very hot just below the
surface of the Earth
since we had found volcanoes breathing fire.
Copernicus must be
wrong. Galileo with his
telescope threatened to
turn all this on its head
in two ways. One was
Venus: a clear proof
that the planets did
not go ‘round the Sun
was that Venus hardly changed its brightness, and if it went
around the Sun,
it would surely be much
brighter
when
it
was near
the Earth
a n d
fainter
when it
was far
away; and
a n y w a y,
it
would
have phases
like the Moon.
No-one had seen
anything like phases
with Venus, but Galileo
with
his
telescope
could see clear phases
with Venus, which also
explained the brightness. When Venus is
near, it is apparently
bigger, but only a small
part of it is illuminated.
When it is far away, it is
smaller and fainter, but
the whole disc is illumi-
nated. The size and the
phase cancelled each
other out and kept the
brightness of Venus
the same as it orbited
the Sun. For the orthodox Catholic view the
unvarying brightness
of Venus was proof that
it did not go ‘round the
Sun, and only when
Galileo could show the
phases of Venus to
everyone did these
ideas change.
Venus
31