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I was just listing to a podcast about the end of the universe and it struck me that the hydrogen atoms that we breathe and drink evey day, has been around since the beginning - over 13 billion years. During all this time, each atom has an electron spinning frantically around the nucleus non-stop. What drives this bugger? Why doesnt it slow down? Will it ever slow down? Did I fall alseep in high school physics?

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While you may have fallen asleep during high school physics this does not account for your confusion. It is likely that you were taught that the electron spins around the nucleus. Please consider the simplest case of the single electron in a hydrogen atom. Please do so because it is the only case that I understand.

This case, called the ground state of the hydrogen atom, the electron has no angular momentum. For clarity I will not refer to the quantum mechanical property of the electron called ‘spin’(1). This ground state is modeled by a wave function which is motionless relative to the nucleus. This should be confusing because they do teach that orbiting version in high school. This is how I learned it in high school.

In my first quantum class the first meeting started with an apology for all the lies that we had been taught up to this point. The lecturer said ‘ now I will tell you the truth’. Please leave your intuition at the door when you come to this class because you will not be using it here.

The most accurate description of the electron is a math model which predicts the probability of an observation. One may adopt the position that it’s shape is the shape of the electron or one may adopt the position that the electron does not have a shape. If one considers a surface of constant probability it will look like the shapes that they showed you in high school. Few high school teachers actually understand those drawings. If one chooses to take the shape of the function to be the shape of the electron then it has spherical symmetry, is centered on the nucleus and the peak of the function is in good agreement with the classical electron radius from the orbital picture.

You did not miss anything during your nap.


1) Spin in quantum is easer to think about if one considers it a type of polarization.

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Michael

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