Brian Cox proves Galileo right

March 5, 2015 • 2:00 pm

Speaking of the Infinite Monkey Cage, Matthew contributed this related post—about Cox’s BBC show last year:

by Matthew Cobb

For reasons that will eventually become clear, I’m reading about Galileo right now, and I thought readers would like to see this great reconstruction of Galileo’s law that objects fall at the same speed, irrespective of their weight. Legend has it that Galileo dropped two objects off the leaning tower of Pisa, it seems in fact that this was a “thought experiment”. And of course, if you do try dropping a bowling ball and a feather, they will fall at different rates because of air resistance. Unless, of course, you do it in a vacuum.

Which is what my University of Manchester colleague (and Jerry’s co-host on the Infinite Monkey Cage Live), Brian Cox, did for his programme Human Universe last year. Part of the fun of this brief (< 5 mins) clip – apart from the mind-boggling Einsteinian twist at the end, so keep going, it’s worth it – is the glee and amazement on the faces of the people who run the facility. Everyone knows that Galileo was right, but seeing it happen in such dramatic fashion is still stunning:

An even more dramatic demonstration of Galileo’s idea took place on the Apollo 15 lunar mission, when Commander David Scott dropped a hammer and a feather on the moon:

76 thoughts on “Brian Cox proves Galileo right”

  2. It was amazing to see those feathers bend, twist and bounce.

    PS It’s all faked, it’s all a conspiracy! 😉

    1. You got it, man. Let’s not abdicate scepticism.
      Anybody who can first explain how they were faked (the two vids) gets a copy of WEIT with a cat drawn in.

  3. What is interesting is to see how a physicist and the seasoned engineers running this facility got exited, just like children. They convey the message that indeed science is cool.

    1. I would have acted the same, but at the same time I couldn’t help laughing at the countdown and everything like it was a shuttle launch. 🙂

      It was VERY cool though!

  4. A beautiful test. I hope kids in high school science classes all over the world have a chance to watch this trick.
    I’m surprised that the staff at the lab seemed so surprised. Hadn’t they thought to try this on their lunch break already? I would have.

    2. I imagine it’s quite a costly exercise pulling down the vacuum, which might preclude doing it for a bit of lunch break messing around. The tv show doubtless provided a budget to do it.

      1. It was totes amazeballs!

        He went full Bronowski. Or was it Sagan? Anyway, loved it.

          1. I watched in ABC iview, which only has episodes up for a couple of weeks after broadcast. At the moment they’ve got 2 eps of something called ‘Out There’ with Stephen Fry, might be worth a look. Not sure if it works outside Oz.

          2. I think I saw a couple of those Stephen Fry Out Theres. He had recently come out as gay and travels around the world talking to people about homosexuality. Being Fry, it was very intelligent, touching, and funny.

  7. It is even more amazing than listening to the English pronounce Aluminum. I guess it’s a syllables question.

      1. In college I knew a fellow from Hong Kong who had a Cockney-ish accent and pronounced “mahogany granite” as “mehockney graynight.” As a West Coast American I’ve always been a little jealous of people with fun accents. I realize we have an accent, too, technically, but it’s largely the no-accent accent: we pretty much pronounce all the vowels, and just as they are written. Bo-ring, and I’m pretty sure the rest of the English-speaking world thinks so, too.

      2. In college I knew a fellow from Hong Kong who had a Cockney-ish accent and pronounced “mahogany granite” as “mehockney graynight.” As a West Coast American I’ve always been a little jealous of people with fun accents. I realize we have an accent, too, technically, but it’s largely the no-accent accent: we pretty much pronounce all the vowels, and just as they are written. Bo-ring, and I’m pretty sure the rest of the English-speaking world thinks so, too.

  8. I can’t wait to find out the reason you’re reading about Galileo. I liked Dava Sobel’s Galileo’s Daughter, and Kim Stanley Robinson’s novel featuring him …

    As I started reading the post, I hadn’t seen the 2nd clip yet, but immediately thought, “the demonstration on the Moon!”.

    Great stuff.

    1. As luck would have it, the journal Science (celebrating 100 years of relativity theory!) has a news article about the drop test. Quote: “About a year from now, a satellite will blast into orbit to perform the legendary test more precisely than Galileo could have imagined. ” (about the MicroSCOPE project).

      Link here, probably not freely accessible: http://www.sciencemag.org/content/347/6226/1096.full

  9. I think Philomena Cunk might introduce this segment by saying:

    “But ‘oo, or wha’, is vacuums?”

    1. “Simply speakin’, vacuums is the best way we’ve come up with to vacuum your carpet.”

        1. Among my Anglophilic fetishes are the various sentence-ending clauses that I guess we use in the U.S. but nowhere near as colorfully: “then,” “innit,” and my very favorite “do I?” As in “Oy don’ ‘ave no f**king oydea, do I?” Love!

  10. How in the world did Gallileo figure that out w/o the aid of a vacuum? There are times when genius appears almost prescient.
    Dave Scott’s testing of this hypothesis is one of my favorite moments in NASA history.
    Conducting an experiment in the lunar surface and then casually stating that “Gallileo was right,” is about as cool as it gets.

    1. If I recall correctly, the original theory was that objects fell at a speed proportional to their mass. Now a bowling ball (or a cannon ball, as I think it was in the original experiment) is lots heavier than a feather; but a cannon ball is surely significantly heavier than a musket ball, so you can do the experiment in air perfectly well as long as air resistance is significantly less than gravitational force.

      1. Galileo did his gravity experiments by rolling balls down ramps on his lab bench. I think his experience with this led him to speculate the equal time idea. I don’t remember that there was anything in his notes that talked of actually testing it directly.
        Anyone…?

