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Experiments

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MatC
153233.  Sat Mar 03, 2007 7:09 am Reply with quote

Just thought this would make a good heading; there must be plenty of quinteresting facts and anecdotes attached to famous experiments (or even obscure ones).

One thing at the back of my mind ... I never quite got the point of (possibly) the 20th centuryís most famous thought experiment, Schrodingerís Cat. It always seemed such an obvious nonsense that I assumed I must be missing something. However, I recently read somewhere (just spent the whole morning looking for it, with no luck; my memory, that is: if I could find that, I could find the book) that the purpose of the experiment was essentially sarcastic. Schro was having a ďGod doesnít play diceĒ moment, and made up his cat in order to demonstrate the absurdity of a then-emerging consensus on one particular aspect of quantum theory. In other words, itís supposed to sound silly.

Does anyone have any idea what Iím talking about?

 
eggshaped
153240.  Sat Mar 03, 2007 7:24 am Reply with quote

The NY Times does:

Quote:
Schrodinger intended his paradox as a sarcastic comment on quantum probability or ''blurred variables.'' One can resolve the uncertainty, he explained, by looking in the box.

 
MatC
153247.  Sat Mar 03, 2007 8:07 am Reply with quote

Brilliant - thanks, Egg. Is this too obscure for Gen Ig, do people think?

 
Flash
165955.  Sat Apr 14, 2007 4:28 am Reply with quote

I was wondering about a show which would look at questions of this sort:

How do you weigh the Earth?
How do you measure the speed of light?

and also perhaps the rough & ready ways that people have devised to measure things, like:

figuring out the altitude of the mountain you're on by seeing what temperature water boils at

measuring the ambient temperature by timing a rattlesnake's rattle and other animal behaviours (post 6660)

measuring the height of a tree by looking at it through your legs (allegedly used by "some African tribes" - you walk away from the object till you can just see its top when you bend and look through your legs, use an object of known height as a reference point, work out how many paces you need to be from the reference tree to just see the top and apply this equation: height of tree = height of practice object x paces from tree / paces from practice object).

 
Jenny
166053.  Sat Apr 14, 2007 10:01 am Reply with quote

Would that link to the mattangs maps thing and gauging how far you are from an island by the waves lapping your scrotum, do you think? (Could explain why there weren't many women navigators I suppose...)

 
Flash
166133.  Sat Apr 14, 2007 2:09 pm Reply with quote

Yep, could be. The mattangs are in rather a lot of demand - Explorers, Easter Island, and now Experiments.

 
Flash
166137.  Sat Apr 14, 2007 2:18 pm Reply with quote

Reference the tree-measuring thing, maybe a picture of a chap looking through his legs, with the Q What's this bloke looking at?

picture researchers

 
Flash
166149.  Sat Apr 14, 2007 2:43 pm Reply with quote

This stuff all relates to Estimates, I have just realised.

 
Jenny
166235.  Sat Apr 14, 2007 7:10 pm Reply with quote

Incidentally, I discovered this today about Efros on the outer forums (who lives about two hours' drive from me in Maine):

Quote:
I am a Dr. of Chemistry for my sins, specialisms include atomic spectrometry, computer controlled instrumentation and laboratory automation. Now I teach the locals as much as they can handle!


So if we need anybody with particular knowledge in that area, here's your man.

 
dr.bob
166588.  Mon Apr 16, 2007 10:30 am Reply with quote

Flash wrote:
I was wondering about a show which would look at questions of this sort:

How do you weigh the Earth?


Weighing the Earth is, of course, trivial. The tricky part is measuring the gravitational constant accurately. Given what a small number it is, this is no easy feat.

Flash wrote:
How do you measure the speed of light?


This is also not too hard. I did it in the lab when I was doing my physics degree and wasn't a million miles away. Of course, if you're extremely clever like James Clerk Maxwell, you don't need to measure it. You can just work it out theoretically.

 
Gray
166890.  Tue Apr 17, 2007 8:42 am Reply with quote

Measurements of the speed of light are interesting. It's not obvious how to do it, but Jean Bernard Lťon Foucault (yes, he of the pendulum) found a way, using a completely mechanical method!

Quote:
Foucaultís method was to shine a sharply focused beam of light onto a rotating mirror, and from there onto a fixed mirror. Once the light hit the fixed mirror, it bounced back onto the rotating mirror and then back toward the source. But because the mirror was rotating, the angle at which it was positioned had changed slightly by the time the beam made its return trip. Consequently, the reflected beam did not line up precisely with the original.

Foucault could easily measure the angle between the original light source and the reflected beam, and along with known constants (the distances between the various surfaces and the speed of the mirrorís rotation), it was a matter of a few straightforward calculations to convert that small angle into a representation of speed.

Using this technique, Foucault produced a measurement of 298,000 km/second (185,167 miles/second), which is shockingly close to the modern measurement of 299,792 km/second (186,282 miles/second), keeping in mind that the latter figure applies only in a vacuum; light travels more slowly in air.

As for the tuning fork... Foucault used this to regulate the speed of the rotating mirror. The apparatus that turned the mirror made a sound that varied with its speed; when the sound exactly matched that of the tuning fork, Foucault knew precisely how many revolutions per second it was making.


http://itotd.com/articles/284/measuring-the-speed-of-light/

Ole Roehmer used a method hundreds of years before, too, just by looking at Jupiter and one of its moons:

http://www.colorado.edu/physics/2000/waves_particles/lightspeed_evidence.html

Cunning buggers.

Good general page here.

 
dr.bob
166940.  Tue Apr 17, 2007 10:52 am Reply with quote

Quote:
Foucaultís method was to shine a sharply focused beam of light onto a rotating mirror, and from there onto a fixed mirror.


Yup, that's how I did it :)

 
Flash
167036.  Tue Apr 17, 2007 3:45 pm Reply with quote

Quote:
Weighing the Earth is, of course, trivial.


Perhaps, but my point is that it is also fairly easy to be funny about.

 
Molly Cule
167147.  Wed Apr 18, 2007 4:07 am Reply with quote

There is some stuff in Bryson about weighing the Earth. Cavendish in an experiment in 1797 worked out the MASS of the earth so accurately that the mass scientists now use is only 1% different to Cavendish. The mass is 5.9725 billion trillion tonnes. Cavendish worked this out at home, using a machine he made himself out of weights, pendulums and wires. At the heart of the machine were two 350-pound lead balls.

"The idea was to measure the gravitational deflection of the smaller spheres by the larger ones, which would allow the first measurement of the elusive force known as the gravitational constant, and from which the weight (strictly speaking the mass) of the Earth could be deduced."

Bryson says

"Each time you pick up a book from a table or a coin from the floor you effortlessly overcome the gravitational exertion of an entire planet. What Cavendish was trying to do was measure gravity at the extremely featherweight level."

Cavendish made his machine then made observations with a telescope, through a peephole, from the room next door. It took him a year to make 17 delicate measurements to work out the weight of the earth. He came to a little over 6 billion trillion metric tonnes.

p88 ASHONEverything

 
Molly Cule
167241.  Wed Apr 18, 2007 7:00 am Reply with quote

The bends were first noticed by Robert Boyle in 1667 when he began pressurization experiments on animals. When depressurising a snake he noticed the viper seemed disturbed then he saw a bubble of gas in the viperís eye.
S Ė Bridge and Tunnels book in QI library

 

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