SHALL I TELL YOU THE PROBLEM WITH TIME TRAVEL?

 

ADAM ROBERTS

 

Adam Roberts was born in the year 3,061,965 and has time-travelled back to London, England, to the early years of the extraordinarily backward and primitive 21^st century, in order to convey a message of the utmost importance to humankind. That message is hidden somewhere in one of his dozen SF novels or several dozen SF short stories. You have to read them all to find it.

 

Zero

 

This is no simulation. The friction-screaming fills the sky. An iceberg as big as the sun is up there, and then it is bigger than the sun, getting huger with terrifying rapidity. This is happening to a world that had, up to this moment, known no noise at all save the swishing of insects through tropical air; or the snoring of surf on the beach. But this, now, is the biggest shout ever heard. Apocalyptic panic. And the asteroid falls further, superheating the atmosphere around it, the outer layer of ice subliming away in a glorious windsock of red and orange and black, down and down, until this world ends.

But – stop. Wait a minute. This hasn’t anything to do with anything. Disregard this. There’s no asteroid, and there never was. He doesn’t know whether he is going on or coming back. Which is it, forward or backward? Let’s go to

 

One

 

A City. A pleasant, well-ordered city, houses and factories and hospitals, built on a delta through which seven rivers flow to the sea. The megalosaurs have long gone, and the swamps have long since dried up, and the mega-forests have sunk underground, the massive trunks taller than ships’ masts, sinking slowly under the surface and through the sticky medium, down, to be transformed into something rich and strange, to blacks and purples, to settle as coal brittle as coral. The world that the asteroid ended is stone now: stone bones and stone shells, scattered through the earth’s crust. Imagine a capricious god playing at an enormous game of Easter-egg-hunt, hiding the treasures in the bizarrest places. Except there is no god, it is chance that scattered the petrified confetti under the soil in this manner.

So, yes, here we are – in a city. It is a splendid morning in August, the sky as clear as a healthy cornea, bright as fresh ice, hot as baked bread. Sunlight is flashing up in sheets from the sea.

The city is several miles across, from the foothills, from the suburbs inland and the factories to the sea into which the seven rivers flare and empty. The seven rivers all branch from one great stream that rushes down from the northern mountains. The city abuts the sea to the south, docks and warehouses fringing the coastline, and beyond it the island-rich Inland Sea. The mountains run round the three remaining sides of the delta, iced with snow at their peaks, really lovely-looking. Really beautiful. To stand in the central area, where most of the shops are, and look over the low-roofs to the horizon, and note the way the light touches the mountains – it makes the soul feel clean. This is Japan and it is 1945.

 

Two

 

Move along, move on, and so, to another city; and this one very different. This city stretches sixty miles across, from the two-dozen spacious estates and the clusters of large houses in the east, nearer the sea, to the more closely-packed blocks, dorms, factories of the west. The city is threaded through with many freeways, tarmac the colour of moondust, all alive with traffic and curving and broad as Saturn’s wings. Sweep further west, drive through the bulk of the town, to where the buildings lose height and spaces open up between them, and away further into the sand-coloured waste, and here – a mountain. And at its base a perfectly sheared and cut block of green. This is the lawn, maintained by automated systems. The style of the white marble buildings is utopian; for this is the closest we come to utopia in this sublunary world – a spacious and well-funded research facility. This is the Bonneville Particle Acceleration Laboratory. Let’s step inside this temple of science. Through the roof (it presents us with no obstacle), down from the height to the polished floor, and the shoes of Professor Hermann Bradley clakclaking along that surface.

He steps through into a room and his beaming, grinning, smiling, happy-o jolly-o face shouts to the world: “We’ve done it, we’ve cracked it – thirteen seconds!”

The room is full of people, and they all rise up as one at this news, cheering and whooping. And there is much rejoicing. People are leaping up from their seats and knocking over their cups of cold coffee, spilling the inky stuff all over their papers, and they don’t care. Thirteen seconds!

