George and the Unbreakable Code

by Stephen Hawking

  A real computer more normally works with binary digits (bits) that take the values 0 or 1 only—and any data—numbers, text, images, program instructions—can be represented (coded) by integers in binary notation, and put together as one long binary number in the computer’s memory.

  The mathematics behind digital computers is based on the Universal Turing Machine. A digital computer accepts the program (the list of instructions for a particular Turing Machine, which can be coded into the form of a big binary number) as part of its input and uses this to perform the same job on the rest of the input. So the “computer,” as we understand the idea today, is a single machine capable of computing anything “Turing-computable,” if input with the right program and given enough time and memory to run it.

  The first was produced in 1941: the Z3, by Konrad Zuse in Germany. It used telephone relays instead of gear wheels—and was therefore electromechanical rather than mechanical—and its input came from punched film tape. It was quickly followed in 1946 by the first electronic general-purpose (Turing-complete) digital computer—the American ENIAC. If you looked inside, though, the electronics weren’t on boards studded with chips as today, but consisted of lightbulb-sized vacuum tubes. It was enormous too: it took up around 1,800 square feet of floor space!

  In 1949, Cambridge University built and started to use another valve-based, electronic, and Turing-complete computer, EDSAC, for research, and over the following decades the electronics shrank, first from tubes to transistors, then to integrated circuits and microprocessors with very large numbers of electronic parts etched onto single pieces of silicon.

  Computers today

  A computer today is a machine we expect to be able to read and store digital data and instructions, and then automatically do what we want it to do at the press of a few keys—or by moving a mouse, swiping, pinching, or touching a screen. It is a lot smaller than its predecessors too. And as the electronics shrank, with more and more tiny parts crammed closer and closer together, the speed of a computer increased enormously.

  But unlike the Turing Machine, way back in the 1930s, a real computer still only has a finite amount of memory—it might, for example, have 2GB of RAM (Random Access Memory). It also has to perform basic operations at a very high speed—maybe 20,000,000,000 steps or “floating point operations” per second (20 gflop/s).

  For example, when you double-click on an image file on your laptop, the viewer application and the image file are both read into memory from the disk, then the processor runs the application instructions on the image data to decode it into the correct colored dots to send to the screen so you can see what you asked for. And see it quickly, too.

  A typical computer today also has permanent storage (a hard disk) that lets you turn the computer off without losing your files. It often has a connection to other computers and most likely is able to log on to the Internet.

  Many homes now have a personal computer—or more than one—and individual people can even carry one in a pocket on a tablet, or access the Internet on a smartphone. New technology is coming out every year, and the computers of the future may look very different.

  • One byte is a group of 8 bits, which is enough to store any letter of the alphabet

  • One gigabyte is 1,073,741,824 bytes

  George’s Guide to Staying Safe Online.

  Give no personal information

  Stay safe by never giving out personal information when you’re chatting or posting online. Personal information includes your full name, email address, phone number, and password. If an app or person online asks for this information, then check with your parent or a trusted adult if it is okay before you share anything.

  Emails aren’t always great

  Accepting emails, or instant messages, or opening files, pictures, or texts from people you don’t know or trust can lead to problems—they may contain viruses or nasty messages. Be careful!

  Online friends

  Meeting someone you have only been in touch with online can be dangerous. Only do so with your parents’ or caregivers’ permission and even then only when they can be present. Remember online friends are still strangers even if you have been talking to them for a long time.

  Really?

  Someone online might lie about who they are, and information on the Internet may not be true. Always check information with other websites, books, or someone who knows about the subject. If you like chatting online, it’s best to only chat to your real-world friends and family.

  Get with the family

  Share what you do and who you talk to online with your parent, caregiver, or trusted adult. The Internet shouldn’t be about secrets. Use your technology in the same room as grown-ups and let them see what you are up to. It will be easier for both of you to talk about any issues that arise.

  Explain your worries

  Tell your parent, caregiver, or a trusted adult if someone or something makes you feel uncomfortable or worried, or if you or someone you know is being bullied online.

  The Internet is by far the biggest source of shared knowledge you have access to—you can learn lots about space, technology, and new ideas. Don’t forget to have fun and stay safe!

  Inside Old Cosmos’s lair it was dry, warm, and almost cozy—at least compared to what was happening in the world above their heads. A fan whirred gently, keeping the old computer cool and the air moving around what might otherwise become a rather stale underground room. Geothermally powered, Old Cosmos was an antique piece of technology with a futuristic energy supply. The previous year, Eric had decided to investigate renewable energy alternatives to keep his power-hungry machines operational. He had suggested that the different parts of the university should use separate energy systems, so that a failure in one place wouldn’t affect another. In the current situation, Old Cosmos, who drew his energy right from the core of the Earth itself, was the only functional machine left in the building. The lights on his impressive stacks of hardware shone brightly, a welcome sight after the grayish-green darkness of the outside world.

  “Cosmos, the world has gone crazy! The computers are malfunctioning, and now there are robots on the streets! Has anyone tried to attack you?” asked George. “Little Cosmos has been hacked—we think by the person or organization doing all these weird things.”

