5 ms·

Why do electrons not fall into the nucleus?

48 points by thunderbong 2y ago

senectus1 2y ago
Not sure I understand it any better having read this. but I did find it interesting and thought provoking.
- aabhay 2y ago
  I personally think the mere idea that you can map on abstract functions that have infinities and boundary conditions, on to a representation that extremely precisely models our physical world, is more astonishing than having a low level understanding of the equations. The final image of the probability density summed over the region around the nucleus, really drove that home for me
snippy 2y ago
> However, an electron, unlike a planet or a satellite, is electrically charged, and it has been known since the mid-19th century that an electric charge that undergoes acceleration (changes velocity and direction) will emit electromagnetic radiation, losing energy in the process. If I take a small piece of matter and shake it for a long time, then don't all its electrons and protons emit electromagnetic radiation and lose energy? To me it seems the rest of the article, i.e. probability density, also means that the electrons undergoe acceleration because their location changes.
- OgsyedIE 2y ago
  How do you know that your shaking action in the scenario isn't the input of the same energy that is emitted?
- meindnoch 2y ago
  >If I take a small piece of matter and shake it for a long time, then don't all its electrons and protons emit electromagnetic radiation and lose energy? The energy they lose by radiating is exactly balanced by the energy they gain from you by accelerating them.
- avian 2y ago
  > If I take a small piece of matter and shake it for a long time, then don't all its electrons and protons emit electromagnetic radiation and lose energy? Yes, they do. But it's only a very very tiny amount. You're shaking both the positive (nucleus) and negative (electrons) parts of the atoms. The electromagnetic fields outside of the atom almost perfectly cancel out. This means that the acceleration only affects the very small residual field and there is very little radiation at far distances, unless you shake it really really fast. Another way to look at it is that atoms are in fact already constantly shaking by themselves because of thermal movement. And this does in fact result in them emitting radiation: objects at room temperature will radiate in the infrared spectrum because of this. The trick is that thermal movements of atoms are very fast compared to moving something by hand. Room temperature infrared radiation frequencies are on the order of tens of terahertz. Compare this to manually shaking an object at (say) 10 times a second. With some hand waving math this is like giving it an equivalent temperature of around 10^-10 kelvin. It will radiate extremely long wave radio waves, but such a tiny amount that it will be completely unmeasurable.
dave333 2y ago
Mills has developed a better purely classical atomic model where the electrons are concentric spinning fluid spheres with force balance equivalent to 20k atmospheres pressure. The spinning electrons don't radiate because there is no net charge movement over time. See https://brilliantlightpower.com/theory/ https://brilliantlightpower.com/theory/
- tralarpa 2y ago
  For those who don't know Mills and his company: https://en.wikipedia.org/wiki/Brilliant_Light_Power https://en.wikipedia.org/wiki/Brilliant_Light_Power
  - dave333 2y ago
    That wikipedia page has a strong skeptical bias and is seriously out of date.
    - rcxdude 2y ago
      Sounds like skepticism is warranted.
    - terminalbraid 2y ago
      Ah, the forever cry of the crackpots. That's particularly rich complaint given it's a publicly editable resource. The only reason it could be in poor shape and "out of date" is because you yourself left it that way. If that was a truly workable theory it would have verifiable predictions and compatibility with all prior observation and it would be eagerly explored. Scientists as a whole like to find anomalies and discrepancies; it is what keeps them in business. There is no "conspiracy".
      - dave333 2y ago
        Edits are removed unless they are published in well known journals which is fair enough for scientific results, but you cannot even update the page to state Mills latest engineering improvements or update factual information about the company.
terminalbraid 2y ago
They do sometimes. https://en.wikipedia.org/wiki/Electron_capture https://en.wikipedia.org/wiki/Electron_capture
- fuzzfactor 2y ago
  >Why do electrons not fall into the nucleus? It's always possible most of them already have done so :0 Seems to me the positive & negative charges would neutralize, and it would no longer be "matter" as we know it. Not anti-matter, just not actual matter by any stretch of the imagination. Which is what most of the universe actually consists of, not actual matter. Matter itself is extremely rare, few, and far between. Could be all there is left and can be perceived by those composed of it, are the things that can have a physical nature simply because their electrons haven't collapsed into the nucleii. Yet.
internet_points 2y ago
This was quite interesting, and at a level where I found I understood something new without being overwhelmed – I tried looking around the site for more, but the site itself has me confused as to where to start, is this part of a work in progress book? How do I get to the table of contents or start of the book?
- mixmastamyk 2y ago
  By coincidence I am currently watching this series, which explains this and a lot more: https://www.thegreatcourses.com/courses/einstein-s-relativity-and-the-quantum-revolution-modern-physics-for-non-scientists-2nd-edition https://www.thegreatcourses.com/courses/einstein-s-relativit... It is on Kanopy now, for “free” (local library pays). I think there’s a subatomic-particle specific course as well that is more focused.
alok-g 2y ago
