“By 2100 we probably need to aim for economic equivalence between Earth and space. I can’t hazard what size of economy this implies. Some say we may need as many as a billion people out there. We can figure it out later.

“These are targets, not prophecy. We may not achieve them; if we don’t try, we certainly won’t. My point is that we’ve sat around with our thumbs up our butts for too long. If we start now, we may just make it. If we leave it any longer, we may not have a planet to launch our spaceships from.”

“And,” he said, “in the end, have faith.”

In who? You?

Malenfant smiled.

His speech was well rehearsed, and it almost convinced him. But Cornelius’ Carter stuff nagged away at the back of his head. Was all this stuff, the exploitation of the Solar System for profit, really to be his destiny? Or — something else, something he couldn’t yet glimpse?

He felt his pulse race at the prospect.

Behind him, the softscreen’s software-generated images gently morphed into a shot of a Big Dumb Booster, real hardware sitting on the pad, a pillar of heavy engineering wreathed in vapor under a burning blue sky, a spaceship ready for launch.

Damn if he couldn’t see some glistening eyes out there, shining in the transmitted desert light. “This is a live image,” he said. “We’re ramping up for our first smoke test. People, this is

just the beginning. I’m going places. Come aboard.”

He waited for the applause. It came.

Emma Stoney:

It only took a week before Dan had designed and set up his first message-from-the-future experiment, at a place called the National Radio Astronomy Observatory in West Virginia. Emma was relieved that the funding required was modest, comparatively anyhow, and that Malenfant was able to pull strings to get his way without, as far as she could tell, any visible damage to the company.

Translation: nobody had found out yet what the hell they were doing.

Weeks went by, and the experiment produced nothing useful. Malenfant shuttled between Vegas, the Mojave, and West Virginia.

After a month of trying to convince Malenfant to come back to work, Emma cleared her diary and caught a flight to West Virginia.

She had a Bootstrap driver take her out to the radio observatory. She arrived at midnight.

The National Radio Astronomy Observatory proved to be set in a leafy valley surrounded by forest-clad hills. In the cloudless October sky a sliver of Moon floated among the stars.

As her eyes dark-adapted Emma made out a cluster of upturned dishes, each cluttered with spidery receiving equipment. The dishes seemed to glow, silver and white, as they peered up hopefully into an impenetrable, infinite sky. Occasionally one of the dishes would move on its fragile-looking stand, with a grind of heavy equipment, at the obscure command of one of the observers in the low, cheap-looking buildings. She wondered how many of the researchers here were now working for Bootstrap or for Eschatology — in either case, presumably, funded by Malenfant’s money.

She was taken to a grassy area where half a dozen folding lawn chairs had been set up. Malenfant, Dan Ystebo, and Cornelius Taine were working their way through a couple of six-packs. All of them were bundled up against the chill.

Dan, crumpled and slightly drunk, looked as if he hadn’t changed his T-shirt since Florida. Cornelius wasn’t drinking. He was wearing his customary designer suit, neat and seamless; somehow he seemed sealed off from this environment: green hills and silence and stately nature.

Malenfant was pacing, restless, his footprints dark against the dew on the grass.

She sighed. Malenfant, in this obsessive mood, took some management. Well, she’d expected this to take some time.

She sat down gingerly on a spare chair and accepted a beer. “I should have brought a heavier coat.”

Dan said sleepily, “After the first six-pack you don’t notice the cold.”

“So what have you picked up from our silver-suited descendants?”

Cornelius shook his head. “We didn’t expect success so easily. We just had to eliminate the most obvious possibility.”

She glanced around. “These are radio telescopes. Right? You’re expecting to pick up back-to-the-future messages by radio waves?”

“We’re trying to build a Feynman radio here, Emma,” Dan said.

“Feynman? As in Richard Feynman?”

Malenfant was smiling. “Turns out,” he said, “there’s a loophole in the laws of physics.”

Cornelius held up his hands. “Look, suppose you jiggle an atom to produce a radio wave. We have equations that tell us how the wave travels. But the equations always have two solutions.”

“Two?”

Dan scratched his belly and yawned. “Like taking a square root. Suppose you have a square lawn, nine square yards in area. How long is the side?”

“Three yards,” she said promptly. “Because three is root nine.”

“Okay. But nine has another square root.”

“Minus three,” she said. “I know. But that doesn’t count. You can’t have a lawn with a side of minus three yards. It makes no physical sense.”

Dan nodded. “In the same way the electromagnetism equations always have two solutions. One, like the positive root, describes the waves we’re familiar with, traveling into the future, that arrive at a receiver after they left the transmitter. We call those retarded waves. But there’s also another solution, like the negative root—”

“Describing waves arriving from the future, I suppose.”

“Well, yes. What we call advanced waves.”

Cornelius said, “It’s perfectly good physics, Ms. Stoney. Many physical laws are time-symmetric. Run them forward, and you see an atom emitting a photon. Run them backward, and you see the photon hitting the atom.”

“Which is where Feynman comes in,” Dan said. “Feynman supposed the outgoing radiation is absorbed by matter, gas clouds, out there in the universe. The gas is disturbed, and gives off advanced waves of its own. The energy of all those little sources travels back in time to the receiver. And you get interference. One wave canceling another. All the secondary advanced waves cancel out the original advanced wave at the transmitter. And all their energy goes into the retarded wave.”

“It’s kind of beautiful,” Malenfant said. “You have to imagine all these ghostly wave echoes traveling backward and forward in time, perfectly synchronized, all working together to mimic an ordinary radio wave.”

Emma had an unwelcome image of atoms sparsely spread through some dark, dismal future, somehow emitting photons in a mysterious choreography, and those photons converging on Earth, gathering in strength, until they fell to the ground here and now, around her.

“The problem is,” Cornelius said gently, “Feynman’s argument, if you think about it, rests on assumptions about the distribution of matter in the future of the universe. You have to suppose that every photon leaving our transmitters will be absorbed by matter somewhere — maybe in billions of years from now. But what if that isn’t true? The universe isn’t some cloud of gas. It’s lumpy, and it’s expanding. And it seems to be getting more transparent.”

“We thought it was possible,” Dan said, “that not all the advanced waves cancel out perfectly. Hence all this. We use the radio dishes here to send millisecond-pulse microwave radiation into space. Then we vary the rig: we send out pulses into a deadend absorber. And we monitor the power output. Remember the advanced waves are supposed to contribute to the energy of the retarded wave, by Feynman’s theory. If the universe isn ‘t a perfect absorber—”

“Then there would be a difference in the two cases,” Emma said.

“Yeah. We ought to see a variation, a millisecond wiggle, when we beam into space, because the echo effect isn’t perfect. And we hope to detect any message in those returning advanced echoes — if somebody downstream has figured out a way to modify them.