The Scientific Secrets of Doctor Who

by Simon Guerrier

  For most of us, this difference in time only affects us when we try to call someone in another country and must factor in that our mid-afternoon is their middle of the night, and so on. When we travel to other countries in another time zone, we must change the time on our watches to give local time.

  Knowing the difference between the local time – that is, the apparent position of the Sun and other stars in the sky from where we are – and the time back in Greenwich means we can calculate our longitude east or west of Greenwich. For example, if the Sun has just reached its highest position in the sky at our location but a watch set to Greenwich time is reading 1 p.m., we must be 15° west of Greenwich. It sounds simple in principle, but before it could be used in practice astronomers had to map the positions and motions of the Sun, Moon and stars with extreme precision, and clockmakers had to design and build clocks which would accurately keep Greenwich time – even on long and arduous sea voyages lasting many months.

  It still takes training and practice to make the necessary measurements, but knowing where on Earth you are is such a useful – even lifesaving – piece of information that for centuries people were willing to make the effort. Today, of course, anyone with a smartphone can use the satellites of the Global Positioning System to tell them their location. But this technology is in many ways a development of those early measurements of longitude using clocks and stars: the GPS satellites form an artificial constellation and computer software does all the difficult calculations for us, but the basic principles remain the same.

  Being able to find out where you are – your position in space – is something that we all find useful, but for time travellers like the Doctor and his companions finding out when you are – your position in time – is also a skill that can come in very handy. Surprisingly the stars could also prove very useful here, too. As the Earth spins on its axis, everything in the sky appears to move around us once every twenty-four hours – and in particular the position of the Sun relative to the horizon is what tells us whether it’s morning or afternoon, day or night. As the Moon orbits round the Earth, we see different portions of it lit up by the Sun. This 29.5-day cycle of lunar phases – new Moon, waxing crescent, Full Moon, waning crescent, and then back to new Moon – is the origin of our calendar system of months. The Earth also orbits the Sun, so that throughout the year the Sun appears to move once around the sky, relative to the background groupings – or ‘constellations’ – of stars. Days, months and years are therefore all astronomical measurements, marked out by the motions of the Earth and the apparent movements of the Moon and Sun in the sky. By understanding how their positions change, we can use the heavens as a giant clock, telling us hours, days and months.

  One thing that doesn’t seem to change is the constellations of stars. Night after night they appear to rise, move across the sky and set, but their familiar shapes – the Plough, Orion the Hunter, Taurus the Bull and dozens of others – are reassuringly constant. However this constancy is an illusion and if we compared their positions after fifty or a hundred years, we would see small changes as each individual star slowly shifted its position in the sky. This is because the Sun, along with every other star we can see, is orbiting round the centre of the Milky Way galaxy. It takes our Sun, and the entire Solar System with it, between 225 and 250 million years to travel once around the galaxy. The last time we were in this part of the Milky Way we’re in now, the dinosaurs had just evolved and the Earth had only one continent. The Sun has made this epic journey about eighteen times since it formed 4.5 billion years ago and will probably make another twenty orbits before it finally dies.

  Our galaxy is vast and, even moving at typical speeds of about 230 kilometres per second, the changes in the positions of the stars are barely noticeable in a human lifetime – at least to human eyes. But with instruments like the European Space Agency’s Gaia space telescope, astronomers are beginning to measure and track the motions of around a billion stars in the Milky Way. Using computer simulations we can fast-forward these motions millions of years into the future or rewind them into the past, making the night sky seethe and swirl like a swarm of bees as each star follows its own unique path through the spiral arms, clouds of gas and billions of other stars which make up our galaxy.

  The constellations which hung above Tyrannosaurus Rex and Velociraptor were not Orion or the Plough, and our own descendants will need to invent new names and stories to describe the patterns that the stars make in the unfamiliar skies of the distant future. Perhaps a time traveller with enough knowledge of galactic dynamics would be able to take one look up and know exactly when they had arrived in the Earth’s long journey through the Milky Way.

