Empty space, by definition, is space that can be filled by something. So how closely can atoms pack together? A neutron star has a density of 10^17 kg/m^3, whereas the typical human being is about 10^3 kg/m^3. I could fit the matter of trillions more human beings in the same space I'm taking up now. So yeah, I think there's some empty space in me.
So the author is saying fields are already filling things up, right? To compare this to the "we can pack them atoms tighter" model seems to be confusing the author's model with another, separate mental model, one in which we can fill up more. But the author's model says we're full. Full of this field stuff. Not so? IANAS
Yeah, they're probability distributions, not fields. So electrons, protons and neutrons are still tiny, even though their positions are uncertain. And so atoms are still mostly empty space.
That's also the difference between raster and vector modeling of virtual geometry. There is an area on a graph where one literally takes less space on a computer's memory than the other, for representing essentially the same information.
I think it’s fine to have the usual view, “this box is full of water”.
But you might also think, “this eyebrow is hairs with not too much space between.”, or “this box is hydrogen and oxygen without too much space between.”
An eyebrow is hairs with a certain spatial density and distance (space) from the eyes. Water is hydrogen and oxygen with relatively less space between than say water vapor.
If I think of space as a magnitude, all the math and forces still work out, but there is “room” for other stuff.
This is what I took from the article as well. Though, it's important to note that the 'billiard ball' particle model is just a model also.
On a related note, as a physics grad, I've been looking into growing evidence that shows consciousness affecting what we observe (i.e. wave-particle duality in this case).
As a lapsed Cognitive Scentist, I had stopped paying attention to consciousness studies and thought Penrose was full of it. This comment sparked my interest. Will look into this movie but curious for pointers for summaries of recent evidence?
I believe there is non-zero vacuum energy. So "something" is going on, whether it be virtual particles popping in and out of existence, even in "empty space".
Granted, I don't really understand the details of what this means, but that's what I remember of the current science.
Yes, vacuum energy. But that's still probability distributions, and so almost all of the vacuum is empty at any given time.
Most physicists would likely say that there's no point trying to visualize this stuff in mundane terms. Or at least, that's what they were saying the last time I took a physics course.
Modeling electrons as tiny objects that have probability distributions has a weakness. There is no sensible value to assign to the 'tiny'. I mean there is no experiment to determine the 'size' of the electron.
That's essentially just an approximation. In some problems it can be useful to model the electron as having a finite radius, but our current understanding is that particles like electrons are literally infinitesimal points. In that case it's generally more useful for us to use things like Dirac delta functions to model them more accurately.
Check all the disclaimers on that concept, in particular "Attempts to model the electron as a non-point particle have been described as ill-conceived and counter-pedagogic"
Do those fields extend into infinity or is there a boundary that the electrons don't cross?
>If you took an atomic nucleus and bound only one electron to it, you would see the following 10 probability clouds for each electron, where these 10 diagrams correspond to the electron occupying each of the 1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, 4d and 4f orbitals, respectively. The electron is never located in one specific place at one particular time, but rather exists in a cloud-like or fog-like state, spread throughout a volume of space representing the entire atom.
If there is no boundary, then the universe itself would be full by that field definition because every electron would be at any point by a very small probability.
You’re not filled with fields or those fields would block neutrinos. Instead we can shoot them though the earth and detect them just fine on the other side. Fields represent possible locations, not actual locations.
For anything that responds to the electromagnetic force, you're filled with fields. For something that responds only to the weak force, you're almost entirely empty space.
In the English-language usage I grew up with, 'occupied' means that there is something there, while 'filled' means occupied to the point where nothing more can be added. The former does not imply the latter.
In this usage, space itself (the 'empty' space of the article's title) is implicitly not something.
This usage may seem to be an accidental issue of language, resulting from an incomplete understanding of physics, but a lot of metaphysics seems to reach the point of hanging on such definitions. One may, of course, agree with both of the points of view expressed in this paragraph.
