by Lucy Hawking
“And now, in other news—”
VACUA
What is a vacuum, and what does it have to do with vacuum cleaners?
A vacuum means a space so empty it doesn’t even have air in it. So if we pumped all the air out of a room, for example, we would create a vacuum.
VACUA IS
THE PLURAL
OF VACUUM
The vacuum in
the beam pipes of the
Large Hadron Collider
is as empty of gas
molecules as some
regions of outer
space!
A vacuum cleaner uses an air pump to create a puny sort of “would-be” vacuum that helps it to sweep up all the particles of dust when you’re cleaning your house. But you couldn’t use a vacuum cleaner to make the sort of vacuum that we’re talking about here. You’d need something with a much more powerful pump for our experiment.
Removing all the air particles from a room is not an easy job. Even a room completely empty of atoms still contains radiation:
• Infrared photons emitted by the warm walls of the room
• radio photons from
• TV transmitters
• microwave photons left over from the Big Bang
• other particles whizzing through from space (e.g. neutrinos produced by the Sun)
• It also would still contain dark matter!
What if we could remove the radiation by cooling down the warm walls? Then the room would be emptier than the space between galaxies! But it would still contain something called quantum fields. These are what are behind photons, neutrinos, electrons, and the other particles. Physicists call the lowest energy state of the quantum fields the vacuum state, and it is this state—the state without any observable particles—that would now fill our imaginary room.
If we could look closely enough, we would also be able to see tiny ripples in space-time and gravity called gravitational waves.
So, although we may think that the room has been completely emptied when we pumped the air molecules out, close up, this vacuum actually buzzes with activity!
Put energy into a vacuum state (physicists would say excite it), and particles (and antiparticles) appear. It is thought that the vacuum is the state of lowest energy. There may be many other vacuum states with equally low energy—when excited they would create familiar-looking particles. In the early Universe, when the temperature was much higher, space may have existed for a little while in a false vacuum state with higher energy, whose particles would seem exotic today. As the temperature fell, this false vacuum would have decayed into our current lower-energy vacuum. A true vacuum is one which really does have the lowest possible energy.
There is no reason to think that any experiment on Earth could kick us into a different vacuum!
Terence switched off the radio. “Is this true?” he said somberly to George. “Are we really at risk from Eric’s experiments?”
“No!” exclaimed George. “Of course not! Eric wants to help human beings, not destroy them!”
“Then why are they saying those things about him on the radio?”
“I don’t know,” said George. “Someone wants to stop him from making discoveries, so they’ve invented this bogus theory about the True Vacuum. I have to find out why! I need to help Eric.”
“You need to do your homework,” said his dad seriously. “And stay away from Eric and his family for now. I don’t want you getting mixed up in this—do you understand me, George? If there is a reasonable explanation, we’ll wait to hear it from Eric himself. Until then, you keep out of the way. Do you promise me?”
“I promise,” said George. But even though he hated to deceive his father, he had his fingers crossed behind his back.
*
The next morning was Saturday, and George was lying sprawled on top of his bed, fully dressed and wondering what to do next, when his phone rang. Now that he had started at middle school, his parents had finally let him have a cell phone.
“Annie!” He had never been more pleased to hear from her. He’d sent hundreds of texts the evening before, and called her, but she hadn’t replied.
“Did you hear what they said about my dad on the news?” she asked him.
“Erm … yes,” said George cautiously. It must be horrible, he thought, to have a famous dad. “Has he called you?”
“Nope,” sniffed Annie. “He hasn’t texted or e-mailed or anything. Just nothing. But all the over the Internet, people are saying he’s a dangerous lunatic and must be stopped from doing any more experiments because he’s about to destroy the whole Universe. All I know is that Mom says he’s got this big meeting with the Order of Science tonight at seven thirty and she hopes he’s coming home after that.”
“I had a weird note,” confessed George. “From Reeper.”
“From Doctor Reeper?” screeched Annie. “What does it say?”
“It says that your dad is in danger and that evil is at work in the Universe.”
“What use is that?” she exclaimed. “We know that already! Why can’t he say something helpful for a change? Did you speak to him?”
“Nuh-uh,” said George. “He didn’t, like, give a number to call. Just a note, Reeper-style, written on parchment in loopy old writing. Like he’d dipped a feather pen in blood or something.”
“How very Reeper-the-Creeper,” said Annie in a hollow voice.
“I tried to get Pooky working,” George continued.
“And did you?”
“Nuh-uh,” said George again, looking over at Pooky’s cage. The hamster supercomputer was snuffling around in some hay, his little eyes blue and blank and empty of any meaning whatsoever. For once he wasn’t running crazily in his hamster wheel, spinning round and round and round for hours on end. “I even got in touch with Emmett last night, and tried connecting remotely, but he said he couldn’t figure it out either.” Emmett was Annie and George’s computer genius friend in America.
“Rats!” said Annie sadly. “Or rather—hamsters! If the master geek can’t do it, then we’ve got no chance.”
“Emmett did say one thing about Pooky, though,” George told her. “He said that he thinks all this running in the wheel is Pooky’s way of keeping his CPU cool while he’s computing something. Something about coolant pumping around his brain when he’s active.”
