Gregg Easterbrook, Flat-Earther

The editorial standards of The New Republic are even lower than I had supposed. Brad DeLong has delivered a smackdown to TNR's senior editor Gregg Easterbrook. Easterbrook has taken the news that Stephen Hawking has refined some of his key ideas on the nature of gravitational collapse and black holes as an opportunity to denounce Hawking as a kook.

To read Easterbrook, Stephen Hawking has been getting away with nonsense pronouncements because other scientists are too embarassed to call him on them, perhaps because they feel uncomfortable contradicting a cripple. But now Hawking has confessed, the game is up, and we can now forget we ever heard of black holes.

This of course has nothing to do with the facts of the matter. If you do the math (I have; has Easterbrook?) it is straightforward to see that the ideas about black holes that Hawking propounded thirty-odd years ago were in fact reasonable ones.

Easterbrook clearly hasn't done the math. Brad DeLong catches him out as an almost total ignoramus about gravity. What is gravity? Easterbrook asks. No one has the slightest idea. That gravity exists is indisputable, and the equations by which it functions have been so precisely refined that NASA can guide space probes moving amid the outer planets. But the what of gravity – how it works – is a total unknown. ... Einstein speculated that the mass of every object causes space-time to curve, and then less massive objects roll downward on the curvature, and that's where gravity comes from. But wait, even if space is curved by mass, why do objects roll down the curvature – what pulls them?

Anyone who has taken a class in modern gravity physics would recognize this as the same kind of idiocy as that of those critics of space travel who insisted that rockets can't work in a vacuum because there's nothing to push against. DeLong says, in general relativity objects don't "roll downward" on the curvature. Objects that are not pushed by the strong or the electroweak force move through curved space along that space's "straight lines" – i.e., they follow the shortest distance between any two points – according to the (relativistic version of) Newton's First Law of Motion: a body in uniform motion will continue in uniform motion. That's right: a freely falling object follows a geodesic path in curved spacetime. Matter and energy, in the form of the stress-energy tensor, change the shape of spacetime.

What's more, the equations that NASA's scientists use to guide space probes around the outer planets are Einstein's equations, not Newton's. Newton's theory of gravity isn't good enough for the necessary precision. Einstein's description of curved spacetime does the job. The curvature of spacetime is detectable, observable, measurable.

The only question that remains is this: Why does Marty Peretz give this nutbar Easterbrook the space to peddle such sophmoric twaddle?

(via Eschaton)