Geography Reference
In-Depth Information
Was There a Big Bang?
Most—but not all—astronomers will answer yes to this question. Like Darwin's “theories,” the
Big Bang
Theory
, which sets out to explain the creation of the universe, can only be disproven, not proven. But it
is supported by a growing body of evidence. In science, a theory is not a good guess; it means a “well-
supported explanation of some aspect of the natural world . . . repeatedly confirmed through observation
and experiment.” Nonetheless, it is always wise to remember that some of the best-educated people in the
world believed the earth to be the center of the universe and thought Galileo was a nut-case and a heretic
for his theories. It only takes a single discovery to shatter a world of preconceptions.
Basically, the Big Bang holds that time, space—all matter—began in one momentous instant: a hot,
dense explosion that took place ten to twenty billion years ago. This was suggested in 1927 by a Belgian
priest, Georges Lemaître, who proposed that the universe started with the explosion of a “primeval atom,”
in which all the mass of the universe had been concentrated in an extremely small space. In the first few
millionths of a second
, space expanded incredibly quickly for a very short time.
The notion of a big bang creation got a serious start from Edwin Hubble, the astronomer who dis-
covered galaxies. At about the same time, Hubble determined that the galaxies were moving away from the
earth. To be more precise, galaxies are moving away from each other. He also discovered that the farther
away a galaxy is, the faster it is moving. In very simple terms, this was the basis for the theory that the
universe is expanding.
Think of dropping a water balloon. It hits the ground and the water spreads outward from a central point
of impact. The bigger the balloon, the more water—thus, the bigger the puddle that spreads out from the
center. Like a cosmic water balloon sending out its immense puddle at the moment of impact, something
had to propel the galaxies outward. That something was presumably the Big Bang.
The next major piece of evidence came in 1965 from two physicists working for the Bell Telephone
Laboratories, Arno Penzias and Robert Wilson. While trying to refine their microwave-antenna equipment,
the two men accidentally discovered a radio wave “hiss” that suggested to the scientists the remnants of
the Big Bang.
Finally, in the spring of 1992, a team at the Lawrence Livermore Laboratory in California led by as-
trophysicist George Smoot announced a startling find that supported the Big Bang Theory. The new data
came from Cosmic Background Explorer (COBE), a $160 million U.S. satellite launched in 1989 to meas-
ure microwave radiation in space. Describing their discovery as “wrinkles” in the smooth “fabric” of the
universe, the team dated these wrinkles to 300,000 years after the Big Bang, a flash in cosmic time.
Now go back to the water balloon. Eventually, the water stops spreading. That is just one of many big,
unanswered questions about the Big Bang and the future of the universe. Will the universe continue its
expansion, moving outward infinitely? Or will it reach a limit, a point of maximum expansion after which
the collective force of gravity will start pulling all those cosmological bodies yo-yo-ing back in toward the
center? This possibility is called the
big crunch
. Whatever you think the answer is, you don't actually have
to sweat it. We're looking at a time frame of several billion years here.
The new data also supports a theory that has been moving up and down the astrophysical popularity
charts. It holds that much of the universe is composed of dark matter that we can't see.
Did an Asteroid Kill the Dinosaurs?