 

Three

 

So, here, clearly, this narrative is in the business of zipping rapidly forward through time. That much is obvious. Some stories are like that: the skipping stone kisses the surface of the water and reels away again, touches the sea and leaps, and so on until momentum is all bled away by the friction. That’s the kind of tale we’re dealing with. So another little skip, through time, not far this time – three small years, in fact. Hardly a hop. And here’s our old friend Professor Bradley, a little thinner, a little less well-supplied with head hair. There’s a meeting going on, and the whole of Professor Bradley’s career is in the balance.

Four people, two men and two women, are sitting in chairs, arranged in a U shape. Bradley is sitting in the middle. One of the women has just said, “three years, and trillions of dollars in funding…” but now she has let the sentence trail away in an accusing tone.

The mood of this meeting is sombre. Whatever happened to ‘thirteen seconds’? Whatever happened to the celebration that single datum occasioned?

Bradley says: “Shall I tell you the problem with Time Travel?”

“No need for you to patronise us, Professor,” says one of the others.

“It’s the metaphor,” says Bradley, quickly, not wanting to be interrupted, “of travel. Time is not space. You can’t wander around in it like a landscape.”

“There are five people in this room,” says one of the women. “Must I tell you how many PhDs there are in this room? It’s a prime number larger than five.”

“That’s just dindy-dandy!” says Bradley, aggressively.

“If you think the point of your being here is to gloss over your experimental failings…”

“OK!” barks Bradley. “Alright! OK! Alright!”

You can tell from this that the mood of the meeting is hostile. You can imagine why: trillions of dollars!

“Last month you reported seventeen seconds.”

“That’s right,” says Bradley. “And let’s not underestimate the real achievement in the…”

“Three years ago you came to us with thirteen seconds. You have worked three years to find those four seconds – and you’re still at least fifteen seconds short! How am I to see this as an improvement?”

“We have,” says Bradley, “cracked it. I am convinced that we have cracked it. I’m more than convinced. I’m certain, absolutely certain. One more test will prove the matter. One more!”

“You have run out of test slots, Professor. Run out! This means there are no more test slots. Do you understand? You have conducted over two thousand tests so far! You have conducted so many experiments that you have literally run out of slots –”

“Shall I tell you the problem,” says one of the men, waggishly, “with using up all your test slots?”

Bradley hasn’t got time for this. Urgently, he says: “The Tungayika…”

“Let us not,” interrupts one of the men, “let us not rehearse all the reasons why Tungayika would be – a terrible idea.”

“A terrible idea!” repeats one of the women.

“Terrible,” agrees the third.

“But of all the remaining possibilities,” urges Bradley, “it’s the best we have. Entertain this idea, I ask you. Please: entertain the idea. What if I really am only one more trial away from perfecting the technology?”

“Tungayika is a good half century further back than any test you’ve conducted.”

“It’s not the distance,” says Bradley, rubbing his eyes, as if he’s been over this a million times. Million, billion, trillion: these numbers are all friends of his. “It’s not a question of distance. Time isn’t like space. That’s what I’m saying. It’s an energy sine.”

“It is the distance,” retorted one of the men. “Not in terms of reaching the target, maybe not, but definitely in controlling the experiment via such a long temporal lag. And quite apart from anything else, nobody really knows what happened at Tungayika…”

Bradley seizes on this. You know what? He thinks this is his trump card. “That’s right!” he says, leaping up, actually bouncing up from his chair. He’s an energetic and impetuous fellow, is Bradley. “That’s the best reason why you should authorise the drop! Think of the metrics we’ll get back! We’re guaranteed at least seventeen seconds there. But in fact I’m certain we’ve finally got the containment right; we’ll be there right up to the proper moment. And that means … we’ll be able to see what it was that created such a big bang, back there in 1908. Solving that mystery is, well, icing on the… icing on the…”

“You’re playing with real things here, Brad,” says one of the men. “This is no game. Real people, real lives.”

