I was reading about the Rutherford atomic model which said that electrons revolve around the nucleus the way the Earth and other planets revolve around the sun.  This model was,however,shunned as it did not accommodate the fact that when charged particles accelerate,they emit radiation,lose energy and fall into the nucleus.This does not happen in the case of the earth as it is electrically neutral.  But it does comprise  charges.   So why don't the individual charges emit radiation ?  What difference does it make if the charges are moving alone or in vicinity of other charges?  How can charges differentiate if they are moving with or without charges?(Which would lead them to either emit or not emit radiation)  P.S- A simple answer would be appreciated as I am not familiar with Maxwell's theory of EM radiation.
15737
I'm having trouble understanding the simple "planetary" model of the atom that I'm being taught in my basic chemistry course.   In particular,    I can't see how a negatively charged electron can stay in "orbit" around a positively charged nucleus. Even if the electron actually orbits the nucleus, wouldn't that orbit eventually decay?  I can't reconcile the rapidly moving electrons required by the planetary model with the way atoms are described as forming bonds. If electrons are zooming around in orbits, how do they suddenly "stop" to form bonds.     I understand that certain aspects of quantum mechanics  to address these problems, and that there are  of atoms. My question here is whether the planetary model itself addresses these concerns in some way (that I'm missing) and whether I'm right to be uncomfortable with it.
48898
This question arose in a seminar today about the solar wind... This is my vagueish understanding of the problem - please correct if you see errors! The 'classical' picture of atmospheric electricity is that the Earth as a whole is neutral, but that thunderstorms maintain a voltage of around +300kV at the electrosphere with respect to the Earth's surface, with a current of around 1 kA slowly discharging around 500 kC of total charge separation. The solar wind is supposed to neutralise any net charge that might be there between the Earth as a whole and the solar wind. However, positive and negative charges in the solar wind are differently trapped in the van Allen belts, from which they can then descend to the Earth's atmosphere, which implies that a net charge can be developed due to this differential leakage. This begs the question of whether there are any estimates of the total net charge. I've hunted in the literature but have found little useful material other than Dolezalek's 1988 paper:  Can anyone offer an explanation, or point me to some more relevant papers?
52898
I have read about an electron making a transition between two energy levels and electromagnatic radiation will be emitted. The problem is how and why e.m radiation is emitted.
37707
I am a n00b to physics. What physics I know comes from high school and popular science books.  At school we were taught about atoms and what make up atoms, but we weren't actually told what the particles were!  So sure an atom has electrons orbiting around a nucleus made of protons and neutrons, but what exactly is an ?  And if we don't know, how can we fire them from guns, like they do in experiments ... etc  Any clarification on this would be great.
57073
Electrons   have a much bigger charge density as the protons (and especially lead nuclei), aren't compound particles as the protons (and especially lead nuclei) are able to get a much bigger energy with the same fields as the protons (and especially the lead nuclei).   Why seems common for the big colliders after the LEP to use protons (and much bigger nuclei)?  Reacting comments: Yes, to get good experimental data about quark matter they need a lot of hot quarks (= collided big nuclei). But to create new particles, the energy per degree of freedom needs to be maximized, and this maximum is at the single particle with the highest charge density, and this is the electron.
11743
I'm tutoring high school students. I've always taught them that:     A charged particle moving without acceleration produces an electric as well as a magnetic field.   It produces an electric field because it's a charge particle. But when it is at rest, it doesn't produce a magnetic field. All of a sudden when it starts moving, it starts producing a magnetic field. Why? What happens to it when it starts moving? What makes it produce a magnetic field when it starts moving?
53800
I was watching the Cosmos documentary where Neil deGrasse Tyson explained how certain energy photons get absorbed by an atom, which causes the electrons of that atom to climb into a higher energy state.  He then says that an atom produces a photon when those electrons drop to a lower energy state, but that we don't know why this happens. I understood that as 'we don't know what triggers this to happen'.  Is that true? And if so, are there any feasible theories that explain this phenomenon?
52096
In Synchrotrons I think they use microwaves to accelerate the electrons bundles that fly through-how does putting a microwave through a cavity accelerate an electron? I know that the Electric and Magnetic fields could and do have an effect on the electron, but if the radiation is moving parallel to the electron, wouldn't the force be perpendicular? Also, how exactly does the microwave radiation look in the vacuum chamber? Are the two ends constant nodes?
