Forces of Nature (8 page)

Lost and Found

T
hey hadn't run more than ten minutes before they saw the bright glow of lights ahead.

Zack was just feet behind Olivia, and they were both breathing hard from navigating at full speed through a nearly ink-black forest.

Zack heard voices ahead. “We did it,” he gasped as a tree branch snapped back and slapped him rudely in the face.

He ran into Olivia. She had stopped suddenly when she pushed her way through the last scrubby bush.

Zack peered over her shoulder and saw that campsite number thirteen was now a hive of activity.

There were easily thirty people standing around. Six green ranger trucks and five county sheriff jeeps were parked at odd angles around the campsite. All the bright headlights and several floodlights on tripods forced the kids to shield their faces while their eyes adjusted to the brightness.

Zack could see several rangers leaning over a large map draped over the hood of one of the jeeps. One by one they looked up at the kids.

The buzz of voices steadily grew silent as the stunned crowd all took notice of the two mud-covered, panting kids who had entered the circle of light. Everyone froze. The only noise was the squawk of the police radios inside each of the vehicles.

Zack looked down.

Olivia was secretly holding Amp behind her back in a fist. She was nudging Zack so he'd take Amp. She was squeezing him too tight. It looked like his head was about to burst. Staying hidden behind Olivia, Zack took Amp from her hand and in one smooth movement stuffed his alien friend into his pocket.

Zack released a big sigh of relief; there was no way Amp's invisibility could work on this many people at once.

Smokey barked a greeting and that seemed to snap the crowd out of their stunned silence.

Zack's mom, dad, and brother burst out of the crowd and ran to them. Zack could see Mom had been crying and she had a large orange blanket wrapped around her. They all collapsed into a giant family hug with a laughing Olivia smashed in the middle. Mom was weeping in relief and Dad wiped tears from his face with the back of his hand.

“We thought you guys were goners,” Taylor said.

“Oh, hush, honey,” Mom sniffed. “Thank goodness you're both safe!”

“And Smokey, too,” Taylor said, falling to his knees and hugging the dog. “We thought you'd run off with the bears, old boy!”

“Oh, my brave little boy,” Mom said, hugging Zack so tight he thought his bones might break. Then she turned and put Olivia in a serious bear hug.

“This small army was about to head out into the forest to find you guys,” Dad said, ruffling the hair on top of Zack's head. “They were just
waiting for the bloodhounds to arrive.”

Ranger Davis approached with a big smile on his face. “Well, this makes our job a whole lot easier! You're both all right? Nobody hurt?”

“I'm hungry,” Olivia said.

“And I've got a wicked blister,” Zack said, which brought a round of relieved laughter from the gathered crowd.

Everyone wanted to hear their story, so they walked over to the hood of the nearest ranger truck and Zack pulled out the pieces of their compass and demonstrated it for everyone. It still worked.

“Wow,” Ranger Davis said, clearly impressed with the two kids before him. “Two tough survivalists,” he said, shaking his head in disbelief. “Gives me hope for the future.”

Taylor stepped through the crowd and studied their small compass and looked a little jealous for all the attention his big brother was receiving. But he didn't say anything.

Soon the crowd began to leave the campsite after another round of well wishes.

Zack could see that a sturdy-looking temporary bridge had been placed over the creek where the wooden bridge had been washed away. It felt as if he'd been gone for a week.

Zack and Olivia each ate two hot dogs in two minutes, the hot food feeling great as it dropped down into their empty stomachs. They chugged on fresh water bottles. Zack let out a thunderous burp and almost felt like his old self again.

As the large temporary lights that had been set up around the campsite began to get switched off, they all piled into the car, which had been packed
and prepped for a speedy escape.

They had only been there for one night, but nobody seemed to want to risk spending another one there. Clearly, everyone was ready to cut their losses.

The whole day had all been so exciting and intense, Zack almost failed to notice the foul smell in the car. At first he thought Amp—still hiding in his pocket—was trying to pull one of his mind-smell tricks, but Taylor set him straight before he could panic.

“That terrible smell is bear pee,” Taylor explained. “They peed all over our car.”

