Thursday 7 August 2014

Little Gnome Astronomical fact #3

WW1 Battlefields and Lunar Craters

At the beginning of the 20th century astronomers were still arguing over what caused the craters on the Moon. Some thought they were caused by volcanoes erupting soon after the formation of the Moon, while others thought that most were caused by meteorites crashing onto the surface of the Moon.

It was the First World War which actually gave the answer. New Zealand astronomer Algernon Charles Gifford (1861-1948) realised that  large explosive shells fired by guns and the huge mines triggered before battles left craters in the ground similar to those found on the Moon.

Algernon Charles Gifford

The huge crater at Lochnagar in northern France at the Battle of the Somme was caused by the ignition of 24 tons of explosive which caused a crater 300 feet deep and 70 feet wide. It was the largest man made crater produced during WW1 though a mere pinprick compared to lunar standards.

Lochnagar Crater

Compared this to Meteor Crater in Arizona which was made about 50,000 years ago by a meteor about 150 feet across, it made a hole 1 mile wide and 570 feet deep. The meteor hit the Earth with an explosive energy equal to 2.5 million tons of explosive. 

Meteor Crater

Gifford realised that if you compare the results of a meteorite striking the surface of the Moon or indeed any rocky planet and a massive explosion on Earth the end result would be in the same form, a circular crater. These craters could be seen during the horrendous battles fought on the western front.

Craters on the Moon

Today we know that Gifford was right, in the 1950s scientists examined the craters caused by the testing of atomic bombs.These were also circular in shape.

The craters seen in WW1, meteorite crater in Arizona and craters on the Moon were caused by impacts.

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