The Perimeter of Ignorance
A boundary where scientists face a choice: invoke a deity or continue the quest for knowledge
by Neil deGrasse Tyson
From Natural History magazine — November 2005
Writing 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 revolved 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 ph¾nomena." 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."
* * *
Laplace notwithstanding, plenty of scientists besides Newton have called on
God-or the gods-wherever their comprehension fades to ignorance. Consider the
second-century a.d. Alexandrian astronomer Ptolemy. Armed with a description,
but no real understanding, of what the planets were doing up there, he could not
contain his religious fervor:
I know that I am mortal by nature, and ephemeral; but when I trace, at my
pleasure, the windings to and fro of the heavenly bodies, I no longer touch
Earth with my feet: I stand in the presence of Zeus himself and take my fill of
ambrosia.
Or consider the seventeenth-century Dutch astronomer Christiaan Huygens, whose
achievements include constructing the first working pendulum clock and
discovering the rings of Saturn. In his charming book The Celestial Worlds
Discover'd, posthumously published in 1696, most of the opening chapter
celebrates all that was then known of planetary orbits, shapes, and sizes, as
well as the planets' relative brightness and presumed rockiness. The book even
includes foldout charts illustrating the structure of the solar system. God is
absent from this discussion-even though a mere century earlier, before Newton's
achievements, planetary orbits were supreme mysteries.
Celestial Worlds also brims with speculations about life in the solar system,
and that's where Huygens raises questions to which he has no answer. That's
where he mentions the biological conundrums of the day, such as the origin of
life's complexity. And sure enough, because seventeenth-century physics was more
advanced than seventeenth-century biology, Huygens invokes the hand of God only
when he talks about biology:
I suppose no body will deny but that there's somewhat more of Contrivance,
somewhat more of Miracle in the production and growth of Plants and Animals than
in lifeless heaps of inanimate Bodies. . . . For the finger of God, and the
Wisdom of Divine Providence, is in them much more clearly manifested than in the
other.
Today secular philosophers call that kind of divine invocation "God of the gaps"-which
comes in handy, because there has never been a shortage of gaps in people's
knowledge.
* * *
As reverent as Newton, Huygens, and other great scientists of earlier centuries
may have been, they were also empiricists. They did not retreat from the
conclusions their evidence forced them to draw, and when their discoveries
conflicted with prevailing articles of faith, they upheld the discoveries. That
doesn't mean it was easy: sometimes they met fierce opposition, as did Galileo,
who had to defend his telescopic evidence against formidable objections drawn
from both scripture and "common" sense.
Galileo clearly distinguished the role of religion from the role of science. To
him, religion was the service of God and the salvation of souls, whereas science
was the source of exact observations and demonstrated truths. In a long, famous,
bristly letter written in the summer of 1615 to the Grand Duchess Christina of
Tuscany (but, like so many epistles of the day, circulated among the literati),
he quotes, in his own defense, an unnamed yet sympathetic church official saying
that the Bible "tells you how to go to heaven, not how the heavens go."
The letter to the duchess leaves no doubt about where Galileo stood on the
literal word of the Holy Writ:
In expounding the Bible if one were always to confine oneself to the unadorned
grammatical meaning, one might fall into error. . . .
Nothing physical which . . . demonstrations prove to us, ought to be called in
question (much less condemned) upon the testimony of biblical passages which may
have some different meaning beneath their words. . . .
I do not feel obliged to believe that the same God who has endowed us with
senses, reason and intellect has intended us to forgo their use.
A rare exception among scientists, Galileo saw the unknown as a place to explore
rather than as an eternal mystery controlled by the hand of God.
As long as the celestial sphere was generally regarded as the domain of the
divine, the fact that mere mortals could not explain its workings could safely
be cited as proof of the higher wisdom and power of God. But beginning in the
sixteenth century, the work of Copernicus, Kepler, Galileo, and Newton-not to
mention Maxwell, Heisenberg, Einstein, and everybody else who discovered
fundamental laws of physics-provided rational explanations for an increasing
range of phenomena. Little by little, the universe was subjected to the methods
and tools of science, and became a demonstrably knowable place.