Zack smiled. “I guess it could have been worse, right?”

Science Geek

T
hree hours later, the car hummed through the night.

Zack sat quietly in the hushed car's rear seat for the rest of the ride.

Taylor was asleep and giggling occasionally, his grinning face pressed into Olivia's shoulder. Smokey jerked at Zack's feet, dreaming of who knows what. Dad snored softly every six seconds or so. Mom was hunched behind the steering wheel, concentrating on the road, like a determined mama bear rescuing her baby bears.

Even Olivia, who was sitting between Zack and Taylor in the backseat, had fallen asleep. Zack couldn't remember ever seeing her sleep before. She looked pretty normal, peaceful even. She was definitely not a McGee.

Zack watched Amp do push-ups on his knee in the shifting light from passing headlights. He was trying to get back in shape. Too many SweeTarts, Ritz Crackers, and gummy bears can make even an alien fat.

Zack thought about his friend and how his deep knowledge of science stuff had saved them. Zack loved how they had made that compass. It showed him that knowledge about the world around you could really be important, useful, and—dare he think it?—fun!

He had never considered science “fun” in his life.

Before this trip, science had always been boring stuff to be avoided, the blah-blah-blah you had to memorize for a quiz, not something that had to do with real life.

But now he knew differently. And he wanted to learn more. He shook his head at himself. “Science geek,” he whispered.

Amp had flipped over and was now doing his weird Erdian version of sit-ups. It looked like an invisible hand was karate chopping his belly over and over.

Zack knew he might only have a few weeks left with his Erdian pal. He'd be heading home soon—either after the invasion or to stop it. But for now Zack wanted to learn whatever he could from Amp. And he was sure that Amp would jump at the chance to show off.

He didn't know how, but the chance that he would become a scientist, or inventor, or engineer, or some kind of doctor when he grew up had mysteriously become a possibility—that is, if he didn't become a pro ballplayer.

He knew it was possible.

Zack looked out at the darkness and smiled. If Amp had taught him one thing, it was that anything was possible.

Y
ou may already be familiar with a compass—the almost magic-seeming navigation device whose red-tipped needle always points north. They've been around for centuries, helping adventurers navigate since around the year 1000 AD. Compasses can be mesmerizing, whether you're holding one and spinning in circles as you watch the needle stay steady, or directing the needle back and forth with the invisible magnetic field from a nearby refrigerator magnet.

And one of the best parts about a compass is that it's so simple to build! In fact, you can build an improvised and fully functional compass out of parts you can find at home.

For this experiment, you will need:

•
  
A paper clip

•
  
A refrigerator magnet

•
  
Something that's buoyant in water, like a piece of cork or Styrofoam (preferably with a flat side to it)

•
  
A plastic bottle cap

•
  
Water

•
  
MOST IMPORTANT: An adult to help

1.
    
To begin, unbend the first two curves of the paper clip. At the second curve, bend it back and forth lots of times until the metal “gets tired” (fatigues) and comes apart. Do your best to straighten the unbent piece. This will be the compass needle.

2.
    
Now it's time to magnetize the needle just like Zack did. Hold the tip of the needle in one hand and the refrigerator magnet in the other hand. Holding the refrigerator magnet in the same orientation, drag it lengthwise down the needle, starting by your fingers and swiping right off the end. Bring the magnet back around for another pass without making contact with the needle until it's by your fingers again. Now repeat 99 times!

3.
    
Your needle is now magnetized. Even though it's not a very strong magnet, it's still having some force exerted on it by the Earth's magnetic field. It wants to turn and align with the field, pointing north! The next step is to allow it to turn more easily by letting it float in the bottle cap. Break pieces off of your floaty piece (the cork or Styrofoam) until it's a little bit round and fits easily in the bottle cap. If it has a flatter side, put that side down toward the water. Poke the needle through the Styrofoam or cork so the needle is held steadily parallel to the bottom flat side. You might want an adult to help with this part.

4.
    
Ready to test! Fill the bottle cap with water until it's just about full. It's even OK if the cap is a tiny bit over-full, with surface tension helping hold the water in. Gently place the floaty needle into the water. You might have to adjust it lengthwise back and forth till the needle is parallel to the surface the compass is on. This can be important, since an unbalanced needle can pull itself downward against the bottle cap and not spin easily enough.

