Skylights Bite Size 22 - Our Moon

By ANDY FLEMING

A view of the Apollo 11 lunar module "Eagle" as it returned from the surface of the moon to dock with the command module "Columbia". A smooth mare area is visible on the Moon below and a half-illuminated Earth hangs over the horizon. The lunar module ascent stage was about 4 metres across. Command module pilot Michael Collins took this picture just before docking at 21:34:00 UT on 21 July 1969. (Credit: NASA)

This highly interesting podcast is about our own Moon, how it formed and how it's been an intrinsic part of the evolution of life on the Earth.

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Skylights Bite Size 22 - Our Moon
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Skylights is featured on Solid Gold Sunday each Sunday afternoon at 1425h UTC on 102.4FM in Hartlepool/East Durham, UK and live around the world online at www.radiohartlepool.co.uk
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Show Notes and Transcript

Our Moon is far more important to all life on Earth than most people realise.  Simply illuminating the night sky or being responsible for ocean tides is of relatively little significance when one realises its true effect on the Earth and us.  It has been intrinsic to the very evolution of life itself, and by definition the appearance of homo sapiens!  And it's not hard to see why it is so important.  To start with it is the only Moon of a major planet in the solar system that is so large relative to its parent planet, indeed many astronomers consider the Earth/Moon system to be a double or binary planetary system.  At 385,000 kilometres distant it is the closest celestial body to the Earth.

The Moon was created from the Earth itself, confirmed by the geological experiments undertaken during the NASA Apollo program.  Unlike the Earth, there is very little iron on its surface and it consists of terrestrial mantle material.  It was created by a Mars-sized impactor striking the young Earth about four billion years ago.  The Earth was nearly completely destroyed by the collision, and the ejecta from the Earth's mantle and the material from the impactor itself eventually came together to form the Moon.

At that point the Moon orbited the young Earth at only a fraction of its current distance, and would have looked enormous in the sky.  The Earth's day was about eight hours in duration, but over four billion years the friction of the lunar gravity has slowed this down to twenty four hours.  Eventually, the velocity of the Moon orbiting the Earth matched that of its rotational speed so that now the Moon is tidally locked to the Earth: the same side of the Moon is visible to the Earth at all times and until the unmanned Soviet and NASA probes of the early 1960s, no human being had ever seen the far side.  Notice it is called the 'far side' and not the 'dark side', a serious misnomer as it receives the same attention from the Sun as the Earth-facing side.

Most importantly, the Moon has prevented the Earth wobbling uncontrollably on its axis and hence over billions of years has provided the climatic stability essential for the evolution of complex life forms.

Precision experiments left on the lunar surface by the Apollo astronauts confirm that the Moon is receding from the Earth by a couple of centimetres per year.