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As a pilot for the first fighter wing, flying the most advanced fighter in the world, the

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F-A-22 Raptor, I use electronics in my work every day.

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From the heads-up display, which shows me how fast I'm going and how high I'm flying,

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to the latest stealth technology.

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The Air Force makes math, science, and technology a way of life.

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You can use math, science, and technology, along with the treehouse detectives, as they

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investigate the magnetosphere in the case of the technical knockout.

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Stay tuned and study hard, and one day you can trade your video game controls for the

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controls of one of these.

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Come on now, and learn about math, science, and technology.

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NASA ScienceFiles

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Discovering the world we're in

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Doing cool experiments

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NASA ScienceFiles

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NASA ScienceFiles

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NASA ScienceFiles

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Be sure to look for the answers to the following questions.

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What are some other uses for a GPS?

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What star can we use to find north?

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How did the Vikings navigate without a compass or the stars?

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When you see this icon, the answer is near.

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Great, keep up the good work, and keep looking.

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Hi, I'm glad you're here.

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We're close to finding our first geocache.

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You guys are quick.

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I'm still trying to figure out this whole geocaching thing.

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It's simple.

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It's like a scavenger hunt using a Global Positioning System device, or GPS.

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You create a cache, which is just a container to hold your treasure.

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Then you take it to a public park or another public area, and you hide it,

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using your GPS to note its exact location.

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Because you have to post the exact coordinates on the Internet.

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Exactly.

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So other GPS users can find the treasure in your cache.

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They take your treasure?

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They have to replace your treasure with a new treasure so others can find it.

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That makes sense.

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My mom told us all about geocaching when she gave us our geography assignment.

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What I can't figure out is how a GPS works.

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How does this thing know your exact location?

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And do I really want anyone to know my exact location?

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Well, you would if you were lost.

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That's true.

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I guess I need to do more research on how a GPS works.

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I know it uses satellites, but I'm not sure how.

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While you're up, do you think you could find the coordinates for some chocolate?

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It was a simple task.

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All you had to do was put batteries into the GPS.

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Batteries have nothing to do with the problem.

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It must be something...

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If the GPS doesn't work, or if it says we're somewhere we're not,

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then basically, we're lost.

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I can't believe it.

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Our position keeps changing, but we haven't moved.

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The GPS is giving us a lot of different coordinates.

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According to my compass, in our last coordinates...

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Let me see.

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North is over here.

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I think I'd better get in touch with the other treehouse detectives.

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Bianca, come here. Listen to me.

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I can't figure it out either.

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Just stay calm and keep taking good notes.

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We'll see what we can find out later. Over.

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That can't be good.

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No, it isn't.

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Everything was going fine,

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and then both teams reported having problems with their GPS.

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Well, from the sketchy radio communications,

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it sounds like they're receiving random coordinates.

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Yes, but they weren't even moving.

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Hmm.

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Identifying a location precisely is what geocaching is all about.

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Sounds like we need to go to the problem board.

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Good idea. So what do we know?

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We know that both teams are using GPS devices,

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and that everything was going fine until just recently.

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Now they're experiencing some kind of technical problems.

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Right.

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Both GPS devices began to give incorrect location coordinates at about the same time.

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We also know that a GPS uses information from satellites to give precise locations.

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So what do we need to know?

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We need to know how GPS, or Global Positioning Systems, work.

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What goes on under your hard plastic cover?

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What makes you tick?

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I don't know where we need to go,

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but someone needs to go outside and take a break.

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Did you say something?

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Yes. Where do we need to go?

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I'm meeting with Dr. D later this afternoon via the Internet

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to discuss my project on the history of navigation.

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Maybe he can help.

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Good. I'm meeting with Mr. Charles Cope

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to pick up some information about the NASA SHARP program for my brother.

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Mr. Cope is a pilot for NASA.

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Pilots use GPS.

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Maybe he can answer some of our questions about how GPS works.

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Pilot from NASA?

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I'm sure he'll be able to help.

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Don't forget to take a get-up-and-go sheet for some serious note-taking.

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Visit the NASA SciFiles website

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to find some cool research tools for your own investigation.

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Guys, we're making progress.

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The GPS now says we're in Virginia.

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Of course it says we're in the middle of the Chesapeake Bay.

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But we're making progress.

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Guys?

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Guys?

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I hope that helps your brother out.

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Thanks for the information on the SHARP program.

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My brother is very excited about it.

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You're welcome.

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May I ask you another question?

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It's about global positioning systems.

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Of course. What would you like to know?

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As a pilot for NASA, how do you use GPS when you're flying?

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With GPS's unique ability to provide an exact location at any second,

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pilots rely on that for accurate navigation.

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That is pretty important when you're flying.

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Yes, knowing exactly where you are helps to keep the plane clear of obstacles and mountains

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and get you to your destination safely.

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How does GPS help you navigate?

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GPS devices on aircraft are very similar to the ones you use for geocaching,

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just a little more sophisticated.

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They show great detail accurately displayed on a graphic map.

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We've learned how important accurate maps are.

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Yes, and having the capability to always know where you are,

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combined with an accurate map display,

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greatly adds to the situational awareness and to the safety of the flight.

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What would happen if the GPS device went out while you were flying?

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It might make the aircraft unable to fly and land in all types of bad weather.

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However, aircraft aren't dependent upon GPS.

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All planes and their pilots have the ability to fall back on traditional modes of navigation

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that were used prior to GPS.

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Just like we had to rely on our good old compass when our GPS went out.

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Exactly. At worst, it would be an inconvenience for the pilot.

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But he or she would be quite capable of safely flying the aircraft.

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That's good to know. Are there any other uses for GPS?

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Absolutely. There are all types of navigational uses for GPS.

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Oil companies use GPS to help them drill for oil.

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Farmers even use GPS to help them plow their fields.

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Some have even used GPS to locate a stolen vehicle.

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Most activities that benefit from knowing an exact position on Earth use GPS.

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Wow, I never realized so many people could use GPS.

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Thanks, Mr. Cope.

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Maybe we could see GPS in action by taking a quick ride on one of your research planes.

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I didn't know you and your brother were interested in flying.

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The weather wasn't cooperating for our flight, but it was great to learn more about GPS.

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I hope Jacob's meeting with Dr. D goes well.

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We still have a lot to learn about GPS and navigation.

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I'm in Oslo, Norway, for the World Year of Physics.

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But now I'm studying some of the history and culture of this great country.

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World Year of Physics

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Wow, I better get to the Viking Ship Museum for my video conference.

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I've got to hand it to the Vikings.

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How they found their way across the Atlantic Ocean without maps is amazing.

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Well, they didn't have maps like ours, but they were pretty sophisticated navigators.

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Hi, Dr. D. I was beginning to wonder if you were going to find the museum.

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Well, it's easy to get distracted when you're doing research.

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And soon I'll be going to Andenes above the Arctic Circle to see the Northern Lights.

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Dr. D, isn't the Alomar Lidar Observatory in Andenes?

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Yes, but how do you know about the observatory in Andenes?

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Ulla and Nina, some of our fellow geocachers, live there.

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And they also happen to be members of the NASA Sci-Files Kids Club.

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That's cool. If you send me their coordinates, I can meet them.

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Speaking of coordinates, as I mentioned in my email, I have some questions about the history of navigation.

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Where do you want to start?

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Didn't the Vikings discover America about 1000 A.D., long before Columbus?

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That's right. The Vikings were excellent navigators and shipbuilders.

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This Viking ship, made of oak, is called the Oseberg.

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It is 22 meters long and was likely the burial ship of a Viking queen.

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The Gokstad was probably built around 890 A.D.

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In addition to sails, it also had 16 pairs of oars.

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In 1893, a replica of the Gokstad sailed from Norway to Canada in 28 days, without the aid of a compass.

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Wow, that's amazing!

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How do they navigate without a compass?

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The Vikings probably used stars to navigate.

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A star named Polaris, which is located above the Earth's north pole, can be used to find north.

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I know. Polaris is sometimes called the North Star.

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It's always in the same place in the sky, and you use the Big Dipper to find it.

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Very good. But when the Vikings sailed in the summer months, they would have had difficulty finding the North Star.

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Why is that?

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Because Norway is so far north, there are places where the sun never sets in the summer.

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That's why it's called the Land of the Midnight Sun.

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Even in southern Norway, it doesn't get really dark at night.

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Dr. D., how would they navigate without a compass or the use of the stars?

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Lots of ways. For example, they relied upon landmarks.

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They used ocean currents, prevailing winds and swells, and they observed the migrations of birds and whales to find their way.

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Is it possible that they used the sun?

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Yes. They apparently used the sun's shadow and the rising and setting positions of the sun to find north.

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Okay. And if there are clouds?

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Some people think they used a sunstone to locate the rising or setting sun when there were clouds on the horizon.

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I have a piece right here.

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How does it work?

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It's called Iceland's bar.

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Put a dot on top and look through it, you'll see two dots.

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You rotate it until both dots are equally dark, then the crystal points toward the sun.

