- Paul Dirac born in Bristol, England in 1902 was probably the second greatest theoretical physicists short of Albert Einstein. He went to public schools, got an electrical engineering degree (1921), switched to mathematics (1923) and got a Ph.D. from Cambridge in mathematical physics.
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- He wrote dozens of technical papers and won a Nobel Prize ins 1933. This review is an article he published in Scientific American magazine on the “Evolution of Physics”.
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- Physics prior to Isaac Newton was essentially 2 dimensional, the plane that we walk around on and up-and-down motion. Newton brought the picture to a 3-dimensional symmetry by adding the gravitational forces.
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- Einstein brought it to 4-dimensions with the concept of space-time. His 4-dimensions were not completely symmetrical because of the arrow of time. When he wrote the equations for invariant distances, “s”, with respect to time, time had the opposite sign of 3-dimensional space.
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------------------ s^2 = c^2 - x^2 - y^2 - z^2
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---------------Differentiate with respect to time, to get the rate of change of space with respect to time:
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------------- ds^2 = c^2dt^2 - dx^2 - dy^2 - dz^2
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-------------- s = invariant distance
-------------- c = the speed of light
------------- x, y, and z = 3-dimensional space.
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-------------- ( c^2dt^2 ) does not have the same sigh as the 3 spatial directions.
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- To get to 4-dimensions he needed to take a 3-dimensional section and give it a frame. At a later time we have a different 3-dimensional section in a later frame.
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- Quantum theory complicated this picture further by requiring us to take the process of observation into account.
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- Then Einstein added his General Theory of Relativity and complicated things even further. He supposed that the space of physics is curved not the “flat space” that Newton worked with. General relativity curved 4-dimensional space-time.
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- Physics today is trying to apply quantum ideas to these gravitational equations. A gravitational field is a tensor field. Quantum Theory is the discussion of very small things. It first appeared when Planck discovered that the energy of electromagnetic waves can exist only in multiple of a certain unit, the Planck Constant of Action times the frequency of the wave, E = h*f.
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- This step in physics was necessary to explain the law of blackbody radiation . Einstein discovered the same unit of energy occurring in the photoelectric effect.
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- The next new picture in physics was Bohr’s picture of the atom. He had electrons moving about the nucleus in certain will-defined orbits able to jump from one orbit to another.
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- In 1925 Heisenberg and Schrodinger introduced Quantum Mechanics.. They were able to explain experimental data with matrix mechanics. De Broglie introduced the duality of particles and waves . Schrodinger was able to describe atomic processes with his wave equation. His equation initially was missing the knowledge that the electron’s had spin. Dirac concluded that it was more important to have “beauty” in one’s equations that to have them fit experiment. Later spin was added and the data matched the calculations.
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- Quantum Mechanics forced physics to give up the deterministic picture. The theory does not predict with certainty rather it gives a probability of occurrence of events.
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- The present stage of physical theory is a mere stepping stone toward the better stage in its evolution.
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- Quantum Theory gives wonderful agreement with observation. But not all the time, it is still not prefect. We do not make progress going over the successes again and again. whereas going over the difficulties can bring progress.
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- Quantum Theory does not work when we push the laws to extreme conditions, high energies and small distances ( Blackholes and Big Bangs).
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- One fundamental Constant of Nature left unexplained is the Fine Structure Constant. Natural constants of the charge for the electron, Planck’s Constant of Action, and the velocity of light create a ratio that has no units:
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----------------------- (h /2*pi) * c / e^2 = 137
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- There is no theory of why the result is 137 yet it is fundamental to the function of atoms. Atoms do not work if it is any other value. Dirac predicted that “ e” and “ c “ are truly fundamental constants but that someday “ h/2*pi” will be derived from the other 2. “h/2pi” is also in the uncertainty relationship between knowing position and momentum of an atomic particle.
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- When Quantum Theory tries to merge with Relativity Theory quantities that ought to be finite are actually infinite, integrals diverge instead of converging. “ Renormalization” is a method invented y physics to insert experimental data into calculating equations to get rid of the infinities. Physicists get good agreement with experiment despite the illogical method. Dirac would say it is not beautiful therefore not mathematically sound.
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- God is a mathematician of a very high order. He used very advance mathematics in constructing the Universe. Physics needs to discover more of his equations then the physical pictures will appear behind them.
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(1) Dirac worked out equations that requires there to be an electron and an anti-electron. The anti-particle had to be the exactly same particle except the opposite electric charge. Dirac discovered anti-matter in his math before it was discovered in the laboratories.
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(2) He retired as professor of physics at Florida State University, Tallahassee.
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(3) Dirac grew up with a father that spoke French and a mother that spoke English. His father would discipline him whenever he made a mistake with the French language. Therefore he tended to not speak at all. Why us one word when none will do
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