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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

#141

Post by veltas »

AlotOfReading wrote: post #98
dilawar wrote: post #65

I went to a talk by a very old physicist. At the end of his talk, he said, recalling from memory, all of the great experiments of the past were done by nothing. If an experiment costs more than $100, I am out. His setup has mud in a jar and bacteria in it which you can see with a simple microscope or handheld lens.

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.

Although it was a refinement of the Fizeau experiment which conceivably could have cost $100 in living memory.

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

#142

Post by hammock »

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.

Understanding Physics? https://www.goodreads.com/book/show/41819.Understanding_Phys...

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

#143

Post by tony-allan »

tony-allan wrote: post #92

https://www.atomsonly.news/p/franklin-oil Why this domain has been suspended Since January 2014, all ICANN accredited registrars (like Namecheap) have been required to verify the contact information (Registrant Whois) of customers registering domain names. This includes modifications to the contact details.

Fixed!

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

#144

Post by humansareok1 »

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…

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

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

#145

Post by SkyBelow »

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…

>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.

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

#146

Post by jjk166 »

MereInterest wrote: post #134
jjk166 wrote: post #35

Earlier quoted context omitted.

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.

Except that you could have part of the surface covered in 1 molecule, and another portion covered in 2 molecules. Since you never directly measure the thickness, this would produce the same apparent thickness as a uniform 1.5 molecule thick layer.

That's not how fluids work. The molecules spread out to form an even surface everywhere, so you can't have local high spots. You'd have to put in enough oil to cover the entire surface, and then put in more.

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

#147

Post by zokier »

NeoTar wrote: post #130
cchi_co wrote: post #115

Earlier quoted context omitted.

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.

Well, also knowledge of the distances between the objects involved (at least the Earth and Jupiter), which in turn depended on a series of further investigations. Which is not to denigrate the achievement, but if I were to drop you on an alien world with only a telescope and an accurate time keeper, you're not going to be able to recreate it.

> if I were to drop you on an alien world with only a telescope and an accurate time keeper, you're not going to be able to recreate it.

But you can relatively easily derive the distances too with timekeeper and telescope, by applying Keplers laws?

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

#148

Post by iamflimflam1 »

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…

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

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

#149

Post by albrewer »

augustusseizure wrote: post #53
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…

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 a youtube channel called "Kathy Loves Physics & History"[0] that goes over all these things in video form.

[0]: https://www.youtube.com/@Kathy_Loves_Physics

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

#150

Post by ummonk »

CamperBob2 wrote: post #101
bryanlarsen wrote: post #62

Earlier quoted context omitted.

Olive oil is a soap oil.

If that's true, then the ChatGPT answer isn't wrong, at least for the specific case of olive oil. I love how a few self-appointed guardians of hackerhood are able to declare certain resources as haram , even when they propose a plausible answer to a question that went unanswered more than once in the thread. Instead of embarking on a discussion that leaves us all a bit better informed, the literal messenger is attack…

No the idea that Rayleigh knew the film was one molecule thick, let alone why it was one molecule thick, is clearly made up. The paper makes it clear that he was reporting the thickness, and thought this might provide information on molecule size.
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