It hadn’t been easy to decide what to wear. “Come as your favorite space object,” he’d been told by Eric Bellis, the scientist next door, who had invited George to his costume party. The problem was, George had so many favorite outer-space objects, he hadn’t known which one to pick.
Should he dress up as Saturn with its rings?
Perhaps he could go as Pluto, the poor little planet that wasn’t a planet anymore?
Or should he go as the darkest, most powerful force in the Universe—a black hole? He didn’t think too long or hard about that—as amazing, huge, and fascinating as black holes are, they didn’t really count as his favorite space objects. It would be quite hard to get fond of something that was so greedy, it swallowed up anything and everything that came too close, including light.
In the end George had his mind made up for him. He’d been looking at images of the Solar System on the Internet with his dad when they came across a picture sent back from a Mars rover, one of the robots exploring the planet’s surface. It showed what looked like a person standing on the red planet. As soon as he saw the photo, George knew he wanted to go to Eric’s party as the Man from Mars. Even George’s dad, Terence, got excited when he saw it. Of course, they both knew it wasn’t really a Martian in the picture—it was just an illusion caused by a trick of the light that made a rocky outcrop look like a person. But it was exciting to imagine that we might not be alone in this vast Universe after all.
“Dad, do you think there is anyone out there?” asked George as they gazed at the photo. “Like Martians or beings in faraway galaxies? And if there are, do you think they might come to visit us?”
“If there are,” said his dad, “I expect they’re looking at us and wondering what we must be like—to have this beautiful, wonderful planet and make such a mess of it. They must think we’re really stupid.” He shook his head sadly.
Both George’s parents were eco-warriors on a mission to save the Earth. As part of their campaign, electrical gadgets like telephones and computers had been banned from the house. But when George had won the first prize in the school science competition—his very own computer—his mom and dad didn’t have the heart to say he couldn’t keep it.
In fact, since they’d had the computer in the house, George had shown them how to use it and had even helped them put together a very snappy virtual ad featuring a huge photo of Venus. WHO WOULD WANT TO LIVE HERE? it said in big letters. Clouds of sulfuric acid, temperatures of up to 878 degrees Fahrenheit (470 degrees Celsius)...The seas have dried up and the atmosphere is so thick, sunlight can’t break through. This is Venus. But if we’re not careful, this could be Earth. Would you want to live on a planet like this? George was very proud of the poster, which his parents and their friends had e-mailed all around the world to promote their cause.
Venus is the brightest object in the sky, after the Sun and the Moon. Named after the Roman goddess of beauty, Venus has been known since prehistoric times. Ancient Greek astronomers thought it was two stars: one that shone in the morning, Phosphorus, the bringer of light; and one in the evening, Hesperus, until Greek philosopher and mathematician Pythagoras realized they were one and the same object.
But Venus is a very different world from the Earth.
It has a very thick, toxic atmosphere, mostly made of carbon dioxide with clouds of sulfuric acid. These clouds are so dense that they trap heat, making Venus the hottest planet in the Solar System, with surface temperatures of up to 878 degrees Fahrenheit (470 degrees Celsius)—so hot that lead would melt there. The pressure of the atmosphere is ninety times greater than Earth’s. This means that if you stood on the surface of Venus, you would feel the same pressure as you would at the bottom of a very deep ocean on Earth.
The dense spinning clouds of Venus don’t just trap the heat. They also reflect the light of the Sun, which is why the planet shines so brightly in the night sky. Venus may have had oceans in the past, but the water was vaporized by the greenhouse effect and escaped from the planet.
Some scientists believe that the runaway greenhouse effect on Venus is similar to conditions that might prevail on Earth if global warming isn’t checked.
Since Mariner 2 in 1962, Venus has been visited by space probes more than twenty times. The first space probe ever to land on another planet was the Soviet Venera 7, which landed on Venus in 1970; Venera 9 sent back photos of the surface—but it didn’t have long to do it: The space probe melted after just sixty minutes on the hostile planet! The U.S. orbiter, Magellan, later used radar to send back images of the surface details of Venus, which had previously been hidden by the thick clouds of its atmosphere.
Venus rotates in the opposite direction from the Earth! If you could see the Sun through its thick clouds, it would rise in the west and set in the east. This is called retrograde motion; the direction in which the Earth turns is called prograde.
A year on Venus takes less time than a day there! Because Venus turns so slowly, it revolves all the way around the Sun in less time than it takes to rotate once on its axis.
