Particle physics

The neutrino

The neutrino was proposed by Wolfgang Pauli in 1930 to account for the conservation of energy and spin angular momentum in beta decay. You can find his original letter to Lise Meitner and others on the Fermilab MicroBooNE database, along with the English translation: Pauli later said “I have done a terrible thing. I have postulated a particle that cannot be detected”. He was wrong about that. He was wrong about some other things too. He talked about a particle that travels slower than light, and…

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What the proton is not

The proton was discovered by the great Ernie Rutherford in 1917. He used alpha particles to convert nitrogen into oxygen, and in doing so detected hydrogen nuclei. He’d previously done experiments with alpha particles and hydrogen, so he was confident they were hydrogen nuclei. This confirmed William Prout's hypothesis which dated back to 1815. Prout had observed that the atomic weights of other elements were integer multiples of the atomic weight of hydrogen. So he came up with the idea that the hydrogen atom was a…

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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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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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The electron

The electron 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 electron 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. Instead you get mixed messages. Take a look at the enigmatic electron…

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How pair production works

Yes, there's a hole in the heart of quantum electrodynamics because it describes the interaction between light and matter, but not the interaction between light and light. That's the interaction that creates matter in gamma-gamma pair production. QED misses the crucial point that waves interact. Even though we've all seen waves interact, down on the beach. Imagine a big wave is coming towards you. You make a little wave with your hand and send it scooting towards the big wave: The little wave rides up and over…

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The hole in the heart of quantum electrodynamics

Pair production is the creation of a particle and its antiparticle. Some say it was first observed in 1929, but it's usually accredited to Carl Anderson in 1932. He used a cloud chamber and an electromagnet to investigate cosmic rays. He effectively split a gamma photon over an atomic nucleus to create an electron and an antielectron. He called the latter the positive electron, which was soon shortened to positron: Image from schoolphysics However whilst he realised that he’d discovered the positron, he didn’t realise that he’d performed pair…

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The photon

The photon has a wave nature, which is why we can refract and diffract light. But what sort of a wave nature? When you try to find a picture, a lot of illustrations depict the photon as some kind of wave train. Even Feynman diagrams do this. Image by bitwise, see Wikipedia commons The photon is shown as a squiggly line, sometimes with an arrowhead, something like this: ⇝. That suggests you could split a photon lengthwise and end up with two photons, each with the…

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What is a photon?

OK, so quantum electrodynamics is said to date from 1929 when it was the same thing as quantum field theory. However it immediately suffered from the “problem of infinities”. So much so that some say most workers in the field doubted its correctness, whilst others say physicists believed a conceptual change was needed. As to what, see the conceptual foundations and the philosophical aspects of renormalization theory by Tian Yu Cao and Silvan Schweber dating from 1993. They say QFT embodies a reductionist view, but “serious doubt has often been cast on the…

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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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