The Universe In a Nut Shell by Stephen Hawking

Author:Stephen Hawking [Hawking, Stephen]
Language: eng
Format: epub
Published: 2011-05-30T22:29:20+00:00

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(FIG. 4 . 2 )

than there is for astrology, but we believe them because they are If you know where and at what speed

consistent with theories that have survived testing.

a baseball is thrown, you can predict

T h e success of Newton's laws and other physical theories led to where it will go.

the idea of scientific determinism, which was first expressed at the beginning of the nineteenth century by the French scientist the Marquis de Laplace. Laplace suggested that if we knew the positions and velocities of all the particles in the universe at one time, the laws of physics should allow us to predict what the state of the universe would be at any other time in the past or in the future (Fig. 4.2).

In other words, if scientific determinism holds, we should in principle be able to predict the future and wouldn't need astrology.

Of course, in practice even something as simple as Newton's theory of gravity produces equations that we can't solve exactly for more than two particles. Furthermore, the equations often have a property known as chaos, so that a small change in position or velocity at one time can lead to completely different behavior at later times. As those w h o have seen Jurassic Park know, a tiny disturbance in one place can cause a major change in another. A butterfly flapping its wings in T o k y o can cause rain in New York's Central Park (Fig. 4 . 3 ) .

T h e trouble is the sequence of events is not repeatable. T h e next time (FIG. 4 . 3 )

the butterfly flaps its wings, a host of other factors will be different 104

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