  Ha, ha, ha, said Old Cosmos. No one would bother attacking me. They think I’m a relic. It would be like attacking the pyramids.

  “But you’re not, are you?” said Annie fondly. “A relic, I mean. Or a pyramid.”

  I am a remarkable piece of technological architecture. Old Cosmos transferred his words onto paper even more rapidly than before. I may not have all the modern capabilities, but I can still perform extraordinary computational feats.

  “Like sending us into space?” said George hopefully.

  I have been portal-modified, replied Cosmos with dignity, not quite admitting that this had not been one of his original functions, by a former user.

  Annie and George exchanged glances. They knew what that meant. Last year, Eric’s old tutor, Professor Zuzubin, had been secretly using Old Cosmos for his own purposes—which included an attempt to blow up the Large Hadron Collider just when the world’s physicists were gathered there together. Zuzubin planned to be the only remaining scientist so that his theories, long ago shown by Eric to be entirely bogus, would be accepted. He’d also tried to use Old Cosmos as a time machine: he wanted to go back and edit history, changing his earlier scientific predictions to make himself look like a genius in the present. But he had been unable to change the course of history; the past had protected itself from this kind of cosmic piracy. All the scientists, Annie’s dad among them, had managed to leave the Collider in one piece and carry on with their work. However, Zuzubin’s legacy was proving to be surprisingly useful in the present crisis… .

  “Zuzubin must have added the space door,” Annie murmured to George.

  “Gosh, I never thought we’d say thank you to him
!” he replied, remembering the seemingly mild-mannered, white-haired professor who had, it turned out, belied his appearance. “Dangerous” wasn’t really the word for Zuzubin … “deluded to the point of insanity,” “power hungry,” and “reputationally challenged” were phrases that summed him up better.

  “But where do we want to go? We don’t know where Ebot is yet!”

  “Cosmos,” said Annie, “we’ve sent our robot into space with a tracking device—using these glasses, we should be able to see where he is. We haven’t spotted anything yet, but we’re hoping that some visuals will come through very soon. Can you connect to them and tell us where we need to go?”

  Easy peasy, typed out Cosmos. Please attach the hardware device to one of my ports.

  “Ports … ports … ports …” Annie rapidly scanned the enormous cliff face that was Old Cosmos as she unfurled a cable from her shorts pocket. “If I was a port, where would I be?”

  “There!” said George, pointing to a spot just below Cosmos’s screen. “Plug it in there!”

  Annie connected the glasses to the cable and plugged the other end into Cosmos. His screen went fuzzy and gray, but then quickly lit up.

  At first there just seemed to be random shapes, blurred and colorless, moving in a way that made no visual sense. But Cosmos quickly used the zoom function to sharpen the images, and changed the brightness so it threw them into relief.

  They peered at the scene in front of them. It was still hard to make sense of what they were seeing. The angles kept changing, so they still had no idea what they were looking at.

  “Look!” said George, squinting at the screen. “Over there! It’s that same robot. It’s like the one we saw on the Moon and the one that chased us here—or maybe it’s another one and they’re all identical!” The robot appeared briefly in front of them, and seemed to somersault, turning a complete circle in the air!

  “They’re in space!” said Annie. “That’s why it looks weird. Ebot is floating—it looks like he’s in some kind of spaceship. Cosmos, can you locate it?”

  Old Cosmos muttered away for a few minutes. They heard his circuits clacking as he tried to trace the exact position of the signal.

  “OMG!” Annie exclaimed. “Look! There isn’t just one robot!”

  Looking through Ebot’s eyes, they now saw that he was in a tube-like corridor with pipes and wiring all over the walls. Around him floated a host of robots that resembled those they had seen on the Moon and just now, in Foxbridge. When the kids got used to the fact that Ebot was in a low-gravity environment, they realized that he was surrounded by floating robots, all guiding him in one direction.

  “Wow!” said Annie. “It’s like Ebot’s got a robot police squad around him!”

  “Who do they belong to?” wondered George. “Who would have so many on a space station? It looks like a robot army.”

  “Cosmos, where is this?” asked Annie.

  They didn’t have to wait long for the printout.

  Do you want to know where it is, or how fast it is moving? Cosmos needed some further direction from them before he could complete his report.

  “We want to know where!” said Annie. “We don’t care how fast it’s going.”

  Your personalized android’s location is a space station that is currently in orbit around planet Earth.

  “That’s not the International Space Station!” exclaimed Annie, who had become very familiar with the inside of the ISS: the commander had broadcast updates and photos every day on Twitter, and she had followed his posts eagerly.

  George studied the paper spilling out of the computer and pooling in great rolls at his feet. “Old Cosmos says here that it’s a privately owned space station, but there is almost no information available about it. It’s like it doesn’t exist … except we can see that it does.”

  “How is that possible?” asked Annie.

  “It may have been ‘cloaked,’ according to Cosmos,” George told her, “to prevent it from being seen. And it may have quantum properties that allow it to change location. Which is why it’s been moving around from place to place—like to the Moon and then the comet.”

