I say, “But what about you? Do you, as do I, play the piano?"
"Oh, no. Not at all. I've strummed a guitar a bit a long time ago. Most people have."
He hunches over his tea as if he's a too tall man trying to look smaller though he's hardly taller than I am.
"Are you a poet? You look like a poet."
"I used to ... now and then, but not much anymore."
I feel a sudden yearning. For what? Nostalgia for my unknown past? For my past that was in the future? I yearn to tell him, “I'm from the future. Or maybe from the past,” but I know better than to say any such thing. Tears come to my eyes. I wish I was back where I belong wherever or whenever that is. I take a big drink of tea. I wipe my eyes while pretending to wipe my mouth.
He's saying, “...so that's all about me. Not much."
"Oh that's very interesting."
"Here's the scar,” he says, and pulls up his pants leg.
"Oh, my."
But he has to get back to the bookstore. He tells me if I want a quiet place to write I can come with him and sit in the back room.
* * * *
I sit in the little cluttered room and try to forget about money and where I might have to sleep tonight. I write Geraldine on the front of my notebook so I can check on it if I forget what I told him. I'm sure he told me his name but I don't remember.
On the first page I write: What DO I know about my skills? I sit still and think. What do I know about the future? Are there any tests for finding out when one comes from? I think as hard as I can but I don't come up with any answers. I've hardly made a single note.
When I hear customers in the front part of the store, I snoop around. I find several coins in a drawer. I find half a peanut brittle bar. I take them.
Did I used to steal things? Maybe this is my usual way. I hope it isn't. No wonder I decided to start over.
I simply will not ask for any more help from this man. He's just too nice.
I gather up my things—into a plastic bag with the name of the bookstore on it—and walk to the front. I guess I look like I'm leaving because he stops me.
"It's cooling off. Don't you have a sweater?"
I don't know what to answer.
"You don't, do you?"
"I'll be all right."
"It looks like rain, too. I can't invite you home with me. My place is too small, but if you want, you can stay here. It won't be very comfortable but there's a cot in the store room. I hate to see anybody homeless."
Of course anybody from the future has got to be homeless. Did he guess where I'm from?
"What can I do for you? Any knowledge? Any skills I may have that might be useful?"
"One of these days you can play the piano for me."
"I'll do that. I promise."
* * * *
He locks me in ... so to speak. I can get out if I need to but I can't lock up after myself if I leave so I shouldn't.
I sit down again with my notebook and think about the future. I can't tell if I really am from there or not. Maybe I could if I could see the new buildings of this time to see just how new they are, but this is an old part of town. There always are old parts that are just the same as hundreds of years ago. They do still have cars. Though in this neighborhood they seem rather grungy. I can think of a car that's shaped like a bubble. I can think of walkways over roads so nobody ever has to cross the street. (But are we still walking across streets in the future?)
I appeared without a newspaper with a date, though why would we still have newspapers in the future? I seem to remember they were dying. I suppose bookstores are, too. (That's why this funny little dusty one.) I arrived with nothing except my clothes. It's a wonder I didn't come through naked. And of course I would be homeless. Anybody coming from the future would be. I need to accept help. I shouldn't feel so bad about having to accept kindness from this man. Without people like him none of us time travelers would be able to get along at all.
Do we still have pianos in the future?
Oh my God, do I need to remember that dirty doorway where I first arrived in order to get back to my real present time? Is that what they call the portal? I don't think I can find it.
I lie down but I can't sleep. I'm thinking how, even if I really am from the future, there's nothing I can teach anybody. I don't even know how to make old things. I couldn't make a printing press, or especially not a flute what with all those valves. I couldn't even hang a door, frame a window.... Light bulbs! Actually I don't even know how to make a candle.
I'm having a terrible night. But I'm going to leave before he comes back. He said he'd be here at 8:30 but I'll be gone. He's done enough. Other people should help the woman from the future.
(Before I try to get back to the portal, should I try to find a piano? Middle C. Why do I know that?)
