The Most Beautiful Experiments in Physics 527
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. :)
That's easy (Score:5, Funny)
Sometimes there's so much beauty in the world, I just can't take it.
Re:That's easy (Score:3, Funny)
Got a good one... (Score:4, Interesting)
Most Beautiful Physics Experiment (Score:5, Funny)
along those lines.... (Score:2, Funny)
Here's an odd one... (Score:5, Informative)
Here are links (Score:2, Informative)
http://www.jsc.nasa.gov/er/seh/feather.
and some old video:
http://www.jsc.nasa.gov/er/seh/feather.avi
Re:Here's an odd one... (Score:3, Insightful)
Eddington, 1919, proving general relativity (Score:5, Informative)
Re:Eddington, 1919, proving general relativity (Score:2)
Re:Eddington, 1919, proving general relativity (Score:3, Informative)
BTW, Newtonian gravity also predicts that light will bend as it passes near a large mass (if you naively assume that a photon feels the force of gravity, despite the fact that it has no mass).
The difference is that the size of the deflection according to GR is larger by a factor of 2 than the Newtonian prediction, which is what Eddington confirmed.
Re:Eddington, 1919, proving general relativity (Score:2)
The Cavendish Experiment (Score:5, Insightful)
I just did a google search on "Cavendish experiment" and found this [iastate.edu]. Evidently a geologist named John Michell deserves some credit too.
Bending Spacetime in the Basement (Score:3, Interesting)
"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 [fourmilab.ch]. He conducted the Cavendish experiment [fourmilab.ch] in his basement.
- Monica
I nominate nuclear explosion (Score:3, Insightful)
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 [amazon.com] 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.
Re:I nominate nuclear explosion (Score:2)
Re:I nominate nuclear explosion (Score:2)
The Two Slit Experiment (Score:5, Insightful)
Course, I am a physics freak. The biology, computer science, chemistry, etc. freaks may have their own opinions!
Two slit (Score:5, Interesting)
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.
Re:Two slit (Score:2)
With the same apparatus, it can be shown tha light is a particle.
Umm, you mean a quantized wave. To call light a particle is to seriously stretch the definition of particle.
So.. (Score:2)
That flies in the face of a great many years of modern physics you know.
Saying they are particles that propgate as waves is innacurate, of course.. it is merely light, and exhibits properties of both.
Re:Two slit (Score:3, Informative)
A photon can act as either a particle or a wave, depending on how it is observed. I just read an article on this, so it is fresh in my mind.
The two slit experiment involves two streams of photons which can be individually measured each aimed at a wall. A blocking surface with two slits is places between the emitters and the wall.
If the photon detectors are on the far side of the blocking surface, a "ripple" pattern shows up on the wall, demonstrating the interference patterns of the waves.
If the detectors are places at the photon sources, detecting each photon as it is emitted, no interference pattern emerges, only two bright dots where the stream hits. This shows the particle nature of photons. The results depend on how the experiment is observed.
The really weird thing about the experiment is that it happens independant of time. Experiments have shown that the result(wave form or particle stream) can occur BEFORE the measurements occur. That how the measurement is taken can alter the past, or something to that effect. Pick up the latest copy of Discover mag, and there's an article.
Re:light as particle (Score:2)
A proton is a quantized wave.
So is an electron.
Any particle stream behaves as a wave to some degree. The wavelength just gets extremely long as you get away from c, so the effect seems to disappear.
Re:Two slit (Score:2, Funny)
Re:Two slit (Score:3, Interesting)
Here's how you want to think about it:
1) Physically, we don't really understand the fundamental nature of photons (light). That is, we have no idea what they really are...
* BUT *
2) When you do an experiment that measures the wave properties of light, light acts like a wave.
AND
3) When you do an experiment that measures the particle properties of light, it acts like a particle.
EITHER WAY,
4) You cannot simultaneously measure the wave and particle properties of light. Measuring one destroys all information about the other.
OH, AND BY THE WAY...
5) The wave-particle duality of 1 - 4 goes for ALL matter, including 1972 Chevy Vegas.
You can calculate the wavelength of a 1972 Chevy Vega (automobile) using DeBroglie's hypothesis. The problem is that shooting cars at a wall with enough momentum to generate a diffraction pattern would require *immensely* unpractical amounts of energy (especially when you factor in the effect of relativity on the mass of the car.) Still, the principle has born out in experiment, as other larger traditional subatomic particles (neutrons, for example) have been shown to generate diffraction patterns when accelerated to high enough energies through appropriately sized diffraction gratings.
The reason we don't notice this kind of duality in real life is because Planck's contstant (a fundamental constant of nature that acts like a scaling factor for quantum phenomena) is very small in size compared to the scale of our normal macroscopic world. Like most of the bizarre stuff covered in modern physics, it's always there but the effect is muted on the scale you and I are able to normally perceive. You have to get to small sizes or large energies to have enough probability of observing quantum effects to make it worth your while.
