okok, the i did searches and everything…but didn’t get the answers i want so…
What forces prevent the electron from crashing into the nucleus of and atom?
with referance to this page : http://itss.raytheon.com/cafe/qadir/q1189.html
I don’t see why a black hole is not possible…(i just don’t get what its trying to say:confused:
Thanks for any help in advance.
The Electromagnetic Force is what holds electrons near a nucleus but I’m not sure what keeps them away. However, I will say that Ernest Rutherford (who first came up with how an atom likely looks like…atoms cricling a nucleus) had the same issue with his theory. Theoretically a Rutherford atom would see the electrons lose energy and spiral into the nucleus (very quickly too). That obviously diesn’t happen so something was missing. Niels Bohr made the next step by finding that electrons could only ‘orbit’ a nucleus in very well defined shell. That is, an electron could orbit in Shell 1, Shell 2 and so on at defined distances from the nucleus but the electron could NEVER be anywhere inbetween (short of getting stripped from the atom completely). So, the electron simply cannot spiral into the nucleus as it would require a fractional energy state that simply isn’t allowed.
Of course, with sufficient energy you can pack an electron into the nucleus (such as in a Neutron Star). The electron is a quantum mechanical beast. That means it is subject to the Heisenberg Uncertainty Principle. The force resisting forming a neutron (and maybe this is the answer to you question) is Electron Degeneracy Pressure. As electrons are compressed into a very small volume their position becomes more defined. However, Heisenberg’s Principle says we can’t know the position AND the momentum of a particle such as this within certain limits. Since the position gets better known the momentum increases. This momentum creates a pressure to hold the electron away from the nucleus.
This is a Frame of Reference issue. As it says in the article if you ride along with the piece of matter at whatever speed the matter will still seem perfectly normal to you. A black hole is a black hole to EVERYONE regardless of their frame of reference.
Electrons sometimes (Very rarely) do crash into the nucleus. Its called inverse beta decay.
Anyways - this page explains it all - http://www.physlink.com/Education/AskExperts/ae265.cfm.
It’s an oversimplification to say that mass increases with speed. Momentum and energy most certainly do increase with speed, and they increase more than Newtonian physics would lead us to believe if the mass stayed the same. The usual way to resolve this (for physicists, at least) is not to say that the mass increases, but to say that Newtonian physics is not the whole story.
For that matter, there’s more than just mass involved in gravity: momentum flux and pressure and other stresses contribute as well. The full description of how all of these things interact to produce gravitational fields requires tensors, which I’m not going to try to explain here, but suffice to say that what a particle travelling at high speeds has is not what’s needed to form a black hole.
Thanks everyone
heres more stuff i don’t know 
I get the distinct impression that no one knows why electrons don’t fall into the nucleus, they just don’t. The electrons occupy energy bands surrounding the nucleus as described by Quantum Theory with the number of electrons in each band determined by the Pauli Exculsion Principle (I think that’s right) but all that is merely descriptive and I think there is no more fundamental explanation yet.
This isn’t too unusual. No one knows why massive objects attract each other either. You can say it is the force of gravity but that is just a name. Or you can say that the attaction is just an appearance resulting from massive objects bending space-time. But why do massive objects bend space-time?
Before we go on to reflect on other parts of the big picture, I think it should be pointed out that this is not necessarily the best explanation for how refraction works.
…uh…huh…so the best explanation would be…?
Simple… a denser medium simply slows the photon down. There’s no absorbing and re-emitting going on, as that would imply that a photon cannot travel through a vacuum (obviously, it can).
Think of it this way: You’re running through a lightly-wooded glade, practically going at full speed since the trees around you aren’t dense enough to provide much of a hindrance. But then you run into a really tangled thicket, and your speed slows down as you slowly pick your way through the brush.
That’s refraction. And if you have a line of people running parallel to each other through the forest, and the border of the thicket is at an angle relative to their direction… well, some will have to start pushing their way through the thicket sooner than others. When they come out the other side, those who entered the thicket at the narrowest spot would have gotten to the other side the soonest. This results in the once-parallel line taking on a bit of a curve.
Why would a photon being absorbed and re-emitted imply that photons could not travel through a vacuum?
Light travels at 3.00 x 10[sup]8[/sup] m/s in a vacuum. In a dense material light still travels at this speed in the interatomic vacuum. When photons encounters atoms they are absorbed and re-emitted which takes some amount of time slowing the propragation of light through a dense medium as measured by the optical density of the medium.
curving might happen in a medium with a density gradient but this is not typical.
A better analogy might be people riding segway scooters. They start on the parking lot next to the beach. If they hit the sand perpendicular to the edge they slow down but go in a straight line. If they hit at an angle one wheel hits first and slows down. The scooter turns toward the wheel that hit first until the second wheel hits. The same thing happens on exit from sand to pavement with the first wheel out speeding up.
The QED details of scattering whether they be in regards to reflection or refraction are rather long and tedious. Suffice to say when a wavefront of light hits a new medium, both reflection and refraction occur. We can model it classically using wave mehcanics. If you want to consider photons, you have to consider all the possible paths of the photons. Some of these paths involve reemittance through the medium (transmission). Some of these paths involve reemittance outside of the medium (reflection). I hope this provides an adequate explanation.
By the by, SPOOFE, you are adequately describing a classical model for refraction and reflection which is the most intuitive. It is, however, not as complete as QED.
