Edwin Hubble announced existence of other galaxies - December 30, 1924

On this day in 1924, Edwin Hubble published his observations on the existence of other galaxies for review at an upcoming meeting of the American Astronomical Society. 

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Episode Transcript

Speaker 1 (00:00):
This Day in History Class is a production of I
Heart Radio. Hey everyone, if I sound a lot cozier today,
it's because I am. I'm at home for the holidays.
But this is this Day in History class, which means
you'll still get a new slice of history every day.
So let's get on with the show. Today is December.

(00:29):
The day was December n American astronomer Edwin Hubble announced
the existence of galaxies beyond the Milky Way. Hubble graduated
from the University of Chicago in nineteen ten with the
Bachelor of Science in Mathematics and astronomy, and in nineteen
fourteen he went back to the University of Chicago to

(00:49):
get his doctorate in astronomy. There he began working at
the Yerkes Observatory, where he studied nebulie or anything that
wasn't immediately identifiable as this are. He got his doctorate
in nineteen seventeen, but that same year the US entered
World War One, and Hubble joined the army. Once the

(01:10):
war ended, he returned to astronomy. Astronomer George Hale, founder
of the Yerkes Observatory and director of the Mount Wilson Observatory,
had offered Hubble a job at Mount Wilson before he
went off to war. In nineteen nineteen, Hubble took a
staff position at Mount Wilson Observatory near Pasadena, California. There

(01:31):
he worked with a one hooker telescope, which was then
the largest in the world. He stayed at the observatory
for his whole career. At Mount Wilson, Hubble continued studying nebulae.
At this time, scientists thought the Milky Way made up
the entire universe. In spiral nebulae were thought to be

(01:51):
clouds of gas or dust within the Milky Way, but
in nineteen twelve, astronomer Henrietta Levitt showed how to use sefid's,
or stars that brightened and dem periodically, to estimate their
distance from Earth, and some astronomers did believe that the
nebulae were distant island universes that were separate from the

(02:12):
Milky Way. Starting in nineteen twenty three, Hubble identified Sefid
variable stars and what was then known as the Andromeda nebula.
Based on their brightness, luminosity, and the distances of sefiad
stars in the Milky Way. Hubble determined that the stars
were at least eight hundred thousand light years away. That

(02:34):
meant that they were beyond the boundaries of the Milky Way,
which had a maximum diameter of about one hundred thousand
light years. This discovery also revealed that nebulae are different
star systems, and that the universe extends past the reaches
of the Milky Way. He called these galaxies extra galactic nebulae.

(02:54):
By the end of nineteen other astronomers were aware of
Hubble's findings. On December nine, four, he published his observations
for review at a meeting of the American Astronomical Society
that would take place two days later. Other astronomers accepted
Hubble's conclusions pretty quickly. Hubble went on to find and

(03:16):
describe more galaxies, dividing them into the categories of regular
or irregular, and the regular ones as spiral or elliptical
based on their shape, and he made many other significant
contributions to cosmology. In Hubble combined his work with that
of astronomer Vesto Slifer and his assistant Milton Hamison, and

(03:39):
he found an essentially linear relationship between the distances of
galaxies and their radial velocities. That concept came to be
known as Hubble's law. Put simply, it says that the
farther apart galaxies are, the faster they move away from
each other. Hubble's findings helped lead to the notion of
the expanding universe. His work had big implications Due in

(04:04):
part to his observations, Debate intensified around the idea of
the Big Bang or the universe's earliest expansion. Some said
that the universe expanded from a single point at its origin,
while others said that the universe exists in a steady state.
The Hubble Space telescope, launched by NASA, is named after him.

(04:27):
I'm Eves Jeff Coote and hopefully you know a little
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(04:52):
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