Experiment
drorzel | February 19, 2006A preliminary report on the standings in the Greatest Physics Experiment voting:
Michelson-Morley: 13
Faraday: 7 (including one vote in the Farady post)
Roemer: 5
Aspect: 4.5 (one indecisive person voted for both Cavendish and Aspect)
Galileo: 3
Rutherford: 3
Cavendish: 1.5
Hertz: 1 (in the comments to the Hertz post)
Newton, Hubble, and Mössbauer are currently getting shut out.
Voting will remain open for another couple of days, so if you're a backer of somebody other than Michelson and Morley, you've still got time for a late charge: round up some friends, and get out the vote.
drorzel | February 16, 2006The Top Eleven is now complete. Here's the full list of experiments, with links to my summaries:
Galileo Galilei: ~1610: Discovery of the moons of Jupiter, and measurements of the acceleration of falling objects.
Ole Roemer ~1675: Measurement of the speed of light by timing the eclipses of Io.
Isaac Newton ~1700: Dispersion of light and measurements of circulating fluids.
Henry Cavendish, ~1797: Measurement of the gravitational constant G.
Michael Faraday ~1831: Discovery of electromagnetic induction.
Michelson and Morley ~1887: Disproving the existence of the luminiferous aether.
Heinrich…
drorzel | February 16, 2006The final and most recent of the Top Eleven is an experiment that goes right to the heart of the weirdness inherent in quantum mechanics.
Who: Alain Aspect (1947-present), a French physicist. (Again, Wikipedia is a let-down, but CNRS has useful information.)
When: Around 1982 (there are several experiments involved, but the 1982 one is cited by most people).
What: His group performed the first experimental tests of Bell's Inequality, which shows that the predictions of quantum mechanics cannot be explained by a "local hidden variable" theory. Explaining that will take some space, so I'll…
drorzel | February 13, 2006The penultimate experiment in the Top Eleven brings us up to the first nominee who's still with us..
Who: Rudolf Moessbauer (1929-present) (that's Mössbauer with a heavy-metal ö), a German physicist. (The Wikipedia link is for consistency with the other posts, but contains very little information. A better bio is available from the Nobel Prize site.)
When: 1957-58.
What: This one requires a bit of background, so there will be more below the fold, but basically, he's nominated for discovering an effect that makes it possible to do precision spectroscopy of nuclear transitions.
Spectroscopy is…
drorzel | February 10, 2006The next experiment in the Top Eleven is a set of observations, not an experiment.
Who: Edwin Hubble (1889-1953), an American astronomer, and the guy the Hubble Space Telescope is named after.
When: He was nominated for two related but different discoveries which were announced in 1924 and 1929.
What: Hubble's most famous work concerns galaxies: first, he proved that they were, well, distant galaxies, and then he showed that they were receding from us with a velocity proportional to their distance, which is the first piece of evidence leading to the Big Bang model of the universe. (More after…
drorzel | February 8, 2006The eighth of the Top Eleven is an experiment by the man who set the gold standard for arrogance in physics.
Who: Ernest Rutherford (1871-1937), a New Zealand-born physicist who famously declared "In science, there is only physics. All the rest is stamp collecting." He was awarded the Nobel Prize in Chemistry in 1908.
When: He's nominated for the alpha-particle scattering experiments that showed the existence of the nucleus, an 1909.
What: Rutherford is famous for carrying out early experiments with radioactive substances. Among other achievements, he coined the terms "alpha, beta, and gamma…
drorzel | February 7, 2006The seventh entry in the Top Eleven is an experiment that leads directly to all forms of wireless communications.
Who: Heinrich Rudolf Hertz (1857-1894), a German physicist.
When: 1886
What: Hertz studied electromagnetism, and in particular, the prediction from Maxwell's Equations that it ought to be possible for electromagnetic waves to travel through free space. Today, this is a simple demonstration-- you grab a couple of loops of wire, a signal generator, and an oscilloscope, but in 1886, it required the invention of a good deal of apparatus.
In order to show that electromagnetic waves…
drorzel | February 1, 2006The next experiment in the Top Eleven is probably the most famous failed experiment of all time.
Who: Albert Michelson (1852-1931) and Edward Morley (1838-1923), American physicists.
When: Their first results were reported in 1887.
What: The famous Michelson-Morley experiment, which tried and failed to detect the motion of the Earth through the "luminiferous aether." At the time, light waves were believed to be disturbances in some medium that permeated all of space, and was fixed in an absolute sense. In this picture, objects moving through space should also be moving relative to the aether…
drorzel | January 30, 2006Next up in the Top Eleven is a man who is largely responsible for the fact that we have electricity to run the computer you're using to read this.
Who: Michael Faraday (1791-1867) a poor and self-educated British scientist who rose to become one of the greatest physicists of the 19th Century.
When: Around 1831.
What: Faraday's main achievement was the discovery of Faraday's Law (obviously), one of "Maxwell's Equations" describing the behavior of electric and magnetic fields (in a certain sense, Maxwell was a master of PR-- he took a bunch of equations that other people had already discovered…
drorzel | January 27, 2006Next up in the Top Eleven is an experiment whose basic technique is still in use today.
Who: Henry Cavendish (1731-1810), a British scientist who made a number of discoveries in physics and chemistry, but received credit for very few of them.