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That's pretty ingenious.

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Of course they would have loved modern navigational technology like this sextant, a seagoing clot, or especially a GPS.

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Our GPS, however, is causing us some problems.

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What do you mean?

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It's giving us lots of random coordinates, even when we're not moving.

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Interesting. That makes it hard to find the cache.

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I have a friend at NASA Langley Research Center who works a lot with global positioning systems.

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I'll email you his information. I'm sure he can help you.

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Until then, I can tell you where to get a good sunstone.

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Thanks, Dr. D. But after I finish my research, I think I'll just give him a call.

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What about this one?

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If we were putting Jacob's bike in our cache, I'd say great.

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Remember, we have to hide this when we're finished.

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Plus, I'll never get that on the plane.

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Hmm. I wonder what my profit margin would be for these plastic containers in a yard sale.

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Note to self. Investigate long-term investment potential in plastics.

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Did you read Bianca and Jacob's get-up-and-go sheets?

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Yes. And we still need to learn about how satellites and GPS work if we want to complete our assignment.

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Dr. D. mentioned talking to a friend of his at NASA.

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Yes. Maybe we can meet him after we finish making our geocache.

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And finding supplies for your camping trip.

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By the way, how is it possible that you get to go on a camping trip to Colorado?

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Isn't that expensive?

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These, Catherine, are the benefits of being on the board of a high-profile financial institution.

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You're a member of the board?

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Well, no. My mom is. She's taking me camping after our meetings.

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I'll tell you all the details when you take me to the airport.

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I can't take you to the airport. I can't drive yet.

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Oh. Right. Note to self.

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Also, investigate investment opportunities in transportation companies.

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So what's up? How will the treehouse detectives find the geocache?

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What should they do if their GPS devices go out again?

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Find out in the next exciting chapter of The Case of the Technical Knockout.

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Be sure to look for the answers to the following questions.

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How do GPS receivers detect their distance from satellites?

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What is the electromagnetic spectrum?

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What is static electricity?

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When you see this icon, the answer is near.

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Dr. D's friend, Mr. Gnaud, works at NASA Langley Research Center.

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He develops new instruments for global positioning systems and has agreed to meet with us.

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If anyone can help us learn more about GPS, he can.

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GPS, or Global Positioning System, is a constellation system of 29 Earth-orbiting satellites

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that were originally designed by the U.S. military in the 1970s as a navigation system.

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Twenty-nine sounds like a lot of satellites.

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Why do you need so many?

242
00:14:58,840 --> 00:15:03,840
It takes 24 satellites to provide global coverage, leaving five spares.

243
00:15:03,840 --> 00:15:10,840
The orbits are arranged so that at any given time, anywhere on Earth, there are at least four satellites visible.

244
00:15:10,840 --> 00:15:13,840
Why do four satellites need to be visible?

245
00:15:13,840 --> 00:15:17,840
Your GPS receiver needs four satellites in order to determine its own location.

246
00:15:17,840 --> 00:15:20,840
How does our GPS locate itself?

247
00:15:20,840 --> 00:15:24,840
Using a simple mathematical principle called trilateration.

248
00:15:24,840 --> 00:15:28,840
I'm not sure simple and trilateration should be used in the same sentence.

249
00:15:28,840 --> 00:15:30,840
What is trilateration?

250
00:15:30,840 --> 00:15:36,840
It's kind of tricky to explain in three-dimensional space, so let's start with a two-dimensional example.

251
00:15:36,840 --> 00:15:40,840
Let's say you're totally lost somewhere in the U.S. and your GPS is not working.

252
00:15:40,840 --> 00:15:43,840
Like us yesterday when we couldn't find our geocache.

253
00:15:43,840 --> 00:15:51,840
As you are trying to find where you are, a friendly person tells you that you are 1,000 kilometers from Boise, Idaho.

254
00:15:51,840 --> 00:15:53,840
Do you know where you are?

255
00:15:53,840 --> 00:15:56,840
No, I could be 1,000 kilometers in any direction from Boise.

256
00:15:56,840 --> 00:15:57,840
Exactly.

257
00:15:57,840 --> 00:16:05,840
Now let's say another friendly person comes by and tells you that you're 1,110 kilometers from Minneapolis, Minnesota.

258
00:16:05,840 --> 00:16:07,840
Do you know where you are?

259
00:16:07,840 --> 00:16:09,840
Not yet, but I'm getting closer to my location.

260
00:16:09,840 --> 00:16:14,840
That's right. Now you have two choices, but you still don't know where you are.

261
00:16:14,840 --> 00:16:21,840
Finally, another friendly person informs you that you are 990 kilometers from Tucson, Arizona.

262
00:16:21,840 --> 00:16:23,840
Now do you know where you are?

263
00:16:23,840 --> 00:16:27,840
It looks like I'm in Denver, Colorado, which of course I will be soon.

264
00:16:27,840 --> 00:16:34,840
The same concept works in three-dimensional space, but instead of circles, you need to think in terms of spheres.

265
00:16:34,840 --> 00:16:37,840
And the satellites are the friendly people telling you how far you are from a place.

266
00:16:37,840 --> 00:16:46,840
That's right. If you know your distance from Satellite A, you could be anywhere on a huge imaginary sphere at that radius.

267
00:16:46,840 --> 00:16:55,840
If you know your distance from Satellite B, you can overlap the first sphere with the second sphere and they intersect in a perfect circle.

268
00:16:55,840 --> 00:17:01,840
So if you know the distance to a third satellite, you get a third sphere which intersects with the circle at two points.

269
00:17:01,840 --> 00:17:07,840
Very good. And the Earth acts as the fourth sphere, so you can eliminate the point in space because you're on Earth.

270
00:17:07,840 --> 00:17:09,840
So do you only need three satellites?

271
00:17:09,840 --> 00:17:19,840
An approximate position can be found with three satellites, but to improve accuracy and get precise altitude information, four or more are better.

272
00:17:19,840 --> 00:17:22,840
How do GPS receivers know how far they are from the satellite?

273
00:17:22,840 --> 00:17:30,840
They analyze the high-frequency, low-powered radio signals from the GPS satellites and calculate the time the signal traveled.

274
00:17:30,840 --> 00:17:32,840
Do satellites have stopwatches?

275
00:17:32,840 --> 00:17:36,840
No. The satellites need to be more accurate than a stopwatch.

276
00:17:36,840 --> 00:17:43,840
The satellites use a very accurate atomic clock which produces exact time-coded signals.

277
00:17:43,840 --> 00:17:45,840
And what happens if a satellite malfunctions?

278
00:17:45,840 --> 00:17:52,840
It's possible. Again, that's why we have 29 satellites when only 24 are needed, leaving a few spares.

279
00:17:52,840 --> 00:17:53,840
It helps to have extra.

280
00:17:53,840 --> 00:17:59,840
True. Here at NASA, we use GPS to determine the position of aircraft and satellites.

281
00:17:59,840 --> 00:18:04,840
And we also are developing a system to perform remote sensing of the environment.

282
00:18:04,840 --> 00:18:10,840
All of these tasks require precision information. Spare satellites make sure we get the data we need.

283
00:18:10,840 --> 00:18:14,840
Cool. NASA is always doing amazing things.

284
00:18:14,840 --> 00:18:22,840
Mr. Ganell, what would happen if your GPS was only receiving a signal from one or two satellites? Would you get incorrect results?

285
00:18:22,840 --> 00:18:29,840
No. Usually, your GPS device will let you know that it doesn't have enough satellites to calculate an accurate position.

286
00:18:29,840 --> 00:18:31,840
Sounds like we need to do some more research.

287
00:18:31,840 --> 00:18:33,840
Thanks, Mr. Ganell.

288
00:18:33,840 --> 00:18:36,840
You're welcome. And good luck with your geocaching.

289
00:18:53,840 --> 00:18:59,840
We're about 25 meters from where we were, and when we last experienced some problems with the GPS. Over.

290
00:18:59,840 --> 00:19:04,840
Can you still hear me? The radio's coming in loud and clear, too. Keep us posted.

291
00:19:04,840 --> 00:19:07,840
We shouldn't really assume whether or not the technical problem was permanent.

292
00:19:07,840 --> 00:19:09,840
My guess is that one of the satellites was broken.

293
00:19:09,840 --> 00:19:11,840
Now, Jacob, don't jump to conclusions.

294
00:19:11,840 --> 00:19:15,840
And besides, Mr. Ganell said that 29 GPS satellites orbit the Earth.

295
00:19:15,840 --> 00:19:18,840
It's possible, but not likely that they're all good.

296
00:19:18,840 --> 00:19:21,840
I guess you're right. But what other explanation is there?

297
00:19:21,840 --> 00:19:25,840
Either way, if we want to complete our assignment, we have to make sure this works.

298
00:19:27,840 --> 00:19:30,840
It should be another 8 meters. A little to the right.

299
00:19:30,840 --> 00:19:32,840
I don't see anything.

