Why do particle physicists like spending time in fields?

When we were first preparing to launch my column for New Scientist, my editor asked me what I would like to call it. “Field notes from space-time,” I said. This title has a bit of a double entendre that might not be obvious, but was fun for me as a physicist. It is a reference to the scientific idea of taking notes while out in the field – a lab notebook of sorts. Simultaneously, it alludes to a specific concept that is very important in particle physics: the field itself.

You might think that a field is a big open space you find on a farm, but in physics it is more abstract. Essentially, a field is a mathematical relation that assigns a number to each point in space and time. The intention is to characterise some physical phenomenon at that location. For example, when you feel the pull of a fridge magnet close to a refrigerator door, there is a magnetic force working between the two. That force has a magnetic field value at each location in space that gets stronger as the distance between the magnet and the fridge shrinks.

In fact, the first time a physicist used the word “field” in this way was when 19^th-century scientist Michael Faraday was studying the magnetism of the element bismuth. While working on my new book, I read his journal entries and saw the first time he invoked the field idea, but I wondered how Faraday arrived at this language. I don’t know for certain, but my own theory is that it is related to the way in which Faraday was unusual for his time. Unlike other physicists of his era, he came from a working-class family. His parents had been born and raised in a village and came from a farming background. In other words, they were people who lived in close relationship to the land. In my mind, I imagine Faraday thinking about the invisible properties of wide-open spaces worked by families like his own.

The field idea didn’t stay in the world of magnetism. One of the most phenomenal innovations of the 20^th century was the intersection of fields with the transformative theories of quantum physics, which had already invited scientists to understand particles and waves as having a dual relationship. In other words, particles like electrons are also waves and waves like the electromagnetic field are also particles (which we call photons). Not long after the community got comfortable with the idea of wave-particle duality, it became clear that there had to be a deeper relationship between the quantum and the field.

In the process of developing a complete quantum picture of the photon, fields once again became necessary. But this time, they were quantum fields. Just as the magnetic field quantifies how much magnetic force exists at each point in space, a quantum field determines how many particles can be created or destroyed at each point in space. As a result, we say that all electrons emerge from a quantum electron field, and so on for other particles. We also suspect that dark matter, which seems to be invisible but behaves in all other ways like it is made of particles, has a similar field that we are yet to discover. The universe is full of particles emerging out of the vacuum, thanks to quantum fields. In this sense, whenever I write about anything in this column, I am writing literal field notes, from space-time.

What are you reading?

I am completely obsessed with The Manifesto of Herman Melville by Barry Sanders.

What are you watching?

I am loving the final season of Hacks.

What are you working on?

Having finished launching The Edge of Space-Time in the US, I’m now focused on the UK release!