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how do stars shine?
somehow, particles reach forbidden regions. our model of classical physics says they shouldn’t be able to get there, yet, somehow, they do, via...
quantum tunneling.
somehow, particles reach forbidden regions. our model of classical physics says they shouldn’t be able to get there, yet, somehow, they do, via...
quantum tunneling.
let’s picture a really tall mountain.
in our classical model of physics, if you want to get to the other side of a mountain, you have to climb up, over, and back down. but if you don’t have enough energy, you can’t make the summit. (no circumventing allowed!)
(ya that’s me ⬇️)
in our classical model of physics, if you want to get to the other side of a mountain, you have to climb up, over, and back down. but if you don’t have enough energy, you can’t make the summit. (no circumventing allowed!)
(ya that’s me ⬇️)
if you can’t make the summit, you’ll either
A) turn around and to go back to your car (REFLECTION)
B) camp out on the mountain (ABSORPTION)
(also me ⬇️)
A) turn around and to go back to your car (REFLECTION)
B) camp out on the mountain (ABSORPTION)
(also me ⬇️)
but in quantum mechanics, there’s a 3rd option.
C) tunnel through the mountain to the other side
in this example, it would be like finding a buffet and tunnel on the mountain. you’d eat, and (instantaneously) keep going through the tunnel.
C) tunnel through the mountain to the other side
in this example, it would be like finding a buffet and tunnel on the mountain. you’d eat, and (instantaneously) keep going through the tunnel.
okay, why on earth does this work?!
in quantum mechanics, matter is both a particle and a wave. there is some non-zero probability that the particle will make it over the barrier.
in quantum mechanics, matter is both a particle and a wave. there is some non-zero probability that the particle will make it over the barrier.
more specifically, particles can be described as a probability wave. there is some small but non-zero probability that a particle with insufficient energy can actually reach the other side of the barrier.
okay, still hard to understand. let’s build our intuition...
okay, still hard to understand. let’s build our intuition...
picture a wave meeting a barrier, and just slightly overlapping it. the majority of the wave won’t be able to make it over the barrier, but some small part does.
in the below gif, most of the wave is reflected, but some SMALL part makes it through. (thx for the gif, Wikipedia)
in the below gif, most of the wave is reflected, but some SMALL part makes it through. (thx for the gif, Wikipedia)
let’s get back to stars. my favorite 😍.
stars shine via a process called nuclear fusion—> heavier and heavier elements are made in the core of the star. this process requires lots of energy, and we see the byproduct as starshine!
stars shine via a process called nuclear fusion—> heavier and heavier elements are made in the core of the star. this process requires lots of energy, and we see the byproduct as starshine!
but classical physics predicts that stars would have to get FAR too hot to fuse elements! so how are stars “cheating”?
answer: quantum tunneling 😎
answer: quantum tunneling 😎
remember that hiker and the mountain?
atoms *classically* don’t have enough energy to fuse in these conditions. but if we invoke quantum tunneling, some non-zero number of atoms can actually get to the other side of the energy barrier and fuse!
YAY! starshine!
atoms *classically* don’t have enough energy to fuse in these conditions. but if we invoke quantum tunneling, some non-zero number of atoms can actually get to the other side of the energy barrier and fuse!
YAY! starshine!
