Title->     Sakharov's visions. (Andrei Sakharov) (Science and
            Technology)

HIS part in making Russia a military superpower, by providing it with
nuclear weapons, would have earned Andrei Sakharov a place in history.
So would his struggles as a dissident. Without either of those,
though, he would still rate a mention as one of the best theoretical
physicists of the past 40 years.

Sakharov was principally a nuclear physicist, but he worked on
astrophysical problems too. His first studies were on the cosmic
radiation that constantly bombards the earth. From that he went on to
attempt applied astrophysics: bringing the power of the stars down to
earth. As well as providing the Russian army with fusion weapons,
Sakharov and his colleagues also took the first steps towards
harnessing fusion as an energy source, using magnetic fields to
"bottle" the hot plasmas in which it takes place, and eventually
developing the doughnut-shaped tokamak magnetic bottle, still the most
promising technology for fusion today.

In  the  1950s  and the  1960s, Sakharov's work in physics brought him
fame, at least among Russian academicians. While his objections to
testing weapons led him into politics, he was doing some of his most
brilliant work. His most cited and admired paper, published in 1967,
addressed the puzzling fact that there is matter in the universe. Big
bang theories of creation, then becoming popular, suggest that matter
and antimatter should be created in equal amounts. Since matter and
antimatter destroy each other, how could anything survive creation?

Sakharov realised that there must be subtle flaws in the symmetry
between matter and antimatter. Even though almost all the matter and
antimatter did cancel each other out, producing the radiation which
saturates the universe, there was a little matter left over. It took
over ten years for physicists elsewhere to catch up with his ideas,
and provide theories that met his conditions of asymmetry.

Sakharov's later work concentrated on general relativity. Einstein's
theory deals with the shape of space and time, describing gravity as
the way in which objects distort geometry. Sakharov accepted the
theory's precision and elegance, but he believed it to be only a
description of the world, not an explanation of it. The properties of
a rubber band being stretched can be described perfectly well by
theories of elasticity, but the underlying explanation lies in the way
that the molecules making up the material interact. So Sakharov
believed that the properties of space and time described by Einstein,
including gravity, were secondary effects due to some more basic
phenomena. His ideas in this field have not gained much acceptance,
but they still might. Sometimes a theory's active life begins after
its progenitor's has ended.

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