"Mac, stop being literal-minded." No chance of that. "For starters, you can tell me what secret you've been sitting on since I arrived."
"Secret?" He was all bland innocence. "I don't have a secret."
* * *
But I was sure he did. And once we were heading out he retreated into his private mental world. I might have been at a loss, but something that Abdi had said at our first meeting gave me an idea. It was his ambition—at least until he changed his mind—to be a spaceship captain. He was fifteen years and a lot of hard work away from that, but if he was willing I could give him a running start.
It turned out he was a good student, given that he was so fidgety he had to be hopping about and doing something different every twenty minutes. He was enormously inquisitive, and wanted to know how everything worked. One of the communications units had not been performing up to par when we left the Penrose Institute. With Abdi's assistance, I stripped the unit down to discover the problem. Then there was the job of putting it back together from the thousand bits and pieces scattered around the living quarters.
That was enjoyable, and in a perverse way I welcomed Abdi's company. Of course, given the tight space in the Hoatzin, Mac and I didn't get any chance for personal interaction. That would have been tolerable, too, except that near the end of the outward run Mac had the gall to say to me, "You and your worrying. Hasn't this been the smoothest trip you could ask for?" He rubbed his hands together. "In a couple of hours the drive goes off. And then the fun starts."
At the halfway point the ship had turned and begun the deceleration phase. From the living capsule I had a clear view out along the central shaft to open space beyond. I had looked that way occasionally for the past eight days, and seen nothing. More to the point, I saw nothing now and we were almost there.
"What were you expecting, Jeanie?" McAndrew said, and Abdi, who had also been staring out, turned to watch the two of us.
"Well . . ." A hole in the universe? That was something neither I nor anyone else had ever seen. I vaguely imagined streams of light and particles, jetting out like a great fountain into space. "You said that matter was appearing from nowhere. I thought we would see it."
"It depends what you mean by see it. A hundred million tons appear every hour, but the caesura—the hole in space—is three hundred kilometers across, and naturally it's three-dimensional. Spectroscopic analysis suggests that almost everything coming through is neutral hydrogen, and it disperses rapidly. When you do the arithmetic you find that the region ahead is much less dense than the air we're breathing. I doubt anyone would have picked this up if there hadn't been a refractive effect around the whole region. The images of distant stars change from points to little rings of light." He smiled. "There's something interesting going on, no doubt about it."
"You're not thinking of taking the Hoatzin any closer, are you?" I knew that McAndrew's sense of danger was about as well developed as his dress sense.
"No, no. I expect that the region is safe enough, but we'll park at a distance with the drive off. There's a whole slew of observations that I'm keen to make."
Reassuring? It might have been, except that the space pinnace was hanging out at the end of the central axle.
I persisted. "You brought a pinnace all this way, and you don't plan to go near the region at all?"
"Well, I wouldn't go quite that far. It would be fascinating to see what it's like close up. But I would never do that until I was sure we were safe. It's observations first, today and tomorrow. Then we'll see. Would you like to help set up the instruments?"
He addressed that question to Abdi, who -nodded eagerly. So once the drive went off and we hung motionless in space—I could still see nothing ahead—the two of them headed out to the very end of the axle. A cluster of special instruments had been set in place there before we left the Institute.
For the next peaceful half day I was alone with my thoughts. One result was that by the time they rolled back into the living capsule, tired and hungry, I had decided that McAndrew's explanations to date provided more confusion than clarity.
"I know there's matter coming out from nowhere." I had already eaten, and I watched the other two as they gobbled down everything in sight. "But Mac, that doesn't make any sense to me. Matter must come from somewhere."
He wiped his mouth on his shirt sleeve. "Oh, it does. It's a standard prediction of brane theory."
"Brain theory—the way we think?"
