In the Beginning was Information

R6: One can employ a known natural law to discover anotherone: It has happened time and again in the history of science that anew law has been discovered using the validity of a known law. Ifthe law of gravity had not been known, then the behaviour of themoons of Jupiter could not have been investigated properly. Observationsof their motions made it possible to compute the speed oflight, which is an important physical constant.The orbits of the planets cannot be exactly elliptical (as would berequired if the gravitational pull of the sun was the only force actingon them), as required by Newton’s law, since they are not onlyunder the gravitational influence of the sun, but they also affectone another gravitationally to a lesser extent. John Couch Adams(1819 – 1892), a British astronomer and mathematician, computedthe expected perturbations caused by their mutual gravitationalattractions, of the orbits of the then known major planets, Jupiter,Saturn, and Uranus. The French astronomer Urban J. J. Leverrier(1811 – 1877) also computed the deviations of these orbits fromthe perfect Kepler ellipses independently. It was found that Jupiterand Saturn “lived up to the expectations”, but Uranus exhibiteddeviant behaviour.Relying on the validity of Newton’s law, both astronomers wereable to deduce the position of a hitherto unknown planet fromthese irregularities. Each of them then approached an observatorywith the request to look for an unknown planet in such and sucha celestial position. This request was not taken seriously at oneobservatory; they regarded it as absurd that a pencil-pushercould tell them where to look for a new planet. The other observatoryresponded promptly, and they discovered Neptune. Leverrierwrote to the German astronomer Johann Gottfried Galle(1812 – 1910), who then discovered Neptune very close to thepredicted position.2.5 The Classification of the Laws of NatureWhen one considers the laws of nature according to the ways theyare expressed, one discovers striking general principles which theyseem to obey. The laws can accordingly be classified as follows:36