by Lucy Hawking
For Willa, Lola and George, Rose, George,
William and Charlotte
THE LATEST SCIENTIFIC THEORIES!
Within the story are a number of terrific essays on scientific topics that give readers real insight into some of the latest theories. These have been written by the following eminent scientists:
The Creation of the Universe
by Dr. Stephen Hawking, Director of the Center for Theoretical Cosmology, University of Cambridge
The Dark Side of the Universe
by Dr. Michael S. Turner, Director of the Kavli Institute for Cosmological Physics and Rauner Distinguished Service Professor, University of Chicago
How Mathematics Is Surprisingly Useful in Understanding the Universe
by Dr. Paul Davies, Beyond Center, Arizona State University
Wormholes and Time Travel
by Dr. Kip S. Thorne, The Feynman Professor of Theoretical Physics, Emeritus, California Institute of Technology
SPECIFIC FACTUAL SECTIONS
There is lots of science within this book, but there are also a number of separate sections where facts and information are provided on specific subjects. Some readers may wish to refer to these pages in particular.
Our Solar System
Problems Facing Our Planet
The Theory of Everything
The Moon
The Big Bang—A Science Lecture
The Expansion of the Universe
Vacua
Space, Time, and Relativity
Andromeda
Uniformity in Space
Particle Collisions
The Large Hadron Collider
Singularities
The Quantum World
M-Theory—Eleven Dimensions!
Chapter One
Where’s the best place in the Universe for a pig to live? Annie was typing onto the keyboard of Cosmos, the supercomputer. “Cosmos will know!” she declared. “He must be able to find Freddy somewhere better than that shabby old farm.”
The farm where Freddy, the pig, now lived was actually perfectly nice—at least, all the other animals seemed happy there. Only Freddy, George’s precious pig, was miserable.
“I feel awful,” said George sadly as Cosmos, the world’s greatest supercomputer, ran through his millions and billions of files to try to answer Annie’s question about pigs. “Freddy was so angry he wouldn’t even look at me.”
“He looked at me!” said Annie hotly, glaring at the screen. “I definitely saw him send me a message with his piggy eyes. It was: HELP! GET ME OUT OF HERE!”
The day trip to visit Freddy at the farm just outside Foxbridge, the university town where George and Annie lived, had not been a success. When Annie’s mom, Susan, arrived to pick them up at the end of the afternoon, she was surprised to see George red-faced and furious and Annie on the verge of tears.
“George! Annie!” said Susan. “What is the matter with the two of you?”
“It’s Freddy!” burst out Annie, leaping into the backseat of the car. “He hates it at the farm.”
Freddy was George’s pet pig. He had been a Christmas present from George’s gran when he was a piglet. George’s parents were eco-activists, which also meant they weren’t very interested in presents. They didn’t like the way all the discarded, broken, and unwanted toys left over from Christmas built up into huge mounds of old plastic and metal, floating across the seas, choking whales and strangling seagulls, or making mountains of ugly junk on the land.
George’s gran knew that if she gave George an ordinary present, his parents would give it right back, and everyone would get upset. So if he was to keep his Christmas present, she realized she would have to think of something special—something that helped the planet rather than destroyed it.
That’s why, one cold Christmas Eve, George found a cardboard box on the doorstep. Inside it was a little pink piglet and a note from Gran saying: Can you give this young pig a nice home? George had been thrilled. He had a Christmas present his parents had to let him keep; and, even better, he had his very own pig.
The problem with little pink piglets, however, is that they get bigger. Bigger and bigger, until they are enormous—too large for the backyard of an ordinary row house with a narrow strip of land and scattered vegetables growing between the two fences separating it from the neighboring yards. But George’s parents had kind hearts really, so Freddy, as George named the pig, had continued living in his pigsty in the backyard until he reached a gigantic size—he was now more like a baby elephant than a pig. George didn’t care how big Freddy got—he was very fond of his pig and spent long hours in the yard, chatting to him or just sitting in his huge shadow, reading books about the wonders of the cosmos.
But George’s dad, Terence, had never really liked Freddy. Freddy was too big, too piggy, too pink, and he enjoyed dancing on Terence’s carefully arranged vegetable plot, trampling his spinach and broccoli and munching thoughtlessly on his carrot tops. Last summer, before the twins were born, the whole family had been going away. Terence had been super-quick to find Freddy a place at a nearby children’s petting farm, promising George that when they all got back, the pig would be able to come home.
Only this never happened. George and his parents returned from their adventures, and George’s next-door neighbors—the scientist Eric, his wife, Susan, and their daughter, Annie—came back from living in America. Then George’s mother had twin baby girls, Juno and Hera, who cried and gurgled and smiled. And then cried some more. And every time one of them stopped crying, there would be a beautiful half-second of silence. Then the other baby would start up, wailing until George thought his brain would explode and start leaking out of his ears. His mom and dad always looked stressed and tired, and George felt bad about asking them for anything at all. So once Annie came back from America, he started slipping through the hole in the back fence more and more often, until he was practically living with his friend, her crazy family, and the world’s greatest supercomputer in the house next door.
