In June, 2014, I gave a talk at the Physics Department of the Czech Technical University in Prague. I started by asking the question “What does the electron look like?”, and I showed two pictures. The first was the familiar Rutherford picture of particles orbiting a nucleus:
and the second was a (highly simplified) picture of the electron as a field in the space around the nucleus:
Then I asked for a vote. Quite amazingly only four people in the audience chose the field picture, and no one chose the particle picture. In other words, THEY DIDN’T KNOW. So here we are, 117 years after the electron was discovered, and this highly educated group of physicists had no idea what it looks like.
Of course when the electron was discovered by J. J. Thomson, it was naturally pictured as a particle. After all, particles are easy to visualize, while the field concept, let alone a quantized field, is not an easy one to grasp. However this picture soon ran into problems that led Niels Bohr in 1913 to propose that the particles in orbit picture must be replaced by something new: undefined electron states that satisfy the following two postulates:
1. [They] possess a peculiarly, mechanically unexplainable [emphasis added] stability.
2. In contradiction to the classical EM theory, no radiation takes place from the atom in the stationary states themselves, [but] a process of transition between two stationary states can be accompanied by the emission of EM radiation.
We assert that the atom in reality is merely the… phenomenon of an electron wave captured, as it were, by the nucleus of the atom… From the point of view of wave mechanics, the [particle picture] would be merely fictitious. – E. Schrodinger
However the fact that a free electron acts like a particle could not be overcome, and so Schrodinger gave in and Quantum Mechanics emerged as a theory of particles that are described by probabilities.
A second battle occurred in 1948, when Richard Feynman and Julian Schwinger (along with Hideki Tomanaga) developed different approaches to the “renormalization” problem that plagued physics. Once again the particle view espoused by Feynman won out, in large part because his particle diagrams proved easier to work with than Schwinger’s field equations. And so two generations of physicists have been brought up on Feynman diagrams and led to believe that nature is made of particles.
In the meantime, the theory of quantized fields was perfected by Julian Schwinger:
My retreat began at Brookhaven National Laboratory in the summer of 1949… Like the silicon chip of more recent years, the Feynman diagram was bringing computation to the masses… But eventually one has to put it all together again, and then the piecemeal approach loses some of its attraction… Quantum field theory must deal with [force] fields and [matter] fields on a fully equivalent footing… Here was my challenge. – J. Schwinger
Schwinger’s final version of the theory was published between 1951 and 1954 in a series of five papers entitled “The Theory of Quantized Fields”. In his words:
It was to be the purpose of further developments of quantum mechanics that these two distinct classical concepts [particles and fields] are merged and become transcended in something that has no classical counterpart – the quantized field that is a new conception of its own, a unity that replaces the classical duality. – J. Schwinger
I believe that the main reason these masterpieces have been ignored is that many physicists found them too hard to understand. (I know one who couldn’t get past the first page.)
And so the choice is yours. You can believe that the electron is a particle, despite the many inconsistencies and absurdities, not to mention questions like how big the particles are and what are they made of. Or you can believe it is a quantum of the electron field. The choice was described this way by Robert Oerter:
Wave or particle? The answer: Both, and neither. You could think of the electron or the photon as a particle, but only if you were willing to let particles behave in the bizarre way described by Feynman: appearing again, interfering with each other and cancelling out. You could also think of it as a field, or wave, but you had to remember that the detector always registers one electron, or none – never half an electron, no matter how much the field has been split up or spread out. In the end, is the field just a calculational tool to tell you where the particle will be, or are the particles just calculational tools to tell you what the field values are? Take your pick. – R. Oerter
What Oerter neglected to say is that QFT explains why the detector always registers one electron or none: the field is quantized. The Q in QFT is very important.
So when you take your pick, dear reader, I hope you won’t choose the picture of nature that doesn’t make sense – that even its proponents call “bizarre”. I hope that, like Schwinger, Weinberg, Wilczek, Hobson (and me), you will choose a reality made of quantum fields – properties of space that are described by the equations of QFT, the most philosophically acceptable picture of nature that I can imagine.