More to Explore 151
Andromeda lay 900,000 light-years away. That proved that Andromeda was a separate
galaxy. It lay too far away to be a fringe part of the Milky Way.
Within six months, Hubble had studied and measured 18 other nebulae. They were all
separate galaxies, ranging from five to 100 million light-years from Earth. Astronomers
were shocked to learn that the universe was so big and that it likely contained thousands of
separate galaxies.
But Hubble was just beginning. He had noticed a consistent red shift when studying
the light emitted from these distant nebulae.
Scientists had discovered that each element (helium, hydrogen, argon, oxygen, etc.)
always emitted energy in a characteristic set of specific frequencies that identified the element’s presence. If they made a spectrograph (a chart of the energy radiated at each separate
frequency) of the light being emitted from a star, the lines on the spectrograph would tell
them which elements were present in the star and in what relative quantities.
Hubble found all the common spectrograph lines for helium, hydrogen, and so forth
that were normally found in a star. But all the lines on his graph were at slightly lower frequencies than normal. It was called a red shift because when visible light frequencies are
lowered, their color shifts toward red. If their frequency is raised, their color shifts toward
blue (a blue shift).
Over the next two years, Edwin Hubble conducted exhaustive tests of the 20 galaxies
he had identified. He found that every one (except Andromeda) was moving away from
Earth. More startling, the galaxies moved away from us and away from each other. Every
galaxy he studied was speeding straight out into open space at speeds of between 800 and
50,000 kilometers per second!
The universe was expanding, growing larger every second as the galaxies raced outward. It was not a static thing that had remained unchanged since the beginning of time. In
each moment the universe is different than it has ever been before.
Fun Facts: Because the universe is expanding, every galaxy in existence
is moving away from our own Milky Way—except for one. Andromeda,
our nearest neighbor, is moving on a collision course with the Milky
Way. Don’t worry, though: the collision won’t occur for several million
years.
More to Explore
Barrow, John. The Origin of the Universe. New York: Basic Books, 1994.
Burns, Ruth Ann. Stephen Hawking’s Universe (video). New York: WNET, 1997.
Haven, Kendall, and Donna Clark. 100 Most Popular Scientists for Young Adults.
Englewood, CO: Libraries Unlimited, 1999.
Munitz, Milton, ed. Theories of the Universe: From Babylonian Myths to Modern Science. New York: Free Press, 2001.
Rees, Martin. “Exploring Our Universe and Others.” Scientific American 281, no. 6
(December 1999): 78–83.