  We’ll talk about other ways we might work out the year in which we’d arrived in Earth’s history in Chapter 10, which would be useful for a time traveller. But in Doctor Who, the Doctor rarely needs his companions to deduce where and when the TARDIS lands. He can do that himself. For example, in The Time of Angels (2010), River checks the TARDIS controls for information while the Doctor just pokes his head out the door.

  * * *

  ‘We’re somewhere in the Garn Belt.

  There’s an atmosphere. Early indications suggest that—’

  ‘We’re on Alfava Metraxis, the seventh planet of the Dundra System. Oxygen-rich atmosphere, all toxins in the soft band, eleven hour day and chances of rain later.’

  River Song and the Eleventh Doctor, The Time of Angels (2010)

  * * *

  In fact, a companion’s skills and experience are unlikely ever to match the Doctor’s. We can leave flying the TARDIS – and fixing it when it goes wrong – largely to him. Instead, the biggest risk of travelling with the Doctor is what to do if we get separated from him – which happens a lot in the series. So the ‘right stuff’ required to be a companion means practical things like self-reliance, bravery, the ability to adapt quickly and improvise.

  But there’s more than that, too. Time travel may be commonplace in the universe of Doctor Who, but its consequences can still be very hard for his companions to deal with. When the Doctor first takes Rose Tyler into the future in The End of the World (2005), she finds all the aliens – and being able to understand their languages – a bit overwhelming. To help, the Doctor fixes Rose’s mobile phone so that she can call her mum, back in the distant past. For a moment, Rose is happy just to hear Jackie’s voice. But the moment the call is over, the truth hits her hard:

  * * *

  ‘That was five billion years ago – so she’s dead now.

  Five billion years later, my mum’s dead.’

  Rose Tyler, The End of the World (2005)

  * * *

  We’re repeatedly shown in Doctor Who the odd side effects of travelling in time. Rose doesn’t just travel to the future where her mum is dead but also – in Father’s Day (2005) – goes to her parents’ wedding in the 1980s and meets herself as a baby.

  In The Power of Three (2012), Amy and Rory know that the amount of time they’ve been travelling with the Doctor for doesn’t match the amount of time that has passed for their friends and family on Earth. Their friends don’t know that Amy and Rory travel in time, but we see that it still affects their relationships: Amy’s friend Laura isn’t sure about asking her to be a bridesmaid because Amy’s not always around. We don’t know if Amy makes Laura’s wedding, but we do know Amy and Rory end up back in time at the end of The Angels Take Manhattan (2012), separated from their friends and family for ever. How companions survive after they’ve travelled with the Doctor – how they return to ordinary life after all of time and space – is a worry, too.

  Companions have to be tough psychologically. To travel with the Doctor, they must ask questions and solve problems, but they have to be ready for answers that can be surprising and unsettling. They are often threatened with death and they often see people die. There are times when they can stop and help and save people, and there are times when they must walk away. It’s OK to be scared, it’s
OK to make mistakes, and it’s OK to be ordinary. What gives a companion the ‘right stuff’ is an open mind, being willing – even eager – to explore all the strangeness of time and space, to puzzle out how it works and fits together, to face the consequences of discovery.

  But that, after all, is what scientists do every day. Rather than a collection of facts, science is really an attitude – a way of looking and thinking about the world. It’s a quest for knowledge, no matter how counterintuitive or strange, with a readiness to accept – in the face of new evidence – that everything you thought you knew is wrong. That’s what makes science such a powerful tool for understanding the universe around us.

  In Battlefield (1989), the Seventh Doctor takes Ace with him when he visits UNIT, handing her an old security pass so she can get past the soldiers on guard. The pass is for Liz Shaw, the companion of the Third Doctor with degrees in physics and medicine. Ace – who we later learn couldn’t pass her school chemistry exams – is worried. But the Doctor reassures her: it’s not qualifications that matter but attitude.

