one!) is that it was formed after another object struck it and spun off Earth debris to create the Moon. The impact started the Earth spinning on its own axis at a rate of about once every 24 hours.

When we use the term year, we're talking about a solar year, which is based on the time it takes for the Earth to revolve once around the Sun. Calendars based on this time are solar calendars, of which the Gregorian calendar used in many countries, is one example. A calendar based on the cycles of lunar phases is, not surprisingly, a lunar calendar. Some calendars use a combination of factors relating to both the Sun and the Moon. (See Chinese calendar, Hebrew calendar, Hindu calendar, Islamic calendar, and Thai calendar.)

The Moon's Orbit

The moon orbits the Earth approximately every 27.3 days, although many people approximate this to 28 days. This orbit path is elliptical in shape and the distance from the Earth and the nearest and farthest point of the Moon's orbit differs by about 26,000 miles (41,600 kms). At certain times, the Moon appears so close to the Earth that we call it a supermoon.

Apparently, the Moon is moving ever so slightly away from the Earth.

Miscellaneous Bits

So, who owns the Moon and, legally, what can they do with it? For more information see Outer Space Treaty and Moon Agreement.

The name of the day of the week Monday, comes from the Old English "day of the moon". (Equivalent Germanic-language words have an equivalent basis.) In French, that day is Lundi, luni in Romanian, and lunes in Spanish.

It takes light about 1.26 seconds to travel between the Moon and Earth (compared with about 8.33 minutes to travel between the Sun and the Earth).

Click here to see a list of the artificial objects on the Moon.

The International Red Cross is well known in most Western countries; however, give the word cross implies a Christian influence, a corresponding branch of this organization, the Red Crescent, was created. The crescent shape appears as one of the phases of the Moon, and as Islamic countries typically use a lunar calendar, the crescent appears on some of their national flags.

The idiomatic English phrase "once in a blue moon" means "a long time". Typically, a blue moon is the second full moon in a given month, and has nothing to do with the Moon's color.

By the way, have you ever mooned anyone, or been mooned? Try it sometime!


According to Wikipedia, 'There is a traditional belief that the Man in the Moon enjoyed drinking, especially claret. An old ballad goes (shown here with original spelling):

Our man in the moon drinks clarret,
With powder-beef, turnep, and carret.
If he doth so, why should not you
Drink until the sky looks blew?

In the English Middle Ages and renaissance, the moon was held to be the god of drunkards, and at least three London taverns were named "The Man in the Moone".'