P.S. Never play D&D with Physics majors - our DM never gave us wish spells because he knew we'd do stuff like changing fundamental constants of nature - i.e. resetting Planck's constant to 1 - high enough so we could quantum-tunnel through walls and stuff.
Milikan Oil Drop Experiment (Score:5, Interesting)
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
Re:Milikan Oil Drop Experiment (Score:2)
Incorrect! (Score:3, Informative)
Such a good story - it's a pity it is not true! Here's a link to David Goodstein's homepage [caltech.edu] - he's the vice-provost of CalTech - the second link on his homepage is a PDF file [caltech.edu] 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.
helium balloon and GR (Score:3, Interesting)
Oh but he is right. It is relevant. (Score:2)
The air in the back is more dense because the car is accellerating.
Similarly, the air is more dense near the surface of the earth because of gravity.
And as we all know, gravity and accelleration are indistinguishable (locally).
So. Both cause the balloon (via their effect on the atmosphere) to move opposite the vector the force is applied in.
(In this case, G + accelleration would put it on an angle, but your balloon is on a string.. etc.. etc..)
The Pitch Drop Experiment (Score:5, Interesting)
The Pitch Drop Experiment [uq.edu.au].
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."
Re:The Pitch Drop Experiment (Score:2, Insightful)
Re:The Pitch Drop Experiment (Score:3, Informative)
Commonly believed but untrue. (And I don't care what your high school/college physics teacher said.)
From Journal of Chemical Education, 1989:
The glassy state resembles a liquid in having short-range [molecular] order without long-range order
See http://www.urbanlegends.com/ for more.
Re:The Pitch Drop Experiment (Score:2)
Re:The Pitch Drop Experiment (Score:3, Insightful)
If you mean clear glass thicker at the bottom than the top, sometimes found in old English buildings, the Glass Flow page [urbanlegends.com] page at the Urban Legends page someone posted earlier says this is also an artifact of the way early clear glass panes were made. The slabs are uneven, and the builders install them with the thickest portion at the bottom to avoid unbalancing the panes.
If you still think glass is a liquid, tell me why Cartaginian glass, made thousands of years ago, are not puddles, and why obsidian shards milions of years old still have sharp edges.
WRONG! glass is NOT a liquid (Score:5, Informative)
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.
Re:WRONG! glass is NOT a liquid (Score:2, Insightful)
Furthermore, several of the windows have up to 1 inch gaps between the top of the pane and the window frame. Pray tell how that would happen if the glass was not slowly drooping.
Re:WRONG! glass is NOT a liquid (Score:3, Informative)
A. Glass does flow, over a GEOLOGIC TIMESCALE. In 200 years, a sheet of glass will not have changed as the result of normal flow.
B. Victorian windows are thicker at the bottom because their glass creation technique sucked at making thin sheets all the same size. There are gaps at the top of the windows because over time the wood SHRINKS because it wasn't pressure treated in victorian construction. This accounts for the gap and the thickness issue at the bottom.
So, yes, glass does flow, but you sure as hell aren't going to notice the effects in a 200 year old house.
Kintanon
Re:WRONG! glass is NOT a liquid (Score:4, Informative)
Glass does not flow. It is an amorphous solid with a shear viscosity well, well in excess of 1014.6 Poise, placing it well, well within the solid regime. If it flowed on even geologic time scales, flow would certainly be observed in telescope mirrors and other optics that are precise down to fractional wavelengths.
Jesus. Go read the link that was posted earlier. There's nothing pisses me off like people who ignore readily available information in favor of propagating the same old misinformation.
Re:The Pitch Drop Experiment (Score:2)
Re:The Pitch Drop Experiment (Score:2, Interesting)
Pitch is still used in the polishing of high quality optical components like lenses and telescope mirrors. The rumor is that at some optical fab shop they had a rather large barrel of pitch which they would chisel out chunks to melt and pour into polishing laps. After a couple of decades of work, they reached the bottom of the barrel, and found several hammers and chisels resting at the bottom, apparently having been left on top and slowly sunk through the entire volume of pitch.
It is a nice story, but it may be as false as the idea that glass is a liquid and flows under the force of gravity.
Not one, but two (Score:5, Interesting)
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.
Re:Not one, but two (Score:2)
Together they showed that light acts completely unlike anything we experience in the classical world.
Then the Davisson-Germer experiment came along and showed that electrons and even alpha particles behave exactly the same way.
Acceleration of gravity (Score:2)
We dropped the birdie onto a box with a microphone in it that stopped the timer when it heard the "thud". We dropped it from different heights and measured the time to fall and then plotted the results.
