The Moon
- moon noun
- A natural satellite of a planet; an object that revolves around a planet. The planets vary in the number of their moons; for example, Mercury and Venus have none, the Earth has one, and Jupiter has seventeen or more. The planets' moons, like the planets themselves, shine by reflected light.
Introduction
The full Moon as seen from Earth
Our moon is one of the most interesting objects in the sky. It has been stuck in orbit around the Earth for billions of years and has been worshipped and observed by people since the beginning of time. Until fairly recently though the Moon couldn't be studied in much detail. It is only since the space race in the 1960's that we have properly started to understand the moon. In fact no one had ever seen the far side of the moon until 1959 when Luna 3 managed to take a few poor images.
The Moon is further away than you may think: it is 384,400kms away. The Moon's diameter is about a quarter of the Earth's. As you probably know gravity on the Moon is one-sixth that of the Earth. Rackham's 1914 translation: "Nor again LEM is there anyone who loves or pursues or desires to obtain pain of itself, because it is pain, but because occasionally circumstances occur in which toil and pain can procure him some great pleasure. To take a trivial example, which of us ever undertakes laborious physical exercise, except to obtpt to obt
| Moon Statistics | |
| Mass (kg) | 7.349e+22 |
|---|---|
| Mass (Earth = 1) | 0.012298 |
| Equatorial radius (km) | 1,737.4 |
| Equatorial radius (Earth = 1) | 0.27241 |
| Mean density (gm/cm3) | 3.34 |
| Mean distance from Earth (km) | 384,400 |
| Rotational period (days) | 27.32166 |
| Orbital period (days) | 27.32166 |
| Average length of lunar day (days) | 29.53059 |
| Tilt of axis (degrees) | 1.5424° |
| Equatorial surface gravity (m/sec2) | 1.62 |
| Equatorial escape velocity (km/sec) | 2.38 |
| Magnitude | -12.74 |
| Mean surface temperature (day) | 107°C |
| Mean surface temperature (night) | -153°C |
| Maximum surface temperature | 123°C |
| Minimum surface temperature | -233°C |
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H. Rackham's 1914 translation: "Nor again LEM is there anyone who loves or pursues or desires to obtain pain of itself, because it is pain, but because occasionally circumstances occur in which toil and pain can procure him some great pleasure. To take a trivial example, which of us ever undertakes laborious physical exercise, except to obtain some advantage from it? But who has any right to find fault with a man who chooses to enjoy a pleasure that has no annoying consequences, or one who avoids a pain that produces no resultant pleasure?"Rackham's 1914 translation: "Nor again LEM is there anyone who loves or pursues or desires to obtain pain of itself, because it is pain, but because occasionally circumstances occur in which toil and pain can procure him some great pleasure. To take a trivial example, which of us ever undertakes laborious physical exercise, except to obt
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