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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

#201

Post by jonny_eh »

RheingoldRiver wrote: post #199
jonny_eh wrote: post #97

Earlier quoted context omitted.

I'd recommend this one instead: https://en.wikipedia.org/wiki/A_Short_History_of_Nearly_Ever...

Why "instead" ? they seem completely different from each other Hunt for Vulcan is a fun history lesson with some interesting insights about human nature. It's history of science, not science. It took about 3 hours to read and I had a lot of fun with it.

The book I recommended is a book about the history of science, but on a broad range of topics. Much longer than 3 hours.

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

#202

Post by tsimionescu »

lern_too_spel wrote: post #200
tsimionescu wrote: post #121

Earlier quoted context omitted.

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…

The results are useful in engineering, but the fact that the results are useful does not mean that a class that teaches just the results is a science class. You don't have to include the boring bits of who paid for the research or the day to day lives of the researchers. That isn't science, and it doesn't help the student understand science. A mere description of the fact that Tycho Brahe kept meticulous records of t…

The results are what science exists for, ultimately. If you're not going to go do science, you still benefit from understanding what the world is - not just for engineering, but as a basic human need for understanding the world you live in.

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

#203

Post by zestyping »

rkagerer wrote: post #89

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?

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?

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

#204

Post by jjk166 »

kccqzy wrote: post #177
jjk166 wrote: post #146

Earlier quoted context omitted.

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.

Yeah and the point is that there is more embedded knowledge about surface tension here. For example if I put a small drop of water onto my desk, it does not spread out into a thin film of one water molecule thick. It remains a droplet due to surface tension.

And if you put an oil drop into that little bead of water it will spread out because it destroys the surface tension. That's why Rayleigh was playing around with it to begin with, and the reason why a thin film of oil calms the surface of water.

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

#205

Post by fennecfoxy »

xhrpost wrote: post #185
glial wrote: post #182

Earlier quoted context omitted.

Therefore in one cycle of a 3GHz processor, light travels about 4 inches. Wild.

Which is maybe part of the reason RAM needs to be so close to the CPU? Granted though most RAM access takes several CPU cycles.

This is exactly it, the longer your traces (or any sort of write I guess) between processor and memory, the longer delay you have to have for things to "settle". Additionally increasing capacitance means that it takes more effort (read, even longer) for the line to settle.

Does make me realise I don't know so much about the super low level parts of it beyond electrons and holes. One end of the wire needs to be at a lower potential to encourage electrons to flow from that side to the other. Hmmm.

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

#206

Post by lern_too_spel »

tsimionescu wrote: post #202
lern_too_spel wrote: post #200

Earlier quoted context omitted.

The results are useful in engineering, but the fact that the results are useful does not mean that a class that teaches just the results is a science class. You don't have to include the boring bits of who paid for the research or the day to day lives of the researchers. That isn't science, and it doesn't help the student understand science. A mere description of the fact that Tycho Brahe kept meticulous records of t…

The results are what science exists for, ultimately. If you're not going to go do science, you still benefit from understanding what the world is - not just for engineering, but as a basic human need for understanding the world you live in.

Being told what is correct doesn't work. That's how you get https://www.newsweek.com/alabama-biology-textbooks-evolution.... Calling something science that isn't science is a serious problem.

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

#207

Post by cchi_co »

wizzwizz4 wrote: post #174
foggyjvdfghhv wrote: post #173

Earlier quoted context omitted.

That’s not the definition of talent

From what I've seen, talent is the tendency for a person to naturally develop a skill, if left alone to do so. It isn't some kind of intrinsic capability.

[dead]

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

#208

Post by qsdf38100 »

hollerith wrote: post #191
qsdf38100 wrote: post #190

Earlier quoted context omitted.

Speed of light has recently been redefined, and is now _exactly_ 299792458 m/s. It’s no longer a measurement, it’s a definition.

That's a little misleading: either the meter or the second has been redefined to make c = 299792458 m/s.

Since 1983, the meter is defined in terms of the distance traveled by light in a vacuum during 1 second, see https://en.wikipedia.org/wiki/Metre#Speed_of_light_definitio...

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

#209

Post by stevenwoo »

knodi123 wrote: post #163
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…

you only had to take one physics class, and it was quantum electrodynamics??? That sounds to me as if someone said "The only math class I've taken was differential equations."

I think I placed out of the physics prerequisites (everyone was expected to have some physics in high school and we went over that and more in a mechanical engineering statics/dynamics/fluids class we all took at the same time) and QED was a standard first semester sophomore year class in the electrical engineering curriculum, the professor made it a lot of fun though every class I remember him deriving equations for thirty minutes on the overhead projector as he explained things, and it was the largest class I had with fellow electrical engineering majors, there was an advanced calculus/diff eq class and linear algebra class during our freshman year.
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