[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:09.76,0:00:15.36,Default,,0000,0000,0000,,In problem solving as in street-fighting:\NRules are for fools!
Dialogue: 0,0:00:15.36,0:00:18.80,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:00:18.80,0:00:24.28,Default,,0000,0000,0000,,(Applause)
Dialogue: 0,0:00:25.60,0:00:29.40,Default,,0000,0000,0000,,Let's see how far we can go\Nby bending rules
Dialogue: 0,0:00:29.40,0:00:32.63,Default,,0000,0000,0000,,as we estimate the fuel efficiency,\N
Dialogue: 0,0:00:32.63,0:00:36.55,Default,,0000,0000,0000,,the miles per gallon of a 747.
Dialogue: 0,0:00:36.55,0:00:40.26,Default,,0000,0000,0000,,The fuel is used to fight drag,\N
Dialogue: 0,0:00:40.26,0:00:41.90,Default,,0000,0000,0000,,the force of air resistance,
Dialogue: 0,0:00:41.90,0:00:43.26,Default,,0000,0000,0000,,what you would feel
Dialogue: 0,0:00:43.26,0:00:45.84,Default,,0000,0000,0000,,if you stuck your hand \Nout of a moving car --
Dialogue: 0,0:00:45.84,0:00:47.81,Default,,0000,0000,0000,,don't try this at home --
Dialogue: 0,0:00:47.81,0:00:51.19,Default,,0000,0000,0000,,or try to run in a swimming pool.
Dialogue: 0,0:00:52.14,0:00:55.27,Default,,0000,0000,0000,,There are at least two ways \Nthat you can use
Dialogue: 0,0:00:55.27,0:00:57.98,Default,,0000,0000,0000,,to figure out the drag.
Dialogue: 0,0:00:57.98,0:01:01.53,Default,,0000,0000,0000,,You could spend \N10 years learning physics
Dialogue: 0,0:01:01.53,0:01:04.56,Default,,0000,0000,0000,,and you write down \Nthe Navier–Stokes equations:
Dialogue: 0,0:01:04.56,0:01:08.26,Default,,0000,0000,0000,,the differential equations\Nof fluid dynamics.
Dialogue: 0,0:01:08.26,0:01:12.28,Default,,0000,0000,0000,,And then you spend another\N10 years learning mathematics
Dialogue: 0,0:01:12.28,0:01:14.75,Default,,0000,0000,0000,,to solve for the pressure.
Dialogue: 0,0:01:14.75,0:01:16.73,Default,,0000,0000,0000,,And whereupon you find
Dialogue: 0,0:01:16.73,0:01:18.71,Default,,0000,0000,0000,,that actually there's no exact solution\N
Dialogue: 0,0:01:18.71,0:01:21.18,Default,,0000,0000,0000,,for the flow around a 747,
Dialogue: 0,0:01:21.18,0:01:23.49,Default,,0000,0000,0000,,or, in fact, for most of the situations\N
Dialogue: 0,0:01:23.49,0:01:25.55,Default,,0000,0000,0000,,which you want to know.
Dialogue: 0,0:01:26.44,0:01:29.07,Default,,0000,0000,0000,,Rigor, the rigorous approach,
Dialogue: 0,0:01:29.07,0:01:33.02,Default,,0000,0000,0000,,the exact approach\Nhas produced paralysis,
Dialogue: 0,0:01:33.02,0:01:35.06,Default,,0000,0000,0000,,rigor mortis.
Dialogue: 0,0:01:35.06,0:01:37.58,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:01:37.58,0:01:40.27,Default,,0000,0000,0000,,We need a different way.
Dialogue: 0,0:01:40.27,0:01:42.70,Default,,0000,0000,0000,,The street-fighting way,
Dialogue: 0,0:01:43.86,0:01:46.67,Default,,0000,0000,0000,,which starts with\Na home experiment.
Dialogue: 0,0:01:46.67,0:01:48.98,Default,,0000,0000,0000,,Chair please.
Dialogue: 0,0:01:54.08,0:01:55.80,Default,,0000,0000,0000,,Props please.
Dialogue: 0,0:01:55.80,0:01:58.29,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:02:03.86,0:02:07.47,Default,,0000,0000,0000,,Small cone, big cone. Coffee filters.
