Will probe's upcoming fly-by unlock exotic physics?

The Rosetta probe will fly by Earth on Friday (Illustration: ESA/C. Carreau)

Courtesy of New Scientist
by David Shiga

What's causing spacecraft to mysteriously accelerate? The Rosetta comet chaser's fly-by of Earth on 13 November is a perfect opportunity to get to the bottom of it.

The anomaly emerged in 1990, when NASA's Galileo spacecraft whizzed by Earth to get a boost from our planet's gravity and gained 3.9 millimetres per second more than expected. And the European Space Agency's Rosetta spacecraft had an unexpected increase of about 1.8 millimetres per second during a previous fly-by of Earth in 2005.

Scientists have ruled out various mundane explanations like atmospheric drag or the effect of deviations in Earth's shape. This has led some to propose that exotic new physics is involved, such as modifications of Einstein's general relativity, the currently accepted theory of gravity.

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