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Princeton astrophysicist David Spergel offered a telling historical anecdote in an address to colleagues at the American Astronomical Society's January meeting in Tucson, Arizona. In the 19th century, it dawned on astronomers that the orbits of Uranus and Mercury weren't exactly what theory predicted. So they proposed the existence of as-yet-undiscovered planets whose gravity was causing the anomalies-sort of the Cold Dark Matter of the time. Sure enough, Neptune finally appeared in their telescopes. But the other planet, Vulcan, never did materialize. In the end, said Spergel, it took the theory of general relativity to explain Mercury's odd behavior.
Which story is applicable today? Will a crucial new observation tie up the loose ends in cosmology? Or do theorists need a fundamentally new framework for understanding the universe? "I don't know," admits Spergel, noting that it's a lot easier to add bells and whistles like cosmic strings or a cosmological constant to existing theories than to come up with something as powerful as relativity.
As they search for answers, the noisy clash of egos and the confusion of conflicting claims may be taken as signs that science is alive and well and likely on the cusp of a major new insight. Says astrophysicist John Bahcall of the Institute for Advanced Study in Princeton: "Every time we get slapped down, we can say, 'Thank you Mother Nature,' because it means we're about to learn something important."