The nuclear force

The nuclear force holds atomic nuclei together. When protons and neutrons are a femtometre apart, the nuclear force between them is powerfully attractive. If you could turn this powerfully attractive force off, an atomic nucleus would explode into a spray of protons and neutrons. That’s because there’s an electromagnetic force between the protons, and it’s powerfully repulsive. In stable nuclei, the forces are in balance. But as Rod Nave says on his most excellent hyperphysics website, when the balance is broken the resultant radioactivity yields particles…

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The neutron

There’s a nice potted history of the discovery of the neutron on the Nobel website. It mentions the great Ernie Rutherford who discovered the proton in 1917. He knew all about Prout's hypothesis wherein the atomic weights of various elements were integer multiples of the atomic weight of hydrogen. However Rutherford also knew that the atomic number, the number of protons, was circa half the atomic weight. So in 1920 he suggested that this disparity was due to neutral particles called neutrons. The evidence of beta…

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Electroweak theory

The weak interaction is said to be responsible for beta decay, muon decay, and some other decays. For example it’s said to be responsible for charged pion decay, but not for the more rapid neutral pion decay. That’s said to be caused by electromagnetism. However the electroweak interaction is said to be a unification of the weak interaction with electro-magnetism, and thus is said to cover all pion decays. The beginnings of unification As to when this unification began, it’s hard to say. Some might say…

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A partial history of the weak interaction

The weak interaction is said to be responsible for beta decay, where a neutron decays into a proton, an electron, and an antineutrino. All four of these particles are said to be fermions. Fermions are of course named after Enrico Fermi, who proposed what’s now known as the Fermi interaction. That was in his 1933 paper Attempt at a theory of β rays. It was famously rejected by Nature, then published in both Italian and German in 1934. The Fermi Interaction The Fermi Interaction is “the…

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Electromagnetic gauge theory

The standard model of particle physics is said to be a gauge theory. It’s made up of different sectors, including the electroweak sector which is said to be a Yang-Mills gauge theory. The Encyclopaedia Britannica electroweak theory article says it “arose principally out of attempts to produce a self-consistent gauge theory for the weak force, in analogy with quantum electrodynamics”. Quantum electrodynamics is the theory that says the electron is a point-particle, that electrons and protons interact by throwing photons at one another, and that photons…

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The mystery of mass is a myth

When you look around on the internet, you can find a whole host of articles about the mystery of mass. For example there’s a Guardian piece by Ian Sample, who says the origin of mass is “one of the most intriguing mysteries of nature”. Or there’s Concepts of Mass by Max Jammer, who says ”the notion of mass, although fundamental to physics, is still shrouded in mystery”. There’s also the ATLAS article by Michael Chanowitz, who talks about uncovering “the deep mystery of the origin of…

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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 do you. Linear and rotational force Moreover the interaction between these fields doesn’t…

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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

To understand how a magnet works, you need to understand that the electron doesn’t have an electric field or a magnetic field, it has an electromagnetic field. In fact it is electromagnetic field. We made it in gamma-gamma pair production, such that a 511keV electromagnetic wave is configured as a spin ½ standing wave. Hence the wave nature of matter. When you wrap a sinusoidal electro-magnetic field variation into a twisted double loop, the minimum and maximum field variation combine, along with all points in between,…

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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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