Foundations of physics

The Big Bang

Big Bang cosmology arguably started in 1917. Vesto Slipher had measured 21 galactic redshifts by 1917. That’s when Albert Einstein wrote his cosmological considerations paper and Willem de Sitter came up with the de Sitter universe. The next year in 1918 Erwin Schrödinger came up with his cosmic pressure. In 1922 Alexander Friedmann came up with a non-static universe. In 1924 he came up with negative and positive curvature, and Knut Lundmark came up with an expansion rate within 1% of measurements today. In 1927 Georges…

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A compressed prehistory of dark energy

In the Wikipedia dark energy article you can read how the term "dark energy" was coined by Michael Turner in 1998. This was in a paper co-authored with Dragan Huterer called prospects for probing the dark energy via supernova distance measurements. It referred to the type 1a supernovae observations made by the Supernova Cosmology Project and by the High-Z Supernova Search Team. Their observations indicated that the expansion of the universe is accelerating, which was contrary to expectations and led to Nobel prizes in 2011: Expanding…

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The nuclear disaster

The nuclear force is the force that keeps protons and neutrons together in atomic nuclei. It is often said to be due to a pion exchange proposed by Hideki Yukawa in 1935. His Nobel prize lecture Meson theory in its developments gives some background: “As pointed out by Wigner1, specific nuclear forces between two nucleons, each of which can be either in the neutron state or the proton state, must have a very short range of the order of 10-13 cm, in order to account for…

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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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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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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 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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