I have come across the same 'explanation' multiple times but do not find it satisfactory. >> This "battle of the infinities" cannot be won by either side, so a compromise is reached in which theory tells us that the fall in potential energy is just twice the kinetic energy, and the electron dances at an average distance that corresponds to the Bohr radius. This "cannot be won by either side" isn't a good explanation of the problem. By saying "a compromise is reached in which theory tells us ...", the article seems going around the answer instead of actually telling the answer to the question. Assuming relativity is not invoked and given a finite size of the nucleus, what is actually bringing this situation of compromise? What is pushing the electron (or its probability cloud) outwards to counter-balance?
- rcxdude 2y ago
  The opposing effect is the kinetic energy of the electron: as it get squeezed into a smaller area its kinetic energy must go up, assuming energy is constant (a classical system would more or less be the same, think how an elliptical orbit speeds up as it gets closer to the barycenter, but a quantum mechanical system doesn't necessarily have a defined trajectory). The real sleight of hand in this explanation is it doesn't really explain why the quantum-mechanical electron doesn't radiate energy like the classical electron. That's a bit more subtle, but it's basically due to the fact that the electron is wave-like and confined within the atom (i.e. it does not have enough energy to escape the nucleus). This means that the wave-function has discrete solutions as a series of 'standing waves', which is what causes the quantization in quantum mechanics.
  - alok-g 2y ago
    >> The real sleight of hand in this explanation is it doesn't really explain why the quantum-mechanical electron doesn't radiate energy like the classical electron. That's a big more subtle, but it's basically due ... This subtle part is exactly the piece that I am missing. So far, we have electron in an orbital. The orbital in itself seems stationary (standing waves), so it may seem nothing is accelerating. I presume that is not it for the answer. If it is, that still feels like, Oh, I solved Schroginger's equation, and it yields these standing waves for the solution, electron is not really having a certain position and momentum as the wave function hasn't collapsed, and thereby there is no acceleration for the electron to be radiating energy. Asking a total newbie question. I heard that QM has operators, so momentum also has an operator. Is there one for acceleration? Would it yield a zero? If so: I see Coulomb's force. Is there another force balancing it? Or is Newton's third law not valid anymore.
t8sr 2y ago
I don't like mechanistic explanations of particle physics - they're an attempt to relate what's going on to our macroscopic experience, but they usually fall apart when you look too closely. I find it much easier to understand the stability of hydrogen by thinking about ground states. If the electron in H could merge with the proton, they'd make a neutron. But a free neutron is not stable and decays in a few minutes back into a proton, electron and an antineutrino. With very large, proton-rich nuclei, eventually you get to the opposite situation where the ground state is one less proton, one less electron and one more neutron and the atom decays into that state by, you guessed it, an electron "falling into" the nucleus.
d--b 2y ago
To me the article says: the electron doesn't fall into the nucleus because we found an equation that says it doesn't.
- vkazanov 2y ago
  Yup. Half of physics is written just like this.
- mr_mitm 2y ago
  In the end, that's true for all why questions in physics. In the end, things don't have a reason for how they behave, they just do. The question of why only makes sense in a framework. Classical EM theory says electrons should fall into the nucleus, but they clearly don't. Asking why they don't is one step towards finding out about quantum mechanics, so it's a really important question to ask. Yes, at the end of the day, the answer is "because classical EM is wrong and quantum mechanics is right (or at least less wrong)". But there is a lot to learn along the way.
fithisux 2y ago
Second law of thermodynamics? The electron and the environment have the same temperature. If it falls, it emits energy warming the environment without consumption of energy. But this is impossible.
- mr_mitm 2y ago
  Single particles do not have a temperature. It's an emergent property of many-particle systems.
  - fithisux 2y ago
    you forget the thermal bath
- gus_massa 2y ago
  Good question, but no. For example you can make a very similar system with a positron and an electron https://en.wikipedia.org/wiki/Positronium https://en.wikipedia.org/wiki/Positronium . It's stable for a while, and it has very similar properties and levels like an Hydrogen atom. So the "second law" should apply too. But it has a mean lifetime of only 0.12 ns (1.2E-10s). The second law consider also the properties of the materials. For example there are small bags with sodium acetate that are used as hand heaters https://en.wikipedia.org/wiki/Sodium_acetate#Heating_pad https://en.wikipedia.org/wiki/Sodium_acetate#Heating_pad https://www.youtube.com/watch?v=Oj0plwm_NMs https://www.youtube.com/watch?v=Oj0plwm_NMs You put them in hot water, the content dissolves, and you let them cold to room temperature. When you click the metallic part, they crystallize and release heat. Another example is connecting a small lamp to a battery. It release light and heat, specially if you can get an old incandescent light bulb.
rolph 2y ago
ELI5 version, why doesnt an elephant fall into a mouse? because the elephant wavelength is too long to fit inside the mouse, so it nestles around the mouse at S1 orbit. so, why doesnt an electron fall into a nucleus? because the nucleus is too small to encompass an electron wave.

