Physics and Chemistry of the Highlands.
By Anthony Toole.
Ben Nevis
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 the Highlands, 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.
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 in Cambridge. 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.