Dialogue: 0,0:02:07.47,0:02:09.58,Default,,0000,0000,0000,,They're the same shape,
Dialogue: 0,0:02:09.58,0:02:13.22,Default,,0000,0000,0000,,but this one has\None-fourth the area.
Dialogue: 0,0:02:13.22,0:02:16.25,Default,,0000,0000,0000,,This one has four times\Nthe area, twice the diameter,
Dialogue: 0,0:02:16.25,0:02:18.99,Default,,0000,0000,0000,,but otherwise the same shape.
Dialogue: 0,0:02:18.99,0:02:20.100,Default,,0000,0000,0000,,When I drop them,
Dialogue: 0,0:02:20.100,0:02:24.79,Default,,0000,0000,0000,,how fast do they fall \Nrelative to one another?
Dialogue: 0,0:02:24.79,0:02:31.58,Default,,0000,0000,0000,,Is the big one roughly twice as fast?
Dialogue: 0,0:02:31.58,0:02:34.78,Default,,0000,0000,0000,,Are they comparable in speed?
Dialogue: 0,0:02:34.78,0:02:38.09,Default,,0000,0000,0000,,Or is the small one\Nroughly twice as fast?
Dialogue: 0,0:02:38.09,0:02:42.86,Default,,0000,0000,0000,,Take ten seconds and think.
Dialogue: 0,0:02:42.86,0:02:45.55,Default,,0000,0000,0000,,What do you believe?\NWhat does your gut tell you?
Dialogue: 0,0:02:45.55,0:02:48.28,Default,,0000,0000,0000,,And then we'll take a vote.
Dialogue: 0,0:02:51.29,0:02:53.32,Default,,0000,0000,0000,,Check with your neighbor.
Dialogue: 0,0:02:53.32,0:02:56.09,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:03:00.87,0:03:05.35,Default,,0000,0000,0000,,(Crowd murmuring)
Dialogue: 0,0:03:10.62,0:03:13.22,Default,,0000,0000,0000,,OK, let's take a vote.
Dialogue: 0,0:03:13.22,0:03:15.49,Default,,0000,0000,0000,,You don't have to agree \Nwith your neighbor.
Dialogue: 0,0:03:15.49,0:03:16.85,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:03:16.85,0:03:19.38,Default,,0000,0000,0000,,That's the beauty of democracy.
Dialogue: 0,0:03:20.82,0:03:25.67,Default,,0000,0000,0000,,So, cheer if you believe\Nthat the big cone
Dialogue: 0,0:03:25.67,0:03:29.16,Default,,0000,0000,0000,,will fall roughly twice as fast \Nas the small cone.
Dialogue: 0,0:03:29.16,0:03:30.75,Default,,0000,0000,0000,,(Faint cheering)
Dialogue: 0,0:03:30.75,0:03:32.79,Default,,0000,0000,0000,,OK, I hear a few.
Dialogue: 0,0:03:32.79,0:03:35.84,Default,,0000,0000,0000,,Cheer if you believe \Nthat they'll be roughly comparable.
Dialogue: 0,0:03:35.84,0:03:39.24,Default,,0000,0000,0000,,(Louder cheer)
Dialogue: 0,0:03:39.24,0:03:41.68,Default,,0000,0000,0000,,And cheer if you believe the small cone\N
Dialogue: 0,0:03:41.68,0:03:44.10,Default,,0000,0000,0000,,will be roughly twice as fast.
Dialogue: 0,0:03:44.10,0:03:47.16,Default,,0000,0000,0000,,(Loudest cheer)
Dialogue: 0,0:03:47.16,0:03:49.02,Default,,0000,0000,0000,,A lot of cheering for that one.
Dialogue: 0,0:03:49.02,0:03:53.38,Default,,0000,0000,0000,,OK, well, as Feynman said and believed,
Dialogue: 0,0:03:53.38,0:03:56.76,Default,,0000,0000,0000,,in science we have a\Nsupreme court: experiment.
Dialogue: 0,0:03:56.76,0:03:59.28,Default,,0000,0000,0000,,So, let's do the experiment!
