Radical Theories, Modest Formulations

23 January 2010


Albert Einstein

Bertrand Russell’s theory of descriptions was memorably called a “paradigm of philosophy” by Frank Ramsey, no mean philosopher himself. In a similar spirit, we could identify Einstein’s theory of relativity as a paradigm of science. Einstein’s work embodies all that is best in scientific thought: a fundamental re-thinking of conventional concepts used to explicate the world, topped off with bold but falsifiable predictions. The most widely known experimentum crusis for the theory of relativity was Eddington’s and Dyson’s observation of a total solar eclipse in 1919 proving the degree of deflection of light by the sun had the value predicted by Einstein.

A total eclipse in 1919 provided a very public test of Einstein's theory of relativity. While waiting for the result of the test Einstein said, 'If my theory of relativity is proven successful, Germany will claim me as a German, and France will declare that I am a citizen of the world. Should my theory prove untrue, France will say that I am a German, and Germany will declare that I am a Jew'.

There is a sense in which Einstein’s theory was truly radical. Much of the radicalness of Einstein’s theory lies in its re-thinking of the nature of space and time. Even today, it is remarkably difficult to arrive at an intuitive grasp of the curvature of spacetime. I have no doubt that physicists who have spent a lifetime on it can probably come pretty close to it, but for most people it remains as inconceivable as the Holy Trinity. However, contemporary experimental evidence for the theory of relatively distinguishes it from the latter example of inconceivability. As recently as 2004-2005, with the launch of Gravity Probe B, further experimental confirmation of relativity theory showed “frame dragging,” that is to say, that as the earth rotates it “drags” space and time around with it just a little bit.

The frame dragging effect: as a celestial body spins on its axis, it drags local spacetime around with it, much like a spinning ball in bowl of molasses would drag around some of the molasses as it spins.

As radical as Einstein’s theory was when proposed, and intuitively remains today, Einstein did not present the theory in the most radical form that it might have taken. I have two particular items in mind. Throughout his life Einstein remained skeptical of gravitational singularities (i.e., black holes), and it was only late in his career that he began to accept a non-steady-state model of the cosmos, that is to say, accepted that the universe was expanding.

We know now that the universe is not only expanding, but that its expansion is accelerating.

Einstein’s initial formulations of General Relativity, before he made the theory public, predicted the expansion of the universe. Einstein rejected this tout court, and added the cosmological constant to his equations in order to maintain the universe in a steady state, i.e., still essentially eternal and unchanging, but updated by general relativity. Einstein later came to call the cosmological constant the biggest mistake of his career. Ironically, with the relatively recent discovery of the increasing speed of the expansion of the universe, and theories of dark matter employed to explain this, there is renewed interest in the cosmological constant. It is no longer viewed as the theoretical “fudge factor” that it once was.

Edwin Hubble at the 48 inch Schmidt Telescope, Palomar Observatory, 1949. It was Hubble and not Einstein that first made us aware of the natural history of the universe.

It is now a commonplace that the universe is not static, and that in fact the world entire possesses a natural history. But when Einstein first published his theory, he published it in a form that took the possibility of a natural history of the universe off the table. He was completely confident in the truth of general relativity, and had no problem with curved space and time, but the very idea that the whole universe might change over time, that there might be cosmological evolution on a grand scale, was not something he was ready to assert. Experimental confirmation of the expansion of the universe came not from research in relativity theory, but from Hubble’s astronomical observations.

Diagram of a Kerr black hole. Einstein recognized singularities as theoretical possibilities but was skeptical that they existed in fact.

I don’t know enough about the history of general relativity to know if Einstein early on saw black holes as a prediction of his theory, but it did not take long before astrophysicists realized that general relativity did in fact predict black holes. Einstein continued to remain skeptical of their actual presence in the universe, though he conceded them to be a prediction (however unlikely) of his theory. Really robust experimental confirmation of black holes did not appear until decades after Einstein’s death, so Einstein can’t be faulted for ignoring evidence in this case.

The radicalness of relativity theory often conceals from us the extent to which it might have been presented in an even more radical form in its day. Einstein, to put it bluntly, toned it down. He gave an essentially modest formulation to his radical theory. If Einstein had started publishing about the expansion of the universe and black holes back when he published his first papers on relativity, he likely would have been dismissed as a crackpot, despite the fact that these aspects of astrophysics have become so central to contemporary cosmological thought.

I think that there is a lesson here to be learned for the whole debate over Kuhn’s influential philosophy of science, that is to say, the idea that scientific change comes from a revolutionary paradigm shift, and that the old theory isn’t replaced so much as the advocates of the old theory die off while all the younger minds in the field have taken to the new theory. It has been a source of endless philosophical debate as to whether such paradigm shifts can be considered to be rational, or whether we must hold that the history of science is as arbitrary and as irrational as, for example, the history of politics.

By presenting a relatively modest formulation of relativity theory, and setting aside some potentially radical (and off-putting) consequences of the theory, Einstein made relativity theory more palatable to his potential audience. Darwin, who represents another paradigm of science, did the same thing. The Origin of Species never mentions human evolution.

In so far as scientists presenting radical theories first publish and argue for the most diplomatic formulations of their theories, they are making a concession to expected resistance to the radical ideas that are essential to the theory in question. Non-essential radicalness becomes an unnecessary risk, and a risk to be avoided if possible.

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Note Added 05 May 2011: A new story on the BBC website, Gravity Probe B confirms Einstein effects, further discusses the work of Gravity Probe B in demonstrating the frame-dragging effect of general relativity.

Gravity Probe B and frame-dragging

1. The gyros’ spin axes were aligned with a guide star, and then monitored for changes in their angle of spin caused by general relativity effects
2. The disturbance due to frame-dragging was expected to cause the spin axes of the super-smooth spheres to change by just 0.039 arcseconds a year
3. For the geodetic effect, the spacecraft expected to see a bigger signal – for the spin axes to change by an angle of 6.6 arcseconds over one year
4. Gravity Probe B’s gyroscopes were held inside a special vacuum container that was designed to insulate them against all other confounding forces
5. Nasa launched GP-B on 20 April, 2004, but it started funding the mission concept in 1963, long before Neil Armstrong had stepped on the Moon

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Grand Strategy Annex

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