Astrotwins — Project Blastoff (5 page)

“Me,” said Mark.

“There's a surprise,” said Scott.

Mark ignored him. “Sir Isaac Newton was born in England in 1642 and died in England in 1727. One day, while he was still alive, an apple fell on his head, and—”

“The story of Newton and the apple is made up. It's a myth,” Howard interrupted.

Barry said, “Maybe not. And anyway, it's a good story.”

Mark gave Howard a dirty look. “Like I was saying, his bruised head made him think about why the apple fell, and all of a sudden he realized that large objects like the Earth pull other things to them, and that pull is caused by gravity.”

“Small objects have gravity, too,” Howard said. “But how much they have is proportional to their mass,
so massive objects like Earth have more.”

Mark frowned. He didn't like being corrected.

Meanwhile, Scott said, “I thought we were talking about three laws.”

“The first one is the law of inertia,” Mark said. “According to it, an object at rest will stay at rest until a force moves it.”

“That one made sense to me,” Scott said, “because I happen to know from personal observation that our dad lazing around on the sofa will stay lazing around on the sofa until a powerful force—like our mom—makes him get up.”

“There's another part of the first law too,” Mark said. “Once something's moving, it stays moving, unless a force slows it down.”

“Yeah, and that part
didn't
make sense to me,” said Scott, “because I also happen to know that if I throw a baseball and no one catches it, it doesn't fly forever. It would be cool if it did, though.”

“Actually, it would be kind of dangerous,” said Barry. “Everybody'd always be getting hit with escaped baseballs, footballs, Frisbees, old javelins from King Arthur's time . . .”

Egg and Howard started to explain at the same time why flying javelins aren't much of a threat, but Scott stopped them. “Slow down a sec, would you? I already feel stupid.”

“You're not stupid. It was a good question,” Egg said.

“Oh, come on,” said Mark. “He's at least a little bit stupid.”

“Scott doesn't seem that stupid to me,” said Howard.

“Thanks . . . I think,” Scott said. Then he looked at his brother. “If you know so much, you explain it.”

“Uhhh . . . ,” said Mark.

“Thought so,” said Scott.

Egg tried again. “There are two forces that stop the baseball, but they're both so familiar that they're easy to forget—gravity and friction.”

“Okay, I get gravity,” said Scott. “We already covered it, plus it's the reason a high fly ball doesn't go to Jupiter. But friction means rubbing against something. What's the baseball rubbing against?”

“The air,” Egg explained. “Think of air like water, because in a lot of ways it is. If you threw a baseball in water, the water would resist, and the baseball wouldn't get far. Air is the same thing only not as dense, so it doesn't slow things down as much.”

Scott nodded. “Okay. I think I am now officially ready for the second law.”

Mark opened his mouth, but Howard was faster. “Force equals mass times acceleration, which can also be expressed as the equation
F
=
ma
.”

Barry nodded.

Everybody else just looked at Howard, who finally shrugged. “There's nothing else to explain. That's it.”

“Maybe for
you
,” Mark said. Then he looked at Barry. “You want to try that in regular human-speak?”

Barry said, “Going back to throwing a baseball, the force is how hard your arm pushes it, the mass is the ball, and the acceleration is, well . . . acceleration.”

“The rate at which the ball's speed speeds up,” Egg said.

Howard added, “Another way to say that is, the rate of change of its momentum.”

Mark had had just about enough of Howard showing off how smart he was. The kid was weird. Why didn't he ever smile? How come Egg had even brought him?

Scott closed his eyes and tugged his short hair. “You're all giving me a headache. But I think it makes sense. How hard you throw the baseball, and the mass of the baseball, determines how fast the baseball accelerates.”

“Mass is the same as size, right?” Mark said.

“Sort of,” Barry said. “Mostly when we say size, we think of volume. So the volume of a beach ball is bigger than the volume of a baseball, but a baseball is more massive—”

“—because it's heavier,” said Mark. “I get it.”

