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A
supernova or dying star can be used to determine at what rate
the universe is expanding.
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In
the early 1990s, two groups of astronomers came up with a new technique
for discovering the ultimate fate of the universe: find dying stars,
or supernovae, and measure their age and distance. Each team expected
to find that gravity — especially that of the recently discovered
Dark Matter
— had slowed the expansion of
the universe and that the universe would eventually collapse. What
they found instead shocked them: not only is the universe still
expanding, it's also speeding up.
If
gravity wasn't slowing down the universe, what was speeding it up?
Albert Einstein used an equational "fudge factor" to allow for —
if not explain — the idea of anti-gravity, later calling it
his "greatest blunder." But astronomer Michael Turner was the first
to name this force that could push the universe apart: Dark Energy.
Together,
Dark Matter and Dark Energy rule our universe. To learn more about
their titanic struggle, astronomers at the Hubble Space Telescope
have been looking at some half dozen supernovae, ranging in age
back to 11 billion years ago. They've determined that the turning
point in the history of the universe came about 5 billion years
ago. That's when Dark Matter began losing its gravitational pull
against Dark Energy's inexorable push and the universe's expansion
stopped slowing down and sped up. Now they want to know what, exactly,
Dark Energy is.
Help
in this search may come from a proposed new spacecraft expressly
designed for supernova hunting. Able to image thousands of supernovae
at a time, the SNAP satellite might not only help find out what
Dark Energy is, but also help answer an even bigger question: Is
there a reason why the universe maintains an almost perfect balance
between the pull of Dark Matter and the push of Dark Energy? Or
is the fact that Dark Energy didn't blow the universe apart in its
infancy just a lucky accident?
For
more on this topic, see the web feature:
Back to the Big Bang
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