[00:00.49]Beyond two or three days, the world's best weather forecasts are speculative, and beyond six or seven they are worthless.
[00:10.31]The Butterfly Effect is the reason.
[00:12.85]For small pieces of weather -- and to a global forecaster, small can mean thunderstorms and blizzards -- any prediction deteriorates rapidly.
[00:24.05]Errors and uncertainties multiply, cascading upward through a chain of turbulent features, from dust devils and squalls up to continent-size eddies that only satellites can see.
[00:37.46]The modern weather models work with a grid of points of the order of sixty miles apart,
[00:43.58]and even so, some starting data has to guessed, since ground stations and satellites cannot see everywhere.
[00:52.44]But suppose the earth could be covered with sensors spaced one foot apart, rising at one-foot intervals all the way to the top of the atmosphere.
[01:02.98]Suppose every sensor gives perfectly accurate readings of temperature, pressure, humidity, and any other quantity a meteorologist would want.
[01:14.12]Precisely at noon an infinitely powerful computer takes all the data and calculates what will happen at each point at 12.01, then 1202, then 12.03...
[01:28.37]The computer will still be unable to predict whether Princeton, New Jersey, will have sun or rain on a day one month away.
[01:37.11]At noon the spaces between the sensors will hide fluctuations that the computer will not know about, tiny deviations from the average.
[01:46.82]By 12.01, those fluctuations will already have created small errors one foot away.
[01:54.08]Soon the errors will have multiplied to the ten-foot scale, and so on up to the size of the globe.
