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The Most Beautiful Experiments in Physics
TheMatt writes "In this month's 'Physics World', Robert P. Crease asks the question: what is
the most beautiful experiment in physics?
Some criteria quoted are that it must change what people thought, must not be too complicated or expensive, and, most importantly, be within the reach of students (which leaves out Stern-Gerlach or Michelson-Morley). He also has a page at BNL reprinting the article, with a
place for suggestions from the community on their opinion." I'll nominate a simple one: Foucault's Pendulum. :)
I like the idea of exploring colored lasers.. especially synched up to Pink Floyd music ;)
Moderation: Put your hand inside the puppet head!
The two slit experiments are the most beautiful. With a simple apparatus it can be shown that light is a wave. With the same apparatus, it can be shown tha light is a particle. And that's not all folks...
The experiment reveals that there's something very very weird happening with very small particles. It could be another universe, or maybe an infinite number of universes. Or maybe just one really weird one. Time itself doesn't seem to have any meaning - things happen for no reason at all, uncaused.
These experiments even seem to reveal something about ourselves. Philosophers and cranks are attracted to the results like moths, offering their own explanations for what is happening, ranging from the hand of god to the basis of intelligence.
The strangeness revealed by the two slit experiment could also form the basis of future computers, where all calculations happen at the same time, but you can't look at the result without destroying the entire computer.
If that whole mess isn't beautiful, I don't know what is.
If tits were wings it'd be flying around.
In this experiment, tiny drops of oil are suspended in mid-air between two charged plates by the interaction of a discrete electric charge on the oil drop.
You use a microscope to measure the speed of the drop with no charge on the plates, then adjust the charge on the plates to hold the drop in place. In other words, the force of gravity is cancelled by the electrostatic force.
If the drops are small enough, you can notice discrete steps in the data when you plot the variables. The beauty is in its simplicity: Using some oil, two pieces of metal and microscope, you can determing the charge of a single electron.
It doesn't get much prettier than that.
Muerte
I always liked how helium balloons go the `wrong' way in a vehicle. toward the rear when braking, rightward when turning rightward, etc. And how General Rel holds the simplest explanation: gravity is indistinguishable from acceleration.
The Pitch Drop Experiment.
If you check the site out, you will even find a live RealVideo stream of the pitch.
Pitch (a derivative of tar once used for waterproofing boats) feels solid at room temperature, and it can easily be shattered with a blow from a hammer. However, at room temperature it is actually fluid.
Quoting from the website:
"In 1927 Professor Parnell heated a sample of pitch and poured it into glass funnel with a sealed stem. Three years were allowed for the pitch to settle, and in 1930 the sealed stem was cut. From that date on the pitch has slowly dripped out of the funnel - so slowly that now, 72 years later, the eighth drop is only just about to fall."
What were the skies like when you were young?
The best experiment is really a pair of them: Young's double slit experiment, and the photoelectric effect. Young's double slit experiment showed that light acted as a wave. The photo-electric effect showed that light acted as a particle. Together they showed that light acts completely unlike anything we experience in the classical world.
Both are simple, easily doable in the laboratory for undergraduates, and after doing (and comprehending) both you'll never again think the same way about light.
I vote for the experiement on the moon when they dropped the hammer and feather to demonstrate aceleration in a gravity field. If not the "most beautiful" experiement it was probably the most watched experiement. Of course, the location of the experiment is what makes it so memorable for me.
Eratosthenes accurately estimated the diameter and circumference of the earth with a stick. That's beauty.
It doesn't necessarily take physics to change a man's worldview:
The Cointoss Fractal
Get a largish sheet of paper, a coin or a d6, a felt-tip marker, and a tape measure.
Draw three dots, making any given shape of triangle. Pick any dot at random. This is your first point. Use the coin or a d6 to *randomly* decide between all three dots as a second point. Draw a new dot exactly half-way in between the two points. Use the dot you just drew as your new first point. Use the coin or a d6 to randomly select a new second point. Draw a dot exactly half-way between the two points. Wash, rinse, repeat.
