A clever mathematical tool known as virtual particles unlocks the strange and mysterious inner workings of subatomic particles. What happens to these particles within atoms would stay unexplained without this tool. The calculations using virtual particles predict the bizarre behavior of subatomic particles with such uncanny accuracy that some scientists think “they must really exist.”
Virtual particles are not real – it says so right in their name – but if you want to understand how real particles interact with each other, they are unavoidable. They are essential tools to describe three of the forces found in nature: electromagnetism, and the strong and weak nuclear forces.
Real particles are lumps of energy that can be “seen” or detected by appropriate instruments; this feature 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 the interactions between real particles.
But many physicists are not convinced by this cut-and-dried distinction.
Although researchers can’t detect these virtual particles, as tools of calculation they predict many subtle effects that ultrasensitive experiments have confirmed to a mind-boggling 12 decimal places. That precision is like measuring the distance between the North and South poles to better than the width of a single hair.
This level of agreement between measurements and calculations makes virtual particles the most thoroughly vetted idea in science. It forces some physicists to ask: Can a mathematical tool become real?
Virtual particles help scientists follow the interactions between particles.
A bookkeeping tool
Virtual particles are the tool that physicists use to calculate how forces work in the microscopic subatomic world. The forces are real because they can be measured.
But instead of trying to calculate the forces directly, physicists use a bookkeeping system where short-lived virtual particles carry the force. Not only do virtual particles make the calculations more manageable, they also resolve a long-standing problem in physics: How does a force act across empty space?
Virtual particles exploit the natural fuzziness of the subatomic world, where if these ephemeral particles live briefly enough, they can also briefly borrow their energy from empty space. The haziness of the energy balance hides this brief imbalance, which allows the virtual particles to influence the real world.
One big advantage of this tool is that the mathematical operations describing the forces between particles can be visualized as diagrams. They tend to look like stick-figure cartoons of particle pingpong played with virtual particles. The diagrams – dubbed Feynman diagrams – offer an excellent intuitive framework, but they also give virtual particles an aura of reality that is…
