the Universe. Despite a suggestion first made by William
Herschel in the 18th century, he shared the accepted
view that all nebulae were relatively nearby objects and
merely patches of dust and gas in the sky.
The turning point
Hubble had to spend many bitterly cold nights sitting
at the powerful Hooker telescope before he could prove
Shapley wrong. In October 1923 he spotted what he first
thought was a nova star flaring up dramatically in the
M31 “nebula” in the constellation of Andromeda. After
careful examination of photographic plates of the same
area taken previously by other astronomers, including
Shapley, he realised that it was a Cepheid star. Hubble
used Shapley’s method to measure the distance to the
new Cepheid. He could then place M31 a million lightyears away - far outside the Milky Way and thus itself a
galaxy containing millions of stars. The known Universe
had expanded dramatically that day and – in a sense –
the Cosmos itself had been discovered!
Just the beginning
This discovery was of great importance to the astronomical world, but Hubble’s greatest moment was yet to
come. He began to classify all the known nebulae and to
measure their velocities from the spectra of their emitted
light. In 1929 he made another startling find – all galaxies seemed to be receding from us with velocities that
increased in proportion to their distance from us – a relationship now known as Hubble’s Law.
This discovery was a tremendous breakthrough for the
astronomy of that time as it overturned the conventional
view of a static Universe and showed that the Universe
itself was expanding. More than a decade earlier, Einstein himself had bowed to the observational wisdom of
the day and corrected his equations, which had originally predicted an expanding Universe. Now Hubble had
demonstrated that Einstein was right in the first place.
The now elderly, world-famous physicist went specially
to visit Hubble at Mount Wilson to express his gratitude.
He called the original change of his beloved equations
“the greatest blunder of my life.”
Another war stops Hubble again
Hubble worked on indefatigably at Mount Wilson until
the summer of 1942, when he left to serve in World War
II. He was awarded the Medal of Merit in 1946. Finally,
he went back to his Observatory. His last great contribution to astronomy was a central role in the design and
construction of the Hale 200-inch Telescope on Palomar
Mountain. Four times as powerful as the Hooker, the Hale
would be the largest telescope on Earth for decades. In
1949, he was honoured by being allowed the first use of
the telescope.
No Nobel Prize for an astronomer
During his life, Hubble had tried to obtain the Nobel
Prize, even hiring a publicity agent to promote his cause
The 100 inch (2.5 m) Hooker telescope at Mount Wilson Observatory near Los
Angeles, California. This is the telescope that Edwin Hubble used to measure galaxy
redshifts and discover the general expansion of the universe. Credit: Andrew Dunn
in the late 1940s, but all the effort was in vain as there was
no category for astronomy. Hubble died in 1953 while
preparing for several nights of observations, his last great
ambition unfulfilled.
He would have been thrilled had he known that the
Space Telescope is named after him, so that astronomers
can continue to “hope to find something we had not
expected”, as he said in 1948 during a BBC broadcast in
London.