# How does an electron go between two points, without crossing the space inbetween? **URL:** \ **Category:** Factual Questions\ **Created:** [September 26, 2003, 5:30am UTC](https://boards.straightdope.com/t/how-does-an-electron-go-between-two-points-without-crossing-the-space-inbetween/203919 "2003-09-26T05:30:22Z")\ **Posts on this page:** 6\ **Page:** 2
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [September 26, 2003, 8:44pm UTC](https://boards.straightdope.com/t/how-does-an-electron-go-between-two-points-without-crossing-the-space-inbetween/203919/21 "2003-09-26T20:44:33Z")
> [@](#): > > \*Originally posted by Roches \* > **By “shell”, do you mean “energy level”, the set of electrons having the same principal quantum number _n_? (The numbers of electrons is the same, so I think that’s what it is…) The term “shell” seems like a simplification of the quantum-mechanical model of the atom, but it occurs occasionally in journal articles, so it must have a place.** I use shell to refer to a place occupied by an electron that has a given energy level. It turns out that the two terms can be used interchangably, so I’ll switch to energy level. > [@](#): > > **If you mean the ordinary movement of electrons within an atom, then, as far as I know, electrons do cross through space when traveling between points. However, the path they take cannot be known because of the Uncertainty Principle (“one cannot accurately measure the position and momentum of an electron simultaneously”).** As far as I’ve ever learned, this is incorrect. The state transition takes no time and the energy level never exists in an intermediate state. > [@](#): > > **Derleth, I’m not sure if you mean that electrons are massless, but they aren’t. Electrons have a mass of ~9.1x10^-31 kg, or about 1/1830th that of a proton. Rough estimates of the mass of an electron have been known for some time (by substituting the charge calculated by Millikan’s oil drop experiment into the charge-mass ratio obtained by observing the behavior of a stream of electrons being deflected by a magnetic field).** I never stated that electrons are massless, because I know better. 🙂 If I implied such, I was mistaken or misread. > [@](#): > > \*\*Your post really clarified what’s meant by wave-particle duality (something I’ve never heard explained very well), though, once I thought about de Broglie wavelengths. \*\* Yes, de Broglie wavelenghts are precisely what I had in mind. I think that bringing the concept of wave-particle duality `up’ to the macroscopic realm and then explaining why we don’t notice it is a good first step in applying it to the quantum realm. > [@](#): > > _Originally posted by Enola Straight_: > **That is, without transversing the space between AND without any time elapsing, thus appearing to go faster than light…effectively going infinite speed?** This is why I will renounce use of the term shell: It implies physical motion too strongly in the layman’s mind, and that leads to conclusions like the one above. **Enola** , thinking of this as motion is not productive. Motion at infinite speed is nonsense: It would require an infinite amount of energy and break causality, to boot. Think of it as a state change, one that is constrained by the concept of energy levels. And don’t think of the electron as a particle. When it changes state, it behaving like a _wave_. It only behaves like a particle when it is traveling freely through space. **Ring** sums it up well. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [September 26, 2003, 9:00pm UTC](https://boards.straightdope.com/t/how-does-an-electron-go-between-two-points-without-crossing-the-space-inbetween/203919/22 "2003-09-26T21:00:47Z")
> [@](#): > > A quantum jump is an instantaneous discontinuous transition between quantum states. There is no in-between state and it takes no time for the transition to occur. Batting 500. There is no in-between state, but it does take time. The closer the two energy levels, the longer it takes, and the math conspires to ensure that the “effective velocity” of such a transition (delta x over delta t) is always less than the speed of light. As for how it gets from one place to another without ever being in between, the closest classical analogies are going to come from waves. Take a rope, tie one end to a doorknob, and wiggle the other end. If you wiggle at the right speed, you’ll get it to bend in a sort of S-shaped curve that’s growing, shrinking, and growing in the other direction, sort of like this ## [sub][/sub]/[sup][/sup] [sup]/[/sup][sub]/[/sub] (it’s hard to draw, but if you play around with the rope a while, you should see what I mean) What you have now is two regions where the rope is wiggling, but it’s not wiggling at all at the point right in between. Similarly (but not _too_ similarly; this is only an analogy), the electron-wave in certain states can wiggle in two different regions, but it can’t wiggle in the exact center. Where the electron-wave is wiggling is where the electron can be, and where it’s wiggling the most is where it’s most likely to be. ---
