By Don Lincoln, Fermilab
Out of all the claims by contemporary physicists, there might be one that is the most counterintuitive of all: the idea that at every location in the universe, matter, antimatter, and energy are appearing and disappearing with riotous abandon. The Casimir effect is a strong proof that asserts the validity of this claim.
Existence of Zero Point Energy
In 1948, physicist Hendrik Casimir was talking with Niels Bohr of quantum mechanics fame. The conversation revolved around the subject of what is called zero point energy, which is another term for the sea of virtual particles that exists everywhere in space. The question under discussion was how to determine that these virtual particles existed.
Casimir came up with a test. He started out by assuming that the virtual sea existed. He then proposed taking two electrically neutral metal plates and placing them side by side, so there was only a very small gap between them, say a fraction of a millimeter. He reasoned that if a researcher did this under controlled conditions then the virtual sea would cause the two plates to drift toward one another.
Understanding Casimir’s Proposition
So, how would it work? It all arises from a combination of the virtual sea and the fact that particles have both a particle and a wave nature. To understand his reasoning, we need to understand virtual particles.
Anywhere in space there is a location that has no energy from a classical point of view. But, because of the Heisenberg uncertainty principle, a photon can spontaneously appear for a short period of time. High energy particles can appear for a very short time. Low-energy particles can appear for a longer amount of time. But, no matter what, these virtual photons have a short lifetime.
And, of course, the virtual photons can produce matter/antimatter pairs of particles, which can subsequently emit more photons, which can produce more matter/antimatter pairs, etc.
In the end, there is a crazy frenzy of particles of different energies, appearing and disappearing. There will be more lower energy particles, simply by virtue of the fact that they last a wee bit longer than the high energy ones.
This article comes directly from content in the video series The Evidence for Modern Physics: How We Know What We Know. Watch it now, on Wondrium.
Particles as Waves
It is important that we remember that particles aren’t just particles, they are also waves. So, the high-energy particles have short wavelengths, while low-energy particles have long wavelengths.
That means that everywhere in space, there are a bunch of waves appearing and disappearing. There are long wavelength particles, short ones, and everything in between.
Experiment With Metal Plates
Now, we have two metal plates into consideration which are located very close to one another, with a tiny distance separating them. The waves appear both outside the plates and between them.
Because the plates are very close to one another, only the short wavelengths can fit between the plates. Outside the plates, all wavelengths can fit just fine. That means that there are more waves outside the plates than there are between the plates and that also means more particles.
Because there are more particles outside the plates than inside the plates, there is an extra pressure outside the plates and the result is that the two plates will get pushed together. This is a firm prediction of the theory if the idea of a sea of virtual particles is true.
Steve Lamoreaux’s Findings
Casimir made the prediction way back in 1948. It took a long time to be able to design equipment to make the measurements. In fact, it wasn’t until 1997 that Professor Steve Lamoreaux was able to make the measurement.
He took two metal plates, separated them by tiny distances—between 0.6 and six micrometers—that is, ballpark, a millionth of a meter, or a thousandth of a millimeter separation. What he found is that the presence of the metal plates altered the zero point energy bath of virtual particles in agreement with the prediction made by Casimir. The plates moved together, pushed by a force that agreed with Casimir’s estimate to within 5%.
The combination of work by Casimir and Lamoreaux definitively proved that zero point energy was real and that virtual particles exist everywhere in space.
Practical Application of the Casimir Effect
There are practical consequences for the Casimir effect. One thing that is increasingly popular in electrical engineering are what are called micro-electro-mechanical system chips, or MEMS for short. The MEMS are tiny circuits that combine both electrical circuitry and super-tiny mechanical systems that move. These systems can be much thinner than a human hair.
These MEMS are everywhere in modern technology. One can find them in their big screen television as a way to get the best high definition projection performance. One can find them inside high-end inkjet printers.
MEMS in Phones
Perhaps the most familiar technology that uses MEMs is our smartphone. Depending on the model, they can have barometers, which measure air pressure. Almost all phones contain accelerometers, which sense if our phone is tipping or moving or anything like that. Some phones use MEMS as microphones. It’s a way to make the phones super thin and lightweight.
A use of MEMS is in lightweight and disposable insulin pump that helps diabetics manage their diabetes. Some are even implantable, which means they do the work of the pancreas. If you happen to be a diabetic, there’s a good chance that you could be using MEMS to save your life.
Because MEMS depends on the separation of two surfaces by tiny distances, the Casimir effect cannot be ignored in these devices. In fact, electrical engineers are now able to design a number of different geometries that manage Casimir effect and even use it to their advantage.
Common Questions about the Casimir Effect
Hendrik Casimir proposed taking two electrically neutral metal plates and placing them side by side, so there was only a very small gap between them. He reasoned that if a researcher did this under controlled conditions that the virtual sea would cause the two plates to drift toward one another.
The combination of work by Hendrik Casimir and Steve Lamoreaux proved that zero point energy was real and that virtual particles exist everywhere in space.
The Casimir effect is widely used in electrical engineering to make micro-electro-mechanical system chips, or MEMS, that are further used in smartphones, television screens, etc.