George's Cosmic Treasure Hunt Read Free Page A

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?”
    â€œA black hole, of course!” said George. “You swallow anything that comes near you, you greedy pig.”
    â€œNope!” said Annie triumphantly. “I knew you’d say that, but that’s wrong! I am”—she looked very pleased with herself—“dark matter.”
    â€œWhat’s that?” asked George.
    â€œNo 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?”
    â€œUm, well,” said George. “I’m the Man from Mars—y’know, from the pictures.”
    â€œOh 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 arocket. 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.
    â€œAnnie,” said George urgently, “I don’t understand any of these costumes. What have these guests come as?”
    â€œUm, well, they’ve all come as things you’d find in space, if you know how to look for them,” said Annie.
    â€œLike what?” asked George.
    â€œWell, like the man dressed in red,” explained Annie. “He keeps stepping away from people, which means he’s pretending to be the redshift.”
    â€œThe what?”
    â€œIf 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.”

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    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.
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    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.
    Light travels at 186,000 miles per second. This is very fast, but light from the Sun still takes eight