E-Book Overview
Why is the night sky dark? How do dolphins sleep without drowning? Why do hangovers occur? Will time travel ever be a reality? What makes a knuckleball appear to flutter? Why are craters always round? There's only one source to turn to for the answers to the most puzzling and thought-provoking questions about the world of science: Scientific American. Writing in a fun and accessible style, an esteemed team of scientists and educators will lead you on a wild ride from the far reaches of the universe to the natural world right in your own backyard. Along the way, you'll discover solutions to some of life's quirkiest conundrums, such as why cats purr, how frogs survive winter without freezing, why snowflakes are symmetrical, and much more. Even if you haven't picked up a science book since your school days, these tantalizing Q & A's will shed new light on the world around you, inside you, below you, above you, and beyond!
E-Book Content
? Answers to the Most Puzzling and Mind-Blowing Science Questions Scientific American’s ASK THE EXPERTS by the editors of Contents 1 Celestial Bodies ASTRONOMY It Came From Outer Space asteroids, meteors, and comets How crowded is the asteroid belt? 1 What causes a meteor shower? 4 Is it possible that a meteorite could strike a commercial airliner and cause it to explode? 5 Why are impact craters always round? 6 Heavenly Bodies planets and moons What defines a true planet, and why might Pluto not qualify? 8 Why do the moon and the sun look so much larger near the horizon? 11 vi Contents What is a blue moon? 13 Why are planets round? 14 How do scientists measure the weight of a planet? 15 How fast is the earth moving? 17 Why and how do planets rotate? 19 Star Light, Star Bright stars What exactly is the North Star? 21 How long do stars usually live? 23 Why do stars twinkle? 25 Far, Far Away . . . the universe How do we know our location within the Milky Way galaxy? 26 Why is the night sky dark? 28 Does the fact that the universe is continually expanding mean that it lacks a physical edge? 31 Contents 2 vii It’s Alive! BIOLOGY The Grass Is Always Greener plants What causes the leaves on trees to change color in the fall? 35 How does the Venus flytrap digest flies? 37 How do trees carry water from the soil around their roots to the leaves at the top? 39 Creepy Crawlers insects How is bug blood different from our own? 41 What kind of illnesses do insects get? 43 How do flies and other insects walk up walls? 44 Why is spider silk so strong? 45 If a used needle can transmit HIV, why can’t a mosquito? 46 Under the Sea ocean life How do squid and octopuses change color? 47 Why do some fish normally live in freshwater and others in saltwater? How can some fish adapt to both? 50 How can sea mammals drink saltwater? 53 viii Contents How do deep-diving sea creatures withstand huge pressure changes? 56 How do whales and dolphins sleep without drowning? 57 That’s a Horse of a Different Color animal kingdom Do hippopotamuses actually have pink sweat? 61 Why do cats purr? 62 Why do dogs get blue, not red, eyes in flash photos? 64 How do frogs survive winter? Why don’t they freeze to death?