**Author:** ![FriendRob](https://avatars.discourse-cdn.com/v4/letter/f/ecc23a/32.png) [@FriendRob](https://boards.straightdope.com/u/FriendRob)\ **Post date:** [September 26, 2003, 9:04pm UTC](https://boards.straightdope.com/t/how-does-an-electron-go-between-two-points-without-crossing-the-space-inbetween/203919/23 "2003-09-26T21:04:18Z")
The OP was asking not about transitions between states (which are **not** instantaneous) but about the distribution in one particular state. Yes, there are places where the wave function is zero, and the electron will never be found there. But remember, the wave function only tells you about the probability of finding the electron, _given that it is in a particular state_. Once you measure the position of the electron, you change its state. So, if you measure the electron to the left of the zero point, then later measure the same electron to the right of the zero point, you aren’t surprised - after the first measurement it was no longer in the state that had the zero point. This is why there’s no way to talk about the path of an electron when the electron is in a particular energy state. If you know the energy state, you don’t know the path. If you decide to determine the path, it will no longer be in the energy state. So, we can’t worry about what the electron does when we’re not looking. We can only talk about specific sequences of measurement and their outcomes. QM tells what the outcomes will be, but doesn’t give us a “picture” of what the electron does in between measurements. ---
**Author:** ![Skeptico](https://avatars.discourse-cdn.com/v4/letter/s/e19b73/32.png) [@Skeptico](https://boards.straightdope.com/u/Skeptico)\ **Post date:** [September 27, 2003, 5:22pm UTC](https://boards.straightdope.com/t/how-does-an-electron-go-between-two-points-without-crossing-the-space-inbetween/203919/24 "2003-09-27T17:22:00Z")
That’s the great thing about chemists: they are very pragmatic types; they accept experimental results and move on. **Dr. Love’s** prof doesn’t know the answer, and since he apparently doesn’t need to know for his chemistry research, he doesn’t care! Now, theoretical physicists on the other hand are just the opposite. They are very prone to wax in all sorts of _philosophia naturalis_ and navel-gazing (see “Tao of Physics”, “Godel Escher Bach”, “Dancing Wu Li Masters”, “The Quantum and the Lotus” \*). They need to know why. It bothers them. A Lot. I think **Chronos** ’s analogy is the simplest answer to the OP so far. I will give you an alternate Zen-like view to the problem. Consider this: when you ask “how does an electron go between two points”, you are implicitly assuming it has a path, therefore for them to go “without crossing the space inbetween” becomes a paradox. Remove the assumption, and Paradox Lost: “In quantum mechanics there is no such concept as the path of a particle” - Lev Landau, _Quantum Mechanics_ **p. 2** (!). (\* Can anyone recommend books of this sort written by chemists? I’m curious about their POV.) ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [September 27, 2003, 6:40pm UTC](https://boards.straightdope.com/t/how-does-an-electron-go-between-two-points-without-crossing-the-space-inbetween/203919/25 "2003-09-27T18:40:15Z")
Exactly. And that’s why you shouldn’t learn physics from a chemist.🙂 Feynman got it right. There is no macro scale analogy that is correct, so if you insist on imposing one, you will be wrong even if it makes you think you understand the situation better. You are thinking of an electon as a particle and asking how it gets from one place to another. But an electron isn’t a particle. It’s not a little moon orbitting a nucleus. On of my physics proffessors said at one point: Nobody acutally understands this-- you just have to trust the math. As had been said, electrons are “things” that exist in differnt energy states. What does that actually mean? Hell if anyone really knows… But we know how to predict certain behavior and force certain outcomes. And one of the behaviors we know is that it can’t be in an inbetween state. At least as far as we know now. Maybe some theory will come along in the future that changes all that. ---
**Author:** ![Ring](https://avatars.discourse-cdn.com/v4/letter/r/6a8cbe/32.png) [@Ring](https://boards.straightdope.com/u/Ring)\ **Post date:** [September 27, 2003, 7:57pm UTC](https://boards.straightdope.com/t/how-does-an-electron-go-between-two-points-without-crossing-the-space-inbetween/203919/26 "2003-09-27T19:57:28Z")
> [@](#): > > \*Originally posted by FriendRob \* > \*\*The OP was asking not about transitions between states (which are **not** instantaneous) \*\* From _Q is for Quantum_ by John Gribbon > [@](#): > > For example, an electron in one energy level in an atom jumps **instantly** into another energy level, emitting or absorbing energy as it does so. There is no in-between state and it does **not take any time at all** for the leap to occur. I believe Doctor Gribbon is ignoring the energy time uncertainty relation just as I was. The position-momentum uncertainty decrees that a particle does not, in principle, have both a definite position and momentum. Whereas, the energy-time uncertainty relation deals more with limitations imposed by nature on the precision of measurements. Time is not a dynamical variable it’s a parameter. [Previous page](https://boards.straightdope.com/t/how-does-an-electron-go-between-two-points-without-crossing-the-space-inbetween/203919.md?page=1)