The Scientific Secrets of Doctor Who

by Simon Guerrier

  That means we also know a little about what some of these planets might be like. There are ‘hot Jupiters’ – huge planets that orbit very close to their stars. It’s thought there could be planets made of carbon – perhaps like the diamond planet in Midnight (2008). And there seem to be planets like Earth.

  * * *

  ‘The Doctor won’t tolerate anyone deliberately playing havoc with his favourite planet.’

  The Master (about the Sixth Doctor), The Mark of the Rani (1985)

  * * *

  As we’ve learnt about other planets, we’ve also learnt about our own. We’ve not (yet) found life anywhere else in the universe, so what makes Earth so special?

  The Earth has lots of features that make it good for life. It has had a stable orbit for billions of years, which the Moon – proportionately large compared to other planets’ moons – helps regulate. We have a ready supply of energy from the Sun. Our magnetic field protects the planet from high energy particles that can be harmful to life. Earth is rich in carbon – as the Doctor tells Sarah in The Hand of Fear (1976), we are carbon-based life forms. The planet is big enough that its gravity keeps hold of its atmosphere, which keeps Earth nicely warm and allows us to breathe.

  With all these things going for it, it’s no wonder so many alien races (in Doctor Who) want to conquer Earth. But there’s something else, too.

  We know that oxygen isn’t essential for life as we’ve found microorganisms living on Earth that don’t need it. But there’s one thing all life we know of depends on: liquid water. Oceans make up seventy per cent of the Earth’s surface.

  For water to be in liquid form, a planet needs to be just the right distance from its sun. Too close and the water evaporates, while too far away and the water freezes. We call the right distance the ‘habitable zone’. About one in five of the planets Kepler has found fit this category. Kepler has only looked in a small region of space but, from what it has found, scientists think there might be as many as 40 billion Earth-like planets in just our galaxy. These planets could have liquid water on them, and that means they could have life.

  Is there life on these planets? Venus is in the habitable zone around our Sun, but its thick clouds of carbon dioxide make it extremely hot. Could life still exist there anyway? At the moment, we simply don’t know. As yet, we haven’t found any.

  What might alien life be like? In Doctor Who, we’ve met all kinds of strange life forms – fish people, butterfly people, slug people, rock people, gas people, water people, even viruses that can talk and people who exist in only two dimensions. In reality, life on Earth is extremely varied and diverse. Anything seems possible. In fact, the chances are that alien life will turn out to be something we haven’t even thought of.

  Think about that. Discovering the first alien life would mean we’re not alone in the universe. But it could also mean we have to redefine what life actually is.

  All we have to do is find it. And that means us getting out into space…

  * * *

  The Solar System according to Doctor Who

  • The Sun

  • Mercury

  • Venus – has metal seas (Marco Polo (1964)), flowers (The Wheel in Space (1968)), spearmint (The Shakespeare Code (2007)) and a creature called a Shanghorn (The Green Death (1973)). The Doctor is skilled in Venusian aikido, first seen in Inferno (1970).

  • Earth – the Doctor’s favourite planet.

  • Mars – the Doctor visits in The Waters of Mars (2009). Indigenous species include the Ice Warriors and the Flood. The Osirans also built at least one pyramid on Mars in the time of the ancient Egyptians (Pyramids of Mars (1975)).

  • Unnamed ‘fifth’ planet – the home planet of the alien Fendahl was time-looped by the Time Lords, possibly creating the asteroid belt. The Doctor says it was 107 million miles out (from Earth?) and broke up 12 million years ago (Image of the Fendahl (1978)).

  • Jupiter – British astronaut Guy Crayford is rescued by the Kraals while trapped in orbit around Jupiter (The Android Invasion (1975)). At some point in the future, the ‘planet’ of gold, Neo Phobos, moves into orbit around Jupiter as one of its moons and is renamed ‘Voga’ (Revenge of the Cybermen (1975)).

  • Saturn – the Doctor is infected by a talking virus while on Saturn’s moon, Titan (The Invisible Enemy (1977). It seems Titan is destroyed at the end of the story.

  • Uranus – the only source of the rare mineral taranium, used to build a time destructor (The Daleks’ Master Plan (1965–1966).

