Great Experiments: Top Eleven

Posted by Chad Orzel on January 24, 2006
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Evil 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 least two different people in the comments comes to eleven, listed here in order of age:


  • 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 graviational constant G.
  • Michael Faraday ~1831: Discovery of electromagnetic induction.
  • Michelson and Morley ~1887: Disproving the existence of the luminiferous aether.
  • Heinrich Hertz ~1888: Creation and detection of electromagnetic waves.
  • Ernest Rutherford ~1909: Discovery of the nucleus of the atom.
  • Edwin Hubble ~1929: Determination of the distance to galaxies, and measurement of the expansion of the universe.
  • Rudolf Mossbauer ~1957: Discovery of the Mossbauer Effect and gamma-ray spectroscopy.
  • Alain Aspect ~1981: Experimental tests of Bell’s Inequality.

(Dates are pulled off Wikipedia, and hence highly approximate. In some cases, I’ve lumped together votes for two different experiments by the same person in order to draw up the list. Newton just barely squeaks on by this method, but he’s such a prickly bastard that it wouldn’t be wise to leave him off…)

It’s a pretty impressive list, really, spanning four centuries and a great many important and historic experiments. The list of people left out (go look at the comments to the other thread) is just as impressive.

So, here’s the plan. Over the next indeterminate period of time, I will endeavor to write up short pieces describing the various experiments and observations on the list, and where they fit in the history of modern physics. After that, if I haven’t lost interest, I may put it up for another vote, which I promise will be every bit as scientific as the last one.

If you’d like to complain about voting irregularities, or castigate me for leaving out your personal favorite experiment, well, you know where the comments are.

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Comments

  1. #1 anon.
    January 24, 2006

    I should have commented on the original thread, but I find the lack of recent high-energy physics experiments a little surprising. It’s hard to know which one to pick, but surely something like the discovery of the W and Z bosons is important, and took a phenomenal effort on the part of many talented people. Elegant experiments done by one person or a small group are wonderful, but we shouldn’t overlook the contributions of members of huge collaborations either.

  2. #2 Ponderer of things
    January 24, 2006

    Excellent list. Subjectively,
    I would also mention:

    J. J. Thomson’s discovery of electron
    Roentgen’s discovery of x-rays
    Kamerlingh Onnes’ discovery of superconductivity

    I would remove Aspect’s Bell inequality as the most recent and more field-specific discovery that has yet to be put in proper perspective scientifically

    If one wanted to include more recent (past 4 decades) experiments, I would mention discovery of high-Tc superconductivity and maybe quantum hall effect.

  3. #3 Anonymous
    January 24, 2006

    Small nitpick: Didn’t Newton do most of his physics work well before 1700? I thought he would’ve done those experiments in the 1660s or early 1670s, which would put him before Roemer. By 1700 he had pretty much given up physics and was spending all his time on alchemy and running the Mint, IIRC.

  4. #4 Mike Molloy
    January 24, 2006

    Wikipedia supports an earlier date for at least some of Newton’s work in optics, citing dates of 1670-1672, during which time Newton lectured in optics at Trinity. However, the book, Opticks, was (again per Wikipedia) written in 1704.

    According to Westfall (page 640), virtually all the work reported in the 1704 book was from the early 1670s:

    “As far as out understanding of Newton’s scientific thought is concerned, the Opticks contained nothing new. With only the smallest exceptions, it presented work he had completed more than thirty years earlier, and the exceptions belonged to the early 1680s.”

  5. #5 Chad Orzel
    January 25, 2006

    Small nitpick: Didn’t Newton do most of his physics work well before 1700? I thought he would’ve done those experiments in the 1660s or early 1670s, which would put him before Roemer. By 1700 he had pretty much given up physics and was spending all his time on alchemy and running the Mint, IIRC.

    I picked 1700 as an approximate date because he didn’t publish the “Opticks” work until after 1700. It’s easier to find the publication dates than to determine when a given experiment really happened.

    The ordering isn’t terribly important, anyway. “Approximate by age” seemed to make more sense than “alphabetical” in this case, that’s all.

  6. #6 Chad Orzel
    January 25, 2006

    I should have commented on the original thread, but I find the lack of recent high-energy physics experiments a little surprising. It’s hard to know which one to pick, but surely something like the discovery of the W and Z bosons is important, and took a phenomenal effort on the part of many talented people. Elegant experiments done by one person or a small group are wonderful, but we shouldn’t overlook the contributions of members of huge collaborations either.

    It is a little surprising, given the prominence of particle physics in the public picture of physics. I think there are really two problems (other than the fact aht I’m not a particle physicist, and I’m not widely read by particle physicists): first, the lack of a single, defintie public face to associate with those experiments, and second, the sheer complexity.

    After the first half-dozen or so particles that were detected, the rest of the detections are mostly indirect. Nobody sees a single top quark shooting out of their apparatus, they see a spray of other particles that are inferred to be due to the decay of a top quark. That’s kind of hard to explain to the laity.

    I think that’s why particle theorists are better known than particle experimentalists.

    Ponderer: I would also mention:

    J. J. Thomson’s discovery of electron
    Roentgen’s discovery of x-rays
    Kamerlingh Onnes’ discovery of superconductivity

    Onnes was mentioned, but only once. He’d be a good choice, but those are the breaks.

    I would remove Aspect’s Bell inequality as the most recent and more field-specific discovery that has yet to be put in proper perspective scientifically

    I’ll make the case for Aspect later on. I think that the Bell inequality tests really are an important and fundamental development, but then, I’m in the same basic field, so I would…

  7. #7 OwnedByTwoCats
    January 27, 2006

    What about the initial discovery of radioactivity? The Curies?

    Or the initial discovery of nuclear fission?

    One problem with the latter discovery is that the discoverers got it wrong for quite a while; fission by-products were misidentified as a the by-products of a new transuranic element.

  8. #8 OwnedByTwoCats
    January 27, 2006

    Milliken measuring the charge of an electron.

  9. #9 Gustavo
    February 27, 2006

    De fijo gana Galileo, es mi heroe, a pesar que soy Católico

  10. #10 Ryan Vilim
    October 26, 2006

    I suppose I am posting about 10 months after the story, but I nominate the Stern-Gerlach experiment and the double slit experiment (in all its incarnations).

    The Stern-Gerlach experiment is a fantastically good example of an experiment that has absolutely no classical equivalent.

    The double slit experiment is particularly good when you consider that it showed that light could interfere (aha! its a wave!), and then a hundred years later, showed that a single photon, and matter could interfere with itself (aha! my brain is going to explode!)

    Oddly enough, this got me thinking of the photoelectric effect. It is often taught as the final proof of the quantized nature of light. Its what Einstein got his Nobel Prize for.

    The funny thing is that in the 60s, some guys named Jaynes and Lamb showed that the entire result could be explained without the notion of a quantized photon at all, as long as you kept the atom quantized.

    I got this out of a book, which I regrettably don’t have the title for. My undergraduate thesis advisor photocopied me the second chapter of it after I realised I had no idea what a photon was.