In our common experience, you can't get something for nothing. In the quantum realm, something really can emerge from nothing.
In theory, the Schwinger effect states that in the presence
of strong enough electric fields, (charged) particles and their antiparticle
counterparts will be ripped from the quantum vacuum, empty space itself, to
become real. Theorized by Julian Schwinger in 1951, the predictions were
validated in a tabletop experiment, using a quantum analogue system, for the
first time. |
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 antiquark, 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 year 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.
This chart of the particles and interactions details how the
particles of the Standard Model interact according to the three fundamental
forces that Quantum Field Theory describes. When gravity is added into the mix,
we obtain the observable Universe that we see, with the laws, parameters, and
constants that we know of governing it. Mysteries, such as dark matter and dark
energy, still remain. |
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. |
But even for the electromagnetic force — even if you
completely zero out the electric and magnetic fields within a region of space —
there’s an experiment you can perform to demonstrate that empty space isn’t
truly empty. Even if you create a perfect vacuum, devoid of all particles and
antiparticles of all types, where the electric and magnetic fields are zero,
there’s clearly something that’s present in this region of what a physicist
might call, from a physical perspective, “maximum nothingness.”
All you need to do is place a set of parallel conducting
plates in this region of space. Whereas you might expect that the only force
they’d experience between them would be gravity, set by their mutual
gravitational attraction, what actually winds up happening is that the plates
attract by a much greater amount than gravity predicts.
This physical phenomenon is known as the Casimir effect, and
was demonstrated to be true by Steve Lamoreaux in 1996: 48 years after it was
calculated and proposed by Hendrik Casimir.
The Casimir effect, illustrated here for two parallel
conducting plates, excludes certain electromagnetic modes from the interior of
the conducting plates while permitting them outside of the plates. As a result,
the plates attract, as predicted by Casimir in the 1940s and verified
experimentally by Lamoreaux in the 1990s. |
Similarly, in 1951, Julian Schwinger, already a co-founder
of the quantum field theory that describes electrons and the electromagnetic
force, gave a complete theoretical description of how matter could be created
from nothing: simply by applying a strong electric field. Although others had
proposed the idea back in the 1930s, including Fritz Sauter, Werner Heisenberg,
and Hans Euler, Schwinger himself did the heavy lifting to quantify precisely
under what conditions this effect should emerge, and henceforth it’s been
primarily known as the Schwinger effect.