Sarah Rogers asked:
Why don't electrons stick to protons if there’s electrons whizzing around the outside of an atom and the protons are the positive bit in the middle? Why don't the two just collapse in on each other?
Okay. In a very simple sense, they do stick to protons as much as they can. They're attracted to protons and so, they form atoms. So an atom is essentially an electron stuck to proton. What you really ask is why don't they get any close than they do? It’s all basically to do with the fact that electrons – in fact, everything- has wave properties. And the electron’s wavelengths are about a similar sort of size of atom and that’s the reason why atoms are that sort of size over the order of the wavelength in electron. And so, you can't really compress a wave any smaller than one or few wavelengths. And so, the electron can’t get any smaller than that without actually changing its properties entirely. So, it can't actually get any closer to the proton in the centre of the nucleus than it does and so, it’s stuck as close as it can. You can cause – if at very high pressures-, you can cause electrons essentially to react with protons and turn into neutrons and this is what happens in neutron stars. A neutron actually isn’t stable just lying around, in the atmosphere or in a vacuum. It decays in about 14 minutes into an electron and proton sort of forms into a hydrogen atom.
Sarah Raphaella Rodgers asked the Naked Scientists:
It has to do with the uncertainty principle. Because the electron cannot have a defined position in the nuclei of atoms means that it must occupy every other space within the atom in a wave of possibilities. If the electron was positioned with great certainty within the nuclei of atoms, their momenta becomes infinitely uncertaint. But instead, they seem to have energy-orbits inside of atoms which determine the chemical struture of the universe. Another interesting thing to note is that electrons could not be in the center of atoms, because if they where, matter would drastically sink in size.
When I was 16 people like Einstein and Schrodinger were reassuring us that we need not worry; the Copenhagen interpretation and Quantum Theory were too weird to make any real difference. Now we are a half century into Physics becoming Quantum theory to the exclusion of reality even. Causality was abandoned because Quantum theory can't survive if we insist upon it.
Principles do not cause things; principles merely describe the happenings. We tend to think of principles and theories as causes; they can not be causes; their use is in describing the happenings. I'm just trying to keep folks honest. Vern, Sun, 1st Nov 2009
Just in case you would like an example of the exclusionary principle ordinary in nature, it even happens when two electrons come close to each other in space. It's closely related to the wave function, which is actually one main reason why the electron does not fall into the nuclei of atoms; specifically because they are not located to any particular region of space, which would induce a collapse of their superpositioned states. They are ''arranged'' within their superpositioning because of energy levels. But the exclusion principle is not the prime cause of either the wave function or the fundemental reason why particles do not fall into the nuclei of atoms. Mr. Scientist, Sun, 1st Nov 2009
I knew i was right. I came across this convo on the net:
If you like to think that Quantum theory represents reality you have to invent excuses. Quarks can not exist outside nuclei, for example. Electrons dance to the uncertainty tune, etc. To me it is much easier just to accept reality as it presents itself. Vern, Sun, 1st Nov 2009
But it seems that we hve experimental evidence for these conclusions. If anything, i think reality has shaped physics for the larger part, not so much intentionally the other the way. Mr. Scientist, Sun, 1st Nov 2009
We can measure decoherence, which is the gradual collapse of the wave function in wave-states of matter. We may not be able to directly observe the transformation because in doing so we disturb the p-field ''probability-field''. But, we know the collapse must occur as an actual transition from having matter acts as waves and then suddenly not. Mr. Scientist, Sun, 1st Nov 2009
But there is very little else that can happen. Given the intantaneous change from wave to particle-nature means that there is little room other than to say there is a sudden collapse. All models have agreed with observation. Mr. Scientist, Sun, 1st Nov 2009
We don't know that there is an instantaneous transition from wave to particle. We know that there is an instantaneous transition of a previously unknown state to a known state at the time of observation. We have not yet figured out how to know the state of the previously unknown state.
Though, we have what we need to know about this state, and that is it acts in every way like a particle when its not being observed. Mr. Scientist, Sun, 1st Nov 2009
I can't argue with the success of Quantum theory. It is the only theory I know that demands a change in reality when reality does not agree with it. Vern, Sun, 1st Nov 2009
I meant a wave by the way in the passage above - oops. Mr. Scientist, Sun, 1st Nov 2009
I don't mean to be contrary. I just need to explore every possibility that might offer experimental evidence that my vision of a photon is not reality. As far as I can determine the double slit experiment supports the vision. If I did not have the photon defined so that it must produce the observed results by cause and effect, I might fantasize some magical wave-particle duality.