* * * *
Except I'm not gone. I finally fall asleep and don't wake up until after eleven. He's brought me coffee and a muffin and opened the shop long ago. The coffee's cold, but still good.
I wish I could remember his name. It must be in here somewhere. While he's busy I snoop around again.
Then I hear the front door slam ... hard. I go out and see a man come in who looks like he doesn't belong here. The bookstore man and I both know it. We look at each other. The man is burly and frowning. He's like those men I tried to avoid yesterday. He wanders around, pretending to look at titles. Is he going to buy something or just walk around? Or is this a stickup? If I'm really from the future I ought to be able to do something these people wouldn't think of. Or maybe he came for me. Maybe he's one of those men I was trying to avoid all day yesterday.
But I shouldn't jump to conclusions. That would be just like my old impetuous self.
He comes close to me and whispers, “What in the world are you thinking?"
I have no idea what he means.
I tell him this must be a case of mistaken identity.
He grabs my arm. So hard it hurts. “Come on,” he says.
Does he want to take me back to my present? I mean back to my present in the future.
"Do I mean something to you?"
"I'd never have thought to see you in a bookstore."
"Don't we have books where we come from?"
The odd thing is, the bookstore man is bald and ugly and this man is handsome, even to a full head of curly black hair, but I don't like his looks at all.
The bookstore man says, “Can I help you?” Politely, as if the man might want to buy a book. But the man doesn't let go of me and doesn't stop trying to pull me out the door.
Do people from the future know how to fight? Do I? I wonder if I ever knew karate or any such thing. For all I know about myself, I could be an expert.
On the other hand, maybe this handsome revolting man can help me get back to the future. I don't know which side I ought to be on. Of course here I don't have a place to be or a life at all, though I do have a start.
But I wouldn't want anything to happen to the bookstore man.
The bookstore man tries to help me pull away, but the big man swings me around as if I was a weapon and knocks the bookstore man down. A lot of books go down, too—a whole shelf full, and I'm down, but I'm free. The floor is slippery with books. The bookstore man gets up and tries to punch the big man.
I'm thinking: Stop wondering if you know karate. Respond automatically just as if you did.
I wait for my chance and then give a good kick right where it hurts the most and when the big man is dealing with that, I push him over backward.
I'm thinking: Any minute he's going to disappear into the future but he doesn't. He staggers up and looks at me, surprised. As he leaves he says, “Well, stay here, then."
* * * *
After our adventure the bookstore man and I hug and the bookstore man gives me a very nice little peck on the cheek. Then we prop up the bookcase and put the books back.
To celebrate we go out to a piano bar. It's early. Hardly anybody is the
re. Now's my chance. I mean I was pretty good at karate or whatever that was. I tell myself to do just as I did when I kicked and pushed the big man. I didn't think at all and everything came out just right.
I sit down at the piano. There's Chopin. There's Bach. There's Mozart. Do I know them or are they just names I've heard before? I put my hands on the keys. I spread my fingers. There's my middle C right in front.
[Back to Table of Contents]
Department: Science: Rocks In Space by Paul Doherty & Pat Murphy
On November 20, 2007, Andrea Boattini of the University of Arizona's Catalina Sky Survey spotted an extremely faint object moving across the stars. The story of that object—an Apollo asteroid named 2007WD5—had the makings of a science fiction thriller. Unfortunately for fans of conventional thriller structure (a form marked by mounting tension), most of the story was over by the time Boattini discovered WD5.
Every four years this asteroid—a rock measuring about fifty meters in diameter—drops in from the asteroid belt to cross the Earth's orbit. On November 1, 2007, WD5 had zipped by the Earth at a distance of 7.5 million kilometers, just thirty times farther away than the Moon—a near miss by astronomical standards.