300
00:19:32,840 --> 00:19:34,840
Another 5 meters.

301
00:19:34,840 --> 00:19:36,840
Oh, wait. I see something.

302
00:19:40,840 --> 00:19:43,840
This is so cool. I can't believe we found it.

303
00:19:44,840 --> 00:19:47,840
This is so cool. I can't believe we found it.

304
00:19:47,840 --> 00:19:52,840
RG to Headquarters. We've found the geocache. I repeat, we have found the geocache.

305
00:19:52,840 --> 00:19:55,840
At the exact coordinates listed on the website.

306
00:19:55,840 --> 00:19:59,840
Good work, guys. Are you sure the coordinates are correct?

307
00:19:59,840 --> 00:20:03,840
We're sure. We've double-checked and double-confirmed. Mission accomplished.

308
00:20:03,840 --> 00:20:05,840
We're returning to Headquarters. Over.

309
00:20:05,840 --> 00:20:09,840
It looks like you were right. I shouldn't have jumped to a conclusion.

310
00:20:09,840 --> 00:20:12,840
Clearly, the satellites and the GPS devices are working properly.

311
00:20:12,840 --> 00:20:16,840
And that's a good thing. But we still don't know what caused the problem in the first place.

312
00:20:16,840 --> 00:20:18,840
Let's go to the problem board.

313
00:20:18,840 --> 00:20:19,840
Okay. What do we know?

314
00:20:19,840 --> 00:20:23,840
We know that our GPS malfunctioned in two different locations at the same time.

315
00:20:23,840 --> 00:20:28,840
And we also know from Catherine and Tony's report that satellites communicate with GPS devices through radio waves.

316
00:20:28,840 --> 00:20:32,840
Of course. And now we know that the problem was only temporary.

317
00:20:32,840 --> 00:20:37,840
True. The satellites and GPS devices are working fine now. So what do we need to know?

318
00:20:37,840 --> 00:20:40,840
We need to know more about radio waves and how they might be affected.

319
00:20:40,840 --> 00:20:43,840
It might also help if we knew anyone else who had a similar problem.

320
00:20:43,840 --> 00:20:44,840
So where do we go?

321
00:20:44,840 --> 00:20:48,840
Let's email Ulla and Nina in Norway and see if they had the same problem on the same day.

322
00:20:48,840 --> 00:20:52,840
Great idea. We may not have this problem solved, but we're making progress.

323
00:20:52,840 --> 00:20:57,840
Yes. And we need to make a report for Tony. Maybe he can help us from Colorado.

324
00:20:57,840 --> 00:21:02,840
For some great ideas on creating your own reports, visit the Treehouse on the NASA SciFiles website.

325
00:21:10,840 --> 00:21:13,840
We read about the treehouse detectives' problem with their GPS.

326
00:21:13,840 --> 00:21:17,840
But we weren't much help. We were not geocaching on the same day.

327
00:21:17,840 --> 00:21:20,840
And we haven't had any problems with our GPS.

328
00:21:20,840 --> 00:21:25,840
We decided to ask Dr. D about it when we meet at the Alomar LiDAR Observatory.

329
00:21:27,840 --> 00:21:31,840
I'm excited to finally be here at the observatory. I've read so much about it.

330
00:21:31,840 --> 00:21:33,840
Dr. D, what kind of research is done here?

331
00:21:33,840 --> 00:21:38,840
The scientists are investigating the middle atmosphere using lasers like this and radar instruments.

332
00:21:38,840 --> 00:21:41,840
Isn't radar what the police use to bounce off cars and see how fast they're going?

333
00:21:41,840 --> 00:21:44,840
And weathermen use it to track rain and snow storms.

334
00:21:44,840 --> 00:21:49,840
Exactly. Radar sends out a beam of light which is reflected off the atmosphere and is then analyzed.

335
00:21:49,840 --> 00:21:53,840
Did you just say that radar sends out a light beam? I thought that radar used radio waves.

336
00:21:53,840 --> 00:21:58,840
It does, but radio waves are a form of light. There are many forms of light that are not visible.

337
00:21:58,840 --> 00:21:59,840
Like what?

338
00:21:59,840 --> 00:22:03,840
Well, for example, this observatory uses microwave light to measure water vapor,

339
00:22:03,840 --> 00:22:08,840
infrared light to detect clouds, and ultraviolet light to measure the ozone layer.

340
00:22:08,840 --> 00:22:10,840
I've heard of ultraviolet light, but it's not visible.

341
00:22:10,840 --> 00:22:14,840
All these different forms of light are part of what is called the electromagnetic spectrum.

342
00:22:14,840 --> 00:22:20,840
Every form of light travels at 300 million meters per second in a vacuum and has a wavelength.

343
00:22:20,840 --> 00:22:24,840
We learned that the wavelength is the distance between the crest of two successive waves.

344
00:22:24,840 --> 00:22:28,840
That's right. Some radio light has wavelengths that are hundreds of meters long,

345
00:22:29,840 --> 00:22:34,840
where ultraviolet light wavelengths are very tiny, only about one ten-thousandth of a millimeter.

346
00:22:34,840 --> 00:22:36,840
That's a big difference.

347
00:22:36,840 --> 00:22:41,840
It is. Light also has a frequency, which is its rate of vibration.

348
00:22:41,840 --> 00:22:47,840
Here, hold on to this spring. I'm going to make it vibrate and create what's called a standing wave.

349
00:22:59,840 --> 00:23:02,840
The faster you move your hand, the shorter the wavelength.

350
00:23:02,840 --> 00:23:05,840
Exactly. And the shorter the wavelength, the higher the energy.

351
00:23:05,840 --> 00:23:07,840
Which light has the most energy?

352
00:23:07,840 --> 00:23:13,840
That would be gamma rays, followed by X-rays, ultraviolet, visible light, infrared, and radio waves.

353
00:23:13,840 --> 00:23:16,840
Wow. I still can't believe that they're all called lights.

354
00:23:16,840 --> 00:23:22,840
Dr. D, the treehouse detectives want to know more about the radio waves the satellite uses to communicate with GPSs.

355
00:23:22,840 --> 00:23:23,840
Good question.

356
00:23:23,840 --> 00:23:26,840
First, you need to know that there are a lot of different types of radio waves.

357
00:23:26,840 --> 00:23:30,840
GPS satellites communicate with a type of radio wave called microwave.

358
00:23:30,840 --> 00:23:32,840
I've heard of shortwave radio.

359
00:23:32,840 --> 00:23:35,840
That's another type. There are also AM and FM radio and TV.

360
00:23:35,840 --> 00:23:41,840
But GPS satellites communicate with microwaves because these pass easily through the atmosphere and are not absorbed.

361
00:23:41,840 --> 00:23:44,840
Are the other forms of light absorbed by the atmosphere?

362
00:23:44,840 --> 00:23:49,840
Not all of them. Ozone in the atmosphere is absorbed most, but not all of the ultraviolet light.

363
00:23:50,840 --> 00:23:54,840
Fortunately, most of the X-rays and gamma rays are also absorbed.

364
00:23:54,840 --> 00:23:56,840
But visible lights get through pretty easily.

365
00:23:56,840 --> 00:23:59,840
Yes, the atmosphere is transparent to visible light.

366
00:23:59,840 --> 00:24:05,840
I heard that some radio waves, like AM and shortwave radio, can bounce off the atmosphere and travel great distances.

367
00:24:05,840 --> 00:24:08,840
That's correct. But FM radio and TV don't.

368
00:24:08,840 --> 00:24:13,840
I also mentioned that all radio waves can be created by moving electrical charges.

369
00:24:13,840 --> 00:24:18,840
And the Kids Club members said you might want to learn more about electricity to solve your GPS problem.

370
00:24:18,840 --> 00:24:25,840
I agree. And if camping conditions aren't too primitive, I recommend that you look up Dr. Baganal,

371
00:24:25,840 --> 00:24:29,840
a friend of mine who studies electricity at the University of Colorado.

372
00:24:29,840 --> 00:24:33,840
I know that we use electricity all the time, but I'm not sure what it is exactly.

373
00:24:33,840 --> 00:24:38,840
It's a physical phenomenon associated with static and moving electrical charges.

374
00:24:38,840 --> 00:24:40,840
Oh, I get it.

375
00:24:40,840 --> 00:24:42,840
I'm sorry, would you repeat that again?

376
00:24:42,840 --> 00:24:44,840
I know. It's complex.

377
00:24:44,840 --> 00:24:48,840
Electricity doesn't have a simple explanation, nor is it easy to understand.

378
00:24:48,840 --> 00:24:50,840
So let's start with the basics.

379
00:24:50,840 --> 00:24:53,840
Take this plastic stick and rub it against this cloth.

380
00:24:53,840 --> 00:24:54,840
Okay.

381
00:24:59,840 --> 00:25:03,840
Okay. Now take this other one, made of the same material, rub it with the cloth,

382
00:25:03,840 --> 00:25:05,840
and see if you can try and put the ends together.

