Scooting along over the clouds I could now see a pattern to the lightning. It moved in great waves over the surface, reaching peaks in places, fading elsewhere. We had lifted from a point where all the peaks had converged, but now it was fading to look no different from the rest. Or almost so; the faint shadow of the black funnel still dipped down into the murk.
I felt a tap on my shoulder. Mac was gesturing at me, then at the helmet of his suit. I nodded and broke the seal on my own helmet. We were outside the danger zone, and it was important to reestablish contact among the group. The search for Hoatzin and Merganser might take hours, with no assistance from automated scan instruments or radio receipt of homing signals. Meanwhile, I wanted some explanations. It was clear that McAndrew and Wicklund between them had more idea than I did what had been happening.
Three miserable, greenish-yellow faces emerged from the helmets. No one had thrown up, but from the look of them it had been a close thing.
“I thought it was bad when the storm hit us on the surface,” said Jan. “But that was even worse. What did you do to us, Jeanie? I thought the pod was coming apart.”
“So did I.” Suit helmet off, I reached back to massage the aching muscles in my neck and shoulders. “It almost did. We lost the computers, the communications, the displays — everything. What is this crazy planet, anyway? I thought the laws of nature were supposed to be the same all over the universe, but Vandell seems to have a special exemption. What in hell did you two do to the place, Jan? It was quiet as a grave until you got at it.”
“It damn near was one,” said McAndrew. “If you hadn’t…”
He paused and swallowed. “We know what’s going on. That’s what we were talking about before you shook us to pieces. If we’d been a bit smarter, we could have inferred it ahead of time and none of this would have happened. How much did you hear on the way up?”
I shook my head. “I tuned you out. I had other things on my mind. Are you telling me you understand that mess down there? I thought you said it made no sense at all.”
While we spoke I had taken us up to the correct height above Vandell for rendezvous with Hoatzin. Now it would need a steady and simple sweep to find our ship.
McAndrew wiped his hand across his pale, sweating forehead. He was looking awful, but less like a dying pickle as the minutes passed. “It didn’t make sense,” he said huskily. “Nothing ever does before you understand it, and then it seems obvious. I noticed something odd just before we left Hoatzin to go into the pod — Sven had wondered about the same thing, but neither of us gave it enough significance. Remember the list of physical variables that they recorded for Vandell when they first arrived here? No electric and magnetic fields, negligible rotation rate, no atmosphere, and cold as the pit. Does any one of those observations suggest anything to you?”
I leaned against the padded seat back. My physical exertions over the past half hour had been negligible, but tension had exhausted me totally. I looked across at him.
“Mac, I’m in no condition for guessing games. I’m too tired. For God’s sake, get on with it.”
He peered at me sympathetically. “Aye, you’re right. Let me begin at the beginning, and keep it simple. We know that Vandell was quiet until Merganser’s pod landed on its surface. Within minutes of that, there was massive seismic activity and terrific electric and magnetic disturbances. We watched it, there were waves of activity over the whole planet — but they all had one focus, and one point of origin: where the pod landed.” As McAndrew spoke his voice became firmer, strengthening now that he was back on the familiar ground of scientific explanation. “Remember the dark cone that we followed in to the surface? It was the only anomaly visible over the whole surface of the planet. So it was obvious. The impact of the pod caused the trouble, it was the trigger that set off Vandell’s eruption.”
I looked around at the others. They all seemed happy with the explanation, but to me it said absolutely nothing. I shook my head. “Mac, I’ve landed on fifty planets and asteroids through the System and the Halo. Never once has one shaken apart when I tried to set foot on it. So why? Why did it happen to Vandell?”
“Because—”
“Because Vandell is a rogue world,” interrupted Sven Wicklund. We all stared at him in amazement. Sven usually never said a word about anything (except of course physics) unless he was asked a direct question. He was too shy. Now his blond hair was wet with perspiration, and there was still that distant, mystic look on his face, the look that vanished only when he laughed. But his voice was forceful. Vandell had done something to him, too.
“A rogue world,” he went on. “And one that does not rotate on its axis. That is the crux of this whole affair. Vandell rotates too slowly for us to measure it. McAndrew and I noticed that, but we thought it no more than a point of academic interest. As Eddington pointed out centuries ago, almost everything in the Universe seems to rotate — atoms, molecules, planets, stars, galaxies. But there is no law of nature that obliges a body to rotate relative to the stars. Vandell did not, but we thought it only a curious accident.”
He leaned towards me. “Think back to the time — how many million years ago? — when Vandell was first ejected from its stellar system. It had been close to the system’s suns, exposed to great forces. It was hot, and maybe geologically active, and then suddenly it was thrown out, out into the void between the stars. What happened then?”
He paused, but I knew he was not expecting an answer. I waited.
He shrugged. “Nothing happened,” he said. “For millions or billions of years, Vandell was alone. It slowly lost heat, cooled, contracted — just as the planets of the Solar System cooled and contracted after they were first formed. But there is one critical difference: the planets circle the Sun, and each other. As tensions inside build up, tidal forces work to release them. Earth and the planets release accumulating internal stresses through sequences of small disturbances — earthquakes, Marsquakes, Jupiterquakes. They can never build up a large store of pent-up energy. They are nudged continuously to internal stability by the other bodies of the system. But not Vandell. It wanders alone. With no tidal forces to work on it — not even the forces caused by its rotation in the galactic gravitational and magnetic fields — Vandell became super-critical. It was a house of cards, unstable against small disturbances. Apply one shock, and all the stored energy would be released in a chain reaction.”
He paused and looked around. Then he blushed and seemed surprised at his own sudden eloquence. We all waited. Nothing else was forthcoming.
I had followed what he said without difficulty, but accepting it was another matter. “You’re telling me that everything on Vandell came from the pod’s landing,” I said. “But what about the dust clouds? And why the intense fields? And how could they arise from an internal adjustment — even a violent one? And why were there peaks in the disturbance, like the one when we lifted off?”
Sven Wicklund didn’t answer. He had apparently done his speaking for the day. He looked beseechingly for support to McAndrew, who coughed and rubbed at his head.
“Now, Jeanie,” he said, “you could answer those questions for yourself if you wanted to give it a minute’s thought. You know about positions of unstable equilibrium as well as I do. Make an infinitesimal displacement, and produce an unbounded change, that’s the heart of it. Compared with the disturbances on Vandell for the past few eons, the landing of a pod was a super-powerful shock — more than an infinitesimal nudge. And you expect a set of spherical harmonics — with a pole at the source of energy — when you distribute energy over a sphere. As for the fields, I’ll bet that you’re not enough of a student of science to know what a Wimshurst machine is; but I’ve seen one. It was an old way of generating tremendous electromagnetic fields and artificial lightning using simple friction of plates against each other. Vandell’s crustal motion could generate fields of billions of volts, though of course they’d only last a few hours. We were there right at the worst time.”