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Archive for Saturday, May 19, 2007

Physicists get kudos for die-off theory

KU professors say galaxy’s movement affects life on Earth

May 19, 2007

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If two Kansas University physicists are correct, things will start getting ugly on Earth in about 10 million to 12 million years.

"Increased cloud cover, increased mutations, cancer," Adrian Melott said Friday, ticking off some of the hazards he foresees coming about because of increased exposure to cosmic rays, or radiation.

Melott and KU colleague Mikhail Medvedev have won acclaim in science circles recently for their ideas about how the movement of the galaxy may help account for massive "die-offs" on Earth on a strikingly regular schedule.

For the moment, Melott said, their theory is of "medium-large" significance in the world of physics and astronomy.

"Like most new ideas in science, it's probably wrong," Melott said. "If it were to turn out to be right, it would be huge."

In 2005, two University of California-Berkeley researchers found by examining fossil records that massive extinctions happen on Earth about once every 62 million years. But an explanation for why that happens has been lacking.

"For months and months and months I sort of obsessed about this, and then arrived at an idea for what could be explaining it," Melott said.

To understand the nutshell version of Melott and Medvedev's theory, picture a pie flying upward through space. That's our galaxy.

Actually, the galaxy is thinner than a pie and is shaped more like a Frisbee, but set that aside for a moment.

Now, picture our solar system toward the outer edge of the pie, orbiting around the pie's center and wavering up toward the top of the crust and back down toward the bottom as it orbits.

About once every 64 million years, the solar system wavers up to the top edge of the galaxy - the top crust of the pie, if you will. There, Melott said it's "bombarded" with higher doses of radiation, as the top of the rising galaxy collides with gases in the universe.

The 62-million-year estimate of the extinction cycle and the 64-million-year estimate of the solar system's motion match, Melott said, because both calculations have a 3-million-year margin of error.

Melott, a professor of physics and astronomy, and Medvedev, an associate professor in the same department, presented the idea in April at a meeting of the American Physical Society. Their paper on the subject also has been accepted for publication in the Astrophysical Journal.

One person who appreciates the idea is the Berkeley professor who discovered the regular die-off cycle.

"They succeeded where I failed in coming up with a possible explanation for the effect that we observed," Richard Muller told KU's campus news service. "It's the most elegant solution that's been uncovered."

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