26661
I know this isn't the right place for asking this question, but in other places the answers are so awfull.. I'm studying eletricity, so, I start seeing things like "charges", "electrons has negative charges",etc. But I didn't quite understand what charge is. I search a little bit on the internet and found it related to electromagnetic fields, then I thought "negative and positive may be associeted with the behaviour of the particle in the field, great!", but the articles about e.m. fields already presuppose "negative" and "positive" charges. In other places, I see answers relating charges to the amount of electrons/protons in an atom, but if that's right, the "negative" electron is an atom without any protons? What about the neutron? So, my questions are (1) What are charges; and (2) How a particle can "be" electrically charged. What does that really mean? Thanks for your time.
111205
When I was in school, I learned (from Democritus) that an atom was  similar to a solar system, with the nucleus being the sun, and the  electrons being the planets. Of course, there are some differences:    The "sun" isn't a single entity, but a collection of protons and nuetrons.  Two planets can share an orbit (which might be possible in a solar  system too, but it doesn't happen in our solar system).    Is this model still valid? Here are my problems with it:    In "Surely You're Joking, Mr Feynman", Richard Feynman implies  that electrons are more a theoretical concept than real objects.  I have trouble understanding atomic bonds (ionic and covalent) in  this model.  I also have trouble understanding electron "orbit jumping" in this  model, as well as several other things.    Is there a better model for someone learning this for the first time?
43336
Let's say we have a emitter, emitting light that has frequency f, less than the threshold frequency of a metal.  If you leave light shining onto that metal, for long enough, does the energy of the individual photons accumulate, on the electrons, so eventually they will ionize, or does this not happen? What am I missing?
103221
According to my text book:  The Lorentz Force F on a charged particle moving in an electromagnetic field is given by:  $$F= qE + q(v\times B)$$  then it states that "it is to be pointed out that only the electric force does work, while the no work is done by the magnetic force which is simply a deflecting force."  How can this by true won't the the magnetic force have a considerable magnitude, will it now impart kinetic energy to the charge? Any explanations will help a lot. Please keep the terminology simple, thanks.
77845
This was a question on a worksheet during my first week in a class on Electromagnetism. The answer is essentially:     No. Life would be no different if electrons were positively charged and protons were negatively charged. Opposite charges would still attract, and like charges would still repel. The designation of charges as positive and negative is merely a definition.   But how would we have negative charges within the nucleus? Taking a look at the , it seems that down quarks are required in this new "negative proton" to help with creating the pion to "transmit a residual part of the strong force even between colorless hadrons".  I tried to set out and try to find a particle with (-1) charge with a down quark (by going through this ) but all the particles are not stable with the exception of two unknown:   Bottom Xi Baryon Double Bottom Xi Baryon   Assuming one of the above are stable, could the strong force act between one of them and a neutron, implying its alright to have a negatively charged nucleus?  Edit: If it wasn't clear, my question concerned whether or not there existed stable baryons of $-1$ charge with down quarks that could "replace" the proton.
62802
An excited electron loses energy in the form of radiation. The radiation constitutes photons which move at a speed $c$. But is the process of conversion of the energy of the electron into the kinetic energy of the photon instantaneous? Is there a a simple way to visualize this process rather than math?
40574
How does  work? I'm wondering why matter and antimatter actually annihilates if they come into contact. What exactly happens? Is that a known process? Is it just because of their different charges? Then what about neutrons and anti-neutrons? I guess that would be about their quarks, but wouldn't it be very unlikely what all of their individual quarks would actually touch the anti-quarks of the other (anti-)neutron at exactly the same time?
22694
So I've been looking into particle-antiparticle pair production from a gamma ray and don't understand one thing.  Let's say I have a 1,1 MeV photon and it hits a nucleus - electron-positron pair with some momentum will be created and the nucleus will probably get some momentum as well because of the impact.  But why does the photon need the nucleus at all? Why can't it just fly through space and suddenly, with some probability, change into a electron-positron pair with momentum? I see that the momentum of the system wouldn't be conserved but I don't really understand how the nucleus helps it.
33065
I was wondering why electrons orbited protons rather than protons orbiting electrons.  My first thought was that it was due to the small amount of gravitational attraction between them that would cause the orbit to be very close to the proton (or nucleus). The only other idea that I would have is that the strong interaction between protons and neutrons have something to due with this.  I have heard that the actual answer is due to something in QM, but haven't seen the actual explanation. The only relation to QM that I can think of is that due to a proton's spin and the fact that they are fermions, the atomic orbitals should be somewhat similar. Do protons have the same types of orbitals, that are just confined by the potential of the strong force?  A related question that came up while thinking of this being due to a gravitational interaction: do orbits between protons and electrons have a noticeable rotation between each other (as the sun orbits the earth just as the earth orbits the sun), or is any contribution this has essentially nullified by the uncertainty of the location of the electron (and possibly proton as well)?