Physics and Chemistry of the Highlands

Ben Nevis image001

     Many Scots have made major contributions to scientific discovery. What is less well known is the part that the Scottish landscape has played in this endeavour. There is, of course, the obvious connection in the word ‘Caledonian’, which is used by geologists to describe the mountain-forming movement that occurred during the Silurian era, about 395 million years ago. Indeed, visitors’ centres throughout theHighlands, whenever they touch on the scientific, tend to concentrate on the more accessible aspects of landscape, such as the geological and biological, whereas the physical sciences are generally ignored. Yet the land of Scotland has its importance in Physics and Chemistry, just as much as in the other disciplines. Three sites in particular, within a relatively short distance of each other, illustrate this.

Schiehallion

At the eastern edge of Rannoch Moor, visible from many distant viewpoints by virtue of its central position, is the cone-shaped peak of Schiehallion, which was the scene of an important experiment carried out in 1774.

When Isaac Newton proposed his theory of gravitation, in 1687, he expressed it in terms of a mathematical formula involving the masses of the objects attracting each other and their distance apart. Also included in the formula was a number of universal significance, which Newton called the gravitational constant. Unfortunately, the value of this constant was not known.

In 1772, the then Astronomer Royal, Nevil Maskelyne, suggested an experiment to determine the gravitational constant. This involved measuring the effect of a mountain on a heavy mass suspended from a string. According to Newton’s theory, the attraction of the mountain for this pendulum should pull it away from the vertical by a measurable amount. The mountain, however, had to be large enough and needed to be sufficiently far from other large masses so that their effects could be ignored. At 3547-feet in height, and standing in relative isolation, Schiehallion proved to be the ideal choice.

From June to October, 1774, Maskelyne and his team carried out a painstaking series of observations, which virtually mapped the entire mountain and, by analysis of the density of its rocks, estimated its mass. The true vertical was measured by observations of the stars at night, and the deviation of the pendulum from this was found to be a tiny fraction of a degree. Nevertheless, the gravitational constant was calculated and the average density of the earth was also found to be 4.5 times that of water.

In recognition of his dedication, Maskelyne was awarded the Copley Medal in 1775. One of the craters on the moon, near where the first manned spacecraft landed in 1969, is named after Maskelyne.

Ben Nevis.

The 20th century dominance of nuclear physics owes much of its development to Scotland’s most dominant mountain.

The summit plateau of Ben Nevis holds the ruins of the now redundant meteorological observatory. On a day of wind and horizontal rain, the walls offer a welcome measure of shelter after the long climb from the valley. Like any high mountain, Ben Nevis attracts, and even creates, its own weather systems and with them their associated phenomena. Wispy vapours seem to materialise out of nothing in clear air.

image003 View from the observatory, Ben Nevis summit

Intrigued by these phenomena, while working at the Ben Nevis Observatory in 1894, the young Scottish research physicist Charles Wilson decided to try to reproduce them in the Cavendish Laboratory inCambridge. He designed and built an apparatus which, when filled with water vapour then cooled rapidly by expansion of air inside, produced clouds. When in 1896 Wilson exposed his cloud chamber to the newly discovered X-rays, he found that these stimulated cloud formations so confirming his theory that the water droplets were forming around electrically charged air particles. Nowadays this phenomenon is commonly manifested in the vapour trails of high-flying aircraft.

With the discovery of radioactivity, the Wilson cloud chamber proved the ideal apparatus for making visible the tracks of radioactive particles in air, observation of which led subsequently to an understanding of the structure of the atomic nucleus.

For his pioneering inventiveness, Wilson, who was born in 1868 in Glencorse, Midlothian, was awarded the 1927 Nobel Prize for Physics.

Strontian.

About 20 miles south west of Ben Nevis, near the eastern extremity of Loch Sunart, stands the town of Strontian. Leading north from the town is the valley of the Strontian River around which lie the remains of a number of old lead mines. Among the minerals to be found here are rocks of a similar nature to limestone. For a time they were thought to consist of baryta, a mineral characterised by the Swedish chemist Scheele in 1774. In 1790, however, Adair Crawford showed these rocks to contain a second substance, which he called strontianite after the nearby town. With the development of electricity, Humphrey Davy was able to isolate, in 1808, a previously unknown metal from the strontianite, which he named strontium. It belongs to the same chemical ‘family’ as the metals magnesium and calcium, and shows similar properties.

The mineral strontianite is used in some metal producing furnaces to remove impurities. Like its calcium relative, limestone, it combines with these to produce a slag, which can be easily separated from the metal. When burned, strontium compounds impart a red colour to the flame so that they are often used for that purpose in fireworks.

The 92 chemical elements that occur naturally on earth take their individual names from a variety of sources. Some are named from their properties, others from mythology or in memory of famous scientists. A large number draw their names from countries or cities. The town of Strontian is unique in that it is the only place in the British Isles to have given its name to one of the chemical elements.

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