This whole idea of empty space within atoms is just nonsense using English grammar as a substitute for physics. It's a meaningless statement either way until you define the terms specifically enough. And by doing that, you can choose whatever answer you want. "occupied to the point where nothing more can be added" isn't specific enough because you can still add a lot of photons to a "filled" glass of water, so that means it's not filled by that definition even though it is by common sense. It just shows the irrelevance of everyday words and concepts at the subatomic scale.
Even a neutron star is practically invisible to neutrinos which can easily pass through it despite it's being "filled" with neutrons.
It’s abstract, but we experience this kind of issue with language lot. Think of a box that doesn’t have any objects in it. It’s empty, right? But if it’s sitting on the table in front of you it’s probably full of air.
So in one respect it’s completely empty but in another it’s totally full.
The core of a neutron star is 100% neutrons (or perhaps a quark-gluon plasma where no individual neutrons are distinguishable). All the electrons and protons have been crushed together (by the extreme gravity) until they merge and form neutrons. As you get further away from the core, you find more and more protons and electrons, but still no atoms. The surface layer of the star has distinct atomic nuclei, but since the surface temperature is so hot (600,000K) they are not neutral atoms; the electrons are not bound to the nuclei. The density at the surface is still about a thousand times higher than the density of water or stone.
>Empty space, by definition, is space that can be filled by something.
Is it? I'd say empty space is empty space whether it can be filled or not.
If the universe was just 2 plates N meters apart that was impossible to move any closer (e.g. because of opposite forces, like with magnets which work fine in a vacuum), the space between them would still make sense to call empty...
> Is it? I'd say empty space is empty space whether it can be filled or not.
Though technically correct when sticking to matter, it feels so wrong because of how it encourages inapplicable intuitions from the macroscopic world.
"We are mostly empty space" is used as trivia, with an implicit exclamation mark suggesting it is astonishing and significant, but it is intentionally incomplete and lacks context - the whole picture shows something far more substantial that has nothing to do with our macroscopic intuitions.
Is it just me who found the technical description and analogy here lacking?
There's nothing that suggests electrons are a cloud. Yes, a "cloud" defines the probability where they can be found, but electron doesn't occupy the cloud.
Electron is always a point, no matter what wave function it has. Therefore, from this perspective space is all empty.
If you invoke path integrals and infinitely many things bubbling in and out of existence, space suddenly fills up. But the author doesn't even mention that.
If you want to understand this stuff, read up Feynman's descriptions & lectures on QED.
If an electron is always a point, how does it have a wave function? Field is the proper term for "cloud", and Quantum Field Theory is an alternative description of the universe, where fields are fundamental, and particles are excitations in the fields.
> Electron is always a point, no matter what wave function it has. Therefore, from this perspective space is all empty.
That depends on what interpretation you're going with. Even with that caveat, I'd be surprised if most physicists would agree with that statement. Electrons are in fact described by the wave function. It's not that the wave function tells us where the electron is, but that the best way of describing the reality of the electron is through its wave function. How and why measurements seem to cause that wave function to collapse to a definite location is different depending on your interpretation of QM.
The electron is both a particle AND a wave. So for practical purposes we must use words like clouds, or regions, or the electron is “spread out”
Neither of the words capture the essence of what is truly going on, afaik.
Language is ambiguous and we are debating between two meanings of empty - nothing there or nothing there, but can be replaced with something else. And we have the added distraction of what nothing means - no physical, permanent “particles” or the abstract empty space.. We can go down the rabbit hole of parsing semantic meanings.
How often do objects interact with our bodies when passing through us? Neutrinos, very rarely. The atoms of an aluminum bat, very commonly. Light? It depends.
Something being "empty" or "full" all depends on spatial and energetic scale.
But visible light can't get through us at all. Does that prove that we aren't empty space? The whole point is that this criterion is incredibly ambiguous.
Depending on the conditions, it is through that neutrinos can pass through even very degenerate matter like that which forms neutron stars. "Empty space" really doesn't mean all that much if the thing that is interacting with it does so weakly.