  • Neptune

  • Pluto – the Doctor calls it a planet when he visits in The Sun Makers (1977). One of its inhabitants, Mandrell, doesn’t believe there is life on any other planets.

  • Mondas – Earth’s long-lost twin planet drifted ‘to the edge of space’ before returning in 1986 – and exploding (The Tenth Planet (1966)).

  • Planet 14 – used as a base by the Cybermen in The Invasion (1968) – it’s not stated that Planet 14 is in the Solar System, but since the Cybermen come from the tenth planet (Mondas), it is possible they’ve colonised other, outer worlds.

  • Cassius – according to K-9 in The Sun Makers, Pluto was thought to be the ‘outermost body’ of the Solar System until the discovery of Cassius.

  * * *

  It was like this every time they landed recently: the Doctor, whizzing his scarf around his neck and jamming his hat atop his curly mop of hair, would throw caution to the wind, fling open the doors and charge out into the sunlight like an excited child.

  It was almost inevitable, really, that he’d sniff out the first sign of trouble, and then mire them both in it. Sarah had come to expect nothing less. This, she realised, was his modus operandi, his idea of having fun. She, on the other hand, wasn’t quite so convinced.

  There was no discussing it, though. Each time she’d tried to raise the issue, suggesting even a preparatory glance at the scanner before hurtling headlong into… whatever, he would just nod sagely and say, ‘Yes, I see precisely what you mean. Terrible business. You’d better have another jelly baby,’ before handing her the paper bag and carrying on as if the conversation was over.

  This time had been no exception. He’d bustled them out of the TARDIS in an unnecessary hurry, urged her on into the strange wooded glade, and marched them straight into oncoming danger.

  Still, Sarah had to admit – even she hadn’t been expecting a rabid, mutant sheep.

  Presently, they were crouched behind a bush while the Doctor tried to keep the thing distracted with the trailing end of his scarf. Sarah peered at it through the foliage. It was the strangest sheep she had ever seen – if it could even be called a sheep. It was overgrown (at least twice the size of a normal sheep) and clearly carnivorous (she could tell this from the way it had tried to bite her calves as they ran). It had wild, flitting eyes, and elongated canines that protruded over its bottom lip. Its wool coat was wiry and matted with dried blood that Sarah suspected wasn’t the sheep’s. It snorted in frustration and made another lunge for the Doctor’s scarf.

  ‘Remember I told you that, besides Earth, oak trees didn’t grow anywhere else in the galaxy?’ Tentatively, so as not to attract the attention of the sheep, the Doctor patted the bough of a nearby tree. It was barely broader than his hand, yet still towered far above their heads, its uppermost branches disappearing into a canopy of green.

  Sarah, exasperated, nodded in the affirmative. ‘Yes. This was just before we were shot at by a gang of homicidal androids, if I remember correctly.’

  He seemed to ignore her qualification. ‘Well, I was wrong.’ He beamed at her encouragingly. ‘They grow here, too. Wherever here is.’ He tugged absentmindedly on his scarf, and the sheep gave a ferocious growl. ‘Watch out, I think he’s grumpy with us.’

  ‘These are not oak trees,’ said Sarah. ‘Look at them. They’re all tall and spindly.’

  ‘Ah, but then, so would you be if you’d spent your formative years in a place like this. It’s all about gravit
y, you see. Don’t you feel a little lighter?’

  Sarah thought about this for a moment. ‘Well, yes, I suppose I do. But what’s that got to do wi—’ she stopped abruptly at the sight of the sheep, which had followed the Doctor’s scarf around to their side of the bush and was now preparing to launch another attack. Ribbons of saliva dripped from its open jaws. It looked positively monstrous. ‘Um… Doctor…’

  A horn blared suddenly, somewhere in the near vicinity, and the wooden shaft of a spear came whistling through the air and struck the earth a few inches from the Doctor’s left boot, burying its tip in the loam. Sarah stifled a scream.

  The sheep, terrified by this sudden incursion, dropped the end of the Doctor’s scarf, turned about, and fled into the trees.

  ‘Well, that’s a bit of a ewe-turn,’ said the Doctor, winding in the end of his scarf and looking forlornly at the macerated end. He flicked it resignedly over his shoulder.

