The Scientific Secrets of Doctor Who

by Simon Guerrier

  ‘I’m a Time Lord. I’m the last of the Time Lords. They’re all gone. I’m the only survivor, I’m left travelling on my own, cos there’s no one else.’

  ‘There’s me.’

  ‘You’ve seen how dangerous it is. D’you want to go home?’

  ‘I don’t know. I want… Can you smell chips?’

  ‘Yeah.’

  ‘I want chips.’

  ‘Me, too.’

  The Ninth Doctor and Rose Tyler, The End of the World (2005)

  * * *

  Watching at home, we can’t smell those chips, but it’s a recognisable smell and one likely to spark warm, happy memories of times when we’ve had chips. Again, our memory evokes an emotional reaction. More than that, because chips seem normal and real, so does all this talk of the Time War, even though we don’t see it.

  We’ve talked in previous chapters about the different ways scientists can measure and test things, using ever more sophisticated technologies to make more accurate measurements. But there’s a basic problem: human beings don’t experience the universe directly. As we’ve already discussed, our brains are supplied with data by our five senses. We then process that data into something we think of as meaningful.

  That means our perception can be subjective – and our senses can be fooled. Television is a series of still images like photographs, run together at speed to make your brain think that it’s watching movement. Look closely at the TV screen and you’ll see the picture is made up of tiny blobs of just three colours: specific combinations of blue, green and red. At a distance, our brains can’t differentiate these separate blobs, so we see a seamless picture.

  Another good example is our sense of time passing. Explaining his theory of relativity, Einstein is said to have used the analogy that a minute spent doing something we don’t enjoy can feel like an hour, while an hour spent with someone we really like can feel like only a minute has passed. Of course, this has nothing to do with the physics of relativity, but Einstein was making the point that our experience of time is a slippery thing and one we shouldn’t take for granted. There’s a related phenomenon, where people who’ve been in accidents or faced great danger speak of time seeming to slow down.

  * * *

  ‘Let me tell you about scared. Your heart is beating so hard, I can feel it through your hands. There’s so much blood and oxygen pumping through your brain, it’s like rocket fuel. Right now, you could run faster and you could fight harder, you could jump higher than ever in your life. And you are so alert, it’s like you can slow down time. What’s wrong with scared? Scared is a superpower.’

  The Twelfth Doctor, Listen (2014)

  * * *

  Is it true that when we’re stressed our brains work faster, effectively meaning that we experience everything else around us passing more slowly? To find out, in 2007, the American neuroscientist David Eagleman conducted an experiment that was as brilliant and ridiculous as anything the Doctor might think of: he dropped people – including himself – off the top of a very tall building.

  The falling people were caught by a net, but the fall itself was still scary. Did that fear make people’s brains work faster? While they were falling, the people in the experiment had to look at a special wristwatch they’d been given to wear, on which two numbers were displayed. The numbers alternated very quickly – faster than could be read in normal conditions. The question was whether people could read the numbers clearly while they were falling and scared.

  The experiment showed that they couldn’t, which proved that stress doesn’t make the brain work more quickly – and doesn’t slow down time. But Eagleman had a second experiment, and after people had fallen and been caught in the net, he gave them a stopwatch. They were asked to let the stopwatch run for the same amount of time that they had fallen for. People who had watched the fall but not fallen themselves were also given stopwatches and asked to estimate the length in time of the fall. The results showed that people who had fallen thought about a third more time had passed than those who didn’t fall. The fallen people felt that time had passed more slowly as they fell, even though their brains hadn’t been working any more quickly.

  There are different theories about why that might be. In a stressful situation, our perception seems to focus on ways to escape or solve the problem facing us. We stop taking in everything else around us – so the world seems less busy and complex. That might affect our sense of time.

  Another idea – which might happen in tandem with the first – is that there’s a difference between how we experience time as it’s happening and how we look back at time that has passed. As we’ve seen, our emotions and sense of smell are linked to the way we make memories. Strong emotions seem to etch memories more strongly into our minds. A key way in which, looking back, we feel how much time has passed is through the number of new memories made in that period. Say we usually create a strong new memory once a day. In a stressful situation, we create several strong memories in a few hours. Looking back, it will feel like several days’ worth of time happened in those hours.

  If that is right, it explains why, as we get older, time seems to pass more quickly. Individual days still feel the same length, but it seems as if Christmas comes round faster than it used to. The reason would be that as we get older we experience fewer new things, we get into routines and maybe have better control of our emotions. All that means that we lay down fewer strong new memories, so when Christmas arrives we look back to the last one and feel little time has passed.

  The Doctor and his companions are constantly having new experiences and dangerous adventures – so perhaps they wouldn’t feel Christmas coming round any more quickly. More than that, they might be healthier, because our subjective sense of time has been linked to various diseases such as depression and dementia. There’s good evidence that having lots of new experiences and laying down new memories helps with ‘cognitive reserve’ – that is, the way the brain resists damage and these kinds of diseases.