In any thriller worth its salt, one hair's-breadth escape is quickly followed by another. Shortly after Boattini spotted WD5, astronomers at NASA's Near Earth Object program realized that this asteroid was going to pass very close to Mars on its return to the asteroid belt. In fact, there was a chance that the asteroid might collide with the planet—exciting news for anyone interested in cratering and planetary impacts. If WD5 hit Mars, scientists estimated it would make a crater about a kilometer in diameter and 200 meters deep. High-resolution orbiting cameras circling Mars were poised to provide a ringside seat to the aftermath of the impact.
When news of the possible impact went out, the Exploratorium in San Francisco sprang into action, preparing to create a webcast of the impact if it happened. Alas (for the Exploratorium, astronomers, and disaster enthusiasts everywhere), the asteroid passed close to—but missed colliding with—Mars on January 30, 2008. WD5 passed so close to Mars that the asteroid's orbit was disturbed by the gravitational interaction. Astronomers have lost track of WD5 for now, but they expect that it will return in four years.
But we're not willing to wait four years to share all the research Paul did about what happens when an asteroid bashes into a planet. Scientists and science fiction writers are both in the business of asking “What would happen if...?” In this case, we'll take a look at what would have happened if WD5 had struck the Earth or Mars.
Belly Flops and
Asteroid Impacts
If you've read Robert Heinlein's The Moon is a Harsh Mistress, you already know that an asteroid hitting the Earth will mess things up in the immediate vicinity of the impact. In that novel, moon colonists use a catapult to “throw rocks"—really big rocks—at the Earth.
But if you're like us, you're curious about exactly how destructive that impact will be. We can help you there. The level of destruction depends on three factors: what makes up the asteroid, how big it is, and how fast it's traveling.
Natural objects that are likely to strike a planet come in three major flavors: ice, iron, and stone. Each type of object behaves differently on hitting the planet's atmosphere, if it has one. We'll start close to home and consider what happens to an object entering Earth's atmosphere.
To appreciate what happens when an object hits the atmosphere, remember the last time you did a belly flop. If you fell flat into the water from the edge of the pool, the water welcomed you with a soft gentle splash. If, however, the flop was the result of a bad dive from a platform that's ten meters (thirty feet) above the water, you probably remember the pain to this day. (Paul certainly does!)
At slow impact speeds, it takes small forces to accelerate the water out of your way. At higher speeds, it takes extremely high forces. Diving from the higher platform, you hit the water a lot faster. Your body exerts a lot of force on the water. Newton's third law (For every action, there is an equal and opposite reaction) dictates that when your body slaps the water, the water also slaps your body—a nasty example of physics in action.
Remember the pain of your last belly flop as you consider a space object striking the Earth's atmosphere. That object is experiencing a similar situation. The molecules in the air have no warning. Suddenly—"Wham!"—they are hit by the object! In keeping with Newton's third law, the air molecules hit back, exerting large forces on the object. One of those forces, the friction of the object passing through the atmosphere, heats the object's surface to incandescent temperatures—so hot that the object emits light. That bright light is what we see from Earth as a falling star or meteor.
The forces on the object may also break it apart or rip off pieces as it travels. (Search YouTube for “meteor” to see some exciting footage of incandescent meteors breaking apart and shedding bits as they travel.)
Let's get back to the three flavors of objects that might collide with Earth. Most icy bodies disintegrate in the atmosphere. They fall apart and melt long before they reach the Earth's surface.
Iron meteorites, on the other hand, are strong enough to hold together in large pieces despite the forces and the heat. Pieces of iron meteorites strike the Earth regularly. In fact, if you have access to the output of the downspout of a building, you can collect iron meteorite particles. Get a magnet (a refrigerator magnet will do fine) and paint it white. Place the magnet where water from the downspout will pour across it.
After a rainstorm, check the magnet for small black specks. Many of those specks are tiny iron meteorite particles that fell onto your roof and paused there until the rain flushed them onto your magnetic trap.
But don't let those cute little meteorites lull you into feeling all warm and cuddly about rocks that fall from the sky. Meteor Crater in Arizona was made by an iron meteorite about fifty meters in diameter—approximately the size of WD5. (Be happy that one didn't land on your roof!)