Venus passes between the Earth and the Sun about twice a century. This is called the transit of Venus. These transits always happen in pairs eight years apart. Since the telescope was invented, transits have been observed in 1631 and 1639; 1761 and 1769; and 1874 and 1882. On June 8, 2004, astronomers saw the tiny dot of Venus crawl across the Sun; the second in this pair of early twenty-first-century transits will occur on June 6, 2012.
- Venus is the second planet from the Sun and the sixth largest in the Solar System.
- Venus is often called Earth’s twin. It is about the same size, mass, and composition as the Earth.
- Venus is thought to be the least likely place in the Solar System for life to exist.
- One year on Venus = 224.7 Earth days
- Venus spins on its axis once every 243 Earth days.
Given what he knew about Venus, George felt pretty sure that there wasn’t any life to be found on that smelly, hot planet. He didn’t even consider going to Eric’s party dressed as a Venusian. Instead, he got his mom, Daisy, to help him with an outfit of dark-orange bobbly knitted clothes and a tall pointy hat so he looked just like the photo of the “Martian” they’d found.
Wearing his costume, George waved good-bye to his parents—who had a big evening planned helping some eco-friends make organic treats for a party of their own—and squeezed through the gap in the fence between his garden and Eric’s. The gap had come about when George’s pet pig (given to him by his gran), Freddy, had escaped from his pigsty, barged through the fence, and broken into Eric’s house via the back door. Following the trail of hoofprints that Freddy had left behind him, George had ended up meeting his new neighbors, who had only just moved into the empty house next door. This chance encounter with Eric and his family had changed George’s life forever.
Eric had shown George his amazing computer, Cosmos, who was so smart and so powerful that he could draw doorways through which Eric; his daughter, Annie; and George could walk, to visit any part of the known Universe.
But space can be very dangerous, as George found out when one of their space adventures ended with Cosmos exploding from the sheer effort of mounting the rescue mission.
Since Cosmos had stopped working, George hadn’t had another chance to step through the doorway and travel around the Solar System and beyond. He missed Cosmos, but at least he had Eric and Annie. He could see them anytime he wanted, even if he couldn’t go on adventures into outer space with them.
George scampered up the garden path to Eric’s back door. The house was brightly lit, with chatter and music pouring out. Opening the door, George let himself into the kitchen.
He couldn’t see Annie, Eric, or Annie’s mom, Susan, but there were lots of other people milling about: one grown-up immediately pushed a plate of shiny silver-iced muffins under his nose. “Have a meteorite!” he said cheerfully. “Or perhaps I should say, have a meteoroid!”
“Oh...um, well, thanks,” said George, a bit startled. “They look delicious,” he added, helping himself to one.
“If I did this,” continued the man, tipping some of the muffins onto the floor, “then I could say, ‘Have a meteorite!’ because then they would have hit the ground. But when I offered them to you, suspended in the air, they were—technically—still meteoroids.” He beamed at George and then at the muffins that were lying in a pile on the floor. “You get the distinction—a meteoroid is a chunk of rock that flies through the air; a meteorite is what you call that piece of rock if it lands on the Earth. So now I’ve dropped them on the floor, we can call them meteorites.”
With the muffin in his hand, George smiled politely, nodded, and started backing away slowly.
“Ouch!” He heard a squeak as he trod on someone behind him.
“Oops!” he said, turning around.
“It’s okay, it’s only me!” It was Annie, dressed all in black. “You couldn’t have seen me, anyway, because I’m invisible!” She swiped the muffin out of George’s hand and stuffed it into her mouth. “You only know I’m here because of the effect I have on objects around me. What does that make me?”
“A black hole, of course!” said George. “You swallow anything that comes near you, you greedy pig.”
“Nope!” said Annie triumphantly. “I knew you’d say that, but that’s wrong! I am”—she looked very pleased with herself—“dark matter.”
“What’s that?” asked George.
“No one knows,” said Annie mysteriously. “We can’t see it, but it seems to be absolutely essential to keep galaxies from flying apart. What are you?”
“Um, well,” said George. “I’m the Man from Mars—y’know, from the pictures.”
“Oh yeah!” said Annie. “You can be my Martian ancestor. That’s cool.”
