Virtual particles: how physicists’ clever accounting trick could be behind reality

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A clever mathematical tool known as virtual particles unlocks the strange and mysterious inner workings of subatomic particles. What happens to these particles in atoms would remain unexplained without this tool. Calculations using virtual particles predict the bizarre behavior of subatomic particles with such uncanny precision that some scientists think “they must really exist.”

Virtual particles are not real – their name suggests – but if you want to understand how real particles interact with each other, they are unavoidable. They are essential tools for describing three of the forces present in nature: electromagnetismAnd the strong And weak nuclear strengths.

Real particles are bits of energy that can be “seen” or detected by appropriate instruments; this characteristic is what makes them observable or real. Virtual particles, on the other hand, are a sophisticated mathematical tool and cannot be seen. Physicist Richard Feynman invented them to describe interactions between real particles.

But many physicists are not convinced by this clear-cut distinction. Although researchers cannot detect these virtual particles, as computational tools they predict many subtle effects which ultrasensitive experiments have confirmed to a staggering 12 decimal places. This precision amounts to measuring the distance between the North and South poles with a precision greater than the width of a single hair.

This level of agreement between measurements and calculations makes virtual particles the most thoroughly tested idea in science. This forces some physicists to ask: can a mathematical tool become real?

Virtual particles are the tool physicists use to calculate how forces work in the microscopic subatomic world. Forces are real because they can be measured.

But instead of trying to calculate forces directly, physicists use an accounting system in which short-lived virtual particles carry the force. Not only do virtual particles make calculations easier, they also solve a long-standing physics problem: how does a force act in empty space?

Virtual particles exploit the natural blur of the subatomic worldwhere if these ephemeral particles live quite briefly, they can also briefly borrow their energy from empty space. The vagueness of the energy balance hide this brief imbalancewhich allows virtual particles to influence the real world.

One of the great advantages of this tool is that the mathematical operations describing the forces between particles can be visualized in diagrams. They tend to look like cartoon particle ping pong played with virtual particles. Diagrams – doubled Feynman diagrams – provide an excellent intuitive framework, but they also give virtual particles a deceptive aura of reality.

Amazingly, this virtual particle-based calculation method produces some of the most accurate predictions in all of science.

Reality check

All matter is made up of basic elements called atoms. Atoms, in turn, are made up of small positively charged particles called protons found in their hearts, surrounded by even smaller negatively charged particles called electrons.

As a teacher of physics and astronomy at Mississippi State UniversityI carry out experiments which often rely on the idea that the electrons and protons observed in our instruments interact by exchanging virtual particles. My colleagues and I recently measured the proton size very precisely, by bombarding hydrogen atoms with a beam of electrons. This measurement assumes that electrons can “sense” the proton at the center of the hydrogen atom by exchanging virtual photons: electromagnetic energy particles.

Physicists use virtual particles to calculate how two electrons repel each other, with exquisite precision. The forces involved are represented as the accumulated effect of the two electrons exchanging virtual photons.

When two metal plates are placed very close to each other in a vacuum, they attract each other: this is called Casimir effect. Physicists can accurately calculate the force that pulls plates together using virtual particle mathematics. Whether the virtual particles are actually present or not, the calculations predict exactly what researchers observe in the real world.

Another mysterious prediction made using the virtual particle toolbox is the so-called Hawking radiation. When pairs of virtual particles appear at the limit of black holes, Sometimes the black hole’s gravity grabs one partner while the other escapes. This fault causes the black hole to slowly evaporate. Although Hawking radiation has not yet been directly observed, researchers have recently I observed it indirectly.

Useful fiction

Let’s come back to the question: can a mathematical tool become real? If you can perfectly predict everything about a force by imagining that it is carried by virtual particles, are these particles considered real? Is their fictional status important?

Physicists remain divided on these questions. Some prefer to “shut up and calculate” – one of Feynman’s famous jokes. For now, virtual particles are our best way to describe particle behavior. But researchers are developing alternative methods who don’t need it at all.

If successful, these approaches could make virtual particles disappear permanently. Successful or not, the fact that alternatives exist suggests that virtual particles might be a useful fiction rather than a physical truth. This also fits the pattern of previous scientific revolutions – the ether example comes to mind. Physicists invented the ether as a medium through which light waves traveled. The experiments matched the calculations made using this tool well, but they couldn’t actually detect it. Eventually, Einstein’s theory of relativity showed that this was not necessary.

Virtual particles constitute a striking paradox of modern physics. They shouldn’t exist, and yet they are essential for calculating everything from the strength of magnets to the behavior of black holes. They represent a profound dilemma: Sometimes the best ideas about reality come from a carefully constructed illusion. Ultimately, confusion around virtual particles may just be the price we pay for understanding fundamental forces.

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