Revolutions in Physics

It was the turn of the twentieth century and the bear prowled the market for physicists. Max Planck’s sympathetic professor had urged the bright young man to find work in another field, say the design of advanced horse-drawn carriages, something useful. Even Albert Einstein could not find employment in his chosen profession. Why not? Well it was simple supply and demand, with demand scarce when there was almost nothing left to do.

After the giants Newton and Maxwell (and a few others) had made all the big discoveries, it was generally believed that there was precious little left for the few extant physicists to work on. Lord Kelvin, the fellow associated with “absolute zero,” identified the two remaining big problems -- why light travels at a constant speed? -- what causes the particular spectral radiation from hot objects? -- to be the “twin clouds in the otherwise clear sky of knowledge.” If Kelvin assigned one physicist to each problem and gave him a ten year contract, surely those two inconsequential problems would yield solutions.

Then everything changed. Albert Einstein, still unable to find a physics job, was employed as a Swiss patent examiner. In his spare time, Einstein worked on the two remaining big problems, and joined with friends to create a weekly discussion club on science and philosophy (which they grandly named “The Olympia Academy.”) The group studied a variety of thinkers such as the polymath Poincare, and the logical positivist philosophers Hume and Mach.

In the fateful year of 1905, young Al published three seminal papers that essentially solved the light speed problem and explained the mystery of the hot body spectrum, while founding two new fields of study. Relativity and quantum mechanics were (partially) born in the Bern patent office.

Einstein’s 1905 paper “On the Electrodynamics of Moving Bodies” modified Galileo's principle of relativity, that all uniform motion was relative. Thus a person on the deck of a ship may be at rest in his opinion, but someone observing from the shore would say that he was moving. Einstein postulated that all observers will always measure the speed of light to be the same, no matter what their state of uniform linear motion is.

Thus if you are a stationary observer and you measure the speed of a light wave you will obtain c = 186,000 miles per second. If you are travelling on a fast plane and measure the light speed you again obtain c, not just a little bit less. And if you are on a warp drive space ship moving at 0.9 c, you will again measure the speed of light to be… c. It is a mystery, as no other wave behaves like that.

The public responded giddily to the new relativity. Positivists (see Auguste Comte) who believed that the only authentic knowledge is scientific knowledge welcomed the triumph of rationality. Relativists claimed that Einstein’s theory showed that culture and morality are relative, i.e., dependent on one’s perspective. It is too bad that Einstein did not choose a title such as the theory of Invariance rather than Relativity.

In 1905 Einstein also addressed the theory of the photo-electric effect whereby a light beam impinges on a metal surface and an electron is emitted. He used a concept due to Max Planck that treated the light as not a wave but as a beam of discrete energetic particles, now called photons. Planck had used the construct of discrete energy states of matter and discrete photon energies to explain the hot body spectrum, ie unsolved problem number two. He considered that the quantization was only “a purely formal assumption.” Einstein showed that the photons were real and that light has a dual character, sometimes wave, sometimes particle.

Before long, Bohr, Schrodinger, Heisenberg, Pauli and others had developed the detailed formalism of quantum physics that could be used to make predictions of nature on the atomic scale. The theory was, however, strange, even compared to Relativity. There were quantized energies; wave-particle duality; the Uncertainty Principle; and the probability interpretation of events, whereby the result of an experiment could be predicted with only statistical certainty. The quantum mechanical wave function in this so-called Copenhagen interpretation was viewed as describing the behavior of an ensemble of identical systems that individually may sometimes behave one way, sometimes another.

But what happened to causality? To determinacy? Must one abandon conceptual clarity to get at the answers? Einstein rejected the theory, refusing to believe in a God who “plays dice with the universe.” Many physicists clung to a belief in hidden variables, under the surface of events, that control the output in a deterministic way, but which we cannot see. Others simply said that there must be underlying physical laws that we do not yet understand.

However, the mainstream interpretation has remained much as the Coppenhagen school defined it, with quantum mechanics seen as a way to calculate the output of experiments in all their statistical glory, without regard to any underlying intuition. That formalism has been the most magnificient scientific edifice ever seen, decribing the microscopic behavior of systems with astounding accuracy, and encompassing the full quantum electrodynamic behavior of light and matter and the weak and strong nuclear forces. Only gravity remains outside the unified theory, and it is handled by Einstein’s (that fellow again!) theory of General Relativity.

More recently, the unease with the statistical nature of quantum mechanics has resurfaced in two arenas. In the “Many Worlds Interpretation”(MWI) held by such eminent physicists as Stephen Hawking and Steven Weinberg, at every instant when a quantum measurement is made, the universe splits into two or more universes, each corresponding to a possible future. Everything that can happen at each juncture happens. Some, like Hawking, take these parallel universes as no more than abstract mathematical entities -- worlds that could have formed but didn't. In this interpretation the MWI becomes little more than a whimsical language for talking about QM.

However some physicists actually believe that the new universes are “out there,” in some sort of vast super-space-time. David Deutsch, head of the quantum computer group at Oxford University has become the top booster of the MWI in this form. (Check out the Oxford Centre for Quantum Computation's Web site at www.Qubit.org.)

Another weird concept is that of a “multiverse” proposed by Andrei Linde and Martin Rees. In the multiverse, every now and then a quantum fluctuation precipitates a Big Bang and a new universe springs into existence with randomly selected values for its fundamental physical constants. In most of these universes those values will not permit the formation of stars and life. However, in a unique universe the constants will be just right to allow creatures like you and me to evolve. We are here not because of any overhead intelligent planning (i.e. God) but simply because we happen by chance to be in the universe properly tuned to allow life to get started.

Martin Gardiner has written about all these interpretations in a fascinating article called “ Multiverses and Blackberries.” He concludes:

“Surely the conjecture that there is just one universe and its Creator is infinitely simpler and easier to believe than that there are countless billions upon billions of worlds, constantly increasing in number and created by nobody. I can only marvel at the low state to which today's philosophy of science has fallen.”