27 May 2004

Cosmos at full throttle

Anyone reading their results might be excused for feeling a bit special. The team found that 4 percent of the universe is made of ordinary matter. Another 21 percent consists of so-called dark matter, inferred from its gravitational effects on matter. The remaining 75 percent consists of dark energy, which exerts a form of pressure that makes it act like gravity thrown into reverse. These figures are consistent with results reported last year from satellite measurements of the big bang's afterglow - the cosmic microwave background.

If the quantity of dark energy is constant, astronomers say, the universe will continue to expand at an increasing rate. In about 20 billion years or so, only about 100 galaxies might be visible from Earth. Think of it as the 'big lonely.' If dark energy were to change with time, it could relax to let gravity once again dominate, prompting the universe to collapse in the 'big crunch.' Or if the pace speeds up, it could lead to the 'big rip,' in which the fabric of space-time stretches so rapidly that even atoms get torn apart.

Based on the team's observations, dark energy is holding steady and 'behaves much like the cosmological constant in Einstein's theories' about the evolution of the universe, says Steve Allen, an astronomer at Cambridge University in England and the team leader.

Essentially, this means that the amount of energy per volume of space remains constant. If this observation holds up under more rigorous programs, it would substantially narrow the range of explanations for what dark energy really is.

I bet you thought I couldn't blog on dark energy without implying a causal relationship between dark energy and the rule of the Man of Steel and the Great Dubya. Well, you were wrong. So there.

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