it’s like this
there is a mirror and
there is a mirror
and they’re looking at each other
the question is
what do they see
~from The Casimir Effect, Chris Mansell
Okay, galleons, we get to talk about some exciting news in an area of quantum field theory that we have only briefly touched on once when discussing time travel way back when:
The Casimir effect.
Now, before we can discuss said news, we’re going to have to get some background on virtual particles, the physics of the vacuum of space according to quantum field theory, and a brief run-down on the Casimir effect itself.
Get comfortable, galleons.
***
When we imagine a vacuum, we imagine space devoid of matter. Completely. Empty.
Of course, that’s not entirely accurate. We consider outer space to be a high-quality vacuum, but it is, of course, not empty. It may contain only a few hydrogen atoms per cubic meter on average, but it is not completely empty. And even if we were to suck every last particle and bit of matter from a region of space… it still would never be entirely empty.
WHAT?!
You heard me. See, quantum physics is weird. There’s a reason Richard Feynman himself once said, “I think I can safely say that nobody understands quantum mechanics.” It’s confusing, defying all logic. Remember that, according to quantum physics, at the smallest levels (Planck levels), spacetime is a roiling, ever-shifting foam:
Like those wacky quantum fluctuations, there’s a thing called vacuum fluctuations, which yield things called virtual particles.
And what is a virtual particle? On occasion, things like particle decay happen via force carrier particles. And sometimes, these force carrier particles have more mass than the initial particle. What’s weird about these high-mass force carrying particles is that they seem to come out of nowhere, violating the laws of conservation of mass and energy.
However, these oddities are a side effect of Heisenberg’s uncertainty principle. High-mass force carrying particles like this are allowed to come into existence out of nothing… so long as they are incredibly short-lived. These are virtual particles.
Because virtual particles exist for such a short time, they can never be observed.
At least, not directly.
One more thing we need to discuss before we get to the actual news is the Casimir effect itself. Now, a central concept of quantum mechanics is wave-particle duality, that all particles exhibit both wave and particle properties. It’s essential to remember that as we delve into the Casimir effect. Because if a vacuum is full of fluctuating virtual particles, that means it’s full of fluctuating virtual waves as well.
Take two uncharged metal plates (or mirrors) and put them in a vacuum. Place them just a few micrometers apart. Now, there is no outside electromagnetic force acting on the plates (because we’re in a vacuum). One would think that, with no electromagnetic field outside the plates, there wouldn’t be one inside the plates either, and thus no force would be measured between them.
Except… that’s not entirely true. Somehow, the plates are attracted to one another.
Why is this? Well, if we remember our virtual particles/waves, we know that there are waves of every wavelength flickering in and out of existence all the time in the vacuum. So when we put those plates close to one another, some wavelengths can fit between the plates… and some can’t. Because fewer waves can fit between the plates, the total amount of energy in the vacuum between the plates will be slightly less than that of the vacuum outside the plates, causing the plates to move toward one another.
That, dear galleons, is the Casimir effect.
***
And now for the news:
Scientists at Chalmers University of Technology in Sweden have successfully captured some of those virtual photons and caused them to shuck their virtual selves, becoming real photons (i.e. measurable light).
Essentially, they just pulled light from the void.
Suck it, God. Science is all up in your shit.
Back in the 70s, it was predicted that virtual photons could become real photons if they were allowed to bounce off a mirror moving at a speed that is almost as high as the speed of light. This was called the dynamical Casimir effect, and it had never actually been observed. Until now.
Because they couldn’t get a mirror to actually move fast enough, Chalmers scientists decided to try a different approach. They created a faux mirror by using a quantum electronic component referred to as a SQUID (Superconducting quantum interference device), which is extremely sensitive to magnetic fields. Instead of varying the physical distance between actual mirrors, they varied the electrical distance to the electrical component, which acts as a mirror for microwaves. By using the SQUID (SQUIDMAN! ASSIST ME!) to change the direction of the magnetic field several billions of times a second, the scientists were able to make a “mirror” that vibrated at a speed of up to 25 percent of the speed of light.
Remember, we can’t actually observe virtual particles. But that’s okay- we don’t need to measure them directly. Instead, the SQUID mirror transferred some of its kinetic energy to the virtual photons, which allowed them to materialize as pairs of real photons. Which we can measure.
Why photons? Why, because photons lack mass, of course.
“Relatively little energy is therefore required in order to excite them out of their virtual state. In principle, one could also create other particles from vacuum, such as electrons or protons, but that would require a lot more energy,” said Göran Johansson, Associate Professor of Theoretical Physics.
Now, this is one of those experiments that doesn’t have any direct, practical applications. Its value lies in bettering our understanding of vacuum fluctuations. It’s science for the sake of science.
It’s also really cool.
Light being created from the vacuum? Come on. You gotta admit, that’s pretty good.
Epistula Rasa 