The galaxies outside of our own are moving away from us, and the
ones that are farthest away are moving the fastest. This means
that no matter what galaxy you happen to be in, all the other galaxies
are moving away from you.
However, the galaxies are not moving through space, they are moving
in space, because space is also moving. In other words, the universe
has no center; everything is moving away from everything else.
If you imagine a grid of space with a galaxy every million light
years or so, after enough time passes this grid will stretch out
so that the galaxies are spread to every two million light years,
and so on, possibly into infinity.
The universe encompasses everything in existence, from the smallest
atom to the largest galaxy; since forming some 13.7 billion years
ago in the Big Bang, it has been expanding and may be infinite
in its scope. The part of the universe of which we have knowledge
is called the observable universe, the region around Earth from
which light has had time to reach us.
One famous analogy to explain the expanding universe is imagining
the universe like a loaf of raisin bread dough. As the bread rises
and expands, the raisins move farther away from each other, but
they are still stuck in the dough. In the case of the universe,
there may be raisins out there that we can’t see any more
because they have moved away so fast that their light has never
reached Earth. Fortunately, gravity is in control of things at
the local level and keeps our raisins together.
Who Figured This Out?
The American astronomer Edwin Hubble made the observations in
1925 and was the first to prove that the universe is expanding.
He proved that there is a direct relationship between the speeds
of distant galaxies and their distances from Earth. This is now
known as Hubble’s Law. The Hubble Space Telescope was named
after him, and the single number that describes the rate of the
cosmic expansion, relating the apparent recession velocities of
external galaxies to their distance, is called the Hubble Constant.
So, is the Universe Infinite?
It might be easier to explain about the beginning of the universe
and the Big Bang Theory, than to talk about how it will end. It
is possible that the universe will last forever, or it may be crushed
out of existence in a reverse of the Big Bang scenario, but that
would be so far in the future that it might as well be infinite.
Until recently, cosmologists (the scientists who study the universe)
assumed that the rate of the universe’s expansion was slowing
because of the effects of gravity. However, current research indicates
that the universe may expand to eternity. But research continues
and new studies of supernovae in remote galaxies and a force called
dark energy may modify the possible fates of the universe.
Robert, and others. Universe. New York, DK Pub.,
2005. 512 p.
Karen C. The big bang theory: what it is, where it
came from, and why it works. New York, Wiley, c2002.
David M.. The big bang: a view from the 21st century. London,
New York, Springer; Chichester, Eng., In association
with Praxis Pub., c2003. 262 p.
Govert. Evolving cosmos. Cambridge, Eng., New
York, Cambridge University Press, 2004. 135 p.
information about the universe and the scientific theories
of the evolution of the universe: an anthology of current
thought. Edited by Rick Adair. New York, Rosen
Pub. Group, 2006. 192 p.
Joseph. The infinite cosmos: questions from the frontiers
of cosmology. Oxford, New York, Oxford University
Press, 2006. 248 p
more print resources...
Search on " Cosmology--Popular
works," " Astronomy," or "Physics--Popular Works"
in the Library of Congress Online
of expanding raisin bread. Wilkinson Microwave Anisotropy Probe,
NASA Web site.
Hubble, with the 48-inch telescope on Palomar Mountain. Photo:
NASA's Astronomy Picture of the Day Web site.
Space Telescope - the largest orbiting public optical telescope
in history. NASA Web site.
The following four images were taken
by the Hubble Space Telescope, and can be found at NASA's Hubblesite image
NGC 1512 in Visible Light
Storm of Turbulent Gases in the Omega/Swan Nebula (M17).
Supernova Remnant In Visible, X-Ray and Infrared Light.