Physics question - Spinning and Tidal lock.

[Soluna]

This is probably an odd question, that can probably be answered in a way by more research than I have already done - but so far I can't find an explanation put into terms that I can really understand. Plus the thoughts came up as I was attempting some EE and PoTS last night, so perhaps it might spark some interest or thoughts here - plus an answer that might make more sense to me!

I don't fully recall the order of my thoughts that led to these questions - I think I was remembering long childhood car journeys at night, and staring up at the moon with my adolescent mind feeling some sort of 'kinship' - which was probably spurred by hearing how a womans cycles were linked to moon cycles and 28 days and tides.

Which got me to wondering about orbits and spins and tides - and the reflective nature of things such as 'orbiting' electrons and their spins.

'Good old Google' led me to this description of electron spins http://scienceblogs.com/principles/2010/07/26/electron-spin-for-toddlers/ - which was kind of cute and fun!

I was wondering, 'if' electrons could 'tidally lock'? ie spin at a rate that left one 'side' facing the nucleus? If it could, what would happen?

Looking up 'how tides work' led me to http://www.physicsforums.com/archive/index.php/t-14029.html - in which one of the responses had an interesting comment :

The Moon's tides are also slowing the Earth's rotation, but since the Earth is some 81 times more massive that the Moon, it will still take some few billion years before the Earth always presents one side to the Moon.

Which made me wonder about the 'rate' of the Earths slow in rotation.


Everything seems connected, in its way - and sometimes I feel very 'foreign' on the surface of the BBM, a bit like a cardboard replica village built on the side of a volcano, just to see how it would burn - hmm not quite sure how to explain that feeling!

 

[pstott]

The way I understand electrons is that they are not little balls that orbit the way planets or moons do. Rather they occupy an area in which their presence is more like a cloud of probability spread around the nucleus. These clouds are arranged at various ranges of distance from the nucleus - depending on how many electron-"shells" an atom has. It is not gravity that keeps an electron in its shell, but atomic forces.

In the case of moons & planets being tidally locked - they are distinct solid bodies that are attracted by gravity - for tidal locking the density of the orbiting body would be uneven, with the denser side eventually always pointing towards the center of orbit.

Hope this clarifies things.

 

[durabone]

Hey Soluna and pstott! It is a very interesting question indeed. Many write that an electron must rotate twice for a full rotation, aka 720 degrees, not 360 degrees. Look up Roger Penrose and Dirac's "belt trick" for some discussion on this topic. Some focus on algebras that exhibit this property, like quaternion algebra. Here is a more basic approach. Find two coins the same size (serrated edges help), then try this:

Tidally locked: Place both coins with the "heads" up on a table. If you hold one coin stationary and revolve the other coin around it, keeping say the top of the head pointed inwards at the stationary coin, you will see that a tidally locked electron would rotate 360 degrees in a single revolution.

Circumference locked: If you now allow the serrations on the two coins to engage and not slip during the revolution, the outer coin rotates twice in a single revolution.

In both cases the rate of rotation of the electron is 'locked.' As for what it means in light of quantum mechanics, etc. I do not have a clue. I do know that things in the "circumference-locked" mode only rotate this nice neat 720 degrees only if the two coins are the same size. This seems problematic for electron and nucleus.

 

[Buddy]

I was wondering, 'if' electrons could 'tidally lock'? ie spin at a rate that left one 'side' facing the nucleus? If it could, what would happen?

I agree with pstott in that the question assumes an electron is like a tiny baseball or something similar. What an electron really is though, seems to depend on other factors that may need to be considered first.

We know from that famous two-slit experiment that an electron only acts like a particle (3 dimensional object) in the presence of direct photon interaction. When that experiment was performed while shielded from light, only wave-front patterns were detected by the screen after electron 'objects' supposedly passed through a doubly slitted wall. When bunches of electrons were shot out of the emitter and only some of the electrons were hit by photons, that quantity of electrons hit by photons went through a slit and showed a particle pattern. The remaining ones showed a wave pattern.

So what is an electron really? I'd say it is much more than a 3d object, but whether it's a particle, a wave or maybe a 'wavicle' or something else entirely probably depends, at the very least, on the specific environment or experimental setup and the detecting equipment used.

 

[Soluna]

Thank you for your responses - I think it highlights to me that I was considering things from a very '3D' viewpoint! And trying to make things fit into the neat little boxes that make '3D' sense, rather than remembering that not everything can be explained in a way that I will understand.

During my ponderings I was definitely thinking about electrons as little floating balls of charge spinning around nuclei, it didn't even occur to me in that moment that they may not be! Which looking back was certainly silly not to consider.

There is so much to everything that is so interesting - there would be no way to learn about everything in one limited human life time! Learning one scrap of a theory seems to open up so much more, it's so daunting.