Why doesn't the electron fall into the nucleus?

[thoughtgaze]

These two statements that I highlighted appear to be contradictory to each other.

The reason why the scenario is conceptually difficult is that it makes OTHER issues difficult. A pendulum has its bob a specific location as a specific time, not spread out all over its trajectory, the latter of which is the conventional picture adopted by standard QM. And there ARE consequences of such a scenario, ranging from molecular bonds, to the existence of the coherent gap in SQUIDs experiments.

Besides, is the mathematics describing the two systems even equivalent?

Zz.

I meant that the probability distribution is constant IN TIME yet the thing is moving. The probability distribution is clearly not constant with regard to position. And no the mathematics describing these two systems are not equivalent. I think that's because of how we perceive things though, perhaps they are equivalent with regard to some other dimension... anyway this is not the point. I was only showing how it's not conceptually difficult even in the classical sense to think that a probability distribution is constant yet have the particle moving.

 

[JayAaroBe]

I've read all the threads relating to this question but my mind is just having trouble with the concept. Let's take the simplest case: a hydrogen atom with one proton and one electron. They have opposite charges and attract. If I think of each as a particle, then my mind wonders why wouldn't the two particles attract each other and come together and collide.

The only way I can make sense of it is as follows, and tell me if this is an okay way to think of it: the electron is not a particle, but rather a spherical cloud of charge. In this case, I think of it the electron not as a single point but rather as the atmosphere around a planet and the planet itself as the proton (I know the sizes are not to scale). This is the only way I can think of it that makes any sense to me and answers the question of why an electron is not pulled into the nucleus (the proton).

 

[eaglelake]

Re: why doesn't the electron fall into the nucleus!?


This is what happens when we insist on using classical physics to describe a quantum system! Classically, an electron-proton system has no equilibrium state – the electron will spiral into the nucleus while radiating away its orbital energy. There is no such thing as a “classical atom”. There are only “quantum atoms”. And, quantum mechanics is about probabilities. It does not describe the motion of the particles involved. In fact, the electron and the proton are entangled in a way that has no classical analog. We must think of the atom as a single entity. The electron and proton are not separate objects that have independent identities . I know this is not what most of you want to hear, but there is no “electron moving around a nucleus”!

So, what does quantum mechanics tell us about the hydrogen atom? It tells us the possible values to expect IF WE MEASURE the energy, for example, and it tells us the probability of obtaining each energy value. Notice that we do not know the atom’s energy, but only the value we might get as a result of an energy measurement. This is because the atom is further entangled with the energy measuring device: the atom is non-separable from the rest of the experimental apparatus. The bottom line is this – we only know that we have an experimental apparatus involving hydrogen atoms that measures the energy.

It is very difficult to discuss such things because we are using the language of classical physics to describe non-classical events. This is an unavoidable dilemma that physicists are forced to live with. And it certainly generates a lot of controversy!
Best wishes

 

[A. Neumaier]

The only way I can make sense of it is as follows, and tell me if this is an okay way to think of it: the electron is not a particle, but rather a spherical cloud of charge. In this case, I think of it the electron not as a single point but rather as the atmosphere around a planet and the planet itself as the proton (I know the sizes are not to scale). This is the only way I can think of it that makes any sense to me and answers the question of why an electron is not pulled into the nucleus (the proton).

This is indeed the most sensible classical view of an atom among the various possibilities, but
it doesn't explain what you'd like it to explain. Indeed, a classical charged electron cloud would still be sucked in by the proton. So, no matter how you do it, classical pictures for quantum phenomena are somewhat limited. The stability of an atom cannot be explained classically, but requires an understanding in terms of quantum mechanics.

 

[Ikoro]

energy and momentum is conserved by the electron...In some sense the electron is in a non-inertial reference frame because of its constant motion or velocity.