across the lumpy ground towards them. She slammed one end of the log down into the soft soil with a heavy thud, next to the last log, and Liam began to lash it into their wall.
‘I have a detailed record of the explosion. The number and density of tachyon particles that we were exposed to in 2015 and the number and density of tachyon particles that emerged here alongside ourselves.’
Liam looked at her and shrugged. ‘Assume I’m a child that knows nothing, Becks.’
She looked at him and he thought he caught her rolling her eyes at his stupidity: a gesture the AI must have learned from Sal back when it was computer-bound and its visual world was what it picked up from the one webcam.
‘Tachyon particles decay at a constant rate. That is why it takes greater amounts of energy to beam a signal further into the past.’
Liam tugged hard on the vine rope, cinching the knot tightly. ‘I get that. So, if these particles die out at a steady rate, that means
…?’
‘I am able to calculate how many particles decayed and, from that, determine how far in time we were sent.’
He grinned. ‘Really? You can do that?’
Becks looked up and tried mimicking his uneven smile. ‘I have the processing power to do this.’
‘And we’ll know exactly when we are?’
‘To an accuracy level of one thousandth of a per cent.’
Liam shook his head in wonder. ‘Jay-zus, that metal brain of yours is a bloody marvel, so it is!’
She seemed pleased with that. ‘Is that a compliment, Liam O’Connor?’
He punched her arm lightly. ‘Of course it is! Don’t know what I’d do without you.’
Her gaze drifted off across the clearing for a moment then back at him. ‘Thank you.’
He finished lashing the log and waited for her to pick up another and slam it down heavily beside the last one.
‘So what? We’ll actually know what day we arrived in the past? Even what time?’
‘Negative. I am unable to give that precise a calculation.’
‘OK. We’ll know to the nearest week or something?’
She shook her head.
‘The nearest month?’
‘Negative.’
‘Year?’
‘I can calculate to the nearest thousand years.’
‘ What? ’
‘I can calculate our current time down to the nearest — ’
He cut her off. ‘I heard you the first time. But… but that’s no good to us, is it? I mean, even if we could somehow get a message to the future and tell them which thousandth year we’re in, finding us here would be like trying to find a needle in a haystack!’ He slumped down against the wall. ‘If they tried opening a window at the same time every day for every year for a thousand years that’d be… that’d be…’
‘Three hundred and sixty-five thousand attempts,’ said Becks. ‘Add another two hundred and fifty attempts for leap years.’
‘Right! That many. Jeeeez, they’d never find us!’
She squatted down on her haunches beside him. ‘You are correct. It is extremely unlikely,’ she confirmed.
‘So that’s it, then?’ he said, sagging. The moment of believing they might have the beginnings of a way out was gone now, leaving him feeling even more hopeless than before. ‘We’re stuck here.’
‘Until my six-month mission timer reaches — ’
‘Yes, yes… I know. Then you’ve got to do what you’ve got to do.’
A hand reached out and gently grasped his arm. ‘I am sorry, Liam O’Connor. It does not make me happy to think of terminating these humans. Particularly you.’
He sighed. ‘Well… I s’pose that counts for something,’ he muttered. ‘Thanks.’
They watched as the others finally arrived with the log, and between them heaved it on to the ground. Whitmore wiped sweat from his forehead and recovered his breath. ‘Good God, I’m beat. Roughly how many more of these logs do you think you’re going to need to finish that?’
Becks turned and eyed the wall for a moment. ‘Seventy-nine.’
He puffed out his cheeks. ‘Seventy-nine? You sure?’
She nodded. ‘I am sure.’
‘Right,’ Whitmore puffed. ‘Right, come on then, you lot,’ he said to the others. ‘Back to work.’
Liam and Becks watched them go. ‘It would be possible for the field office to narrow down the number of candidate windows,’ said Becks.
‘What?’
‘They do not need to try opening three hundred and sixty-five thousand, two hundred and fifty windows. I am certain the AI back in the field office would make the same recommendation.’
‘Same recommendation? What?’
‘A density probe. They could attempt a brief scan of each day. Any scans that returned a varying density signal warning would indicate movement of some object at that location. It is possible they would consider density warning signals as best-case candidates.’
He looked at her. She was right. A routine protocol before opening a window, to make sure they weren’t going to get mangled up with somebody else. ‘Do you remember exactly where we appeared on this clearing?’
She nodded. ‘I have the exact geo-coordinates logged in my database.’ She pointed across the ground towards a cluster of ferns. ‘You appeared there. Fifty-one feet, seven and three-quarter inches from this location.’
‘Then — ’ Liam looked at the spot — ‘we’d need to stand someone right there… flapping their arms around or something, right?’
‘Correct. But it is unlikely the field office will be making probe sweeps this far back in time.’
Liam felt himself sagging again. Another dashed ray of hope. He balled a fist with frustration. ‘This time- travel stuff is nonsense. Would it be so hard for the agency to come up with some beamy signal thing we could send back to them?’
‘In theory it would be possible. But it would require an enormous amount of energy and of course time displacement machinery, and a sophisticated enough computer system to target where to aim a — ’
He raised a hand to shush her. ‘Becks?’
Her grey eyes locked on him obediently.
‘Please, shut up.’
‘Affirmative.’
He stood, stretching an aching back. ‘Ah, sod this!’ Then he suddenly snapped, slamming his fist against the log wall. The palisade vibrated slightly with the soft creak of stretched vine-rope.
‘Ouch!’ he muttered, and sucked on grazed knuckles. ‘That hurt.’
She tilted her head, curious. ‘Then why did you do that?’
‘Ugh… will you not be quiet?’
CHAPTER 32
65 million years BC, jungle
Several of the new creatures were standing in the shallows of the raging river, frothing white water tumbling noisily around their legs. They all held long sticks in their hands and seemed to be studying the water intently, keeping motionless for long periods then finally, inexplicably, lashing out with their sticks.
Broken Claw turned to the others crouching a few yards away, watching these creatures with fascination. He
