Something from Nothing

There are all sorts of conservation laws in the Universe: for energy, momentum, charge, and more. Many properties of all physical systems are conserved: where things cannot be created or destroyed. We've learned how to create matter under specific, explicit conditions: by colliding two quanta together at high enough energies so that equal amounts of matter and antimatter can emerge, so long as E = mc² allows it to happen. For the first time, we've managed to create particles without any collisions or precursor particles at all: through strong electromagnetic fields and the Schwinger effect. Here's how.

Whoever said, “You can’t get something from nothing” must never have learned quantum physics. As long as you have empty space — the ultimate in physical nothingness — simply manipulating it in the right way will inevitably cause something to emerge. Collide two particles in the abyss of empty space, and sometimes additional particle-antiparticle pairs emerge. Take a meson and try to rip the quark away from the anti-quark, and a new set of particle-antiparticle pairs will get pulled out of the empty space between them. And in theory, a strong enough electromagnetic field can rip particles and antiparticles out of the vacuum itself, even without any initial particles or antiparticles at all.

Previously, it was thought that the highest particle energies of all would be needed to produce these effects: the kind only obtainable at high-energy particle physics experiments or in extreme astrophysical environments. But in early 2022, strong enough electric fields were created in a simple laboratory setup leveraging the unique properties of graphene, enabling the spontaneous creation of particle-antiparticle pairs from nothing at all. The prediction that this should be possible is 70 years old: dating back to one of the founders of quantum field theory, Julian Schwinger. The Schwinger effect is now verified, and teaches us how the Universe truly makes something from nothing.

Even in the vacuum of empty space, devoid of masses, charges, curved space, and any external fields, the laws of nature and the quantum fields underlying them still exist. If you calculate the lowest-energy state, you may find that it is not exactly zero; the zero-point (or vacuum) energy of the Universe appears to be positive and finite, although small.

In the Universe we inhabit, it’s truly impossible to create “nothing” in any sort of satisfactory way. Everything that exists, down at a fundamental level, can be decomposed into individual entities — quanta — that cannot be broken down further. These elementary particles include quarks, electrons, the electron’s heavier cousins (muons and taus), neutrinos, as well as all of their antimatter counterparts, plus photons, gluons, and the heavy bosons: the W+, W-, Z0, and the Higgs. If you take all of them away, however, the “empty space” that remains isn’t quite empty in many physical senses.

For one, even in the absence of particles, quantum fields remain. Just as we cannot take the laws of physics away from the Universe, we cannot take the quantum fields that permeate the Universe away from it.

For another, no matter how far away we move any sources of matter, there are two long-range forces whose effects will still remain: electromagnetism and gravitation. While we can make clever setups that ensure that the electromagnetic field strength in a region is zero, we cannot do that for gravitation; space cannot be “entirely emptied” in any real sense in this regard.

Instead of an empty, blank, three-dimensional grid, putting a mass down causes what would have been ‘straight’ lines to instead become curved by a specific amount. No matter how far away you get from a point mass, the curvature of space never reaches zero, but always remains, even at infinite range.

There are many ways of studying the Universe, and quantum analogue systems — where the same mathematics that describes an otherwise inaccessible physical regime applies to a system that can be created and studied in a laboratory — are some of the most powerful probes we have of exotic physics. It’s very difficult to foresee how the Schwinger effect could be tested in its pure form, but thanks to the extreme properties of graphene, including its ability to withstand spectacularly large electric fields and currents, it arose for the very first time in any form: in this particular quantum system. As coauthor Dr. Roshan Krishna Kumar put it:

“When we first saw the spectacular characteristics of our superlattice devices, we thought ‘wow … it could be some sort of new superconductivity’. Although the response closely resembles those routinely observed in superconductors, we soon found that the puzzling behavior was not superconductivity but rather something in the domain of astrophysics and particle physics. It is curious to see such parallels between distant disciplines.”

With electrons and positrons (or “holes”) being created out of literally nothing, just ripped out of the quantum vacuum by electric fields themselves, it’s yet another way that the Universe demonstrates the seemingly impossible: we really can make something from absolutely nothing!

adapted from article by Ethan Siegal on September 13, 2022 at BigThink.com