Sunday, September 19, 2010

A dark force

Researchers say Pioneer 10, which took the first close-up pictures of Jupiter before leaving our solar system in 1983, is being pulled back to the sun by an unknown force. The effect shows no sign of getting weaker as the spacecraft travels deeper into space, and scientists are considering the possibility that the probe has revealed a new force of nature. ...

Research to be published shortly in The Physical Review, a leading physics journal, will show that the speed of the two [Pioneer] probes is being changed by about 6 mph per century - a barely-perceptible effect about 10 billion times weaker than gravity. ...

Scientists initially suspected that gas escaping from tiny rocket motors aboard the probes, or heat leaking from their nuclear power plants might be responsible. Both have now been ruled out. The team says no current theories explain why the force stays constant: all the most plausible forces, from gravity to the effect of solar radiation, decrease rapidly with distance. ...

Assertions by some scientists that the force is due to a quirk in the Pioneer probes have also been discounted by the discovery that the effect seems to be affecting Galileo and Ulysses, two other space probes still in the solar system. Data from these two probes suggests the force is of the same strength as that found for the Pioneers.
--Robert Matthews, Telegraph, on a mysterious tug home. HT: Gizmodo

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