Professor Bradley nods, and lowers his gaze, but this could be the problem – right there. Because you know what? Professor Bradley doesn’t really think he is playing with real things. Many years and scores of drops have reinforced his belief that reality can’t be played with. History is as it is; time paradoxes are harder to generate than kai-chi muons. Tungayika in Siberia in 1908 is further away from his conscience than anything imaginable. It was such a sparsely populated area! And anyway, the asteroid wiped it out! And anyway, that event has already happened. The board is worried about killing people, but all the people he might kill are all already long dead! None of what he does is real.

That’s the crucial one, really. That last one.

“It’s one more drop,” says Bradley. “Just that. Just one more! Then we’ll be able to go back to Capitol Hill with a fully-working time travel insertion protocol! Think of it!”

“Brad...”

“This one chance to turn all the frustration around to victory – the chance to get a return on all that money!”

“But Professor Notkin says that…”

At this much-hated name Professor Bradley positively arches his back. Like a cat! Really – like a furious, hissing feline! “Come on Rosie,” he cries. “Don’t bait me, Rosie!”

“Brad, now, listen, Notkin is…”

“– after my bloody job,” cried Professor Bradley, rolling his hands in an agitated dumb-show. “She’s after my Lab. She can’t have it. If I didn’t have to keep pouring my energies into combating her conspiracies against me –”

“Oh,” says Rosie, in a disappointed voice.

“Conspiracies is too strong,” agrees another.

“Some might consider it actionable,” opines a third.

“Agh!” yells Bradley, in the sheerest of sheer annoyance.

There is an embarrassed pause.

“Come now,” says Rosie, in a placating tone. “Notkin is a good scientist. There’s no need to get so worked-up about office politics. You can’t blame Notkin for being ambitious. Being ambitious is not a crime.”

“She has been undermining me for eighteen months now. She sells you on this pipe dream of remote viewing…”

“At least it doesn’t involve shit being blown up,” snaps one of the men.

And once again there is an awkward silence.

“Give me a break,” growls Bradley. “Patrick, you of all people –”

“I’m not kidding, Brad,’ says Patrick. ‘The bandwidth may be small, but with Notkin’s system…”

“... which she stole from my work…”

“... we get real data, and – and – and nothing blows up.”

Everybody falls silent. After a short while, Rosie says: “Look, Brad, we’re not out to get you. We’re really not. We’re not trying to replace you with Notkin. But you have to give us something to work with. Give us a result that’s more than seventeen seconds.”

“Then give me Tunguska,” says Bradley.

 

Four

 

We’ve come a long way, from the asteroid that killed the dinosaurs to Japan in 1945, and then via diminishing leaps to the present. From that heated meeting we need to use the magic time-travel machine called ‘story’ to step forward only two more months. Hardly any time at all. And here we are, right now.

Bradley is in a corridor inside his own lab and trying to get in, but his way is being blocked by three people. One of them is a policeman. The policeman looks kind-of embarrassed, but he’s there, and he’s resting his palm on the back of the grip of his holstered gun. Of the other two people one is Professor Notkin, aforementioned; and the other is Rosie – Roseanna Chan, senior liaison, perhaps the most objectively powerful person (in terms of political power) anywhere on the mountain.

Bradley says: “Crimes against humanity?” He says this several times. “Crimes against humanity? Crimes against humanity?” Then, “I thought that was a joke. Rosie,” he says, turning to her. “You’re going to let Notkin hand me to the police for crimes against humanity?”

“I’m afraid my hands are tied,” says Rosie, looking blank. Blank is her version of looking uncomfortable. “Maybe if Tunguska had –”

“She sabotaged Tunguska!” cries Brad, pointing a finger at Notkin. “She sabotaged it to get my job, to take my lab, to…”

“Calm yourself,” advises the policeman.

“There’s no need for a scene,” Notkin agrees, blandly.

“It does you no good,” says Rosie.