Dialogue: 0,0:04:00.77,0:04:03.56,Default,,0000,0000,0000,,One, two, three.
Dialogue: 0,0:04:05.50,0:04:10.25,Default,,0000,0000,0000,,(Cheering) (Applause)
Dialogue: 0,0:04:13.18,0:04:15.50,Default,,0000,0000,0000,,They're almost the same.
Dialogue: 0,0:04:16.56,0:04:19.45,Default,,0000,0000,0000,,Within experimental error.
Dialogue: 0,0:04:20.29,0:04:21.72,Default,,0000,0000,0000,,So what does that mean?\N
Dialogue: 0,0:04:21.72,0:04:24.46,Default,,0000,0000,0000,,What can we use \Nthat experiment to tell us?
Dialogue: 0,0:04:24.46,0:04:26.32,Default,,0000,0000,0000,,Well,
Dialogue: 0,0:04:27.99,0:04:31.10,Default,,0000,0000,0000,,the cones fell at the same speed.
Dialogue: 0,0:04:31.10,0:04:33.74,Default,,0000,0000,0000,,They fall in the same air.\NIt has the same density.
Dialogue: 0,0:04:33.74,0:04:36.16,Default,,0000,0000,0000,,The same properties.\NThe same viscosity.
Dialogue: 0,0:04:36.16,0:04:38.82,Default,,0000,0000,0000,,The only things different \Nbetween the two cones
Dialogue: 0,0:04:38.82,0:04:40.77,Default,,0000,0000,0000,,is this one has four times the area,
Dialogue: 0,0:04:40.77,0:04:43.33,Default,,0000,0000,0000,,the cross sectional area of this one,
Dialogue: 0,0:04:43.33,0:04:46.06,Default,,0000,0000,0000,,and their drag force is different.\N
Dialogue: 0,0:04:46.06,0:04:47.38,Default,,0000,0000,0000,,How different?
Dialogue: 0,0:04:47.38,0:04:50.49,Default,,0000,0000,0000,,Well, the drag force\Nis equal to the weight.
Dialogue: 0,0:04:50.49,0:04:54.02,Default,,0000,0000,0000,,Because they were falling\Nat a steady speed with no acceleration.
Dialogue: 0,0:04:54.02,0:04:55.92,Default,,0000,0000,0000,,So the drag and the weight cancel.
Dialogue: 0,0:04:55.92,0:04:57.39,Default,,0000,0000,0000,,So we have a very sensitive measure
Dialogue: 0,0:04:57.39,0:05:00.29,Default,,0000,0000,0000,,of the drag force\Nwithout any force sensors.
Dialogue: 0,0:05:00.29,0:05:02.77,Default,,0000,0000,0000,,All we do is measure the weight.
Dialogue: 0,0:05:02.77,0:05:05.37,Default,,0000,0000,0000,,So this one has four times\Nas much paper as this one.
Dialogue: 0,0:05:05.37,0:05:08.68,Default,,0000,0000,0000,,So it's four times heavier,\Nfour times the drag.
Dialogue: 0,0:05:08.68,0:05:11.43,Default,,0000,0000,0000,,Only change, four times the area.
Dialogue: 0,0:05:11.43,0:05:14.92,Default,,0000,0000,0000,,The conclusion:\Ndrag is proportional to area.
Dialogue: 0,0:05:14.92,0:05:17.44,Default,,0000,0000,0000,,Not square root of area,\Nnot the square of the area.
Dialogue: 0,0:05:17.44,0:05:19.01,Default,,0000,0000,0000,,but just the area.
Dialogue: 0,0:05:19.01,0:05:21.29,Default,,0000,0000,0000,,That's the result \Nof our home experiment
Dialogue: 0,0:05:21.29,0:05:25.41,Default,,0000,0000,0000,,without the rigorous \Nrigor mortis method.
Dialogue: 0,0:05:25.41,0:05:26.80,Default,,0000,0000,0000,,How can we use that?
Dialogue: 0,0:05:26.80,0:05:30.19,Default,,0000,0000,0000,,Well, that one constraint,
Dialogue: 0,0:05:30.19,0:05:33.39,Default,,0000,0000,0000,,along with the next street-fighting tool
Dialogue: 0,0:05:33.39,0:05:37.40,Default,,0000,0000,0000,,of dimensional analysis,\Nsolves the drag force.