As to
Feynman was fond of saying that physics only tells us what the rules of the chessgame were. It doesn’t say anything about why one is playing the game, so to speak. In reality we don’t know “why” anything in physics is going on or why anything is around at all. What we can say is that the laws of physics in its formulation of quantum mechanics conspire to make it very difficult for an electron to find itself in the nucleus of an atom, though that doesn’t mean it’s impossible for it to happen, as andy_fl pointed out.
Well, no. Whack-a-Mole’s explanation is pretty good:
More accurately, the momentum spread increases, which means in turn that the average of the square of the momentum increases.
Think classically for a moment: momentum = mV, momentum squared = (mV)[sup]2[/sup] = m*(mV[sup]2[/sup]). But mv[sup]2[/sup] is kinetic energy, so the electron’s kinetic energy is increasing as you squeeze it into a smaller region.
Note that combining a proton and an electron to make a neutron is not the same as simply squeezing the electron close to the proton.
Not necessarily “best”, but classically, the atoms of the refractive medium become polarized in response to the electric field, and that induces radiation that is 90 degrees out of phase with the original wave. The sum of the two is the slowed wave. (Of course, this happens continuously throughout the medium). The atoms near the surface also radiate energy back out from the surface. For reflection from, say, a mirror, the induced currents radiate 180 degrees out of phase of the incident wave, and exactly cancel the incident wave. They also radiate in the specular direction, leading to “reflection”.
IMNAP but agree and thats a great quote. Another way to “explain” why the electron does’nt fall into the nucleus is that if it did, you would’nt be here to ask this question. Or if you still were, you’ll ask why do electrons fall into the nucles ? This is called the anthropic principle or something like that.
This is getting more like GD material.
Something which Quantum Mechanics and Reltavity have in common (in my opinion) is that they don’t view the observer and the event (occurance, esistence, etc. etc.) as independent. It is intuitive to think that you can observe things without effecting them but its not true as per QM and Relativity. So in short everything happens because you interact and observe it so. What happens to anything when you are not observing is meaningless or not definable.
So the Universe exists, because you observe it. The universe is meaningless to you, if you don’t exist. (NOW is this a Science - Philosophy BVP ?? :D)
Your mean this one? “The Electromagnetic Force is what holds electrons near a nucleus but I’m not sure what keeps them away.”
Or maybe this one? “the electron simply cannot spiral into the nucleus as it would require a fractional energy state that simply isn’t allowed.”
WHASSATUSAY? HUH? Mass increases with speed? Can you expand on that please? I have never heard that before. As far as I have known, mass is constant under any conditions.
But I do not know everything about everything, just everything about sex.
Such a charmer DS. Is there something wrong with what I wrote?
Are you suggesting the electromagnetic force does not hold atoms together? Or do you have issue that I said I don’t know what keeps the electron away?
As to stating that I don’t know what keeps the electron from spiraling into the nucleus I think it is a fair statement. I don’t know. What followed in my post was speculation that Zen Beam seemed to confirm. It seems clear from this thread so far that what keeps the electron from getting sucked into the atom isn’t quite common knowledge. If you’re smart enough to know then good for you…maybe you’d like to share it rather than taking me to task.
Electrons do crash into the nucleus of atoms on occasion as has been stated. It is my understanding though that quantum mechanics dictates that electrons (among other subatomic beasties) can only lose energy in discrete, complete energy packages (or quanta…look at that…quanta – quantum, who’d have guessed :rolleyes: ). When an electron changes orbits from one shell to another it does not travel between the shells. That is, you’ll never see an electron between shell 1 and shell 2 (for example). It basically stops being in one place and appears in the next place. If it is going up an energy level it must absorb precisely the right energy to get it there. Anything else (basically allowing for a fractional energy unit to remain) won’t work. It the electron jumps down a shell it releases a photon that is again a distinct quanta of energy. It cannot jump and lose 1.5 photons of energy.
IANAPhysicist so perhaps I have something wrong here. Feel free (anyone) to point that out but maybe, DS, you’ll consider being more constructive in your thread next time and let us all in on your vast store of knowledge rather than only bashing another poster.
Such a charmer DS. Is there something wrong with what I wrote?
Are you suggesting the electromagnetic force does not hold atoms together? Or do you have issue that I said I don’t know what keeps the electron away?
As to stating that I don’t know what keeps the electron from spiraling into the nucleus I think it is a fair statement. I don’t know. What followed in my post was speculation that Zen Beam seemed to confirm. It seems clear from this thread so far that what keeps the electron from getting sucked into the atom isn’t quite common knowledge. If you’re smart enough to know then good for you…maybe you’d like to share it rather than taking me to task.
Electrons do crash into the nucleus of atoms on occasion as has been stated. It is my understanding though that quantum mechanics dictates that electrons (among other subatomic beasties) can only lose energy in discrete, complete energy packages (or quanta…look at that…quanta – quantum, who’d have guessed :rolleyes: ). When an electron changes orbits from one shell to another it does not travel between the shells. That is, you’ll never see an electron between shell 1 and shell 2 (for example). It basically stops being in one place and appears in the next place. If it is going up an energy level it must absorb precisely the right energy to get it there. Anything else (basically allowing for a fractional energy unit to remain) won’t work. It the electron jumps down a shell it releases a photon that is again a distinct quanta of energy. It cannot jump and lose 1.5 photons of energy.
IANAPhysicist so perhaps I have something wrong here. Feel free (anyone) to point that out but maybe, DS, you’ll consider being more constructive in your thread next time and let us all in on your vast store of knowledge rather than only bashing another poster.
I mean the one I quoted and expanded upon. Maybe you missed it…