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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

#121

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…

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.

Both have their value, both the process and the results. And given the immensity of scientific knowledge, you can only learn so much of it in a K-12 education, or even in college.

I don't think it's a priori wrong to teach students our current understanding of the world, without going into the details of how we came up with it. I also don't think it's wrong to add those details, but the more details you add, the less of the full picture you'll be able to present. And I definitely don't think it would be a good idea to teach children how we do science, without teaching them what we actually learned from doing it.

I'd also say that the reality of some of the process is extraordinarily boring ("we kept meticulous records of precisely where on the sky various stars were each night, and how their position changed, for a few hundred years, and tried finding a function that matched those numbers; for a few hundred years, we kept adding more and more circles to correct things, until Kepler came up with some ellipses"). And that for many children, learning history is already a huge bore, learning the history of science in addition would make science classes much worse. For others, the opposite is true.

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

#122
post #32

Earlier quoted context omitted.

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

In 1909 the results results were couched in some "elementary electric charge" quantity, since the now-familiar subatomic particle model (and the "electron") was still gaining acceptance. I expect that the greater the number of trials, it becomes easier it is to detect a distinction between closer-multiples, and if at some point more trials stops changing the answer then you've likely converged on e, unless there's so…

The approximate value of the elementary electric charge had been known since 1874, when it was first computed by George Johnstone Stoney. After Stoney, other experiments had reduced the uncertainty with which the value was known, but it remained relatively high.

The importance of the experiments of Robert Andrews Millikan consists in the fact that the uncertainty of the value of the elementary electric charge obtained by this method was much smaller than by any previous method (he claimed that it was better than one half of one percent, but he used wrong values for the viscosity of air, so his actual result was off by more than that, but still by less than one percent from the correct result).

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

#123
Thanks for covering that story - I lived at Clapham Common for seven happy years.

So much history: there is also a little church on the Common, whose past members played a role in the abolishion of slavery: https://en.wikipedia.org/wiki/Clapham_Sect

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

#125

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.

We also did it in uni, it was very exhausting. And after a full day of measurements noone ever had enough data to see the quantization of the charge of electrons.

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

#126

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…

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.

Most of the general public would be better served with more emphasis on the history of science. Knowing how and when it happened makes it seem less like magic dogma given to them from the elders, against which rebellion is appealing.

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

#127

Even back in the day, without all our modern technology, great minds like Franklin and Rayleigh could uncover truths that still resonate today.

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.

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

#128

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…

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.

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

#129

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?

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.

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

#130
post #50

In 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 distan…

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.

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