All the article says is that "empty" isn't enough information.
If "empty" means "I can put electrons in there", then it takes more binding energy to pack more electrons into the same space. If you want to pack more electrons in, you have to squeeze harder.
Example: you can confine an electron to a tiny part of an atom (electrons in inner shells of heavy atoms, for example) but those electrons are very tightly bound (held in by very high ionization energies).
Or the "emptiness" of an atom could be measured using neutral particles, which don't interact with the electrons at all and sail right through as if the electrons were empty space.
For what it's worth this is normal sophomore physics. There's no way to just dismiss it. But there's also no way to claim it's less than a hundred years old.
> For non-quantum objects, this isn’t a problem, as different methods of measuring an object all give you the same answer. Whether you use a measuring stick (like a ruler), high-definition imaging, or a physics-reliant technique like Brownian motion or gravitational settling, you’ll arrive at identical solutions.
Right off the top, it's made clear this author doesn't know what he or she is talking about. From at least the time of de Moivre, around 1740, the problem of estimating an accurate true value from multiple differing measurements was recognized in its own right as a problem. By 1810, Gauss and Laplace had discovered the basics of statistical estimation, the form of the normal distribution, results including the central limit theorem, and regression techniques such as non-linear weighted least squares. Now, almost 200 years later, the problem still exists, and is being worked on in various forms and circumstances.
To give a simple example, take 1000 frames of well-exposed video of a still scene, with constant illumination, and constant exposure settings on the camera. Now try to estimate how many photons, within a constant multiplicative factor, are coming from each point in the scene. Most of the measurements will show a normal distribution, but at the extremes of exposure, something more complex is going on (perhaps to do with sensor non-linearity, censored sampling, or something else). This is one of the basic theoretical problems in HDR imaging, and is an active area research (i.e. unsolved, as of today).
It's very hard to get past that paragraph -- which is the first one in answer to the question "why?".
So, in an atom, how much volume does the electron cloud occupy? It's more than the volume an electron occupies, but, in the upper end, does it occupy all the space from the electron to the nucleus? (And also because it is rotating, that space then occupies all the area surrounding the nucleus as well?)
One on hand, electrons as point particles sure sounds empty enough. On the other hand, the fields fill everything.
But on the gripping hand, you could set the volume of the electron to something ludicrously large, like the volume of a proton, then use the charge distribution of whatever "orbital" to trade that charge for an equivalent amount of proton-volume, as sort of a percentage filled of unit volume ... integrate, and you could get a sense of the density.
That, I think, is about as fair as you could ask for when dealing with point particles that are still smeared around.
Excellent explanation. My question after this is, at a macro level,how much of space is actual pure space. Pardon the childish question but how exactly would one measure space (nothing exists at this point) without introducing something that might be displaced by the measurement,or how can one be sure space isn't made up of lower energy qanta that are displaced by higher energy particles,much like how solids displace gases and liquids?
Yeah, agree with this and disagree with other comments, thought this was a very effective communication of a better thought-model for understanding- still in largely colloquial terms- what is going on.
To the point about "pure space"- I suspect the colloquial answer is that there isn't any pure/just space. I know that Wolfram is also not respected on here much but I like his- not intentionally metaphorical- arrival at a story for space being a process.
My understanding of quantum physics is miniscule; so a question: would it be potentially true to say that the concept of "emptiness" as we define it is essentially meaningless at the quantum level?
Yes. Concepts can stop making sense in situations that take them apart. For example, it makes sense to ask whether an apple is a fruit, but it doesn't make sense to ask whether an atom inside the apple is a fruit.
Even if you'd take just one electron, its cloud is infinite. Like, really, when people talk about things like shape of the cloud, what they mean is the density of the cloud, or the shape that you get when you only take the region where the density exceeds some arbitrary level.
So, from this perspective, as long as at least one electron exists in the universe, there is no empty place in the universe. Because, with infinitesimal probability, the electron could be anywhere.
Obviously, this is NOT what we mean by emptiness in everyday life.