383
00:25:06,840 --> 00:25:08,840
It looks like one is pushing the other.

384
00:25:08,840 --> 00:25:10,840
Now rub this one, made of a different material.

385
00:25:10,840 --> 00:25:12,840
Okay.

386
00:25:12,840 --> 00:25:14,840
So now try and put them together.

387
00:25:21,840 --> 00:25:24,840
The different stick pulled the first stick. Why did it do that?

388
00:25:24,840 --> 00:25:28,840
Well, the difference between the two sticks is that they're made of the same material.

389
00:25:29,840 --> 00:25:32,840
The different stick pulled the first stick. Why did it do that?

390
00:25:32,840 --> 00:25:35,840
Well, let's figure it out. Do you remember the parts of the atom?

391
00:25:35,840 --> 00:25:39,840
Yes. There is a nucleus with protons and neutrons surrounded by electrons.

392
00:25:39,840 --> 00:25:44,840
That's correct. And the protons are positively charged and the electrons are negatively charged.

393
00:25:44,840 --> 00:25:46,840
And the neutrons are neutral.

394
00:25:46,840 --> 00:25:49,840
Very good. And positive and negative charges are attracted to each other.

395
00:25:49,840 --> 00:25:51,840
We call that the attractive force.

396
00:25:51,840 --> 00:25:53,840
Aren't all atoms basically neutral?

397
00:25:54,840 --> 00:25:59,840
Yes. But when you put different materials together, sometimes the parts of the atoms like to move.

398
00:25:59,840 --> 00:26:04,840
However, some nuclei like to hang on to their electrons stronger than other nuclei.

399
00:26:04,840 --> 00:26:08,840
The stronger nuclei gather electrons from the weaker nuclei.

400
00:26:08,840 --> 00:26:11,840
Is that what happened when I rubbed the two different sticks with the cloth?

401
00:26:11,840 --> 00:26:15,840
When you rubbed the first two sticks with the cloth, the electrons left the cloth and gathered on the sticks.

402
00:26:15,840 --> 00:26:19,840
And then because they were both negatively charged, they repelled each other.

403
00:26:19,840 --> 00:26:22,840
Because they were both negatively charged, they repelled each other.

404
00:26:22,840 --> 00:26:25,840
So why did the different sticks attract one another?

405
00:26:25,840 --> 00:26:28,840
Well, different materials cause electrons to move differently.

406
00:26:28,840 --> 00:26:33,840
Oh, I get it. With the different stick, the electrons gathered on the cloth, leaving the stick positively charged.

407
00:26:33,840 --> 00:26:37,840
Because once it was positively charged and the other one was negatively charged, they attract each other.

408
00:26:37,840 --> 00:26:39,840
Yeah, I think you've got it.

409
00:26:39,840 --> 00:26:44,840
So this kind of electricity is called static electricity because the charges are stationary and don't move.

410
00:26:44,840 --> 00:26:48,840
Now, shuffle your feet on the carpet and then touch this metal object.

411
00:26:48,840 --> 00:26:50,840
I have a bad feeling about this.

412
00:26:53,840 --> 00:26:54,840
Shocking.

413
00:26:54,840 --> 00:26:55,840
Can you explain why?

414
00:26:55,840 --> 00:27:00,840
I'll try. When I shuffled my feet, I gathered electrons from the carpet, making me negatively charged.

415
00:27:00,840 --> 00:27:03,840
That's correct. And what happened when you touched the metal object?

416
00:27:03,840 --> 00:27:07,840
The extra electrons jumped over to the metal, causing pain.

417
00:27:08,840 --> 00:27:13,840
Sorry, but you're right. It's an example of what we call current electricity.

418
00:27:13,840 --> 00:27:18,840
Watch what happens when I connect this end of the wire to this end of the hand generator.

419
00:27:18,840 --> 00:27:22,840
This looks like a complete circuit, where the light bulb is the load.

420
00:27:22,840 --> 00:27:26,840
When you turn the crank, you produce current, which is electrons flowing through the circuit.

421
00:27:26,840 --> 00:27:28,840
And the light bulb glows.

422
00:27:29,840 --> 00:27:35,840
Exactly. Now watch what happens when I connect the generator to this circuit near these compasses.

423
00:27:36,840 --> 00:27:40,840
Wait a minute. The compasses moved. Why'd they do that?

424
00:27:40,840 --> 00:27:43,840
Initially, the compass was pointing towards the Earth's North Pole.

425
00:27:43,840 --> 00:27:48,840
When we cranked the generator to make the current flow, a small magnetic field was created.

426
00:27:48,840 --> 00:27:55,840
This field caused the compass needle to swing, because the needle is itself a small magnet with a north and south end.

427
00:27:55,840 --> 00:27:59,840
Very interesting. The TRAILS detectives need to know about this.

428
00:28:00,840 --> 00:28:02,840
I didn't know that electricity was so cool.

429
00:28:02,840 --> 00:28:06,840
Dr. Bagnall said that flowing electricity creates a magnetic field.

430
00:28:06,840 --> 00:28:10,840
If that's true, then we need to know more about magnets and magnetism.

431
00:28:10,840 --> 00:28:14,840
So what's up? Will learning about magnets help the TREEhouse detectives?

432
00:28:14,840 --> 00:28:17,840
What other information do they need to solve the mystery?

433
00:28:17,840 --> 00:28:20,840
Find out in the next exciting chapter of TREEhouse!

434
00:28:29,840 --> 00:28:32,840
Next chapter of THE CASE OF THE TECHNICAL KNOCKOUT!

435
00:28:33,840 --> 00:28:36,840
Be sure to look for the answers to the following questions.

436
00:28:36,840 --> 00:28:38,840
What is solar wind?

437
00:28:38,840 --> 00:28:40,840
What does voltage measure?

438
00:28:40,840 --> 00:28:42,840
Name the layers of the atmosphere.

439
00:28:42,840 --> 00:28:44,840
Describe a convection cell on the sun.

440
00:28:44,840 --> 00:28:47,840
When you see this icon, the answer is near.

441
00:28:54,840 --> 00:28:56,840
What about a nice bag of beef jerky?

442
00:28:56,840 --> 00:29:00,840
Don't you think after a long day of hiking and geocaching, you might want some beef jerky?

443
00:29:00,840 --> 00:29:02,840
Or something of substance?

444
00:29:02,840 --> 00:29:04,840
Sorry, Jacob. Nothing perishable.

445
00:29:04,840 --> 00:29:09,840
We need to put things into our cache that are fun and interesting as treasure, not a meal.

446
00:29:09,840 --> 00:29:11,840
Well, I'm running out of ideas.

447
00:29:11,840 --> 00:29:12,840
What do you have so far?

448
00:29:12,840 --> 00:29:15,840
I had lots of food items.

449
00:29:16,840 --> 00:29:18,840
Signal flares...

450
00:29:18,840 --> 00:29:21,840
might be hazardous in the forest.

451
00:29:21,840 --> 00:29:24,840
Cache or a gift certificate?

452
00:29:24,840 --> 00:29:26,840
Why don't we just put travel bugs in our caches?

453
00:29:26,840 --> 00:29:29,840
Hi, RJ. What are travel bugs?

454
00:29:29,840 --> 00:29:31,840
They sure don't sound like treasure.

455
00:29:31,840 --> 00:29:34,840
My dad got me this one on the internet.

456
00:29:34,840 --> 00:29:36,840
It doesn't look like a bug.

457
00:29:36,840 --> 00:29:38,840
It's not a real bug.

458
00:29:38,840 --> 00:29:41,840
Each travel bug has its own unique tracking number.

459
00:29:41,840 --> 00:29:46,840
So when someone finds our cache, they take out the travel bug and place it into a different location.

460
00:29:46,840 --> 00:29:49,840
Then they look up on the internet the travel bug tracking number

461
00:29:49,840 --> 00:29:52,840
and type in the new location of the cache that they placed it in.

462
00:29:52,840 --> 00:29:55,840
So your travel bug could travel to geocaches all around town?

463
00:29:55,840 --> 00:29:57,840
Actually, it can travel the world.

464
00:29:57,840 --> 00:29:59,840
How would that work?

465
00:29:59,840 --> 00:30:01,840
Let's say we place a travel bug in our cache,

466
00:30:01,840 --> 00:30:04,840
and then someone from New York is geocaching in our area.

467
00:30:04,840 --> 00:30:07,840
They take the bug back to New York and place it in a cache in their city.

468
00:30:07,840 --> 00:30:10,840
Someone from London visits New York to geocache,

469
00:30:10,840 --> 00:30:12,840
and then they take it with them back to London.

470
00:30:12,840 --> 00:30:14,840
What a cool idea.

471
00:30:14,840 --> 00:30:16,840
We have to get some travel bugs.

472
00:30:16,840 --> 00:30:18,840
We have one, but we can get some more.

473
00:30:18,840 --> 00:30:21,840
Our travel bugs could see the world. How cool is that?

474
00:30:21,840 --> 00:30:23,840
Wait a minute. We're getting ahead of ourselves.