Dialogue: 0,0:05:37.40,0:05:39.12,Default,,0000,0000,0000,,We match their dimensions.
Dialogue: 0,0:05:39.12,0:05:43.96,Default,,0000,0000,0000,,We match the dimensions of force,\Ndrag force on one side
Dialogue: 0,0:05:43.96,0:05:46.09,Default,,0000,0000,0000,,with what we have on the other,\N
Dialogue: 0,0:05:46.09,0:05:49.47,Default,,0000,0000,0000,,which is area, density, speed \Nand viscosity.
Dialogue: 0,0:05:49.47,0:05:52.61,Default,,0000,0000,0000,,But we already know how to put in\Nthe area, just one of them.
Dialogue: 0,0:05:52.61,0:05:55.96,Default,,0000,0000,0000,,That gives us length squared,\Nmeters squared.
Dialogue: 0,0:05:55.96,0:05:58.90,Default,,0000,0000,0000,,Now we look and we say,\N"Oh, there's kilograms over here,
Dialogue: 0,0:05:58.90,0:06:00.61,Default,,0000,0000,0000,,we have to get a kilogram over here."
Dialogue: 0,0:06:00.61,0:06:02.68,Default,,0000,0000,0000,,The only place to get it from is density.
Dialogue: 0,0:06:02.68,0:06:07.30,Default,,0000,0000,0000,,Speed and viscosity, the kinematic\Nviscosity, have no mass in them.
Dialogue: 0,0:06:07.30,0:06:10.78,Default,,0000,0000,0000,,So we put in one density.
Dialogue: 0,0:06:10.78,0:06:14.79,Default,,0000,0000,0000,,Now what we need still \Nis meter squared / second squared,
Dialogue: 0,0:06:14.79,0:06:16.16,Default,,0000,0000,0000,,out of speed and viscosity.
Dialogue: 0,0:06:16.16,0:06:19.46,Default,,0000,0000,0000,,The only way to make it is speed squared.
Dialogue: 0,0:06:20.79,0:06:23.23,Default,,0000,0000,0000,,So there is our drag force.
Dialogue: 0,0:06:23.23,0:06:25.07,Default,,0000,0000,0000,,One experiment for a constraint.
Dialogue: 0,0:06:25.07,0:06:27.61,Default,,0000,0000,0000,,Dimensional analysis\Nfor the rest of the constraints.
Dialogue: 0,0:06:27.61,0:06:31.99,Default,,0000,0000,0000,,Drag Force =\NArea x Density x Speed squared.
Dialogue: 0,0:06:31.99,0:06:34.20,Default,,0000,0000,0000,,How can we use this?
Dialogue: 0,0:06:34.20,0:06:37.41,Default,,0000,0000,0000,,Well, the fuel consumption \Nis proportional to the drag force.
Dialogue: 0,0:06:37.41,0:06:41.62,Default,,0000,0000,0000,,So, let's compare the fuel consumption\Nof a plane with a car.
Dialogue: 0,0:06:41.62,0:06:45.49,Default,,0000,0000,0000,,Rather than calculating the plane\Nfrom scratch, compare it to a car.
Dialogue: 0,0:06:45.49,0:06:48.90,Default,,0000,0000,0000,,Another street-fighting technique.
Dialogue: 0,0:06:48.90,0:06:52.15,Default,,0000,0000,0000,,So there're three factors in\Nthe comparison, in the ratio:
Dialogue: 0,0:06:52.15,0:06:57.67,Default,,0000,0000,0000,,the area, the air density\Nand the speed squared.
Dialogue: 0,0:06:57.67,0:06:59.56,Default,,0000,0000,0000,,Do them one at a time.
Dialogue: 0,0:06:59.56,0:07:03.33,Default,,0000,0000,0000,,So, the area. Well, \Nin the old days of plane travel,
Dialogue: 0,0:07:03.33,0:07:05.39,Default,,0000,0000,0000,,you could lie down on three seats
Dialogue: 0,0:07:05.39,0:07:07.11,Default,,0000,0000,0000,,and there were three sets of those seats.
