|We're studying the universe right now in science
and it said that the universe is expanding but
the book or my notes didn't say how fast it's
expanding, I was hoping you could help me.
|Question Date: 2002-12-05|
Over 70 years ago, Edwin Hubble announced his
findings that the universe appeared to be
expanding in all directions. Since then,
scientists have been trying to measure the rate of
expansion. Interestingly, the rate of expansion
is not the same everywhere in the universe.
The rate galaxies move away from each other is
proportional to distance (the farther away the
galaxy, the faster it seems to be moving awa).
Therefore, the rate of expansion of the
universe, known as Hubble's constant, is in
units of velocity per distance. So, for example,
if an object is twice as far away, it will appear
to be moving away at twice the velocity.
Reported values of Hubble's constant seem to
vary between 50 to 100 km/s/megaparsec (a
megaparsec is about 3.3 million light years).
A few years ago, a study using the Hubble
Telescope came to a value of 70 km/s/megaparsec.
Note from ScienceLine Moderator:
The current date for this answer is December 5th 2002.
Well, when we say the universe is expanding, we
mean that space itself is getting bigger and
pushing the galaxies apart. Imagine putting dots
on a balloon and then blowing it up. As the
balloon expands, the dots move apart. And the
farther apart the dots are, the faster they move
away from each other. So we measure the
expansion of the universe by saying that, if a
galaxy is so far away, it is moving away from us
so fast. This measurement is called the
Hubble parameter, and it is roughly that a
galaxy is moving away from us about 70
kilometers/second for every megapersec that
the galaxy is distant from us. A megapersec is
about 3 million light years (a light year is
the distance light travels in a year, and light
takes only about 8 minutes to reach the sun!).
If I've done my conversion factors correctly,
this means that the universe expands by about
0.0000000001% every year.
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