475
00:30:23,840 --> 00:30:26,840
I know working on our caches is part of the assignment,

476
00:30:26,840 --> 00:30:28,840
but we still haven't solved our problem.

477
00:30:28,840 --> 00:30:30,840
I was reading Tony's report on electricity,

478
00:30:30,840 --> 00:30:33,840
and he said we need to learn more about magnetism.

479
00:30:33,840 --> 00:30:36,840
I think Ula and Nina are meeting with Dr. D again.

480
00:30:36,840 --> 00:30:38,840
Hopefully we should get their report soon.

481
00:30:38,840 --> 00:30:40,840
For great ideas on creating reports,

482
00:30:40,840 --> 00:30:43,840
visit the Treehouse and the NASA Sci-Files website.

483
00:30:46,840 --> 00:30:49,840
I'm really looking forward to the Northern Lights Festival tonight,

484
00:30:49,840 --> 00:30:52,840
and hopefully seeing some auroras with the kids' club members.

485
00:30:52,840 --> 00:30:54,840
Ondinus is the perfect spot for viewing auroras

486
00:30:54,840 --> 00:30:57,840
because it is located directly under the auroral oval.

487
00:30:57,840 --> 00:31:00,840
Of course, Nina and Ula are also investigating magnetism

488
00:31:00,840 --> 00:31:02,840
for the Treehouse detectives.

489
00:31:02,840 --> 00:31:04,840
This is a good place to start.

490
00:31:04,840 --> 00:31:07,840
We know that magnets have a north pole and a south pole.

491
00:31:07,840 --> 00:31:09,840
And the two north poles repel,

492
00:31:09,840 --> 00:31:11,840
and the north and the south pole attract each other.

493
00:31:11,840 --> 00:31:13,840
Very good. Let's demonstrate that

494
00:31:13,840 --> 00:31:16,840
by having you push light poles of these two magnets together.

495
00:31:20,840 --> 00:31:22,840
Oy, they're really strong.

496
00:31:22,840 --> 00:31:26,840
Let's take a look at the magnetic field of this permanent bar magnet.

497
00:31:35,840 --> 00:31:37,840
That's impressive.

498
00:31:37,840 --> 00:31:40,840
Notice how the south pole, or white part of this compass needle,

499
00:31:40,840 --> 00:31:43,840
points to the north pole of the bar magnet.

500
00:31:43,840 --> 00:31:46,840
So if a compass always points to where the Earth's north pole,

501
00:31:46,840 --> 00:31:49,840
that must mean that the Earth is a big magnet with a magnetic pole up north.

502
00:31:49,840 --> 00:31:52,840
You're right. The Earth's magnetic field looks very similar

503
00:31:52,840 --> 00:31:54,840
to the field of this bar magnet.

504
00:31:54,840 --> 00:31:57,840
I heard that the Chinese used a lodestone to produce their first compass.

505
00:31:57,840 --> 00:31:59,840
Historians think so.

506
00:31:59,840 --> 00:32:02,840
Here is a piece of lodestone, a naturally magnetic rock.

507
00:32:02,840 --> 00:32:05,840
If I float it on this phone, it will point north.

508
00:32:05,840 --> 00:32:08,840
Doesn't magnetism have something to do with electricity?

509
00:32:08,840 --> 00:32:10,840
Yes, it does.

510
00:32:10,840 --> 00:32:12,840
Magnetic fields are produced by moving charges.

511
00:32:12,840 --> 00:32:15,840
Let's make an electromagnet by having an electric current

512
00:32:15,840 --> 00:32:18,840
go through this wire, which is wrapped around an iron bar.

513
00:32:21,840 --> 00:32:23,840
This field looks just like the bar magnets.

514
00:32:23,840 --> 00:32:26,840
Except, when I turn off the current of an electromagnet,

515
00:32:26,840 --> 00:32:29,840
the magnetic field disappears.

516
00:32:29,840 --> 00:32:33,840
So is the Earth like a giant electromagnet, or like a permanent magnet?

517
00:32:33,840 --> 00:32:38,840
Well, the Earth has an outer core made of molten iron that is constantly in motion.

518
00:32:38,840 --> 00:32:43,840
A process called the dynamo effect creates huge currents of electricity in the iron,

519
00:32:43,840 --> 00:32:46,840
which produces a giant electromagnet.

520
00:32:46,840 --> 00:32:51,840
In like manner, the Earth's magnetic field deflects the protons and electrons of the solar wind,

521
00:32:51,840 --> 00:32:55,840
which the Sun is throwing at the Earth at hundreds of kilometers per second.

522
00:32:55,840 --> 00:32:57,840
Ah, I get it.

523
00:32:57,840 --> 00:33:01,840
Didn't a Norwegian scientist named Christian Birkland investigate the solar winds and auroras?

524
00:33:01,840 --> 00:33:05,840
That's right. He used a magnetized sphere called a torella to represent the Earth.

525
00:33:05,840 --> 00:33:08,840
And he fired an electron beam at it to simulate the solar wind.

526
00:33:08,840 --> 00:33:10,840
What did he discover?

527
00:33:10,840 --> 00:33:14,840
Well, the electron beam did cause the gases in the chamber to glow like an aurora,

528
00:33:14,840 --> 00:33:18,840
and the magnetic field guided the electrons like beads in a string to the poles of the torella.

529
00:33:18,840 --> 00:33:21,840
And we know that auroras occur on Earth near its poles.

530
00:33:21,840 --> 00:33:26,840
Very good. Here is an example of how high-energy electrons can cause a gas to glow.

531
00:33:26,840 --> 00:33:30,840
This is a tube of helium gas hooked up to a high-voltage power supply.

532
00:33:31,840 --> 00:33:33,840
The tube is glowing pink.

533
00:33:33,840 --> 00:33:36,840
Each gas gives off its own special color.

534
00:33:36,840 --> 00:33:39,840
Here is neon gas, which looks orange.

535
00:33:39,840 --> 00:33:41,840
Just like the lights I've seen at restaurants.

536
00:33:41,840 --> 00:33:44,840
That's right. Auroras produce greens, blues, and reds

537
00:33:44,840 --> 00:33:50,840
when electrons collide with oxygen and nitrogen atoms hundreds of kilometers above the Earth's surface.

538
00:33:50,840 --> 00:33:52,840
Auroras certainly don't look that high.

539
00:33:52,840 --> 00:33:55,840
Dr. D., wasn't there a problem with Birkland's theory?

540
00:33:55,840 --> 00:34:00,840
Yes, he had the misconception that it was electrons coming directly from the Sun that caused the aurora.

541
00:34:00,840 --> 00:34:01,840
Well, where do they come from?

542
00:34:01,840 --> 00:34:03,840
They do come in part from the Sun.

543
00:34:03,840 --> 00:34:06,840
The solar wind compresses the magnetic field on the day side of the Earth

544
00:34:06,840 --> 00:34:10,840
and stretches it into a long tail called the magnetotail on the night side.

545
00:34:10,840 --> 00:34:15,840
Electrons from the solar wind flow around the day side and into the magnetosphere at the tail.

546
00:34:15,840 --> 00:34:16,840
Then what happens?

547
00:34:16,840 --> 00:34:20,840
The electrons in the magnetotail are then pulled back down toward the poles

548
00:34:20,840 --> 00:34:22,840
at increasingly high speeds by electric forces.

549
00:34:22,840 --> 00:34:24,840
These are called Birkland currents.

550
00:34:24,840 --> 00:34:29,840
And when they collide with the gases in the atmosphere near the poles, we have an aurora.

551
00:34:29,840 --> 00:34:34,840
Exactly. But to really understand auroras, you must first learn more about activity on the Sun,

552
00:34:34,840 --> 00:34:35,840
like sunspots and flares.

553
00:34:35,840 --> 00:34:39,840
Thanks, Dr. D. Let's get a report on magnetism ready for the Trias detectives.

554
00:34:39,840 --> 00:34:41,840
Maybe they can help us investigate the Sun.

555
00:34:47,840 --> 00:34:49,840
Okay, let's fire up the computer.

556
00:34:49,840 --> 00:34:53,840
I'm ready to talk magnetism with our friends at the Andenes Barn School in Norway.

557
00:34:53,840 --> 00:34:56,840
It's not every day we have a transatlantic experiment.

558
00:34:56,840 --> 00:34:59,840
I would love to visit Norway and see the culture close up.

559
00:34:59,840 --> 00:35:01,840
Well, how about the next best thing?

560
00:35:01,840 --> 00:35:04,840
We're ready to talk to the NASA Sci-Files Kids Club members in Andenes.

561
00:35:04,840 --> 00:35:05,840
Perfect.

562
00:35:05,840 --> 00:35:08,840
They should be ready just about now.

563
00:35:10,840 --> 00:35:14,840
Hi, I'm Jacob here with Bianca. We understand you're doing an experiment on magnetism.

564
00:35:14,840 --> 00:35:15,840
Hi, I'm Ingrid.

