George's Secret Key to the Universe

by Stephen Hawking

  Eric’s computer was small and glossy. It looked powerful and neat—the sort of computer you might find on a spaceship. Eric hit a couple of buttons on the keyboard, and the computer made a sort of humming noise while bright flashes of color shot across the screen. He patted the computer happily.

  “You have forgotten something,” said a strange mechanical voice. George jumped out of his skin.

  “Have I?” Eric looked confused for a moment.

  “Yes,” said the voice. “You have not introduced me.”

  “I’m so sorry!” exclaimed Eric. “George, this is Cosmos, my computer.”

  George gulped. He had no idea what to say.

  “You have to say hello to Cosmos,” said Eric in a side whisper to George. “Otherwise he’ll get offended.”

  “Hello, Cosmos,” said George nervously. He’d never spoken to a computer before, and he didn’t quite know where to look.

  “Hello, George,” replied Cosmos. “Eric, you have forgotten something else.”

  “What now?” said Eric.

  “You have not told George I am the most powerful computer in the world.”

  Eric rolled his eyes up to heaven. “George,” he said patiently, “Cosmos is the most powerful computer in the world.”

  “That is correct,” agreed Cosmos. “I am. In the future, there will be computers more powerful than me. But there are none in the past or present.”

  “Sorry about this,” Eric whispered to George. “Computers can be a bit touchy sometimes.”

  “I am smarter than Eric, too,” boasted Cosmos.

  “Says who?” said Eric crossly, glaring at the screen.

  “Says me,” said Cosmos. “I can compute billions of numbers in a nanosecond. In less time than it takes you to say ‘Cosmos is great,’ I can compute the life of planets, of comets, of stars, and of galaxies. Before you can say ‘Cosmos is the most impressive computer that I have ever seen, he is truly incredible,’ I can—”

  “All right, all right,” said Eric. “Cosmos, you are the most impressive computer we have ever seen. Now, can we move on? I want to show George how a star is born.”

  “No,” said Cosmos.

  “No?” said Eric. “What do you mean, no, you ridiculous machine?”

  “I don’t want to,” said Cosmos snootily. “And I am not ridiculous. I am the most powerful computer that has ever been—”

  “Oh, but ple-e-ease,” pleaded George, interrupting him. “Please, Cosmos, I really want to see how a star is born. Please won’t you show me?”

  Cosmos was silent.

  “Oh, come on, Cosmos,” said Eric. “Let’s show George some of the wonders of the Universe.”

  “Maybe,” replied Cosmos sulkily.

  “George doesn’t have a very high opinion of science,” Eric went on. “So this is our chance, Cosmos, to show him the other side of science.”

  “He must take the oath,” said Cosmos.

  “Good point—smart Cosmos,” said Eric, leaping over to the blackboard.

  George turned and studied the writing on it more closely. It looked like a poem.

  “George,” said Eric, “do you want to learn about the greatest subject in the whole Universe?”

  “Oh yes!” exclaimed George.

  “Are you prepared to take a special oath to do so? To promise that you will use your knowledge only for good and not for evil?” Eric was staring at George intently from behind his big glasses. His voice had changed—he now sounded extremely serious. “This is very important, George. Science can be a force for good, but as you pointed out to me earlier, it can also do great harm.”

  George stood up straighter and looked Eric in the eye. “I am,” he confirmed.

  “Then,” said Eric, “look at the words on the blackboard. It is the Oath of the Scientist. If you agree with it, then read the oath out loud.”

  George read what was written on the blackboard and thought about it for a moment. The words of the oath didn’t frighten him. Instead they made him feel tingly with excitement, right down to his toes. He read the oath out loud, as Eric had instructed.

  “I swear to use my scientific knowledge for the good of Humanity. I promise never to harm any person in my search for enlightenment …”

  The living room door opened, and Annie sidled in, clutching a huge multipack bag of potato chips.

  “Keep going,” said Eric encouragingly. “You’re doing very well.”

  George read out the next part.

  “I shall be courageous and careful in my quest for greater knowledge about the mysteries that surround us. I shall not use scientific knowledge for my own personal gain or give it to those who seek to destroy the wonderful planet on which we live.

  “If I break this oath, may the beauty and wonder of the Universe forever remain hidden from me.”

  Eric clapped. Annie burst an empty potato chip package. Cosmos flashed a rainbow of bright colors across his screen.

  “Well done, George,” said Eric. “You are now the second youngest member of the Order of Scientific Inquiry for the Good of Humanity.”

  “I salute you,” said Cosmos. “From now on, I will recognize your command.”

  “And I’ll let you have some chips!” piped up Annie.

  “Annie, shush!” said Eric. “We’re just getting to the good part. George, you may now use the secret key that unlocks the Universe.”

  “Can I?” asked George. “Where is it?”

  “Go over to Cosmos,” said Eric quietly, “and look at his keyboard. Can you guess which one you need to press? Can you figure out which one is the secret key that will unlock the Universe for you? Annie—say nothing!”

