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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 once saw an experiment where a small bag made out of thin plastic was subject to the forces of a small pocket of circular wind currents.
Sometimes there's so much beauty in the world, I just can't take it.
I like the idea of exploring colored lasers.. especially synched up to Pink Floyd music ;)
Moderation: Put your hand inside the puppet head!
...comic book breasts. They break at least 3 laws of physics every day.
Kids these days. They don't know the difference between classic, and just plain old.
What about Gallileo's hypothesis about the Feather and the Hammer that was proven on the (IIRC) Apollo 14 mission?
Good quote, too many chars. Seriously, the slashdot 120 char limit sucks!
My vote (without reading other comments) goes to Arthur Eddington's validation of Einstein's relativity by demonstrating that the sun's gravity bent the light from nearby stars. But how do you see stars when they're right next to the sun? Good lateral thinking, very ingenious...
"None are more hopelessly enslaved than those who falsely believe they are free." -- Goethe
Henry Cavendish did an experiment to measure the gravitational constant G. He used a torsional pendulum with two small lead weights to measure the gravitational attraction of two large lead weights nearby. I did this experiment as an undergrad and got a pretty good value for G (big error bars though). It's amazing that back in the 1700s he could measure the gravitational force due to a lead ball.
I just did a google search on "Cavendish experiment" and found this. Evidently a geologist named John Michell deserves some credit too.
...has to be a front-runner here. Something as simple as a piece of paper and a light source showed that classical mechanics was not enough to explain our universe and that quantum mechanics had to be invented. No computers needed, no complex aparratus, and no genius needed to explain it (today).
;-)
Course, I am a physics freak. The biology, computer science, chemistry, etc. freaks may have their own opinions!
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
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.
Eratosthenes accurately estimated the diameter and circumference of the earth with a stick. That's beauty.
Ok, so this is probably apocryphal, but I was sent this a while ago:
A question in a physics degree examination at the University of Copenhagen
ran thus:
"Describe how to determine the height of a skyscraper with a barometer."
One student replied:
"You tie a long piece of string to the neck of the barometer, then lower the
barometer from the roof of the skyscraper to the ground. The length of the
string plus the length of the barometer will equal the height of the
building."
This highly original answer so incensed the examiner that the student was
failed immediately. He appealed on the grounds that his answer was
indisputably correct, and the university appointed an independent arbiter to
decide the case. The arbiter judged that the answer was indeed correct, but
did not display any noticeable knowledge of physics. To resolve the problem
it was decided to call the student in and allow him six minutes in which to
provide a verbal answer which showed at least a minimal familiarity with the
basic principles of physics. For five minutes the student sat in silence,
forehead creased in thought. The arbiter reminded him that time was running
out, to which the student replied that he had several extremely relevant
answers, but couldn't make up his mind which to use. On being advised to
hurry up the student replied as follows:
"Firstly, you could take the barometer up to the roof of the skyscraper,
drop it over the edge, and measure the time it takes to reach the ground.
The height of the building can then be worked out from the formula H = 0.5g
x t squared. But bad luck on the barometer.
"Or if the sun is shining you could measure the height of the barometer,
then set it on end and measure the length of its shadow. Then you measure
the length of the skyscraper's shadow, and thereafter it is a simple matter
of proportional arithmetic to work out the height of the skyscraper.
"But if you wanted to be highly scientific about it, you could tie a short
piece of string to the barometer and swing it like a pendulum, first at
ground level and then on the roof of the skyscraper. The height is worked
out by the difference in the gravitational restoring force T = 2 pi sqrroot
(l / g).
"Or if the skyscraper has an outside emergency staircase, it would be easier
to walk up it and mark off the height of the skyscraper in barometer
lengths, then add them up.
"If you merely wanted to be boring and orthodox about it, of course, you
could use the barometer to measure the air pressure on the roof of the
skyscraper and on the ground, and convert the difference in millibars into
feet to give the height of the building.
But since we are constantly being exhorted to exercise independence of mind
and apply scientific methods, undoubtedly the best way would be to knock on
the janitor's door and say to him 'If you would like a nice new barometer, I
will give you this one if you tell me the height of this skyscraper'."
The student was Niels Bohr.
A great example of how there are always different ways of looking at a problem, from one of the greatest scientists ever (allegedly).
