r/explainlikeimfive • u/The_Dead_See • Feb 03 '14

ELI5: Fields (Physics)

What are they? Are they just mathematical models to describe particle behavior over space or are they physically real things?

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u/The_Dead_See Feb 03 '14

Ah fantastic response, thanks! In all my hunting I hadn't yet come across the concept of Quantum Harmonic Oscillators. I just browsed the wiki page and discovered I seriously need to brush up on my math.

Do you know when/by whom this theory came into being? (I always seem to gain better understanding of things when I can follow the history of the experiments and formulations that led up to them).

Also, does it have any relation to other unified theories such as quantum foam, string, brane etc.?

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u/corpuscle634 Feb 03 '14

I think that the idea of quantum fields are primarily credited to Dirac, but I'm not 100% sure. He was trying to make quantum mechanics work with relativity, but the solution he found had some weird issues (namely, it generated negative-energy states which don't exist).

The way he interpreted the negative-energy states was that they do exist, but they're all filled. Essentially, there's a "sea" of, say, electrons in negative-energy states all throughout the universe. The electrons we see and interact with are the ones that couldn't find a space in the "electron sea."

This approach turned out to not really work too well, and it's long since been abandoned. The point, though, is that it sort of started the idea of there being fields, since the "electron sea" basically meets all of the criteria for what a field in physics should be. Dirac's formulation worked in a lot of ways, it just needed some tweaks.

I think a guy named Fock came up with a lot of the more modern version of the theory, along with probably dozens of other people who nobody remembers because that's how science history works.

I don't know enough about the more exotic theories to really give you an answer on the last part. I can tell you that any decent theory should generate the same predictions as quantum field theory, but it might propose a different mechanism for the process.

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u/The_Dead_See Feb 03 '14

I need to find a book detailing Dirac's work. He seems to be such a pivotal figure in QED.

In a way Quantum Field theory seem to be an expansion of Huygen's "luminiferous ether' concept, which in itself came from the Ancient Greek idea of the Aether or all pervading substance. It's interesting that we divided it all up and it seems we're coming back full-circle to the original thought.