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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

#81

Post by komali2 »

happytoexplain wrote: post #13
bqmjjx0kac wrote: post #4

> 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. 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.

It feels intuitive that a thin fluid on a low-friction surface (like water) would spread out "as much as possible" given enough time. There certainly may be confounding factors, but it seems like a reasonable thing to pin as an "assumption" in a hypothesis. I.e. he didn't have to "know" - assumptions are OK, and I don't feel like this one is huge .

I'm confused, the blog wrote "known amount of water," so was it a closed little area like a bathtub? If you added a ton of oil wouldn't it spread out as much as possible aka 600 molecules thick or whatever?

Or did he pour it into a huge lake or something?

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

#82

Post by at_a_remove »

hn_throwaway_99 wrote: post #2

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…

When I was a tutor, mostly doing math, when it came to polynomials and that range, I would trick my students into deriving the quadratic equation. It's not even a full page. Almost all of them finished with a strange expression, and then we had the little "it was always there, waiting for someone to find it" chat.

Some people care about the history, some don't. I find when people talk about astrophysics stuff, most of them do not know the history and ought to, because most of their interpretations fall into the "Yes, that was a question in the 1960s but eventually ..."

If you want one for relativity, I strongly suggest Was Einstein Right? by Clifford Will. It dates from 1986, so it is nearly forty years behind now, but it covers the many experiments and tests of relativities special and general.

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

#83

Post by RheingoldRiver »

hn_throwaway_99 wrote: post #2

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 highly recommend this book! https://www.goodreads.com/book/show/25238350-the-hunt-for-vu...

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

#84

Post by owyn »

ghastmaster wrote: post #78
augustusseizure wrote: post #53

Earlier quoted context omitted.

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).…

You're referring to The History of Physics. An excellent read for a budding mind. Asimov was incredibly talented.

I was looking at my parent's bookshelf and saw a book on Shakespeare and I recognized the author's name: Asimov!

https://en.wikipedia.org/wiki/Asimov's_Guide_to_Shakespeare

It's like 800 pages, I haven't read it but I think I'll keep that one. Seems like it might be hard to find another physical copy. He was definitely prolific on a number of topics.

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

#87

Post by hn_throwaway_99 »

ddfs123 wrote: post #73
stevenwoo wrote: post #31

Earlier quoted context omitted.

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…

That was my Physics too, but Chemistry just completely glanced over the history. Same thing with Mathematics, no backstory of mathematicians. I guess that either 1. Physics History is short enough, well-recorded, or 2. Physicists really like teaching their history.

Yeah, in retrospect I think this aligns with my experience. But I'd even say that with the famous physics experiments I still remember often thinking "How did they get such precision with such primitive instruments?" I mean they would explain the experiments in very basic/schematic terms, but would have been nice to actually replicate I've to truly understand how it worked.

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

#88

Post by SJC_Hacker »

ddfs123 wrote: post #73
stevenwoo wrote: post #31

Earlier quoted context omitted.

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…

That was my Physics too, but Chemistry just completely glanced over the history. Same thing with Mathematics, no backstory of mathematicians. I guess that either 1. Physics History is short enough, well-recorded, or 2. Physicists really like teaching their history.

Physicists seem to be always seeking a deeper understanding of everything, more so than other fields like biology and sometimes chemistry, who have a tendency to get bogged down into to the idiosyncrasies of particular phenomena.

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

#89

Post by rkagerer »

This is fascinating, but wasn't it still a bit of a conjecture to assume the oil would spread to a minimum thickness of one molecule? Did he have any doubts, like that surface tension might keep it thicker? Or other clues hinting it was indeed a monolayer?

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

#90

Post by shepherdjerred »

ddfs123 wrote: post #73
stevenwoo wrote: post #31

Earlier quoted context omitted.

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…

That was my Physics too, but Chemistry just completely glanced over the history. Same thing with Mathematics, no backstory of mathematicians. I guess that either 1. Physics History is short enough, well-recorded, or 2. Physicists really like teaching their history.

MIT has an excellent chem course on YouTube that goes into the history
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