After even a few hundred iterations, you'll begin to see a beautiful crystaline-like fractal pattern emerge. Even with the inherent innacuracy of this method, you can see the fractal down to the fourth or fifth iteration of the pattern before it breaks down. If you use even a slightly more accurate method, such as a C or Pascal program to draw colored dots on a computer screen, you can get 10 or 11 iterations, even with interger math rather than floating point.
The first time I saw this, I very nearly cried.
Order from chaos, just from math.
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You could do this with material from a smoke detector and some fluorescent screens.
He sent a beam of alpha particles through a target, which according to the theories of the day should have been like firing a bullet through jello.
Some of them bounced straight back, which proved there were small hard objects in the "jello". Those small hard objects were atomic nuclei, and the experiment revealed the existence of matter with unprecedented density.
Simple, cheap, interesting. http://scitoys.com/scitoys/scitoys/magnets/gauss.h tml
Michelson-Morley had to do with the existence of aether. It was complicated, but elegant.
;-)
But Michelson had already done an even more historically impressive experiment, I think, that had to do with the most accurate measurements of the speed of light in his day by far. "In 1878 Albert A. Michelson first accurately measures the speed of light with $10 worth of apparatus along the seawall" (scroll toward the middle of the page).
The more accurate measurement he made in the 1920s is described briefly below that quote on the same page. Certainly the $10 experiment is in the grasp of most classrooms, but I think the mountaintop one is also possible for today's students, what with GPS and all, or even a really good topo map (+/- a few feet gets you close-enough-for-proof-of-concept). You have to get 2 teams of kids on 2 different mountains- and with SUVs and the quality of roads nowadays, how hard is that to do in the high sierras with some adult supervision? Maybe hard to do if you live in Kansas, admittedly.
Plus, what school kids want to sit around a stuffy lab? How cool an experiment would it be to the most science-jaded student to get out of the classroom and into the wilderness to do science on an as easily appreciated concept as the speed of light?
Here's another good article on the history of the speed of light and better details of Michelson's efforts.
intellectual property law is philosophically incoherent. it is your moral duty to ignore it or sabotage it
"To talk of many things:
Of plastic foam--and tuna cans--
Of chunks of lead--and string--
And how the force of gravity--
Will make the balance swing."
The above is from John Walker's excellent website. He conducted the Cavendish experiment in his basement.
- Monica
When I was in school, this was the most fascinating thing that I ever read about. Simple mirrors and rotation. Ofcourse, the Young's double slit experiment is also fascinating, but I didn't understand it when I was in School :)
s / pedlite.html
More info at a link I got from Google: http://www.phys.virginia.edu/classes/109N/lecture
S
I wrote a paper last year entitled "On Mathematical Beauty", which was mostly a philosophical work on whether it was proper to mathematics to be called beautiful, and if so, what one might mean by calling a particular bit of mathematics "beautiful".
So in light of that, I'm interested in seeing what people mean when they say that a physics experiment is "beautiful". If we can figure out what we mean by that (i.e., whether we mean "beautiful" in the same way as when we call a car or woman or building "beautiful"), then maybe that will help us decide which is the *most* beautiful.
Belloc
I got more rhymes than Jamaica got Mangoes.
I think that any experiment that makes people think "outside the box" can be called beautiful.
I forget what this one is called, but it goes something like this:
You have a light source on one end. Screen on another (a fairly long rail connecting the two.
Put a piece of horizontaly polarized glass between light and screen - the intensity of light on the screen is cut in half.
Add another piece of (vertically this time) polarized glass - there is virutally no light going through.
Lastly - add a piece of polarized glass that's at about 45 degrees half way in between the other two. What do you expect to see on the screen?
Sir Issac was not "sitting" under a tree; in fact, he was lying down, and he was sound asleep.
It wasn't just any apple which happened to fall onto him; it was a rather large apple, which fell because it had gone thoroughly rotten to the core.
And Newton did not say "I've discovered Gravity", but rather just commented "the world sucks."
The thing about things we don't know is we often don't know we don't know them.
I recall setting up a transparent cuboid (glass or perspex, I forget) to totally internally reflect light off one of its faces. When a second transparent cuboid was placed very close to the reflecting face, some light passed from the first cuboid into the second, and was visible coming out of the second cuboid. It happened even though the two blocks were not quite touching. This is a very simple way to demonstrate quantum tunneling.
