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In 1870, Lord Rayleigh used oil and water to calculate the size of molecules

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Re: In 1870, Lord Rayleigh used oil and water to calculate the size of molecules

#51
"Rayleigh divided the volume of the oil by the area it covered, thus estimating the thickness of the oil film. Assuming that the oil formed a single layer of molecules — a monolayer — then the thickness of the oil film is the same thing as the length of one oil molecule.

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."

Re: In 1870, Lord Rayleigh used oil and water to calculate the size of molecules

#52
post #16
post #8

Earlier quoted context omitted.

[flagged]

Seems questionable that Rayleigh would have known that oil molecules are hydrophobic on one end and hydrophilic on the other.

> Seems questionable that Rayleigh would have known that oil molecules are hydrophobic on one end and hydrophilic on the other.

That's not a true thing, so it kinda doesn't matter. Surfactants (soaps, emulsifiers) have hydrophobic and hydrophilic ends. Oils are just straight up hydrophobic and nonpolar and don't have a water-loving end.

Re: In 1870, Lord Rayleigh used oil and water to calculate the size of molecules

#53

I love articles like this. I feel like too often in science education (at least my science education) that laws and theories are presented as just something that you need to memorize, when in my opinion the stories of how things were originally discovered and figured out is eminently more fascinating and inspiring. Like I remember having to learn all of these biochemical pathways, but I left school with nary a clue a…

Did you get your physics education in high school or university? I only had to take one physics class in the USA at college for my major, quantum electrodynamics for electrical engineering but my professor wrote the textbook and I recall he went over each experiment starting from the fundamentals of our understanding of the basics of the atom, Newton's understanding of light at the time, double slit experiment, to Ma…

What’s the name of that textbook? It sounds really interesting.

Isaac Asimov wrote a couple books that follow the narrative of science from the beginnings up until the 80s or so, which I highly recommend. One is called Atom and is more focused on how we got to our “present” understanding of particles. There’s also one that takes a broader view, it’s something like History of Science (? not at my bookshelf right now).

There’s several books in this genre for math as well. IMO it’s a much better structure for pedagogy since we can piggy back the education on our natural wiring to care about narrative and mystery/puzzles.

Re: In 1870, Lord Rayleigh used oil and water to calculate the size of molecules

#54

I love articles like this. I feel like too often in science education (at least my science education) that laws and theories are presented as just something that you need to memorize, when in my opinion the stories of how things were originally discovered and figured out is eminently more fascinating and inspiring. Like I remember having to learn all of these biochemical pathways, but I left school with nary a clue a…

I read Chasing the Molecule by John Buckingham recently and thoroughly enjoyed it! It give a good outline of the history of modern chemistry in a way that felt accessible but still thorough.

It also does a great job of explaining the different characters and their stories. Some little-known who moved chemistry forwards in profound ways, and others, very well-known, who through their loyalty to false theories ended up holding it back.

It's also a pretty short book when helps make it feel accessible.

Re: In 1870, Lord Rayleigh used oil and water to calculate the size of molecules

#55

I love articles like this. I feel like too often in science education (at least my science education) that laws and theories are presented as just something that you need to memorize, when in my opinion the stories of how things were originally discovered and figured out is eminently more fascinating and inspiring. Like I remember having to learn all of these biochemical pathways, but I left school with nary a clue a…

As part of 9th grade biology we had to read "Microbe Hunters". The grades ahead insisted that it was awful and boring but I devoured the whole thing in a weekend. So thankful that it was part of the curriculum.

Re: In 1870, Lord Rayleigh used oil and water to calculate the size of molecules

#56
post #22

I would have loved to have had a course in school about "The Design of Scientific Experiments." One that described the processes of landmark historical experiments from antiquity onward, and challenged students throughout: "Given this set of constraints, how would you design and execute an experiment to estimate the size of the Earth? Disprove phlogiston and luminiferous aether? Measure the speed of light?"

I don't think many people today would be able to propose the Michelson Morley experiment and then actually do it. It was truly heoric (and Michelson was a genius). We did this oil/water experiment in freshman physics or chemistry lab. It was rushed, everybody just did the minimum, the teachers barely explained any of it, and then we moved on.

People still win Nobel prizes (LIGO, for example) using interferometers. It’s arguably the single greatest invention in experimental physics.

Re: In 1870, Lord Rayleigh used oil and water to calculate the size of molecules

#57

I love articles like this. I feel like too often in science education (at least my science education) that laws and theories are presented as just something that you need to memorize, when in my opinion the stories of how things were originally discovered and figured out is eminently more fascinating and inspiring. Like I remember having to learn all of these biochemical pathways, but I left school with nary a clue a…

Discovering the quantization of the charge of electrons sounds like something you'd be interested in: https://en.wikipedia.org/wiki/Oil_drop_experiment

We did it with several hundred volts (DC, scary) in college and it was pretty fun collecting the data and watching the numbers fall out in excel doing the analysis.

Re: In 1870, Lord Rayleigh used oil and water to calculate the size of molecules

#59
post #48

Semi off topic: 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? ;-)

Thank Knuth for TeX or good scientific typesetting would be a nice thing the Victorians had.

Re: In 1870, Lord Rayleigh used oil and water to calculate the size of molecules

#60
Very cool.

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.

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