Dialogue: 0,0:07:07.11,0:07:10.19,Default,,0000,0000,0000,,So three people wide.\NPlane is about three people high.
Dialogue: 0,0:07:10.19,0:07:12.72,Default,,0000,0000,0000,,So it's nine square people.
Dialogue: 0,0:07:12.72,0:07:17.03,Default,,0000,0000,0000,,A car: Well, \Nfrom nocturnal activities in cars
Dialogue: 0,0:07:17.03,0:07:20.34,Default,,0000,0000,0000,,you know you can sort of lie down\Nin cars a bit uncomfortably.
Dialogue: 0,0:07:20.34,0:07:21.52,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:07:21.52,0:07:24.06,Default,,0000,0000,0000,,And you can stand up.\NSo it's one square person.
Dialogue: 0,0:07:24.06,0:07:26.02,Default,,0000,0000,0000,,So it's roughly a ratio of ten,
Dialogue: 0,0:07:26.02,0:07:27.36,Default,,0000,0000,0000,,maybe nine or ten.
Dialogue: 0,0:07:27.36,0:07:30.73,Default,,0000,0000,0000,,So the plane is 10 times\Nless fuel efficient for that.
Dialogue: 0,0:07:30.73,0:07:32.18,Default,,0000,0000,0000,,What about air density?
Dialogue: 0,0:07:32.18,0:07:34.39,Default,,0000,0000,0000,,Well, the planes fly high, \Nabout Mt. Everest.
Dialogue: 0,0:07:34.39,0:07:36.00,Default,,0000,0000,0000,,So the density is about one third.
Dialogue: 0,0:07:36.00,0:07:38.15,Default,,0000,0000,0000,,So that helps the plane.
Dialogue: 0,0:07:38.15,0:07:40.23,Default,,0000,0000,0000,,But they fly about ten times faster,\N
Dialogue: 0,0:07:40.23,0:07:42.52,Default,,0000,0000,0000,,600 miles an hour versus 60.
Dialogue: 0,0:07:42.52,0:07:48.12,Default,,0000,0000,0000,,That means planes pay a factor \Nof a hundred, 10 squared.
Dialogue: 0,0:07:48.12,0:07:51.27,Default,,0000,0000,0000,,The result is planes are 300 times\N
Dialogue: 0,0:07:51.27,0:07:53.73,Default,,0000,0000,0000,,less fuel efficient than cars.
Dialogue: 0,0:07:53.73,0:07:57.57,Default,,0000,0000,0000,,Oh, no. By flying here, \Ndid I damage the environment
Dialogue: 0,0:07:57.57,0:08:00.12,Default,,0000,0000,0000,,300 times compared to driving? \N(Gasp)
Dialogue: 0,0:08:00.12,0:08:02.11,Default,,0000,0000,0000,,What saves it?
Dialogue: 0,0:08:02.11,0:08:04.79,Default,,0000,0000,0000,,300 people on my plane!
Dialogue: 0,0:08:04.79,0:08:07.18,Default,,0000,0000,0000,,So the conclusion is planes and cars
Dialogue: 0,0:08:07.18,0:08:09.33,Default,,0000,0000,0000,,are roughly equally fuel efficient.
Dialogue: 0,0:08:09.33,0:08:11.05,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:08:11.05,0:08:12.51,Default,,0000,0000,0000,,All from that.
Dialogue: 0,0:08:12.51,0:08:17.05,Default,,0000,0000,0000,,(Applause)
Dialogue: 0,0:08:20.86,0:08:24.43,Default,,0000,0000,0000,,So let's say the plane is \N30 miles per gallon.
Dialogue: 0,0:08:24.43,0:08:28.52,Default,,0000,0000,0000,,Crossing the country\Nback and forth 6,000 miles,
Dialogue: 0,0:08:28.52,0:08:30.90,Default,,0000,0000,0000,,30 miles per gallon, 2 dollars a gallon.\N
Dialogue: 0,0:08:30.90,0:08:33.25,Default,,0000,0000,0000,,That's 400 dollars of gasoline.
