I have been loving the new Cosmos series which has excellent writing, mellifluous voiceovers by a wonderful host, Neil deGrass Tyson, spectacular special effects and visuals, and which has made very few errors, too, at least until last night. In an attempt to explain how atoms absorb and release photons of light they created an animation of atoms. First their depictions were a bit sci-fiish and bizarre but they settled upon a single hydrogen atom with a fuzzy, jittery large spot representing the nucleus of the atom and a smaller, jittery blob of light representing the electron. There is the problem of scale, which I have written about before. It is impossible to show these particles at their actual scales and at their actual distances (even blown up as they were in the animation. The human eye is not capable of that feat, so I give them a pass on the two particles being overly large and overly close together. It is, after all, T.V.
“This would have been a quite acceptable description if it were, say, 1922.”
But then they goofed. They then showed the electron in orbit around the nucleus, one of , they said, many possible orbits. And that the electron, when it absorbed or released light energy, in the form of a photon, would leave one orbit and end up in a different orbit. They showed the glowing orbit (looking like a vapor trail the electron was leaving behind) disappearing and a new orbit appearing elsewhere. This is the so-called “quantum leap.”
This would have been a quite acceptable description if it were, say, 1922.
Since then, though, we have learned a great deal, specifically that there are no orbits. We do not know what atomic electrons are actually doing but we know what they are not doing and that is orbiting the nucleus. They are not in circular orbits. They are not in elliptical orbits. They are not in loop-the-loop orbits. There are no orbits! The locality of an atomic electron can be described but only as a probability map, e.g. it has a high probability of being here, and a low probability of being there, etc. These maps are called “orbitals” to signify that they replaced the orbits of earlier thinking. These orbitals are “unbounded,” that is they have no outer boundaries. A consequence of “unboundedness” is that all possible orbitals of an atom overlap. When an electron in an atom absorbs or spits out a photon of light energy, it does not change position in no time. It simply changes its probability map and since they all overlap (albeit in many cases only a tiny bit) each electron doing this is in its old orbital and its new one at that exact moment. What the electron does from that time forward is to exist as described by its new map rather than its old one.
A “quantum leap” (damned poets) is an instantaneous leap in energy, not in position. In human beings it is like an instantaneous change in mood; like if you were having a bad day but then got the news that your child finally was having another baby after trying for years: bingo, happy days are here again! This mood change does not require a change in position.
And neither does a quantum leap.
There is plenty of quantum wierdnesses to amaze the audience; they do not need to dredge up one hundred year old misconceptions to highlight them. For example, the fact that only a set of fixed energy changes are possible for any element’s atoms. If a photon races through an atom and does not correspond, exactly, to the energy difference between two of that atom’s orbitals, it just keeps going. Nobody knows (yet) why or even how those energies are fixed into the values the are or how the electron can tell whether or not to take on that photon. There is nothing like this behavior in the macroscopic world in which we live.