The beautiful thing wasn't learning that gravity is 9.8 m/s^2, but in showing us that from a fairly simple setup we could quantitatively measure something important in physics. We calculated the acceleration of gravity as well as the terminal velocity of the birdie. And our results were correct!
This was a great foundation to other experiments with interferometers measuring the wavelength of a laser, pendulums, exponential decay (of you name it -- cooling, capacitor discharge, etc.).
It's all in the shadows (Score:5, Interesting)
OT: Eratosthenes vs. Chris Columbus: True Hero? (Score:4, Informative)
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 [carlsagan.com]. 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
Re:OT: Eratosthenes vs. Chris Columbus: True Hero? (Score:2)
Re:OT: Eratosthenes vs. Chris Columbus: True Hero? (Score:2)
Not necessarily physics... how about math? (Score:3, Interesting)
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.
Re:Not necessarily physics... how about math? (Score:2, Informative)
Now if you came up with some function where you were not able to predict anything at all about the placement of the next dot (in the Sierpinski we know much about the next dot - namely that it will lie on the midpoint of the line drawn to the next vertex chosen) and still ended up with some deep fractal pattern that would be pretty cool.
I remember playing around with the mandlebrot fractal too and seem to remember that it is a bit harder to predict that shape ahead of time (but I could just not be remembering right).
Re:Not necessarily physics... how about math? (Score:2)
Re:Not necessarily physics... how about math? (Score:2, Insightful)
Two words (Score:2)
some renaissance classics... (Score:2)
Also, the related experiment using wires spaces n^2 distances apart, and listening for the resulting equal times between "clicks", which shows that the distance covered is proportional to the square of the time!
And then, how about Newton's extrapolation of the laws of gravity (observed by simple things like falling bodies) to the laws governing celestial bodies under the influence of gravity? This is pretty impressive, I think, to be able to predict successfully something that has no (near) physical equivalent that you were able to test beforehand!
Back to Basics (Score:2)
Re:Back to Basics (Score:4, Informative)
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.)
Re:Back to Basics (Score:2)
F = G * (m1 + m2)/r^2
a = G * m2 / r^2
The acceleration of mass 1 due to the gravitational field of mass 2 is solely dependent of on mass 2's mass.
This happens because of the lucky coincidence of the equivalence of inertial and gravitational mass. If these values varied by anything other than a constant amount the m1's in the equation would not cancel and you would end up in the situation you describe.
The physics changes slightly once General Relativity is taken into account, but only at speeds near c, or around object's whose escape velocity approaches c.
Rutherford's alpha scattering (Score:2, Interesting)
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.
Foucault pendulum too subtle (Score:2)
I have taught undergraduate differential geometry many times, and covered the relevant material (parallel transport of vectors along non-geodesics, holonomy) and frequently even reasonably strong students have a hard time with understanding it correctly. Particularly when I put a parallel transport question on an exam...
This Smithsonian FAQ [si.edu] has a bit about pendulums, but just says the relationship is complex. The California Academy has a page [calacademy.org] that is much better than a typical museum explanation in that it mentions that the amount of precession depends upon latitude and gives the relationship (precession is 2 pi sin(phi) where phi is the latitude) as well as making a reasonable effort at an explanation.
Gallileo's Gravity Experiment (Score:2)
What other experiment changed the world more in such a simple way as to drop 2 objects of diffrent Mass and show that gravity acts the same for each?
Archamedies I guess would also be. sitting in a tub to proove that diffrent densities displace diffrent amounts of water.
Measuring the height of a building... (Score:5, Funny)
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).
Re:Measuring the height of a building... (Score:3, Informative)
How some stuff gets to Score: 5, I will never know. Remember folks,
Google makes all computing simple [google.com].
Really. (Score:5, Interesting)
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.
Hovercup!! The best expirement (Score:5, Funny)
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."
Dropping a feather in a vacuum (Score:2)
I will nominate cold fusion (Score:2, Funny)
Wait a minute...
Interference (Score:2)
There are a whole class of experiments where old masters using (by modern standards) primitive equipment found results that were accurate even to modern standards and formed the basis of modern science:
Relativity (Score:2)
1) Look position of stars
2) Wait for solar eclipse
3) See that stars near moon have moved from where they should be.
Measuring the charge of an electron? (Score:2)
IANAP but I once saw a student at a science fair who measured the charge of an electron using standard off the shelf high-school lab equipment.
Instead of the very pure oil used by Millikan she used cooking oil. This introduced a lot of noise in the system, but quite amazingly when you plot out the results you can clealry see the impure oil component and the electron charge component. Subtract the impure oil component from your data, average out and report the result. She got the charge of the electron right to three significant digits of precision IIRC.