Egg shook her head. “Not exactly. Mass is more like
the amount of stuff in stuff. Remember that the idea of ‘heavy' relates to gravity, and in space gravity's force is less than on Earth. So the weight of something changes when it's in space, or on the Moon, or on Earth, but its mass is always the same.”

“There's an equation that describes mass,” said Barry.

“I was afraid of that,” said Scott.

“Mass equals density times volume—
M
=
D
·
V
,” Barry said.

“What Scott said about common sense is right,” Egg said. “But you have to remember there are other influences on acceleration besides force and mass. There are also friction and gravity.”

“Friction and gravity
again
?” said Mark.

“And because the second law is an equation, you can work it backward and sideways,” said Barry.

“Try that one again,” said Scott.

“If you know the mass of something and how fast it's accelerating, you can figure out how much force it took to move it. And if you know its acceleration and the amount of force that moved it, you can figure out its mass.”

Scott nodded. “That's cool.”

Barry said, “That's algebra.”

“Really?” Scott said. “So now I know algebra?”

“Algebra just means using variables—like
letters—to solve problems. So if I say two
x
equals six, solve for
x
, then I've expressed an arithmetic problem as algebra,” Barry said.

“
X
equals three,” Mark said.

“My brother, the genius,” Scott said.

Mark waved and bowed to an imaginary crowd of fans—“Thank you, thank you very much”—until Howard interrupted by saying, “I don't think Mark is a genius.”

Mark was more surprised than insulted, but Scott and Barry both sat up, ready to pound the kid.

“Howard!” Egg said. “That was a joke!”

Howard looked from Scott to Barry, alarmed by their reaction. “It was?”

“Sometimes Howard doesn't get jokes,” Egg explained.

“He got the one about Fig Newton,” Mark said.

Keeping his eyes on Scott and Barry, Howard shook his head. “No, I didn't. I just laughed because everyone else did. A Fig Newton is a cookie, right? What does a cookie have to do with Sir Isaac Newton?”

“They have the same name,” Barry said.

Howard nodded solemnly. “Yes.”

Mark saw that the kid was genuinely confused. He's weird, all right, Mark thought. And kind of obnoxious, but maybe not on purpose. Then Mark thought of somebody on a TV show his parents used to watch,
Star Trek
. The character's name was Mr. Spock, and he never smiled. Howard reminded Mark of Mr. Spock.

Thinking of that, Mark felt less angry. “What's really insulting,” he said, “is how you guys think the perfectly reasonable idea that I'm a genius is only a joke.”

That made everybody laugh—Howard too. But Howard's laughter seemed nervous.

“Remember how my butt was starting to hurt?” Barry said. “Well, it's happening again, not to mention I'm getting sweaty.”

“Luckily, there's only one more law,” said Egg. “For every action, there is an equal and opposite reaction.”

Mark nodded. “So if I bounce a basketball on the ground, it bounces back up. I get it. Are we done?”

Egg frowned. “A basketball isn't a good example. There's gravity, friction, the effect of the compression of the air inside, the rubberized material . . .”

“Yeah,” Scott said, “because in my personal experience, if you try to bounce a rock off the ground, it won't work. I think maybe Newton got the third law wrong.” He shrugged. “But hey, he made a good effort. And two out of three isn't bad.”

“It's not good enough to qualify you as a genius, though,” Mark said, “and genius is something I happen to know about.”

Howard pointed at Mark. “That was a joke. Wasn't it?”

Mark said, “There's hope for you yet, but can I ask a question? What are you doing here, anyway?”

Scott and Barry fidgeted.

Egg frowned angrily. “He's here because I invited him!”

“I know that,” Mark said, “and I also know you invited him for a reason, so what was the reason?”

Howard did not seem bothered by the question. “My Altair 8800,” he said. “Also, I know BASIC.”

Scott looked at everybody else. “Translation?”

Egg explained. “An Altair 8800 is a computer that's small enough so you can have one at your house—and Howard does. BASIC is the name of a language for telling the computer what to do.”

“Whoa,”
said Barry. “That is so cool. Did you put the 8800 together yourself or buy it preassembled?”