"No, no. B-R-A-N-E. The word's short for membrane, and the result follows from an old extension of superstring theory. Things that lie close together on a multidimensional membrane—separate universes, if you want to think of them that way—can touch. One theory suggests that our whole universe began when two neighboring brane elements collided. We're looking at something much smaller here, just one little region of contact between us and a neighboring universe. Of course, there may be billions or trillions of others like it, scattered around in places too far off for us to see them."
He had finished eating, and now he yawned. "I'll go into detail tomorrow if you like. But it's been a long day, and I want an early start."
"That's all right." I suspected he had gone as far as he could without becoming unintelligible to me. "Get some sleep. You too, Abdi, so we'll all be up bright and early in the morning."
I expected resistance—Abdi hated to go to bed—but for a change he didn't argue. He stood up without a word, and was gone.
He was also gone the next morning, though McAndrew and I didn't realize it at first. I was saying, "If he doesn't get his sleepy head out of his bunk in the next few minutes, he'll miss breakfast," when McAndrew interrupted.
"The pinnace!" He was staring out of the cabin's top window.
"What about the pinnace?"
"It's not there."
"You think it came loose and drifted away?"
"I don't see how it could." He was already struggling into a suit. Before he was half done with that I was over at Abdi's bunk, pulling back the curtain.
"Mac, Abdi's not here! He must have taken the pinnace."
"I don't think so. We told him not to, and he agreed."
I was thinking back. "That's not quite true. We told him that he wasn't to do anything with the pinnace before we left the Institute. We didn't say a word about after we arrived. I think Abdi interprets things in his own way. If you tell him not to do something, he won't. But anything that's not explicitly forbidden, he treats as permitted."
As I spoke I was using the external sensors to scan space in all directions. "Where could he have gone? I see no sign, and the pinnace has a low-thrust drive. It's not designed to take you far away."
"Oh Lord." McAndrew paused with one arm in his suit and leaned his head back against the living capsule wall. "All those questions he asked yesterday. I assumed the little bugger had just a casual interest."
"Mac, stop speaking in riddles and tell me what's going on. Where is Abdi? And what's—"
He held up his hand. "I know where he is. I have to go after him. Before that, you need to understand what we're getting into. It could be dangerous."
"If Abdi is in danger, we can't sit around for explanations."
"The full story can wait, but there are things you absolutely have to know. You see, Jeanie, it's a two-way street. It has to be. If matter can emerge from a neighboring universe into ours, matter from here must be able to go there. I was hoping that the transfer might work for something a lot bigger than individual atoms. That's why I brought the pinnace, in case we had a chance to go next door and learn what it's like."
"And you told all that to Abdi?!"
"I might have. I suppose I did. But I would never have dreamed of trying the transfer until we'd made hundreds of measurements using small probes, and we knew it was safe."
"Were you thinking you might come out somewhere dangerous—near a star, maybe, or a planet?"
"Worse than that, Jeanie. We're seeing what looks like hydrogen atoms coming thro
ugh, and you might say that's a good sign because it suggests physics there isn't much different from what it is here. But tiny changes in the weak force or the strong force would make any atom quite different in its properties. I'm not sure that life as we know it can exist on the other side."
"You mean Abdi could already be dead?"
"That's what I'm afraid of. Either way, this is my fault. I have to go and find him. We don't have another pinnace, but I doubt that he has gone far. The drive on a suit should be enough."
He was starting forward when I grabbed his arm. "The pinnace has a communications unit. You said that radiation goes between the universes. We can call Abdi, and ask where he is."
"We can. But take a look." He nodded toward the console. "No carrier signal. Either the unit on the pinnace was never turned on, or Abdi switched it off."
I was still gripping his arm. "Mac, why do you imagine Professor Limperis and the others at the Institute wanted me to travel with you?" That earned a blank stare, and I went on, "They trust that I'm cautious, and they know for sure that when you get an idea in your head, caution is the last word anyone would apply to you."
"You said we don't have time for philosophical discussions. Now you're trying to start one."