Any sufficiently self-referential snowcloned
My favorite from high school was extremely simple. Use a "wave pool" (a pan and a mechanical device that dabs one or two prongs into the water at some frequency). Aim a strobe light at the pool and turn off the lights. When you match the wave frequency to the strobe, the waves seem to stand still. Of course, you are merely catching the flash at the same point on each wave. Move the strobe frequency a little slower and the waves creep out. A little faster and they creep back to the source. Two wave sources, and you get to see the effect of the interference pattern.
Nowadays, the most likely experiment students would grasp would be the effects of beer.
Seriously though... Anyone who went to UT Austin and took physics would likely have heard of Prof. Rory Coker and his Physics Circus. All sorts of beautiful experiments there. Among them was a demonstration of airflow. Put a three-foot high glass cylinder, open at both ends, over the top of a candle, the cylinder being flat on the table so no air gets in that way. The candle will go out, even though the top is still open. Do it the same way, and slip a simple piece of cardboard into the top of the cylinder, making an "outflow" and an "inflow". Even though the cardboard is maybe six inches long, it's enough to keep the candle from going out.
Then there's the experiment where Coker gets on a bed of nails and has his assistant bust cement blocks on a piece of plywood on his stomach.
Lately democracy seems to be based on the skybox, the Happy Meal box, the X-box, and the idiot box.
Dunno if this one is true, but it stuck in my head as being deliciously elegant..
Supposedly, shortly before WWII German scientists were trying to work out the best shape to use for U-Boats. The solution was as follows:
freeze a big long slab of ice with a rope embedded in it. Store it in a shed beside a long canal during winter. Wait for a day where the temerature of the water in the canal is zero degrees [everything in celsius, for the no-scientific americans among us] but has not frozen.
On the magic day, drop the block of ice in the canal, & start towing it down the canal at the speed you're interested in having your u-boat move at. The friction created by being towed through water creates sufficient energy to crack the latent heat of freezing, the only thing differentiating the zero degree block of ice from the zero degree water around it, & the edges of the ice start to melt, causing the ice to start taking on the optimal minimum drag shape for the speed it's moving through the water at.
Once the shape of the ice seems to have stabilized, you pull the block of ice out of the canal & measure its shape. Voila - you now have the optimal minimum drag shape for your u-boat.
The wave/particle and "acceleration indepency on mass" experiments are great, but I have a great respect for pendulum experiments. With them you can determine the mass of the earth, local gravity, determine that the earth does indeed rotate, mirror the findings of dropping differing masses, etc.. Not to mention that their ability to time events was important for a lot of other experiments.
Actually, this exact question was asked at an Olympics of the Mind competition back in 1990 or so. Teams had to submit as many creative answers as they could.
Answers were fantastic, far more creative than this one, included, but not limited to:
Accellerate the building towards c until it appears the same size as the baromoeter, and use the resulting speed to calculate the original size.
Drop it off, and observe the impact damage it makes to the ground. calculate the forces needed to do this.
Run far away from the building and hold the barometer at arm's lentgh until it appears the same size as the building. DO some trig.
Drop the barometer, and listen for the delay betwen it hitting the ground and the sound reaching you. Calculate height based on speed of sound.
ANd I really wish I could remember some of hte other 50-odd answers that one team came up with... it was fantastic.
And I think the thing about Bohr is an urban legend.
How about superfuidity?
Seriously, that is one of the coolest and creepiest things at the same time, watching liquid helium crawl UP and spill out of a container. Granted liquid helium is rather expensive it is something which should really get the little buggers thinking and doing some research.
--Won't that be grand? Computers and the programs will start thinking and the people will stop. - Dr. Walter Gibbs
First year physics - Lancaster, PA Sept 1967
Takes place is a large lecture theater. At one end of the room an empty beer can is suspended from near the roof by an electromagnet. At the other end of the room there is a long iron pipe hooked up to a canister of compresses air. At the end of the pipe there is a electromagnetic relay. Place a ball bearing the the pipe and aim it at the beer can across the room. Push a charge of air into the pipe, the ball bearing flies out of the pipe and as it leaves the pipe triggers the relay which causes the electromagnet to release the beer can. Both the beer can and the ball bearing begin to fall and accelerate at the same rate as the ball bearing flies toward the beer can. BANG. Our very very large physics professor, Prof. Richard Hood (aka happy) is heard to exclaim: "Ain't science wonderful". A true red letter day in a four year foray into college physics.
