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

by Editors of Scientific American

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!

Product Details

ISBN-13:	9780061753602
Publisher:	HarperCollins Publishers
Publication date:	12/15/2023
Sold by:	Barnes & Noble
Format:	eBook
Pages:	288
Sales rank:	960,857
File size:	800 KB

Read an Excerpt

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

Celestial Bodies

Astronomy

It Came From Outer Space
asteroids, meteors, and comets

---

How crowded is the asteroid belt?

Answered by:

Tom Gehrel, University of Arizona, Tuscon, Arizona. A veteran asteroid hunter, he and his colleagues find roughly 20,000 objects a year -- many of them uncatalogued asteroids -- using the Spacewatch Telescope on Kitt Peak.

---

Some scientists were seriously concerned about the possible high density of objects in the asteroid belt, which lies between the orbits of Mars and Jupiter, when the first robotic spacecraft were scheduled to be sent through it. The first crossing of the asteroid belt took place in the early 1970s, when the Pioneer 10 and Pioneer 11 spacecraft journeyed to Jupiter and beyond. The danger does not lie in the risk of hitting a large object. In fact, such a risk is minuscule because there is a tremendous amount of space between Mars and Jupiter and because the objects there are very small in relation. Even though there are perhaps a million asteroids larger than one kilometer in diameter, the chance of a spacecraft not getting through the asteroid belt is negligible.

Even if there were 100,000 sizable asteroids (more than a few kilometers in size) in the asteroid belt -- and the real number is quite likely about 10 times less-- the average separation between them would be about five million kilometers. That is more than 10 times the distance between the earth and the moon. If you were standing on one of those asteroids and looked up, you would not see a sky full of asteroids; your neighbors would appear so small and dim that you would be quite lucky to even see one, let alone hundreds.

In some ways, the asteroid belt is actually emptier than we might like. In the early 1990s, the National Aeronautics and Space Administration wanted the Galileo space-craft to encounter an asteroid while it was passing through the asteroid belt on its way to Jupiter. But it took some effort to find an object that was located even roughly along Galileo's path. Special targeting was required to reach this object, but the result was the first close-up view of an asteroid, the one called Gaspra.

The number of objects in the asteroid belt increases steeply with decreasing size, but even at micrometer sizes the Pioneer spacecraft were hit only a few times during their passage. That is not to say that asteroids cannot pose any danger, however. It is worth noting that for a large planet like Earth, over a long period of time, there is an appreciable chance of being hit. This hazard comes from the fragments of mutual collisions in the asteroid belt; after their break-up, some of these fragments move toward the earth under the gravitational action of Jupiter.

An asteroid about 12 kilometers in diameter crashed into the earth 65 million years ago, killing nearly 90 percent of the animals, including the dinosaurs. Such major impacts are very rare events, but for smaller objects the likelihood of impact increases; the chance of the earth being struck by an object approximately one kilometer in size is about one in 5,000 in a human lifetime. An object one kilometer across would still be large enough to cause a global disaster because of the enormous energy it would release upon impact:at east a million times the energy of the bomb dropped on Hiroshima in 1945.

---

What causes a meteor shower?

Answered by:

Gregory A.Lyzenga,Professor of Physics, Harvey Mudd College,Claremont,California.

---

Meteor showers occur when the earth in its orbit around the sun passes through debris left over from the disintegration of comets. Although the earth's orbit around the sun is a most circular, most comets travel in orbits that are highly elongated ellipses. As a result, some comets have orbits that intersect or partially overlap the earth's path.

Because a comet's nucleus is made up of a combination of icy materials and loosely consolidated "dirt," when a comet is heated by passing close to the sun, it more or less slowly disintegrates, producing the visible tail. The rocky debris, consisting of mostly sand-size particles, continues in an elongated orbit around the sun close to that of its parent comet. When the earth intersects this orbit in its annual trip, it can run into this debris, which burns up on entry into the earth's atmosphere, producing a visible shower of meteors.

Meteor showers associated with particular comet orbits occur at about the same time each year, because it is at those points in the earth's orbit that the collisions occur. However, because some parts of the comet's path are richer in debris than others, the strength of a meteor shower may vary from one year to the next. Typically a meteor shower will be strongest when the earth crosses the comet's path shortly after the parent comet has passed.

---

Is it possible that a meteorite could strike a commercial airliner and cause it to explode?

Answered by:

David Morrison,NASA Ames Research Center, Maffett Field,California.

---

It is certainly possible, a though the probability is low. We can make a very rough estimate by comparing the area of airliners with the area of cars in the United States.A typical car has an area on the order of 10 square meters, and there are roughly 100 million cars in the United States, for a total area of about 1,000 square kilometers. The typical airliner has a cross-sectional area of several hundred square meters, but the number of planes is much smaller than the number of cars, perhaps a few thousand.The total area of airliners is therefore no more than 10 square kilometers, or a factor of at least 100 less than that of cars. Three cars are known to have been struck by meteorites in the United States during the past century...

Scientific American's Ask the Experts
Answers to The Most Puzzling and Mind-Blowing Science Questions. Copyright © by Scott Editors of Scientific American. Reprinted by permission of HarperCollins Publishers, Inc. All rights reserved. Available now wherever books are sold.

