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Parallax: The race to measure the cosmos by Alan W. Hirshfeld, W. H. Freeman,
$23.95, ISBN 0716737116

BECAUSE the Earth goes around the Sun, nearby stars appear to move against
the background stars as we move from one side of our orbit to the other.
Copernicus knew this in 1543 and so did Galileo in 1690. Robert Hooke knew in
1670, James Bradley in 1727 and William Herschel in 1780. Measure the parallax
of a star, and you can work out how many times further away than the Sun it
is.

But search as these famous astronomers might, they could not detect this
annual “parallax shift”. Its tiny size defeated them. After the Sun, the next
nearest star to Earth is more than two-hundred thousand times further away. Its
parallax is less than a twentieth of one per cent of the size of the full Moon
in the sky. In the end, detecting parallax came down to excellence in lens
making and precision technology, coupled with the skill, application and
dedication of the German astronomer Friedrich Bessel, who got a result in
1838.

Parallax is a superb book. Hirshfeld, a Massachusetts professor of
astronomy, is hugely talented at bringing to life the story’s cast of
complicated characters. And he portrays science in its true light, avoiding the
misleading idea that it is a steady forward march to enlightenment. We get to
see it as a true human endeavour, complete with false assumptions, failures,
unfounded optimism, inattention to detail, luck, jealousies and egotisms. This
deserves to be a bestseller.