But it was worse for Freddy, because he never made it home at all.
Once the baby girls were born, George’s dad said they had enough on their hands without a great big pig taking up most of the backyard. “Anyway,” he told George rather pompously when he protested, “Freddy is a creature of planet Earth. He doesn’t belong to you—he belongs to nature.”
But Freddy couldn’t even stay in his small, friendly petting farm, which had to close at the beginning of this summer vacation. Freddy—along with the other animals there—had been moved to a bigger place where there were unusual breeds of farm animal, and lots of visitors, especially during summer vacation. It was a bit like him and Annie moving up to middle school, George thought to himself—going somewhere much bigger. It was a bit scary.
“Nature, huh!” he snorted to himself as he remembered his dad’s comments now. Cosmos the computer was still chewing over the complicated question of the best location in the Universe for a homeless pig. “I don’t think Freddy knows he’s a creature of planet Earth—he just wants to be with us,” said George.
“He looked so sad!” said Annie. “I’m sure he was crying.”
On their trip to the farm earlier that day, George and Annie had come across Freddy lying flat on his stomach on the floor of his pig pen, legs splayed out on either side, his eyes dull and his cheeks sunken. The other pigs were trotting around, looking cheerful and healthy. The pen was spacious and airy, the farm clean, and the people that worked there friendly. But even so, Freddy seemed lost in a piggy hell of his own. George felt incredibly guilty. Summer vacation had passed and he hadn’t done anything about getting Freddy home again. It was Annie who
had suggested making the trip to the farm today, badgering her mom into driving them there and picking them up again afterward.
George and Annie had asked the workers what was wrong with Freddy. They’d looked worried too. The vet had examined him: Freddy wasn’t sick, she’d said; he just seemed very unhappy, as though he was pining away. After all, he had grown up in George’s quiet backyard, and had then moved to a small farm with just a few children coming to pet him. In the new place he was surrounded by noisy, unfamiliar animals and had lots of visitors every day: It was probably a big shock. Freddy had never lived with his fellow pigs before. He was totally unused to other animals: In fact, he considered himself more as a person than a pig. He didn’t understand what he was doing on a farm where visitors hung over the edge of the pig pen to stare at him.
“Can’t we take him home?” George had asked.
The helpers looked a little perplexed. There were lots of rules and regulations about moving animals around, and anyway, they felt that Freddy was simply too big now to live in an urban backyard. “He’ll feel better soon!” they reassured George. “Just you wait and see—next time you come to visit, it’ll be quite different.”
“But he’s been here for weeks already,” protested George.
The helpers either didn’t hear or chose to ignore him.
Annie, however, had other ideas. As soon as they got back to her house, she started making plans. “We can’t bring Freddy back to your place,” she said, switching on Cosmos, “because your dad will just take him straight back to the farm. And he can’t live here with us.”
Unfortunately George knew this was true. He looked around Eric’s study: Cosmos was perched on the desk, on top of piles and piles of scientific papers, surrounded by wobbling towers of books, cups of half-drunk tea, and scraps of paper with important equations scrawled on them. Annie’s dad used the supercomputer to work on his theories about the origins of the Universe. Finding a home for a pig was, it seemed, almost as difficult.
When Annie and her family had first moved into this house, George’s pig had made a dramatic entrance, charging through Eric’s study, sending books flying into the air. Eric had been quite pleased, because in all the chaos Freddy had actually helped him to find a book he’d been searching for. But these days, George and Annie both knew that Eric wouldn’t welcome a spare pig. He had too much work to do to look after a pig.
“We need to find somewhere nice for Freddy,” said Annie firmly.
Ping! Cosmos’s screen came to life again and started flashing with different colored lights—a sure sign that the great computer was pleased with himself. “I have prepared for you a summary of the conditions within our local cosmic area and their suitability for porcine life,” he said. “Please click on each box to see a readout of your pig’s existence on each planet within our Solar System. I have taken the liberty of providing”—the computer chortled to himself—“an illustration for each planet with my own comments.”
“Wowzers!” said Annie. “Cosmos, you are the best.”
On Cosmos’s screen were eight little boxes, each marked with the name of a planet in the Solar System. She checked the one labeled MERCURY …
Mercury
Scorched pig
Venus
Smelly pig
Earth
Happy pig
Mars
Bouncy pig
Jupiter
Sinking pig
Saturn
Orbital pig
Uranus
Upside-down pig
Neptune
Windy pig
OUR SOLAR SYSTEM
The Solar System is the name we give to the family of planets that orbit our star, the Sun.
Our Solar
System was
formed around
4.6 billion
years ago
How Our Solar System Was Created
Step One:
A cloud of gas and dust begins to collapse—possibly triggered by shock waves from a nearby supernova.
Step Two:
A ball of dust formed, spinning round and flattening into a disk as it attracted more dust, gradually growing larger and spinning faster.
