Feynman and Perpetual Electron In the paragraph 1–2 "Matter is made of atoms" of the first Volume of his lectures, the great Feynman says that electrons are in a perpetual motion.
Now, i'm new to physics and i don't know quantum mechanics, but for what i understood about Classical Mechanics, perpetual motion is not possible (at least for the moment :)  ).
Now, what did Feynman want to mean saying that electron are in  perpetual motion ?
 A: First off, perpetual motion is possible. In fact, perpetual motion is sort of the "default" and it is only interactions that will cause an object in motion to stop. Think of Newton's laws, "an object in motion will stay in motion" - or maybe think about throwing a rock in space (it will remain at the same speed that it was thrown at until it hits something in space).
Things slow down because of friction. Now, one way of rephrasing your question might be "what is friction at a quantum level, and if electrons are spinning around the neucleus of an atom, why don't these electrons experience any friction and slowly fall to the center of the nucleus?"
Well, there's some different ways of answering this. One way is talking about discrete energy levels. At the quantum level, there are some systems that can have "discrete" energy levels. This means that energy the system can have only have very specific values, and cannot be in a continuum. This is the case for an electron that's trapped by a nucleus of an atom. If a satellite in space hits a little bit of dust, its orbit (or energy) will lower very slightly - but this is impossible for quantum states. Instead they have a chance of lowering by one of these discrete intervals. 
Another way of talking about this is discussing electron spin. We can keep track of how the electron is orbiting around the nucleus (more precisely, we can keep track of the "wavefunction" which lets us know the probabilities associated with its position and speed.). This orbiting behavior is called angular momentum. But we see that even in situations when the electron is on its own (and not orbiting something), it still seems to have some "angular momentum". This is very perplexing because the electron does not even seem to have any size, so it's hard to even argue that it can "spin" in the convention sense. None the less, we believe that this angular momentum is an inherent property of the electron, and have given it the name "spin." 
This is most likely what Feynman was referring to, that electrons always, no matter what you do to them, will have a fixed amount of this special angular momentum called "spin!"
A: In this section, Feynman did actually refer to "particles" being in perpetual motion not to "electrons". He meant by this that even in a stationary object (say a tennis ball on a table) consists of many atoms in perpetual motion "wiggling" around even thought the ball is not moving. Macroscopic objects could lose their energy due to friction but the very small particles in comprised off keep on wiggling.
A: A perpetual motion machine is something that can work indefinitely without any energy source. Such a machine is not possible as it violates the second law of thermodynamics. 
What Feynman describes here is somewhat similar, but it is possible because of the time scale of the observation. Given a short enough time scale a system in motion will appear to move without exchanging energy with its surroundings, and for that time scale it can be considered to be in perpetual motion. However if you wait long enough you will observe that the system indeed exchanges energy with its surrounding and such a perpetual motion, that is one without exchanging energy with the surroundings, is not possible. 
A: Since he was talking specifically about atoms being in perpetual motion, I believe the idea is essentially Heisenberg's Uncertainty Principle. 
Now Feynman did not refer to that here. His point was, rather, that as a matter-of-fact atoms are always in motion, flying about and vibrating against other atoms and so on. But the reason they are always in motion is down to the uncertainty principle. So I think that was in the back of his head when he said that.
A rough explanation: since the atoms are interacting with their environment (other atoms, light, and so on) they are effectively localized by it i.e. they have a rough location. This location isn't precise, there is some uncertainty about where they really are. Correspondingly, by the Heisenberg Uncertainty Principle, they also must have a degree of uncertainty about their momentum, hence about their velocity. But this means that their description must include states with non-zero velocity - since it's possible their velocity is some non-zero value, the state "moving at that velocity" must be one of the states the atom could be in. This guarantees that atoms, or really any quantum system, is never fully "at rest". There would always be some motion and jiggling on-average, as the possible-states that include motion contribute to that average. 