48 points by thunderbong 2y ago

senectus1 2y ago

Not sure I understand it any better having read this. but I did find it interesting and thought provoking.

aabhay 2y ago
I personally think the mere idea that you can map on abstract functions that have infinities and boundary conditions, on to a representation that extremely precisely models our physical world, is more astonishing than having a low level understanding of the equations. The final image of the probability density summed over the region around the nucleus, really drove that home for me

snippy 2y ago

> However, an electron, unlike a planet or a satellite, is electrically charged, and it has been known since the mid-19th century that an electric charge that undergoes acceleration (changes velocity and direction) will emit electromagnetic radiation, losing energy in the process. If I take a small piece of matter and shake it for a long time, then don't all its electrons and protons emit electromagnetic radiation and lose energy? To me it seems the rest of the article, i.e. probability density, also means that the electrons undergoe acceleration because their location changes.

OgsyedIE 2y ago
How do you know that your shaking action in the scenario isn't the input of the same energy that is emitted?
meindnoch 2y ago
>If I take a small piece of matter and shake it for a long time, then don't all its electrons and protons emit electromagnetic radiation and lose energy? The energy they lose by radiating is exactly balanced by the energy they gain from you by accelerating them.
avian 2y ago
> If I take a small piece of matter and shake it for a long time, then don't all its electrons and protons emit electromagnetic radiation and lose energy? Yes, they do. But it's only a very very tiny amount. You're shaking both the positive (nucleus) and negative (electrons) parts of the atoms. The electromagnetic fields outside of the atom almost perfectly cancel out. This means that the acceleration only affects the very small residual field and there is very little radiation at far distances, unless you shake it really really fast. Another way to look at it is that atoms are in fact already constantly shaking by themselves because of thermal movement. And this does in fact result in them emitting radiation: objects at room temperature will radiate in the infrared spectrum because of this. The trick is that thermal movements of atoms are very fast compared to moving something by hand. Room temperature infrared radiation frequencies are on the order of tens of terahertz. Compare this to manually shaking an object at (say) 10 times a second. With some hand waving math this is like giving it an equivalent temperature of around 10^-10 kelvin. It will radiate extremely long wave radio waves, but such a tiny amount that it will be completely unmeasurable.