Step Three:
The central region of this collapsed cloud got hotter and hotter until it started to burn, turning it into a star.
Stars with a mass
like our Sun
take around ten
million years
to form.
Step Four:
As the star burned, the dust in the disk around it slowly stuck together to form clusters, which became rocks, which eventually formed planets, all still orbiting the star—our Sun—at the center. These planets ended up forming two main groups: close to the Sun, where it is hot, the rocky planets; farther out, beyond Mars, the gas planets, which consist of a thick atmosphere of gas surrounding a liquid inner region with, very probably, a solid core.
Because Jupiter
is the largest, it
may have done
most of the
cleaning up
itself.
Step Five:
The planets cleaned up their orbits by gobbling up any chunks of material they came across.
Step Six:
Hundreds of millions of years later, the planets settled into stable orbits—the same orbits that they follow today. The bits of stuff left over ended up either in the asteroid belt between Mars and Jupiter, or much farther out beyond Pluto in the Kuiper belt.
Are There Other Solar Systems Like Ours?
An
exoplanet
is a planet in
orbit around a
star other than
the Earth’s
Sun.
For several hundred years astronomers suspected that other stars in the Universe might have planets in orbit around them. However, the first exoplanet was not confirmed until 1992, orbiting the corpse of a massive star. The first planet around a real, brightly shining star was discovered in 1995. Since then, more than four hundred exoplanets have been discovered—some around stars very similar to our Sun!
This is just the beginning. Even if only 10% of the stars in our Galaxy had planets in orbit around them, that would still mean more than two hundred billion solar systems within the Milky Way alone.
Some of these may be similar to our Solar System. Others might look very different. Planets in a binary solar system, for example, might see two suns rise and set in the sky. Knowing the distance from their star to the planets—and the size and age of the star—helps us to calculate how likely it is that we might find life on those planets.
Most of the exoplanets we know about in other solar systems are huge—as big as Jupiter or larger—mainly because those are easier to detect than smaller planets. But astronomers are beginning to discover smaller, rocky planets orbiting at the right distance from their star that might be more like planet Earth.
In early 2011, NASA confirmed their Kepler mission had spotted an Earth-like planet around a star five hundred light-years away! At only 1.4 times the size of our home planet, this new planet, Kepler 10-b, may be the most similar to Earth we have found so far.
Chapter Two
“But I don’t think Freddy could actually live on any of those planets,” objected George after they had looked through Cosmos’s tour of the Solar System for pigs. “He’d boil on Mercury, get blown away on Neptune, or sink through layers of poisonous gas on Saturn. He’d probably wish he was back on the farm.”
“Except for on Earth … ,” murmured Annie. “That’s the only planet in our Solar System that’s suitable for life.” Her nose was scrunched up, meaning she was thinking hard. “It’s just like for humans,” she said suddenly. “You know how my dad was talking about finding a new home for human beings, in case our planet becomes uninhabitable?”
“You mean, if we get struck by a huge comet or global warming takes over?” said George. “We won’t be able to live
on this planet if there are volcanic eruptions or it becomes a huge, dry desert.” George knew all about the frightening things that might happen to planet Earth if humans didn’t start taking better care of it from his eco-activist parents.
PROBLEMS FACING OUR PLANET
ASTEROID ATTACK!
Asteroids
typically range in
size from as little
as a few yards to
hundreds of miles
across.
An asteroid is a rocky fragment left over from the formation of the Solar System about 4.6 billion years ago. Scientists estimate there are probably millions of asteroids in our Solar System.
Once in a while an asteroid will get nudged out of its orbit—for example by the gravity of nearby planets—possibly sending it on a collision course with the Earth.
Around once a year, a rock the size of a family car crashes into the Earth’s atmosphere but burns up before it reaches the surface.
Once every few thousand years, a chunk of rock about the size of a football field hits the Earth, and every few million years, Earth suffers an impact from a space object—an asteroid or a comet—large enough to threaten civilization.
If an asteroid or a comet—a rocky ice ball that slingshots around the Sun—were to hit the surface of the Earth, it is possible that it could crash through the surface, releasing a flood of volcanic eruptions. Nothing would survive the impact.
A meteoroid is a chunk of rock that flies through our Solar System; a meteorite is what you call that piece of rock if it lands on the Earth.
Sixty-five million years ago, an asteroid smashed into the Earth. This could be what wiped out the dinosaurs—the impact sent up a cloud of fine dust, which blocked out the sunlight, dooming the dinosaurs and many other species to extinction.
PROBLEMS FACING OUR PLANET
GAMMA RAY BURST … GAME OVER!
We also face the exotic threat of extinction by gamma rays from space.
When very massive stars reach the ends of their lives and explode, they not only send hot dust and gas across the cosmos in an expanding cloud. They also shoot out deadly twin beams of gamma rays, like lighthouse beams. If the Earth were directly in the path of such a beam, and if the gamma-ray burst happened close enough to us, the beam could rip our atmosphere apart, causing clouds of brown nitrogen to fill the skies.