Earth's end may be sooner than expected

Technology Review - 1.14.10

Dark Matter May Explain the Puzzling Change in Earth-Sun Distance

If the sun sweeps up dark matter as it moves through the galaxy, how would that affect the orbit of the planets?

In the last five years or so, astronomers have noticed a puzzling change in the astronomical unit, the distance of the Earth's from the sun. Various measurements indicate that this distance (or at least the length of the Earth's semimajor axis) is increasing at the rate of 15 cm per year (plus or minus 4 cm).

Why that should be, nobody knows. But today, Lorenzo Iorio at the National Institute of Nuclear Physics in Pisa, Italy, says dark matter could be to blame.

Astronomers have long assumed that dark matter must fill the universe. In fact, the motion of the Milky Way implies that there ought to be some 10^-25 grams of the stuff in every cubic centimeter of the galaxy. And the density ought to be even higher near massive bodies such as stars, whose gravity would attract a halo of dark matter. Around the sun, the density of dark matter should be about 10^-19 g/cm^3.

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