* * *
Then, in what amounts to a stunning yet unheralded philosophical inversion,
throngs of ecclesiastics and scholars began to declare that it was the laws of
physics themselves that served as proof of the wisdom and power of God.
One popular theme of the seventeenth and eighteenth centuries was the "clockwork
universe"-an ordered, rational, predictable mechanism fashioned and run by God
and his physical laws. The early telescopes, which all relied on visible light,
did little to undercut that image of an ordered system. The Moon revolved around
Earth. Earth and other planets rotated on their axes and revolved around the
Sun. The stars shone. The nebulae floated freely in space.
Not until the nineteenth century was it evident that visible light is just one
band of a broad spectrum of electromagnetic radiation-the band that human beings
just happen to see. Infrared was discovered in 1800, ultraviolet in 1801, radio
waves in 1888, X rays in 1895, and gamma rays in 1900. Decade by decade in the
following century, new kinds of telescopes came into use, fitted with detectors
that could "see" these formerly invisible parts of the electromagnetic spectrum.
Now astrophysicists began to unmask the true character of the universe.
Turns out that some celestial bodies give off more light in the invisible bands
of the spectrum than in the visible. And the invisible light picked up by the
new telescopes showed that mayhem abounds in the cosmos: monstrous gamma-ray
bursts, deadly pulsars, matter-crushing gravitational fields, matter-hungry
black holes that flay their bloated stellar neighbors, newborn stars igniting
within pockets of collapsing gas. And as our ordinary, optical telescopes got
bigger and better, more mayhem emerged: galaxies that collide and cannibalize
each other, explosions of supermassive stars, chaotic stellar and planetary
orbits. Our own cosmic neighborhood-the inner solar system-turned out to be a
shooting gallery, full of rogue asteroids and comets that collide with planets
from time to time. Occasionally they've even wiped out stupendous masses of
Earth's flora and fauna. The evidence all points to the fact that we occupy not
a well-mannered clockwork universe, but a destructive, violent, and hostile zoo.
Of course, Earth can be bad for your health too. On land, grizzly bears want to
maul you; in the oceans, sharks want to eat you. Snowdrifts can freeze you,
deserts dehydrate you, earthquakes bury you, volcanoes incinerate you. Viruses
can infect you, parasites suck your vital fluids, cancers take over your body,
congenital diseases force an early death. And even if you have the good luck to
be healthy, a swarm of locusts could devour your crops, a tsunami could wash
away your family, or a hurricane could blow apart your town.
* * *
So the universe wants to kill us all. But let's ignore that complication for the
moment.
Many, perhaps countless, questions hover at the front lines of science. In some
cases, answers have eluded the best minds of our species for decades or even
centuries. And in contemporary America, the notion that a higher intelligence is
the single answer to all enigmas has been enjoying a resurgence. This
present-day version of God of the gaps goes by a fresh name: "intelligent
design." The term suggests that some entity, endowed with a mental capacity far
greater than the human mind can muster, created or enabled all the things in the
physical world that we cannot explain through scientific methods.
An interesting hypothesis.
But why confine ourselves to things too wondrous or intricate for us to
understand, whose existence and attributes we then credit to a superintelligence?
Instead, why not tally all those things whose design is so clunky, goofy,
impractical, or unworkable that they reflect the absence of intelligence?
Take the human form. We eat, drink, and breathe through the same hole in the
head, and so, despite Henry J. Heimlich's eponymous maneuver, choking is the
fourth leading cause of "unintentional injury death" in the United States. How
about drowning, the fifth leading cause? Water covers almost three-quarters of
Earth's surface, yet we are land creatures-submerge your head for just a few
minutes, and you die.
Or take our collection of useless body parts. What good is the pinky toenail?