  “That’s superweird,” said Annie. “Does Cosmos think it’s linked to what’s happened on Earth? Does he know what’s happened on Earth?”

  Furious printing followed Annie’s question.

  Of course I know! Cosmos wrote. Please address me directly. It is rude to talk about me in the third person.

  “Sorry,” said Annie humbly. “It’s just that we’re living in a very strange world where it seems that anything is possible.”

  Right at the beginning of the computer age, Cosmos told her, we pointed out that there was a danger of connecting everything to everything else. It has made it too easy to bring everything crashing down.

  “Well, it doesn’t look like anyone listened,” said George.

  “Cosmos …” Annie directed her comments straight at the old computer. She’d noticed that he could be as cranky as his mini-me, Little Cosmos, used to be, before he got hacked and turned all oily and polite. “Can you take us to Ebot’s location on the spaceship? Not his exact location, because it looks like he’s with a robot police force who are escorting him somewhere, but close enough to find out what’s going on?”

  Affirmative, typed Cosmos.

  “And can you ‘cloak’ us? Can you make us invisible so that when we get to the spaceship, no one can see us?”

  There was a pause.

  I can’t give you an invisibility cloak . Old Cosmos actually added a sad face emoticon.

  “That’s so cute,” murmured Annie. “Cosmos, why don’t you have a voice?” she wondered suddenly. By now, the whole basement was filling up with the reams and reams of paper that Cosmos had used up in communicating with them.

  Because no one has made one for me, he told her. So I am voiceless.

  “Aw, I’m doing a sad face now.” Annie actually thought she might cry.

  But I can give you a time cloak, Cosmos carried on.

  “What’s a time cloak?” she asked.

  It means even if someone has managed to pick up my network activity, they won’t know you have space traveled through a portal until around three minutes after you’ve gone. So I can give you three minutes’ head start.

  “Do it,” said Annie decisively. “Right, let’s get moving. Do we need our space suits?”

  George looked doubtful. “It’s hard to say,” he replied. “But most space stations are climate-controlled inside, so no one wears a space suit while they’re actually on board.”

  “But this is like a weird, invisible space station,” explained Annie. “So who knows what it’s like inside?”

  “If it’s invisible,” said George, “then how come we can see it now?”

  Because your android is sending us a signal from his tracking device from inside the station, Cosmos explained. If he wasn’t actually there, we would never have found it.

  “But we saw it from Earth!” said George. “I managed to take a photo of it!”

  A glitch in the metamaterial of the invisibility cloak, said Cosmos, must have produced a brief period when the ship was visible, during which time you took its photo.

  “So that’s why Dad has no idea about it!” said Annie. “That’s why all the international governments are unable to find this ship and whoever is on it! Cosmos, get ready to hide us from time itself.”

  Cosmos did some complicated computations of his own, with the result that a doorway that George and Annie hadn’t noticed until now—concealed as it was among all the circuitry and paneling on Cosmos’s impressive rows of stacks—started to glow.

  “Remember,” said George, “we need to open the door. It’s not like the other portal: we have to physically open it and step through; last time it had a sort of hallway before we reached our destination.”

  “What if we fall down the gap and end up in space without our space suits on?” said Annie, grimacing.

  “The
n we’ll freeze and boil at the same time; our blood gases will explode while our eyes literally pop out of our heads,” said George helpfully.

  “Thanks,” murmured Annie. “You’re sure we have to do this? And that we don’t need our space suits?”

  “Pretty sure,” he said. “Eric will never find the space station without us—we might be the only people on Earth who have a chance of finding I AM and working out whether he, it, or they are definitely linked to what’s gone wrong everywhere.”

  “Okey-doke,” said Annie. “Looks like it’s just you and me again.”

  The door glowed brighter and brighter in a rainbow of colors, until it looked like a lit-up Christmas tree—a beautiful sight in the dim basement.

  Without saying anything more, they edged closer to each other. Annie held out her hand, and George took it in his gloved one: while Annie had been talking to Old Cosmos, he had fished Ebot’s black haptic gloves out of his pocket and put them on, in case they turned out to be useful.

  “Should we take the glasses with us?” Annie asked.

  Negative, Cosmos typed out. I need them to follow the tracking signal so that I can send you to the right location.

  “You will get us inside the spaceship, won’t you?” whispered Annie. “Not floating about in space, outside.”

  Unlike later imitations, typed Cosmos snippily, I never make mistakes. Please step forward. The portal is ready.

  The two of them took a deep breath and stepped forward. George pulled back the door with his free hand. Through the doorway, they could see nothing but a blaze of multicolored lights swirling in great green, pink, and orange clouds.

  “What’s through there?” asked Annie nervously.

  “We won’t find out until we go through,” said George. “Do you remember? Old Cosmos can’t show us what’s ahead—we need to step forward; otherwise we’ll never know.”

  “Wait!” said Annie, tearing a sheet of paper off Cosmos’s printouts and scribbling something on the back of it with a pencil she’d found in her pocket.

  “What are you doing?” asked George.