31 Aug 2017 6:35:11 UTC

Topic 209492

(moderation:

I found on YouTube a great demonstration of a classic experiment performed by Robert Millikan over one hundred years ago. It is true brilliance. With straightforward apparatus ( not a multi-billion dollar device ) and a moderate amount of care one can establish a marvelous fact about our universe : one can only measure electric charge in integer multiples of a basic unit. One can measure that amount* but regardless of the precision of that estimation one is still left with the inescapable conclusion of ** charge quantisation**. Specifically integer could mean zero, and of course plus or minus whole numbers.

{ Note that I said ** measure**. Allegedly more basic particles eg. quarks are

There are many variations on exactly how to go about this process. I did one of those during undergraduate physics. I recall having to think carefully for a very long time as to why Millikan's technique guaranteed the final deduction of the experimental process. Fortunately I used professionally prepared apparatus in a laboratory session. You could probably buy some online kits, but beware it is not hard to spend a 4+ figure sum on this.

Bear in mind Millikan's circumstances ( ~1909 IIRC ) : the actuality of an electron was still contended, atoms too for that matter. His work is a lovely example of hard data forcing a sea change in thinking which some two decades later gave us most of the modern formulation of quantum mechanics.

Cheers, Mike.

* Strictly speaking, the mass to charge ratio of the electron and then use other determinations to yield that charge as a physical quantity.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

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