“C’mon, Rosie! You know how she’s been plotting for years to unseat me! I taught her everything she knows, and this is how she repays me?”

“You’ve taught me a lot, Brad,” says Professor Notkin. “I’ll always be grateful.”

Brad’s eyes do that bulgy-outy thing, as if they are filled with a metallic gel and Notkin is a massively powerful electromagnet. Words temporarily fail him.

“Time to come away, sir,” says the policeman. “Leave these people to do their work.”

“It’s not their work!” Bradley complains. “It’s my work!”

“You are under arrest,” the policeman reminds him.

“Ah!” says Brad, as if the idea has just occurred to him. “And what about the statute of limitations, eh? There is such a thing as a statute of limitations, even on murder.”

“But not,” said Rosie, as gently as she can, “for crimes against humanity. That’s why I’m afraid the officer here has got to take you in. But I’m certain it’s a temporary thing. It’ll only be a few days in jail until we find a judge prepared to bail you.”

“Bail me on a charge of crimes against humanity?” boggles Brad.

“It is an unusual case, yes,” says Rosie. “We all realise that.”

“Too right it is. These people were all dead already! These people were all long dead already! How you can murder somebody who’s already dead? Try and peg me with the guilt of these people when they’re already…”

“Dead, yes, and long ago,” says Notkin. “But dead because of you.” And for the first time there is, as the phrase goes, steel in her voice. You see now how she might have moved herself in only four years from grad student to Head of the Bonneville Particle Acceleration Laboratory.

Bradley is blustery, and he can do no better than repeat himself. He’s lost. It’s over for him. “They died before I was even born!”

“It’ll be interesting to see what the court makes of that defence,” Notkin notes, “Hey! Don’t punish me! The people I killed are already dead!”

“I am not a murderer,” says Brad.

“Let’s not –” says the policeman.

“This is bull,” says Brad. “I flat don’t believe this.”

“I’m afraid that Professor Notkin’s hunch has been proved,” says Rosie. “Do you think we’d be acting like this otherwise? I’m afraid it’s been looked into. There have been literally – literally – hundreds of federal agents and specialists looking into it. And it’s fair to say that there have been… ructions. Oh, some pre-tty ma-jor ructions. At the highest levels.”

“Just because a bunch of dead people are dead?”

“Not that! Well, obviously, that” says Rosie, “But the White House is more worried by the thought that – oh, come on Brad!” All one word: cmnbrad! uttered with the force of exasperation. “Our national defence is still predicated on nuclear deterrence, after all. We’ve still got thousands of missiles with nuclear warheads. It’s a shock to discover that firing them at a target would have no more effect than…” and she searches for an analogy, before falling back (she is a scientist, after all) on the literal truth “… no more effect than dropping eight tons of inert metal. There’s some high-level rushing around on that account, I don’t mind telling you. There are some chickens deprived of their heads in the corridors of power, I don’t mind telling you.”

“All that nuclear physics, all the stuff I learned as a student – the basis of nuclear power stations,” Brad splutters. “I refuse to believe it’s wrong.”

“It’s not wholly wrong, of course. But it turns out – wrong in one important regard.”

“Crazy!”

“Simply not explosive,” says Rosie. “Nuclear tech will fuse of course, and go fissionable of course, but only slowly. It’ll work in a nuclear pile. It just won’t explode over Hiroshima. It’s a tough lump to swallow, but swallow it you’d better. It’s the truth. The defence chiefs of staff are having to swallow that none of our nuclear warheads are actually explosive. That’s a big swallow for them. Those early bombs sent our physics a bit skewy. It might even be, you know, comical, if it weren’t so serious. If the implications weren’t so serious. Look, I’ll send the research work to your phone. I’m sure they’ll let you keep your phone in jail. You can read up on it. In actual fact, you know what? They took a regular warhead up to the Mojave last week and tried to explode it, and nothing happened.”

“One damp squib,” said Brad. But he sounded tired. Maybe the fight was finally going out of him.

