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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.
Uh, what's the target group? I teach general freshman physics at my university and discuss both SG and MM experiments in detail.
Anyway, I nominate the first nuclear explosion as the greatest ever experiment. Until a hole is successfully opened in the spacetime, splitting the atom is the greatest scientific achievement ever.
There is, in fact, a fabulous book on this subject. What makes it such a great book is that it doesn't depict the making of the atomic so much as a rigorous scientific project, but rather as a social, political, random and very much a human achievement.
The owls are not what they seem
...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
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.
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.
The next Slashdot story will be ready soon, but subscribers can beat the rush and slashdot the links early!
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
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
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.
https://www.accountkiller.com/removal-requested
The most beautiful experiment has to be Newton's light slit and prism showing that white light is actually made up of many other frequencies. From there young minds can be introduced to all sorts of things such as why sticks appear to be bent when half in water and at what angle they seem to disappear. But to really get them going, help them create a hand drawn hologram. http://www.amasci.com/amateur/holo1.html
From memory, some of the more interesting experiments the Amateur Scientist column include:
Tons of goodies, all worth goofing around with. If you can't come up with some good ideas after leafing through this material, you just aren't trying.
There is much pleasure to be gained in useless knowledge.
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
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.
Though not particularly revolutionary, creating a cloud chamber and seeing the paths of radioactive particles is really quite amazing the first time you see it.
We did this experiement during A-Level physics, with small chambers using dry ice, alcohol and some of the small alpha and beta sources that schools are allowed to use.
A quick google seach will turn up lots of instructions for making your own, for example :
- some instructions from cornell
- or an article from Scientific America
although without a radioactive source you'll have to sit around and wait until some cosmic rays create some ionizing radiation that hits your experiment.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
Such a good story - it's a pity it is not true! Here's a link to David Goodstein's homepage - he's the vice-provost of CalTech - the second link on his homepage is a PDF file which should show you that the accusation is simply wrong.
Take a look - it's not long, and it's well worth it - before slandering a beautiful experiment.
"I will take the Ring," he said, "though I do not know the way."
John Conway's Game of Life, the most well-known cellular automaton, shows how nonlocal phenomena can be generated from purely local rules.
Since exposed to the science minded through Martin Gardner's column in Scientific American in 1970, Life has introduced many to the study of complex systems, emergence, etc, etc, which I now see as providing a broader context for the physics (and chemistry and biology and collaborative systems) which we find in this world.
For the record, this does not mean that I am convinced that our cosmos is a cellular automaton, but rather that complex systems provide a tool even more powerful than traditional math for modeling, and thus in some ways understanding, our world.
-- Our systemic servants do not good masters make.