A few days ago, there was a HN post about surface acoustic wave filters, and a commenter mentions how inspired the inventor of it must have been(https://news.ycombinator.com/item?id=41604937).
That was this same fella!
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
#42I 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.
I agree. The Michelson Morley experiment reminds me of some difficult algorithms: simple only in hindsight, and implementation is _hard_ to do correctly.
Re: In 1870, Lord Rayleigh used oil and water to calculate the size of molecules
#43Earlier quoted context omitted.
How can you make sure you don't end up with 2e as a result? (Or any other multiple)
He did- he selected the lowest value, ignoring all the multiples.
Not ignoring the multiples; the multiples verify the result.
If you calculate the charge of one at 1e and you measure 2.5e, something went wrong. All values must be a multiple of the lowest.
Re: In 1870, Lord Rayleigh used oil and water to calculate the size of molecules
#44I 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…
> experimentally proving general relativity
Can you elaborate on that? What experiments did the professor perform?
Re: In 1870, Lord Rayleigh used oil and water to calculate the size of molecules
#45> 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.
Agreed. The experiment actually gives an upper limit on the size of a molecule in one particular dimension. Still a very useful result.
It isn’t necessarily an upper bound. The molecules might spread out more distant than their size.
Re: In 1870, Lord Rayleigh used oil and water to calculate the size of molecules
#46Related: Agnes Pockels’ experiments [0]
Re: In 1870, Lord Rayleigh used oil and water to calculate the size of molecules
#47Earlier quoted context omitted.
> Cortesy of ChatGPT: Can we not, please? At the very least not unless you personally have the knowledge to confirm that ChatGPT didn't make any mistakes, as it did here.
This should be a rule on hacker news.
Agreed. Everyone here knows how to use chatgpt. We come here for a different way to share, learn and interact.
Re: In 1870, Lord Rayleigh used oil and water to calculate the size of molecules
#48Semi 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? ;-)
Re: In 1870, Lord Rayleigh used oil and water to calculate the size of molecules
#49I 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?"
Experiments are HARD. There is a joke among physicists that theoreticians are washed up by 35 but experimentalists don't even get started until 45.
To make a physics experiment work you have to be ridiculous about recording details and have a strong intuition. You have to design the experiment such that you can differentiate between "hypothesis wrong" and "equipment doesn't work" because you don't know the answer.
(For example: When they turned on LIGO for the first time, they almost immediately caught a great event. Huge victory party, right? Nope. They promptly ignored it assuming that something was wrong with the machine. And it was only after significant post analysis and correlation that they decided that it was a real event.)
Re: In 1870, Lord Rayleigh used oil and water to calculate the size of molecules
#50In 1676 Roemer estimated the speed of light by timing the orbit of Jupiter’s moon Io, noting that as the Earth approached Jupiter, Io emerged from behind Jupiter a little earlier every day, and as the Earth traveled away from Jupiter it appeared a little later every day, with the time of day varying by 22 minutes over a year. Knowing the difference between the two distances, he reckoned that light travels that distance in 22 minutes, or 227 thousand km/s. The actual speed is about 300 thousand km/s. Not bad!