565
00:35:15,840 --> 00:35:16,840
And I'm Alexander.

566
00:35:16,840 --> 00:35:20,840
Hi. Dr. D. told us that you're working on an electromagnet experiment.

567
00:35:20,840 --> 00:35:22,840
Can you tell us about it?

568
00:35:22,840 --> 00:35:28,840
Sure. Our electromagnet is a wire wrapped around an iron nail attached to a battery.

569
00:35:28,840 --> 00:35:35,840
We wanted to find out how the strength of the electromagnet changes when we increase the voltage.

570
00:35:35,840 --> 00:35:38,840
And we increase the voltage by using more batteries.

571
00:35:38,840 --> 00:35:44,840
We learned in science class that a battery is like an electrical pump that pushes electrons through a circuit.

572
00:35:44,840 --> 00:35:46,840
The voltage measures the push.

573
00:35:46,840 --> 00:35:49,840
And the flow of electrons through the wire is called a current.

574
00:35:49,840 --> 00:35:50,840
We learned that too.

575
00:35:50,840 --> 00:35:55,840
We also learned that as the voltage is increased, the current in the wire will increase.

576
00:35:55,840 --> 00:36:03,840
So we hypothesized that if we increase the voltage and get more current, then the strength of the electromagnet will also increase.

577
00:36:03,840 --> 00:36:05,840
Sounds like excellent reasoning.

578
00:36:05,840 --> 00:36:09,840
We began by wrapping wire around the nail 300 times.

579
00:36:09,840 --> 00:36:13,840
Next we placed a 1.5 volt battery in the battery pack.

580
00:36:13,840 --> 00:36:17,840
We then connected one end of the wire to the positive battery terminal.

581
00:36:17,840 --> 00:36:23,840
And to complete the circuit, we connected the other end to the negative terminal.

582
00:36:23,840 --> 00:36:28,840
You won't get any current or flow of electrons unless you have a complete circuit.

583
00:36:28,840 --> 00:36:33,840
That's right. And a current in the wire then causes the nail to become a magnet.

584
00:36:33,840 --> 00:36:38,840
To test the strength of the magnet, we placed it in a cup of paperclips.

585
00:36:38,840 --> 00:36:42,840
I would think that the stronger the magnet, the more paperclips it would pick up.

586
00:36:42,840 --> 00:36:46,840
We agree. In our first trial, we picked up six paperclips.

587
00:36:46,840 --> 00:36:50,840
We know in an experiment it is important to do multiple trials and then find the average.

588
00:36:50,840 --> 00:36:52,840
What was your average?

589
00:36:52,840 --> 00:36:56,840
The class average was 8 paperclips with 1.5 volt battery.

590
00:36:56,840 --> 00:37:05,840
To continue to test our hypothesis, we added another 1.5 volt battery increasing the voltage to 3 volts.

591
00:37:05,840 --> 00:37:08,840
The average was 14 paperclips with 2 batteries.

592
00:37:08,840 --> 00:37:12,840
Wow! You doubled the voltage and almost doubled the number of paperclips.

593
00:37:12,840 --> 00:37:15,840
We continue by adding a third battery.

594
00:37:15,840 --> 00:37:19,840
With 4.5 volts, we averaged 21 paperclips.

595
00:37:19,840 --> 00:37:26,840
And 4 batteries, or 6 volts, picked up an average of 30 paperclips.

596
00:37:26,840 --> 00:37:29,840
Congratulations! It looks like you proved your hypothesis.

597
00:37:29,840 --> 00:37:33,840
That's right. We graphed the results as well.

598
00:37:33,840 --> 00:37:39,840
A graph clearly shows that the strength of the magnet increases as the voltage increases.

599
00:37:39,840 --> 00:37:45,840
Our teacher, Ole, also told us that the Earth's magnetic field is very similar to our electromagnet,

600
00:37:46,840 --> 00:37:50,840
except the current in the Earth is a billion times the current in our circuit.

601
00:37:50,840 --> 00:37:52,840
That's incredible!

602
00:37:52,840 --> 00:37:56,840
I was wondering, does the number of times you wrap the wire around the nail make a difference?

603
00:37:56,840 --> 00:38:00,840
We think so, but that is what we are going to test next.

604
00:38:00,840 --> 00:38:02,840
Great! Be sure to send us your results.

605
00:38:02,840 --> 00:38:07,840
We will. Goodbye, from Andenes Børneskole, Norway.

606
00:38:07,840 --> 00:38:10,840
Andenes!

607
00:38:10,840 --> 00:38:12,840
I can't believe all the cool experiments we've seen.

608
00:38:12,840 --> 00:38:17,840
Anthony, Dr. Bagnall, Dr. Dean, the Kids Club members, and now the Kids Club in Norway.

609
00:38:17,840 --> 00:38:22,840
Clearly there is a connection between electricity and magnetism, but I'm not sure how.

610
00:38:22,840 --> 00:38:25,840
I'm still sorting through Ulla and Nina's report on auroras.

611
00:38:25,840 --> 00:38:30,840
Dr. D also said that before we can fully understand auroras, we need to learn more about the Sun.

612
00:38:30,840 --> 00:38:34,840
I completely forgot about the Sun. How are we going to learn more about the Sun?

613
00:38:34,840 --> 00:38:39,840
Don't worry. I've done some research on the Internet, and NASA does lots of research on the Sun.

614
00:38:39,840 --> 00:38:41,840
Of course! The answer is NASA. Let's go!

615
00:38:41,840 --> 00:38:49,840
Slow down. Ulla and Nina also reported a teleconference that they had with North Shore Christian Academy in Everett, Washington.

616
00:38:49,840 --> 00:38:52,840
Oh, I see. I think.

617
00:38:52,840 --> 00:38:57,840
Before learning about the Sun, they talked with the students at North Shore about the layers of the Earth's atmosphere.

618
00:38:57,840 --> 00:39:00,840
The layers of the Earth's atmosphere?

619
00:39:00,840 --> 00:39:07,840
You know, the troposphere, closest to the Earth, and the mesosphere, which is very cold and the air is very thin.

620
00:39:07,840 --> 00:39:11,840
And, of course, the thermosphere and ionosphere, where most of the auroras occur.

621
00:39:11,840 --> 00:39:13,840
Jacob, I'm impressed.

622
00:39:13,840 --> 00:39:18,840
I've been doing more than surfing the Web and reading reports. Every once in a while, you have to go old school and use books.

623
00:39:18,840 --> 00:39:21,840
Well, I'm glad you haven't forgotten such a great resource.

624
00:39:21,840 --> 00:39:23,840
But we still need to learn more about the Sun.

625
00:39:23,840 --> 00:39:28,840
Well, we're in luck. Catherine and Argie are meeting with Dr. Nikki Fox to learn more about the Sun.

626
00:39:28,840 --> 00:39:35,840
She's at the Johns Hopkins Applied Physics Laboratory and works with scientists at NASA Goddard Space Flight Center.

627
00:39:35,840 --> 00:39:39,840
I'm sure they'll find the Sun very illuminating.

628
00:39:39,840 --> 00:39:42,840
Very funny. But I can't wait to read their report.

629
00:39:42,840 --> 00:39:47,840
Well, most of what we know about the Sun comes from measurements from various instruments and satellites.

630
00:39:47,840 --> 00:39:52,840
And they observe things such as the Sun's size, mass, surface temperature, and brightness.

631
00:39:52,840 --> 00:39:56,840
Various instruments and satellites? What kinds of satellites?

632
00:39:56,840 --> 00:40:00,840
Well, there's SOHO, which is designed to study the internal structure of the Sun,

633
00:40:00,840 --> 00:40:03,840
and ACE that studies the solar wind that comes from the Sun.

634
00:40:03,840 --> 00:40:06,840
And then there's also POLAR, TIMED, and POSE,

635
00:40:06,840 --> 00:40:11,840
that monitor how this solar wind interacts with the Earth's magnetosphere and causes auroras.

636
00:40:11,840 --> 00:40:14,840
And, of course, we're all looking forward to the launch of STEREO,

637
00:40:14,840 --> 00:40:16,840
which is being built here at the Applied Physics Lab.

638
00:40:16,840 --> 00:40:20,840
And it will get the first three-dimensional images of the Sun.

639
00:40:20,840 --> 00:40:22,840
So that's how you know so much about the Sun.

640
00:40:22,840 --> 00:40:25,840
Well, satellites are very helpful, but there's still much more to learn.

641
00:40:25,840 --> 00:40:28,840
Let's start with the basics. The Sun is an average star.

642
00:40:28,840 --> 00:40:31,840
It's not the brightest star, and it's not the hottest star.

643
00:40:31,840 --> 00:40:34,840
In fact, scientists actually classify it as a dwarf.

644
00:40:34,840 --> 00:40:37,840
A dwarf? I thought it was really big.

645
00:40:37,840 --> 00:40:39,840
Well, remember that size is relative.

646
00:40:39,840 --> 00:40:41,840
Compared to the Earth, the Sun is huge.