“I’m afraid not. I’m afraid it’s true of all our warheads. None of them work, which is to say; none of them will explode. The same is true of the Chinese nukes, and the Russian ones, and the Indonesian ones – turns out the technology just doesn’t work. I mean, you can’t blame those last-century scientists. They did their chalkboard calculations, and they figured the bomb would blow, and when the bomb really did blow it seemed to confirm their calculations. So they didn’t worry too much about the more abstruse implications of the equations.”

“And how easy it is,” says Notkin, “to get one’s calculations wrong. Wouldn’t you say, Professor?” She may be forgiven this snide interjection. She’s suffered under Bradley’s cyclotropic eccentricities and incompetence for many years. And it’s her facility now.

“And when Hiroshima, and Nagasaki, and the subsequent nuclear tests seemed to confirm…” Rosie says. “But the horrible truth is that although those military leaders thought they were dropping those bombs and killing those people, they didn’t. You did it. You didn’t realise that this was what you were doing, but it was. The responsibility is yours. And since…”

And, suddenly, Brad is running. He is running as fast as his lanky legs will propel him, and the policeman is shouting “Stop or I’ll shoot!” He has finally unholstered his pistol. But Rosie stops him. “There’s no need to shoot,” she says. “There’s no way out of here. It’s a closed facility.”

Is she right, though? It is a closed facility, yes. But is there no way out?

What do you think?

Bradley runs, and runs. It’s been his facility for many years, and there are things about which not even the ambitious Professor Notkin knows.

Like what?

Like this capsule, in this room, wired up with the full power the facility can provide.

Previous drops have propelled a capsule no larger than a human thumb, wrapped about in shielding and cladding designed to protect it. But size isn’t actually a constraint, since time (it turns out) is not topographic in the way space is. It preserves angles, and an analogue of velocity; but not mass, or dimension, or, and to quote the great Algerian theoretical temporicist El-Dur les êtres de l’hyperespace sont susceptibles de définitions précises comme ceux de l’espace ordinaire, et si nous ne pouvons les répresenter nous pouvons les concevoir et… – well, anyway. The point is that there’s no reason, given enough energy, why a larger capsule might not be sent back. No reason at all. And you must understand this about Professor Bradley: he really really believes he’s cracked the containment field problem. He thinks the Tunguska mess-up was deliberate sabotage by the envious, ambitious, scheming Professor Notkin. He’s sure that he’ll be able to shoot himself back – and stabilize – and polarise – and get away. And what’s the alternative? Prison is the alternative. Crimes against humanity? – execution, like a Nuremberg villain? Ignominy, and a destroyed reputation, and his beloved technology thrown on the scrapheap? Or (this is what he is thinking) or: one final throw of the dice, one eucatastrophic twist in the story to turn failure into triumph, to vindicate everything he has done. A personal one way mission, backwards in time, simultaneously freeing him from captivity and proving the worth of his invention!

It’s no choice at all, really, for Professor Bradley. It’s exactly consonant with his impetuous personality; his ressentiment, his chafing restlessness. His fundamental incaution. He’s in the room, and he fits a metal chairback snugly under the door handle.

His phone comes to life in his breast pocket. The ringtone is ‘Rain’ by The Beatles. A fumble with a trembling thumb, and the device is turned off.

Professor Bradley powers up the generators, and climbs into the padded innards of his own experimental capsule, and he pulls the lid down on top of him.

Crimes against humanity? Or? Maybe beat the rap with one flick of this –

 

Three

 

And we’re off!

There’s almost nothing to see from the tiny porthole in the capsule. There’s not even really a seat to sit down on, just a little shelf to rest his narrow buttocks. But once the switch is flicked there’s a whomp and a whoosh and Brad’s head cracks against the ceiling of the capsule. A painful collision. Before he knows it he’s back resting on the little shelf, trying to peer out of the fogged up porthole and rubbing his head. Why did he bounce upwards when he accelerated backwards? He ought not to have moved at all; time, after all, is not space. But there is a trembling thrum to the capsule, as if time travel involves some kind of friction, or something. He can’t think. But it hardly matters. It hardly matters now. The switch has been thrown.

