While they may look the same, a Time Lord is very different to a human. Not only are there a few quirks of biology, but there are plenty of traits that separate the two races as well. A Time Lord has an innate connection with the ebb and flow of the universe: the term ‘Time Lord’ is not merely ceremonial. They can feel the turn of the universe and sometimes see the timelines of those they meet stretching out in front of them. The Doctor often seems distracted by things humans cannot perceive; his mind functions on a higher level, comprehending variables no one else can possibly fathom. Thus understanding time travel is easy for them... to make it easier for non time travellers, here's a bit of a primer:
Time is very much like a river, able to roll round most stones dropped into it without changing course too badly. In this way the careful traveller can go to the past and future without doing much damage, as long as they stay out of trouble. If you tread on a butterfly you won’t destroy the world as the universe does its best to ensure time develops along the right path. It basically ensures a different butterfly does what the one you stepped on was meant to do. Without a solid (albeit confusing) structure to spacetime the universe would fall apart, so the fabric of reality does its best to tidy up after you. Of course, no river survives long if you throw enough big stones into it, or dig up the banks. If you know the trail of events and influences of your actions in any time frame, you can do an awful lot of damage. A concerted attempt to change the proper order of events can succeed, if you know what you are doing. Temporal manipulation isn’t easy though. For instance, you might think killing Hitler would be enough to stop The Second World War.
However, the war began due to a complicated series of events enacted by many various individuals. So killing Hitler isn’t enough alone, in fact, you might not need to kill anyone at all. Perhaps getting England into a treaty with Germany before the invasion of Poland might do the trick. But then a vast AngloGerman alliance might crush most of Europe. As you can see, blundering about in time often does no good at all. Without an intrinsic instinct for the flow of time it is very hard to see the right ‘nudge points’ to get the best effects. It is also important when manipulating time to stick to the small stuff and play the long game. Major adjustments to history (such as the death of renowned historical figures) get noticed very quickly. Not only does the universe react badly to such blatant attempts, but so do the various races that govern time travel. The Time Lords came down hard on rogue agents who didn’t tread carefully. That is if the universe itself doesn’t edit the marauder from existence in self defence.
Having established that interference in temporal events is possible, you need to know the best place to do so. Any temporal manipulator must master the use of ripples and nexus points to stand a chance of success. Ripples are the side effects of interfering with time. No action happens without influencing the actions of others. Change one action and you change any further events that action influenced. Those actions in turn influence other actions, and so on. As you move further and further from the centre of such a disturbance, its influence might fade, but it could just as easily build into a cascade. This chain of actions that spread out from the spatial and temporal centre of the disturbance is like ripples on a pond after you throw a stone in it. Travellers must take care of the ripples their actions create on the pond of universal time. Their effects are hard to predict and often more far reaching than you expect. As with a stone, when the initial interference has sunk and been forgotten, the ripples might still continue. Many amateur interventionists are surprised at the damage they do when they focus only on the initial change to causality and fail to deal with the further consequences of their actions.
Luckily, not all places in time and space send out ripples in the same way. Some places are more important to the fundamental fabric of space-time. These places are referred to as nexus points. Both Earth and Gallifrey are good examples of powerful and important nexus points. Gallifrey’s history had such an impact on the universe that the Time Lords banned all interference in its timeline. Earth is important given the way humans have spread out to every corner of the galaxy. To change the history of the cradle of humanity would influence every world they ever touched.
While most time travellers have the sense to leave nexus points alone (it’s safer that way) they often become primary targets for temporal marauders. There will always be those who think they can interfere with time for personal gain and either control its effects or don’t care about the damage they do. Such beings are sadly in no shortage. Earth has become a battleground for alien invasion on countless occasions as changes to the timeline here can create galaxywide changes to causality. This is also due to Earth’s development being quite primitive compared to most time-aware cultures. It appears simple to manipulate such primitives to create far reaching temporal interference effects. However, their position as ‘knots’ in the weave of the fabric of space-time grants nexus points a kind of destiny. Such places seem to find heroes to defend them, and keep them safe. These heroes and those who inhabit such nexus points are bound to play a major part in the universe.
This all leads to the question of predestination. If you were actually responsible for a historical event, all you are doing is following a set course. Your life has been predetermined for you the moment you step into the time machine. So why bother going back in time at all? Firstly, you still don’t know what’s going to happen to you. Whether you are already fated to perform certain actions or not is unimportant. You are free to do as you please, knowing that everything you do has been sorted out by the universe without messing with history. If you are not actively trying to mess with time, you are probably OK. Secondly, it might be vital that you do, as you may be fated to stop some other temporal manipulation from happening.
It is possible to change the future if you work at it. Other time travellers might be working to pervert the universal timeline. Your successful plan to stop them could already be a matter of history, or it might not be. If time is altered, the universe might follow a different path. Alter history enough and no one might be able to fix the damage. That might have been the fate of the universe all along. You just never know what you’re meant to do, but does that mean you don’t try? If you told a soldier from either side of the Second World War what the outcome would be, do you think he’d fight any less? He knows what’s at stake, he can’t just trust fate to sort things out without him. Everyone has a part to play in the drama of the universe. In the case of time travellers, the universe simply has a lot more work for them to do.
When Sally Sparrow finally talks to the Doctor through a DVD extra, she was already predestined to say what she said. However, she was still able to ask the Doctor what she wanted to know as she didn’t know what she was predestined to do! It just so happened that whatever she wanted to know or would have thought to ask was ready to be answered by the Doctor. But it isn’t all fun; you can argue that occasionally predestination can still take control of your actions. Sally’s conversation with the Doctor ends with his telling her there is no more transcript, which he assumes means the Angels are coming. It is this that makes Sally check where the Angels are. Could Sally have talked longer with the Doctor if he hadn’t said that? Could the Angels have attacked earlier? They could have chosen to, but predestination implies they didn’t, and if you don’t know what you’re meant to do, how can you change it?