"Not philosophical. Practical. Mac, you mustn't try universe-hopping alone. Either we both go, or nobody does."
"That's a terrible idea. Abdi and I need a backup. Suppose we both get in trouble?"
"Suppose you do. What am I supposed to do? Sit here at the edge of creation until supplies run out, then turn and head for home? I would have no idea how to act if you disappeared."
He pursed his lips and said nothing.
I continued, "On the other hand, if I went looking for Abdi and you stayed here, you could take action if I was in trouble. You know a thousand times as much as I do about where we are, and what's going on."
"If it were a million times as much it might not be enough. Jeanie, you can't travel alone through the caesura and into the other universe."
"Nor can you. And I'd be no help back here."
And that, after a lot more argument, kind of settled the matter. We would both be going—but not before McAndrew insisted on telling me more than I wished to know about the overall situation.
"It's natural to think about the material that enters our universe, because that's what we see. But the second law of thermodynamics is more complex than that. Let me give you an example, Jeanie."
We were makings preparations to leave the Hoatzin in our suits alone. We could stay away from the ship for up to thirty hours, then it was return or die.
He went on, "Suppose you have a box divided into halves by a solid partition. Nothing can pass through, not even heat. Call the boxes A and B, and imagine that they represent separate universes. On each side of the partition you have matter. Let's say it's a gas. The temperatures are the same in A and B, and so are the pressures. If the gas on each side of the partition is perfectly mixed, that's as disordered as you can get. Entropy is at a maximum on each sides. Now you make a hole in the partition. Is there any observable effect from making that hole?"
I was dying to leave, but if he said I needed to know, I was forced to accept his rambling. I said impatiently, "The gases from both sides mix, but they were at the same temperature and pressure to start with. Things were as random as you could get. You shouldn't notice any difference at all."
"Shouldn't, and wouldn't. But suppose I give you another piece of information. Suppose the gas in box A is different from the gas in box B. Maybe, it's oxygen in A and hydrogen in B. Before the hole was made, the gas on each side had maximum entropy and maximum disorder. I couldn't produce energy from the gas inside either box. But once I make the hole we have a combined system. Hydrogen molecules from B start going into A. If I'm sitting in A, I will notice the change and I can measure it. I will say to myself, 'Aha! Entropy is going down around that hole.' I know, because if I strike a spark the new hydrogen molecules will combine with some of the oxygen molecules, and produce energy.
"But now suppose I'm sitting in B. Oxygen molecules are arriving, so near the hole I can strike a spark and combine them with some of the hydrogen to generate energy. I will reach the same conclusion as I did in A. Entropy in B is decreasing, too."
"Mac, entropy always increases. Isn't that the second law of thermodynamics?" As usual when I talked with McAndrew, I was more confused instead of less. "You have it decreasing in both boxes."
"That's right. It must, since the situation is perfectly symmetrical. But because of the hole connecting them, neither A nor B is now a closed system. The complete system is (A + B), and it's the entropy of that which has to increase. It may not look like it to someone in either box, but the total degree of randomness is going up. Eventually, all the gas will be perfectly mixed."
"We see things from only one box. Is that your point?"
"Part of it. But I want to emphasize the symmetry. We have matter coming in from outside—from another box or another universe. And things can run both ways. If matter comes from there to here, it can just as likely go from here to there."
"Separate atoms and molecules."
"Sure. But maybe more. What we lose must be different from what we gain, or we'd see no entropy change. Maybe bigger things can go the other way. Like the pinnace."
"And Abdi."
"Right. And the problem is, we have no idea how much energy his arrival might trigger in the other universe."
"But we're going to find out."
"I suppose we are. Unless you will let me go alone—"
As I said, when he gets an idea in his head he never gives up. Of course, that doesn't mean you have to let him act on it.
The hole in the universe was invisible, but McAndrew had plotted its boundary and knew exactly where it was. A hundred meters from the edge he halted and said over his suit radio, "Can you hear me?"