  George did as he was told. Cosmos might be the world’s most powerful computer, but his keyboard was just an ordinary, familiar one, with the letters and symbols laid out in the same order as even the school’s crummiest computer. George thought hard. Which key would be the one to unlock the Universe for him? He looked again at the keyboard—and suddenly he knew.

  “It’s this one, isn’t it?” he said to Eric, his finger hovering.

  Eric nodded. “Press it, George. To begin.”

  George’s finger came down on the key marked ENTER.

  Suddenly the lights in the room started to fade …

  “Welcome,” said Cosmos, playing a little computerized fanfare, “to the Universe.”

  The room was getting darker and darker. “Come and sit here, George,” called Annie, who had already settled herself on the big comfy sofa. George sat down next to her, and after a few seconds he saw a tiny beam of very bright white light. It came directly from Cosmos’s screen. The beam shot out into the middle of the room, where it wavered for a second before it began to sketch a shape in the air. It moved from left to right in a straight line before dropping down toward the floor. Leaving a shining path of light behind it, it turned another corner to make three sides of a rectangle. One more right angle and the beam of light came back to its starting point. For a second, it looked like a flat shape hanging in the air, but suddenly it turned into something real and very familiar.

  “But that looks like a—,” said George, who could suddenly see what it was.

  “A window,” said Eric proudly. “Cosmos has made us a window on the Universe. Watch closely.”

  The beam of light disappeared, leaving the window it had drawn in the middle of Eric’s living room, hanging in midair. Although the outline was still shining with bright light, it now looked exactly like a real window. It had a big sheet of glass in the pane and a metal frame. Beyond it, there was a view. And that view was not of Eric’s house, or of any house, road, or town, or anywhere else that George had ever seen before.

  Instead, through the window George could see an incredible, vast darkness, peppered with what looked like tiny bright stars. He started to try and count them.

  “George,” said Cosmos in his mechanical voice, “there are billions and billions of stars in the Universe. Unless you are as smart as
me, you will not be able to count them all.”

  “Cosmos, why are there so many?” asked George in wonder.

  “New stars are created all the time,” answered the great computer. “They are born in giant clouds of dust and gas. I am going to show you how it happens.”

  “How long does it take for a star to be born?” George asked.

  “Tens of millions of years,” replied Cosmos. “I hope you are not in a hurry.”

  “Tut-tut,” said Eric, sitting cross-legged on the floor beside the sofa, his long, thin limbs bent at sharp angles. He looked like a friendly giant spider. “Don’t worry, George, I’ve speeded it up quite a lot. You’ll still get home for dinner. Annie, pass the chips around. I don’t know about you, George, but the Universe always makes me very hungry.”

  “Oh dear,” said Annie, sounding embarrassed. There was a rustling noise as she rooted around inside the big bag. “I’d better get some more.” She leaped off the sofa and dashed back to the kitchen.

  As Annie left the room, George noticed something about the view through the window onto outer space: Not all of it was covered with little stars. In the bottom corner of the window he saw a patch of total darkness, a place where not a single star shone.

  “What’s happening there?” He pointed.

  “Let’s have a look, shall we?” said Eric. He pressed a button on a remote control, and the view through the window seemed to zoom toward the dark patch. As they got closer, George realized that an enormous cloud was hovering in that spot. The window kept moving forward until they were right inside the cloud itself, and George could see it was made of gas and dust, just as Cosmos had said.

  “What is it?” he asked. “And where is it?”

  “It’s a huge cloud in outer space, much bigger than the ones in the sky,” replied Eric, “made up of tiny, tiny particles that are all floating around inside it. There are so many of these particles that the cloud is enormous—it’s so big that you could put millions and millions of Earths inside it. From this cloud, many stars will be born.”

  Inside the cloud, George could see the particles moving around, some joining together to form huge lumps of matter. These great lumps spun around and around, gathering even more particles all the time. But as the particles joined together, the spinning lumps weren’t getting bigger; instead, they seemed to be getting smaller, as though something was squeezing them. It looked like someone was making gigantic dough balls in outer space. One of these giant balls was quite close to the window now, and George could see it spinning around, getting smaller and smaller all the time. As it shrank, it became hotter and hotter—so hot that George could feel the heat from where he sat on the sofa. And then it started to glow with a dim but frightening light.

  PARTICLES

  Elementary particles are the smallest possible things that cannot be divided up into smaller particles. Examples include the electron, which carries electricity, and the photon, which carries light.

  An atom is not an elementary particle because it is made of electrons going around a nucleus in the center, like the planets go around the Sun. The nucleus is made of protons and neutrons packed tightly together.

  Protons and neutrons were previously thought to be elementary particles, but we now know they are made of smaller particles called quarks, held together by gluons, which are the particles of a strong force that acts on quarks but not on electrons or photons.

  A helium atom: 2 neutrons and 2 protons in the core, and 2 electrons circling around.

  “Why is it glowing?” asked George.

  “The more it shrinks,” said Eric, “the hotter it gets. The hotter it gets, the brighter it shines. Very soon it’s going to get too hot.” He grabbed a couple of pairs of strange sunglasses from a pile of junk on the floor.

