From delancyplace.com:

In today's excerpt - Edwin Hubble, the man
for whom today's Hubble Space Telescope is
named, discovers the universe:



"On an October night in 1923, at the Mount
Wilson Observatory north of Los Angeles, the
view of the night sky was unparalleled. Down
in the valley, Hollywood was booming, but the
population of the city was till less than a
million, and the tide of smog and city lights
had not yet crept up the mountain. On its
5,700-foot peak stood the largest telescope
in the world, a reflecting telescope with a
100-inch-wide mirror. At the eyepiece that
night, guiding the mammoth white tube as it
tracked the Andromeda Nebula across the sky,
sat a 33-year-old
astronomer named Edwin Hubble. He was about
to redefine our concept
of the universe. ...



"The telescope was the second
American thing about this
story. It's not just that it was the
world's largest, and thus the
instrument that could see the farthest
into what Hubble would later call 'the
realm of the nebulae' - it's that it was
paid for, not by the government, but by
wealthy philanthropists. John D.
Hooker, a local businessman, footed the
bill for the mirror, which was cast in
France from greenish wine-bottle glass
and then shipped to Pasadena for grinding and
polishing. The rest of the money came from
Andrew Carnegie, who through his Carnegie
Institution supported science by supporting
'exceptional' individuals like himself. The
brains behind the telescope, George
Hale, fit that bill, and so did Hubble,
whom Hale recruited. ...

"Astronomers at that time could not
decide, even roughly, how big the universe
was, let alone whether it was
expanding. There were basically two
camps. According to one, the universe
was no bigger than our own galaxy, the
Milky Way. The sun, like most stars we
can see, is embedded in that flat disk of
stars, which appears as a band of light
bisecting the night sky. But above and
below the disk float the nebulae: faint
clouds of light that, according to the
first camp, were just that - clouds of
luminous gas, studded perhaps with a
few stars. They were part of our galaxy
too; nothing we could see was not. It
was anywhere from 20,000 to 200,000
light years across, depending on which
astronomer you talked to.



"According to the other camp, however, those
nebulae were not intrinsically
faint and wispy - they only looked faint
because they were very far away. They
were other galaxies just like our own,
floating in a much bigger sea of empty
space. 'Island universes,' Immanuel
Kant had called them when he first proposed
the theory in the 18th century. ...
Hubble had devoted his doctoral work at
Chicago to observing nebulae with a
24-inch reflecting telescope; that's what
brought him to the attention of Hale. ...



"On the night of Oct. 5, 1923,
Hubble noticed a faint star [in the Andromeda
Nebula] he had not
seen before. Back in his office in
Pasadena, though, he found the same
star on earlier plates - it was a regularly
pulsing star called a Cepheid
variable. Astronomers had studied
Cepheids in the Milky Way, and discovered
that the period of the pulsations
was a reliable measure of the star's
intrinsic brightness. Comparing that
with how bright the star appeared on
their photographs, they could calculate
how far away it was. Hubble did that
right away with his first Cepheid. He
found that it and, thus, the Andromeda
Nebula were one million light-years
away - a distance five times greater than the
largest estimate of the Milky Way's
diameter. Clearly Andromeda was not
part of the Milky Way....



"When
Hubble's first results were presented at
a scientific meeting at the end of 1924,
one astronomer pulled out a slide rule to
calculate how much the volume of the
universe had just grown: a hundred-fold, he
said. When Harlow Shapley,
the leader of the
our-galaxy-is-the-whole-shebang camp,
received a letter
from Hubble in 1924, announcing the
Cepheids in Andromeda and another
nebula, he is reported to have said to a
colleague, 'Here is the letter that has
destroyed my universe.' "



Robert Kunzig, "America's Cosmic
Frontiersman," American History, August 2009,
pp. 59-62.