The Strange Charm of Quantum Electrodynamics

Quantum Electrodynamics (QED) is a model in physics that describes the very small.

At very small scales, reality is built up like Lego. Atom nuclei are made of protons and neutrons, which in turn are made of quarks. Imagine 3 small lego bricks – say 2 blues and a red – and join them together to form a larger “proton block.” Or a “neutron block” formed by 2 red and 1 blue. The larger blocks have an individual identity and a combined identity.

Electrons however, are believed to be fundamental (in this analogy they would be small bricks that don’t connect to anything). This analogy doesn’t give an idea of relative size, but can be used to create an image of what is occurring at very small scales.

Small bricks can be combined in different combinations to make different bigger blocks. Particles are the same. Credit: WikiCommons

Physicists are literally creative.

Now, these quarks would obviously be named so that their significance was evident. Obviously. So, the 6 flavours (different types with slightly altered properties) of quarks are called:

First Generation:

  1. Up
  2. Down

Second Generation:

  1. Strange
  2. Charm

Third Generation:

  1. Top
  2. Bottom

Excited…? Well, not so much.

Each flavour has different combinations of altered properties/Ice-Cream is exciting. Credit: Dace Praulins WikiCommons

Spin me right round.

Let’s take a real quick detour so I can explain the spin of a particle. Unlike a lot of quantum mechanics, there’s not an everyday comparison – it’s not, for example, a description of how fast the particle spins. It’s an anachronism from when we had a lesser understanding of the universe.

However, it follows some of the mathematical descriptions of angular momentum (like linear momentum, but how the object is spinning), and so the name remains.

Anything that rotates has angular momentum – even if you hate that object. Credit: Guillaume Carta WikiCommons

You can have spin up or spin down with a magnitude attached – like a vector. While a particle can switch between spin up and down, the magnitude will never change.

Up and Down/Physicists are very literal.

As you might expect, the Up and Down quarks are named because they are intrinsically spin up and spin down – always. (Of course the other quarks have spin up and spin down, but Up and Down were named first).

Up and Down are the only stable quarks; the more massive flavours quickly decay into lighter Up and Down quarks.

Some of the mass transforms into energy, making the new particles lighter. Credit: WikiCommons

Using Legos, the outermost shell of colour would fall off the more massive quarks to reveal red or blue (Up and Down quarks) underneath. How the outside world defines them has changed and their properties change too.

That’s strange.

The Strange quark was named third and was first discovered in a Kaon – a particle that exists for a “strangely” long time (that’s against a compatible particle; a Kaon has a mean lifetime of only 10-8 s).

Charming.

Charm has no real meaning in the physical sense. Most believe it was named on a whim – the math worked like a charm.

The loss of Beauty and Truth.   

The Top and Bottom quarks were almost called ‘Truth’ and ‘Beauty,’ but were changed after scientists decided that the name was too ridiculous.The names where finally chosen to be analogous to the Up and Down quarks and kept the ‘T’ and ‘B‘ as reference. It suggests that Physicists can only create very literal names!

The Top quark is the heaviest of the six quarks and would weigh as much as an entire gold atom. For comparison, it takes 2 Up and 1 Down quarks to form just one proton.

An alternative view on a proton. Credit: WikiCommons

They’re real, I swear.

Quarks are never found in isolation due to their unique binding properties, and their attributes have been inferred from the particles they make up.

However, they can be modelled to a high degree of accuracy using QED.

If you are able to observe a solitary quark, please email me. I would love a Nobel Prize.

#Goals. Credit: WikiCommons

6 Responses to “The Strange Charm of Quantum Electrodynamics”

  1. Ruby Lieber says:

    Great post Will! I absolutely loved your Lego analogy, it was a really good way of describing something so complicated. It is a shame they didn’t stick with truth and beauty, it would have made the names a lot easier to remember! Your final post has improved so much since the first draft, I really think you have found your writing style! Keep it up!

  2. Jamie says:

    Will, all my attempts to understand quarks have been futile – until today. Like Richard, I loved the lego metaphor and found it helpful in terms of putting things into perspective. Using pictures and explaining the history of naming quarks also made it much more interesting, and much easier to get through than the blocks of text on Wikipedia (for me, at least!). The basic aspects of quarks are definitely not as intimidating as they appeared to be. Thanks so much. What an amazing piece of work!

  3. Hockey says:

    Nice work Will!
    Upon perusing the words “Quantum Electrodynamics” I was reluctant to read this article. The relation to fidget spinners, ice cream and lego kept me engaged and introduced me to a topic far outside my area of expertise. Thank you!

  4. Matthew says:

    The sub headings, the pictures you used and the way you explain things makes your post super chill and entertaining to read. I left reading that, thinking i wanted to read more into the binding properties and why we can’t observe the quarks alone but i didn’t get far at all! Thanks for the sweet insight into a really hard topic.

  5. Will McDonald says:

    Thanks Richard, that’s exactly what I was aiming for. It’s such a complicated topic that I really wanted to show readers there was still approachable avenues to talk about it!

  6. Richard Proudlove says:

    Hi Will. Fantastic! A blog that combines two things I love….Physics and Lego!! As with all things Physics it will warrant a second, third, fourth..one hundredth reading before I have any chance of thinking that I might be starting to understand it, and I will still be deluding myself (even Prof Brian Cox says that he did not really understand General Relativity until he was taught it for the third time). Thanks for a great attempt to explain something complex in simple terms.