  By now, Sarah could hear the thunder of approaching footsteps. She parted the bush and peered through. Around thirty men and women dressed in rags and carrying primitive-looking weapons were forming a wide semi-circle around them. They were humanoid, but looked… odd. Like the trees, they were tall and willowy, at least eight feet tall, with thin, gangly limbs. Their skin tones were pale and washed out, like they hadn’t seen enough sunlight, and their noses were almost flat upon their faces, little more than wrinkles of flesh protecting tiny vents.

  The Doctor stood, coming out from behind the bush with his hand extended. ‘How very nice to meet you. I’m the Doctor. This is Sarah. We’re new around these parts.’ He grinned, flashing his teeth.

  The tribes people glared at him, still brandishing their motley assortment of weapons.

  ‘No?’ said the Doctor. He shrugged and lowered his proffered hand. ‘I should work a little on your hospitality, if I were you. All those spears, you’ll scare off the tourists.’

  A tribesman in a bright headdress stepped forward, jabbing his weapon in the Doctor’s direction. Sarah, who had now come around the bush to join the Doctor, could see that it resembled a garden spade.

  ‘Oh, now that’s very interesting,’ said the Doctor. ‘Very interesting indeed. A spade, a hoe, a laser cutter… What fascinating weapons you all have, Mr…?’

  ‘Euripides,’ said the man. His voice was guttural and deep, and, although the accent was thick and unfamiliar, he spoke clearly in a form they could understand. ‘I am Euripides, and you, Doctor and Sarah, are our prisoners.’

  ‘Oh, why aren’t I surprised?’ muttered Sarah. ‘It would be nice if, just once, we were greeted by people who wanted to give us tea.’

  The Doctor laughed. ‘Let me guess, Euripides. You’re going to take us to your leader. Good.’

  Euripides jabbed his spade at them. ‘You will come with us to the Temple of Life,’ he said.

  ‘Oh, if you insist,’ said the Doctor, tipping the brim of his hat. ‘Lead on, lead on!’

  The Doctor and Sarah were led at spear point through the flora, following trails that felt more like the claustrophobic tunnels of a military bunker than any natural environment. They walked in single file, with little conversation, and although they must have trudged through the undergrowth for over a mile, the going wasn’t too tiresome, given the reduced gravity.

  After being poked, prodded and ignored by their captors, Sarah was close to boiling point by the time they reached the place Euripides called the ‘Temple of Life’.

  It was, in fact, a large clearing in the heart of the forest, a nexus point for the paths through the trees. Here, the tribe had erected makeshift shelters from sheets of corrugated plastic and tempered steel. Sarah was surprised to see winking diodes and other signs of electrical power nestled amongst the foliage. Children gambolled around them, playing games of chase, and men were distributing food amongst themselves on tarnished metal dishes. Clearly, these tribes people weren’t as primitive as she’d first imagined.

  ‘In here,’ said Euripides, gesturing to one of the huts. ‘You shall face the judgement of the Elders.’

  ‘How delightful,’ said the Doctor. ‘I do enjoy a good chinwag with an enlightened one,’ he added, quietly.

  ‘You’re incorrigible,’ said Sarah, unable to contain a laugh. She followed him into the hut, closely followed by Euripides, still wielding his spade.

  Inside, two figures sat cross-legged on wooden plinths, at either side of another open doorway. One, on the left, was male. The other, on the right, was female. Both had their eyes closed, in meditative trance. They were similar in appearance to the rest of the tribes people, save for the fact they weren’t carrying weapons.

  Euripides gestured to a woven mat in the centre of the floor, and, with some reluctance, Sarah lowered herself onto it beside the Doctor.

  ‘I am the left-tenant,’ said the man, after a moment.

  ‘And I am the right-tenant,’ said the woman.

  ‘You come before us as strangers,’ went on the left-tenant, ‘but I see you are not of the other tribe.’

  ‘I’m Sarah Jane Smith, from Earth,’ said Sarah.

  ‘And I’m the Doctor.’ He raised his hat in genial fashion, and then replaced it. ‘I suppose you could say I’m a citizen of the galaxy.’

  The right-tenant arched an eyebrow. ‘You trespass within our borders. Were you sent by the pilot?’

  ‘The pilot?’ said the Doctor, his tone thoughtful. ‘No, no. Not the pilot. We’ve only just arrived, you see.’