Dialogue: 0,0:08:33.25,0:08:36.37,Default,,0000,0000,0000,,That's not that different than\Nthe price of my plane ticket,
Dialogue: 0,0:08:36.37,0:08:40.66,Default,,0000,0000,0000,,which may explain why \Nairline companies teeter on bankruptcy
Dialogue: 0,0:08:40.66,0:08:42.58,Default,,0000,0000,0000,,and why they charge us for peanuts.
Dialogue: 0,0:08:42.58,0:08:45.23,Default,,0000,0000,0000,,(Laughter)
Dialogue: 0,0:08:45.23,0:08:52.44,Default,,0000,0000,0000,,So connection between\Nthe 747 and the cones.
Dialogue: 0,0:08:52.44,0:08:55.38,Default,,0000,0000,0000,,They increase our enjoyment of the world\N
Dialogue: 0,0:08:55.38,0:08:58.27,Default,,0000,0000,0000,,and expand our perception.
Dialogue: 0,0:08:58.78,0:09:01.24,Default,,0000,0000,0000,,And that, making connections here \N
Dialogue: 0,0:09:01.24,0:09:03.15,Default,,0000,0000,0000,,was enabled by street-fighting reasoning,
Dialogue: 0,0:09:03.15,0:09:06.87,Default,,0000,0000,0000,,by getting away from rigor mortis.
Dialogue: 0,0:09:06.87,0:09:08.75,Default,,0000,0000,0000,,Making connections is so important\N
Dialogue: 0,0:09:08.75,0:09:11.80,Default,,0000,0000,0000,,because it builds ideas and isolated facts\N
Dialogue: 0,0:09:11.80,0:09:14.10,Default,,0000,0000,0000,,into a coherent story.
Dialogue: 0,0:09:14.10,0:09:16.07,Default,,0000,0000,0000,,Imagine each dot is an idea
Dialogue: 0,0:09:16.07,0:09:19.05,Default,,0000,0000,0000,,and the lines are the connections \Nbetween them.
Dialogue: 0,0:09:19.05,0:09:21.23,Default,,0000,0000,0000,,As I increase the fraction of connections\N
Dialogue: 0,0:09:21.23,0:09:24.57,Default,,0000,0000,0000,,from 40% to 50%, to 60%,
Dialogue: 0,0:09:24.57,0:09:27.43,Default,,0000,0000,0000,,the big story, the red connection network,\N
Dialogue: 0,0:09:27.43,0:09:29.19,Default,,0000,0000,0000,,grows to fill the whole space.
Dialogue: 0,0:09:29.19,0:09:31.09,Default,,0000,0000,0000,,That's the long lasting learning.
Dialogue: 0,0:09:31.09,0:09:33.14,Default,,0000,0000,0000,,That's what we want \Nto build in our thinking
Dialogue: 0,0:09:33.14,0:09:35.08,Default,,0000,0000,0000,,and in our teaching.
Dialogue: 0,0:09:35.98,0:09:38.43,Default,,0000,0000,0000,,The goal of teaching should be
Dialogue: 0,0:09:38.43,0:09:42.26,Default,,0000,0000,0000,,to implant a way of thinking\Nthat enables a student
Dialogue: 0,0:09:42.26,0:09:45.93,Default,,0000,0000,0000,,to learn in one year\Nwhat the teacher learned in two years.
Dialogue: 0,0:09:45.93,0:09:48.32,Default,,0000,0000,0000,,Only in that way \Ncan we continue to advance
Dialogue: 0,0:09:48.32,0:09:51.31,Default,,0000,0000,0000,,from one generation to the next.
Dialogue: 0,0:09:51.31,0:09:55.04,Default,,0000,0000,0000,,In fifty years, all education
Dialogue: 0,0:09:55.04,0:09:58.25,Default,,0000,0000,0000,,will, I believe and dream,\Nbe based on this principle.
Dialogue: 0,0:09:58.26,0:10:02.28,Default,,0000,0000,0000,,Richard Feynman, I think,\Nwould have agreed.
Dialogue: 0,0:10:02.28,0:10:03.66,Default,,0000,0000,0000,,Thank you.
Dialogue: 0,0:10:03.66,0:10:08.52,Default,,0000,0000,0000,,(Applause)