Undreamed Shores - Ocean Worlds: The Story of Seas on Earth and Other Planets - page 249

men in the world' who then understood Einstein's revolutionary
and counter-intuitive ideas).
At Principe, Eddington was to provide crucial support for Einstein's
seemingly topsy-turvy theory. He noted that stars whose light was
passing close to our Sun appeared slightly out of position, indicating
that the mass of the Sun had bent the light from those stars on its
journey to Earth in accordance with Einstein's theory (we now know
that light can even be swallowed entirely, in the massive gravity well
of a black hole). This same microlensing effect can be used to detect
exoplanets, but it needs the light of two stars: that of the background
star is bent by the gravity of the intervening star, and if the interven-
ing star has an exoplanet with its own gravity, then that produces a
tiny but distinct and detectable change to the microlensing effect.
The Space Race
As the wobble, transit, and microlensing effects were used by ground-
based telescopes, with ever more careful and sensitive techniques the
number of suspected and confirmed exoplanets began to rise. But the
Earth's atmosphere, with its dust and clouds and the absorptive effect
of the gases within it, blocks or distorts much of the electromagnetic
signal that comes from outer space. In particular, this atmospheric
blurring made it virtually impossible to detect Earth-size planets that
have Earth-size orbits. One answer has been to go into the transpar-
ent near-vacuum of space.
The celebrated pioneer here is NASA's Hubble Space Telescope,
launched in 1990. Hubble made a famously inauspicious beginning. A
tiny flaw in its 2.4-metre light-collecting mirror meant that its initial
images were slightly blurred: they were better than images that could
be resolved on Earth, but not as good as the perfect images that were
expected. In a magnificent exercise in rescue engineering, NASA sent
a mission into space during December 1993 to fix the problem, fitting