In short, microscopic atomized oil droplets had their fall-time through air measured to figure out their volume, and then a known electric field was used to levitate them. The calculated charge-per-molecule clustered around multiples of a smaller value, which would be the charge of an individual electron.
Thanks for submitting! Would welcome suggestions for any other publications on how scientific theories were first discovered.
This is how Lord Rayleigh became the first person to figure out a single molecule’s dimensions, many years before anyone could see such molecules."
How did he know that the film of oil was one molecule thick?
It feels like a huge assumption to me, but maybe this blog post left something out.
"But a little experiment that Rayleigh performed in 1890, inspired directly by Franklin's observations, is not nearly as well-known."
Therefore Rayleigh computed the size of molecules in 1890, not in 1870 (in 1870 Rayleigh was young and not known yet for any original research).
While Rayleigh has devised a novel method for determining the size of molecules, it should be noted that the first who has succeeded to determine the size and weight of molecules was Johann Josef Loschmidt, in 1865.
https://en.wikipedia.org/wiki/Johann_Josef_Loschmidt
The publication of the weight and size of air molecules by Loschmidt is one of the most important milestones in the history of physics.
Until that moment in 1865, the theory of atoms revived by Dalton could still be considered as some kind of fictitious model that explained some features of the chemical reactions and of thermodynamics, but which might have been wrong and which would probably be replaced by some better model.
Starting from that moment, the atoms and molecules could be weighed and counted, so their reality was no longer questioned.
The determination by Loschmidt of the size and weight of air molecules was enough to determine the sizes and weights of any other known atoms and molecules, making use of the relative atomic weights that could be determined from chemical reactions and which were already known.
Moreover, a few years later, in 1874, George Johnstone Stoney has used the results of Loschmidt together with the theory of the existence of an elementary electric charge published by Maxwell one year before, in 1873, to compute the value of the elementary electric charge. Some years later, Stoney has given the name "electron" to the elementary electric charge, which has been the source of a very large number of words in modern science and technology, from electronics to hadrons.
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For more like this, check out this lecture series: https://www.thegreatcoursesplus.com/the-evidence-for-modern-...
It's by a guy called Don Lincoln and it's about how we established things like the existence of atoms, the speed of light, and many other fundamental things that are good to know.
It's also an audiobook, though the lectures are easier to follow.
That was this same fella!
30 years later, Henry Cavendish measured G and estimated the density of the earth. Using candles, mirrors and telescopes.
His setup has mud in a jar and bacteria in it which you can see with a simple microscope or handheld lens.
So much history: there is also a little church on the Common, whose past members played a role in the abolishion of slavery: https://en.wikipedia.org/wiki/Clapham_Sect
Source: Public statistics and my back-of-napkin math, not accounting for waves.
This can apply to many other fields too!
?? Has the Gulfstream changed direction in the intervening years?
Interesting to look at picture of the text of the 1890 paper. That typesetting is almost the same as modern scientific papers.
Maybe Rayleigh had an early copy of LaTeX? ;-)
Was he just lucky that the spread was 1 molecule thick or that's the way oil spreads on water? Why?
It has become fashionable in foodie circles to mock the idea of adding oil to boiling pasta so as to prevent stickiness. The argument against seems to be that oil floats and cannot possibly affect the pasta, unless you add so much that the pasta becomes slimy. But I maintain that a drop of two in boiling water is enough to coat all the pasta in a single layer of molecules. The agitation of the water spreads the oil evenly as a kind of colloidal suspension.
All these fancy restaurants with elaborate methods to avoid sticky pasta.
What??