November 2005



Darwin & Evolution
Image by Jac Depczyk, jacdepczyk.com; netcells.net

The Illusion of Design Darwin’s Shrink Evolution in Action The Origins of Form Universe


Universe:  The Perimeter of Ignorance

A boundary where scientists face a choice:
invoke a deity or continue the quest for knowledge


riting in centuries past, many scientists felt compelled to wax poetic about cosmic mysteries and God’s handiwork. Perhaps one should not be surprised at this: most scientists back then, as well as many scientists today, identify themselves as spiritually devout.

But a careful reading of older texts, particularly those concerned with the universe itself, shows that the authors invoke divinity only when they reach the boundaries of their understanding. They appeal to a higher power only when staring into the ocean of their own ignorance. They call on God only from the lonely and precarious edge of incomprehension. Where they feel certain about their explanations, however, God gets hardly a mention.

Let’s start at the top. Isaac Newton was one of the greatest intellects the world has ever seen. His laws of motion and his universal law of gravitation, conceived in the mid-seventeenth century, account for cosmic phenomena that had eluded philosophers for millennia. Through those laws, one could understand the gravitational attraction of bodies in a system, and thus come to understand orbits.

Newton’s law of gravity enables you to calculate the force of attraction between any two objects. If you introduce a third object, then each one attracts the other two, and the orbits they trace become much harder to compute. Add another object, and another, and another, and soon you have the planets in our solar system. Earth and the Sun pull on each other, but Jupiter also pulls on Earth, Saturn pulls on Earth, Mars pulls on Earth, Jupiter pulls on Saturn, Saturn pulls on Mars, and on and on.

Newton feared that all this pulling would render the orbits in the solar system unstable. His equations indicated that the planets should long ago have either fallen into the Sun or flown the coop—leaving the Sun, in either case, devoid of planets. Yet the solar system, as well as the larger cosmos, appeared to be the very model of order and durability. So Newton, in his greatest work, the Principia, concludes that God must occasionally step in and make things right:

The six primary Planets are revolv’d about the Sun, in circles concentric with the Sun, and with motions directed towards the same parts, and almost in the same plane. . . . But it is not to be conceived that mere mechanical causes could give birth to so many regular motions. . . . This most beautiful System of the Sun, Planets, and Comets, could only proceed from the counsel and dominion of an intelligent and powerful Being.

In the Principia, Newton distinguishes between hypotheses and experimental philosophy, and declares, “Hypotheses, whether metaphysical or physical, whether of occult qualities or mechanical, have no place in experimental philosophy.” What he wants is data, “inferr’d from the phænomena.” But in the absence of data, at the border between what he could explain and what he could only honor—the causes he could identify and those he could not—Newton rapturously invokes God:

Eternal and Infinite, Omnipotent and Omniscient; . . . he governs all things, and knows all things that are or can be done. . . . We know him only by his most wise and excellent contrivances of things, and final causes; we admire him for his perfections; but we reverence and adore him on account of his dominion.

A century later, the French astronomer and mathematician Pierre-Simon de Laplace confronted Newton’s dilemma of unstable orbits head-on. Rather than view the mysterious stability of the solar system as the unknowable work of God, Laplace declared it a scientific challenge. In his multipart masterpiece, Mécanique Céleste, the first volume of which appeared in 1798, Laplace demonstrates that the solar system is stable over periods of time longer than Newton could predict. To do so, Laplace pioneered a new kind of mathematics called perturbation theory, which enabled him to examine the cumulative effects of many small forces. According to an oft-repeated but probably embellished account, when Laplace gave a copy of Mécanique Céleste to his physics-literate friend Napoleon Bonaparte, Napoleon asked him what role God played in the construction and regulation of the heavens. “Sire,” Laplace replied, “I have no need of that hypothesis.”

To read the rest of Neil deGrasse Tyson’s column for November, see the print issue of Natural History.

 Order this special issue. 

Neil deGrasse Tyson



Astrophysicist Neil deGrasse Tyson is the director of the Hayden Planetarium at the American Museum of Natural History. An anthology of his “Universe” columns will be published in 2006 by W.W. Norton.


The Illusion of Design Darwin’s Shrink Evolution in Action The Origins of Form Universe


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