  * * *

  ‘Who’s Elizabeth Shaw? I don’t even look like her.’

  ‘Oh, never mind. Just think like a physicist.’

  Ace and the Seventh Doctor, Battlefield (1989)

  * * *

  Here we are now, in the park. With the pram beside her and the little one asleep, Tilly Pilgrim is watching a father pushing a child on a swing. Up curves the swing, and then, because this is how swings work, down comes the swing, and then it comes back, then down, then up and the child opens his mouth to laugh…

  And then Tilly comes unstuck in time…

  A cold red Sun curves across a darkening sky in a great arc – rising, peaking, and plunging down again behind the horizon. A bare Moon rises and speeds on its path. Then the Sun again, and the Moon, and the Sun, and the Moon – never-ending, and all the time Tilly can hear the cries of the damned trapped in this hell-time. Months, it seems, pass – years, and the chorus of screaming is ceaseless.

  And then a single voice comes, rising steadily above the rest, breaking through…

  ‘Can you hear us? You must hear us! We are coming! Coming through…’

  And down comes the swing. And back and down and up and down and back and –

  ‘Hello,’ says the man now sitting beside her. ‘Your daydreams. They’re very disruptive. There should be a warning sign. Something of a nuisance for you, too, I should think.’

  The man is funny-looking, limbs awkward like a baby giraffe. Tilly owns a lot of giraffes these days – or, rather, the little one does – but the point is Tilly knows what giraffes look like when she sees one. And this man looks like one – a baby giraffe that is – or he would, if baby giraffes wore bow ties.

  ‘And tweed,’ Tilly says, and giggles.

  ‘Tweed?’

  ‘My daydreams.’

  ‘Your daydreams are tweed?’

  ‘Don’t be silly,’ says Tilly, and giggles again. Then the man looks at her with such compassion that she thinks she might start crying. ‘How do you know about my daydreams?’

  ‘Well, I could hardly miss them, could I? They almost knocked me off course!’

  ‘Off course? Well, of course!’ Tilly says gaily. Very little about her life makes sense at the moment – what with the daydreams that seem more real than everyday life, and the thinking that the world is ending, and the being unstuck in time – so why not something else? Why not a tweedy baby giraffe with a bow tie?

  He is looking at her now, intensely, and the urge to weep is very strong again. This man, she thinks, has seen whole worlds become unstuck. He has seen monstrosities, and he has judged, and – sometimes – he has forgiven. And Tilly – who doesn’t know what is to be done, but knows that something must be done and quickly – makes a decision.

  ‘Let’s go for a coffee,’ she says.

  The man with the bow tie stares at her in horror. ‘A coffee?’

  ‘A coffee!’ He looks around, enchanted, and his hands flap about, like a dodo’s wings might have done when failing to fly. ‘Me! Going for a coffee! In a café! Me!’

  ‘It’s nowhere special,’ Tilly says apologetically. ‘Just one of those chain ones.’ But the staff are nice and they don’t hurry her out, and the mums in the indie cafés are slim and blonde and judge.

  ‘Can I have one of those giant chocolate biscuits?’ says her companion.

  ‘You can have whatever you like. Your dollar—’

  ‘Ah.’ He fidgets. ‘Yes. You see, I don’t have any money.’

  Tilly sighs. ‘Two double espressos and a big bourbon biscuit, please,’ she says to the nice young woman at the counter. Bow-tie man, happy again, capers off to find a seat, and she adds, ‘Could you make one of those espressos decaffeinated?’

  ‘So,’ says the man-boy, after she’s wheeled the pram round and sat down opposite him, ‘These dreams.’ He’s not flapping or fidgeting now. ‘Serious business, dreams. Particularly ones that can knock a time machine off course.’

  The baby stirs, but rolls her head to the other side and goes back to sleep. ‘Time machine,’ Tilly says, meditatively.

  ‘Don’t worry about it,’ he urges. ‘Tell me about the dreams.’

