- Everything you can see ñ from a distant nebula
to the family dog ñ makes up only about 5 per cent of the universe.
The rest is mystery stuff ñ dark matter and dark energy.
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- We should be wary of equating existence with visibility
because most of the universe is not something we can see, University of
Toronto astronomy professor John Percy told globeandmail.com.
-
- Although these concepts are not new, evidence has been
piling up "almost exponentially" especially over the past decade
as astronomers are able to use more advanced technology to see farther
distances, he said.
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- Dark matter is similar to normal matter in that it exerts
gravitational force, Prof. Percy said, but most similarities end there.
Some of the remaining 95 per cent might be made up of dark objects like
planets, but "most likely it's some kind of elementary particle which
doesn't interact much with other things."
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- Scientists have called these particles WIMPs (weakly
interacting massive particles), which are difficult-to-detect elementary
particles that interact weakly with normal matter, Prof. Percy said. Beyond
such notions, he said, it is difficult to pin down the exact form of the
matter.
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- "Dark matter is quite widely distributed, it exists
in parts of the galaxy where there are not very many visible stars and
planets," he said.
-
- He said another example of an elementary particle is
a neutrino, which may make up a small component of dark matter. A neutrino
is a sub-atomic particle with no charge that can fly through matter as
if it wasn't there.
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- Although the existence of dark matter has been theorized
since the 1930s, it didn't become a well-established notion until the 1960s,
Prof. Percy said.
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- Dark energy manifests itself by pushing the universe
apart in opposition to the gravity that is pulling it together, Prof. Percy
explained. It was first observed when astronomers discovered that the universe
is gradually accelerating in its expansion.
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- There is nothing comparable to dark energy on earth,
Prof. Percy said. But for the purposes of imagination, if there was a force
such as dark energy that was effective on a smaller scale in the same way
gravity is, if one dropped a coin, the force would let it fall, stop it,
then send it shooting upwards, he said.
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- Dark energy only becomes apparent when you look at things
farther away on massive scales such as distant universes, he explained.
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- "These are the things that many astronomers and
physicists are working on right now," Prof. Percy said, "It's
really among the most fundamental questions in the universe: What is the
universe made of?"
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- In 2003, The Globe and Mail reported on the Wilkinson
Microwave Anistropy Probe, a satellite barely the size of a minivan that
proved stars formed 200 million years after the Big Bang and not 500 million
years as previously accepted. It also indicated that the universe expanded
greatly in its first few moments of existence, and that it will keep expanding
forever.
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- "You shouldn't feel small," Prof. Percy laughed
in response to a comment that these discoveries have a way of reminding
earthlings that our planet is but an infinitesimal fraction of the universe.
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- Controversy erupted when Galileo dismissed the commonly-accepted
geocentric theory in the early 1600s, that the cosmos revolved around the
earth, and he theorized, correctly, that the earth actually revolved around
the sun.
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- Prof. Percy adds that he is often reminded of a quotation
from French scientist Henri Poincare, "Astronomy is useful because
it shows how small our bodies how large our minds."
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- © Copyright 2004 Bell Globemedia Publishing Inc.
All Rights Reserved. http://www.theglobeandmail.com/servlet/story/RTGAM.20040617
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