He pointed to small blips in the output level of the instruments.

“Noise?” I suggested. “Or the result of our high velocity? Or maybe a local effect, something on the Hoatzin?” He had told me that his new instruments were supernaturally sensitive to disturbance.

“No, they’re definitely external, and far-off. And regular. That’s just the signals I’d be getting if massive objects were flying, evenly spaced, across my field of view. Except there’s nothing there. It’s a total mystery.”

“Then you’ll just have to be patient. We’re already past turn-around. In twelve days we’ll be there, and you’ll be able to see for your—”

“Crewman Roker!” It was Parmikan’s voice, ringing through the living capsule. “Come here immediately. I have a task that must be performed at once.”

I took a deep breath, and held it. Another fun-filled day was beginning. Twelve more to go, before we came to rest in the most perfect nothingness known to humans, half a light-year from the Sun.

With the whole habitable space of the Hoatzin only four meters across, I knew before we left the Institute that we’d be living close. But given the lack of privacy, there was one form of closeness I had never expected.

The surprise came late in the evening on the twenty-third day out, when Mac was in the shielded rear of the living capsule muttering over his still-anomalous instrument readings. The blips were growing. With Parmikan’s consent Mac had gradually changed our course, angling the ship’s direction of travel towards the strongest source of signal. We would arrive a tenth of a light-year away from our original destination, but as McAndrew pointed out, the choice of that had been more or less arbitrary. Any place where the matter density was unusually low would serve his purpose equally well.

By eleven o’clock Stefan Parmikan was asleep. I was sitting cross-legged on my bunk, listening to an Institute lecture from my talking library. It was “Modern Physics for Engineers,” by Gowers, Siclaro, and McAndrew, a course designed to be less high-powered than the straight two-hundred-proof Institute seminar presentations. There were three other series available, of rapidly descending levels of difficulty. They each had official names, but inside the Institute they were known as “Physics for Animals,” “Physics for Vegetables,” and “Physics for Football Players.”

I had brought all four, just in case, but I was holding my own with “Physics for Engineers.” I was finally gaining a clearer idea of just why we had to charge off half a light-year from Sol.

Something was absent from the Universe, something that the best brains around thought had to be there: Missing matter.

The “bright stuff” — visible matter — isn’t nearly enough to make the Universe hover on the fine line between expanding forever, and collapsing back one day to the Big Crunch. That’s what the theorists want, but there’s only about one percent of the mass needed in the bright stuff. You can pick up a factor of ten or so from matter that’s pretty much the same as visible matter, but happens to be too cold to see, and that’s all.

This leaves you about a factor of ten short on mass. And there you stick. You have to start laying bets on other, less familiar materials.

Neutrinos moving up close to the speed of light — hot dark matter — are one candidate. There are scads of neutrinos around, generated soon after the Big Bang but damnably difficult to find by experiment. Neutrinos don’t interact much with ordinary matter. They’d slip through light-years of solid lead, if you happened to have light-years of lead available. They’re a candidate for the missing matter, but they’re not the front runner. They don’t give a Universe with the right lumpy structure, and anyway they come up short on total mass.

The other candidates are much slower and heavier than neutrinos. They’re the cold dark matter school, axions and photinos and gravitinos, and they don’t give the right lumpiness to the Universe, either. Even adding them to the neutrino mass, the whole thing still came up too small. McAndrew was saying, in effect, we’ve gone as far as theories can go. Let’s get out there, where the experiments have a chance to succeed, and measure how much hot dark matter and cold dark matter is around. Then we’ll know where we stand.

It was all fairly new to me. I was concentrating deeply, struggling with the theories of WIMPs — Weakly Interacting Massive Particles — when I was interrupted.

For the past three days I had been aware of Van Lyle hanging around me. I became a lot more aware of him when two arms suddenly went around me from behind, and two hands clasped my breasts.

“Hey, Jeanie,” Lyle’s voice whispered in my ear. “You’ve got lovely tits. It’s going to be nice and quiet for a while. Want to get friendly?”

I jerked forward along the bunk, untangling my legs and trying to pull myself free. He was hanging on tight. That hurt.

“Get your damned hands off me.” I wanted to say something a lot worse, but I knew we were going to be cooped up in the same space for another few weeks, no matter what. I had been trained to avoid onboard confrontations, and I wanted to stay cool and end this politely.

I swung around to face him and pushed myself away.

“Oh, don’t be like that.” He was grinning, a big, smarmy God’s-gift-to-women grin. “Come on. Lighten up. We could have some real fun.”

He reached out towards my breast again, and I pushed his hand away. “Quit that, Lyle! I tell you, I’m not having any.”

“You haven’t tried it. Lots of women could tell you, you won’t be disappointed. Want to have a look at my testimonials?” And then, as I pushed his groping hand away again, this time when it reached towards my crotch, “Hey, Jeanie, you’re strong. I just love strong women.”

“You do, do you?” I’d had it. “This strong enough for you?”

I swung with all my body behind it as his face came forward, and got him with my fist right on the bridge of his nose.

It hurt like hell — hurt me, I mean. I didn’t care how much it hurt him. But I don’t think he enjoyed it, because as the blood spurted out of his flattened nose and splashed all over my bunk, he let out a terrible howl that brought McAndrew running.

Just as well, because by that time I was upright, off my bunk, and all set to kick Lyle in the balls at least ten times as hard as I’d punched his nose. McAndrew got in the way before I could do it. He leaned close to Van Lyle, a rag in his hand to mop up blood.

“What happened?”

Lyle produced only a horrible snorting noise.

“Tripped as he was coming in here,” I said, “and banged his face on the edge of the bunk. Get the medical kit.”

McAndrew glanced at the bunk as Stefan Parmikan finally appeared. I knew that Mac was doing an instant height and angle match, and rejecting it. But he never said a thing. Nor did Lyle, unless you count the groans when Parmikan was moving his broken nose around in an attempt to achieve a reasonably straight result.

We fixed the nose, more or less, and sedated Lyle. Parmikan went back to bed. During the sleep period, McAndrew leaned over the edge of my bunk and whispered to me. “Jeanie? I know you’re awake. Are you all right?”

“I’m just fine.” I didn’t want him as furious as I was.

“He didn’t bang himself on the bunk, did he? He made advances to you, and you hit him.”

“What makes you think that?” Mac’s insights were supposed to be into Nature, but not human nature.

“He was talking about you two days ago, when you weren’t present. He said he wanted to take you to bed. Get a piece, he said.”

“And you were there? Why for God’s sake didn’t you stop him? Tell him that you and I are lovers, have been for years.”