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When was the 'aha moment' of the movement of continents?

In the third century B.C., King Hiero allegedly asked Archimedes to ascertain whether an unscrupulous jeweler had made his crown of pure gold or some less valuable alloy. Archimedes was not to damage the crown in any way. Baffled by this seemingly intractable problem, Archimedes had a flash of insight when the water overflowed as he stepped into his bath: he dashed naked through the streets of Syracuse crying, “Eureka! I have the solution!”

Mrs. Archimedes probably had a simpler solution — “Put less water in the tub!” — but as a youngster I was told this story as an example of the way great discoveries are made. Aristotle, who died more than 35 years before Archimedes was born, believed that great discoveries are made only by exhaustive study of natural phenomena.

Although some major discoveries may have resulted from revelatory moments like Archimedes’, I suspect that even when an “aha moment“ does occur, it may be the culmination of years of study. Isaac Newton said, “If I have seen farther than those before me, it is because I stood on the shoulders of giants.” Thomas Edison described discovery as, “one percent inspiration and 99 percent perspiration.”

Consider two extraordinary concepts about the movement of continents that are widely accepted today but were considered little more than wild-eyed speculation just 50 years ago. These two concepts, that the continents of the earth’s crust have bobbed up and down like wood chips floating in water (“isostasy,”) and have moved about relative to one another (“continental drift”) seem to challenge common sense. Yet both ideas were suggested in the sixteenth century and almost 400 years elapsed before either gained wide acceptance.

For example, movement of the continents was suggested by Abraham Ortelius, a Dutch mapmaker in 1596. He observed that the Atlantic coastlines of South America and Africa were so strikingly complementary that one could only conclude the two continents were once conjoined. In the years that followed, observations by oceanographers, botanists, paleontologists, geologists, meteorologists and others appeared to support Ortelius’ suggestion. But physical scientists and engineers dismissed continental movement for want of a mechanism to drive the continents as they “plowed across the earth’s surface like a ship through water.”

In the mid-1960s, several geologists working independently examined the problem from a slightly different point of view. Instead of searching for a driving force to move the continents, they suggested that continents were simply drifting on a moving current within the earth, like blocks of ice floating down a river. With this change of view, all of the accumulated data came together. The earth sciences underwent a fundamental transformation.

Was this a scientific epiphany? If so, when was the “aha moment?" Was it 1596 when Ortelius noticed the congruent shapes of African and South American coastlines? Was it in 1960s when several geologists suggested that continents were "flotsam" drifting on a mobile mantle? Or was there no epiphany, the discovery being simply the culmination of work by scores of scientists who contributed to an exciting new view of the earth?

And why on earth was Archimedes inspired by an overflowing bathtub?

OLLI at Penn State — open to adults who love to learn — has offered more than 140 courses this spring. Bob Schmalz will lead an OLLI course on "Floating Continents? Colliding Continents?" To receive a free catalog for the summer session, call OLLI at Penn State at 867-4278 or visit

Robert Schmalz, a retired professor geology at Penn State, lists his research interests as chemistry of natural waters, water supply problems and environmental radon. He also taught introductory courses in geology for majors and for nonscientists.