“So Pooky is active, but we can’t get him to work!” Annie sighed. “That’s so frustrating! Why won’t Pooky help us?”
George didn’t get to answer, because at that moment a piercing high-pitched noise burst out of the hamster’s cage.
“Was that the babies?” asked Annie, who’d heard it on the other end of the phone.
“Not the babies … ,” said George slowly. “I think that noise came from Pooky.”
Pooky was standing on his hind legs with his nose pointing directly up at the ceiling. His paws scrabbled wildly in the air and he screeched again, a bloodcurdling sound that seemed too loud to come from such a small animal. Suddenly Pooky’s head swung around and he turned to glare at George with his little hamster eyes, which had turned from sky blue to flashing yellow.
“What’s going on?” said Annie sharply.
“Pooky’s having some kind of fit!”
But then Pooky opened his mouth. “George,” he said, in a voice that sounded like a rusty nail scraping across a blackboard. “George.”
“Who said that?” Annie screamed into the phone.
“Pooky … ,” whispered George, whose hair was prickling on the back of his neck. “Pooky just spoke!” Pooky, as far as he knew, had never before uttered a single word. Unlike Cosmos, he was a silent supercomputer. Until a few moments ago.
But the voice Pooky used hadn’t been the voice of a hamster, or even a computer: It was the voice of a human being, and one whom they both knew quite well.
“Reeper!” said Annie. “Pooky spoke to you in the voice of Doctor Reeper!”
“George,” said Pooky aga
in, this time more clearly, “you must help me.”
“What do I do?” said George to Annie, panicking.
“Find out what he wants,” she urged. “But don’t be fooled! Remember what he did to us before!”
“How can I help you?” asked George, horribly aware that he was now having a conversation with an electronic hamster.
“You must come and meet me,” said Pooky, his eyes flashing. “You must travel into space to find me. We need to talk.”
“Reeper, is that you?”
“Who else could it be?” said the hamster in Dr. Reeper’s voice.
“The last time we met,” said George bravely, “you wanted to abandon us to run out of oxygen on a moon forty-one light-years away from Earth. And the time before, you tried to throw Eric into a black hole.”
“I’ve changed,” said Pooky simply. “I want to help you.”
“Why should I believe you?”
“You don’t have to, but if you don’t come and find out what I have to say, Eric will never come home …”
The thought of Freddy, abandoned and alone in a strange place forever, flashed through George’s mind as well.
“Why can’t you tell me now?” he said, seizing the little hamster with both hands. “What’s happening to Eric?”
“Eric is in grave danger … Only you can save him, George. Only you. Meet me. Pooky will bring you to me. I don’t have much time. You must leave immediately. Good-bye, George. See you in space!”
“Reeper!” George shouted at the hamster. “Reeper! Come back!” But Pooky’s eyes had turned blue again, and George realized that the connection had been lost.
“What did he say?” Annie yelled into the phone.
At that moment the hamster gave a shudder, and a tiny pellet dropped out of his furry backside.
“He said”—the phone was shaking in George’s hand—“that I must come and meet him in space!”
“But where?” cried Annie. “Where in space are you supposed to meet him?”
“He didn’t say. He didn’t tell me where to come or how to get there.”
“Try Pooky again!” ordered Annie.
George picked up the little hamster and gently pressed all over his tiny furry body to see whether there was some hidden switch they hadn’t yet found. But the hamster just gazed back at him with the same empty expression as before.
“I’m on my way over,” said Annie.
“No, don’t come!” said George. “There isn’t time.” He picked up the tiny pellet that Pooky had deposited on the floor of his cage. It was a screwed-up ball of paper. George unraveled the pellet, which turned out to be a long thin ribbon of paper with a line of numbers on it, ending in a capital H. “There seems to be another message … Perhaps it’s the destination … ,” he said slowly, remembering a letter that Dr. Reeper had once sent to Eric, giving him the coordinates of a distant planet he wanted Eric to visit. The string of numbers reminded him of the way Reeper had written the location of that planet—the snag being that it had turned out not to exist, and Reeper had actually sent Eric right into the path of a super-massive black hole. “Maybe this is where I’m supposed to meet Reeper …”
“But how will you get there?” asked Annie. “And how do we know it will be safe? Maybe you’re going to fall into a black hole!”
“I can’t talk now,” said George, who had the phone jammed between his shoulder and his ear as he jumped off the bed and wrenched open his cupboard to find the space suit that Eric had given him as a souvenir of their cosmic journeys.
Pooky was stirring again, his blue eyes slowly changing color—the signal, George now knew, that he was about to spring into action.
“I’m coming over,” said Annie firmly. “I’ll be there really fast—I’ve got my bike with me. Don’t go anywhere before I get there.”
“Sorry, Annie,” said George. “I don’t have time to wait.”
Pooky had sat bolt upright and his eyes were now flashing red; they shot out two little beams of light that stopped halfway across the room and started spinning, forming a brilliant circle that whizzed round and round like Pooky’s hamster wheel.
“George!” said Annie into the phone. “Don’t hang up!” At that moment he was struggling into his space suit. “Don’t go into space alone!”
