Electron spin

Something is rotten in the state of QED

Check out something is rotten in the state of QED. It’s a paper by Oliver Consa, who has done some excellent detective work on the history of quantum electrodynamics (QED). He has delved deep into the claims that QED is the most precise theory ever, and what he’s come up with is grim: Consa says the much-touted precision of QED is based on measurements of the electron g-factor, but that “this value was obtained using illegitimate mathematical traps, manipulations and tricks”. I think he’s right. I…

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Quantum computing and the quantum quacks

I have a computer science degree. I work in IT, and have done so for many years. In that period "classical" computers have advanced by leaps and bounds. I remember teletypes and paper tape, and punched cards too. I also remember when a top-notch disk drive was the size of a washing machine and the cost of a car. It provided a miserly 10 megabytes of storage. My disk drive today is the size of my wallet and cost £46.99. It provides a terabyte of storage.…

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What charge is

The electron doesn’t have an electric field, it has an electromagnetic field. If you’re a positron and I set you down near a motionless electron, you will move linearly towards it, and it will move linearly towards you. So you might think the electron has a radial electric field, which results in a linear electric force. But it doesn’t. That linear force is there because the electron has an electromagnetic field, and so does the positron. Linear and rotational force Moreover the interaction between these fields…

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Why magnetic monopoles do not exist

There’s a lot of articles about magnetic monopoles. See this for example: the hunt for magnetism’s elementary particle begins. It dates from 2016, and it’s by Avaneesh Pandey. He says this: “magnets, for reasons we still do not understand, seem to exist only in the form of dipoles - ones with a north and a south end. Break a bar of magnet into two, and you still do not get a magnetic monopole. Instead, you now have two smaller magnets, each with its north and south…

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How a magnet works

There's a rather interesting Discover magazine article called Three Words That Could Overthrow Physics: “What Is Magnetism?”. It was written by Bruno Maddox in 2008. The subtitle is "The standard model still doesn't describe magnets' spooky action at a distance". Maddox was on holiday reading Electronics for Dummies when he realised that he didn't how a magnet works. He said this: "I set out on what I assumed would be a minutes-long odyssey to understand the phenomenon. Seventy-one days later, I am here with astonishing findings.…

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The screw nature of electromagnetism

If you’ve ever read Maxwell’s On Physical Lines of Force, you may have noticed this: “a motion of translation along an axis cannot produce a rotation about that axis unless it meets with some special mechanism, like that of a screw”. Maxwell was referring to what I can only describe as the screw nature of electromagnetism. If you have a pump-action screwdriver you’ll appreciate that linear force is converted into rotational force. That’s like an electric motor: current flows through the wire, and the motor turns.…

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The positron

The positron is usually described as a fundamental or elementary particle. That doesn’t tell you much, but when you look for more information, it’s rather scant. You soon learn that the positron  has a mass of 9.109 x 10-31 kg or 511keV/c². You learn that it has a charge of 1.602 x 10−19 Coulombs or +1e, the e being elementary charge. You also learn that it has spin ½. However you don’t learn much else. Particularly since the particle data group doesn’t have a listing for…

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Quantum electrodynamics in the 1930s

Quantum electrodynamics or QED is said to be the quantum field theory or QFT which gives “a complete account of matter and light interaction”. Some say it was developed by Sin-Itiro Tomonaga, Julian Schwinger, and Richard Feynman in the 1940s: Image from Rod Nave’s hyperphysics But some say it started with Pascual Jordan in 1925, some say it started with Dirac in 1927, and some say it started with Heisenberg and Pauli’s “canonical” papers of 1929 and 1930. In the history of QFT Meinard Kuhlmann says…

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Quantum electrodynamics in the 1920s

Quantum electrodynamics is often shortened to QED. As for what it is exactly, I find it difficult to say. Wikipedia says it’s the relativistic quantum field theory of electrodynamics, and gives “a complete account of matter and light interaction”. But that’s not enough. The Encyclopaedia Britannica says it’s a quantum field theory which “describes mathematically not only all interactions of light with matter but also those of charged particles with one another”. That’s not enough either. Particularly since it’s defining QED in terms of other things…

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A detective story

So why isn't the future what it used to be? I think it’s something of a detective story, one where you have to look back at the history. In 1831 Michael Faraday was doing his ground-breaking experiments, showing how electricity and magnetism were interrelated. Then in 1865 James Clerk Maxwell developed the theory, and in 1880 we had light bulbs courtesy of Joseph Swan and Thomas Edison. In 1905 Einstein gave us E=mc², saying there was an awful lot of energy in matter. Then in 1934…

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