How Long Can You Balance a Pencil?

How Long Can You Balance a Pencil?


Balancing a pencil or any other top heavy object on its tip is quiet precarious task It’s easy to see why top heavy objects are unstable They just…Wanna fall down Any little nudge will put it off balance with gravity happy to pull its center of mass even more off balance and the more off balance it is, the more gravity pulls until… Physicist call this kind of tipping an Inverted pendulum, becouse it´s kind of like upside down pendulum. And careful mathematical analysis of inverted pendulums will tell you the obvious: They’re really unstable. In fact, these equations predict that if a perfectly balanced pencil with a perfectly sharp tip were to get nudged off balance by just 1/10000th of the width of an atom, it would take only three seconds to fall over. There are indeed acrobats who can balance poles with other acrobats on top, and robots that can balance and catch and throw upright sticks, and people who make seemingly impossible artistic rock stacks. But in all these cases, keeping the objects balanced either requires an active stabilization effort, or else carefully taking advantage of the fact that the balancing point isn’t actually a point. So the question is this: can you balance a pencil sharpened to a perfect single atom wide tip on its tip, without active stabilization? Well, to start, you’d better get rid of all the air bumping off the sides of the pencil, since the kinetic energy of a typical oxygen molecule is enough to destabilize the pencil Remember: if the pencil gets off-centered by even 1/10000th the width of an atom, it’ll fall down in under three seconds. And you’d better cool the pencil and table down as close to absolute 0 as you can, since the thermal jiggling of their atoms when they’re hotter will similarly jiggle the pencil off balance. But even then, matter at very small scales has a spread-out, wave-like nature which means you can’t have both the pencil perfectly upright and not moving at the same time. And while this quantum effect is never a real life inhibitor of precarious pencil balancing, it means you never even COULD succeed. However, it’s still fun to see how long you can keep a pencil balanced on your fingertip. The shorter the pencil, the harder it is. My best time for a standard 19 cm pencil was 1,3 seconds. Think you can beat it? This minutephysics video was brought to you by Audible.com, one of the leading providers of online audiobooks across all types of media including fiction, non-fiction, and periodicals. I’d like to recommend The Tipping Point by Malcolm Gladwell this week. It’s a book about exponential increases in spreads, uh, trends, social trends epidemics, that sort of thing. And, uh, it’s – the mathematic is somewhat related to the mathematics of balancing an object on its… tip, so, anyway, The Tipping Point, by Malcolm Gladwell. Audible.com supports minutephysics and without them, we wouldn’t be able to do what we do, so… Thank you to Audible, and, uh, head to audible.com/minutephysics to get your free audiobook.

100 thoughts on “How Long Can You Balance a Pencil?”

  1. Yes but a pencil isn't 1 atom wide at the tip. If you were going to use a typical pencil it would require much less effort.

  2. You forgot to mention the rotation of the Earth. Even if you managed to perfectly balance it with no air, etc. The Coriolis effect would cause it to tip over. You would need to be on the north pole, at absolute 0, perfectly balance.

  3. Atoms still have kinetic energy at absolute zero. And cooling down just decreases it. Otherwise itd break Heisenbergs principle

  4. Hey wouldn't it be more stable if the pencil in shorter, because center of gravity is close to ground.

  5. It's actually pretty easy to do this with a peacock feather on your palm. Edit: Just realized this video was published 5 years ago, it somehow got on my recommended.

  6. Putai** c’est sérieux là ! Il y a 10000 langue de sous-titres sauf en Français 🇫🇷 ! Limite si c’est fait exprès 🤬

  7. You can't put something with a sharp edge into perfect balance.
    But you can if you give it support.
    -minute psychics 2014

  8. My record for pencil balancing is 8 years and counting. It's a simple task to keep a pencil upright on its point on a table. You just need a good hammer :3

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