I always appreciate these stories about how very specific observations that most people would miss can give away far deeper details of the universe that many wouldn't even consider. Eratosthenes using shadows and figuring out the size of the earth within a few percent is another well known one.

https://en.wikipedia.org/wiki/R%C3%B8mer%27s_determination_o...

https://en.wikipedia.org/wiki/Speed_of_light#First_measureme...

Another interesting thing about using the timing of moon eclipses:

> Galileo proposed a method of establishing the time of day, and thus longitude, based on the times of the eclipses of the moons of Jupiter, in essence using the Jovian system as a cosmic clock. The times of the eclipses of the moons could be precisely calculated in advance and compared with local observations on land or on ship to determine the local time and hence longitude.

https://en.wikipedia.org/wiki/Galilean_moons#Determination_o...

It's amazing to think that with nothing more than a telescope and careful timing, he managed to get so close to the actual speed of light.

The speed of light, because it is so fast, is the most precise physical constant known : 299 792 458 m / s. Less than 7/1000ths away from 300,000,000 m / s. I am not going to sweat this in the least.

So light travels only 0.3 m / nano second, or 11.802 inches.

https://www.youtube.com/watch?v=9eyFDBPk4Yw

They tried a similar experiment first, called the water drop experiment. It was intended to work in the exact same way, except with the obvious parameter varied: they would use water instead of oil.

The reason the water drop experiment failed was that the bright lamps they used to look at the drops evaporated the water too quickly.[1] Such a relatable experience!

[1]: https://buttondown.com/entropicthoughts/archive/when-bubble-...

There is always more to the story:

https://www.scribd.com/document/661270387/My-Work-with-Milli... Fletcher & Millikan

https://www.youtube.com/watch?v=B-uWaEvXqbA

How can you make sure you don't end up with 2e as a result? (Or any other multiple)

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 Maxwell's equations, the Michelson Morley ether experiment, to deriving then proving experimentally proving general relativity and decomposing GR into Newtonian physics/other laws of electromagnetism, I am still in awe at the people just figuring this stuff out from first principles.

Anyways, I haven't read this (have it on hold at my library) but someone recommended this book on reddit How to Make an Apple Pie from Scratch: In Search of the Recipe for Our Universe, from the Origins of Atoms to the Big Bang https://www.publishersweekly.com/9780385545655

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.

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.

Yes, often what is taught is taught in a manner that seems mysterious in origin, as if it were revealed, certain and final, and developing a sensibility like that concerning scientific matters is not good. You could argue that the viability of science as such rests on certain articles of faith, but the particular findings of science themselves are a matter of demonstration, interpretation of demonstration and argument making use of interpreted demonstration, as well as the making of certain working assumptions that do quite a bit of quiet heavy lifting. The last, I think, receives too little attention, but it also supports the idea that practical and pragmatic rather than theoretical motives and habits drive much of scientific activity.

So very true. The greatest science teachers understand the power that comes with the stories of scientific discovery.

Carl Sagan’s Cosmos and some of Richard Feynman’s best lectures come to mind as some of the most memorable examples, but I’m certain all the best teachers out there know to incorporate the historical and human aspects to bring the essential perspective and natural mnemonic anchors to otherwise “dry” subjects.

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.

How we derived the laws and theories is science. (Some of the other commenters are mixing this together with biographies of the scientists, which is not science but is sometimes interesting in its own right.) The laws and theories in isolation are just trivia, and any class that teaches just those cannot truthfully be called a science class. Demand a better education.

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.

>that laws and theories are presented as just something that you need to memorize

That's part of a larger problem in how science is presented. It is presented as something that is true, when it isn't. It is a model that describes reality. The models you are learning in high school and entry undergrad classes are mostly wrong models whose main use is that they are great building blocks to more complex models, as they work well enough in ideal conditions and correlate well enough with our exist. Yet even the best, most up to date models, aren't right. They work well enough in the places they are used that we can bet human lives on them, but that doesn't mean they describe what the universe is actually doing. Unless someone finds a way to crack open up the universe and check the "source code", we will never know exactly what the universe is doing and are limited to only ever improving models that approach the truth, like a sum that converges on a value at infinity but never equals that value for any finite sum of the series.

Pretty sure I remember recreating this experiment in high school chemistry.

but chronological order of scientific discoveries does not imply conceptual linearity, so i kinda get why colleges and schools do not go for that kind of approach

There's literally a dedicated major called History of Science. They teach fundamentally different things for different reasons.

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

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My question exactly.. I hope someone can chime in :)

EDIT: Thinking a bit more... I suppose it's a reasonable assumption that the molecules (mostly) wouldn't stack on top of each other. They all want to get lower and perhaps the resistance to the oil spreading out is much lower proportionately that the gravitational force encouraging the oil to flatten

Perhaps he was observing the layer making sure it had integrity? Oil layers famously have an optical effect (iridescence from interference of reflections). This effect would transition as the layer goes from >= 1 molecule thick to <= 1 molecule thick (on average). It's likely possible to pinpoint this transition experimentally and then using the oil volume obtain the molecular layer thickness.

