74 The EconomistMarch 14th 2020
T
here are, wrote Freeman Dyson towards the end of his long
life, two different kinds of mathematicians. Some are birds,
who fly high, surveying the broad vistas and spotting unexpected
links between different bits of the mathematical landscape. Oth-
ers are frogs, who prefer to be up close and on the ground, delight-
ing in the details and the beauty of the flowers.
He counted himself among the frogs, and started there. At the
age of 24 he made a fundamental contribution to the study of Dio-
phantine equations, a branch of mathematics dating back to the
ancient Greeks. A year later he resolved a tricky conundrum in
quantum electrodynamics, a field so new that it had hardly existed
when he was born. But already the airborne tendencies were stir-
ring. He was fascinated by biology, engineering, international re-
lations and, in particular, physics, at which he became a master.
For him, it was an ideal subject. Its mathematical underpinnings
might be abstruse and theoretical, but in the 20th century those
theories handed blunt, world-changing power to nations that
could master their applications. In the second world war, he ap-
plied his mathematics at Britain’s Bomber Command to calculate
the most destructive (but safe) formations for the planes to fly in.
After the war, when he moved to the Institute for Advanced Study
in Princeton, he rubbed shoulders with both Albert Einstein,
whose theorising on relativity he had revered since boyhood, and
Robert Oppenheimer, who had developed the atomic bomb.
Despite a lack of credentials (he never got round to earning his
phd; friends joked that he was the world’s most accomplished
graduate student), he was plainly clever. By the age of five, growing
up in Berkshire, he had tried to calculate how many atoms there
were in the sun. His leisure reading as a teenager was Piaggio’s“Differential Equations”; and he had solved that quantum electro-
dynamics puzzle, without pen or paper, while riding in a Grey-
hound bus. His very cleverness, his vivid language and his faith in
the potential of science—which marked him as it marked the cen-
tury—meant that, even when his schemes were wildly bizarre,
they were not dismissed. Colleagues respected him too much.
And the schemes came thick and fast. He proposed using ge-
netically altered trees to turn comets into places where humans
could resume an “arboreal existence”; these trees would grow hun-
dreds of miles high, until the comet would look like a sprouting
potato. He also popularised a wild thought called the Dyson
sphere, a gigantic shell made of pulverised asteroids that might be
spread by a very advanced civilisation round its parent star to cap-
ture all its energy. (Looking for such structures and their infra-red
glow elsewhere in the galaxy, he argued, might be a good way to de-
tect super-advanced aliens.) He imagined plants that could grow
greenhouses round themselves, and genetically altered microbes
that could harvest minerals and clear up plastic litter from space.
In 1958 he was briefly lured away from his professorship at the
iasto work on Project Orion: a plan to build a rocket, propelled by
nuclear power, that would be faster and more efficient than any
other. The basic principle was to throw a stream of nuclear bombs
out of the back of the rocket, detonate them, and ride the shock
waves to Mars and beyond. On paper, it seemed to work. Flight tests
on small models, using conventional explosives, were encourag-
ing. Orion could reach Mars in weeks, where chemical rockets
would take six months or more. A more powerful version could
cross the vast void to Alpha Centauri, the nearest star to the sun, in
a bit over a century. Since the bigger the rocket, the more efficient it
was, he proposed a 240m-ton ship 90 miles in diameter, designed
to carry thousands of colonists and make humanity an interstellar
species. Whether he was serious, even he may not have known.
The project was scuppered in the end by a mix of political quea-
siness over the fallout (rather literally—later modelling suggested
that each launch of a modestly-sized rocket from Earth’s surface
would kill about ten people) and the partial test ban treaty of 1963,
which forbade nuclear explosions except underground. He was in-
volved in that too, arguing in favour of the ban, in his clipped
home-counties tones, in front of America’s Senate. Since the pow-
er they had unleashed thrust physicists into high places, he also
became a government adviser on science and grand strategy. He
was on the board of sponsors of the Bulletin of the Atomic Scien-
tists, maintainers of the nuclear Doomsday Clock, which now
stands at 100 seconds to midnight. There was far more to nuclear
weapons, he knew, than the science that had spawned them. He
wrestled with the moral questions they raised, studying game the-
ory in an effort to work out when, if ever, it might make sense to use
such a weapon in anger. The problem of nuclear war, it seemed to
him, was fundamentally not technical but human and historical.
He was an iconoclast, too, and enjoyed being known as one.
Heretics were useful in science. It was far better to be contradicted
than ignored; better to be wrong than vague. As a colleague said,
whenever consensus was forming like ice hardening on a lake, he
would do his best to chip away at it. He dared to challenge natural
selection as the only driver of evolution, and he queried climate
change: not the fact that it was happening, but the usefulness of
the models that aimed to predict its effects. In any case, some of
those effects might be beneficial—a longer growing season, for ex-
ample, and fewer deaths from the cold. Environmentalism struck
him as more a religion than a science.
Not that he was against religion; he supported it, in a diffident
Church of England way. To get back beyond the Big Bang, certainly,
you needed religion. But the real faith that sustained him was a
boundless belief in the power and possibilities of science. He had
witnessed at first hand how it could give mere mortals the power to
destroy their own world. Perhaps they could use science to save it,
too—or, if not, leave it for another altogether. 7Freeman Dyson, physicist and big thinker, died on February
28th, aged 96Infinite possibilities
Obituary Freeman Dyson