I wouldn't be as bold as to suggest you cannot explain physics, if indeed it is the correct description of a photon. Physics is not easy to explain, whether it being a pet-theory or not. Mr. Scientist, Mon, 2nd Nov 2009
I have to keep reminding myself what my goal is here in this forum. It is not to point out weaknesses in Quantum theory, and it is not to promote my pet concepts. It is simply to remind folks when common misconceptions are promoted. In this case it was the misconception that there is experimental evidence that quantum states occur at observation time. Vern, Mon, 2nd Nov 2009
Fair do's. Mr. Scientist, Tue, 3rd Nov 2009
It would really be interesting if there was experimental evidence; maybe a last instant change in one of the states that is reflected in the other. I know that has been tried. All the attempts I know about failed. Vern, Tue, 3rd Nov 2009
Vern - You wrote: "There is a cause for quantum phenomena just as there is a cause for uncertainty."
I have not yet signed on to quantum units other than the quantum of light. That is because I have a speculative cause for How Come The Quantum that assigns the cause to a property of the photon. I guess when you dwell on a subject for a long time it kinda sets in your mind and makes it difficult to contemplate another scenario for the action in mind.
Heisenberg uncertainty principle restricts measurement capabilities, not what objectively happens there - I completely disagree with such explanation by eye shutting ...
Yeah, reading it I agree with homely physicist. You can't ignore the Pauli exclusion principle as that is what defined matter macroscopically. Although the Heisenberg exclusion principle is also important, but there depending on how far you want to take it. As a way of thinking or as a real property of the universe. yor_on, Sat, 2nd Feb 2013
Schrodigner picture represents complex electron dynamics as a simple wavefunction - Pauli exclusion principle only says that there cannot be multiple repelling particles in the same dynamical state.
Doesn't matter (ahem:) if they vanish meeting Jarek, well, as i see it :)
But there are some weird effects to it, thinking of it from the probability of finding a electron in a atom. The electron (in its orbital inside the atom) is from the point of probability 'smeared out' as I understands it. The measurement alone must then be the definition of 'where it is/was'
The short answer is that a "proton and electron stuck together" does happen, in a neutron.
Part of the hydrogen electron's life *is* lived in the nucleus: its wavefunction square modulus is non-zero there; it has even the greatest value, there!
Indeed the simplest Schrodinger equation leads to that the maximum of electron density is exactly where the proton is ... but this model is just one point charge in potential of another fixed point charge - greatly simplifies the real physics. In the real world electron being in the same place as proton would mean that they create neutron, but it would require relatively huge energy: 782keV. So including strong force holding baryons together would rather remove this density maximum from the Schrödinger's ground state.
Be that how it might Jarek, but your question about measurements is one that has been on my mind too, but in the form of 'observers', and of course 'consciousness'. And it is important to define it I think. My own view of it is that as long as you define a 'observer' as 'something' being in a interaction with 'something else' the Copenhagen interpretation makes sense, and HUp seems then to be a sort of ultimate answer on the very small plane. If you on the other hand define it such as a 'measurement' always must involve something conscious, deciding to make that measurement? Then all of your objections hold water to me. yor_on, Sun, 3rd Feb 2013
As for bosons and fermions?
The need of consciousness of observer makes it extremely mystical ...
I have to admit to have understood nothing of what you have written, maybe it's outside of my knowledge possibilities.
What you don't understand? I have only pointed out that this density maximum in the center is a nonsense from the point of particle physics (binding proton with electron would cost m_n-m_p-m_e=782keV). This simple Schrödinger equation ignores much more physical aspects, but still gives impressively good agreement, even in nuclear shell model - it is because the quantum ground state is something extremely universal, also from thermodynamical point of view as Maximal Entropy Random Walk shows (these papers and my last PhD thesis was about) ... Jarek Duda, Sun, 3rd Feb 2013
Jarek, what lightarrow mean is that you have had a long hard thinking about this, with friends presumably. We are new to the subject, and it might well be that we miss what you consider obvious. You keep coming back to the quantum ground state btw, can you expand on how you see that? One universal ground state, is that what you mean? And yes, spin states are a mystery to me :) How they can define matter from 'bosons'. So does your model simplify it, or explain them?
...and this is quite simple to understand....and this is the less simple part lightarrow, Mon, 4th Feb 2013
Probability density of the quantum ground state is universal from QM point of view because other states are excited - have higher energy and so want to release this energy, deexcitating down to the ground state - so this is kind of thermal equilibrium state (in 0K).
