Visar inlägg med etikett logical fallacy. Visa alla inlägg
Visar inlägg med etikett logical fallacy. Visa alla inlägg

tisdag 16 september 2025

Logical Fallacy of Modern Physics?

Aristotle would have been very surprised to see that modern physics in the form of Standard Quantum Mechanics StdQM is filled with his logical fallacy of "affirming the consequent" or "confirming an assumption by observing a consequence". 

Examples: 

  • If there was a Big Bang, then a Universe would have been come into existence. We observe that a Universe exists, and conclude there was a Big Bang. 
  • If the Higgs boson exists, there will be blip on a computer screen. We observe a blip and conclude that the Higgs boson is real physics worthy of a Nobel Prize.

The incorrect form is: If A implies B and B is observed to be true, then A is true. Cannot be used as verification of A.

The correct form is: If A implies B and B is observed to be false, then A is false. Can be used as falsification of A.

But we have been confronted with the incorrect form so many times that we are immune to the logic fallacy of "affirming the consequent". 

The motivation using this logical fallacy over and over, is that the assumptions of StdQM cannot themselves be checked because of their evasive physical nature, and so the only possibility has been to observe some observable consequence to see if it is the case, and then use that as evidence that the assumption is satisfied. 

This is not so in classical mechanics, where the basic laws in the form of Newton's law of gravitation or Coulomb's law of electrostatics can be directly checked. Then there is no need to resort to logical fallacy and the science has a better chance to capture reality. 

Is it then true that the basic assumptions of Schrödinger's Equation SE for the Hydrogen atom cannot be checked? No, they can be directly be checked because SE for the Hydrogen atom is based on

  1. Coulomb's Law
  2. Kinetic energy in the form of compression energy of charge density. 
Both can be checked directly as in classical mechanics. It means that after verifying 1-2 we can predict the spectrum of Hydrogen to be exactly that observed. What could happen is that we observe some "fine structure" of the spectrum and we can then conclude that there is something missing in the set up for 1-2 such as non-zero magnetic field. 

The trouble with StdQM is that the generalisation to atoms with more than one electron leaves the setting of 1-2 and adds assumptions which cannot be directly verified because they concern a multi-d wave function living in some Hilbert space, which has no physical meaning. What remains is to check consequences of the presence of such a wave function and use that as confirmation of correctness of the added assumptions, then resorting to the logical fallacy.

Now there is a version of quantum mechanics named RealQM which is based solely on 1-2, in principle,  and so the assumptions of RealQM can be checked, at least in principle, and so RealQM takes the same form as classical mechanics and so does not need to resort to incorrect logic. Maybe quickly check it out?


lördag 28 maj 2016

Aristotle's Logical Fallacy of Affirming the Consequent in Physics


One can find many examples in physics, both classical and modern, of Aristotle's logical fallacy of Affirming the Consequent (confirming an assumption by observing a consequence of the assumption):
  1. Assume the Earth rests on 4 turtles, which keeps the Earth from "falling down". Observe that the Earth does not "fall down". Conclude that the Earth rests on 4 turtles.
  2. Observe a photoelectric effect in accordance with a simple (in Einstein's terminology "heuristic") argument assuming light can be thought of as a stream of particles named "photons" . Conclude that light is a stream of particles named photons. 
  3. Assume light is affected by gravitation according the general theory of relativity as described by Einstein's equations. Observe apparent slight bending of light as it passes near the Sun in accordance with an extremely simplified use of Einstein's equations. Conclude universal validity of Einstein's equations.
  4. Observe lift of a wing profile in accordance with a prediction from potential flow modified by large scale circulation around the wing. Conclude that there is large scale circulation around the wing. 
  5. Assume that predictions from solving Schrödinger's equation always are in perfect agreement with observation. Observe good agreement in some special cases for which the Schrödinger equation happens to be solvable, like in the case of Hydrogen with one electron. Conclude universal validity of Schrödinger's equation, in particular for atoms with many electrons for which solutions cannot be computed with assessment of accuracy.
  6. Assume there was a Big Bang and observe a distribution of galaxy positions/velocities, which is very very roughly in accordance with the assumption of a Big Bang. Conclude that there was a Big Bang.
  7. Assume that doubled CO2 in the atmosphere from burning of fossil fuel will cause catastrophic global warming of 2.5 - 6 C. Observe global warming of 1 C since 1870. Conclude that doubled CO2 in the atmosphere from burning of fossil fuel will cause catastrophic global warming of 4 - 8 C.
  8. Assume that two massive black holes merged about 1.3 billion years ago and thereby sent a shudder through the universe as ripples in the fabric of space and time called gravitational waves and five months ago washed past Earth and stretched space making the entire Earth expand and contract by 1/100,000 of a nanometer, about the width of an atomic nucleus. Observe a wiggle of an atom in an instrument and conclude that two massive black holes merged about 1.3 billion years ago which sent a shudder through the universe as ripples in the fabric of space and time called gravitational waves...
  9. Observe experimental agreement of the anomalous magnetic dipole moment of the electron within 10 decimals to a prediction by Quantum Electro Dynamics (QED). Conclude that QED is universally valid for any number of electrons as the most accurate theory of physics. Note that the extremely high accuracy for the specific case of the anomalous magnetic dipole moment of the electron, compensates for the impossibility of testing in more general cases,  because the equations of QED are even more impossible to solve with assessment of accuracy than Schrödinger's equation.
The logic fallacy is so widely practiced that for many it may be difficult to see the arguments as fallacies. Test yourself!

PS1. Observe that if a theoretical prediction agrees with observation to a very high precision, as is the case concerning the Equivalence Principle stating equality of inertial and gravitational (heavy) mass, then it is possible that what you are testing experimentally in fact is the validity of a definition, like testing experimentally if there are 100 centimeters on a meter (which would be absurd).

PS2 Books on quantum mechanics usually claim the there is no experiment showing any discrepancy whatsoever with solutions of the Schrödinger equation (in the proper setting), which is strong evidence that the Schrödinger equation gives an exact  description of all of atom physics (in a proper setting). The credibility of this argument is weakened by the fact that solutions can be computed only in very simple cases.