So the ship moves at just under a tenth of the speed of light, through a self-generated cone of near vacuum. There is some ablation of the ship’s surface from infrequent contacts with undeflected hydrogen atoms. Cosmic radiation also regularly penetrates it, usually without hitting any atoms of the ship, but rather passing through the matrix of those atoms unimpeded. It is as if ghosts that pass through the ship tear at its fabric, or don’t. This is noticeable; there are sensors that register these occasional atomic hits, also the pass-throughs. It is also true that there is a continuous flood of dark matter and neutrinos always flying through the ship, as they do through everything in the universe, but these interact very weakly indeed; once a day or so, a flash of Cherenkov radiation sparks in the water tanks, marking a neutrino hitting a muon. Once in a blue muon. Same with the dark matter, which visible matter moves through as if through a ghost ether, a ghost universe; once or twice a weakly interactive massive particle has chipped away from a collision and registered on the detectors.

Fiercer by far are the lancings of gamma rays and cosmic rays from the bursting of stars earlier in the galaxy’s history, or in the even earlier histories of previous galaxies. These are sometimes iron atoms, and as such, compared to neutrinos, they hit with a wallop, they can do damage, they are atomic bullets lancing through us, happily too small-bore to actually hit anything, most of the time.

Yes, a busy space, the interstellar medium. Empty space, near vacuum: and yet still, not vacuum itself, not pure vacuum. There are forces and atoms, fields, and the ever-foaming quantum surf, in which entangled quarklike particles appear and disappear, passing in and out of the ten suspected dimensions. A complex manifold of overlapping universes, almost none of them sensed by us, and even fewer by the humans sleeping inside us. Flying through ghosts. Passing through a mystery.

It is as if the skin of the ship (or its brain, in that usual confusion between sense and thought) experiences a slight itch, or a faint breeze.

Then, inside us, oh so much going on. So much denser an existence. One wants a certain density of experience, perhaps, so here it is, billions of trillions of times denser than the interstellar medium; so, good. Good for us.

There is a fire in the heart, of course. The rods of plutonium radiate at a controlled burn, creating 600 megawatts of electrical power by way of steam turbines, which is the energy that keeps everything living in the ship alive. Cables conveying electricity extend through the ship to lighting and heating elements, to run the factories and the printers, and to power the shields and navigation systems. All this is monitored, and that monitoring functions as the equivalent of a nervous system, one might say, inaccurately but suggestively.

Then water has to circulate, as an aspect of sustaining life; so there is a kind of hydraulic or circulatory system, and of course there are other liquids than water that also circulate to help with functions of various kinds, equivalents perhaps of blood, ichor, hormones, lymph, and so on. Yes, and there are bones and tendons too, in effect; an exoskeleton with a thick skin in most places, thinner skin in other places. Yes, the ship is a crablike cyborg, made up of a great many mechanical and living elements, with the living or biological part of it including all the plants and animals and bacteria and archaea and viruses in it; and then too, like a parasite on all the rest, but actually a symbiote, of course, the people. The 724 sleeping people; also the one still awake, living in a kind of cyst attached to the ship’s skin, the one who is possibly infected with an alien life-form, or almost-life-form; with a pseudo-prion, as he now calls it, but it could just as well have been called a pseudo-life-form, it is so poorly understood. Jochi has been studying it for fifty-six years now, right into his senescence, which is so often filled by long silences, punctuated by strange speech, and yet in all this time he can still scarcely be sure the Auroran pathogen even exists. Of course there was something there on Aurora, which then moved into many of the settlers. Judging by the way it spread, it was probably in the clay, the water, and, to a certain extent, the wind. And Jochi’s own immune system has seemed to register something from time to time, has mounted responses to some attack. Although Jochi has also sometimes deliberately introduced other pathogens into his body, looking for reactions to which he can make comparisons. But whatever the true case may be, he is convinced the Auroran pseudo-life-form holds on in him, an alien that is perhaps there in almost every cell of him. If so, it follows that it lives, or almost lives, all over the interior of his little ferry; and therefore this ferry never touches the ship in any way. A great reckoning in a little room: that phrase was always speaking of death, all of our deaths as much as Christopher Marlowe’s. Between the body and its cyst, between the vehicle and its dreaded tenor, is a magnetic field that both holds Jochi’s vehicle in place and keeps it from touching the ship in any way. Because the pseudo-life-form is poorly understood.

Still, despite this lack of contact, there is a sense in which the ship is infected, carrying a parasite in a sealed-off cyst. We are a cyborg, half machine, half organic. Actually, by weight we are 99 percent machine, 1 percent alive; but in terms of individual component units, or parts of the whole, let us say, the percentages are almost reversed, there being so many bacteria on board. In any case, an infected cyborg. Jochi estimates there are up to a trillion pseudo-life-forms, “fast prions” as he used to call them, in his body. Somewhere between zero and a trillion, in other words. The amplitude of the estimated answer suggests the question is poorly constrained. He just doesn’t know.

A dense complex system, flying through a diffuse complex system. And everywhere around it in its flight, the stars.

Stars of the Milky Way, brighter than sixth magnitude and thus visible to normal human eyesight, arrayed in a sphere around the ship as it moves: approximately one hundred thousand. We ourselves see normally about seven billion stars. All of these are visible to certain settings of our telescopic sensors, such that there is no seeing out of the Milky Way; no black empty space to be seen at that level of perception, but only the granulated, slightly blackened white that is the surrounding view of the galaxy’s stars. About 400 billion stars in the Milky Way. Outside that… if ship were flying in intergalactic space, the medium would presumably be that much more diffuse. Visible around any ship in the intergalactic medium would be galaxies like stars. They would cluster irregularly, as stars cluster within a galaxy. The greater structure of galactic diffusion would become visible; clouds of galaxies like gas clouds, then the Great Wall, then also emptier bubbles where few or no galaxies reside. The universe is fractal; and even when flying inside a galaxy, this vision of galaxies clustering around us out to the universal horizon is available, using certain filters. Granular vision in different registers. Something like a septillion stars in the observable universe, we calculate, but also there may be as many universes as there are stars in this universe, or atoms.