I glanced back at Sol. Look at the situation any way you liked; if I blew it and something went wrong, it was a long walk home.
I propelled myself gently away from the ship and towards McAndrew. He was staring at his mass detector readings in great irritation.
“Jeanie, you’ve made a mistake. We’re kilometers away from the source.”
“We certainly are. Two kilometers, to be exact. I know you can see right through it and it looks like nothing’s there, but I want to approach this particular nothing very carefully.”
He gave the patient sigh of a long-suffering martyr. “Ah, Jeanie. There’s no danger here, the way you’re thinking. I know just what this is.”
“Maybe. But you haven’t told me.”
“I will, though, right now. It’s shadow matter.” And then, seeing my stare, “I’m surprised you’ve not heard of it.”
“I know, Mac. I’m a constant disappointment to you. But I haven’t. So tell me.”
“It’s wonderful. Right out of supersymmetry theory. Soon after the Big Bang — about 10-43 seconds after it, actually, before anything else we know about happened — gravity decoupled from everything else. Sort of like the way that radiation decoupled from matter, but the gravity decoupling happened much earlier. So then you had a symmetry breaking, a sort of splitting, and two types of matter were created: ordinary matter and shadow matter. Just like matter and anti-matter — except that matter and shadow matter can’t interact by strong nuclear forces, or radiation, or the weak nuclear force. They can only interact by gravitational influence. You’d never detect shadow matter by firing particles at it. We proved that for ourselves. The particles feel the gravitational force, but that’s tens of orders of magnitude too weak to do anything noticeable.”
I stared at nothing, in the direction that the mass detectors were pointing. “You’re saying that whatever is out there is as real as we are — but we can’t see it?”
“Can’t see it, never will be able to see it. Seeing depends on interaction with radiation. The only way to learn what we’ve found is through these.” He pointed at the mass detectors. “We’re safe enough, as I said. But we have to do some detailed mapping. Who knows what that is out there? It could be a shadow matter star — we don’t have any idea how big a star might be in that universe, or what the laws of force are. Or maybe we’re detecting a set of interstellar shadow matter spaceships, or a column of shadow matter ants marching in a shadow matter superworld.
“You think I’m joking, but I’m not. It could be anything. The only way we’ll get any idea what we’ve found is by plotting structure. That’s why I need you — it’s a two-person job, to make transects.”
We’re safe enough, he had said. But maybe only while we were outside the Hoatzin.
“Mac, before we start your work we’ve got to talk. I think we have a bad problem.” I told him about the Dummy’s Delight on the ship’s computer.
He frowned through his suit visor. “But why would they waste data storage on a thing like that?”
“So they could get home, even if something happened to both of us.” I took the last mental step, the one I had been resisting. “Mac, we’re not intended to return from this trip. The plan is for us to vanish while we’re out here. If the drive of the ship were turned on now, who’d ever know what had happened to us?”
He turned to stare at the Hoatzin. “They wouldn’t dare.”
“Not now they wouldn’t. I wiped the program they were relying on to fly them back. So they need us.” Or one of us. But I didn’t say that. “We’re safe enough for the moment.”
“But what about when we go back inside? We can’t stay out here forever.”
“I don’t have an answer for you. We’ve got enough air for six or seven hours. We have to think of something — soon.”
We had to think of something. But we didn’t succeed. My mind stayed blank. McAndrew is a superbrain, but not when it comes to this sort of problem. After half an hour floating free not far from the ship, he shook his head.
“It’s got me beat. But this is silly. There’s no point in sitting here doing nothing. We might as well get on with the measurements.”
He placed one mass detector in my care, with its inertial position sensor tuned to the Hoatzin as reference, and started to steer me under his direction from one fixed place to another, while he moved himself in constant relative motion. He apparently knew exactly what he wanted. That was just as well. My own thoughts were all on the situation aboard the ship. What would we do when our air ran low?
I worried that problem with no result while McAndrew made four straight-line passages, right through the middle of the kilometer-wide region that he described as shadow matter. The mass detectors confirmed that something was there. I saw absolutely nothing.
On the fifth passage through, McAndrew paused halfway. He called to me to move closer, while he carried his own detector through a complicated spiral in space. At the end of it he left his mass detector where it was, flew across to me, and examined the recording on my instrument.
“Well, I’m damned,” he said. “Jeanie, I think you were right. Stay there.” And leaving me mystified and feeling about as intelligent as a marker post, he flew away. This time he moved his mass detector through an even more complex path in space, pausing often and proceeding very cautiously.
“I’ve still no idea what this is, overall,” he said when he came back. “But I’ll tell you one thing for sure. There are structures in shadow space that I’ve never met in our spacetime.”
“Right about what?” I asked. “You just said I was right. But what was I right about?”
“That we ought not to set the ship in the middle of that, without knowing more about it. I’m seeing evidence of gravitational line singularities, or something very like them, running across the shadow matter region. You don’t find those in our universe. If we had flown in too close to one of them, we might have found ourselves in trouble.”
“You mean we’re not in trouble now? With Lyle and Parmikan waiting for us.”
“I’ve been thinking about that, too.” He came close, and his face was earnest and unshaven within his visor. “I think you’re overreacting. There’s no evidence at all that Lyle and Parmikan even knew there was a Dummy’s Delight set up in the Hoatzin’s computer. And certainly there’s no evidence they mean us any harm. But anyway,” he went on, before I could interrupt, “one thing’s for sure: When we go back in the lock, I should enter first while you stay outside. I know both of them, they respect me, and they’ll not do anything to hurt me.”
McAndrew is a pathetically bad liar. I didn’t argue with him. But when we were a few meters from the lock I said, “You’ve got it backwards. I’m the one they won’t hurt, because they need a pilot to get home. And you don’t know how to work our only weapon. Don’t stand too near the hatch of the lock.”
I dived for the airlock, pulled myself inside, and swung it closed in one movement, leaving Mac to bang on the outside. While the lock was filling with air I did a little work of my own. It required that three separate safety procedures be overridden, so it took a few minutes. At last I moved forward to open the inner lock door, then jumped back at once to stand by the outer one.
I didn’t know what I was expecting. Lyle and Parmikan, going about the normal business of the ship, with a stack of messy chores ready for me? Or waiting to complain that I had for no reason at all wiped out a program that one of them had set up in the computer, for a wholly innocent purpose?