Throughout the rest of this competition, we’ve talked a lot about what light does: how it interacts with objects, how our eyes manipulate it, how it belongs to a spectrum of electromagnetic radiation, and how to combine “primary” light frequencies in order to create additional colors. But we still haven’t talked much about what light actually is, and for that, we have to get very small.
As mentioned in our announcement post, light is composed of elementary particles known as photons; these also form the building blocks of other EM radiation. Nowadays, physicists know there are many varieties of subatomic particle, each playing a critical role in why our universe works the way it does, but photons have some rather special qualities. They have no mass (although gravity can still affect them), they have no electrical charge (although they are naturally emitted by electromagnetism), and they do not decay over time (although we often hear “radiation” and think of radioactive decay). And very importantly, a photon can be characterized as both a singular particle and a wave function, although depending on exactly what school of physics you belong to, you may consider it more of one than the other.
None of these properties are exclusive to photons — not even the wave-particle duality. But within its larger class of elementary particles known as gauge bosons — which each carry one of the four fundamental forces (electromagnetism, strong force, weak force, and gravity) — photons are one of the only particles with all of these properties in combination. And while the gauge bosons known as gluons have these properties as well, gluons only interact with each other or with quarks, whereas photons only interact with electrically charged particles and can never interact with other photons. There are also more complicated distinctions between photons and gluons that make our eyes spin at HQ.
Furthermore, the photon was the first wave-particle really identified as such, and these studies were integral to early developments in quantum mechanics by scientists such as Max Planck, Niels Bohr, and of course, Albert Einstein, who although known more for his theories of relativity also worked extensively with light and whose paper “On the Quantum Theory of Radiation” informs how later engineers invented laser technology.
And speaking of Einstein, we can also thank him for demonstrating why the speed of light is what it is… sort of. This speed of 299,792,458 m/s had been calculated by various scientists for ages, and in the mid-1800s James Clerk Maxwell demonstrated that because electromagnetic waves move at that same speed, and because light waves are the same as electromagnetic waves, there was an electromagnetic origin for what we call lightspeed. Einstein took things a step further when he worked out that light is how to “convert” between measurements of space and measurements of time. The speed of light is an elegant mathematical constant for how fast any particle can move if it doesn’t have mass.
Even then, however, that’s not a full explanation for why the universe is put together in a way why 299,792,458 m/s is the specific speed. For that, we can thank another German physicist, Arnold Sommerfeld, for doing some definitely not intense mathematics that yielded the separate constant value α. This value is something like 1 divided by 137.036. Kind of. And we live in a universe whose subatomic particles are governed by this value. If we didn’t, then the speed of light would also be different. But we do… so it is!
If this whirlwind of information has you spinning up and ready to fly at the speed of light yourself, that’s perfect timing! Speed will soon be of the essence. Starting at 10:00 AM EST on 2/23, you will have 24 hours to complete one or more cells! Bonus & cell renaming information can be found in your in-game notifications.
Swag: Anyone in the top 25% of participants will be entered into a raffle, for which the five prizes include a wall clock, a pillow (new for this year!), and three sticker/magnet sets.