字幕表 動画を再生する 英語字幕をプリント Balancing a pencil or any other tough, heavy object on its tip, is quite a precarious task. It is easy to see why tough heavy object 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 in too! Physicist calls this kind of tipping an...Inverted Pendulum. Because its kind of, like…an upside-down pendulum. And careful mathematical analysis of Inverted Pendulums...will tell you the obvious, they’re really… unstable. In fact, this equation predicts that if a perfectly balanced pencil with a perfectly-sharped tip, will do get nudge, off balance, by just one ten thousandth 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 the robots, they can balance and, catch and throw, upright sticks! And the people who make... seemingly impossible, artistic, rock stacks. But in all these cases, keeping the objects balance, 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 better get rid of the air bumping in besides the pencil. Since the kinetic energy of a typical oxygen molecule, is enough to destabilize the pencil. Remember, if the pencil gets off center by even ten thousandth of the width of an atom, it would fall down in, under three seconds. And you better cool the pencil and table down as close to absolute zero, as you can... since the thermal jiggling of their atoms when they're hotter, are similarly jiggle the pencil off balance. But even then, matter add very small scales has spread out wape like nature which means that you cannot have both pencil perfectly upright, and not moving at the same time. And while this "quantum effect" is never a real life inhibitor of the precarious pencil balancing? It means, you never even could succeed... However, it is 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 nineteen centimeter pencil was one point three seconds. Do you think you can beat that? This minute physics video is brought to you by audible.com one of the leading providers online, audio books, and all types of media, either fiction, non-fiction, and periodicals.. I'd like to recommend "The Tipping Point" by Malcolm Gladwell this week. It is a book about exponential increases and spreads of trends, social trends, academic, that sort of thing, and...the mathematics of, the mathematics of... balancing an object, on its...tip, so...anyway,"The Tipping Point", by Malcolm Gladwell, audible.com, supports minute physics. Without them, we won't be able to do... what we do! So, thank you to audible and have an audible.com/minutephysics to get your free audio book.