As a rule of thumb, an object impacting Earth will make a crater that's about twenty times the diameter of the impacting object. Meteor Crater follows this rule, measuring about 800 meters in diameter. (For a more precise estimate of the size of a crater produced by a meteorite impact, the Lunar and Planetary Laboratory has a website that allow you to calculate the size of the crater made by an object of a specific diameter and speed. See www.lpl.arizona.edu/tekton/crater.html.)
The third flavor—the rocky asteroid—is stronger than ice but weaker than iron. Like icy bodies, most rocky asteroids don't ever reach the ground. The forces resulting from impact with the atmosphere are large enough to break the rock into pieces. Each new piece is then exposed to collisions with more air, which breaks it up. This continues in a cascade so that the rocky object is pulverized high in the atmosphere.
How can we say this with such confidence? Well, we have a pretty good idea of what happens when a rocky asteroid of that size hits the Earth, since it happened near Tunguska, Siberia back in 1908. We'll get back to that in a minute.
How Fast? How Big?
As we said before, an asteroid hitting the Earth will create a mess in the spot it hits. One way to measure the expected destruction is to estimate the energy of the object as it strikes the atmosphere and the surface of the Earth. To do that, you need to know the object's mass and speed. When an asteroid is in motion, its kinetic energy is proportional to the mass of the asteroid times its speed squared.
There are two parts to the velocity of an object that will hit the Earth: the velocity it gains by falling into Earth's gravity well (about eleven kilometers per second or seven miles per second) and its orbital velocity around the sun relative to the Earth. Suppose an object has the same orbit as the Earth and is orbiting at about the same speed as the Earth (about thirty kilometers per second or twenty miles per second). If it's traveling in the same direction as Earth, it could slowly overtake the Earth, in which case it will drop in from nearly
rest and have the lowest possible speed of impact—about eleven kilometers per second.
At the other extreme, an asteroid might have the same orbit as Earth, traveling in the opposite direction. The speed that an orbiting object travels depends on the mass of the body it's orbiting (in this case, the sun) and the radius of its orbit (about 150,000,000 kilometers). So the asteroid that's in Earth orbit will be traveling at thirty kilometers per second, the same speed as the Earth. That asteroid could collide with Earth head-on, in which case it will start falling into the Earth with a velocity of sixty kilometers per second.
But an asteroid does not have to be in the same orbit as the Earth. It could drop in from the outer solar system, as WD5 did. Such an asteroid can be moving faster than an asteroid in Earth orbit—racing along at more than forty kilometers per second. If a such a rock hits the Earth head on, its forty plus kilometers per second velocity will add to the Earth's thirty kilometers per second orbital velocity producing the fastest speeds we see for meteors: seventy kilometers per second. Such an object enters the atmosphere at over Mach 200, more than 200 times the speed of sound.
Compared to the speed of these falling rocks, the speed of sound in air is positively glacial. Sound pokes along at a mere 350 meters per second or just 0.35 kilometers per second (700 miles per hour depending on altitude). The speeds at which objects hit the Earth range from 30 to over 200 times the speed of sound.
Combine these tremendous speeds with a substantial mass and you've got a lot of destructive potential. WD5 massed about a billion kilograms and would have hit the Earth at about twenty kilometers per second or 50,000 miles per hour. (Just for reference, that's fifty times the speed of sound or mach 50.) Calculate the kinetic energy of WD5, and you'll get many megatons—the energy of a large hydrogen bomb!
Ground Zero—Siberia
That brings us to Tunguska, a region of Siberia known mainly for peat bogs and pine forests. According to eyewitness accounts in 1908, a bright, flaming object came down from the sky at an angle, followed by a giant bright blast. The heat wave and wind blast flattened huts and trees for 800 square miles. Forty miles from the impact site, windows shattered, ceilings collapsed, and people and livestock went flying. Hundreds of miles away, the Earth shook and people heard the “thunderclaps” of the impact.
FSF, October-November 2008 Page 20