  Our bodies also keep time in another way, called the circadian clock. We seem to unconsciously keep track of levels of daylight all the time. The suprachiasmatic nucleus of the brain uses this information to control a number of things, such as production of melatonin – a hormone that makes us sleepy. The hormone cortisol, which affects levels of blood sugar and so affects whether we feel hungry, also seems to be governed by this internal clock, as are body temperature and women’s menstrual hormones. In animals, hibernation seems to be controlled by the same inner clocks.

  Our inner clocks also synchronise our senses. If someone touches your foot and your shoulder at the same time, you feel both sensations at once – but the sensation in your foot has much further to travel to your brain than the sensation in your shoulder. It’s thought that your brain leaves a tiny amount of time between what’s happening and your perception of it, effectively a buffer that allows the sensation from your foot to catch up with the sensation from your shoulder. That buffer means the world as we experience it is always slightly behind the world as it is happening – so we are always living slightly in the past. It’s even thought that the taller you are – and the further sensations have to travel to reach your brain – the longer the delay you experience, so the more in the past you are living.

  It also seems that we continually use our senses to check our inner clocks are in sync with the world around us. There’s an experiment that gets you to press a button which turns on a light. You keep pressing the button, but the light starts coming on fractionally later – say by 200 milliseconds. You continue pressing the button long enough that your brain puts the two things in sync, then we stop the delay. Now you press the button again and the light comes on immediately – but your brain, synchronised to the tiny delay – makes you think the light came on before you pressed the button. It feels as if the light turning on has travelled backwards in time.

  Because our bodies depend on the workings of this inner clock, when that clock gets out of sync
it can make us feel very peculiar. If we travel a long distance round the Earth, we cross many time zones. If we travel relatively slowly – say, on a ship – our bodies can keep in sync with the changing time. But if we cross time zones more quickly – such as by flying in a jet plane – it can make us ill, with a condition called desynchronosis or ‘jet lag’.

  The Doctor’s companions don’t seem to experience jet lag when they travel in the TARDIS. In The Bells of Saint John (2013), the Doctor and Clara jump ahead a few hours as a weapon against their enemies.

  * * *

  ‘Why did we travel to the morning? What’s the point in that?’

  ‘Whoever’s after us spent the whole night looking for us. Are you tired?’

  ‘Yes.’

  ‘What? Then imagine how they feel.

  They came the long way round.’

  Clara Oswald and the Eleventh Doctor, The Bells of Saint John (2013)

  * * *

  Clara’s not tired because they’re jumped forward from night to day, but because she’s already had quite an adventure. If the jump in time caused jet lag, she’d be feeling sick. Perhaps the TARDIS compensates for jet lag somehow.

  We can get over jet lag in a few days as our inner clocks adjust to the time zone we’ve moved to. But people who regularly work or party into the night can be at risk of more serious harm. They might sleep longer into the next day, but their bodies’ sense of time will still be out of sync. It’s been shown that shift workers have a greater chance of heart disease, stomach illness and problems sleeping. What’s more, our inner clocks seem to explain seasonal affective disorder – a kind of depression that usually strikes in winter, when there is less daylight – and may be related to diseases including type 2 diabetes, obesity and cancer. It’s even thought that our inner clocks decide how long human beings can live for – as we’ll see in Chapter 14.

  How do you know what happened to you in the past? And how do you know that you know it? In Listen, the Doctor and Clara meet a small boy called Rupert Pink – who will grow up to be Clara’s boyfriend, Danny. Clara is worried about the consequences of the encounter.

  * * *

  ‘Will he remember any of that?’

  ‘Scrambled his memory. Gave him a big old dream about being Dan the soldier man.’

  Clara Oswald and the Twelfth Doctor, Listen (2014)

  * * *

  The suggestion is that Rupert won’t remember Clara and the Doctor explicitly, but something of their adventure together will remain with him – and shape his personality.

  There seem to be two kinds of long-term memory: explicit and implicit. Explicit memory is conscious and intentional: we remember that a new episode of Doctor Who will be on at a specific hour, and we remember to watch it. Implicit memory is different: we’re not conscious of the way that past experience affects our behaviour. When you tie your shoes or ride a bike, you do it without (consciously) thinking.

  In young children, the ability to make implicit memories develops before the explicit memory. Babies recognise things that make them feel safe or scared and develop responses when those things happen again.

  The possibility that memories that aren’t part of our conscious thoughts might still affect our behaviour has long intrigued doctors and scientists. In the late nineteenth century, Austrian neurologist Sigmund Freud proposed that shameful or traumatic memories that people hid from themselves might be the reason that they experienced mental health problems and unexplained physical symptoms. He argued that this process of repression made people unwell, and bringing such things to light through a new kind of treatment – psychoanalysis – could be helpful. Psychologists and neuroscientists have moved on from Freud’s theories, but they are still influential in clinical practice and in the way writers think about personality and memory, as we shall see shortly.

