by Nate Ball
An angry soldier’s face appeared in the dark at the top of the ladder, just feet away. “Don’t move!” he shouted, pointing at me. “You are under arrest!”
“Seriously?” I squeaked. The door on the Dingle closed again with a little snick noise.
“There’s a kid in his underwear up here!” the soldier hollered back down the ladder. “The beast has him!”
The soldier sprung from the ladder and landed on his big black boots in front of me. He got into a fighting position, like he was ready to do battle.
“Take it easy, sir,” I quivered. “I give up!” I raised my hands in surrender.
“Go, Amp, go!” I commanded with my mind. “Now’s your chance!”
“Hold on,” Amp said inside my head.
“Hold on to what?” I said aloud.
The soldier looked at me. “Hold on to what?” he asked. “What does that—”
Just then the Dingle shot up with a whoosh and punched me in the gut.
Acting on reflexes alone, my arms wrapped around the spaceship like I had just caught a forty-mile-an-hour football pass.
Then I was flying, spinning like a human helicopter over the roof.
The soldier was chasing us, his hands outstretched at me.
My boxers flapped in the wind.
“Boy, you’re heavy!” Amp said in my head.
“Stop! That’s a direct order! You get back here!” the soldier yelled.
The soldier ran out of roof and stopped at the edge, his arms flailing as he worked to keep his balance.
Now I was high in the air again for the second time that night. The camp below me had exploded with activity. Soldiers, men in suits, people in lab coats, and others I couldn’t make out spilled from the building and searched the dark sky for us.
I didn’t think flying could be any more uncomfortable than hanging on to a stick at the end of string, but this topped it.
I was practically naked, spinning like a top, and wobbling back and forth over a floating ball that rose and dove through the air.
“Problems with the stabilizers,” Amp growled in my head.
“Olivia and her grandpa!” I said as best I could with my brain. “They’re on the road. Outside the main gate. Three hundred yards or so.”
“Got it,” Amp replied sharply, sounding more like himself. “Just hold on.”
“I assume going back for my clothes is out of the question?” I said jokingly.
“Yes, much too risky,” Amp replied. “Especially since it seems the invasion has begun.”
And as we rose into the air, thousands of Erdian spaceships descended all around us.
My life was not dull.
But there was still much left to be done.
I’d managed to save Amp. Now I had to save Earth.
Try It Yourself: Hover-Ship
When Zack and Olivia sneak back into Zack’s room to rescue the Dingle, they discover a shocking surprise: Amp’s ship is hovering in midair, all by itself! How on Earth would such a thing be possible? Even though we’ve dreamed of hovering cars and flying skateboards for ages, you sadly still don’t see any real-life versions around town.
But it turns out that even though you can’t ride a hover-bike to school (yet), there are real-life ways to make objects hover in midair in just the same way the Dingle can—using science!
Invisible Forces
Imagine holding a toy airplane in your hand and zooming it around the house. Though it’s not flying by itself, the airplane is still positioned in midair. It’s just that your hand is holding it there. You already know why you have to hold it there with your hand: you have to counter the force of gravity on the airplane. If you let go, the airplane will drop to the ground—pulled downward by gravity.
What about a paper airplane? You can make it fly through the air by itself with a throw. Why doesn’t it fall right to the ground without you holding it up? In this case, your hand isn’t countering the force of gravity—the air in the house is. Even though you can’t see it, the air is doing just the same job your hand was. It’s applying an upward force to the airplane that’s equal to the force of gravity pulling down.
For anything to hover above the ground—anything at all—an invisible game of tug-of-war is being played. Something is exerting a force on the hovering object that’s exactly the same strength as the force of gravity pulling it down.
Thing Type of Force that Fights Gravity
Airplane Air pressure difference across wings
Helicopter or drone (like a quadcopter) Acceleration force from pushing air downward
Maglev bullet train Electromagnetic force
Hot-air balloon Buoyancy in air
Hair standing up on end from static electricity Electrostatic repulsion
“Magic Wand” toy Electrostatic repulsion
Amp’s ship, the Dingle Electromagnetic force
Most of the hovering and flying forces listed are impractical for indoor use. Airplanes have to fly super-fast, helicopters and drones have to spin their blades at high speed, hot-air balloons are huge, and electrostatic forces are not very strong.
To get something smaller to hover in a more practical way, we might choose to look to another force to counter the downward force of gravity. Electromagnetic forces are a great option because they’re pretty easy to create or find and control. And as you might remember from Alien in My Pocket: The Science UnFair, Amp brought special alien technology to Earth that can control Earth’s magnetic field, which makes it possible to exert huge forces on any objects that can also interact with magnetic fields. This is how the Dingle can float in midair without propellers: it bends the Earth’s magnetic field around to exert forces on itself which counter gravity’s downward pull.
