This was a disappointing article. I found quite a few incorrect statements, and the overarching claim that "space inside an atom is full of clouds" isn't going to be particularly convincing considering that clouds are also.... mostly empty space.
Also no mention of the Geiger–Marsden experiments/Rutherford gold foil experiments that discovered the atomic nucleus and involve alpha particles passing through a gold foil and only being deflected with a low probability.
If you want to "bust" a myth, at least understand where it comes from instead of building up strawmen.
I am bothered by the constant talk of "virtual quanta." They are in a way abstractions as the top comment mentions, mainly because there are terms in the perturbation theory that "look like" photons and leptons that weren't there originally in the starting state. However, the "virtual" part of this is key, you can't actually observe them, so they might not really exist. They do predict changes to the interaction however.
The important detail here that drives home how virtual they are is they only exist then when the regime is perturbative, for QED, at large spatial scales, and for QCD, at small spatial scales, hence why you can talk about them in hadrons like protons and neutrons as the author does. In the nonpertubative regimes, for example, strong QED, you cannot use perturbation theory and there are no "virtual photons" you can use. For example, the most basic strong field QED, the hydrogen atom, has no virtual photons in the coulomb field, you just solve the hamiltonian with the q^2/r potential given to you a priori. As the fourier transform of ~ 1/r shows you, you would need an infinite number of photons to make a couloumb field. This problem was already known from classical physics, in which the energy density of a couloumb field including the divergence at the point charge is infinite.
I think what gives a kind of credence to the atomic void is that we see it at other scales as well.
For example, our solar system is mostly “empty” with the mass mainly concentrated in the Sun (and Jupiter). The galaxies are mostly empty as well, so that two galaxies can “collide” without a single star hitting each other.
So there is a certain intellectual pull to try to extend the analogy (wrongly?) down to the smallest level as well.
I guess the analogy still holds with gravity instead of charge? So while the "real" mass of each object is compressed so "small" that normally colliding will be improbable, their gravitational influence is much much bigger and pretty much fill the entire empty space. And this is without even considering the milky way center that influences the whole galaxy.
Interesting that galaxies can collide without a star hitting another star.. but would it also be that the distances are so vast that the stars dont even (or mostly dont even) affect each other?
I don't know about the percentage of affected stars in a typical galaxy collision but note that you don't need a collision for two stars to affect each other. We're not speaking of interaction like on a pool table. The gravity will significantly affect star systems that pass significantly close from each other.
Why would stars hit each other during galactic collisions when stars inside of a single galaxy already almost never hit each other? Apparently reading it here of all the stars in the galaxy, a stellar collision only happens once every 10 000 years.
Interestingly enough, when galaxies collide, the supermassive black holes at their centres do typically merge as their gravity is strong enough to attract each other.
It's by the way not particularly unlikely for stars to pass through other solar systems. Apparently about 70 000 years ago a binary star system flew through the Oort Cloud.
This is not at all what happened. \Rutherford, Geiger, and Marsden ran an experiment. The data was totally incompatible with a solid blob of atomic mass, but instead suggested that the positive charge of the atom was concentrated into a tiny space.
Yes but why is positive all we care about when it comes to the definition of space? If we fire neutrinos, basically 100% of the atom is 'empty space'. If we fire protons, 99% is empty. If we fire electrons, none is empty.
Why do we say it is mostly empty just because of 2/3 of these things don't interact? Disproving the plum-pudding model was significant but saying the atom is 99% empty space is misleading. We know there are billions of virtual particles appearing and disappearing all the time within the atom and space, they just cancel out.
Carl Sagan was just trying make some of these observations intelligible to children.
I can't take this article seriously if it doesn't engage with the discovery of the structure of the atom, and disregards the experiments where they shoot stuff through and it passes mostly unperturbed - because well its actually mostly empty.
It turns out that Schroedinger's equation predicts the results of the gold-foil experiment, too, and is better in some ways than the old "solar system" model of the atom.
