5 ms·
> electrons cannot move very far before they collide with an atom which changes their direction And yet we know it’s mostly just empty space. I’m assuming it’s
by vlovich123 2y ago
> electrons cannot move very far before they collide with an atom which changes their direction
And yet we know it’s mostly just empty space. I’m assuming it’s more because of the electromagnic force being particularly strong at those scales rather than a straight up “collision” right?
- bavell 2y agoIsn't a straight up physical "collision" just a strong interaction between the electromagnetic field of multiple particles?
- vlovich123 2y agoI believe particle colliders really overcome the forces and have the particles touch and annihilate. But sure, at our level it’s all normal low energy electromagnetic stuff and nothing every really touches anything else.
- Filligree 2y agoI would really argue that "electromagnetic stuff" is what "touches" means in the first place. Atoms aren't really empty. They're electron clouds with an extremely dense core of protons and neutrons, but the electron clouds are what we care about.
- vlovich123 2y agoI think that’s just arguing over the imprecision of language. Are we referring to the human sense which is the electromagnetic field or are we referring to the abstract mathematical concept of whether two line segments touch which is what the particle accelerator does or matter/antimatter. Both definitions are valid imho.
- tsimionescu 2y agoI think it's really hard to define this fully. The most relevant parts are probably the Pauli exclusion principle (which prevents two fermions from occupying the same point in space if they are otherwise identical), and the size of elementary particles (which, as far as we can tell, is 0). Overall this means that you can get two fermions arbitrarily close, but not to overlapping positions. Since they have no know dimension, they can't "touch" unless they are completely overlapping, and since they can't overlap, and since the electromagnetic repulsion increases rapidly as you get closer and closer together, I think the parent poster is right - regardless of inertia, they will always have some kind of electromagnetic interaction that will change their course or nature before actually "touching". To add a bit of a complication, if two particles that have mass, even one as tiny as the electron, come closer together than some minimum, general relativity predicts that they would collapse into a (really really tiny) black hole. Of course, we don't know how and if general relativity really works at this level, so the relevance of this is unclear.
- TheOtherHobbes 2y agoNo, it's just different field interactions. None of this is tangible in the way that billiard balls are tangible. With particle physics there are no "things" that can "touch" - just different events in different particle fields which are more or less likely at different energies and spatial separations. You can even take it up a level and say that interaction events are the only things that really exist. That's more or less what Copenhagen QM boils down to. It is not at all a given that "particles" even exist between interactions. Intuition insists that if something happens here and something apparently related happens over there and you can move here and there around to make a line or curve, then something physical is moving between here and there. But actually - no. Not necessarily. All you have are ghost traces of an apparent chain of causality. And you can play with those traces experimentally to make them do incredibly weird shit in very surprising ways.
- hosteur 2y agoWhen does anything really touch?
- cuttothechase 2y agonever!
- BobbyTables2 2y agoSo all atoms are married?
- alex_young 2y agoVirtual particles are. Usually they wind up touching though, which always destroys both of them.
- silentguy 2y agodepends on your definition of touch.
- andrewflnr 2y ago> mostly just empty space I'm so tired of this. If atoms are "empty space", then there's no such thing as non-empty space, which makes the concept meaningless. Electron clouds have all the properties we want from non-empty space, mainly excluding other objects made of non-empty space, so let's just admit that's what non-empty space is and move past this pseudo-profound silliness.
- thereisnospork 2y agoYe olde Rutherford experiment nicely illustrates the points of 'yes it is all empty space' and why that is both non-obvious and profound. Nothing pseudo about it.
- andrewflnr 2y agoThat's a defensible perspective, I guess, but the fact remains that you don't fall through your chair, and that's all we really want from a description of "solid" matter. Turns out your chair behaves weirdly when you shoot alpha particles through it, but your bottom isn't made of alpha particles, so what does that prove as far as solidity goes? I suppose it proves that solidity is a non-fundamental property of matter, and that is profound, but that doesn't mean we need to change the name. It just seems like a semantic cul-de-sac to me.
- BobbyTables2 2y agoI think of it more like a pincushion. A needle will go right into it with very little resistance. One’s hand or fingertip — not so much.
- andrewflnr 2y agoRight. And no one confuses a pincushion for empty space. They just also don't confuse it with adamantium.
- 2y ago