  She ponders how to explain. ‘Have you ever read the Narnia books?’

  ‘Read them? I built the wardrobe!’

  ‘It’s a made-up wardrobe—’

  ‘Believe that, by all means, if it helps.’

  Tilly decides, sensibly, that this is the least of her worries. ‘The Pevensie children. They went into the wardrobe, and became kings and queens of Narnia, and reigned for years. Then they went on a hunt, and they chased the white hart through a waste land—’

  He is nodding. He knows the story. ‘And they fell out of the wardrobe no older than they were when they went in.’ He picks up a little packet of brown sugar from the table and twists it around between thumb and forefinger. All this nervous energy, Tilly thinks, could make you feel really rather tired, if you weren’t very tired already from the sleepless nights and the dream-filled days. ‘Is that what happens, Tilly? Do you fall into the wardrobe and become a queen of Narnia, and then fall out again no older than you were when you went in?’

  ‘I didn’t tell you my name.’

  ‘No, you didn’t. I’m the Doctor. There – equal footing. Is that what happens?’

  ‘Yes,’ Tilly says, with great relief. ‘That’s how it happens. How it’s always happened.’

  He’s very intent now. ‘They’ve not just started, then?’

  ‘No, I got them as a child…’

  The Most Beautiful Place in the World

  Here she is now, in her home away from home, back again in the magic land, the daydream land, the garden, the place where a child can roam safe and free. This is Middle-earth, this is Narnia, this is where the wild things are and the white flowers bloom at night. This is where colours are brighter, sounds sharper, and she is still young enough that she misses nothing, records all, remembers all.

  Here she quests, and explores, and wanders, and sometimes just sits by running water and watches it ripple over her toes. Here she becomes a hero, a captain, a navigator, a gardener, a king and a queen. Here she leads many long lives of adventure, and peace – and, later, love. But when she returns home, she is still on the bed, and the clock still shows the same time.

  And the places she visits are always various and new, and the people are generous and kind, and the summers are warm but not unbearable, and the winters are beautiful but not cruel, and spring is full of life, and autumn full of promise, and time, relentless time, is passing – and then, and then, and then…

  ‘And then?’

  ‘And then it… stopped.’

  ‘Why?’ says the Doctor, urgently. ‘What happened?’

  Tilly sighs. ‘I guess I fell out of the wardrobe,’ she says with regret.

  ‘So the dreams?’

  ‘Went away.’

  ‘Where did the
y go?’

  ‘Where did they go?’ Where do dreams go? ‘They were childhood stories,’ she says, as if that should be enough explanation. ‘Things I told myself to help me fall asleep.’

  Softly, the Doctor says, ‘I think we both know that they were something more than that. And still are.’

  Tilly thinks of the voice – the latest voice. We’re coming. Coming through… She drinks her coffee in one quick gulp. He has made short work of the big biscuit, she notices. ‘I grew up. There were exams, university…’

  The Doctor nods sagely. ‘Lipstick. Parties. Girls. And boys.’

  Tilly can’t help laughing. ‘Something like that, yes.’

  ‘So you became less open to the messages. You didn’t have the bandwidth. Busy time, being a teenager. Brain expanding. Going supernova. Learning about cause and effect and life and death and getting the first tiniest inkling that you’re not, in fact, going to live for ever.’ He’s getting excited now, and he wags his hands about, sending biscuit crumbs everywhere. ‘Big issues. Big deal. Needs a bigger brain. But even that bigger brain – it’s so full, all the time, too full, not enough room for everything any more—’

  Tilly holds up a hand to stop the flood. ‘Whoa there, mister!’

  ‘Doctor.’

  ‘Doctor-mister. Hold on a minute. Did you say bandwidth? Like some kind of receiver?’

  ‘Yes, yes, a receiver!’

  ‘You make me sound like a telephone! I’m not a receiver!’

  ‘No?’

  ‘No! I was the kind of child that had an overactive imagination. Daydreamed a lot. Probably read too much—’