  A number of conditions can affect our memories. The general term for memory loss is ‘amnesia’. Memory loss is not uncommon clinically. It might be a short-lived process (for example, following mild brain injury), permanent as in the case of Henry Molaison, or progressive, in which case patients are said to have dementia. In many cases we can find anatomical damage that explains the memory loss, but sometimes there seems to be a psychological explanation.

  Some treatments for these conditions use the associative nature of memory. For example, Henry Molaison was able to modify some of the long-term memories he retained from before his operation to include new information – less creating new memories than adapting old ones.

  Something similar might be happening in The End of Time (2009–2010). In Journey’s End (2008), the Doctor saves the life of his companion Donna by removing her memories of him. But those memories are not destroyed – it seems he only removes her ability to access them. In The End of Time, when she sees people around her turning into copies of the Master, it reminds her of things she’s seen before. Her brain processes the new experience by comparing it to previous memories – and that need to associate new memories to old ones is strong enough to bring everything back.

  Importantly, our memories – what we learn and experience – make us who we are. In Chapter 7, we saw what the Doctor looks for in potential companions: they need to have the right attitude. As they travel in the TARDIS, he provides them with skills and experience, and makes them better people.

  Heartbreakingly, Wilfrid Mott says just that to the Doctor in Journey’s End, when Donna has lost all her memories.

  * * *

  ‘I had to wipe her mind completely. Every trace of me – or the TARDIS, anything we did together, anywhere we went – had to go.’

  ‘All those wonderful things she did …

  But she was better with you.’

  The Tenth Doctor and Wilfrid Mott, Journey’s End (2008)

  * * *

  In fact, the suggestion is that memories can be used to change how we behave in the future.

  Recent research has revealed some interesting quirks about implicit memory. So-called ‘priming’ involves tinkering with implicit memory in ways that will subsequently affect behaviour. For example, in the early 1970s, American psychologists David E. Meyer and Roger W. Schvaneveldt conducted an experiment where people were shown a series of groups of letters – some of the groups with letters in a random order, and others where the letters spelled out an everyday word. The speed at which people recognised the everyday words was recorded.

  It was found that people were faster at recognising the word ‘nurse’ if they had seen the word ‘doctor’ earlier in the series. This suggested that the word ‘doctor’ prepared or primed them to recognise associated words.

  Although the science of priming is still contested, the idea seems to have influenced Doctor Who. At the end of Listen, Clara meets and reassures a scared child who will apparently grow up to be the Doctor. She holds his ankle and talks to him soothingly, creating a memory – and entirely changing his life to come.

  * * *

  ‘Fear is like a companion. A constant companion, always there. But that’s OK, because fear can bring us together. Fear can bring you home. I’m going to leave you something, just so you’ll always remember, fear makes companions of us all.’

  Clara Oswald, Listen (2014)

  * * *

  The First Doctor will later (for him) quote the words ‘Fear makes companions of all of us’ to his new companions in the very first Doctor Who story, An Unearthly Child (1963) – and goes on to say that fear lives with another sensation: hope. Hope despite fear seems key to the Doctor’s character – and it might come from one brief childhood experience.

  Memory is not just something we have but something we do: encoding memories, storing them, recalling them and acting on them. Remove our memories and we become different people. In Into the Dalek (2014), we learn that Daleks shut off certain memories to extinguish any glimmer of kindness or compassion, making themselves more ruthless. The Doctor gives the Dalek back one of its memories – of a star being born – and the Dale
k feels a strong emotion, speaking of the star’s ‘beauty’.

  At the end of the story, the Dalek rejoins the other Daleks – but with ‘unfinished work’ to do. Because the Doctor changing its memory has changed this Dalek’s whole personality. It has switched sides, and we are left to wonder what damage it will wreak among the rest of the Dalek race. The Doctor has used memory and emotion as weapons against his worst enemies.

  But once, he and his people fought the Daleks using time…

  The universe convulsed. For a moment, time itself held its breath. Then it let it out again in a chaotic amalgam of past, present and future. Might-have-been and could-have-done crashed into what-if and never-was.

  Caught at the edge of the temporal wave, the TARDIS rode out the storm. The first the Doctor knew of it was when the ground dropped from under his feet and his head cracked into the console. When he woke a few moments later, he was lying on the floor. Until recently he’d had a mass of dark curly hair that might perhaps have cushioned the blow. But now his hair was cut short – like the soldier he resolutely refused to be in this most catastrophic of wars. The lights fizzed and flickered like an electric storm. The Cloister Bell sounded cracked and melancholy. He dragged himself back to his feet and surveyed the panels in front of him. Every warning light was blinking at him. Even several he was sure he’d never seen before.

  High above his head, the roof of the TARDIS had faded into a view of the contorted star systems as they folded in on themselves. Stars went nova; black holes collapsed; planets collided and spun away into oblivion. Several whole galaxies vanished from history – never having existed. The view and the readings from the instruments that were still working told him everything he needed to know.