647
00:40:41,840 --> 00:40:45,840
The diameter of the Sun is about 110 Earths strung together.

648
00:40:45,840 --> 00:40:49,840
If you think of the Sun as a basketball, Earth would be a tiny BB.

649
00:40:49,840 --> 00:40:52,840
But there are stars that are much bigger.

650
00:40:52,840 --> 00:40:54,840
Then why don't the other stars look bigger than the Sun?

651
00:40:54,840 --> 00:40:57,840
Well, that's because they're so much farther away.

652
00:40:57,840 --> 00:41:00,840
The Sun is 158 million kilometers away from the Earth.

653
00:41:00,840 --> 00:41:04,840
However, the next closest star is Proxima Centauri,

654
00:41:04,840 --> 00:41:08,840
and it's so far away that its distance has to be measured in light-years.

655
00:41:11,840 --> 00:41:13,840
Wow, that's far.

656
00:41:15,840 --> 00:41:17,840
And fast.

657
00:41:17,840 --> 00:41:19,840
What is the Sun made of?

658
00:41:19,840 --> 00:41:23,840
It's mostly made from hydrogen, with some helium and a few other elements.

659
00:41:23,840 --> 00:41:25,840
It also has six layers.

660
00:41:25,840 --> 00:41:29,840
The Earth has layers. Are the Sun's layers like the Earth's?

661
00:41:29,840 --> 00:41:30,840
No.

662
00:41:30,840 --> 00:41:33,840
Because the Sun is not solid like our Earth, they're quite different.

663
00:41:33,840 --> 00:41:38,840
The Sun's layers consist of a core, a radiative zone, a convective zone,

664
00:41:38,840 --> 00:41:42,840
and then there's the visible surface known as the photosphere, the chromosphere,

665
00:41:42,840 --> 00:41:45,840
and finally the outermost layer, the corona.

666
00:41:45,840 --> 00:41:48,840
So if the Sun is not a solid, then is it gaseous?

667
00:41:48,840 --> 00:41:51,840
No, it's neither. It's actually a plasma.

668
00:41:51,840 --> 00:41:55,840
Of course. I was just reading about plasma being the fourth state of matter.

669
00:41:55,840 --> 00:41:56,840
That's correct.

670
00:41:56,840 --> 00:41:59,840
Because this plasma is hotter in some places than others,

671
00:41:59,840 --> 00:42:02,840
it creates convection cells in the convection zone of the Sun.

672
00:42:02,840 --> 00:42:03,840
What are convection cells?

673
00:42:03,840 --> 00:42:07,840
Well, they look just like rice grains, and scientists call this granulation.

674
00:42:07,840 --> 00:42:11,840
The bright center of each cell is hot, rising material,

675
00:42:11,840 --> 00:42:16,840
and the darker edges are cooler gas falling to be reheated, just like water boiling.

676
00:42:16,840 --> 00:42:19,840
These granules are continuously evolving and changing.

677
00:42:19,840 --> 00:42:23,840
But these light and dark patches should not be confused with sunspots,

678
00:42:23,840 --> 00:42:26,840
which are dark spots higher up on the surface of the Sun.

679
00:42:26,840 --> 00:42:30,840
I've seen pictures of sunspots before. Are they very big?

680
00:42:30,840 --> 00:42:33,840
Well, the average size of a sunspot is about the size of the Earth.

681
00:42:33,840 --> 00:42:35,840
I'd say that's pretty big.

682
00:42:35,840 --> 00:42:37,840
What causes sunspots?

683
00:42:37,840 --> 00:42:40,840
Well, just like the Earth, the Sun has poles and a magnetic field,

684
00:42:40,840 --> 00:42:45,840
and sunspots are created when this magnetic field interacts with hot plasma at the Sun's surface.

685
00:42:45,840 --> 00:42:49,840
The Sun has poles and a magnetic field? Cool.

686
00:42:49,840 --> 00:42:51,840
Well, not really cool.

687
00:42:51,840 --> 00:42:56,840
Sometimes this magnetic field causes the plasma in a sunspot to burst from the surface of the Sun

688
00:42:56,840 --> 00:42:58,840
in what's known as a solar flare.

689
00:42:58,840 --> 00:43:00,840
Do solar flares affect the Earth?

690
00:43:00,840 --> 00:43:01,840
Or satellites?

691
00:43:01,840 --> 00:43:04,840
Well, solar flares do release a tremendous amount of energy,

692
00:43:04,840 --> 00:43:08,840
and that can affect the Earth and our satellites in lots of different ways.

693
00:43:08,840 --> 00:43:11,840
It sounds like we need to learn more about solar flares.

694
00:43:11,840 --> 00:43:13,840
Thanks, Dr. Fox.

695
00:43:13,840 --> 00:43:18,840
So what's up? Could solar flares be responsible for the problem with the GPS?

696
00:43:18,840 --> 00:43:22,840
How do the treehouse detectives figure out what happened to their GPS devices?

697
00:43:22,840 --> 00:43:26,840
Find out in the conclusion of The Case of the Technical Knockout.

698
00:43:26,840 --> 00:43:30,840
Be sure to look for the answers to the following questions.

699
00:43:30,840 --> 00:43:34,840
In which layer of the atmosphere is the ionosphere?

700
00:43:34,840 --> 00:43:37,840
What is a coronal mass ejection?

701
00:43:37,840 --> 00:43:39,840
What is space weather?

702
00:43:39,840 --> 00:43:41,840
Explain a solar cycle.

703
00:43:41,840 --> 00:43:44,840
When you see this icon, the answer is near.

704
00:43:48,840 --> 00:44:04,840
I'm still not sure about this.

705
00:44:04,840 --> 00:44:06,840
Come on, it's easy.

706
00:44:06,840 --> 00:44:09,840
We find a good hiding spot, note the location using our GPS,

707
00:44:09,840 --> 00:44:12,840
put the location on the Internet, and our assignment is complete.

708
00:44:12,840 --> 00:44:14,840
I already anticipate a good grade.

709
00:44:14,840 --> 00:44:17,840
I'm not talking about the assignment. I'm talking about our problem.

710
00:44:17,840 --> 00:44:19,840
I've got a new hypothesis.

711
00:44:19,840 --> 00:44:22,840
A solar flare occurred during our first attempt at geocaching.

712
00:44:22,840 --> 00:44:25,840
Now there is no solar flare, so we aren't getting any technical interference.

713
00:44:25,840 --> 00:44:28,840
Well, I agree we aren't receiving any interference,

714
00:44:28,840 --> 00:44:30,840
but we still need to confirm our hypothesis.

715
00:44:30,840 --> 00:44:31,840
No problem.

716
00:44:31,840 --> 00:44:33,840
What do you mean, no problem?

717
00:44:33,840 --> 00:44:36,840
Geo Eagle One to home base, come in please.

718
00:44:36,840 --> 00:44:38,840
Hi, Jacob. We're all set.

719
00:44:38,840 --> 00:44:40,840
We should have the results in a few minutes.

720
00:44:40,840 --> 00:44:42,840
Jacob, what's going on?

721
00:44:42,840 --> 00:44:46,840
I knew you wouldn't just accept my hypothesis, so I did some more research.

722
00:44:46,840 --> 00:44:50,840
I set up an interview between R.J. Cayley and Dr. Sten Odenwald,

723
00:44:50,840 --> 00:44:52,840
a NASA researcher who's also over in Norway.

724
00:44:52,840 --> 00:44:54,840
Jacob, you're making real progress.

725
00:44:54,840 --> 00:44:57,840
You recognize the problem, conducted solid research,

726
00:44:57,840 --> 00:45:00,840
and you're working to verify your hypothesis. I'm impressed.

727
00:45:00,840 --> 00:45:04,840
If you think that's impressive, wait until you hear from Dr. Odenwald.

728
00:45:04,840 --> 00:45:09,840
Home base, let me know the minute you finish talking to Dr. Odenwald.

729
00:45:09,840 --> 00:45:11,840
Home base?

730
00:45:11,840 --> 00:45:13,840
Home base?

731
00:45:17,840 --> 00:45:20,840
Jacob, come in. We're getting ready to talk to Dr. Odenwald.

732
00:45:20,840 --> 00:45:23,840
Do you have any additional questions? Over.

733
00:45:23,840 --> 00:45:25,840
Over.

734
00:45:26,840 --> 00:45:29,840
Well, that's funny. It was working just fine a second ago.

735
00:45:29,840 --> 00:45:31,840
Yeah, it's really strange.

736
00:45:31,840 --> 00:45:35,840
Maybe there's been another solar flare that's affected the radio and the GPS.

737
00:45:35,840 --> 00:45:38,840
Poor Jacob and Bianca.

738
00:45:39,840 --> 00:45:41,840
Oh, look. Here he is now.

739
00:45:41,840 --> 00:45:42,840
Hi, Dr. Odenwald.

740
00:45:42,840 --> 00:45:46,840
Hi, kids. Jacob's been telling me about his hypothesis and the research you've been doing.