dave333 2y ago

Mills has developed a better purely classical atomic model where the electrons are concentric spinning fluid spheres with force balance equivalent to 20k atmospheres pressure. The spinning electrons don't radiate because there is no net charge movement over time. See https://brilliantlightpower.com/theory/ https://brilliantlightpower.com/theory/

tralarpa 2y ago
For those who don't know Mills and his company: https://en.wikipedia.org/wiki/Brilliant_Light_Power https://en.wikipedia.org/wiki/Brilliant_Light_Power
- dave333 2y ago
  That wikipedia page has a strong skeptical bias and is seriously out of date.
  - rcxdude 2y ago
    Sounds like skepticism is warranted.
  - terminalbraid 2y ago
    Ah, the forever cry of the crackpots. That's particularly rich complaint given it's a publicly editable resource. The only reason it could be in poor shape and "out of date" is because you yourself left it that way. If that was a truly workable theory it would have verifiable predictions and compatibility with all prior observation and it would be eagerly explored. Scientists as a whole like to find anomalies and discrepancies; it is what keeps them in business. There is no "conspiracy".
    - dave333 2y ago
      Edits are removed unless they are published in well known journals which is fair enough for scientific results, but you cannot even update the page to state Mills latest engineering improvements or update factual information about the company.

terminalbraid 2y ago

They do sometimes. https://en.wikipedia.org/wiki/Electron_capture https://en.wikipedia.org/wiki/Electron_capture

fuzzfactor 2y ago
>Why do electrons not fall into the nucleus? It's always possible most of them already have done so :0 Seems to me the positive & negative charges would neutralize, and it would no longer be "matter" as we know it. Not anti-matter, just not actual matter by any stretch of the imagination. Which is what most of the universe actually consists of, not actual matter. Matter itself is extremely rare, few, and far between. Could be all there is left and can be perceived by those composed of it, are the things that can have a physical nature simply because their electrons haven't collapsed into the nucleii. Yet.

internet_points 2y ago

This was quite interesting, and at a level where I found I understood something new without being overwhelmed – I tried looking around the site for more, but the site itself has me confused as to where to start, is this part of a work in progress book? How do I get to the table of contents or start of the book?

mixmastamyk 2y ago
By coincidence I am currently watching this series, which explains this and a lot more: https://www.thegreatcourses.com/courses/einstein-s-relativity-and-the-quantum-revolution-modern-physics-for-non-scientists-2nd-edition https://www.thegreatcourses.com/courses/einstein-s-relativit... It is on Kanopy now, for “free” (local library pays). I think there’s a subatomic-particle specific course as well that is more focused.

alok-g 2y ago

I have come across the same 'explanation' multiple times but do not find it satisfactory. >> This "battle of the infinities" cannot be won by either side, so a compromise is reached in which theory tells us that the fall in potential energy is just twice the kinetic energy, and the electron dances at an average distance that corresponds to the Bohr radius. This "cannot be won by either side" isn't a good explanation of the problem. By saying "a compromise is reached in which theory tells us ...", the article seems going around the answer instead of actually telling the answer to the question. Assuming relativity is not invoked and given a finite size of the nucleus, what is actually bringing this situation of compromise? What is pushing the electron (or its probability cloud) outwards to counter-balance?

