The Moon

by Chris Lawton

Despite its proximity relatively little was known about our nearest neighbour until the coming of the space age. Due to the spin and orbital periods of the moon being virtually identical we always see the same face. Consequently it wasn't until the late 1950's that the first pictures of the far side of the moon were received from the Russian Luna 3 probe.

The moon has a diameter of 3 500 km, about the same as Australia. Its mass is an eightieth of ours and gravity one sixth. Essentially it is just a ball of rock in orbit around the earth. What makes it so attractive is its proximity. Far enough away to cause wonder yet close enough to be reachable. We can easily observe the moon and its phases. Because the moon orbits us we see the sunlight reflected off different amounts of its surface. When the moon is aligned between us and the sun we have a new moon - which is not visible. As the moon progresses in its orbit around the earth we see it move through crescent to gibbous to full moon. At this point the whole surface of the moon is illuminated. The moon then moves on back through gibbous to crescent to new.

Occasionally at a new moon the alignment is such that the moon passes directly between us and the sun. Due to variances in the orbit sometimes the relative sizes of sun and moon are such that the whole of the sun is obscured - this is a solar eclipse. In 1999 such an event will be viewable in the UK from Cornwall. If the moons apparent size is smaller than the sun an annular eclipse occurs. Neither of these events last for a particularly long time - at most 8 and 14 minutes respectively.

At a full moon the earth's shadow can pass across the lunar surface creating a lunar eclipse. These are much more frequent than solar eclipses and last for up to one and a half hours. In a lunar eclipse the moon often adopts a coppery red colour. This is due to sunlight being scattered form the earth's atmosphere.

Without the space race there would almost certainly have been no moon landings. Kennedy's famous speech in 1961 committed America to put a man on the moon before 1970. By the time that day arrived the political motivation was waning and by 1972 man left the moon for the last time. In the current political and financial climates it is unlikely that man will return for a number of years to come.

The Apollo mission was created with Kennedy's decree in mind. The Apollo 8 mission was a great publicity stunt - timed such that the lunar orbit took place over Christmas and within seven months Apollo 11 stood on the launch pad ready to take the first men to the moon.

On July 16 1969 the giant Saturn V rocket took off from Cape Kennedy with the aim of putting two men - Neil Armstrong and Edwin 'Buzz' Aldrin - on the lunar surface. The mission went almost to perfection and on July 20 1969 the lunar module Eagle landed in the Sea of Tranquillity. A few hours later Neil Armstrong stepped out from the lunar module and as he touched the surface spoke the following :

" That's one small step for a man. One giant leap for mankind."

The two pioneers spent some 2.5 hours on the surface of the moon collecting samples and experiencing the increased freedom of low gravity. When they blasted off from the surface they left behind a plaque :

" Here men from planet Earth first set foot on the Moon, July 1969, AD. We came in peace for all mankind. "

There were six other lunar missions including the fateful Apollo 13 mission. In all twelve men explored the lunar surface for a total of 166 hours. In this time they travelled some 100 km in a variety of vehicles including the lunar rovers. Nearly 400 kg of samples were returned and many experiments undertaken. 30 000 photographs were taken of the lunar environment and 20 000 geophysical data tapes collected. By the time Eugene Cernan and Harrison Schmitt left the surface in December 1972 the total cost of the Apollo project was $ 25 000 million.