Monday, May 6, 2013

Modern physics is not crummy

I am unhappy with this new podcast: Live From NECSS With Jim Holt On Why Does the World Exist?

Holt is a fine science journalist, and most of the discussion was about silly and unanswerable philosophical questions. But I believe he also painted a seriously inaccurate picture of modern physics.

He said that the universe is so "crummy", "not elegant", with "60+ elementary particles", 110 elements, and the "standard model is so ugly". [at 15:00] The argument is that God should have been able to create a simpler design.

This is wrong. The standard model is quite elegant. All matter is made of quarks and electrons, with energy being transmitted by bosons. You can only get to 60+ particles if you count colors, flavors, anti-particles, etc as separate particles. I still don't know how you get to 60 unless you also include supersymmetric and other fictitious particles.

The second wrong opinion is that it is "impossible to give a realistic interpretation of quantum theory", and "impossible to make sense of it", with the obligatory R.P. Feynman quote. [at 33:20]

There are textbook explanations of quantum mechanics that make perfect sense, and that has been true since about 1930. There are people who claim that it would make more sense with hidden variables or parallel universes or other such nonsense, but they have been proven wrong for 80 years. Lee Smolin is a recent example.

Yes, I know that Feynman said that quantum mechanics is hard to understand, and that is true if you want to relate it to everyday macroscopic experience. But you can understand the theory by just reading Feynman's textbook.

MIT physicist Alan Lightman reviews Smolin's book in the NY Times:
He rightly remarks that Einsteinian physics frames time as a relative concept in which the line between past and future varies with the observer. ...

Twentieth-century physics has brought us two kinds of strangeness: strange things we more or less understand, and strange things we do not understand. The first category includes relativity and quantum mechanics. Relativity reveals that time is not absolute. Clocks in relative motion to each other tick at different rates. We don’t notice relativity in daily life because the relative speed must be close to the speed of light before the effects are significant. Quantum mechanics presents a probabilistic picture of reality; subatomic particles act as if they occupy many places at once, and their locations can be described only in terms of probabilities. Although we can make accurate predictions about the average behavior of a large number of subatomic particles, we cannot predict the behavior of a single subatomic particle, or even a single atom. We don’t feel quantum mechanics because its effects are significant only in the tiny realm of the atom.
I know what he is trying to say here, but this is wrong. Relativity does not deny absolute time. When cosmologists say that the age of the universe is 13.8B years, they are using absolute time. We can distinguish the past from the future. Clocks don't tick at different rates; they only appear that way to certain observers. We can see relativistic effects in the form of magnetism.

Probability is not essential to quantum mechanics. We can apply the theory to predict the behavior of single atoms. We can say what will happen if it is struck by a photon or electron, and we can say how it can bind with other atoms. We feel quantum effects all the time. In just reading this text, your eye is detecting individual photons.
The category of strange things we do not understand includes the origin of the universe and the nature of the “dark energy” that pervades the cosmos. Over the last 40 years, physicists have realized that various universal parameters, like the mass of the electron (a type of subatomic particle) and the strength of the nuclear force (the force that holds the subatomic particles together within the centers of atoms), appear to be precisely calibrated. That is, if these parameters were a little larger or a little smaller than they actually are, the complex molecules needed for life could never have formed. Presumably, the values of these parameters were set at the origin of the universe. Fifteen years ago, astronomers discovered a previously unknown and still unexplained cosmic energy that fills the universe and acts as an antigravity-like force, pushing the galaxies apart. The density of this dark energy also appears to be extraordinarily fine-tuned. A little smaller or a little larger, and the life-giving stars would never have formed.
We know a lot about the nature of dark energy. We know the pressure and the density, we know that it is appears to be uniform (and Lorentz invariant) thru-out the universe, we know its history since the big bang, and we know how it continues to expand. Or at least we think that we know. And the dark energy is not finely tuned. If it were, then it would have been discovered much more than 15 years ago, as it would have been a consequence of the existence of stars.
He goes on to propose a variety of revolutionary ideas to codify further his notion of “real time.” In one, he suggests that every atom in the universe is causally connected to every other atom in the universe, no matter how many light-years away. According to his notion, the failure of standard quantum mechanics to predict the behavior of individual atoms arises from the fact that it does not take into account the vast numbers of interconnections extending across the universe. Furthermore, this picture of the cosmos requires an absolute time (in violation of relativity), which he calls “preferred global time.”

One of Smolin’s most astonishing ideas is something he calls the “principle of precedence,” that repeated measurements of a particular phenomenon yield the same outcomes not because the phenomenon is subject to a law of nature but simply because the phenomenon has occurred in the past. “Such a principle,” Smolin writes, “would explain all the instances in which determinism by laws work but without forbidding new measurements to yield new outcomes, not predictable from knowledge of the past.” In Smolin’s view such unconstrained outcomes are necessary for “real” time.
This is kooky. I have not seen the book, so I don't know if it is as bad as it sounds.

1 comment:

  1. Because the probability density of Quantum Mechanics (QM) implies a "particle" can be found in any region of space, no matter how small, QM effectively states that electrons and protons are mathematical points. In fact, QM was invented to somehow give electrons and protons wave like properties, because the Physics community were already treating electrons and protons as point particles. The fact that point charges have infinite self energy and no physical explanation for angular momentum, magnetic spin or energy exchange (radiation) has never bothered the Physics commuinty.

    The reason why electrons and protons had to be treated as points was because calculating the dynamics of two self interacting 3-dim charges interacting with each other is impossible without a very fast computer. Another reason was a 3-dim charge would fly apart (explode) due to electrostatic force, and this was not solved until the Parson model of the spinning charge electron came out. By then, QM and Relativity were invented to patch over most of the short comings of the 0-dim theory, and too many well tenured careers would have been destroyed by switching to a 3-dim theory.

    Fortunately, there are folks like, who are more interested in advancing truth than in parroting the dogmatic comic book farce of so called Modern Physics, like infinite universes, dark matter and energy, Higg's Boson, etc... .