Table 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
	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
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
	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
	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
	Do humans have some kind of homing instinct like certain birds do?	105
	Why do we yawn when we are tired? And why does it seem to be contagious?	107
	You Haven't Aged a Bit: growing older
	Why does hair turn gray?	109
	Do people lose their senses of smell and taste as they age?	111
	Anatomy 101: the human body
	What is the function of the human appendix?	113
	What makes the sound when we crack our knuckles?	115
	Why does your stomach growl when you are hungry?	118
	How can you live without one of your kidneys?	120
	Why do fingers wrinkle in the bath?	122
	If the cells of our skin are replaced regularly, why do scars and tattoos persist indefinitely?	124
	Why does fat deposit on the hips and things of women and around the stomachs of men?	125
	The Dr. Is In: health and medicine
	Why do hangovers occur?	128
	Why does reading in a moving car cause motion sickness?	130
	Why do we get the flu more often in the winter than in other seasons?	132
	What happens when you get a sunburn?	134
	There are many kinds of cancer, so why is there no heart cancer?	136
	Is there any proof that Alzheimer's disease is related to exposure to aluminum--for instance, by using aluminum frying pans?	138
	How long can the average person survive without water?	139
4	As a Matter of Fact: Chemistry
	Elementary, My Dear Watson ...: the elements
	Why doesn't stainless steel rust?	141
	If nothing sticks to Teflon, how does it stick to pans?	143
	What determines whether a substance is transparent?	144
	If You Can't Stand the Heat, Get Out of the Kitchen! everyday chemistry
	Why do my eyes tear when I peel an onion?	145
	Why do spicy (or "hot") foods cause the same physical reactions as heat?	148
	Why does bruised fruit turn brown?	150
	How is caffeine removed to produce decaffeinated coffee?	151
	What is the difference between artificial and natural flavors?	153
	How can an artificial sweetener contain no calories?	155
	Do vitamins in pills differ from those in food?	157
	Where There's Smoke, There's a Fire: more chemistry
	How does a flame behave in zero gravity?	159
	How does fingerprint powder work?	161
5	There's No Place Like Home: Earth Science
	Everybody Talks About It ...: weather
	Why do clouds float when they have so much water in them?	163
	What causes thunder?	165
	Why are snowflakes symmetrical?	167
	Why are some rainbows bigger than others?	168
	What is the meaning of the phrase, "It is too cold to snow"? Doesn't it have to be cold for it to snow?	170
	Why do hurricanes hit the East Coast of the United States but never the West Coast?	171
	Up Above: the atmosphere
	If chlorofluorocarbons are heavier than air, how do they reach the ozone layer?	173
	What determines the shape of a mushroom cloud after a nuclear explosion?	174
	The Upper Crust: earth's surface and below
	How do volcanoes affect world climate?	175
	Where do geysers get their water from?	179
	How do scientists measure the temperature of the earth's core?	182
	What causes the regular, wavelike shapes that form in the sand on beaches?	184
	What is quicksand?	186
	Let's Get Wet: oceans
	How did the oceans form?	188
	Why does the ocean appear blue? Is it because it reflects the sky?	190
6	Count on Me: Mathematics and Computers
	Much Ado About Nothing: zero
	What is the origin of zero?	191
	Give 'Em an Inch measurement
	On average, how many degrees apart is any one person in the world from another?	193
	Where does the measurement of the "meter" come from?	195
	How does a laser measure the speed of a car?	197
	Does Not Compute computers
	Why do computers crash?	199
	How do Internet search engines work?	201
	How do rewritable CDs work?	203
	When did the term "computer virus" arise?	205
7	Let's Get Physical: Physics
	Let There Be Light: light
	How do surfaces, such as pavement, become heated from the sun?	207
	What is the physical process by which a mirror reflects light rays?	208
	How does sunscreen protect the skin?	210
	Why are sunsets orange?	212
	I'm Very Particular particles
	If we cannot see electrons and protons, or smaller particles such as quarks, how can we be sure they exist?	213
	Is glass really a liquid?	215
	Now Hear This sound
	How can the extremity of a whip travel faster than the speed of sound to produce the characteristic "crack"?	216
	What causes the noise emitted from high-voltage power lines?	217
	What are "booming sands" and what causes the sounds they make?	219
	What happens when an aircraft breaks the sound barrier?	221
	In Theory: theoretical physics
	Is it theoretically possible to travel through time?	223
	Is dark matter theory or fact?	227
	Would you fall all the way through a theoretical hole in the earth?	230
	What is antimatter?	232
	Does the speed of light ever change?	234
	You Won't Believe Your Eyes the physics of seeing
	Why do beautiful bands of color appear in the tiny oil slicks that form on puddles?	236
	Why is it that when you look at the spinning propeller of a plane or fan, at a certain speed, the blades seem to move backward?	237
	Why do jets leave a white trail in the sky?	239
	Shake It Up everyday physics
	Does hot water freeze faster than cold water?	241
	How does a microwave oven cook foods?	243
	Why does shaking a can of coffee cause the larger grains to move to the surface?	244
	Why does a shaken soda fizz more than an unshaken one?	246
	Bottom of the 9th, Bases Loaded: the physics of baseball
	What makes a knuckleball appear to flutter?	248
	Why does a ball go farther when hit with an aluminum bat?	250