How about the appendix, which stops functioning after childhood and thereafter
serves only as the source of appendicitis? Useful parts, too, can be
problematic. I happen to like my knees, but nobody ever accused them of being
well protected from bumps and bangs. These days, people with problem knees can
get them surgically replaced. As for our pain-prone spine, it may be a while
before someone finds a way to swap that out.
How about the silent killers? High blood pressure, colon cancer, and diabetes
each cause tens of thousands of deaths in the U.S. every year, but it's possible
not to know you're afflicted until your coroner tells you so. Wouldn't it be
nice if we had built-in biogauges to warn us of such dangers well in advance?
Even cheap cars, after all, have engine gauges.
And what comedian designer configured the region between our legs-an
entertainment complex built around a sewage system?
The eye is often held up as a marvel of biological engineering. To the
astrophysicist, though, it's only a so-so detector. A better one would be much
more sensitive to dark things in the sky and to all the invisible parts of the
spectrum. How much more breathtaking sunsets would be if we could see
ultraviolet and infrared. How useful it would be if, at a glance, we could see
every source of microwaves in the environment, or know which radio station
transmitters were active. How helpful it would be if we could spot police radar
detectors at night.
Think how easy it would be to navigate an unfamiliar city if we, like birds,
could always tell which way was north because of the magnetite in our heads.
Think how much better off we'd be if we had gills as well as lungs, how much
more productive if we had six arms instead of two. And if we had eight, we could
safely drive a car while simultaneously talking on a cell phone, changing the
radio station, applying makeup, sipping a drink, and scratching our left ear.
Stupid design could fuel a movement unto itself. It may not be nature's default,
but it's ubiquitous. Yet people seem to enjoy thinking that our bodies, our
minds, and even our universe represent pinnacles of form and reason. Maybe it's
a good antidepressant to think so. But it's not science-not now, not in the
past, not ever.
* * *
Another practice that isn't science is embracing ignorance. Yet it's fundamental
to the philosophy of intelligent design: I don't know what this is. I don't know
how it works. It's too complicated for me to figure out. It's too complicated
for any human being to figure out. So it must be the product of a higher
intelligence.
What do you do with that line of reasoning? Do you just cede the solving of
problems to someone smarter than you, someone who's not even human? Do you tell
students to pursue only questions with easy answers?
There may be a limit to what the human mind can figure out about our universe.
But how presumptuous it would be for me to claim that if I can't solve a
problem, neither can any other person who has ever lived or who will ever be
born. Suppose Galileo and Laplace had felt that way? Better yet, what if Newton
had not? He might then have solved Laplace's problem a century earlier, making
it possible for Laplace to cross the next frontier of ignorance.
Science is a philosophy of discovery. Intelligent design is a philosophy of
ignorance. You cannot build a program of discovery on the assumption that nobody
is smart enough to figure out the answer to a problem. Once upon a time, people
identified the god Neptune as the source of storms at sea. Today we call these
storms hurricanes. We know when and where they start. We know what drives them.
We know what mitigates their destructive power. And anyone who has studied
global warming can tell you what makes them worse. The only people who still
call hurricanes "acts of God" are the people who write insurance forms.
* * *
To deny or erase the rich, colorful history of scientists and other thinkers who
have invoked divinity in their work would be intellectually dishonest. Surely
there's an appropriate place for intelligent design to live in the academic
landscape. How about the history of religion? How about philosophy or
psychology? The one place it doesn't belong is the science classroom.
If you're not swayed by academic arguments, consider the financial consequences.
Allow intelligent design into science textbooks, lecture halls, and
laboratories, and the cost to the frontier of scientific discovery-the frontier
that drives the economies of the future-would be incalculable. I don't want
students who could make the next major breakthrough in renewable energy sources
or space travel to have been taught that anything they don't understand, and
that nobody yet understands, is divinely constructed and therefore beyond their
intellectual capacity. The day that happens, Americans will just sit in awe of
what we don't understand, while we watch the rest of the world boldly go where
no mortal has gone before.
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.
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