With time travellers going from the future to the past with alarming regularity, it is possible for them to even engineer predestination sequences on purpose. If the Doctor had wanted to use Sally Sparrow to deal with the Angels for no better reason than he didn’t want to get too close to them, he could have done so. However, working out the variables to create the right chain of events can often take a lot more time and energy than just doing the job yourself, though simple predestination sequences are easily possible and can be fun, if only to mess around with temporal physicists. For instance, you know your friend will spill his cup of tea. So you tell him not to worry that he’ll spill it, which causes him to fumble with the cup and to spill his tea anyway. Would he have still spilt it if you’d not told him it didn’t bother you? Is that a form of predestination or are you just messing with his head?
Temporal philosophers have wrestled with the problem of predestination for millennia. How do you know if your actions have been pre-planned and you are following a path you are unable to deviate from? If you are, then that just makes us all unthinking puppets of an uncaring universe. Mind you, that is a very ‘glass half empty’ way of looking at it. If you don’t know the intentions of the universe, it doesn’t matter if it is a plan or not. You still never know what is around the next corner, and what adventures might need you. near and far It is also important for a time traveller to be careful how far they travel in time. It is very tempting to go to the end of the universe, and maybe eat their picnic while watching suns fade away. You might also fancy a trip to gaze at the Big Bang and see the universe created.
Even the Time Lords never travelled to the end of existence. It isn’t a very good idea, for two reasons: firstly, these are momentous events, and interference in either might have dire consequences for the universe as a whole. The tiniest particle added to the Big Bang could cause the universe to form in a totally different way. The end of time is just as delicate, with whole species evolving into new forms or on the cusp of their universal destiny.
The second reason is simply for your own safety. These times are very, very dangerous indeed. Beings at the end of the universe might be more advanced than you, and decide to use you or your technology as some way to escape the final days. In the early days of the universe, strange and god-like entities, some that eat time itself, swim in the forming matter. These beings might drive you mad with a touch or destroy your timeship. Even with these beings gone the universe is still dangerous. The laws of physics themselves are still forming. You might arrive to find time travel is impossible due to the state of the universe, and these are not very pleasant or forgiving environments to be stuck in. In some cases your very existence might not function in reality, and it is a pain to be erased from existence the moment you step out of the door.
sideways in time If you can travel forwards and backwards in time, what happens if you go sideways? The answer is that you visit a timeline where different decisions have led to a different outcome for the world, an alternate universe. The theory of alternate universes suggests that every time you make a decision, a whole new world is created where the path you didn’t take is also followed through. If that decision was whether to have a bacon sandwich or a boiled egg for lunch, the world that is created wouldn’t be very different from the other reality. However, if the decision was whether or not America should have entered the Second World War, or whether Bill Gates should get involved in the computer market, the world may be very different indeed. Especially as each of these decisions creates ripples that flow out into the alternate world and offer new opportunities and tragedies to plenty of other people. For example, if America hadn’t entered the war, not only might Germany have conquered Europe, but all the American soldiers who died fighting would have lived. Who knows what these soldiers might have done with the lives the battlefield stole from them? The potential for them to change the world is vast. Alternate worlds are a playground of ‘what ifs’ filled with copies of everyone you know that are often slightly different. Visiting such places is a fascinating way to find out what you might have become if things had been just a little bit different. As such they are an incredible source of adventure and exploration. Especially as you won’t know what your alternative version has been up to until you investigate. Will you be mistaken for someone wanted for murder or treated like a president?
Before the Time War, the barriers between these dimensions were thin and a TARDIS could easily pass between them. However, the damage wrought by the Time War caused the universe to shut down such access in an attempt to limit the damage to reality. The walls between the worlds went from paper to stone as the universe tried to heal itself.
That is not to say getting to an alternative universe is impossible, it’s just that it isn’t a very good idea. There are still holes and tunnels to such places that failed to close and certain powerful machines might exist to force open a gateway. However, once you are there, getting back can often be an issue. The power systems of most devices will be slightly different, making it difficult to repair any damaged systems and get them working again. Given how hard it is to punch through the universe, and traverse the Void between, it is unlikely you’ll arrive without any damage to your timeship at all. While some places are paradises of peace and tranquillity (on some worlds even humans get things right) others are hostile and barren. You never know what you’ll find until you get there. Just imagine what the Earth might be like if the Doctor hadn’t been around to save it and you get the idea. Boiled and sold off to the Slitheen, a slave farm for the Sycorax or even the centre of a new Human/ Dalek empire. Donna discovered just how harsh a reality without the Doctor could be when she ‘Turned Right’. Sometimes the world is mostly the same – it just has more Zeppelins in it, and someone you once knew is now sporting an attractive eye-patch.
This travel to other worlds doesn’t only go one way. There may be alternate worlds that are actively developing such devices so they might invade other worlds, including ours, for their resources. After all, if you have run out of oil in your world, you know there are plenty of other Earths you could visit to get more.
Most people mark the ‘present’ as the point they step into a timeship. Sure, they may lose a couple of days, and have adventures that last a week or two while returning a few hours later. However, the year is still usually the same and an experienced guide can use the Blinovitch Limitation Effect to steer their companions along a more linear timeline with everyone else. Although you can’t revisit your own timeline very easily you can ‘bookmark’ your last visit to a place and return there after you left. Time travel isn’t an exact science, however, and the Doctor himself once promised to return in five minutes and ended up twelve years in the future of a very annoyed Ms. Pond