MOTION MOUNTAIN

312 9 concepts, lies and patterns of nature
Challenge 319 s
Challenge 320 s
vation with them.This endeavour is called theunification of physics – by those who like
it; those who don’t like it, call it ‘reductionism’. For example, the same rule describes
the flight of a tennis ball, the motion of the tides at the sea shore, the timing of ice ages,
and the time at which the planet Venus ceases to be the evening star and starts to be the
morning star.These processes are all consequences of universal gravitation. Similarly, it
is not evident that the same rule describes the origin of the colour of the eyes, the formation
of lightning, the digestion of food and the working of the brain. These processes
aredescribedbyquantum electrodynamics.
Unification has its most impressive successes when it predicts an observation that
has not been made before. A famous example is the existence of antimatter, predicted
by Dirac when he investigated the solutions of an equation that describes the precise
behaviour of common matter.
The second procedure in the search for explanations is to eliminate all otherimaginablealternatives
in favour of the actually correct one.This endeavour has no commonly
accepted name: it could be called thedemarcation of the ‘laws’ of physics – by those who
like it; others call it ‘anthropocentrism’, or simply ‘arrogance’.
When we discover that light travels in such a way that it takes the shortest possible
time to its destination, when we describe motion by a principle of least action, or when
we discover that trees are branched in such a way that they achieve the largest effect with
the smallest effort, we are using a demarcation viewpoint.
In summary, unification, answering ‘why’ questions, and demarcation, answering
‘why not’ questions, are typical for the progress throughout the history of physics. We
can say that the dual aspects of unification and demarcation form the composing and
the opposing traits of physics.They stand for the desire toknoweverything.
However, neither demarcation nor unification can explain the universe as a whole.
Can you see why? In fact, apart from unification and demarcation, there is a third possibilitythatmergesthetwoandallowsonetosaymoreabouttheuniverse.
Can you find
it? Our walk will automatically lead to it later.
Pigs, apes and the anthropic principle
“Daswichtigste Hilfsmittel desWissenschaftlers
istderPapierkorb.*
The wish to achieve demarcation of the patterns of nature is most interesting
Severalauthors”
when we
follow the consequences of different rules of nature until we find them in contradiction
with the most striking observation: our own human existence. In this special case the
program of demarcation is often called theanthropicprinciple – from the Greek ἄνθρωπος,meaning
‘man’.
For example, if the Sun–Earth distance were different from what it is, the resulting
temperature change on the Earth would have made impossible the appearance of life,
which needs liquid water. Similarly, our brain would not work if the Moon did not circle
the Earth. It is also well-known that if there were fewer large planets in the solar system,theevolution
of humans would have been impossible.The large planets divert large
* ‘Themostimportant instrument ofascientististhewastepaper basket.’
Motion Mountain – The Adventure of Physics copyright © Christoph Schiller June 1990–November 2015 free pdf file available at www.motionmountain.net