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Characteristics of our Moon

by Ron Kurtus (revised 18 December 2005)

A moon is a large body or mass or material that orbits around a planet. It is usually much smaller than the planet. The Earth has only one moon, while Mars has two moons and Jupiter has 9 moons.

Our Moon is only about 1/4 the diameter of the Earth. Its gravity affects the Earth's tides. The Moon looks bright at night because of sunlight that is reflected off its surface. It has some distinct surface features that can be seen with the naked eye. Astronauts examined the surface more closely during Moon landings.

Questions you may have include:

This lesson will answer those questions.

Physical characteristics

Characteristics of the Moon include its distance from the Earth, size, mass, density, and temperature.

Our Moon

Our Moon


The Moon is approximately 384,400 km (239,000 miles) from the Earth.

A radio signal from the Earth and bounced off the Moon's surface back to Earth would take approximately 2 seconds. Communication with an astronaut on the Moon would thus have a several second pause between a question and an answer.


The diameter of the Moon is 3479 kilometers (2162 miles). This is about 1/4 the diameter of the Earth (12,756 kilometers or 7,926 miles).


The mass of the Moon is 7.35*1022 kilograms, which is about 1/80 of the mass of the Earth. (1022 is 10 times itself 21 times or 1 followed by 22 zeros.)


The density of the Moon is 3340 kg/m3.

Density problem

Can you verify the density of the Moon?

Density = mass divided by volume, d = m/V.

The volume of a sphere = 4/3 times pi times its radius cubed,
V = 4*π*r3/3.


The average temperature on the surface of the Moon during the day is 107°C. That is hot enough to boil water on the Earth. During the night, the average temperature drops to −153°C.


The Moon revolves around the Earth in an elliptical orbit every 27.3 days. The same side of the Moon always faces the Earth. Due to the angle of the Sun on the Moon, we see different portions of Moon illuminated. These are called the phases of the Moon.

(See Motion of the Moon and Phases of the Moon for more information.)


Because of its smaller size and mass, the gravity of the Moon is about 1/6 the gravity on the Earth. That means that a person who weighs 180 pounds on Earth would only weigh 30 pounds, if measured on the Moon. That is why when the astronauts were on the Moon, they were able to jump so high—even while wearing the heavy space suit.

Moon causes tides

The force of gravity from the Moon affects the Earth. Its gravity reaches the Earth and pulls the oceans toward the Moon, causing the tides. The gravity from the Sun also affects the tides. The highest tides will always occur when the Moon and Sun are aligned. That is when there is a New Moon or a Full Moon.

Moon influences lunatics

There are even people who seem to be affected by the gravity of the moon. They are called "lunatics" from the Latin word luna, meaning moon. There are stories about people who are so affected by the moon that they turn into werewolves. Of course, that is fiction (I think).

Major features

The Moon shines at night, due to sunlight that is reflected off its surface.


The major features we can see on the Moon are its craters. These have apparently been caused by the impact from meteors over millions of years. Exploding volcanoes on the Moon also caused some craters.

Craters on Moon

You can see the craters on the Moon's surface

You can see the outlines of major craters on the Moon with your naked eye. The configuration almost looks like a face. Thus, they call it "the man in the Moon."

Moon landings

Much information about the surface of the Moon came from experiments United States astronauts made when they landed on the Moon in 1969. The United States landed men on the Moon six times between 1969 and 1972. Since then, no one else has landed on the Moon.


Our Moon is only about 1/4 the diameter of the Earth, has less gravity and has craters on its surface that can be seen with the naked eye. The Moon looks bright at night because of sunlight that is reflected off its surface. American astronauts landed on the Moon between 1969 and 1972.

Shoot for the Moon with your goals and plans

Resources and references

Ron Kurtus' Credentials


Facts About the Moon - From NASA

The Moon - Good details from Nine Planets site

The Moon - Information and statistics from Russian version of American website

Astronomy Resources


From Blue Moons To Black Holes: A Basic Guide To Astronomy, Outer Space, And Space Exploration by Melanie Melton Knocke; Prometheus Books (2005) $19.00

Observing the Moon by Peter T. Wlasuk; Springer (2000) $39.95 - Reference book for anyone seriously interested in the Moon and its geology

Welcome to the Moon: Twelve Lunar Expeditions for Small Telescopes by Robert Bruce Kelsey; Naturegraph Publishers (1997) $11.95 - Well written "how to" for novice astronomers

Top-rated books on the Moon

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