I’m hoping that something staggering happened this morning. At 7.45 GMT, about an hour and a half ago as I write this, the spacecraft Rosetta performed a slingshot manoeuvre, using the Earth’s gravitational field to change course, rather than burning extra fuel. That’s not the staggering thing: that trick has become quite routine for spacecraft on long journeys. What is staggering is the possibility that, during the slingshot, Rosetta gained an extra 1mm/s in speed.
When the craft is travelling at 13 km/s, that doesn’t seem like a lot. But the gain in speed, if it happened, stands in defiance of all known physics. The prediction of an extra 1mm/s came from John Anderson, the man behind the NASA Pioneer missions in the 1970s. He has noticed that many spacecraft see anomalous speed changes during a slingshot. There is no law of physics that says why this should happen, but Anderson has worked out a formula that accounts for all previous speed changes in terms of spacecraft velocity, angle of approach relative to the planet’s spin, distance of closest approach and so on (you can hear him talk about it here). And, with Rosetta coming in for a near-Earth flyby, he was able to make a prediction about what would happen.
It’s scientific progress, right here, right now. We’ll find out what Rosetta did in a few days or maybe a few weeks. If Anderson is right, we have spotted a phenomenon that defies explanation. The history of science is full of such things; that’s how we got quantum theory started, for instance. If Anderson’s formula also works for Rosetta, maybe we will see the birth of something fundamentally new in science. It’s not often you can say that. Watch this space!
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