"As clear as if you were sitting next to me on board the Hoatzin." Which I wished was the case. I looked back at the ship, less than ten kilometers away. The central shaft and living-quarters were invisible, but the mass plate hung like a silver coin in space.
"We stay close, Jeanie. We move forward together, and make sure we can still see and talk to each other."
We gripped gloved hands. Side by side we drifted toward the caesura, the nothing, the three-dimensional hole in the wall of the universe. I felt nothing, but without warning the darkness around me disappeared. I moved through a shimmer of light, multicolored and constantly changing. No longer in any place that I could recognize, I suspected I was between universes.
The display of my inertial guidance system, designed to track position in three-dimensional space, suddenly went blank. It lit again after a few seconds, but its spatial coordinates had reset to zero values. At the same time, everything around me went dark. My suit radio filled with a roar of static.
"Mac, where are we?" I hoped my voice was calmer than I was.
"We made it through in one piece." His voice was a near-unintelligible thread of sound, but I could hear the satisfaction. "So chances are that Abdi is all right. Hold on, and set your suit to roam. I'm going to try different frequencies."
Nothing happened for about thirty seconds. While I waited I realized that the space surrounding us was not completely dark. A faint, pearly radiance glimmered in from all directions. It was just enough to show the outline of my arm.
"How about that? Better?" McAndrew's voice was much clearer.
"Lots better. I can hear you now. Do you know what's going on?"
"Sure. We've arrived in a universe where the dominant radiation is at radio frequencies, probably generated by discrete sources. I picked the quietest region I could find and tuned us to it. Visible wavelengths seem to come from a general background. If there are stars, they are radio stars."
His words were distinct enough, but there was a curious background echo to them, as though everything was being repeated a fraction of a second later. I turned o
n my helmet light and directed its beam at McAndrew.
There he was, clear and unmistakable, but faint shadow images of his suit marched away to left and right, above and below, diminishing ghostly arrays that shrank in size until they merged into the pearly background.
"Mac, turn on your helmet light and point it at me."
Not one light appeared, but a whole constellation of them. They blinded me to anything beyond.
I said, "What do you see?"
"Same as you do, I imagine. I'm only guessing, mind, but I'd say this is a spacetime with a totally different structure. It's built of discrete units on a macro scale, at least so far as optical properties are concerned. I want to try an experiment." His hand released its hold on mine. "Stay right where you are, Jeanie."
I certainly wasn't going anywhere. I kept my light focused on McAndrew's suit, and watched uneasily as it receded from me. It was no more than fifty meters away when the structured array of images turned into a bland glow, little brighter than the background.
"Mac, I've lost you. You've disappeared."
Not a word of reply, only the steady hiss of static. The urge to drive my suit toward the direction where I had last seen him was very strong. I fought it, hovering frozen in space. I could hear my pulse, loud in my ears. I counted the beats. Sixty—eighty—a hundred. On the hundred and twelfth beat, a suited figure popped back in sight, accompanied by its retinue of ghostly images.
"I'm seeing you again, Jeanie," Mac said. "And hearing you. Is it two-way?"
"Yes."
"That's reassuring. I was afraid for a minute we might be in a spacetime with asymmetric affine connections, and no metric."
He reassured a lot easier than I did. But perhaps not, because his next words came in a voice more serious than I had ever heard before.
"Here's the problem, Jeanie, and I must admit it's not one I'd ever anticipated. We need to find Abdi and the pinnace, but we seem to be stuck with a distance limit of fifty meters for any form of electromagnetic propagation. If the common region is the same size in the two universes, then we're dealing with a space about three hundred kilometers across. That gives us a finite volume to search, which is good news. The bad news is the length of time it will take us if we're stuck with traverses that are only a hundred meters wide. We'll run out of air and fuel for our suit drives, long before we're done."
Cosmic Tales - Adventures in Sol System Page 3