The flyby anomalies, you may remember, are a set of fascinating data indicating that spacecraft flying past Earth undergo a strange, step-like change in their acceleration.
The Galileo, Near, Cassini and Rosetta spacecraft all seem to have been hit by this weird phenomenon and while that’s not a large number of data points, it is an impressive proportion of the few spacecraft that have flown past Earth on their way to other parts of the solar system.
Nobody knows what causes this effect but there are a growing number of fascinating ideas. For example, I’ve blogged about a Casimir force-like change in inertia. And today, Stephen Adler at the Institute for Advanced Study in Princeton considers the possibility that these spacecraft are banging into lumps of dark matter as they swing past the planet.
In an impressive analysis, Adler doesn’t rule out an interaction with dark matter but he does impose some severe limits on how this process might occur. The problem is that we’ve witnessed both increases and decreases in the acceleration of these spacecraft so any dark matter model would have to allow for this.
Adler says that to fit the flyby data, the dark matter near Earth would have to be much denser than in the rest of the solar system and many orders of magnitude more dense than expected in our galaxy. It would have to be confined to a Saturn-like ring around the Earth. And it would have to consist of at least two types of dark matter.
Of course that’s possible but dark matter would have to be wildly more complex than most scientists are willing to accept at the moment. So the phenomenon remains a puzzle.
Since I last blogged about this, a major peer-reviewed study from the Jet Propulsion Laboratory has examined the data and pronounced the effect real. Which means that this is becoming one of the great outstanding challenges in modern physics. Expect to hear a lot more about it.
Ref: arxiv.org/abs/0805.2895: Can the Flyby Anomaly be Attributed to Earth-bound Dark Matter?