ThirdThoughts

Third Thoughts (Steven Weinberg)

  • In the ancient world astronomy reached a much higher level of accuracy and sophistication than any other natural science. One obvious reason is that astronomical phenomena are much simpler and easier to study than the things we can observe on the earths surface.
  • Discovery around 430 BC using gnomom (a pole in the ground) that the solstices and equinoxes have slightly different lengths. This ruled out the possibility that the sun travels around the earth (or the earth around the sun) with constant velocity.
  • The SM is required to be made of renormalizible interactions (actually now think the others can also be there but suppressed by powers of a large mass scale). This simplicity gives a natural explanation of the mysterious approximate symmetries of the strong interaction, eg: isospin conservation.
  • EFTs are not fundamental, they cannot be assumed to be particularly simple. So all possible terms consistent with assumed symmetries are considered independently.
  • Quantum gravity has to be treated as an EFT. The problem with Quantum Gravity is not the infinities, but that the theory loses all predictive power at high energies.
  • "I fully expect that sometime in the coming century we will find suppressed baryon non-conserving processes, so that proton decay will become a major concern of particle physicists.
  • Whiggery has a rightful place in the history of science. In science we really can say who was right. History
  • Much of the history of science has been a matter of learning which question should and should not be asked.
  • The evolution over many centuries of modern science is a great story, as important and interesting as anything else in the history of human civilization. History
  • Since the downfall of the phlogiston theory of fire and the caloric theory of heat in the 19C, there has been no generally accepted theory in the exact sciences that has turned out to be simply wrong. History
  • A particle is simply a physical system that has no continuous degrees of freedom except for its total momentum.
  • The idea that all matter consists of just two types of elementary particles was assumed to be true in a way that is hard to understand today. eg: when neutrons were discovered they were assumed to be deeply bound states of protons and electrons.
  • We do not know in advance what are the right questions to ask, and we often do not find out until we are close to an answer.
  • Free will is nothing other than the conscious experience of deciding what to do. This experience is not invalidated by the reflection that physical laws made it inevitable that I would want to make these decisions. FreeWill
  • So we had a double mystery, What causes the observed violation of the eight-fold way symmetry and of mirror symmetry and matter-anti-matter symmetry? Theorists offered several possible answers, this turned out to be the wrong question to ask. It turned out that the SM obeys certain symmetries that are accidental, in the sense that they are not exact local symmetries on which the SM is based, they are automatic consequences of the SM. Instead of asking what breaks mirror symmetry we should have been asking why there should be any mirror symmetry or matter-antimatter symmetry at all. PhilosophyOfPhysics
  • If protons do decay, the universe will eventually contain only electrons and lighter particles like neutrinos and photons. Matter as we know it will be gone.
  • The electron waves are not waves of electronic matter, in the way that ocean waves are waves of water. Rather, the electron waves are waves of probability. Quantum Mechanics
  • It is a bad sign that those physicists today who are most comfortable with QM do not agree with each other about what it all means. Quantum Mechanics
  • The trouble with QM is not that it involves probabilities. The trouble is that in QM the way that wave functions change with time is governed by an equation, that does not involve probabilities. If we regard the whole process of measurement as being governed by the equations of QM, and these equations are perfectly deterministic, how do probabilities get into QM? Quantum Mechanics
  • The special treatment of investment income should be eliminated. It distorts the balance between consumption and investment, a balance that ought to be set (at least according to the economic philosophy of conservatives) by free market forces. In the present state of our economy, it is consumers that are the real job creators. Politics
  • The real challenge in gaining independence of earth, is not getting people to Mars, but freeing them from the need of support form Earth, we would start with Antarctica.

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