Bad Astronomy: Misconceptions and Misuses Revealed, from ...

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METEORS, METEOROIDS, AND METEORITES, OH MY! 135 it might eventually cross paths with the Earth. When that happens, we might see a single bright meteor flash across the sky. Since the bits of meteoroid may be coming from any random direction in space, we see them come from any random point in the sky, traveling in a random direction. We call these sporadic meteors. Cometary meteors are different. Comets are about the same size as asteroids but have a different composition. Instead of being mostly rock or metal, comets are more like frozen snowballs; rocks (from pebble size to kilometers across) held together by frozen material like water, ammonia, and other ices. When a comet gets near the Sun, the ice melts, and little bits of rock can work loose. This type of debris stays in roughly the same orbit as the comet for a long time. Not forever, though, because the orbit can be affected by the gravity of nearby planets, the solar wind, and even the pressure of light from the Sun. But the debris orbits are generally similar to that of the parent comet. When the Earth plows through a ribbon of this meteoroidal debris, we see not one but many meteors. Usually it takes a few hours or nights to go all the way across the debris path, so we get what are called meteor showers—like a rain of meteors. We pass through the same debris ribbons every year at about the same time, so showers are predictable. For example, every year we pass through the orbital debris of the comet Swift Tuttle, and we see a meteor shower that peaks around August 12 or 13. Meteor showers create an odd effect. Imagine driving a car through a tunnel that has lights all around the inside. As you pass them, the lights all seem to be streaking outward from a point ahead of you in the tunnel. It’s not real, since the lights are really all around you, but an effect of perspective. The same thing happens with meteor showers. The Earth’s orbit intersects the meteoroid stream at a certain angle, and that doesn’t change much from year to year. Like the lights in the tunnel, the meteors flash past you from all over the sky, but if you trace the path of every meteor backwards, they all point to one spot called the radiant. This point comes from a combination of the direction the Earth is headed in space and the motion of the meteoroids themselves. The radiant is almost literally the light at the end of the tunnel.
136 SKIES AT NIGHT ARE BIG AND BRIGHT So the meteor shower I mentioned above not only recurs in time but in space, too. Every August those meteors appear, and they seem to flash out of the sky from the direction of the constellation Perseus. Showers are named after their radiant, so this one is called the Perseids. One of the most famous showers comes from the direction of Leo every November. The Leonids are interesting for two reasons: One is that, relative to us, the parent comet orbits the Sun backwards. That means we slam into the meteoroid stream head-on. The meteoroids’ velocity adds to ours, and we see the meteors flash across our sky particularly quickly. The second interesting thing is that the meteoroid stream is clumpy. The comet undergoes bursts of activity every time it gets near the Sun (every 33 years or so), and this ejects lots of bits of debris. When we pass through these concentrated regions, we see not just dozens or hundreds of meteors an hour but sometimes thousands or even tens of thousands. This is called a meteor storm. The celebrated storm of 1966 had hundreds of thousands of meteors an hour, which means, had you been watching, you would have seen many meteors whizzing by every second. It must have really seemed as if the sky were falling. So that’s why we get meteors. But why are they so bright? Almost everyone thinks it’s friction—our atmosphere heating them up, causing them to glow. Surprise! That answer is wrong. When the meteoroid enters the upper reaches of the Earth’s atmosphere, it compresses the air in front of it. When a gas is compressed it heats up, and the high speed—perhaps as high as 100 kilometers per second—of the meteoroid violently shocks the air in its path. The air is compressed so much that it gets really hot, hot enough to melt the meteoroid. The front side of the meteoroid— the side facing this blast of heated air—begins to melt. It releases different chemicals, and it’s been found that some of these emit very bright light when heated. The meteoroid glows as its surface melts, and we see it on the ground as a luminous object flashing across the sky. The meteoroid is now glowing as a meteor. Here I am guilty of a bit of bad astronomy myself. In the past, I’ve told people that friction with the air heats the meteoroid and,
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Bad Astronomy PPPPPPPPPPPPPPPPPPPPP
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Bad Astronomy PPPPPPPPPPPPPPPPPPPPP
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CONTENTS Introduction 1 PART I Bad
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CONTENTS vii Recommended Reading 25
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2 BAD ASTRONOMY luminous, against a
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4 BAD ASTRONOMY who fully well knew
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6 BAD ASTRONOMY But if they cannot
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PART I PPPPPP Bad Astronomy Begins
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1 PPPPPP The Yolk’s on You: Egg B
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THE YOLK’S ON YOU 13 and they mak
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THE YOLK’S ON YOU 15 ished announ
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THE YOLK’S ON YOU 17 Of course it
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THE YOLK’S ON YOU 19 with the wea
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2 PPPPPP Flushed with Embarrassment
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FLUSHED WITH EMBARRASSMENT 23 much
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FLUSHED WITH EMBARRASSMENT 25 Equat
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FLUSHED WITH EMBARRASSMENT 27 still
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IDIOM’S DELIGHT 29 press my heigh
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IDIOM’S DELIGHT 31 friend about w
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IDIOM’S DELIGHT 33 Incidentally,
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IDIOM’S DELIGHT 35 So you might c
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38 FROM THE EARTH TO THE MOON and t
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40 FROM THE EARTH TO THE MOON body
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42 FROM THE EARTH TO THE MOON red l