If you dig really deep in the article - somewhere in the middle sounded by typical garbage like "We have yet to learn how to reconcile the dual wave-like and particle-like behaviour of matter" - the author actually indicates the issue he has with the apparently empty nature of atoms:
`The association between this mass concentration and the idea that atoms are empty stems from a flawed view that mass is the property of matter that fills a space.`
Whats really happening is that for certain kinds of interactions electrical forces were important, and for others nuclear forces were important. We understand the nuclear forces by proxy of mass concentrations, and reach reasonable conclusions like "the atom is mostly empty".
I actually like the idea of visualizing an atom as a cloud in addition to older visualization of orbiting “points”. But I kind of use cloud loosely in my mind and add energy field.
Although neither is technically true it helps convey they idea that everything atomically is in a state of flux.
So if you could stop time and glance inside a atom you may think to observe something closer to the empty space idea. However this situation is impossible and the representation is almost like a tesseract represented in 3d. Impossible to represent in a way we consciously operate.
But we live in a state where things are constantly in motion and thus the existing state of an atom can be kind of though of as a cloud or maybe even better thought as an energy field with predictable states.
There's a much better classical model of electron orbits as spherical fluid spinning shells or "orbitspheres" that have motion along all great circle routes.
I really enjoyed reading the article until this pop-up of “why we need your support” not only it blocked half my screen, but it also spoiled that attention I was giving to the article. These Jimmy Wales style of donations demand must be rethought, it’s too intrusive.
My approach is just to close the tab at that point. There are already more articles on the web and in print than I'll ever manage to read, and the content will probably be available elsewhere anyway.
Maybe it's a pipe dream, but my hope is that if enough people close browser tabs in reaction to rude behaviour, it'll start to show up on analytics.
Thanks, I don’t think I am willing to trade that pop-up inconvenience with my privacy offered to Googles by going through their cache. But yes I more than happy to use Archive.org. Did you have to copy the url, submitted it to archive.org to get the free access version? Or is there another secret flow I am missing?
Well-written article on descriptions of electron (and importantly, nuclei to a lesser degree) behavior and state.
A pair of strawmen to knock down in the process, most notably in the title and opening paragraphs; the second half way through, re mass concentration. clouds of moving fluff as a lay description of electrons isn't too bad. I guess the key part is to emphasize charge in addition to mass.
Tangent: I'm surprised that, at least according to [this paper by Sebens](https://arxiv.org/abs/2105.11988), Shrodinger's model of the electron wave function corresponding to a charge density (probability aside) is controversial among physicists. I suspect most chemists doing DFT agree with it.
> Shrodinger's model of the electron wave function corresponding to a charge density (probability aside) is controversial among physicists
It's more than "controversial"; it was shown not to work way back in the 1920s. That's why Born's probability interpretation was adopted--it was the only one left standing.
> I suspect most chemists doing DFT agree with it.
If all you ever have to deal with is atoms and molecules, the Schrodinger charge density interpretation sort of works--it's at least a good enough heuristic for that domain.
But quantum mechanics gets applied to lots of other domains besides atoms and molecules. The charge density interpretation breaks down in those other domains, whereas the Born probability interpretation does not. And physicists who had to deal with those other domains figured that out, as noted above, back in the 1920s, which is why Schrodinger's charge density interpretation was discarded, at least as any kind of fundamental aspect of quantum theory.
DFT is like it is a cloud of density charge with some aditional weird rules.
Or in another words, you must sum many rules to calculate the energy, an one of them is easy to remember because it's the result you'd get from a cloud of density charge.
Readit News
If you want to "bust" a myth, at least understand where it comes from instead of building up strawmen.
> but it is sure that Carl Sagan, in his classic TV series Cosmos (1980), was crucial in popularising it
I would say it was popularized by teaching the gold foil experiment in middle school physics.
(That said, it seems like a minor point of the article.)
