> 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?
I 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.
I 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.
I 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.
I 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.
No, 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.
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.
Ye 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.
That'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.
You can sit on a pincushion filled very densely with needles equally well as a solid wooden chair. Yet the needles clearly have more space between them than a solid block of wood. Your personal inability to penetrate or see into that space doesn’t mean the space isn’t there. Indeed, how do you know if there’s a microscopic crack? You look at photons reflecting and amplify them into your optical range. How do we know whether or not there’s space in the atom range? We use an electron microscope. It’s still a microscope - a tool to objectively pierce the physical realm in ways that you can’t with your own sense.
None of that, even to the extent it's true, makes a lick of difference to my point. You definitely don't need to lecture me about how scientific instruments supply info my biological senses can't. I know how subatomic particles work. I'm trying to make a point about obfuscatory terminology.
> Ye olde Rutherford experiment nicely illustrates the points of 'yes it is all empty space'
No, it does not. It illustrates that the portion of an atom that strongly scatters alpha particles occupies a small fraction of the atom's volume. Asserting that alpha particle scattering is the only correct definition of the threshold between emptiness and non-emptiness is an awfully strange position to take.
When interacting with other electrons at energy scales relevant to human life, i.e. maybe ten electron volts and down, an electron cloud is somewhere between solid (core electrons especially in heavy atoms) and squishy (valence electrons). Give a rock the ol' "I refute it thus!" and your toes will report that that rock's electrons are quite competently occupying their space.
Ask an alpha particle at nuclear energy scales a million times greater, and that electron cloud is like a swarm of gnats to a speeding car. The electrons only interact with the alpha electromagnetically, and it takes another object that interacts through the strong nuclear force to really bother a nucleus (most of the time).
Ask a neutrino, and it will tell you that all the nuclei in the Sun are but a wisp of fog.
This is a good example of how approximations valid in one regime fail in another but are
not therefore useless. Rutherford's experiment reveals that there is more going on with matter than what can be probed by fingers and microscopes and chemical reactions, but it in no way invalidates those other observations.
I don't know how established this is, but I'm partial to the "vacuum is elastic, non-linear medium, and particles are waves trapped in the non-linearity - self-confining energy" hypothesis. IANAPhysicist, but this really seems to make a lot of sense and is quite elegant:
And with this, there's no empty space in atoms, as the vacuum perturbations from each particle spread out to infinity, so inside the atom there's more energy in those perturbations than outside - the space is less empty inside than outside.
But what is the nature of the "perturbations"? Relativistically self-interacting knots/manifolds? Can you take the elastic medium and fold it onto itself (through higher dimensions?) in a manner similar to (but not the same as) a microscopic black hole to stabilize it into a particle?
Either I'm going schizo or I should read some real books on the subject.
As I understand it, the idea in the video is that if vacuum can be seen as non-linear elastic medium, then with the right functions for elasticity and stress, you can create conditions where EM waves at high enough frequency will hit the "sweet spot", a local minimum, where the energy gets confined in space by those non-linear properties, and can't leave without supplying additional energy. And such confined energy seems to behave like you'd expect particles to.
Again, I am not a physicist, so I'm probably wrong in understanding what half of the words I used above mean. But I do understand the idea of multiple forces creating semi-stable states that are "energy traps". For instance, the balance between electric repulsion vs. attraction from strong nuclear force is what defines how tightly bound is the nucleus of any given atom (aka. the "nuclear binding energy"). The nucleus can't expand or split apart, nor can it contract, unless you supply additional energy. When you do - say, you hit a large atom with high-speed neutrons to break past strong force attraction, or smash two small nuclei together at high speeds to overcome electric repulsion, the other force takes over resulting in a rather spectacular release of energy[0] as matter finds new stable configuration.
So I feel the idea here is similar, but with stress and elasticity in place of strong and electric forces - if there's enough energy propagating through some space, the wave gets trapped in a spatially-confined region instead of dispersing into the medium.
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?