Scientific American's Ask the Experts: Answers to The Most Puzzling and Mind-Blowing Science Questions

290 Pages·2003·2.6 MB·English

by  Editors Of Scientific American

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Answers to the Most
Puzzling and Mind-Blowing
Science Questions
Scientific American’s
ASK THE EXPERTS
by the editors of
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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
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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
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2
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
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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? 66
Do unbred animals lack the individual distinctiveness
of humans? 69
Talkin’ About Evolution
evolution
Is there any evolutionary advantage to gigantism? 71
What is the point in preserving endangered
species that have no practical use to humans? 74
What do we know about the evolution of sleep? 76
When Dinosaurs Ruled the Earth
dinosaurs
What are the odds of a dead dinosaur becoming
fossilized? 78
What kind of evidence could be found in the
fossil record (or anywhere else) that would prove
whether some dinosaurs were warm-blooded? 80
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How close are we to being able to clone a dinosaur? 84
Did any dinosaurs have poisonous saliva,
as in Jurassic Park? 85
If T. rex fell, how did it get up, given its tiny
arms and low center of gravity? 86
3
Being Human
It’s All in the Genes
human evolution
Is the human race still evolving? Isn’t culture
a more powerful force? 89
Can the human race be devolving? 92
Why are we getting taller as a species? 94
Why do men have nipples? 96
Oh, Behave!
human behavior
How did the smile become a friendly
gesture in humans? 99
Why are more people right-handed?
Do other primates show a similar tendency
to favor one hand over the other? 100
How long can humans stay awake? 103