“What I don’t get, Professor,” said Ace, “Is how you can change some bits of history and not other bits.”
The Doctor looked up from where he was fussing around the hexagonal control console of the TARDIS, a questioning–if irritated–look on his features.
“Well… remember Terra Alpha?” Continued Ace. “Overthrowing Helen A, fermenting revolution, home by teatime?”
The Doctor stopped what he was doing, walked around the console to Ace’s side and leaned against it, smiling. “A rather grimly happy place, yes. Go on.”
“If we weren’t there, would that have happened?”
The Doctor pondered for a moment. “It’s difficult to say, even for me. These things do tend to get resolved, though, one way or the other… it’s almost like a universal constant: oppress sentient beings and get your just deserts. I rather think our presence sped up the process somewhat but for the sake of argument, let’s say if it weren’t for us, none of it would have happened.”
“Right. So Helen A continues killing people and it remains a nuthouse… but… say because it was such a nuthouse for so long, something really great happens. They create the U.N. or something.” Ace gestured randomly. “Or make the best-tasting pizza. But all that didn’t happen because we interfered and got rid of the old hag before it got worse.”
The Doctor winced slightly. “A little bluntly put, but all right. So what you’re asking is… Why it is that we can do all that and not, for example, stop Earth’s World War Two? Why do we interfere at all, in fact, when we could possibly be creating a worse situation–or even a situation that just isn’t as good?”
Ace thought for a moment. “Right. Yeah. Why? I mean, I realise that a lot of good things came out of the second World War, but maybe good things would come out of it anyway, if it never happened…”
“Such as your grandmother’s husband surviving the war, your mother having a father, perhaps meeting someone else than your own father–”
Ace looked shocked. “Stop it.”
The Doctor flapped his hands in a conciliatory manner. “Oh, Ace, I’m sorry. I didn’t mean to get personal but this is the sort of thing I mean. If Kathleen raised Audrey with her husband, with Audrey’s biological father… you may not even be here.”
Ace frowned, but accepted his apology. “All right, but that goes for Terra Alpha, too. A lot of things were changed by us.”
The Doctor looked thoughtfully at her for a moment, then nodded slowly. “All right… this is quite difficult to explain without going into quantum physics and time law. So we’ll do the next best thing–I’ll show you how it all works.”
Ace looked warily at him. “Is this going to have anything to do with evil from beyond time?”
The Doctor was already flicking switches and keying in coordinates. “No, no. I’ll have to make a small preparation stop first, though, so why don’t you go and freshen up? This won’t take a minute.” The time rotor paused, then started moving again as the TARDIS corrected its path and headed to a new destination.
* * *
Ace waited until the TARDIS landed before the Doctor shooed her away from the console room and back into the depths of the TARDIS. She used an antique cleansing system, all brass taps and gold-plated showerheads, instead of the sonic shower she had in the bathroom next to her room. She’d once asked the Doctor to replace the sonic shower with a ‘real’ one and he’d muttered about ‘perverting the course of human history’ and put it off.
When she was refreshed and munching on a chocolate-coated muesli bar she’d coaxed out of the food machine, she marched back to the console room to find the Doctor coming back in through the TARDIS’ outer doors. He was carrying a large rectangular case and a thick, coarse rug, which he deposited in a corner before turning to beam at her. “All set?” he asked.
Ace shrugged. “So where are we going, then?” she asked, randomly flicking a switch on the console and peering at the coordinates. The Doctor lightly slapped her hand and flicked the switch back. Then he leaned on the console and gazed at her.
“First, we are…” he paused, then turned a dial on the console. The lighting dimmed, impressively dramatic. “That’s better. First, we’re going to set some ground rules. This is particularly dangerous, so you are to stick with me at all times–and I do mean it, this time. Step where I step, look where I look. Do what I say at all times. Are we clear?”
Ace looked annoyed. “I’m not a child, Professor.”
His eyes softened. “No, you’re not. I’m just saying this now because it’s terribly important.” He closed the outer doors and set the TARDIS in motion. “We’re going to arrive slowly, because I’m now going to try and explain the different rules that apply.”
Ace watched as he activated a projector on the console, which created a 3D holographic image in the air above it. A single red line set against a starscape. “Time, in the broad sense, isn’t linear. For the ease of understanding, however, we’ll say that this red line is time, its leftmost end being the past, its rightmost end being the future and the middle being the present.” He activated a control, and a green line curved from the future into the past. “The green line represents time travel. Say a human being built a time machine in the year 3000. He uses it to go back in time to the year 2000. However… the act of his going back in time is, in fact, part of the entire timeline. He may set out to change the future, but that setting out, as well as that change, is and has always been part of how events unfold anyway. Is that understandable?”
Ace nodded impatiently. “I can work that out on my own. But we’re… well, you’re sort of out of time, out of the set events because you’re a Time Lord, right?”
The Doctor looked shifty. “Well… it’s much more complicated but broadly speaking, yes. A good way of putting it, in fact. Without going into difficult details, Time Lords can alter history without becoming part of the timeline. Whilst you’re with me, you can do the same. However, if you decided to go back to Earth or stay on in one time and place, then you become part of events once more.”
Ace glanced away briefly. “Right, go on.”
“Free will isn’t an illusion, however. Whilst timelines seem to be set from the perspective of a time traveller, just as the past seems to be set to someone living in the present or the future… there are a myriad of timelines which can become the future, depending on choices made and actions done. Personal timelines, general timelines… it’s all very messy.”
The Doctor looked pleased. “Yes, them too. Well done!”
Ace felt absurdly pleased with herself, and couldn’t help smiling. There was something warm about the Doctor’s approval. “Too good. Where do I sign up for the Time Lording?”
The Doctor rolled his eyes but he was smiling. “To continue… We could change things, yes. We could, forgive me for using this example, go back to 1942 and save Kathleen’s husband. We could certainly do that and change the course of history in that small way–though it may have major consequences. However…” the time rotor juddered to a stop and the Doctor nodded, his expression grim. “Ah, we’re here.”
He picked up the large rectangular case by its handle and, asking her to carry the rug, opened the outer doors. Together, they walked out of the TARDIS.