The view outside the capsule is not of a smooth backward-running movie. It’s a strobey series of discontinuities, frozen moments that hold for second, or sometimes more, of subjective time and then jerk into a prior arrangement. Very strange. It hurts Bradley’s eyes to watch.

The capsule is three months back. This is the time of his meeting with the suits, before the Tunguska debacle. It was at this time that Gupta, who worked directly for Notkin, came to his boss and said: “I’ve been looking at the underlining metrics from the drops, and something real screwy is going on with the numbers.”

It was at this time that Notkin (by no means a fool) began to wonder: but if the physics for the A-bomb was so misguided, then where did all that energy come from to flatten the city? And All those nuclear tests – that explosive energy must have come from somewhere! And what if the delta fold-up function that Brad included in his equations in fact follows an exponential rather than a sequential logic?

So many people killed! Of course that had never been Brad’s intent. Don’t you think he should be judged on his intentions? He had the best of intentions. He personally wouldn’t so much as pull a puppy’s tail, consciously. He’s a considerate and –

Too late! We’ve gone back past that moment.

 

Two

 

When now? We’ve jarred backwards a number of years before. This was the time of the first successful test: the probe lasting thirteen seconds of shielded life in the earlier time frame before exploding so violently. It was a frabjous day when that news was broached. On that day Brad drank two thirds of a bottle of champagne and, unused to the excess of such a gesture, was sick in a waste bin. You see, it was possible to shield the probe, even if only for a temporary period, when it –

No, we’re earlier than that now. Hurtling backwards the whole time.

This was when Brad was giving his introductory lecture to the new recruits. These were all brilliant minds, but all of them ignorant of the business of time travel. The whole discipline was classified. The basic equations were classified. The government would hardly spend so many billions on a project and leave it flapping vulnerable in the public breeze. So the students sit expectantly. Notkin is there, looking much younger and plumper and with eager eyes; all twelve of them have eager eyes.

Bradley says: “Shall I tell you the problem with Time Travel?”

And they listen.

“You need to stop thinking of it as travel,” says Bradley. “It’s not like wandering around a landscape. When you put an object from our time into another time frame, it’s like bringing matter and anti-matter together. It’s actually very much like that; the matter of your probe” (he holds up the thumb-sized plasmetal object) “is of a radically temporally distinct sort to the matter of your surrounding environment – the air, the ground on which it finds itself, the water in the atmosphere. They mutually annihilate and release energy. Boom!”

The students are wide-eyed and attentive.

“That would be bad news for the chrononaut,” says Brad, walking round to the front of the desk and leaning himself, rakishly, up against it. He is half-distracted – or no, a third-distracted, no more – by the eyes of that plump graduate student there, in the front row. Very striking. Attractive. He was not a man with a wide experience of women, but something about her gaze appealed to him. “Our chrononaut would step out of the door of his time machine into the world of 1850 and, boom! In fact he wouldn’t even get the chance to open the door. The material out of which his time capsule was made would react as soon as it appeared. Boom! How big a boom?”

So he calls up the white board, and as a group they go through the numbers, with Brad leading them, to show how big a boom. And it is big. It’s high explosive big. And as they do this, as he nudges their naïf misunderstandings in the right direction, and pushes the correct equations through the mass of variables, Brad thinks: she’s bright as well as pretty. He starts to daydream, idly, about whether this young new-PhD might be interested in –

“So how do we solve it, professor?” asks one of the other students.

Snap out of it, Brad! “That’s what you are all here to work on,” he booms. “We know what we need to do. We need to shield the probe,” and he holds up the probe again, “so that, once it’s inserted in the previous time slot it lasts longer than a microsecond. And then we need to develop the means of temporally polarising its matter. Given a long enough period – thirty seconds should do it – we ought, theoretically, be able to align the matter of the probe with the local grain of time travel. And once we’ve done that it can slot into the new environment non-explosively. Once we’ve cracked that problem… then actual, real time travel becomes a possibility.”