So you do this from assuming a even probability 'density' to the universe? "we should assume uniform probability distribution". So I got it all wrong :) when I wondered if you were trying for a 'classical' (Newtonian?) definition. I will have to read up on the maximal uncertainty principle, it's new to me. As for a uniform probability it makes sense to me, as long as we ignore interactions, if that is how you mean? I'm good at jumping to conclusions :) And I like new ideas, and yours are new to me.
In terms of random walk, one of equivalent formulation of maximal uncertainty principle says that having absolutely no information about what trajectory the object will chose, we should assume uniform probability distribution among all possible paths - it is MERW. Another formulation is by maximizing entropy.
K will do.
This magnet toy is a good demo for a hydrogen atom. https://www.youtube.com/watch?v=LyvfDzRLsiU#aid=P8fZ2oSGqsg jccc, Mon, 12th May 2014
The fact that atoms don't collapse just shows that the classical electron-proton model is inadequate. There is no "why" in nature: stuff happens, and the best we can do is to generate predictive models of what happens. The classical model of electrostatics works pretty well for widely separated charges but just doesn't describe the behaviour of electrons in an atom - and there's no reason why it should.
Science is all about applying the scientific method to come up with models of nature. The key term (for this discussion) is models. Science doesn't deal with coming up with a fundamental "real" cause for everything. All we as scientists can do it to come up with accurate models and then leave it to philosophers to argue over whether the model itself is reality or whether it is simply a model of some deeper underlying reality.
I never posted ideas like "I think an electron can stick to a proton".
Force is caused by a change in momentum which is in turn caused by the exchange of particles or fields. The speed at which one object can exert a force on another is determined by the speed of those particles or fields. The upper speed limit to anything we know of is the speed of light, since both fields and particles obey special relativity. Of course, forces can travel slower.
And I don't understand why you don't want to understand that electrons in an atom are not little balls and so to describe their behaviour you have to use quantum mechanics.
how can they not attract each other and stick together?
The energy involved in electrostatic interactions between electrons and protons is around a few electron-Volts - the level of energy that is involved in chemical reactions.
"So three reasons protons don't routinely capture electrons:
This brings up a question about neutron stars. Do they have a magnetic field? If so then is it simply electrons that cause it? The neutrons being neutrally charged are unlikely candidates. This would make the field mono-polar. jeffreyH, Fri, 4th Jul 2014
I don't know how important this is for neutron stars, but neutrons in atomic nuclei are certainly magnetic--both protons and neutrons have "nuclear spin" that results in a small magnetic field. I don't know to what extent the spins would arrange themselves to cancel out in a neutron star, but it would only take a small imbalance to have a fairly large magnetic moment. (A neutron has a spin of magnitude 1/2, some of the most out-of balance, but still stable nucleons have a spin of 7/2. Some more extreme nuclear states only last a short while (110Ag has a 12/2 nuclear spin, but a half life of only 253 days, and 43Sc has a 19/2 nuclear spin, but a half-life of only 450 ns!) chiralSPO, Fri, 4th Jul 2014
the only stuff inside a molecule is the electrostatic charge and magnetic forces and these need to balanced.
I rather to be a neutron than an electron, how about you? jccc, Sun, 6th Jul 2014
Well, here is something to read about this: http://www.wired.com/2014/06/the-new-quantum-reality
From the previously mentioned article.
How do you calculate "10^6 nucleus energy" out for e– + p+ → n ??
I don't have calculation. I am thinking energy is stored within atoms, not nucleus. To release all the energy, we must break down nucleus force field to destroy the atoms.
JCC, I think some of the confusion here has to do with trying to think classically about things on the atomic scale (and especially at the nuclear scale). Picturing protons and electrons as little charged balls that move like macroscopic balls will naturally lead to paradoxical and contradictory predictions. chiralSPO, Fri, 11th Jul 2014
The experimental result which first showed the distribution of charge within the atom was conducted by Geiger & Marsden in a 5-year period around 1910.
For some time I was puzzled by what seemed to be a reciprocity failure between electron jumps away from and towards the nucleus. I reasoned that if an electron was attracted towards the nucleus, it should require more energy to move it away from the nucleus than towards it. The conclusion I eventually reached was that as this was a quantum leap, the electron could not be said to be anywhere when it was not occupying an energy level. If the electron could not be said to be anywhere, it could not be using or exchanging energy. Thus it made no difference which way it was going. The energy necessary to accomplish the jump would be the same.
Quote from: evan_au
2 H2o + 4e = o2 + E