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44 FROM THE EARTH TO THE MOON top o
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46 FROM THE EARTH TO THE MOON photo
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5 PPPPPP A Dash of Seasons: Why Sum
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50 FROM THE EARTH TO THE MOON Clear
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52 FROM THE EARTH TO THE MOON Equat
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54 FROM THE EARTH TO THE MOON Howev
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56 FROM THE EARTH TO THE MOON the S
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58 FROM THE EARTH TO THE MOON These
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60 FROM THE EARTH TO THE MOON the d
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62 FROM THE EARTH TO THE MOON That
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7 PPPPPP The Gravity of the Situati
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66 FROM THE EARTH TO THE MOON is co
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68 FROM THE EARTH TO THE MOON a poi
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70 FROM THE EARTH TO THE MOON you
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72 FROM THE EARTH TO THE MOON Moon,
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74 FROM THE EARTH TO THE MOON that
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76 FROM THE EARTH TO THE MOON galax
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78 FROM THE EARTH TO THE MOON that
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80 FROM THE EARTH TO THE MOON exact
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82 FROM THE EARTH TO THE MOON The P
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Page 127 and 128: 13 PPPPPP Shadows in the Sky: Eclip
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Page 153 and 154: 16 PPPPPP When the Universe Throws
Page 164 and 165: PART IV PPPPPPP Artificial Intellig
Page 166 and 167: 17 PPPPPP Appalled at Apollo: Uncov
Page 168 and 169: APPALLED AT APOLLO 157 My question
Page 170 and 171: APPALLED AT APOLLO 159 Admittedly,
Page 172 and 173: APPALLED AT APOLLO 161 These belts
Page 174 and 175: APPALLED AT APOLLO 163 solid-state
Page 176 and 177: APPALLED AT APOLLO 165 However, you
Page 178 and 179: APPALLED AT APOLLO 167 flow well be
Page 180 and 181: APPALLED AT APOLLO 169 One of the m
Page 182 and 183: APPALLED AT APOLLO 171 The shadows
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Page 186 and 187: WORLDS IN DERISION 175 Many people
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Page 192 and 193: WORLDS IN DERISION 181 This premise
Page 194 and 195: WORLDS IN DERISION 183 Venus’ orb
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WORLDS IN DERISION 185 or mainstrea
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19 PPPPPP In the Beginning: Creatio
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IN THE BEGINNING 189 want to believ
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IN THE BEGINNING 191 squarely at th
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IN THE BEGINNING 193 tem started ou
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IN THE BEGINNING 195 it’s natural
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( a.) ( b.) ( c.) IN THE BEGINNING
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IN THE BEGINNING 199 their lives, e
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IN THE BEGINNING 201 ence isn’t l
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MISIDENTIFIED FLYING OBJECTS 203 la
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MISIDENTIFIED FLYING OBJECTS 205 In
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MISIDENTIFIED FLYING OBJECTS 207 an
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MISIDENTIFIED FLYING OBJECTS 209 Ne
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MISIDENTIFIED FLYING OBJECTS 211 ni
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MARS IS IN THE SEVENTH HOUSE 213 Th
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MARS IS IN THE SEVENTH HOUSE 215 as
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MARS IS IN THE SEVENTH HOUSE 217 Mi
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MARS IS IN THE SEVENTH HOUSE 219 of
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PART V PPPPPP Beam Me Up We’ve tr
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22 PPPPPP Hubble Trouble: Hubble Sp
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HUBBLE TROUBLE 225 The Hubble Space
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HUBBLE TROUBLE 227 A DROP IN THE BU
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HUBBLE TROUBLE 229 for space telesc
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HUBBLE TROUBLE 231 staking your sci
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HUBBLE TROUBLE 233 also used to say
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HUBBLE TROUBLE 235 can assure you t
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STAR HUSTLERS 237 That’s a tall o
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STAR HUSTLERS 239 the names aren’
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STAR HUSTLERS 241 I’ll note that
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STAR HUSTLERS 243 The star “Phili
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24 PPPPPP Bad Astronomy Goes Hollyw
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BAD ASTRONOMY GOES HOLLYWOOD 247 ar
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BAD ASTRONOMY GOES HOLLYWOOD 249 si
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BAD ASTRONOMY GOES HOLLYWOOD 251 it
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BAD ASTRONOMY GOES HOLLYWOOD 253 Tr
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BAD ASTRONOMY GOES HOLLYWOOD 255 In
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BAD ASTRONOMY GOES HOLLYWOOD 257 Si
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260 RECOMMENDED READING with the ma
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262 RECOMMENDED READING One of the
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264 ACKNOWLEDGMENTS Vergano, for gi
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266 INDEX “Astrology: Science or
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268 INDEX earthquakes, 130, 182 pla
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270 INDEX Islam, 58-59 “It’s Sp
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272 INDEX neutrons, 34 in stars, 98
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274 INDEX Sirius, 100, 107 size con
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276 INDEX triangles, 148 true scien
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