Читать книгу Time - Stephen Baxter - Страница 25

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 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?’

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

‘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 which 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, travelling 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 cancelling 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 travelling 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.’

Dan said, ‘We thought it was possible 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 dead-end 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.

‘We pick cloudless nights, and we aim out of the plane of the Galaxy, so we miss everything we can see. We figure that only one per cent of the power will be absorbed by the atmosphere, and only three per cent by the Galaxy environment. The rest ought to make it – spreading out, ever more thinly – to intergalactic space.’

Cornelius said, ‘Of course we can be sure that whatever message we do receive will be meaningful to us.’ He looked around; his skin seemed to glow in the starlight. ‘I mean, to the four of us, personally. For they know we are sitting here, planning this.’

Emma shivered again. ‘And did you find anything?’

‘Not to a part in a billion,’ said Cornelius.

There was silence, save for a distant wind rustling ink-black trees.

Emma found she had been holding her breath. She let it out gently. Of course not, Emma. What did you expect?

‘Crying shame,’ said Dan Ystebo, and he reached for another beer. ‘Of course experiments like this have been run before. You can find them in the literature. Schmidt in 1980. Partridge, Newman a few years earlier. Always negative … Which is why,’ he said slowly, ‘we’re considering other options.’

Emma said, ‘What other options?’

Cornelius said, ‘We must use something else – something that isn’t absorbed so easily as photons. A long mean free path length. Neutrinos.’

‘The spinning ghosts.’ Dan belched, and took a pull at his beer. ‘Nothing absorbs neutrinos.’

Emma frowned, only vaguely aware what a neutrino was. ‘So how do you make a neutrino transmitter? Is it expensive?’

Cornelius laughed. ‘You could say that.’ He counted the ways on his hands. ‘You set off a new Big Bang. You spark a supernova explosion. You turn a massive nuclear power plant on and off. You create a high-energy collision in a particle accelerator …’

Malenfant nodded. ‘Emma, I was going to tell you. I need you to find me an accelerator.’

Enough, she thought.

Emma stood and drew Malenfant aside. ‘Malenfant, face it. You’re being spun a line by Cornelius here, who has nothing to show you, nothing but shithead arguments based on weird statistics and games with techno toys. He’s spinning some kind of schizoid web, and he’s drawing you into it. It has to stop here before –’

He snapped, ‘If something goes wrong in the cockpit you don’t give up. You try something else. And then another thing. Again and again until you find something that works. Have a little faith, Emma.’ Emma opened her mouth, but he had already turned back to Dan Ystebo. ‘Now tell me how we detect these damn neutrons.’

‘Neutrinos, Malenfant …’

Cornelius leaned over to Emma. ‘The Wheeler-Feynman stuff may seem spooky to you. It seems spooky to me: the idea of radio waves passing back and forth through time … But it’s actually fundamental to our reality.

‘Why is there a direction to time at all? Why does the future feel different from the past? Some of us believe it’s because the universe is not symmetrical. At one end there is the Big Bang, a point of infinite compression. And at the other there is the endless expansion, infinite dilution. They couldn’t be more different.

‘We can figure out the structure to the universe by making observations, expressing it in such terms. But what difference does it make to an electron? How does it “know” that the forward-in-time radio waves are the “correct” ones to emit?

‘Maybe it’s because of those back-in-time echoes. Perhaps an electron can tell where it is in time – and which way it’s facing. And that’s how come the forward-in-time waves are the ones that make sense.

‘All this is analogy and anthropomorphism. Of course electrons don’t “know” anything. I could say, more formally, that the Wheeler-Feynman theory provides a way for the boundary conditions of the universe to impose a selection effect on retarded waves. But that would just be blinding you with science; and we wouldn’t want that, would we?’ He was smiling, his teeth white. He was toying with her, she realized.

Malenfant and Ystebo talked on, slightly drunk, eager. It seemed to Emma that their voices rose up into the sky, small and meaningless, and far above the stars wheeled, unconcerned.