He grins; they grin. The world is all before them.

“One problem,” he tells them, “is in finding places to test our probe. You see, the early probes are likely to fail; we have to factor that in. And when they fail they’re going to go big boom-boom.” He simpers, and pushes his glasses back up the bridge of his nose. “The past is a different country, and we don’t want to go dropping random dynamite bombs on it hither and yon.”

“Because of the sanctity of the time lines, professor?” asks one of the students.

“Because of the risk of killing people. But there’s a way to avoid that danger.”

What way?

No, we’re slinking back further and further.

 

One

 

The 1940s. This is the moment of Hiroshima. What better place to hide an exploding device from the future than inside a nuclear blast? The time-locals are hardly going to notice it there, are they? Drop it at that place, at precisely that time. You’ll recover metrics that let you know how well the shielding is holding up, how long it would have lasted for – and then, bang: vaporised. No chance of futuristic technology falling into 1940s hands. No chance of being noticed. No grandfather paradox. Oh it’s an ideal solution.

One of the first things the team learn is that their theory is wrong. The device explodes not with high-explosive force, but with a more concentrated and devastating power. But it’s still small beer compared with the force of ten thousand suns that the atomic bombs unleash.

They test, and probe. They drop their devices into Hiroshima and Nagasaki. There were 477 nuclear tests in the period from 1945-1970, and they can camouflage their work inside any one of them. Each time they inch a little closer to perfecting the technology, drawing out the power of the shielding, giving more time for the polarisation to take effect.

Eventually, of course, they’re going to run out of nuclear explosions in which to hide their experiments. But by then they’ll have perfected the technology. By then. And if they have not, then they’ll have to find other historical explosions. That asteroid strike in Siberia in 1908 – you know the one. That’s always a fall-back.

It’ll be a long time before Notkin realises that the delta fold-up function that Professor Bradley included in his equations in fact follows an exponential rather than a sequential logic. Before she realises that the brown-paper-and-vinegar science of the Manhattan project, stuck with 1940s technology and assumptions, was simply not in the position to develop a working nuclear device. That the exponential factor in the equations, multiplied by the length of time through which the device travels, rubbing up a potent form of energetic friction, will produce an explosion of… precisely A-bomb dimensions. And that the later tests, with more sophisticated shields, would yield precisely the larger megatonnage of the test explosions into which they were dropped. That, in fact…

Missed it. Brad has shot backwards. He’s now earlier than Hiroshima, and is getting more before by the minute.

Frankly, he’s lost control. His grasp of the math has been wrong from an early stage, and he’s massively overestimated the amount of energy he needs to place this much larger device back to the right time. (He was thinking the 1970s). There’s an inverse scale on increasing math; but a straightforward exponential on the amount of energy you accumulate as you –

There he goes

Gone.

Before gone.

 

Zero

 

The deeper in time you sink, the more temporal static you build up. On the other hand, imagine an asteroid capable of causing mass extinction. That would have to be a whopper. But there never was such a large irregular polygon of ice and rock falling out of the highest high. You don’t believe me? Fair enough. I tell you how we can solve it: go back there and see for ourselves. Imagine the time traveller, his capsule popping out and crashing into the foliage. It lands on its back, tumbles on its top, rolls on its back, and the chrononaut can see out through his porthole. He wipes the condensation away with his arm. There are weird contortions of green and black, and he recognises them straight away for foliage. He can see two things. Past the leaves, out in the wetland a grazing diplodocus raises its head, its long neck straightening upwards like a pointing arm. The other, of course, is the number seventeen on his inner display turning, second by second, into sixteen, and so into fifteen, and – well, I daresay you know how to count backwards just as well as you know how to count forwards.