“I don’t have a choice!” George shouted before he put on his space helmet so he could still speak with his normal voice rather than through the voice transmitter. “If I don’t go now, we won’t know what Reeper has to tell us! Annie, I have to go …”
He put the cell phone down on his bed. In front of him, Pooky’s circle of light had grown. Beyond it he saw a silver tunnel, which led off into the distance with no sign of what lay on the other side. George put on his space helmet and took a deep breath from his air tank. Through the transmitter, he could hear Reeper’s voice again.
“George,” he rasped. “George—enter the tunnel of light.”
“Where are you?” asked George, trying to sound brave. He didn’t feel brave. He had never been so scared in all his life. His blood felt like it had frozen in his veins, but his heart was pounding so loudly that he thought his ears might explode.
“I am at the other end, waiting for you,” said Reeper. “Follow the tunnel, George. Come to me.”
When George had stepped through Cosmos’s portal on his previous journeys around the Universe, he had usually been able to see where he was going on the other side. But this time there was only the shimmering silver tunnel, which curved away without showing where it was taking him.
What would he find at the other end? A parallel Universe? Another place in time? Did the tunnel bend away because it followed the curvature of space-time, leading to some mysterious destination far away from the Earth’s gravitational field? What lay in wait for him at the other end? There was only one way to find out.
“If you want to save Eric,” whispered Reeper, “you must go on this journey. Just take the step, George. The tunnel will bring you to me.”
“George!” Annie screamed from the phone on the bed. George could still pick up noises around him, thanks to the external microphone in his helmet. “I can hear Reeper as well! Don’t go!”
George hesitated. Then he heard another voice speaking on the phone. It was Vincent.
“George, buddy,” he said. “Don’t go by yourself! It isn’t safe. Annie’s told me about the portal and Doctor Reeper. You mustn’t do this.”
What? thought George, feeling miffed. What was Vincent doing with Annie at her aunt’s house? All the time he’d been talking to Annie, Vincent had been listening in? Vincent knew about the portal and Cosmos and Dr. Reeper? Vincent knew all the secrets that he and Annie had faithfully sworn never to tell anyone? And now Vincent, karate champion and ace skateboarder as well as Annie’s new BFF, was telling him what to do?
So Vincent thought he couldn’t handle it, did he? Vincent thought he wasn’t brave enough to save Eric, George’s mentor and teacher and Annie’s dad? “I’ll show you, Vincent,” he muttered to himself. “And I’ll save you, Eric, even if no one else will.
“Good-bye, Earth people,” he went on haughtily. “I am going into space. I may be gone for a while.”
He stepped forward toward Pooky’s wheel of light, which quickly sucked him into the tunnel as though he had dived down a waterslide at the park. George whooshed headfirst through the silver tunnel, his arms stretched out in front of him, turning this way and that as he was whisked out of his bedroom to an unknown location.
George didn’t have time to think—he was traveling at immense speed through a blur of shining light on his way to meet his former deadly enemy, Dr. Reeper, somewhere out there in the great cosmic expanse that makes up our Universe.
From a place already light-years behind him, he thought he heard Annie scream, the sound echoing around his space helmet: “Noooooo!”
But it was too late. George was gone.
SPACE, TIME, AND RELATIVITY
Four-Dimensional Space-Time
When we want to go somewhere on Earth, usually we only think in two dimensions—how far north or south, and how far east or west. That is how maps work. We use two-dimensional directions all the time. For example, to drive anywhere you only need to go forward (or reverse), or turn left (or right). This is because the surface of the Earth is a two-dimensional space.
The pilot of an airplane, on the other hand, isn’t stuck to the Earth’s surface! The airplane can also go up and down—so as well as its position over the Earth’s surface, it can also change its altitude. When the pilot is flying the plane, “north,” “east,” or “up” will depend on the airplane’s position. “Up,” for example, means away from the center of the Earth, so over Australia this would be very different from over Great Britain!
The same is true for the commander of a spaceship far away from the Earth. The commander can choose three reference directions any way he or she wishes—but there must always be three, because the space in which we, the Earth, our Sun, the stars, and all the galaxies exist is three-dimensional.
Of course, if we have something we need to get to, like a party or a sports event, it isn’t enough to know where it will be held! We also need to know when. Any event in the history of the Universe therefore needs four distances, or coordinates: three of space and one of time. So to describe the Universe and what happens within it completely, we are dealing with a four-dimensional space-time.
Relativity
Einstein’s Special Theory of Relativity says that the laws of nature, and in particular the speed of light, will be the same, no matter how fast one is moving. It’s easy to see that two people who are moving relative to each other will not agree on the distance between two events: For example, two events that take place at the same spot in a jet aircraft will appear to an observer on the ground to be separated by the distance the jet has traveled between the events. So if these two people try to measure the speed of a pulse of light traveling from the tail of the aircraft to its nose, they will not agree on the distance the light has traveled from its emission to its reception at the nose. But because speed is distance traveled divided by the travel time, they will also not agree on the time interval between emission and reception—if they agree on the speed of light, as Einstein’s theory says they do!