We had finished our lab a bit early, and well, there was still about 3 gallons of unused liquid nitrogen -- this could not be allowed. So we started to figure out things to do with it, poured it on the floor and watched the dirt particles dance around :)
Looking for some other things to do with the stuff, I poked some holes in the bottom of our Styrofoam cup and poured the liquid nitrogen in it -- I had hoped the cup would levitate on the boiling nitrogen leaking out the bottom ... no dice, it was too heavy -- So I kept tearing away the walls of the cup, trying to leave enough room for liquid nitrogen, but leave the cup light enough to float. Finally I arrived at the right balance, and we had fun kicking our cup around the floor and watching it glide. So to be idiots we showed the TA what we were doing and he replies, "Gentlemen, you have just discovered the leidenfrost effect." And to this I reply, "We call it hovercup."
Religion is a gateway psychosis. -- Dave Foley
But this experiment is a bit misleading. Mass isn't actually independent of gravity. It is just extremely negligable when the second object is billions of times more massive than the object in question (like a bowling ball as compared to the Earth).
The force of gravity is proportional to the sums of the masses of the two objects in question (m1 + m2), and the Earth (m2) has a mass of 5.9736 × 10^24 kg. Try the same experiment by comparing how fast a bowling ball falls in comparison to a bowling-ball sized neutron star. (Of course, you wouldn't want to drop them at the same time, because you'd then be dealing with a three-body problem.)
Eratosthenes accurately estimated the diameter and circumference of the earth with a stick. That's beauty.
Quite right. This beautiful experiment is explained and recreated in Carl Sagan's Cosmos series. Not only that, but Eratosthenes did this many years Before Christ. By the time that Christopher Columbus petitioned the royal court for funding for three ships to sail westward from Portugal to India, scientists already knew the circumference of the earth pretty damn well. Well enough to know there was no way in hell Columbus would ever make it. But in 1492 -- and this is still true today, unfortunately -- the intelligent advice of scientists was disregarded by the rulers were blinded by visions of wealth and power and the Queen funded Columbus' journey. Turns out, unbeknownst to anyone, that Columbus' ass was saved because there was a land mass closer than halfway. Columbus decided that since he had sailed west to get to India, and ran into some land, had indeed reached India and proclaimed the inhabitants Indians -- a misnomer which exists to this day.
Although Eratosthenes was a true genius the world hails Christopher Columbus as a hero even though his accomplishment was sheer accident. What does this tell you about how the world views science and scientists?
GMD
watch this
I have always been a fan of the monkey in the tree experiment.
The setup story goes like this:
There is hunter walking through the forest, and he sees a monkey in the distance in a tree. He shoots at the monkey. Well, the monkey is so startled by the gunshot that he falls out of the tree at the same instant that the gun is fired. The bullet still hits the monkey. How is this so?
Basically this takes advantage of the fact everything falls at the same rate. You set up a gun of some sort (with a round projectile), and you set up a "tree" with the monkey a distance way. The gun and the monkey should be at the exact same height. The trick is to then fire the gun and drop the monkey at the same instant. The projectile should hit the monkey every time.
This experiment is a pain to get setup correctly, but it is pretty cool when it is successful. I couldn't find any video of it on the web, maybe somebody else can find some.
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it is an amorphous solid, refer to this urban legend...
An Urban Legend
The legend usually appears in any of the following forms:
Antique windowpanes are thicker at the bottom, because glass has flowed to the bottom over time.
Glass has no crystalline structure, hence it is NOT a solid.
Glass is a supercooled liquid.
Glass is a liquid that flows very slowly.
Glass is a liquid.
The prolonged survival of this legend, chiefly among English speakers (and particularly among North Americans) is puzzling -- especially when one considers that glass and glassy materials are readily available, and one can easily verify if one can pour a gallon of glass, or drain a pint of obsidian.
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Saw this expierement, professor has a rope with a bowling ball tied to the end suspended from a high ceiling. Stand at one end of the room with the ball pulled back and just touching his nose. Professer them lets go of the ball and it swings across the room and returns just missing his nose.
Of course, then stupid studnet comes back later that night to show a friend, holds the ball against his nose and gives it a sold PUSH...
Beautiful.
Krispy Cream is people
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