“I put it together,” Howard said. “It wasn't hard.”

Now Scott and Mark were paying attention. This Howard kid had assembled a real computer himself! That was way better than taking apart a calculator. They had a thousand questions, but before they could ask even one, Egg looked up and waved.

“My mom's here,” she said. “We gotta go.”

Howard lived west of town, so Mrs. O'Malley gave him a ride to his dad's work, which was nearby on the highway at an auto repair place called Nando's.

“See you tomorrow at two?” Howard said to Egg when he opened the car door.

“Sounds good,” said Egg. At the same time, a girl came out of Nando's office door and smiled and waved.

“Hang on a sec, Mom, could you?” Egg jumped out behind Howard and jogged over to talk to the girl.

“That's Lisa Perez,” Mrs. O'Malley told Mark, Scott, and Barry. “She's in Howard's class at school, and it's her dad's shop.”

Egg came back a few seconds later and climbed in. Howard turned to wave, but didn't smile.

“He doesn't like us,” Scott said as they drove off
toward Grandpa Kelly's house. “And now we'll never get to fool around with his computer.”

“I don't think it's that,” Egg said. “He's just not a smiler.”

“So, Egg, what is it you and your good friend Howard are doing tomorrow at two o'clock?” Mark asked.

“Library,” Egg said, “just like you.”

“Hey—wait a second,” Mark said.

“You've got to be kidding!” Scott said. “Today was enough library to last me through summer, and possibly high school.”

“Seriously?” said Egg. “You thought that was all the research we needed to do to build a—”

“Egg!”
Mark waved to keep her from giving away the secret.

“—a science fair project,” Egg concluded.

“You guys have to admit there's a lot we don't know yet,” Barry said.

“Yeah,” said Egg. “Like we should research the history of the space—”

“Egg!”
Mark interrupted again.

Mrs. O'Malley laughed. “What if I just promise not to listen?”

Egg said, “Or what if everybody just agrees we'll go to the library again tomorrow? We can talk then.”

Barry was in favor. Scott and Mark grumbled, but in
the end said okay.

When Mrs. O'Malley pulled into Grandpa's driveway, she said, “I trust you kids, so I'm glad to support the project you're working on. It's even okay—for now—if you don't want to give away secrets. However, I'd appreciate it if you promised me one thing.”

“What's that, Mom?” Egg asked.

“Just please don't blow anything up.”

*  *  *

“I wonder why everybody's so worried we'll blow something up,” Mark said later. The three boys were clearing dinner dishes. Grandpa had grilled hot dogs, and they had eaten outside at a table on the flat patch of dirt that was supposed to become a patio one day. Now the boys were cleaning, and Grandpa was talking to someone—they didn't know who—on the telephone extension in his bedroom.

“I guess we just look dangerous,” said Scott.

“Or”—Barry stuck out his tongue, rolled back his eyes, and waggled his fingers—
“crrrrr-azy!”

In the kitchen, Scott turned on the water to start washing dishes. “Maybe they've figured out what the project is. It's kind of like blowing something up. There will be flammable fuel, and we'll ignite it to send the rocket into space.”

“That's what Newton's Third Law is about, isn't it?” Mark asked.

Scott turned off the water; then both twins looked at Barry.

“Oh, I get it,” Barry said. “With Egg and Howard gone, now I'm the resident brain.”

Mark was quick to reassure him. “We think you're brainy even when Egg and Howard are around.”

“Just not that brainy,” said Scott.

“On the other hand,” said Mark, “you do have two good qualities. First, you get jokes, and second, you're not a girl.”

“Another thing I get is Newton's Third Law,” said Barry, “which is key to understanding how rockets work.”

Mark tossed him a dish towel. “You can explain while you dry the dishes.”

“More chores.” Barry sighed. “Hasn't your grandfather ever heard of this radical new invention, the dishwasher?”

“He says he doesn't need one for just one person, and if it's more than one person, it's us, and we're the dishwashers.” Mark handed Barry a plate dripping with water.