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 consisting of 11 atoms, to almost absolute zero and hammered it with laser pulses to break its atomic bonds. The team found that the motions of the free atoms were correlated, showing that despite the cold state, the iodopyridine molecule was vibrating. “This was not the main goal of the experiment in the beginning,” said Rebecca Boll, an experimental physicist at the facility. “This is basically something that we found.”
Perhaps the most famous effect of zero-point energy in a field was predicted by Hendrik Casimir in 1948, glimpsed in 1958, and definitively observed in 1997. Two plates of electrically uncharged material – which Casimir saw as parallel metal sheets, although other shapes and materials would do – exert a force on each other. Casimir said the plates would act as a kind of guillotine for the electromagnetic field, cutting off long-wavelength oscillations in a way that would skew the zero-point energy. According to the most accepted explanation, in some sense, the energy outside the plates is greater than the energy between the plates, a difference that pulls the plates together.
Quantum field theorists usually describe fields as collections of oscillators, each with its own zero-point energy. A field has an infinite number of oscillators, and thus a field must have an infinite amount of zero-point energy. When physicists realized this in the 1930s and 40s, they were skeptical of the theory at first, but soon became convinced of infinity. In physics – or in most physics, at any rate – energy differences really do matter, and careful physicists can subtract one infinity from another to see what’s left.
However, this does not work for gravity. As early as 1946, Wolfgang Pauli realized that an infinite or at least enormous amount of zero-point energy should create a gravitational field powerful enough to explode the universe. “All forms of energy are gravitationally attracted,” said Shawn Carroll, a physicist at Johns Hopkins University. “There’s also vacuum energy involved, so you can’t ignore that.” Why this energy remains gravitationally quiescent is still a mystery to physicists.
In quantum physics, the zero-point energy of a vacuum is more than an ongoing challenge, and it’s more of a reason why you can never actually empty a box. Instead of being something where nothing should be, it has the potential to be anything.
“The interesting thing about the vacuum is that every field, and therefore every particle, is represented in some way,” Miloni said. Even though there is not a single electron present, the vacuum has “electronness”. The zero-point energy of the vacuum is the combined effect of every possible form of matter, including those we have not yet discovered.
Original story reprinted with permission from the editorially independent publication, Quanta Magazine Simons Foundation Its mission is to enhance public understanding of science by covering research developments and trends in mathematics and the physical and life sciences.
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