To me, the much more questionable assumption is that volume is preserved when a liquid spreads out to a layer one molecule thick.

There's no reason why the volume you get when each oil molecule is surrounded on all sides by other oil molecules should be the same as when each oil molecule has air above and water below. Can anyone explain why this is so?

there has to be some missing information on how he found the area of water that fully consumed exactly that amount of oil as it simply doesn’t make sense without that. for instance one can spread a teaspoon of oil over 1, 2, n square meters and at some point the oil goes from m later thick to one to less than one.

Blog post seems to have elided this point, but it did link the original paper which was quite short: https://www.damtp.cam.ac.uk/user/gold/pdfs/teaching/old_lite...

Rayleigh's experiment was actually trying to solve for the minimum thickness of oil required to stop some camphor shavings from moving around on the water. He never states it explicitly, but I think the assumption is that the minimum thickness required to stop the shavings' movement would be such that the oil volume 'just' covers the surface, ie. is 1 molecule thick everywhere and hence the shavings never touch water. I think he's specifically making a slightly more clever point about surface tension, but that's a little beyond me.

If you try the experiment lots of times with drops of different sizes you find the oil layer always has roughly the same thickness. That's an interesting observation that calls for some kind of explanation, and the hypothesisis that the thickness of the oil layer is the length of one molecule is perhaps the most obvious and plausible explanation. Then one would look for confirmation, of course. (What was the next thing to confirm this, historically?)

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.

Agreed. The experiment actually gives an upper limit on the size of a molecule in one particular dimension. Still a very useful result.

Scientists frequently have to make assumptions in order to make progress.

Famous example is Darwin figured out that traits are inheritable by natural selection, and this is the driving force of evolution, without having any concept of the physical nature of DNA, or how genes could change (eg. by DNA mutation) to develop adaptations and thus make an organism more fit.

If there were multiple layers of molecules then the film would spread out over a wider area. With repeated experiments it would be clear that films are always an integer multiple of this thickness and never thinner.

The molecular scale was well estimated (at least for the gaseous phase of matter) by 1865 (25 years earlier not 5 as the incorrect HN title would suggest) https://physics.stackexchange.com/questions/13757/how-was-av... (and guesstimated by just "following your nose" in Gandalf-of-Lord-Of-The-Rings-ese in 1646!)

Rayleigh's experiment is just accessible requiring very little training / background to describe. To interpret as a monolayer is honestly probably not so accessible at all, though, and a weakness of the atomsonly.news piece and seemingly not even done by Rayleigh himself. Modern retconning as zokier says elsewhere.

Perhaps at the time it was sufficient to define "molecule of oil" as "the height of the amount when spread maximally across the surface of water", and it just so happens that height is only 1 actual molecule

An idea: if oil forms a two dimensional shape, ie a single layer of molecules, then adding 2x amount of oil would give you twice the area. If it is three dimensional, say oil makes a bubble, then it would look smaller.

Of course this also fails if the oil formed a disc of X layers of molecules

> How did he know that the film of oil was one molecule thick?

He didn't. It was an assumption

I have also immediately thought the same question. This is probably the most crucial part of the whole estimation and indeed left out in the article.

And even assuming it's one molecule thick, how did he know how tightly the oil molecules in that layer pack together?

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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.

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.)

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Fixed!

That's a bit harsh. To give one counterexample, the Michelson-morley experiment put the figurative nail in the coffin of centuries of speculation about the "luminiferous aether". The experimental apparatus was a table-sized precision carved slab of sandstone floating in a huge vat of mercury, holding the highest precision optical equipment of the day. I suspect it cost rather more than $100 even in the 1880s.

Ten years earlier and she didn't publish it right away. That really goes to show how much more difficult it was for a woman to become a scientist back then.

By 1870 pi was known to several hundred decimal digits, for something like this calculation where you have other large sources of error Archimedes approximation from 2 millennia earlier would probably be fine. (<1% error)

https://en.m.wikipedia.org/wiki/Chronology_of_computation_of...

Its not ancient times, some of the most accurate measuring instruments of that time are of a precision that you'd still need a few hundred or thousand dollars to buy today. The tooling wasn't primitive by any means.

YouTube video: https://www.youtube.com/watch?v=RST_ylwVrUw&t=1m27s

Yes, we did it in physics at school too, when we were 13 or 14 I think.

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

The actual manuscript from Rayleigh [1] explains it better: the area is the entire area of the vessel the oil was placed in, and the thing actually being measured was how much oil was required for it cover the whole area.

[1] https://www.damtp.cam.ac.uk/user/gold/pdfs/teaching/old_lite...

He used a fixed area (a 33 inch diameter bowl) and measured the weight of oil required to just about calm the entire water. That turned out to be 0.81 milligrams.

Some powder is added to the water, which covers the surface of the water but not the oil patch (which is circular). Then the oil patch diameter is measured.

Here's a video from another post: https://news.ycombinator.com/item?id=41630637