        1. I read somewhere that Galileo’s writings contain a reference to the large sphere landing slightly ahead of the small one, but far from what would be expected from speed proportional to weight. That implies that he at least saw the experiment being performed, and also that he had some inkling of air resistance.

    2. Gallileo had a nice argument that, in brief, went like this:

      Suppose we have a small light ball and a large heavy ball.

      We assume that the light ball falls slower than the heavy ball.

      What then happens if we connect the light ball to the heavy ball, say with a string?

      The two together will fall slower than the heavy ball because the light ball retards the fall.

      But the combination is heavier than both the light and the heavy ball, so this is a contradiction to the view that heavier objects fall faster than light ones.

      1. Thanks for the reminder. That Italian math man was quite some thinker. He deserves much admiration.

      2. The argument is fallacious. Well, the conclusion is true obviously, but the argument itself is invalid.

        I think the failure comes when the concept of retardation is introduced. This is, of course, caused by the object’s inertia and the apparent contradiction caused by tying the two objects together is a tacit acknowledgement that inertia and mass (that causes the falling) are really the same thing.

        If you are still unconvinced, try the analogous argument using electric charge.

        Suppose we have a ball with a small positive charge and a ball with a large positive charge (both balls have the same mass) and a negatively charged infinite plate

        We assume that the smaller charge moves to the plate slower than the larger charge.

        What then happens if we connect the small charge to the large charge, say with a string?

        The two together will move slower than the large charge because the small charge retards the movement.

        But the combination has a larger charge than either the small or large charge, so this is a contradiction to the view that larger charges objects are attracted to oppositely charged plates faster than smaller charges.

        In reality, of course we find that the smaller charge really does retard the larger charge (and the larger charge pulls the smaller charge along) when they are tied together and there is tension in the string.

        1. Interesting idea. My question is when Galileo tied his balls together, they clearly would behave as on larger mass. You might as well glue them together.
          With the electric charged balls, tied with an insulator string, are they simply going to act as a single object with a larger charge? Or do they maintain independence? Know what I mean?

          1. Almost all arguments in physics are invalid, then. In the electrostatic case, the two balls accelerate unequally because their charge:mass ratios are different. The analogous quantity in Galileo’s case is the ratio of gravitational mass to inertia, which we now ‘know’ to be constant.

            If Galileo had already known Coulomb’s Law he might have jumped straight to General Relativity instead of failing to get as far as Newton (who also didn’t know from electricity), but it didn’t happen like that.

  11. I may be wrong about this, but the bit at the end about Einstein vs Newton is somewhat misleading. A Newtonian account of gravity as an attractive ‘force’ can fully explain the fact that two objects with different masses fall to earth at the same rate (an acceleration of 9.8 m/s^2). This is because the forces on the two objects are different, as according to Newton’s law of gravitation, F=G x (Earth’s mass x Object’s mass)/r^2 and the masses are different. Since the force is larger for the object with the larger mass, but its mass is also proportionately larger, the acceleration stays the same (i.e., it is independent of the object’s mass).

    1. I hope Jerry revisits his preview of this book, now that it is out. It has some fascinating stuff about the rise and fall and re-rise of science under different political and religious environments, but it also has some very poor discussions of the nature of science and naturalistic assumptions. These problematic statements were presaged in the Introduction that Weinberg gave to Jerry to post. We had hoped that the main text would be clearer, but if anything the main text is worse than the Introduction on this subject.

  13. Who would’ve thought that the home of the world’s biggest vacuum chamber would be…Cleveland, OH — my hometown? Nice to hear “Cleveland” and “vacuum” in the same sentence without the latter being preceded by the modifier “cultural” — a characterization that I, as a native son and proud alumnus of CWRU (home of the famous Michelson-Morley experiment) can vouch is untrue.

      1. The best! Its Severance Hall home is a short stroll around the block from my old school off University Circle. I was there in time to see Lorin Maazel conduct.

      1. No need to tell me, a long-suffering Tribe fan. And as any long-suffering Tribe fan can tell ya, they pretty much have sucked since ’59, when “Trader” Frank Lane swapped Rocky Colavito to the Tigers for a fruit-peddler name o’ Harvey Kuenn.

        1. But Progressive Field looks like a lovely place to spend the day. They beat the pants off of the Reds yesterday – and thanks to inter-league play, they will have chances to repeat during the regular season.

          1. My people there still call it “The Jake” (after its earlier name, Jacobs Field). Yes, it’s a fine place to see a ballgame, and I try to get back to catch one every season. Unfortunately, when I lived there, the Tribe played in creaky, old Municipal Stadium, where sometimes hundred of fans
            would cram into its 78,000 seats, and a
            chill Lake Erie wind always seemed to be whipping over the bleachers.

            Any day a Cleveland team beats a Cincinnati team is a good day. (I had a T-shirt with a picture of an Interstate-71 sign saying “Cleveland 240 miles” and a caption below reading “The only sign of life in Cincinnati”.)

  16. I’m not sure what the release mechanism is but it must be nicely engineered to ‘let go’ without imparting any ‘snatch’ or sideways velocity to the feathers in particular. What I found almost more impressive than the speed was the fact that they fell straight down.

  17. Oh, and the moon experiment was visibly in slow-motion. (Okay, reduced gravity).

  20. “Galileo, king of night vision, king of insight.”

    Anyway, while we’re talking about the guy, I strongly recommend _Galileo: Watcher of The Skies_ as a very well written recent biography. Like many of the recent biographies of 17th century figures, this does not attempt to whitewash their antichristianity.

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