Building Your Own
Magnetic Hovering Ship
Even though we don’t have the technology to just bend the Earth’s magnetic fields around at will, we do have the ability to manipulate magnetic fields in other ways. You may have already built your own electromagnet with instructions in the back of Alien in My Pocket: The Science UnFair.
In this experiment, we will use permanent magnetic fields to make objects hover in midair almost like the Dingle does.
With the help of an adult, gather these materials:
Materials for the dock:
• A small block of wood, like a 1x4, that’s about 6 inches long, for the base
• Another small piece of wood for the top, about 5 inches long, and a bit more narrow than the 1x4 base
• A dowel rod ½ inch in diameter, about 7 inches long
• A threaded hook, like you might hang a picture with
• Two strong cylindrical magnets—one should be solid and about ½ inch in diameter (like D88-N52 from K&J Magnetics—www.kjmagnetics.com) and the other should have a hole in it (like R828 from K&J Magnetics)
• About a foot of string, in a size that fits through the second magnet’s hole
• Wood glue
Materials for the ship:
• Paper—ideally nice and thick, like construction paper
• Colored pencils or pens for decorating
• Scotch tape
Tools:
• A drill
• A drill bit the same diameter as the dowel rod and the magnet without the hole (½ inch)
• A drill bit slightly smaller than the threads on the threaded hook
• Scissors
• Safety glasses
• Measuring tape
Step 1: Drill all the holes
1. Safety first: Put on your safety glasses
2. Use the ½-inch drill bit to drill a hole about ¾ inch away from one end of both the base and the top beam
3. Use the ½-inch drill bit to drill a hole about 4 ¼ inches away from the same end of top beam
4. Use the tiny drill bit to drill a hole in the base about 4 ¼ inches away from the same end of the base
Step 2: Install the top magnet
Add a s
mall amount of glue to the ½-inch hole in the top beam. Press the solid cylinder magnet into the hole. You might use the base block of wood to push against the magnet so you can apply more force. Push it all the way in as shown below.
Step 3: Install the hook
Screw the hook into the small hole in the base. Be careful not to overtighten it!
Step 4: Join the top beam to the base using the dowel rod
Put a small dab of glue in the ½-inch diameter holes in both the base and the top beam. Install the dowel rod into the top beam, giving it a twist as you push it in. Then install the bottom of the dowel (with top beam attached) into the base with a twist as you push it in. Twist the top beam so it’s parallel to the base.
Step 5: Wait a while for the glue to dry
This is the hardest part! It usually will take a few hours at least. If your dowel rod had a really tight fit, you might not need to wait as long to proceed.
Step 6: Tie the second magnet to the string
Put the second magnet (the one with the hole in it) up near the first magnet, which is sitting in the top beam. Check which end of the second magnet wants to grab the top magnet. That’s the top side. Push an end of the string through the hole in the magnet from the bottom to the top and tie a big knot in the top end so it can’t pull through. If you can’t tie a big enough knot, pull the string all the way back around and tie it back to itself so the magnet is stuck on a loop of string and can’t come off.
Step 7: Attach the magnet’s string to the structure
Allow the magnet tied with the string to grab the magnet glued to the top beam, so the string is hanging down. Wrap the string around the hook, and then tie it to the dowel rod. Try using a clove hitch—it’s the best way to tie a rope or string to something solid and round. Add some tape to help hold the string in place on the dowel.
Step 8: Make it hover
Wrap the string many times around the hook until the bottom magnet can’t touch the top magnet anymore. Now bring the magnet back up to the top near the stationary magnet—can it stay up all by itself? If so, great! It’s hovering!
If the magnet can’t stay up all by itself, unwind a couple of wraps of string.
Step 9: Getting it dialed
To make the science sculpture look as cool as possible, it’s fun to have as much space as you can between the top magnet and the bottom magnet. Once the magnet underneath is hovering in the air, held in place by the string, shorten the string by adding one wrap at a time to the hook. With each wrap, the gap between the magnets grows. Try to adjust it so the magnet is barely held in place. Voilà! A magnet, hovering in space! You may notice that the farther away from the top beam your magnet hovers, the more slowly it moves, and the more it appears to be floating all by itself in space.
Step 10: Add the ship!
Now that you’ve got a magnet that can hover, it’s time to put a spaceship on it. Do your best to copy the pattern for Amp’s ship, the Dingle, onto your own piece of construction paper. Color it in if you want. Then cut it out, fold the tabs in, bend the paper at the dotted lines, and create the shape of Amp’s tiny spacecraft. There should be a hole in the bottom big enough to pass the magnet through. Flip the whole structure upside down so the magnet is hanging downward with gravity—then drop the magnet through the hole in the ship, carefully hold it in place, and turn the whole assembly back upright. Look, it’s the Dingle hovering in midair, ready to go rescue Amp!
Experiment Time
The magnets you’re using to make the tiny paper model of the Dingle are called “permanent magnets”—that means the magnetic field they create can’t be turned off. It’s always on, and its strength will stay about the same all the time.
