Dark energy and dark matter mysteries - Update

The Mysteries currently facing the Dark Energy Scientists can be compiled into a small list.

• Gravity acting across vast distances does not seem to explain what astronomers see
• Galaxies, for example, should fly apart; some other mass must be there holding them together
• Astrophysicists have thus postulated "dark matter" - invisible to us but clearly acting on galactic scales
• At the greatest distances, the Universe's expansion is accelerating
• Thus we have also "dark energy" which acts to drive the expansion, in opposition to gravity
• The current theory holds that 73% of the Universe is dark energy, 23% is dark matter, and just 4% the kind of matter we know well

For decades, the strange substance called dark matter has teased physicists, challenging conventional notions of the cosmos.

Today, though, scientists believe that with the help of multi-billion-dollar tools, they are closer than ever to piercing the mystery -- and the first clues may be unveiled just weeks from now.

"We are so excited because we believe we are on the threshold of a major discovery," said Michael Turner, director of the Kavli Institute for Cosmological Physics at the University of Chicago, at an annual conference of the American Association for the Advancement of Science (AAAS).

Dark matter throws down the gauntlet to the so-called Standard Model of physics.

Elegant and useful for identifying the stable of particles and forces that regulate our daily life, the Standard Model only tells part of the cosmic story.

For one thing, it does not explain gravity, although we know how to measure gravity and exploit it for our needs.

And the Standard Model has been found to account for only around four or five percent of the stuff in the Universe.

The rest is dark matter, making up 23 percent, and dark energy, an enigmatic force that appears to drive the expansion of the Universe, which accounts for around 72 or 73 percent.

"On the cosmology side we now understand that this mysterious dark matter holds together our galaxy and the rest of the Universe," said Turner.

"And the tantalizing thing on the cosmology side is that we have an airtight case that the dark matter is made of something new... there is no particle in the Standard Model that can account for dark matter."