  ‘Then you have come to plunder the crucible,’ said the left-tenant, his voice growing in ire.

  ‘No!’ said Sarah. ‘It’s not like that at all. We’re explorers. We’re here to help.’

  ‘To help?’ said the right-tenant. She looked from Sarah to the Doctor. ‘Then you come to protect us from the other tribe?’

  ‘Yes, if you like,’ said the Doctor. ‘Tell us about them.’

  ‘They hunger for the crucible,’ said the left-tenant. ‘Once, we were many, and our borders ranged for quadrants. Food was bountiful, and the wild beasts did not trouble us. Now, we have been forced to withdraw to protect the crucible. The other tribe grows strong, while we grow weak. Our people are diminished. The sheep and rats hunt us for food. The Temple of Life is our last remaining stronghold.’

  ‘What do they hope to achieve, this other tribe, by capturing the crucible?’ said the Doctor.

  There was a collective intake of breath from the two Elders. They glanced at one another. ‘They are heathens,’ said the right-tenant. ‘Unschooled in the Manual.’

  ‘As surely as the pilot guides our way,’ agreed the left-tenant.

  ‘We told you, we’ve only just arrived,’ said Sarah. She could hear the impatience in her own voice.

  ‘The crucible is the source of all life,’ said the left-tenant. ‘The origin of the Uman species.’

  ‘The well-spring from which we all flow,’ added the right-tenant. ‘When we reach Fall, the avatars will live anew.’

  ‘And this other tribe want the glory for themselves,’ said the Doctor. ‘They want to be there when the avatars awaken. Oh, I’ve heard it all before. Usual story. And here I was hoping for something new.’

  Sarah heard footsteps entering the hut behind her. She looked round. One of the tribes people was silhouetted in the doorway, but she could tell from the ragged breath and a glimpse of his troubled expression that something was wrong. ‘They’re here!’ he said. ‘They’ve come for the cruc—’

  He broke off abruptly as the tip of a spear buried itself in his back, and he toppled forward, gasping for breath. Outside, Sarah could hear shouting. ‘Doctor?’ she said, panic rising.

  The Doctor was already on his feet. He grabbed her hand and pulled her up beside him. ‘In there,’ he said, nodding toward the other doorway.

  ‘You cannot enter the crucible,’ said Euripides, raising his spade to block their path. ‘No one but the Elders are permitted.’

  Sarah watched as the two figures relinquis
hed their positions on the pedestals and walked – with some dignity – into the adjoining chamber.

  The Doctor, of course, was having none of it. He grabbed at the spade, wrenching it from Euripides’ grasp and tossing it angrily to the floor. ‘I told you we’d help, didn’t I?’

  Euripides hesitated and, with a quick ‘Come on,’ the Doctor led Sarah into the crucible.

  It was not what she’d been expecting. Hearing the Elders go on about the place, Sarah had envisioned a grand temple, an ornate religious structure, but in the event the room was relatively small and underwhelming.

  The floor was formed from a series of interlocking metal grids, while the walls and ceiling were bland metal plating, now tarnished and worn. Around the room were arranged a dozen lozenge-shaped pods, standing upright against the walls, each of them protected by a shattered glass dome. There were no plants in the room, save for the questing vines spilling from the front of the broken pods.

  ‘It reminds me of Space Station Nerva,’ said Sarah.

  ‘Stasis pods,’ said the Doctor as he circled the room, taking it in. ‘They’ve all failed.’

  ‘Then the people in them…’ began Sarah. But it was quite clear. The people inside the pods had long ago decomposed, and now they were reduced to nothing but compost, giving sustenance to the plants.

  ‘We must protect the crucible at all costs,’ said the left-tenant. Sarah had almost forgotten he was there.

  ‘Oh, I think we’re long past that,’ said the Doctor. He was pacing back and forth, a crooked finger held to his chin, looking thoughtful. ‘The crucible… the pilot… the Fall…Yes, of course!’ he exclaimed, evidently pleased with himself.

  ‘They’re colonists from Earth,’ said Sarah. ‘They’ve just forgotten they came here by spaceship.’

  ‘What?’ said the Doctor, in astonishment. ‘No, of course not. We’re still on the spaceship.’