Be very, very careful what you put into that head, because you will never, ever get it out.
--Thomas Wolsey, 1471-1530
That quote was the inspiration for a talk by Jonathan Drori at TED University on the topic of Why We Don’t Understand as Much as We Think We Do. For the second consecutive year at TED, the conference was preceded by a series of twelve-minute "courses" on everything from How to Fly a Helicopter Indoors to Making the Most of Web 2.0.
In his talk, Drori offered some examples of problems where intuition leads most people astray:
- When a seed grows into a tree, where does most of the material come from? (Wrong answer: the soil.)
- How do you make an electrical circuit with only a battery, a light bulb, and one piece of wire? (He showed a video of recent MIT Electrical Engineering graduates who couldn't figure this out.)
- Why is Winter colder than Summer? (Wrong answer: because the earth is further away from the sun in Winter.)
- Draw a diagram showing the shape of the orbits of the planets. (Wrong answer: they are ellipses.)
When I tried these same questions on most people, they got the answers wrong, but in defense of MIT, all three people I know who went there got all three answers correct. Perhaps being out in the real world for a few years gave them the practical experience to apply their theoretical knowledge, or maybe I've just hired people who fooled around with electricity before they embarked on an education filled with more math than hands-on experience.
The correct answers:
- The mass of the tree comes from the air. If you recall photosynthesis from high-school biology, the energy from the sun enables the chlorophyll in the leaves to separate the carbon and the oxygen from the carbon dioxide in the air. The Carbon is combined with the much lighter hydrogen in the water to form hydrocarbons which are the basis of all organic materials, including wood.
- To light the bulb, touch one end of the wire to one end of the battery. Wrap the other end around the threads of the bulb. Then touch the other contact at the end of the bulb directly to the other contact at the end of the battery.
- The seasons are caused by the angle of the earth. The rays in the Summer hemisphere strike more directly than the rays in the Winter hemisphere.
- The orbits are pretty much circular. People often draw ellipses for two reasons: 1. They have seen all those illustrations in books that try to look three-dimensional by projecting the circular orbits on a plane not parallel to those orbits; and 2. they think that the Earth must be further from the Sun in the Winter, not thinking about how it's Summer in the other hemisphere at the same time.
At the end of the class, Drori handed out a small plastic toy which I later learned is called a Rattleback
or Rebellious Celt. If you spin it counterclockwise, it rotates well enough, but if you spin it clockwise, it turns a few times before it starts to rock back and forth and then, astonishingly, start to spin in the other direction. You can see a video here. The physics have intrigued scientists for at least a century until Hermann Bondi published a The Rigid Body Dynamics of Unidirectional Spin in 1986. Jeremy Webb attempts to explain it here, but you can't really understand it without doing the math.
