The Nothing That Has the Potential to Be Anything

A recent example was published in 2025 by researchers at the European X-ray Free Electron Laser Facility near Hamburg, among other institutions. They cooled iodopyridine, an organic molecule made up of 11 atoms, almost to absolute zero and hammered it with a laser pulse to break its atomic bonds. The team found that the movements of the released atoms were correlated, indicating that, despite its cooled state, the iodopyridine molecule had vibrated. “That wasn’t initially the main goal of the experiment,” said Rebecca Boll, an experimental physicist at the facility. “It’s basically something we found.”

Perhaps the best-known effect of zero-point energy in a field was predicted by Hendrick Casimir in 1948, glimpsed in 1958, and definitively observed in 1997. Two plates of electrically uncharged material—which Casimir envisioned as parallel sheets of metal, although other shapes and substances would do the trick—exert a force on each other. Casimir said the plates would act as a sort of guillotine for the electromagnetic field, cutting off long-wavelength oscillations in a way that would distort zero-point energy. The most accepted explanation is that in some sense the energy outside the plates is greater than the energy between the plates, a difference that brings the plates closer together.

Quantum field theorists typically describe fields as a set of oscillators, each with its own zero-point energy. There are an infinite number of oscillators in a field and so a field must contain an infinite amount of zero point energy. When physicists realized this in the 1930s and 1940s, they initially doubted this theory, but soon accepted infinities. In physics – or at least most of physics – energy differences are what really matter, and with care, physicists can subtract one infinity from another to see what’s left.

This doesn’t work for gravity though. As early as 1946, Wolfgang Pauli realized that an infinite or at least gargantuan amount of zero-point energy would have to create a gravitational field strong enough to blow up the universe. “All forms of energy gravitate,” said Sean Carroll, a physicist at Johns Hopkins University. “This includes void energy, so you can’t ignore it.” The reason why this energy remains attenuated by gravitation still remains a mystery to physicists.

In quantum physics, the zero-point energy of the vacuum is more than an ongoing challenge, and it’s more than the reason you can never truly empty a box. Instead of being something where there should be nothing, it’s nothing imbued with the potential to be anything.

“What’s interesting about the vacuum is that every field, and therefore every particle, is represented in one way or another,” Milonni said. Even though no electrons are present, the vacuum contains “electron”. Vacuum zero point energy is the combined effect of all possible forms of matter, including those we have not yet discovered.

Original story courtesy of Quanta Magazine, an editorially independent publication of Simons Foundation whose mission is to improve public understanding of science by covering research developments and trends in mathematics and the physical and life sciences.