When: 1797.
What: Cavendish's modern claim to fame is the torsion pendulum experiment, an idea that originated with John Michell, who died before completing it.
The apparatus for the famous experiment, shown at left, consists of a dumbell-shaped pendulum hung from a very fine wire. Two larger masses (Cavendish used 350 lb lead spheres) are brought near…
drorzel | January 25, 2006Third in the Top Eleven is Sir Isaac Newton, who squeaks in with two nominations for two different experiments.
Who: Isaac Newton (1642-1727), famous English physicist, mathematician, alchemist, Master of the Mint, and Neal Stephenson character.
When: Newton was secretive and reluctant to publish anything, so it's sort of hard to assign dates. I'm going with "About 1700."
What: Newton pretty much kicked off modern science, so you could go on for a long time about his various accomplishments, but he was cited for two specific experiments: splitting white light with a prism, and measuring the…
drorzel | January 25, 2006The second in the Top Eleven is the first quantitative measurement of the speed of light, by Ole Christensen Roemer (whose last name ought to contain an o-with-a-slash-through-it, that I've rendered as an "oe").
Who: Ole Roemer (1644-1710), a Danish astronomer.
When: The crucial observations were made around 1675.
What: Roemer made careful observations of the orbit of Jupiter's moon Io (which circles the planet once every two days or so), and noted that the time between eclipses of Io (times when it disappeared behind Jupiter) got shorter as the Earth moved closer to Jupiter, and got longer…
drorzel | January 24, 2006The first and oldest of the experiments in the Top Eleven is actually a two-fer: Galileo Galilei is nominated both for the discovery of the moons of Jupiter, and for his experiments on the motion of falling objects.
Who: Galileo Galilei (1564-1642), the great Italian physicist, astronomer, and general Renaissance man.
When: He's known to have made the first observations of the moons of Jupiter around 1610. The dates of the experiments on accelerated objects are fuzzier, but around the same time.
What: Shortly after obtaining a telescope (after its invention by Dutch astronomers), Galileo…
drorzel | January 24, 2006Evil elves have apparently snuck into the house in the middle of the night, and stuffed my sinuses with cotton and motor oil (the dog is sitting here muttering "I told you there were evil elves out there but did you listen? 'Stop barking at nothing,' you said..." Or maybe that's the drugs.). This sort of cuts down on my ability to think Deep Thoughts and post the results here.
I can, however, carry out mechanical tasks like tallying the nominations for the Greatest Physics Experiment (to go with Clifford's Greatest Physics Paper on the theory side). The list of experiments mentioned by at…
drorzel | January 19, 2006In the ongoing string theory comment thread (which, by the way, I'm really happy to see), "Who" steps off first to ask an interesting question:
One way to give operational meaning to a theory being predictive in the sense of being empirically testable is to ask
What future experimental result would cause you to reject the theory?
I think what worries a lot of people about string thinking is that it seems so amorphous that it might be able to accomodate any future experimental measurement. In fact I am not aware of any string theorist's answer to this basic question.
It's an interesting…
drorzel | January 16, 2006Today is the last day to vote in Cosmic Variance's Greatest Physics Paper contest. If you haven't voted yet, go over there and pick a paper.
Locally, I'm still collecting nominees for the Greatest Physics Experiment. A quick scan through the comments gives the current list as:
The Michelson-Morley experiment disproving the aether.
Rutherford's discovery of the nucleus.
Aspect's Bell Inequality test.
Galileo's inclined planes, or possibly the discovery of the moons of Jupiter.
The Mossbauer Effect.
If you have a favorite physics experiment, and don't see it on that list, go leave a comment…
drorzel | January 14, 2006The big news in physics yesterday was the announcement that a private donation has been made to support experiments at the Relativistic Heavy Ion Collider on Long Island. This is the accelerator that's slamming gold nuclei into each other to create a quark-gluon plasma, along with a million dippy stories about how it might make a black hole that will eat the whole New York metro area. This isn't my field (not by a long shot), but I think this is terrifically exciting work, not least because the observations that they've made confound existing theories-- the "plasma" acts more like a liquid…
drorzel | January 13, 2006Looking at the ScienceBlogs front page, I suspect that I may be well out of my league, especially when it comes to posting frequency. There's just no way I can post that many entries in one day, especially not a day like Thursday.
In addition to my lab this morning (in which half the students were using a Michelson interferometer to measure laser wavelengths and the index of refraction of air, while the other half measured the speed of light-- it was like a "Greatest Experiment Nominee" re-enactment event. Only with lasers...), we had a visit from Dave DeMille of Yale, who I had invited a…
drorzel | January 11, 2006Quite a while back, Clifford Johnson at Cosmic Variance had a post seeking nominations for "The Greatest Physics Paper Ever." Back after a long hiatus, he's now holding a vote among five finalists: Isaac Newton's Principia Mathematica, Albert Einstein's General Relativity, Emmy Noether's paper on symmetry and conservation laws, Dirac's theory of the electron, and the Einstein, Podolsky, and Rosen paper on quantum non-locality.
(Newton's Principia Mathematica had a comfortable lead when I last checked, so if you're a partisan of one of the other candidates, go over there and vote...)
Of course…