 

Test 1!

First, check to ensure your needle is magnetized. Bring the refrigerator magnet close by and swing it back and forth slowly around your compass. Does the needle spin? Great! Your compass is already showing you it can align to the magnetic field coming out of your refrigerator magnet! How far away can you hold the magnet and still make your compass spin?

 

Test 2!

Now take the refrigerator magnet far away from your compass. You should see the needle spin slowly to align itself north/south. Once it's aligned, try rotating the bottle cap underneath the needle. The needle should stay aligned to the Earth's magnetic field! Remember how far away your refrigerator magnet could affect the compass direction? It was probably on the order of about a foot, max. Now think: how far away from the north pole do you live? Probably pretty far. Think about how strong of a magnet the Earth's molten iron core is, to be able to point your compass needle from that far away! Pretty strong indeed.

 

Which way's north?

You've had success! Your needle is clearly aligning to Earth's magnetic field! But which way is actually north? Without some other point of reference to compare to, you don't exactly know which end of your needle you should paint red so you can tell north from south when you're out in the field. You can use another compass, or a map and a geographical feature, to give yourself a reference point. By comparing an approximate direction you know is north to where the needle is pointing, you should easily be able to tell which end of the needle is pointing toward magnetic north. Zack, Olivia, and Amp used the sunset to reference an approximate direction for west, which will always be to the left of the compass needle.

 

Troubleshooting:

A compass is a sensitive instrument, meaning not only can it detect faint signals like a faraway magnetic field, it can also be interfered with easily by other things you're not trying to measure. Here are some things to think about if your compass isn't working exactly as expected:

•
  
Make sure your needle is magnetized. You should see the needle moving when you wave your refrigerator magnet nearby. If it's not wiggling around in response to the magnet, swipe the magnet down the length of the needle in one direction a lot more times.

•
  
If the needle can't spin easily, it won't be able to point north/south, because the forces exerted on it by the Earth's magnetic field are very small. Make sure the Styrofoam or cork float isn't crashing into the edges of the plastic bottle cap. Try adjusting the water level as well, to make sure it's centered.

•
  
Check to make sure the needle is parallel to a horizontal surface, like a table.

•
  
Just like the refrigerator magnet's magnetic field is strong enough to override the Earth's
magnetic field effects on the compass needle, other fields from nearby objects might also interfere. Make sure there are no other magnets or large pieces of steel nearby. A pair of headphones, a cell phone, or even a cookie sheet can mess up your compass's sensitivity if they're too close. Isolate your compass to get a good reading.

•
  
Make sure the needle is nice and straight.

 

What's actually going on here?

Magnets are crazy! Isn't it cool how you can hold a magnet in each hand and feel the forces they exert on each other right through your skin and bones, without even being able to see anything? Believe it or not, magnetic fields can be produced in a few different ways, and even completely natural rocks can have permanent magnetic fields just like the magnets on your refrigerator.

There are a few different types of magnetism, but the kind we encounter most often is called “ferromagnetism.” The “ferro” part stands for
iron
, which is present in both the Earth's core and in the steel that makes up much of our engineered world, including paper clips.

In the atoms of the ferromagnetic material, like the paper clip, the tiny particles called electrons each act a little bit like tiny magnets themselves. When they get stuck together and form a lump of material, groups of them tend to align themselves in the same direction. We call those “magnetic domains.” It would be like if you were in a classroom at school, and everybody split into groups of friends who were each looking at different
parts of the room. When the teacher says “pay attention up front please!” and all of the groups face forward, it's like the classroom got magnetized! It's just that to magnetize the compass needle, you have to have the “teacher” (the refrigerator magnet) ask the “class” (the electrons and magnetic domains) to all face the front about 100 times in a row before they all pay attention.

To learn more, look up some articles about ferromagnetism. You can use your compass to help you navigate to the library! And while you're there, check out
Alien in My Pocket: The Science UnFair
to read about Zack's adventures building magnets that run off of electricity. Electromagnets!