“Glad to,” Hibbet said. “The earth is like a big bar magnet. The inner core of solid iron rotates at a different speed from the outer core of molten iron. This movement creates a dynamo effect that generates a magnetic field called the geodynamo.”

The picture changed to depict the intact globe. Lines looped out into space from one pole and curved back into the opposing pole.

“Those are the lines of magnetic force,” Hibbet explained. “They create a magnetic field that surrounds the earth, and allows us to use compasses. Even more important, the magnetosphere extends out thirty-seven miles. This creates a barrier that protects us from the harmful solar wind radiation and swarms of deadly particles that bombard the earth from space.”

Trout changed the computer image. They were looking at a map of the world. The ocean surface was splotched with blue and gold patches.

“In the 1990s, scientists pulled together everything known about the earth's molten core and fed it into a supercomputer,” Trout said. “They threw all sorts of stuff into the mix. Temperature. Dimensions. Viscosity. They found that the poles reversed themselves every hundred thousand years or so, usually when one started to weaken. It looks like we're in for another cycle.”

“The earth is undergoing a natural polar reversal?” Adler said.

“Apparently,” Trout said. “The earth's magnetic field started to deteriorate seriously around a hundred and fifty years ago. Its strength has waned by ten to fifteen percent since then, and the deterioration in the field has accelerated. If the trend continues, the main field would waken and almost vanish, and it would reappear with the opposite polarity.”

“Needles that point north would point south,” Hibbet added.

“That's right,” Trout said. “A magnetic polar reversal would mean a whole host of disruptive events, but the impact would be minimal. Most of us would be able to adapt and survive. Studies show that the magnetic poles have reversed many times.”

“Herodotus wrote about the sun rising where it normally sets,” Gamay said. “The Hopi talked about the chaos that comes about when the two twins who hold the earth in place leave their position. These could have been interpretations of ancient polar shifts.”

“While legend is fascinating, and often contains a grain of truth, all of us at this table are versed in the scientific method,” Adler said.

“That's why I didn't mention the clairvoyants and pseudoscientists who predicted an end of the world,” Gamay said. “The whole concept of polar shift got mixed up with theories of Atlantis and ancient astronauts.”

“As a wave expert, I deal with huge ocean forces,” Adler said, “but a shift in the outer surface of an entire world seems unbelievable.”

“Normally, I would agree,” Gamay said. "But paleomagnetists who have studied lava flows have shown that the ground, has moved in relation to the earth's magnetic north. North America was once deep in the Southern Hemisphere, where it straddled the equator.