Taking on the weight of the world

19th August 2005 at 01:00
Douglas Blane joins pupils to find out how scientific discoveries really happen.

The rock-strewn summit of Schiehallion, in Perthshire, is no place to linger unprotected, even on midsummer's day. A gentle breeze at ground level puts on a lot of force by the time it reaches the top of "the fairy hill of the Caledonians" (as the name translates).

So, the flapping blue tent tied to the rocks is vital for protecting the equipment and students brought up to "weigh the world".

The event is a re-enactment of a celebrated experiment first performed by the Reverend Nevil Maskelyne, the astronomer royal, who spent months on the mountain in 1774 making precise measurements of the stars. These established the Earth's mass, confirmed Newton's law of gravitation, and disproved, Maskelyne reported, "the hypothesis of some naturalists who suppose the Earth to be only a great hollow shell of matter".

The sixth-year pupils from Fortrose Academy in Highland and Crieff High in Perth and Kinross take turns in the tent, guided by scientists from Counting Thoughts, a Glasgow-based consultancy that develops teaching computer software.

"We all have astronomy backgrounds," says Dr Andrew Conway, "so our first idea was to repeat Maskelyne's experiment exactly." But it soon became apparent that this would be too much of a challenge. Even in the 21st century, measuring the apparent change in position of stars caused by the tiny shift due to the gravitational pull of a mountain would be painstaking work. It would also need to be done at night.

"We devised an alternative, not available to Maskelyne, because lasers and light-gates hadn't been invented," says Dr Conway. "Using these we measure the period of a pendulum to high accuracy. From that we calculate the acceleration due to gravity and hence the mass of the Earth."

Inside the tent, Crieff High students Kirsten Mauchline and Jennifer Scott are trying to do exactly that, but the laptop connected to the glass-encased apparatus is misbehaving.

"That should work now, if you'd like to try again," says Dr Aidan Keane, of Counting Thoughts. He has been in the tent since early morning collecting data, and getting more than a little cramp.

Crieff High physics teacher Rachel Gallagher says encountering problems and seeing that they can be solved are valuable parts of the experience for her students. "School science can seem very cut and dried because we teachers try to make sure everything works perfectly. Outside the classroom, science isn't like that."

"It is satisfying taking part in a real experiment," Kirsten says. "Also, getting outdoors is great."

While this also appeals to Nick Forwood, the principal teacher of physics at Fortrose Academy and a mountaineer, he is equally interested in the history of science. "I've been telling my pupils all about Maskelyne weighing the Earth and how this was used to calculate the mass of every other planet, once observations of the transit of Venus, carried out by Captain Cook's expedition (to New Zealand in 1769), gave them the scale of the solar system.

"I also tell them that my ancestor Stephen Forwood was the gunner on the Endeavour and Captain Cook said he had never put to sea with a worse sailor."

Demonstrating the human side of science was one of the main aims of the event, says Dr Peter Clive of Counting Thoughts. "We wanted to show that science is accessible, that you don't have to be part of an elite group to do it."

As clouds roll in to wreathe the 1083m summit of one of the highest mountains in Britain, "accessible" is not the first word that springs to mind.

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