Physics at a time of uncertainty

 

Physics at a time of uncertainty

I nearly entitled this post “The death of Susy” for reasons which will become apparent but I rejected it as out of keeping with the serious tenor of this contribution. Physics is the part of science that deals with the material world and of course a great deal is understood and certain. Physicists have long been interested in the fundamental building blocks of matter. Study of the atom has shown it to be made up of different parts. These parts were gradually fitted together during the latter part of the 20^th century. The generally accepted version of these parts is known as the Standard model.

The Large Hadron Collider ( LHC )  is a massive atom splitter occupying a 27 mile tunnel at the French/Swiss border. Early on in its career the LHC was instrumental in the discovery of the Higgs boson, a particle predicted 50 years ago by theoretical physicist Peter Higgs. This was highly satisfactory as it suggested the Standard model was very much along the right lines.

However a range of other particles was also predicted as larger, heavier versions of the variety of known particles. This was expected to explain the puzzle of dark matter and to connect with gravity. The Standard model explains three basic forces but doesn’t explain gravity, a vastly weaker force. These expected particles were called supersymmetric particles and the whole theory supersymmetry or Susy for short. No such particles were found which has led to much head scratching.

A great deal of the investigation of these phenomena is mathematical. No Susy meant also that doubt was cast on the mathematics of string theory. This latter posits that matter at its most fundamental level is made up of vibrating strings in a 10 or 11 dimensional universe. String theory also suggests that 6 or 7 of these dimensions are rolled up so small that they don’t affect the 4 dimensions of space and time we normally experience. Very weird!

This problem demands further investigation and several mathematical theories have been advanced. There are some anomalies which may give a way forward. In the past it has often been trying for an explanation of small anomalies from generally accepted theories which has resulted in major advances.

There is a more basic issue with looking at sub atomic particles. This simply put is that quantum theory which is such a good explanation of small things up to hundred of atoms doesn’t mix with the best explanation of large scale phenomena in relativity theory.

Quantum theory is strange. Essentially it says matter is both a particle and a wave at the same time. Mathematically the wave is described by a wave function which essentially gives the probability that a particle will be in a particular position at a particular time. For a chemist like me concerned with the electrons around an atom, often shown a bit like a miniature solar system this means that the electron is not at a fixed point but rather as a cloud around the nucleus. All we know is the probability it will be in a particular position. This uncertainty continues until something happens to fix its position ( to decohere in the jargon )

The infamous thought experiment often quoted is ascribed to Schrodinger of a cat in a box. Personally I don’t find it helpful but it is quoted in almost every effort at a simple explanation. The outside observer knows the quantum cat is both alive and dead. Opening the box decoheres the cat and a result is observed as either alive or dead

It might be protested that quantum theory can’t be right. However it passes every test we can construct and it’s application has led to many electronic gadgets we use every day. At present there is no resolution of the composition of dark matter or of relativity vs quantum mechanics.