Around them, the party was buzzing. Groups of the most oddly dressed grown-ups stood eating and drinking and talking at the tops of their voices. One man had come dressed as a microwave oven, another as a rocket. There was a lady wearing a badge shaped like an exploding star and a man with a mini satellite dish on his head. One scientist was bouncing around in a bright green suit, ordering people to “Take me to your leader”; another was blowing up an enormous balloon stamped with the words THE UNIVERSE IS INFLATING. A man dressed all in red kept standing next to people and then stepping away from them, daring them to guess what he was. Next to him was a scientist wearing lots of different-sized hula hoops around his middle, each one with a different-sized ball attached to it. When he walked, his hula hoops all spun around him.
“Annie,” said George urgently, “I don’t understand any of these costumes. What have these guests come as?”
“Um, well, they’ve all come as things you’d find in space, if you know how to look for them,” said Annie.
“Like what?” asked George.
“Well, like the man dressed in red,” explained Annie. “He keeps stepping away from people, which means he’s pretending to be the redshift.”
“If a distant object in the Universe, like a galaxy, is moving away from you, its light will appear more red than otherwise. So he’s dressed in red, and he is moving away from people to show them he’s come as the redshift. And the others have come as all sorts of cosmic stuff that you’d find out there, like microwaves and faraway planets.”
LIGHT AND HOW IT TRAVELS THROUGH SPACE
One of the most important things in the Universe is the electromagnetic field. It reaches everywhere; not only does it hold atoms together, but it also makes tiny parts of atoms (called electrons) bind different atoms together or create electric currents. Our everyday world is built from very large numbers of atoms stuck together by the electromagnetic field. Even living things, like human beings, rely on it to exist and to function.
Jiggling an electron creates waves in the field. This is like jiggling a finger in your bath and making ripples in the water. These waves are called electromagnetic waves, and because the field is everywhere, the waves can travel far across the Universe, until stopped by other electrons that can absorb their energy. They come in many different types, but some affect the human eye, and we know these as the various colors of visible light. Other types include radio waves, microwaves, infrared, ultraviolet, X rays, and gamma rays. Electrons are jiggled all the time by atoms that are constantly jiggling too, so there are always electromagnetic waves being produced by objects. At room temperature the waves are mainly infrared, but in much hotter objects the jiggling is more violent, and produces visible light.
Very hot objects in space, such as stars, produce visible light, which may travel a very long way before hitting something. When you look at a star, the light from it may have been moving serenely through space for hundreds of years. It enters your eye and, by jiggling electrons in your retina, turns into electricity that is sent along the optic nerve to your brain. Your brain says, “I can see a star!” If the star is very far away, you may need a telescope to collect enough of the light for your eye to detect, or the jiggled electrons could instead create a photograph or send a signal to a computer.
The Universe is constantly expanding, inflating like a balloon. This means that distant stars and galaxies are moving away from Earth. This stretches their light as it travels through space toward us—the farther it travels, the more stretched it becomes. The stretching makes visible light look redder, which is known as the redshift. Eventually, if light traveled and redshifted far enough, the light would no longer be visible and would become first infrared, and then microwave (as used on Earth in microwave ovens), radiation. This is just what has happened to the incredibly powerful light produced by the Big Bang. After thirteen billion years of traveling, it is detectable today as microwaves coming from every direction in space. This has the grand title of cosmic microwave background radiation, and is nothing less than the afterglow of the Big Bang itself.
- Light travels at 186,000 miles per second. This is very fast, but light from the Sun still takes eight minutes to reach us; from the next nearest star it takes more than four years.
Annie said all this matter-of-factly, as though it were quite normal to know this kind of information and be able to rattle it off at parties. But once again George felt a little jealous of her. He loved science and was always reading books, looking up articles on the Internet, and pestering Eric with questions. He wanted to be a scientist when he grew up, so he could learn everything there was to know and maybe make some amazing discovery of his own. Annie, on the other hand, was much more casual about the wonders of the Universe.
When George had first met Annie, she’d wanted to be a ballerina, but now she’d changed her mind and decided on being a soccer player. Instead of spending her time after school in a pink-and-white tutu, she now charged around the backyard, hammering a soccer ball past George, who always had to be goalie. And yet she still seemed to know far more about science than he did.
Annie’s dad, Eric, now appeared, dressed in his normal clothes and looking no different from usual.
“Eric,” cried George, who was bursting with questions. “What have you come as?”
“Oh, me?” Eric smiled. “I’m the only intelligent life-form in the Universe,” he said modestly.
“What?” asked George. “You mean you’re the only intelligent person in the whole Universe?”
