What is quantum tunnelling and why should you care?
Well, a reasonable argument for why you should care is that it is a prerequisite to you reading this article. Quantum tunnelling is the reason for the season(s) because without it there would be no sun! It is how the the sun manages to continuously maintain the process of nuclear fusion. Without stars undergoing fusion, they would have never created all of the elements that eventually resulted in the “star stuff” that is we.
Hydrogen, the simplest element, makes up the majority of the sun ringing in at 74.9% of its mass. Helium, at a not-so-close second, rings in right around 23.8%. Okay. So, what is nuclear fusion exactly? It is the process in which lighter atomic nuclei fuse to create heavier atomic nuclei. The resulting energy that is released is what causes the sun to burn. Well, that’s cool, right? A bunch of hydrogen running around bumping into each other to create helium. I know, riveting stuff. But, hold on, we’re about to get to the good part.
Hydrogen is a positively charged particle. So, if a bunch of positively charged hydrogen atoms are flying around then they can’t be actually slamming into each other. Can they? Well, grade level science would tell you no. Remember, “opposites attract.” So, if like charges repel each other, how are the hydrogen atoms fusing? Good question, my friends, and I’m glad you asked. The answer is quantum tunnelling.
Quantum tunnelling is the phenomena in quantum mechanics when a particle passes through a barrier that would have been impossible to pass through in classical physics. In classical physics, this would be similar to throwing a ball at a brick wall and it passing through ‒ without barrelling a hole in the wall. Obviously, the ball will not go through the wall, but in the world of the incredibly small, the quantum world, things are a little different. Because of Heisenberg’s uncertainty principle, the position of the particle when colliding has a degree of uncertainty. There is a small (read as infinitesimal) chance that the particle could exist on the opposite side of the invisible barrier that blocks the particles from colliding. It’s a REALLY small chance, but there are so many particles in the sun, that it happens all the time and causes the sun to burn.
Hence, we are star stuff.
You can watch Henry Reich of MinutePhysics explain quantum tunnelling here and how it applies to the sun.