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Electrons are supposed to be moving around the nucleus in orbits. In tat case they emit electro magnetic waves which makes the electrons lose energy. So as time passes,shouldn't the atom one day collapse??
Electrons that are bound to atoms possess a set of stable energy levels, or orbitals, and can undergo transitions between them by absorbing or emitting photons that match the energy differences between the levels.
An electron orbit is not as simple as it sounds, as the electrons are in a quantum state they can be anywhere within that "orbit" at any time.
The energy levels electrons can located in is therefore more like a series of "shells" surrounding the nucleolus.
This was one of the very problems that launched quantum mechanics. The early pioneers had indeed asked the same question and using classical physics (i.e. in this case relating to Kepler's laws of planetary motion, and Newton’s Laws of motion) it is predicted that the electrons do “fall” into the nucleus.
Thus the theory and practice did not tie up, and so the idea was born that the electrons were “locked” forever in one “state” until an external source of energy arrived that could knock them to a different state. This is a “quantum jump” and is an example of a term often used in modern language to mean a “big change” (etc.) but actually means the almost infinitesimal change from one quantum state to another.
So, in classical physics we would see the slow orbital decay and collapse of the atom, in quantum mechanics we see no decay, but discrete jumps from one state (orbit) to another.
As Fruit Bat /\0/\ says, these jumps involve photons, and the reality is not really “orbits” but probability waves where the particle (i.e. not just electrons) is “everywhere at once”, but has a variation in probability of where it “really is”. Even more bizarrely, it (they) can be in several places at the same time; and my favourite quantum effect is so called “tunnelling”. Quantum tunnelling occurs when the particle does not have enough energy to move from its state, but suddenly finds itself in the next state. This is like you being stuck at the bottom of a well, with no hope of jumping to the surface, but suddenly finding yourself at the surface. An apocryphal tale is that a physics student was drunk and drove his car off the road at a hump back bridge. He argued that rather than lose control, the car must have tunnelled through the bridge and ended up in the field. Apparently, the judge did not believe this tale.
Although all this sounds fanciful, (the quantum physics not the student!) you may be surprised that you probably use the result of all these effects every day. The most obvious example is LEDs (light emitting diodes) that are found everywhere in electronics. Electrons changing state within them is the mechanism to release photons, which you see as light. The tunnelling effect is used in tunnel diodes, another electronic device.
Unfortunately, everything gets really complicated and if you are really interested, some Googling and a few years study should answer further questions!
The orbit of an electron generates an electromagnetic wave only when its plane rotates, otherwise it just produces a steady EM field.
It may help to consider a permanent magnet at rest. Its electron planes share a common direction, and so show a steady external field. If the magnet is then rotated to continually interchange pole positions, an EM wave is generated.
The external force needed to do this provides the energy and angular momentum of the wave.
One small change to Wilham’s post:
“...otherwise it just produces a steady EM field.”
I suggest moving electrons (in the sense of those orbiting at the atomic level) generate a magnetic field, not an electromagnetic wave. An oscillating electric current (e.g. the movement of electrons, as generated by a radio frequency transmitter) would generate an EM wave.
There will be plenty to test mans ingenuity in surviving before that happens
Well, thats sorted that out, Thanks lads....
I wrote my piece while my dinner cooked and later was pleased to see your earlier and more detailed posting.
You are astute in your observation, but I intended what was put, also I wrote 'field' not 'wave'.
In rough terms in this context a field indicates influance at a distance, and a wave is a moving variation of the strength of a field, often periodic.
The magnet in my post when not moving exhibits a static (unchanging) magnetic field.
A plastic comb rubbed with silk can pick up paper, and shows electrostatic field.
Simple experiment makes it apparent the the two properties above are independent. However, deeper examination shows that a quick change in the strength of either produces the same thing, what we call an electromagnetic wave. James Clerk Maxwell (google?) summed up this dynamic property as four equations in the 19th century.
The quick way to look at it is to say it's just a property of the electron.
morddwyd's comment reminds me of the recent? prognosis that the universe will expand for ever and ultimately become vast, cold and dead. I find this rather alarming, what will we do then?
My brain hurts.
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