Eric laughed. “Don’t say that too loudly around here,” he told George, gesturing to all the other scientists. “Otherwise people will get very upset. I meant, I’ve come as a human being, which is the only intelligent form of life in the Universe that we know about. So far.”
“Oh,” said George. “But what about all your friends? What have they come as? And why does red light mean something is going away? I don’t understand.”
“Well,” said Eric kindly, “you’d understand if someone explained it to you.”
“Can you explain it to me?” pleaded George. “All about the Universe? Like you did with the black holes? Can you tell me about red thingies and dark matter and everything else?”
“Oh dear,” said Eric, sounding rather regretful. “George, I’d love to tell you all about the Universe, but the problem is, I’m just not sure I’ll have time before I have to...Hang on a second...” He trailed off and gazed into the distance, the way he did when he was having an idea. He took off his glasses and polished them on his shirt, setting them on his nose at the same off-kilter angle as before. “I’ve got it!” he cried, sounding very excited. “I know what we need to do! Hold on, George, I’ve got a plan.”
With that, he picked up a soft hammer and struck a huge brass gong, which rang out with a deep, humming chime.
“Right, gather round, everyone,” said Eric, waving everyone into the room. “Come on, come on, hurry up! I’ve got something to say.”
A ripple of excitement went through the crowd.
“Now then,” he went on, “I’ve gathered the Order of Science here today for this party—”
“Hurray!” cheered someone at the back.
“And I want us to put our minds to some questions my young friend George has asked me. He wants to know all sorts of things! For a start, I’m sure he’ll want to know what your costume is!” He pointed to the man wearing the hula hoops.
“I’ve come to the party,” piped up the cheerful-looking scientist, “as a distant planetary system where we might find another planet Earth.”
“Annie,” whispered George, “isn’t that what Doctor Reeper did? Find new planets?”
Dr. Reeper was a former colleague of Eric’s, who wanted to use science for his own selfish purposes. He had told Eric he’d found an exoplanet—that is, a planet in orbit around a star other than the Earth’s Sun—that might be able to support human life. But the directions he’d given Eric had been bogus—in fact, in his search for the planet, they had sent Eric dangerously close to a black hole. Dr. Reeper had been trying to get rid of Eric so he could control Cosmos, Eric’s supercomputer. But his evil trick hadn’t worked, and Eric had returned safely from his trip inside a black hole.
No one knew where Dr. Reeper was now. He had fled after his master plan backfired. At the time, George had begged Eric to do something about him, but Eric had just let him go.
“Doctor Reeper knew how to look for planets,” said Annie, “but we don’t know whether he ever actually found one. After all, that planet he wrote about in the letter to Dad? We never got to see whether it really existed or not.”
“Thank you, Sam. And how many planets have you found so far?” Eric questioned the hula hoop man.
“So far,” replied Sam, shaking his hoops as he spoke, “more than seven hundred exoplanets—more than a hundred of them in orbit around stars quite nearby. Some of these stars have more than one planet going around them.” He pointed to his hula hoops. “I’m a nearby system with planets in orbit around its star.”
“What does he mean by ‘nearby’?” George whispered to Annie, who passed the message on to Eric. Her father whispered back to her, and she then relayed the answer to George.
“He means, maybe, like, about forty light-years away. So, like, about two hundred and thirty-five trillion miles,” said Annie. “Nearby for the Universe!”
“Have you seen anything that might be like the Earth? A planet we could call home?”
“We’ve seen a few that might—and only might—be like a second Earth. Our planet-hunting search continues.”
“Thank you, Sam,” said Eric. “Now, what I want us to do is answer George’s questions—all of us. Each of you”—he handed out pens and paper—“can write me a page or two by the end of the party about what you think is the most interesting part of the science you work on. You can send or e-mail it to me later if you don’t have time to finish it now.”
The scientists all looked really happy. They loved talking about the most interesting parts of their work.
“And,” added Eric quickly, “before we get back to the party, I’ve got one more brief announcement to make—one of my own this time. I’m very excited and pleased to tell you all that I have a new job! I’m going to work for the Global Space Agency, looking for signs of life in our Solar System. Beginning with Mars!”
“Wow!” said George. “That’s amazing!” He turned to Annie, but she didn’t meet his eye.
“So,” continued Eric, “in just a few days’ time, my family and I will be packing up...and moving to the headquarters of the Global Space Agency in the United States of America!”
With that, George’s universe imploded.