Two Earths drop away below us. "This is going to be my last adventure," says Ed.
I look at him quizzically. "I'm going to Andromeda," he continues.
"To see it?"
For a while I say nothing. Then, "For how long?"
"Probably forever." Ed has this look in his eyes. He's dead serious. I try to think of more to say, but can't.
This is it, then. The last chapter of the Ed MacPherson story.
Below us, both Earths are replaced with darkness.
The law of gravitational potential states - provisionally - that when using a tunnel drive, the point in space from which you depart will have precisely the same gravitational potential as the point where you arrive. That means, if you leave low Earth orbit and depart for a distant star, you'll arrive just a short distance above its surface, and if your ship isn't properly shielded, you will get instantly burnt to death.
You have three alternate options. One is to jump to the star anyway and, in the fraction of a second before you or your ship begin to sustain damage, take enough sensor readings to identify an alternate target inside the same system which you can safely jump to, and immediately jump to it instead. This is risky and doesn't always work. The second is to identify such a target remotely. This is less risky, but also less likely to work; often, you're lucky to be able to identify a single planet, and that's if the system has any to begin with. The third, and by far the most tedious, is to invest a few hours or days climbing far enough out of your local gravity well that heat won't be a problem at your entry point.
We took the second option. Below us now, the floor of the entire universe as far as my primitive brain can figure out, is the night side of Epsilon Eridani B, a gas giant a tad smaller than Jupiter first observed from Earth way back in 2000. On the horizon ahead of me - how many thousands of miles ahead? - is a glimmer of orange. As I spot it, it begins to tilt upwards. B becomes a wall, dominating the view ahead of the ship, and the wafer-thin but growing orange slice of light becomes an arch "above" me.
Time passes as we accelerate across the night side towards the terminator and when we reach it, filters in the ship's main window cut in to reduce the rising Epsilon Eridani's brilliance from blinding to merely spectacular.
It was worth waiting for.
Ed gets down to hunting for signs of alien life. There's a lot of system to scan and a lot of scanners to scan it with.
"Hey, check this out," he says after a while, and puts on some extremely staticky music.
"Whitesnake. Very good."
"You don't understand. This is live from Earth, circa 1987."
"Yeah. And if we can hear it, so can the Eridanians. They can probably hear everything. Television, radio, satellite communications. Most likely they've been listening in for decades. Most likely they know an awful lot about us."
"Do you really think we can stop this war before it starts?"
"I've never been more sure of anything in my life," he replies.
"We still don't know who the Eridanians are. We still don't know why the war began."
"We'll find out."
We start at the innermost of system's eight planets. Epsilon Eridani One is a small but dense rocky world, with two moons, one slightly smaller than Luna, the other half that size. It whirls in uncomfortable heat, somewhere in the range between Mercury's measure and Venus'. There's a thin green atmosphere of chlorine, which makes this the first time I've ever seen a planet's natural colour clash with its own star.
The Ed Rocks isn't great at handling intense heat, so we lurk in the shadow behind the larger moon to observe the planet, constantly accelerating in a fifty-kilometre-circle to simulate gravity without leaving the shadow. I dread to think what Epsilon Eridani looks like from One's surface. Surface temperature is high enough to liquify most kinds of rock.
"It looks like we have radio activity," says Ed. "Faint, but definitely coherent. Listen..." He turns a switch and unpleasant static fills the cockpit. Then he fiddles with the tuner a bit. Some sort of pattern seems to emerge from the noise. It sounds strange. Like whale song in a tin can. Like a didgeridoo on helium. But the Human brain is the greatest pattern-spotting device in... well, on Earth... and there's no doubt. Behind the noise is signal. "That's an Eridanian radio broadcast."
"It's amazing! You can almost hear the language behind it."
Ed nods. Then frowns. "...What?"
"You can't tell what they're saying, but you can hear there's language behind it."
Puzzled: "They're a few hundred years ahead of us, technologically. Shouldn't they be encoding their transmissions by now? This sounds like... like regular, direct sound modulation. They could fit a thousand times more in this band. I mean, WE still do this... but... let me find another station." He fiddles. More noise comes through. Different texture. Maybe a different language. The same mouths, though. "It's all like this. All over the radio spectrum. It's just chatter. No television, no digital radio. And it's all so faint! It's almost drowned out by background noise from Earth..." He turns up the volume. Eridanian voices fill the ship, overlaid with human chatter from eleven years ago.
Ed gets it an instant before I do: "But these aren't just transmissions. These are their voices. They speak in radio. They're like gigantic living semi-liquid stone antennae and they speak to each other in radio. The same radio bands we use. But they speak faintly and we holler. Even at such an enormous distance we drown them out for half of every day and every day it gets louder. No wonder they went to war. That's the whole reason. They can't communicate. Interstellar noise pollution. And they've been watching the trends, they know that for the next eleven years it's going to build and build... But they're too big and heavy to go into space themselves, and besides that's not how they work." He pulls out a piece of paper and a pen and starts drawing rapidly. "They're intelligent but their intelligence is at right angles to ours - they barely recognise us as life. We're more like a natural force - destroying us is no more immoral for them than damming a river. They're patient and slow but some of them are very intelligent and despite their size many of them have really delicate skill. They sent unmanned ships to try and keep us quiet. The first wave... the first wave..." He scribbles madly. There's an outline taking shape on his paper.
"How do you know all that?"
Ed pushes buttons. The pure green image of the planet in the main window wobbles through various colours as he tries to find a waveband on which the chlorine atmosphere isn't opaque. Then it settles down, with the planet looking almost Earthlike apart from the colour scheme. Half of the visible expanse is taken up with jaggedy continents picked out in dark purple-blue, the rest, black oceans of molten metal and metal chlorides. Here and there across the land, there are tiny pinpricks of white light.
Ed leans forward and holds up his drawing, skewed at forty-five degrees so that the outlines of the continents match each other. He's drawn some vigorous little concentric circles at one point on a coast. On the screen, that location looks like a cluster of bright white and yellow pinpoints. A city. He's drawn a target map.
"How did you do that?"
I stare at him, and he stares at me like a man who just had the whole universe ripped out from under his feet.