The Thompson experiment, or the modern manifestatin of, is by far my favorite.
Electron gun in a helmholtz coil, where with just a bit of E&M you can figure out the charge to mass of an electron. Very pretty as well, with the glowing electron path being steered into a loop.
Or shooting the falling monkey. It entertains the kids, and really hits home the idea that all things fall at the same rate, no matter how fast they are going laterally.
Getting diabetes AND salmonella would be a bad weekend.
This is so cool...
: www.fourthturning.com/forums/viewtopic.php%3Ftopic %3D22%26forum%3D6+ink+rod+glycerin+drop-of-ink+tur n&hl=en.
Bohm further proposed that the holomovement I mentioned consists of two parts - an explicate order and an implicate order. I will clarify this difference with an example that Bohm himself developed.
Imagine a jar filled with thick, transparent fluid-like glycerin, a highly viscous fluid. In the center of the jar is a cylinder rod with a handle so you can turn the rod. You add a drop of ink into the glycerin, and the ink just sits there. But when you turn the inner cylinder around, it pulls this drop of ink and stretches it out. If you continue turning, the ink is drawn out into longer, ever finer and fainter lines. Eventually, if you keep doing this, the ink actually disappears completely. You can no longer see it.
Now at this point, it's very tempting to conclude that the order that was originally present in the drop has now been rendered completely random and chaotic by thorough mixing of the ink into the glycerin. So much so that you can no longer even see the ink. However, if you now reverse the direction of the rotation, what you find is that this thin long line of ink will begin to reappear. And as you continue the reverse rotation, it will continue to get thicker and more clearly defined, and eventually, it will completely reconstruct itself.
Now this is a mechanical metaphor for what Bohm talks about. What it tells us is that a hidden order may be present in what appears to be random. That's a very important insight that Bohm had, so I'd like to repeat it. With reference to this example and with references to reality in general, what appears to be random may, in fact, contain a hidden order. And unless your epistemological net is sufficiently fine, or sufficiently broad, you may miss that hidden order.
Bohm call this order the implicate order, because although the ink is dispersed to the point of not being visible, its order has, in some way, been preserved. Or, I should rather say it's been transformed into a different form, but it has not been destroyed. And it can then move from being implicate into what Bohm would call the explicate order, where the order has been made visible and made manifest. So we than have this ink dot reappearing.
When the ink drop disappears, Bohm would say that its order is enfolded in the glycerin. When the ink drop reappears, its order is unfolded back into the explicate order. I am going to be using these terms, so I want you to be come familiar with them.
Taken from http://216.239.33.100/search?q=cache:rAqZl1UCxFIC
Interview with him about this very thing Here. Read up on this also here.
You quitting proves that the karma kap worked. The most annoying of the whores shut up. --CmdrTaco
Preconditions: You're on a plane, and have a drink in a cup that's close to full (about a cm off the top is fine)
Assumptions: the pilot is sane and sober; the plane is a commercial aircraft not designed for stuff like flying sideways
Normal expectation: when the plane banks to one side, the water would spill out of the cup
Observed behaviour: water level will remain parallel to that of the plane, and hence the table that the cup is on, and therefore won't spill.
I noticed this a few years ago, and reasoned thusly: Other than the rudder of the aircraft, the plane has very little lateral resistance. When the plane turns, it banks at an angle to balance out the centripetal forces created by the plane's turning. To the people on the plane (and the beverage), this is simply an increased downward force, but looking out the window, it appears the plane is tilted.
Of course, if the plane runs into turbulence, the drink may spill.
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Sit in a swivel chair and hold a bicycle wheel with the axis vertical and the wheel itself perpendicular to your chest and the wheel spinning. Rotate the axis by 180 deg so that it is still vertical, but with the axis reversed. The chair starts to rotate to conserve angular momentum.
Why I like about this one is that it is quite amazing if you haven't seen it before, but it demonstrates a principle of classical, high school physics.