I’m grateful to quantum mechanics.
Teaching quantum mechanics, even at an elementary level, often causes me to be short of breath and a little uneasy. Of anything I teach in a physics course, this makes me the most uncomfortable because there’s a decidedly “hands off” nature to it. In fact, it’s nature’s way of telling us a bit about our limits of knowledge. At the same time, those limits make weird but critical things possible. Take, for example, all of chemistry, the periodic table, and our very existence.
There are operations of quantum mechanics that must be in existence because without them there would be no anything. With only classical physics, electrons, and their bundle of charge racing around an atom, would naturally and easily leak out energy, and in the process spiral into their respective nucleus. This would take some amount of time, of course, so you wouldn’t have to worry about this right away. That amount of time is about 0.00000000001 second.
Having just taken the time to read that, and realizing that all of our electrons should have just fallen into the deep wells of their atoms many many times over before the last moment that it took to register the meaning of it, you can now recognize that classical physics doesn’t entirely work. How do you know? You, and all of the rest of the matter in the universe, are still here. Quantum mechanics sets up the next level of rules that allows this to happen. In addition to making it so that electrons don’t just spiral into these wells in a quick, painless-but-extraordinary burst of energy, it also makes it so that electrons has only specific, “quantized” states that they can exist in. If electrons were allowed to do anything they wanted, then instead of having discrete, specific elements, we’d just have a continuous wash of particles with an infinite number of possible combinations. This might sound appealing — we all value diversity. Yet, if all these infinite possibilities existed, then no two atoms could find ways to combine into compounds. It would just be a slush of an infinite number of possible particles, and, really, this probably just reduces down to a soup, a mush, a wash of particles. And, of course, those would just be spiraling into one another and bursting in energy.
So, I suppose I’m stating that I’m grateful for quantum mechanics, but really I’m grateful for a universe in which there is quantum mechanics, which is the requisite universe for both existence and, with it, gratitude.