L-shaped contrails

Sorry I haven't posted much lately. I've been run off my feet with work. Like that woman at the end of Twelve Monkeys, I'm in insurance, and work is pressing. But anyhow, very briefly, I wanted to show you something I saw yesterday evening: L- shaped contrails. At least that's what they looked like: There appears to be two, one lower, one higher. Here's another picture I took a few seconds later: I was in Poole looking west, at circa 18:53 GMT.  Interesting, that! NEXT

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Why clocks go slower when they’re lower

This is in response to a query from Jonas K. See my post you can lead a horse to water, and take a look at the comments. OK, I’ll start again from the beginning, Jonas, you're blue: Textbook optical clocks of the bouncing-photons-kind go slower when lower in a gravitational field, yes. So do Cesium-based atomic clocks, by exactly the same amount. Why is that? It’s because a Cesium-based atomic clock has an electromagnetic nature. Take a look at the NIST caesium fountain clock: Image courtesy…

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A worble embracing itself

See the 2014 essay on the fluid dynamics of James Clerk Maxwell by Henry Keith Moffat. He referred to Maxwell’s 1867 letter to Peter Guthrie Tait. That’s where Maxwell said the simplest indivisible whorl “is either two embracing worbles or a worble embracing itself”. A worble embracing itself has a ring to it. I think it’s one of the secrets of the universe myself. Because John Williamson and Martin van der Mark were talking about something similar in their 1997 paper Is the electron a photon…

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The TOE that Maxwell missed

If you’ve ever read James Clerk Maxwell’s 1865 paper A Dynamical Theory of the Electromagnetic Field, you might have noticed his Note on the Attraction of Gravitation. It’s at the end of part IV. Maxwell ends up saying energy is essentially positive, and that “the presence of dense bodies influences the medium so as to diminish this energy wherever there is a resultant attraction”. Then he said this: “As I am unable to understand in what way a medium can possess such properties, I cannot go…

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A grand unified history lesson

Like I was saying last time, a major goal of physics is “to unify the various fundamental forces” in a theory that offers “a more elegant understanding of the organization of the universe”. This is called a grand unified theory or GUT if it doesn’t include gravity, and a theory of everything or TOE if it does: Image from Sten Odenwald’s astronomy cafe Personally I don’t understand why anybody doesn’t include gravity. Gravity is easy. Einstein explained most of it in his 1920 Leyden Address. A…

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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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