Moon

TIDAL TWINS

PROTECTIVE SHIELD 

The Moon has also influenced life on Earth at a biological level – scientists still can’t agree on whether the link between the lunar month and the female menstrual cycle is a coincidence, but there are certainly many simpler organisms, such as several species of insects and various marine plankton and corals, that have breeding rhythms tied to the Moon. For example, moths navigate by the Moon, and turtle hatchlings rely on the light of the Moon to help them find the sea and relative safety. 

One other significant role that our satellite may have played is in regulating conditions on our planet, and helping to keep them so ideal for life. The Moon is thought to act as a shield for the Earth – soaking up the impacts from many comets and asteroids (see Glossary) that might otherwise have threatened Earth, and deflecting countless other potential threats out of harm’s way. 

A few still get through to strike the Earth, of course, but by reducing the rate of major impacts to one every few million years, our lunar guardian helps give life a chance to develop. 

The Moon also helps to keep Earth itself stable our planet orbits the Sun like a spinning top, tilted over at 23.5 degrees relative to its orbit, and the Moon seems to stop this from varying by much more than a degree either way. In contrast, the tilt of Mars swings between extremes of 15 degrees and 35 degrees, creating an extremely variable and sometimes hostile environment.

 

 

 

FAR SIDE REVEALED 

The Moon’s far side is always hidden from Earth and only seen in images relayed by space craft.

  

INSIDE INFO

TIDAL TWINS

Just as the Moon influences Earth, so our planet affects the Moon. Earth has a much greater gravitational effect on its satellite than the other way around. The Moon, though, has no water to rise and fall in tides. Instead, the tidal effects are limited to the Moon’s rocks, which flex, compress and grind past each other during each monthly orbit. 

Early in its history, however, this relentless tugging began to slow down the Moon’s rotation, until eventually the point was reached where its orbital and rotation periods were the same. This keeps tidal forces to a minimum, so the Moon is now locked in this configuration.

As a result, the Moon keeps one face permanently towards Earth, with the other forever hidden from sight. This far or “dark” side of the Moon remained a mystery until Luna 3 sent back the first pictures in 1959.