“What?”
“Well, the aurora borealis—and the aurora australis, too—have been acting up.”
Ponter was quite surprised. “No, nothing like that is currently occurring. In fact, I saw the night lights last evening; they were perfectly normal.”
Arnold looked disappointed. “We were hoping you guys would have some insight. Our best guess is that Earth’s magnetic field is collapsing, and the poles are perhaps going to reverse.”
Ponter raised his eyebrow again, rolling it up his browridge. “When was the last time something like that happened here?”
“I’m not sure off the top of my head. Many thousands of years ago.”
“There have been no field collapses since?”
“No.”
“Fascinating. We had one—Hak?”
“Six years ago,” said Hak, through his external speaker.
“You mean it ended six years ago?”
“Yes.”
“But it must have started centuries earlier.”
Ponter shook his head. “It started twenty-five years ago.”
“Let me get this straight,” said Arnold, eyes wide. “Your entire field collapse took just—what?—nineteen years?”
“That is correct,” said Ponter. “Up until twenty-five years ago, the magnetic field was at its normal strength. Then it collapsed; the planet did not have any appreciable magnetic field for the next nineteen years. And then, six years ago, the field popped back up.”
“‘Popped up’?” repeated Arnold, astonished. “No, you must be joking.”
“When I joke,” said Ponter, “I strive to be much funnier.”
“But…but…we’ve always believed the magnetic field would take hundreds, and probably thousands, of years to collapse.”
“Why?”
“Well, you know, because of the size of the Earth.”
“The sun’s magnetic field reverses every hundred and forty months or so—every eleven years—and the sun is about a million times the size of Earth.”
“Yes, but…”
“I do not mean to sound grayer than you,” said Ponter. “We knew very little about field collapses, too, until we actually experienced one happening. Some of our geologists were astonished by the rapidity, as well.”
“Geomagnetic collapse and reestablishment in less than two decades,” said Arnold. “Incredible.”
“It was an interesting time to do physics,” said Ponter. “Our people learned a great deal about the—the process by which the field…you must have a word for it?”
Arnold nodded. “The geodynamo.”
Ponter frowned; another ee phoneme. But he let Hak take care of supplying it as needed; it was only proper names that Ponter had his Companion repeat exactly as he spoke them. “Yes. We learned much about the geodynamo.”
“We’d love to hear what you know,” said Arnold.
Ponter was glad that Tukana was asleep; he’d probably given away too much information already. But this concept of trading data—it upset the scientist in him. All data should be freely exchanged. Still, he decided to shift the topic slightly. “Is Inco worried that the demand for nickel will abate during the period of collapse?” Nickel was widely used in compasses on both versions of Earth—and the deposit here in Sudbury was one of the world’s largest.
“What? Hmm, I hadn’t even thought about that,” said Arnold.
Ponter was confused. “Reuben said you were a geologist…?”
“Yes, I am,” said Arnold, “but I don’t work for Inco. I’m with Environment Canada. I flew here from Ottawa as soon as word came that contact with your world had been reestablished.”
“Ah,” said Ponter, still not understanding.
“My job is protecting the environment,” said Arnold.
“Is that not everyone’s job?” asked Ponter, being, he knew, a bit disingenuous.
But again the subtlety was lost on Arnold. “Yes, indeed,” he said. “Yes, indeed. But I wanted to find out what your people might know about environmental effects associated with magnetic-field collapses. I was hoping you might have some data from the fossil record—but to have complete studies of a recent collapse! That’s fabulous.”
“There were no appreciable environmental effects,” said Ponter. “Some migratory birds were confused, but that was about it.”
“I suppose they would be, at that,” said Arnold. “How did they adapt?”
“The affected birds have a powerfully magnetic substance in their brains…”
“Magnetite,” supplied Arnold. “Lodestone. Three iron atoms and four oxygens.”
“Yes,” said Ponter. “Other kinds of birds navigate by the stars, and some individuals of the species that use brain magnetite for determining direction turned out to be able to use the stars, too. It is ever the way in nature: variation within a population provides vigor when the environment changes, and most crucial capabilities have a backup system.”
“Fascinating,” said Arnold. “Fascinating. Tell me, though: how did you originally determine that Earth’s magnetic field does, in fact, periodically reverse? That’s a fairly new insight for us.”
“The alternation of the planet’s magnetic-field polarity is recorded at meteor-impact sites.”
“It is?” said Arnold, his one long eyebrow—how refreshing to see someone who looked normal, at least in that regard!—rising up his forehead.
“Yes,” said Ponter. “When an iron-nickel meteor slams into the Earth, the impact aligns the meteor’s magnetic field.”
Arnold frowned. “I suppose it would, at that. Just like hitting an iron bar with a hammer and turning it into a magnet.”
“Exactly,” said Ponter. “But if you did not learn of this from meteorites, how did your people come to know that Earth’s magnetic field periodically reverses?”
“Sea-floor spreading,” replied Arnold.
“What?” said Ponter
“Do you know about plate tectonics?” asked Arnold. “You know, continental drift?”
“The continents drift?” said Ponter, making his face agog. But then he held up a hand. “No, that time I was making a joke. Yes, my people know this. After all, the coastlines of Ranilass and Podlar clearly once were attached to each other.”
“You must mean South America and Africa,” said Arnold, nodding. He smiled ruefully. “Yes, you’d think it would be blindingly obvious to everyone, but it took decades for our people to accept the notion.”
“Why?”
Arnold spread his arms. “You’re a scientist; surely you understand. The old guard thought they knew how the world worked, and they weren’t about to give up their theories. As with so many paradigm shifts, it wasn’t really a case of convincing anyone to change their minds. Rather, it was waiting for the previous generation to pass on.”
Ponter tried to conceal his astonishment. What an extraordinary approach to science these Gliksins had!
“In any event,” continued Arnold, “we ultimately found proof for continental drift. At the middle of the oceans there are places where magma wells up from the mantle, forming new rock.”
“We surmised such things must exist,” said Ponter. “After all, since there are places where old rock is pushed down—”
“Subduction zones,” supplied Arnold.
“As you say,” said Ponter. “If there are places where old rocks go down, we knew there must be places where new rock comes up, although, of course, we have never seen them.”
“We’ve taken core samples from them,” said Arnold.
Ponter’s face went honestly agog this time. “In the middle of the oceans?”
“Yes, indeed,” said Arnold, clearly glad for once that his side was coming out ahead. “And if you look at rocks on both sides of the rifts from which magma is welling up, you see symmetrical patterns of magnetism—normal on either side of the rift, reversed equal distances to the left and right of the rift, normal again on either side but farther out, and so on.”
“Impressive,” said Ponter.
“We have our moments,” said Arnold. He grinned, and was clearly inviting Ponter to do the same.