(The article is okay, but its title is pure clickbait.)
> But until such an interaction occurs, the electron has been acting like a wave all along.
What does that mean? Most interpretations of quantum mechanics consider the wave function to be an abstraction to model the system, not something that is actually tangible. Even in theories that consider it real (e.g. De Broglie-Bohm) it acts as some sort of field, not something that actually occupies space.
That's rally not correct. Interpretation of the double-slit experiment relies on the electron (or photon) wave actually spanning both slits. It's not enough to treat the electron as a point particle and the wave as being something we pretend exists to explain it's wave-like behaviour. If the wave wasn't real, we wouldn't see the behaviour.
“Empty space” is a completely relative notion. If I have a heavy steel safe which I do not have the key for, whether there is an empty space inside it is irrelevant, and the space occupied by the safe cannot be seen as being (partially) empty in any practical sense.
That's not a terrible place to start. "Under most definitions the radii of isolated neutral atoms range between 30 and 300 pm (trillionths of a meter), or between 0.3 and 3 ångströms."
What is it about Medium that produces less than stellar articles? Because it is a paid blogging service so people just blow out some smoke and hope to make a little money?
because it resembles an old 2003 sensibility of blogs which resonated with a pseudo sensibility about certain types of New Yorkeresque/90s WIRED vibe. Medium is not good, I use it right now to create synopsis for YouTube videos I make, it's basically Myspace, which was useful for non professional and pro musicians to just get the music out.
> Inside your body, you aren’t mostly empty space. You’re mostly a series of electron clouds, all bound together by the quantum rules that govern the entire Universe.
So we are mostly electron clouds... and clouds by definition are mostly empty space.
From what I understand, the idea of "empty" no longer makes sense at that level. All you have are fields. There, everything is made out of fields and fields are everywhere. There is therefore no "empty" really anywhere, including inside yourself.
Physics is all based on predictions not arbitrary definitions. To suggest something is filling space you must be able to hit it with something else. This talk of empty space, comes from actual experiments.
Shoot a neutral particle through that cloud and you generally find it really was empty. Wave particle duality doesn’t mean a particle is in every location, just that it could be in every location. After detection you generally find all the places it was not.
An oxygen tank where you can safely add more oxygen by increasing the pressure is not considered full. The percentage of how empty a container is can be considered 1 -(amount of stuff in it) / (maximum stuff possible).
At the scales our brains are familiar with we experience "emptiness" as a kind of space which can have things placed in it. A chair is empty if you can sit on it, a box is empty if you can put something in it. The sub-atomic "empty" space is filled with fields of various kinds. You could not place something where those fields are. The spaces are not empty.
When you fill a box with things, you are filling it with sub-atomic fields.
> Inside your body, you aren’t mostly empty space. You’re mostly a series of electron clouds, all bound together by the quantum rules that govern the entire Universe.
> So we are mostly electron clouds... and clouds by definition are mostly empty space.
But if this article is correct, then clouds are not, by definition, mostly empty space!
My point is that one cannot settle this sort of issue by invoking the definition of words. I am not sure what sort of fallacy the 'argument by dictionary definition' is, but it is definitely a fallacy (except possibly in lexicography.)
Why the downvotes? That reply might have been ELI5-level, but I am a physicist.
Atoms are fuzzy things without a hard interface boundary. At that scale it doesn't really make sense to say they have a "perimeter" at all. The distance at which they repel each other is different from the distance at which they cling together in a hydrogen bond, which is different from the distance between covalently bonded atoms, etc. The electrons themselves roam all over the place, including far outside whatever bond distance you might choose as the size of an atom. In short, there isn't a perimeter which defines "inside" and "outside" of the atom.
The "empty space" thing is a bit of a poor analogy anyway. It comes from chemical experiments which showed that the repulsive cross section of an atom when pummeled with zero-charge particles is orders of magnitude smaller than the electric cross section. These are different forces though (strong vs electromagnetic), so it's a bit apples-to-oranges to begin with.
