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The Question
(Submitted October 19, 1997)
I've been trying to figure out exactly what the Hubble Constant is for quite
a while. I know that it has to do with the expansion rate of the Universe and
that it can also directly yield the distance scale and the age of the Universe.
Could you possibly explain it to me in fairly simple terms. I'm in 11th grade
and I've had about a month's worth of class on astronomy.
The Answer
Early in this century Edwin Hubble discovered that galaxies are
moving rapidly away from us (this was the first evidence for the big bang
theory for the creation of the Universe). He also discovered that more
distant galaxies were moving away at a higher velocity and proposed the
following relationship:
v = H*r
where v is the velocity of the galaxy, r is distance and H is Hubble's
constant. Finding a more precise value for Hubble's constant is an area
of very active research, since many questions of cosmology are tied up
with this value. Here are a few URLs that are related to the
Hubble Constant:
http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970321d.html
http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970326e.html
I hope this helps,
Jeff Silvis
For Ask a High-Energy Astronomer
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