The important detail here that drives home how virtual they are is they only exist then when the regime is perturbative, for QED, at large spatial scales, and for QCD, at small spatial scales, hence why you can talk about them in hadrons like protons and neutrons as the author does. In the nonpertubative regimes, for example, strong QED, you cannot use perturbation theory and there are no "virtual photons" you can use. For example, the most basic strong field QED, the hydrogen atom, has no virtual photons in the coulomb field, you just solve the hamiltonian with the q^2/r potential given to you a priori. As the fourier transform of ~ 1/r shows you, you would need an infinite number of photons to make a couloumb field. This problem was already known from classical physics, in which the energy density of a couloumb field including the divergence at the point charge is infinite.
For example, our solar system is mostly “empty” with the mass mainly concentrated in the Sun (and Jupiter). The galaxies are mostly empty as well, so that two galaxies can “collide” without a single star hitting each other.
So there is a certain intellectual pull to try to extend the analogy (wrongly?) down to the smallest level as well.
Interestingly enough, when galaxies collide, the supermassive black holes at their centres do typically merge as their gravity is strong enough to attract each other.
It's by the way not particularly unlikely for stars to pass through other solar systems. Apparently about 70 000 years ago a binary star system flew through the Oort Cloud.
Why do we say it is mostly empty just because of 2/3 of these things don't interact? Disproving the plum-pudding model was significant but saying the atom is 99% empty space is misleading. We know there are billions of virtual particles appearing and disappearing all the time within the atom and space, they just cancel out.
https://www.khanacademy.org/science/chemistry/electronic-str....
Carl Sagan was just trying make some of these observations intelligible to children.
I can't take this article seriously if it doesn't engage with the discovery of the structure of the atom, and disregards the experiments where they shoot stuff through and it passes mostly unperturbed - because well its actually mostly empty.
`The association between this mass concentration and the idea that atoms are empty stems from a flawed view that mass is the property of matter that fills a space.`
Whats really happening is that for certain kinds of interactions electrical forces were important, and for others nuclear forces were important. We understand the nuclear forces by proxy of mass concentrations, and reach reasonable conclusions like "the atom is mostly empty".
Although neither is technically true it helps convey they idea that everything atomically is in a state of flux.
So if you could stop time and glance inside a atom you may think to observe something closer to the empty space idea. However this situation is impossible and the representation is almost like a tesseract represented in 3d. Impossible to represent in a way we consciously operate.
But we live in a state where things are constantly in motion and thus the existing state of an atom can be kind of though of as a cloud or maybe even better thought as an energy field with predictable states.
https://brilliantlightpower.com/atomic-theory/
Maybe it's a pipe dream, but my hope is that if enough people close browser tabs in reaction to rude behaviour, it'll start to show up on analytics.
alternative one https://web.archive.org/web/20230825073946/https://aeon.co/e...
A pair of strawmen to knock down in the process, most notably in the title and opening paragraphs; the second half way through, re mass concentration. clouds of moving fluff as a lay description of electrons isn't too bad. I guess the key part is to emphasize charge in addition to mass.
Tangent: I'm surprised that, at least according to [this paper by Sebens](https://arxiv.org/abs/2105.11988), Shrodinger's model of the electron wave function corresponding to a charge density (probability aside) is controversial among physicists. I suspect most chemists doing DFT agree with it.
It's more than "controversial"; it was shown not to work way back in the 1920s. That's why Born's probability interpretation was adopted--it was the only one left standing.
> I suspect most chemists doing DFT agree with it.
If all you ever have to deal with is atoms and molecules, the Schrodinger charge density interpretation sort of works--it's at least a good enough heuristic for that domain.
But quantum mechanics gets applied to lots of other domains besides atoms and molecules. The charge density interpretation breaks down in those other domains, whereas the Born probability interpretation does not. And physicists who had to deal with those other domains figured that out, as noted above, back in the 1920s, which is why Schrodinger's charge density interpretation was discarded, at least as any kind of fundamental aspect of quantum theory.
Or in another words, you must sum many rules to calculate the energy, an one of them is easy to remember because it's the result you'd get from a cloud of density charge.
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