Marshmallows and the speed of light (Score:5, Informative)
Take a casserole dish, a microwave oven, and a bag of marshmallows and you can measure the speed of light. Details at http://www.physics.umd.edu/ripe/icpe/newsletters/
no Michelson-Morley? maybe just plain Michelson? (Score:3, Interesting)
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" [amu.edu.pl] (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. [knoxnews.com]
Shoot the monkey... (Score:2)
In a nutshell, drop an object with just gravity effecting it's fall and aim a projectile at it, since they fall at the same rate, the projectile will hit the falling object every time.
Of course, they always use a falling monkey and a sling shot in the text books, it just cracks me up.
If you want inexpensive... (Score:2, Funny)
Michelson measuring the speed of light... (Score:2, Interesting)
More info at a link I got from Google: http://www.phys.virginia.edu/classes/109N/lecture
S
What Constitutes Beauty in Physics? (Score:2, Interesting)
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
Fermi (Score:2, Insightful)
The monkey experiment (Score:4, Funny)
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.
Re:The monkey experiment (Score:3, Funny)
The real reason it still hits the monkey is that bullets are fucking fast.
Quantum Mechanics (Score:2, Interesting)
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?
Note: must change what people thought (Score:2)
Two slit interference, on the other hand, is a perfect case of what they're looking for. Of course, whether overturning existing ideas is a prequisite for beauty is another issue...
In molecular biology, I'd nominate the Crick and Brenner determination of codon size as the most beautiful ever.
Not F*****s P******m (Score:2)
Anyway doing Foucault's Pendulum is NOT easy. You need a LONG Pendulum, a SOLID building, a heavy bob and preferably no drafts
The Gent on the ModelEng list tried to do it in an old barn silo, and it didn't work, as the silo moved too much
BTW I was told that research at the University of Quito has shown that the Foucault Pendulum doesn't work
Fractals (Score:2)
There's also an experiment you can try if you have a handy particle accelerator; defocus it and fire some electrons at a sheet of lexan. Then touch a grounded wire to the side of the sheet. The electrons, embedded into the face of the plastic will rush to ground, creating pathways that other electrons will follow. The result is a fractal tree. You may have to play with the intensity and run-time, though.
Why not M-M? (Score:2)
My old high school had all of the required equipment (had a holography lab at one point).
Ice breaking steal (Score:2)
The "classic" version of the experiment is to fill a steal ball with water and seal it shut. If you place the ball in the freezer, the next day you'll find that the force of crystallization was stronger than the steal and the ball will be split in two.
My High School physics teacher got a hold of some liquid nitrogen and wanted to do whole experiment during class. So he prepared the steal ball, filled a glass beaker (yes, glass) with the liquid nitrogen, and set the ball in. As everyone gathered around up close to watch, he did have a brief moment of sanity and decided that, perhaps he should move the whole thing into a bucket instead. And maybe we shouldn't stand quite so close. So he poured the whole thing into a plastic (yes, plastic) bucket, added more liquid nitrogen to account for the increased volume, and we waited.
The force was not only enough to break the steal ball, but enough to shatter the bottom of the bucket too. He didn't have enough liquid nitrogren left to demonstrate that a rose will shatter if frozen, but we kinda saw that effect already...
Explosions! (Score:2)
The very best experiment, however, which certainly satisfied at least the "changed worldview" requirement, took place in the nevada desert in 1945, and was carried out primarily by physicists. Now, two kids go to their science fair:
Cindy - I measured the speed of light by observing jupiter's moons!
Kelly - I have first strike capability!
Who's going to win? I don't know how much enriched uranium you really need to make a nuclear bomb - all published figures are inflated - but they make lawn furniture out of it in the former soviet bloc, so I'm sure you can get some. After that you just need an enclosed container, an explosive, a little engineering knowhow and a healthy contempt for human life. With the plane tickets to and from eastern europe, I anticipate the whole deal costing less than $5,000 US for the fanatically inclined hobbyist. Admittedly, it costs more than a piece of cardboard with slits in it, but it's a lot more satisfying.
Hand drawn holograms (Score:3, Informative)
Some ideas... (Score:3, Informative)
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.
Frozen Waves (Score:2, Interesting)
Bowlingball on a string (Score:5, Funny)
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.
Plasma fire (Score:2)
A similarly interesting, and eventually decorative result, can be achieved by microwaving AOL CDs..
Measurement of the speed of light (Score:2)
Today's students (Score:2, Interesting)
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.
subsonic shaping (Score:2, Interesting)
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.
Pendulums (Score:3, Interesting)
Cloud Chamber (Score:3, Informative)
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 [cornell.edu]
- or an article from Scientific America [sciam.com]
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.Schrodinger's cat? (Score:2)
Triv
The superfluidity of Liquid Helium (Score:5, Interesting)
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.
Gliders in Conway's Life (Score:3, Insightful)
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.
Re:It's not a cookie mum it's a Newton (Score:2, Interesting)
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."
Furthermore... (Score:2, Interesting)