“It’s not a time to feel ignoble,” Sariena told him. “Sending the women and children first might have some point on a sinking ship, where there’s an intact civilization for them to go back to, but in this situation we’re going to have to rebuild civilization. It’s going to need people like you every bit as much as new blood. You’re an engineer and a scientist, Lan. What will you do here when it’s over? Charlie can see the logic of it. He’s only being realistic.”
Keene was reacting to an instinct that he was unable to articulate and so took the opportunity to steer the talk onto a different tack. “I used to be a scientist,” he said. “But that was only until I saw what it was turning into.”
“What Earth turned it into,” Sariena replied. “What’s at Kronia is different—the way you’ve always said science should be. We’ve talked enough about it. Don’t you want to be a part of that?”
Keene leaned his elbows on a guardrail beside an access pit leading down under some machinery and sighed, giving her a tired smile. She was still selling hard—and doing a good job. “The beginnings of a whole new science,” he said. “It was just starting to get interesting too, wasn’t it? Did you ever think any more about the dinosaurs? When did Vicki and I call in the middle of the night? Five days ago, was it? I’ve lost all track.”
“We had some exchanges with the Kronian scientists while we were in Washington,” Sariena said. “Basically, they’re intrigued by the idea. They’ve got a possible theory about why that estimate of yours didn’t work.” She meant the rough calculation that Keene had made of how much Earth’s surface gravity would be reduced in a phase-locked orbit close to Saturn.
“What?” Keene asked.
“They think Earth may have gone through not one phase of gravity increase, but two. You only covered one of them.”
“Two?” Keene repeated, looking puzzled.
“Somebody there came up with the thought that maybe the account of an impacting body wiping out the dinosaurs, is only half the story. If it was high in density, say, five to ten times that of the crust, and large enough, then absorbing it into the Earth’s core would cause a significant increase in surface gravity. So before the impact, two factors were operating: the mass was smaller, and you had the effect of being close to the giant primary. When the gravity increased due to the extra mass being added, none of the giant life-forms that had existed previously could survive.”
Keene stared at her, trying to visualize what she was saying. It did make a strange kind of sense. A planet like Earth was molten inside a sticky bag of mantle, topped by a crumbly crust—not solid all the way through in a way that would shatter. A small, dense object penetrating and being absorbed would certainly have been possible. “But we’re still a satellite of Saturn,” he checked.
“Right. Maybe knocked out to a looser orbit.”
“So life is reduced in size, but still bigger than what we’ve got today.”
Sariena nodded again. “And how’s this for a coincidence? Taking the figures I used a moment ago, with the impacting body a fifth of Earth’s initial volume, the amount you’d have to shrink a dinosaur by to get back to the same strength-weight ratio that you had under the lower-gravity conditions, works out at about forty percent. That gets you just about down to the size of the titanoheres—the giant mammals that lived until the end of the Pliocene.”
The implication was clear. Keene scanned her face, as if looking for a hint that he wasn’t jumping ahead prematurely. “So are you saying that was when Earth detached from Saturn—and gravity increased a second time to become what we’ve got now?” He nodded slowly to himself as he thought about it. And by that time, humans could have existed to witness it—the Joktanians and very likely others, long predating what had been thought to be the earliest civilizations. Huge, too. The giant humans had existed along with the giant mammals.
“We don’t know what caused it to detach,” Sariena said. “Maybe another impact event—enough to have ejected the artifacts that were found on Rhea. That’s just a guess, of course, but it fits. . . . In fact, it fits with a lot of things.” Keene stared at her again. And so the temporarily orphaned Earth would have begun falling toward the Sun, away from the cradle that had seen its life begin, and warmed it benignly and nurtured it. For how long would it have fallen inward?