rcxdude 2y ago
The opposing effect is the kinetic energy of the electron: as it get squeezed into a smaller area its kinetic energy must go up, assuming energy is constant (a classical system would more or less be the same, think how an elliptical orbit speeds up as it gets closer to the barycenter, but a quantum mechanical system doesn't necessarily have a defined trajectory). The real sleight of hand in this explanation is it doesn't really explain why the quantum-mechanical electron doesn't radiate energy like the classical electron. That's a bit more subtle, but it's basically due to the fact that the electron is wave-like and confined within the atom (i.e. it does not have enough energy to escape the nucleus). This means that the wave-function has discrete solutions as a series of 'standing waves', which is what causes the quantization in quantum mechanics.
- alok-g 2y ago
  >> The real sleight of hand in this explanation is it doesn't really explain why the quantum-mechanical electron doesn't radiate energy like the classical electron. That's a big more subtle, but it's basically due ... This subtle part is exactly the piece that I am missing. So far, we have electron in an orbital. The orbital in itself seems stationary (standing waves), so it may seem nothing is accelerating. I presume that is not it for the answer. If it is, that still feels like, Oh, I solved Schroginger's equation, and it yields these standing waves for the solution, electron is not really having a certain position and momentum as the wave function hasn't collapsed, and thereby there is no acceleration for the electron to be radiating energy. Asking a total newbie question. I heard that QM has operators, so momentum also has an operator. Is there one for acceleration? Would it yield a zero? If so: I see Coulomb's force. Is there another force balancing it? Or is Newton's third law not valid anymore.

t8sr 2y ago

I don't like mechanistic explanations of particle physics - they're an attempt to relate what's going on to our macroscopic experience, but they usually fall apart when you look too closely. I find it much easier to understand the stability of hydrogen by thinking about ground states. If the electron in H could merge with the proton, they'd make a neutron. But a free neutron is not stable and decays in a few minutes back into a proton, electron and an antineutrino. With very large, proton-rich nuclei, eventually you get to the opposite situation where the ground state is one less proton, one less electron and one more neutron and the atom decays into that state by, you guessed it, an electron "falling into" the nucleus.

d--b 2y ago

To me the article says: the electron doesn't fall into the nucleus because we found an equation that says it doesn't.

vkazanov 2y ago
Yup. Half of physics is written just like this.
mr_mitm 2y ago
In the end, that's true for all why questions in physics. In the end, things don't have a reason for how they behave, they just do. The question of why only makes sense in a framework. Classical EM theory says electrons should fall into the nucleus, but they clearly don't. Asking why they don't is one step towards finding out about quantum mechanics, so it's a really important question to ask. Yes, at the end of the day, the answer is "because classical EM is wrong and quantum mechanics is right (or at least less wrong)". But there is a lot to learn along the way.

fithisux 2y ago

Second law of thermodynamics? The electron and the environment have the same temperature. If it falls, it emits energy warming the environment without consumption of energy. But this is impossible.

mr_mitm 2y ago
Single particles do not have a temperature. It's an emergent property of many-particle systems.
- fithisux 2y ago
  you forget the thermal bath
gus_massa 2y ago
Good question, but no. For example you can make a very similar system with a positron and an electron https://en.wikipedia.org/wiki/Positronium https://en.wikipedia.org/wiki/Positronium . It's stable for a while, and it has very similar properties and levels like an Hydrogen atom. So the "second law" should apply too. But it has a mean lifetime of only 0.12 ns (1.2E-10s). The second law consider also the properties of the materials. For example there are small bags with sodium acetate that are used as hand heaters https://en.wikipedia.org/wiki/Sodium_acetate#Heating_pad https://en.wikipedia.org/wiki/Sodium_acetate#Heating_pad https://www.youtube.com/watch?v=Oj0plwm_NMs https://www.youtube.com/watch?v=Oj0plwm_NMs You put them in hot water, the content dissolves, and you let them cold to room temperature. When you click the metallic part, they crystallize and release heat. Another example is connecting a small lamp to a battery. It release light and heat, specially if you can get an old incandescent light bulb.

rolph 2y ago

ELI5 version, why doesnt an elephant fall into a mouse? because the elephant wavelength is too long to fit inside the mouse, so it nestles around the mouse at S1 orbit. so, why doesnt an electron fall into a nucleus? because the nucleus is too small to encompass an electron wave.