Thursday, December 2

How much the Earth weighs and how a humble Scottish mountain helped discover it

Scottish Highlands

Image source, Getty Images

In the summer of 1774, the British astronomer, Nevil Maskelyne, stood on the side of a Scottish mountain gazing at something deeper than sight. He was trying to find out how much the Earth weighed.

Schiehallion Mountain in Perthshire is what is often referred to as a “hump”. It goes from east to west, (its north and south slopes are very steep), with a complicated and steep west slope that marks the head of the mountain. And a much longer east slope that marks the tail, the path where most of the climbs are attempted.

When I had the first glimpse of the headland of Schiehallion, from the north shore of Loch Rannoch, I realized that it could pass like a volcano, because it was steep on the sides and tapered to a sharper point.

The necessary mountain

This was exactly the type of mountain that Maskelyne asked his fellow astronomer, Charles Mason, to look for in 1772, because it was just the right size to study.

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