Yuri Arcurs/Alamy
THE first thing you need to know is that virtual particles, which are impossible to avoid if you want to understand how the fundamental forces of nature animate matter, aren’t really particles at all. “The language makes people misunderstand,” says Matt Strassler, a theoretical physicist at Harvard University. The second is that they might not be proper physical constituents of the universe.
Let’s start with some basics. According to quantum theory, our best description of the subatomic realm, particles aren’t the infinitesimal snooker balls we tend to imagine, but excitations in underlying quantum fields. The Higgs boson is a spike in the underlying Higgs field, for instance, and electrons are spikes in the electromagnetic field.
These fields permeate the entire universe, but we can’t observe them directly. What we see are particles – clear disturbances in a field that persist over time and interact with other, similar disturbances to produce more particles.
Virtual particles are more subtle. So subtle, in fact, that although they can be thought of as disturbances in underlying fields, they don’t persist for long – and can’t be directly detected.
This is where things get confusing, because virtual particles do appear to affect the properties and behaviour of other particles in measurable ways. They seem to be emitted and absorbed by real particles when those particles interact, which is why we rely on virtual particles for our understanding of how three of the known fundamental forces – electromagnetism and the strong and weak nuclear forces – work.
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