So we’re in the basement of the Royal Society in London. This is the UK
Academy of Sciences. They have exhibitions here telling people about
interesting things about science, and so we have come here because
there’s a really interesting exhibit relevant to the work of Lawrence who
was the person after whom the element Lawrencium was named after.
Lawrencium is another one of the elements right at the bottom of the
periodic table which are really heavy, very radioactive. They fall to
pieces very rapidly. So chemists are very, and physicists are very lucky
if they just make a few atoms of this. So there’s nothing to tell you
about the uses of lawrencium, because nobody’s made enough
lawrencium to use it for anything, except as the subject of scientific
papers and physical measurements. So instead I want to show you here
a piece of equipment which is very similar to the sort of equipment that
Lawrence used when he was doing his pioneering work in Berkeley,
California, close to San Francisco. So let’s go along here.
Lawrence was famous for inventing an instrument called the Cyclotron
which was for accelerating electrons to very high speeds. It was in fact
the precursor of the large Hadron Collider which everybody’s now talking
about. But he thought of it I think one day in the library in Berkeley, and
he imagined to begin with an instrument that was literally as big as my
two hands here, a few inches across, and his idea was that if you made
a vessel which was quite flat and circular not very high and put in it a big
magnetic field the electrons could go round and round and round, and be
accelerated to go faster and faster. The idea was that he made one and
demonstrated the principle and he patented it and then he built bigger
and bigger and bigger machines and as he made them, not only did the
disc get bigger, but at the same time the magnet got bigger as well. And
the final magnet that he made in Berkeley, which was installed just
before the Second World War, was so large that a large part of his
research group could sit between the poles of the magnet and it’s so
heavy that the magnet is still there to this day. But come and look over
here. This is a Cyclotron that was built in Cambridge. The first thing that
strikes you is that it doesn’t look very exciting. It’s two copper discs,
which are not actually connected together and the voltage is switched
between one disc and the other so as the electron goes round when it
gets to the end of one you switch the voltage so it goes on being
accelerated and it goes round and round, and as it goes round in a
magnetic field the faster it goes the bigger the circle. So it goes round
and round and round in a larger and larger circle until the end it flies out
of one of these tubes. I think again that it is important to say that some
of these historic physics experiments, which are so important to both
chemistry and physics, were done with equipment that really looks
surprisingly simple and it is the really clever ideas that have been so
important to physics and chemistry rather than always having
enormously complicated apparatus. Sometimes to take these ideas to
their full extreme you do need complicated apparatus but that’s not the
starting point.
Well I’ve read quite a bit about him. He was meant to be a very
egotistical person and a real control freak, but my father-in-law worked
in Lawrence’s research group. When he was an English undergraduate he
was sent to America during the Second World War to work in Lawrence’s
group on the enrichment of uranium isotopes. That is, concentrating
Uranium-235, the less-common isotope which was the basis for the atom
bomb that was dropped on Hiroshima.
So John Keane, my father-in-law, worked in the research group, I don’t
know exactly what he did, but it’s really quite a sobering thought that
during the Second World War some of the brightest scientists had to
work on these terrible projects really in order to save their countries.
And let us hope that these such things never happen again.