  “Wear these,” he told George, putting on a pair himself. “It will soon be too bright for you to look at without glasses.”

  Just as George put on the very dark glasses, the ball exploded from the inside, throwing off its outer layers of burning-hot gas in all directions. After the explosion, the ball was shining like the Sun.

  “Wow!” said George. “Is that the Sun?”

  “It could be,” Eric replied. “That’s how stars are born, and the Sun is a star. When a huge amount of gas and dust combines and shrinks to become dense and hot, as you’ve just seen, the particles in the middle of the ball are so pressed together they start to fuse or join up, releasing an enormous amount of energy. This is called a nuclear fusion reaction. It is so powerful that when it starts, it throws off the outer layers of the ball, and the rest is transformed into a star. That’s what you just saw.”

  The star was now shining steadily in the distance. It was a beautiful sight. Without the special sunglasses, they wouldn’t have been able to see much because the star was so bright.

  George gazed at it, amazed by its power. Every now and then he could see huge jets of brightly shining gases sent hundreds of thousands of miles from the surface at extraordinary speeds.

  MATTER

  Matter is made of atoms of various types. The type of atom, or element, as it is called, is determined by the number of protons in the nucleus. This can be up to 118, with mostly an equal or greater number of neutrons.

  The simplest atom is hydrogen, whose nucleus contains just one proton and no neutron.

  The largest naturally occurring atom, uranium, has a nucleus that contains 92 protons and 146 neutrons.

  Scientists think that 90% of the total number of all atoms in the Universe are hydrogen atoms.

  The remaining 10% are all the 117 other atoms, in various proportions. Some are extremely rare.

  When atoms join together in chains, the resulting object is called a molecule. There are countless molecules, of various sizes, and we build new ones all the time in laboratories.

  Before stars are born, only the simplest molecules can be found in space. The most common is the hydrogen molecule, which is inside the huge clouds of gas in outer space where stars are born. It consists of two hydrogen atoms joined together.

  “And the star will keep on shining like this forever?” he asked.

  “Nothing is forever, George,” said Eric. “If stars shone forever, we wouldn’t be here. Inside their bellies, stars transform small particles into larger ones. That is what a nuclear fusion reaction does: It fuses small particles together, and builds big atoms out of small ones. The energy released by this fusion is enormous, and that’s what makes stars shine. Almost all the elements that you and I are made of were built inside stars that existed long before the Earth. So you could say that we are all the children of stars! When they exploded a long time ago, these stars sent into outer space all these large atoms they created. The same will happen to the star you are looking at now, behind the window. It will explode at the end of its life, when there are no more small particles available to fuse into bigger ones. The explosion will send into outer space all the large atoms the star created in its belly.”

  On the other side of the window, the star was looking angry. Its bright yellow color was turning reddish as it grew and grew, until it was so big that it was almost impossible to see anything else through the window. It seemed to George that the star might explode at any moment. Eric pressed his remote control again, and the window immediately moved away from the star, which kept getting redder and bigger all the time.

  “Isn’t it amazing!” exclaimed Eric. “At first the ball shrinks and gives birth to a star, and then the star gets bigger and bigger! And now it is about to explode! Whatever you do, don’t take off your glasses.”

  George watched the star in fascination. Suddenly, long after it had reached a size no one could have imagined, the most powerful explosion George had ever seen happened just in front of him. The whole star blew up, sending into outer space enormous quantities of light and red-hot gas, including all the new atoms it had created. After the explosion, George saw that all that was left of the star was a beautiful new cloud, ful
l of extraordinary colors and new materials.

  “Ooooh-ahhhh!” he said. It was like watching the most incredible fireworks display.

  “You see,” said Eric, “with time, the colorful cloud you now see will mix with other clouds, ones from far distant stars that have also exploded. As they cool down, all the gases from these clouds will mix together into an even bigger cloud, where stars will be born again. Near where these new stars appear, the leftover elements will gather together to become objects of various sizes—but not ones big enough to become stars themselves. Some of these objects will become balls, and with time, these balls will turn into planets. In real life, it takes a very long time for all this to happen—tens of millions of years!”

  “Wow!” George was fascinated.

  “But we haven’t got that much time to wait, and you need to get home for your supper,” said Eric, going over to Cosmos and pressing a few more keys. “So let me speed it up a bit. Here we go!”

  In the blink of an eye, the tens of millions of years Eric was talking about had passed. The gas from the explosion of dozens of stars had gathered into an immense cloud. Within this cloud, new stars were appearing everywhere, until one formed just in front of the window. That star’s brightness made all the other stars very difficult to spot. Some distance away from this new star, the gas left over from the cloud was becoming very cold and had started to gather into small, icy rocks. George saw that one of these rocks was heading straight for the window. He opened his mouth to warn Eric, but the rock was traveling far too quickly. Before George could say anything, it smashed into the glass with a shattering, splintering roar, seeming to shake the whole house.