You surely know by holding magnets in your hand that the closer they are together, the harder they want to pull themselves to touch. But what’s the relationship between the distance and the strength of the pull?
A Little Distance Makes a Big Difference
1. With your magnet and ship hovering in the air, give a very controlled, gentle tug on the string until the magnet falls away from the top. Rate the amount of force on a scale of 1–10, where 1 is a tiny amount of force and 10 is a lot. Write it down on a table like the one on the next page:
Number of Wraps Undone Amount of Force
(your rating on a scale of 1–10)
0
1
2
. . .
Magnets touching
2. Undo a second wrap, reset the magnet, and give another controlled tug. Rate it on the same scale, and record your rating across from the corresponding “number of wraps undone” number. Keep going until the magnets are touching.
3. Extra Credit: Make a graph! Graphs are really useful tools that help us visualize data like the data points you took in your table. For each number of wraps undone (these are the values on the X axis), record the “amount of force” rating you wrote down (along the Y axis).
4. Extra Credit: With your graph all done, it’s time to interpret the data to figure out what it means! Start making observations. When the magnets were far apart, how big of a change in force happened by just removing one wrap? Was it a big or a small change? And how does it compare to the change in force when the magnets are almost touching? What do you think it means about how magnets work? It’s all about questions now—what questions do you have about the experiment? How might you go about answering them?
5. Extra Credit: Taking it further: think about how strong these magnets are and the intensity of the fields that give them that strength. It might be enough to levitate a paper ship, which is totally cool. But how strong of a magnetic field would it take to make a football-size ship hover above the Earth with a tiny alien and a fourth-grader hanging from it? Especially really high off the ground? That’s a strong magnetic force! We’re going to need a lot more magnets. . . .
BACK AD
AN EXCEPT FROM ALIEN IN MY POCKET #8: SPACE INVADERS
Read a sneak peek of book eight of the Alien in My Pocket series:
The Mess I Made
It’s hard to be a kid these days.
Think about it.
You’ve got chores, tons of homework, and little brothers. Moms and dads are always bossing you around and saying they know best. Coaches make sour faces every time you take batting practice. And teachers think learning is the most exciting thing ever invented.
It can all be a bit much for a fourth grader to handle without going nuts.
Now add to all that the responsibility of ensuring the survival of the human race, and you get a glimpse into my life.
I’ve pretty much gone nutty.
And it’s easy to pinpoint exactly when it all went wrong: the day Amp arrived.
Amp is the avocado-size alien who burst into my life when he flew through my window screen. His football-size spaceship dented my bedroom wall and crash-landed on my bed.
Connecting the dots from that first, shocking night to the possible end of mankind wasn’t easy to do. But that didn’t mean it was any less true. Because that moment so many months ago really had led directly to this night. Earth—and the billions of people living on it—was in serious crisis, even if they didn’t know it yet.
Which was, more or less, what I was thinking about as I flew through the cool night in my underwear. I was clinging to Amp’s spaceship for dear life as an army of soldiers chased me from below and an alien force poised to invade Earth floated above me in the starry sky.
As I said, it was an odd time for a kid whose biggest accomplishment previously had been making the travel baseball team as a catcher with a pretty decent throw to second base and a so-so batting average.
Despite all that, the world was counting on me.
Now if I could only find some pants.
Face-Plant
Amp landed near Olivia and her grandfather.
Or I should say, Amp dumped me off the top of his spaceship from about eight feet in the air, and I face-planted on some sha
rp pine needles near Olivia and her grandfather. Then Amp landed safely, all comfy cozy inside his spaceship.
Olivia and her grandfather had been waiting for us to return to make our getaway, which I now realized would be harder than we’d expected. The dark woods around us were filled with the sound of men shouting orders. Beams of light flashed through the trees. An army helicopter with a superbright searchlight roared above us.
The soldiers in the fort from which we had just escaped were coming after us. They were determined not to let us get away easily.
Olivia emerged out of the darkness to help me up. “Why . . . why are you wearing only your unmentionables? Wh-where are your pants?” she stammered. “And your shoes and socks and shirt?”
“Kind of hard to explain,” I said, gasping and plucking off dried pine needles. I stumbled, trying to shake the dizziness. The woods spun around me. I put my hands on my knees and concentrated on not throwing up.
Olivia ran to the truck. Her grandfather was on one knee by Amp’s ship. It steamed visibly and had a slight golden glow to it. It looked more futuristic out here in the woods than it had under the wool blanket in my closet, which was where it had sat, unused, for weeks.
“We’ve got to get out of here,” Olivia said, handing me her grandfather’s vest.
I zipped it up, but it was way too big. I felt like I was wearing a dress.
“Step into these,” Olivia demanded, setting down huge, waterproof hunting boots.
I did as she said, and my toes searched the inside of the giant boots for warmth. I glanced down at myself and held my arms out. “I look ridiculous!”