741
00:45:46,840 --> 00:45:48,840
Sounds very interesting.

742
00:45:48,840 --> 00:45:49,840
Yes, it is.

743
00:45:49,840 --> 00:45:53,840
Of course, it'll be even more exciting if the hypothesis is correct.

744
00:45:53,840 --> 00:45:55,840
Right. We were hoping you could help us.

745
00:45:55,840 --> 00:46:00,840
Jacob believes that a solar flare is responsible for the technical glitch with our GPS,

746
00:46:00,840 --> 00:46:01,840
but we're not sure how.

747
00:46:01,840 --> 00:46:04,840
Well, solar flares are one possibility, of course.

748
00:46:04,840 --> 00:46:08,840
When we're talking about the sun and solar flares, we're talking about a huge amount of energy.

749
00:46:08,840 --> 00:46:11,840
And that energy caused our GPS to malfunction?

750
00:46:11,840 --> 00:46:14,840
It could have. Let's start at the beginning.

751
00:46:14,840 --> 00:46:19,840
Solar flares happen near the surface of the sun because the magnetic fields there that are all tangled up

752
00:46:19,840 --> 00:46:24,840
try to get untangled into simpler shapes, and that releases a huge amount of energy.

753
00:46:24,840 --> 00:46:27,840
Sometimes it can heat the surface all the way up to 100 million degrees.

754
00:46:27,840 --> 00:46:29,840
That's incredibly hot.

755
00:46:29,840 --> 00:46:30,840
It really is.

756
00:46:30,840 --> 00:46:34,840
The gases near the flare are so hot that they produce X-ray light,

757
00:46:34,840 --> 00:46:39,840
and this light travels to the Earth in about eight and a half minutes and impacts the Earth's atmosphere.

758
00:46:39,840 --> 00:46:41,840
Wow, that's quick.

759
00:46:41,840 --> 00:46:45,840
And when the X-rays arrive, they disrupt the ionosphere on the daytime side of the Earth.

760
00:46:45,840 --> 00:46:48,840
We learned that the ionosphere is part of the thermosphere,

761
00:46:48,840 --> 00:46:51,840
where there are a lot of charged particles and free electrons.

762
00:46:51,840 --> 00:46:56,840
That's right, and these disruptions can cause shortwave radio blackouts that last for hours.

763
00:46:56,840 --> 00:47:00,840
We also learned that GPS communicates using radio waves.

764
00:47:00,840 --> 00:47:04,840
And because solar flares affect radio waves, Jacob's hypothesis is right.

765
00:47:04,840 --> 00:47:07,840
Well, again, solar flares are only one possibility.

766
00:47:07,840 --> 00:47:10,840
You could also have coronal mass ejections and superflares.

767
00:47:10,840 --> 00:47:12,840
What are coronal mass ejections?

768
00:47:12,840 --> 00:47:15,840
Well, during some of the largest solar flares,

769
00:47:15,840 --> 00:47:22,840
the same magnetic changes that produce the flare can actually launch a billion-ton cloud of charged particles into space.

770
00:47:22,840 --> 00:47:25,840
These are called coronal mass ejections, or CMEs.

771
00:47:25,840 --> 00:47:27,840
Do these clouds affect radio waves?

772
00:47:27,840 --> 00:47:29,840
Oh, yes, they can.

773
00:47:29,840 --> 00:47:32,840
They also produce some of the most intense and widespread aurora.

774
00:47:32,840 --> 00:47:37,840
The thing is that they travel to the Earth much slower than the X-rays do from typical solar flares.

775
00:47:37,840 --> 00:47:41,840
It usually takes about one to four days for a CME to arrive at the Earth.

776
00:47:41,840 --> 00:47:43,840
What is a superflare?

777
00:47:43,840 --> 00:47:46,840
Well, fortunately for us, superflares are not very common.

778
00:47:46,840 --> 00:47:49,840
When they happen, though, they produce an amazing amount of energy.

779
00:47:49,840 --> 00:47:51,840
How would a superflare affect the Earth?

780
00:47:51,840 --> 00:47:56,840
Well, if you're an astronaut in space, a superflare could produce a life-threatening dose of radiation.

781
00:47:56,840 --> 00:48:04,840
Historical record also shows that some of the most powerful flares we've seen so far can produce satellite damage or loss of function.

782
00:48:04,840 --> 00:48:07,840
Then our GPS really wouldn't work.

783
00:48:07,840 --> 00:48:08,840
Well, that's right.

784
00:48:08,840 --> 00:48:14,840
Even the CME from a modest superflare like the one in 1989 caused a blackout in Quebec.

785
00:48:14,840 --> 00:48:16,840
Wow, radiation, power shortages.

786
00:48:16,840 --> 00:48:18,840
These superflares sound extreme.

787
00:48:18,840 --> 00:48:23,840
It's easy to see how something that's strong as a superflare would have an effect on our GPS.

788
00:48:23,840 --> 00:48:25,840
But what effect would an average solar flare have?

789
00:48:25,840 --> 00:48:31,840
Well, space weather includes all solar flares, CMEs, and superflares can disturb the ionosphere.

790
00:48:31,840 --> 00:48:37,840
These disturbances slow down the speed of the radio signals sent to the Earth from the GPS satellite.

791
00:48:37,840 --> 00:48:39,840
And the speed can vary from minute to minute.

792
00:48:39,840 --> 00:48:46,840
And if the signal takes longer to get to Earth, then our GPS receiver will think that the satellite is further away and get the wrong position.

793
00:48:46,840 --> 00:48:51,840
Because the speed changes from minute to minute, the GPS location varies as well.

794
00:48:51,840 --> 00:48:53,840
That's exactly what happened to us.

795
00:48:53,840 --> 00:48:56,840
What we need is some way to predict space weather.

796
00:48:56,840 --> 00:48:58,840
And then we would know the best time to geocache.

797
00:48:58,840 --> 00:49:02,840
And we'd be able to better protect and prepare our astronauts in space.

798
00:49:02,840 --> 00:49:03,840
Well, that's right.

799
00:49:03,840 --> 00:49:08,840
NASA has been working for years to understand the complex relationship between the Earth and the sun

800
00:49:08,840 --> 00:49:12,840
using sophisticated satellite systems such as ACE and SOHO.

801
00:49:12,840 --> 00:49:18,840
We also work with the image and time satellite systems and sounding rockets launched here in Norway

802
00:49:18,840 --> 00:49:21,840
to study auroras and how electrons and auroral particles flow.

803
00:49:22,840 --> 00:49:24,840
So NASA is at work all around the world.

804
00:49:24,840 --> 00:49:25,840
That's right.

805
00:49:25,840 --> 00:49:29,840
And we work with communities of scientists and researchers all around the world

806
00:49:29,840 --> 00:49:32,840
to try to understand how space weather affects the Earth.

807
00:49:32,840 --> 00:49:33,840
Thanks, Dr. Unwall.

808
00:49:33,840 --> 00:49:36,840
You may have actually helped support Jacob's hypothesis.

809
00:49:36,840 --> 00:49:38,840
And solved our problem with our walkie-talkies.

810
00:49:38,840 --> 00:49:40,840
Did you say walkie-talkies?

811
00:49:40,840 --> 00:49:41,840
Yes.

812
00:49:41,840 --> 00:49:44,840
We lost our radio signal with Jacob just before we called you.

813
00:49:44,840 --> 00:49:49,840
There must have been another solar flare that affected both the walkie-talkies and the GPS

814
00:49:49,840 --> 00:49:51,840
because they both use radio waves.

815
00:49:51,840 --> 00:49:56,840
Yeah, but walkie-talkies don't usually use radio waves to travel up to the ionosphere and then back down.

816
00:49:56,840 --> 00:49:58,840
They usually use what's called a ground wave,

817
00:49:58,840 --> 00:50:02,840
which is basically line of sight between the receiver and the transmitter.

818
00:50:02,840 --> 00:50:03,840
Oh, no.

819
00:50:03,840 --> 00:50:05,840
Our hypothesis is incorrect.

820
00:50:05,840 --> 00:50:06,840
What do we do now?

821
00:50:06,840 --> 00:50:07,840
Well, don't panic.

822
00:50:07,840 --> 00:50:10,840
You did use careful reasoning after all.

823
00:50:10,840 --> 00:50:13,840
And your basic hypothesis about the GPS problem could still be correct.

824
00:50:13,840 --> 00:50:15,840
You just have to do more research.

825
00:50:15,840 --> 00:50:20,840
Perhaps there's a way for us to find out if we had any solar activity on the first day of our problem and today.

826
00:50:20,840 --> 00:50:22,840
Ah, I think you're onto something.

827
00:50:22,840 --> 00:50:25,840
I've got a friend at NOAA who might be able to help.

828
00:50:25,840 --> 00:50:26,840
I'll give you his email address.

829
00:50:26,840 --> 00:50:28,840
But what about our walkie-talkie problem?

830
00:50:28,840 --> 00:50:32,840
Well, walkie-talkies might require a completely separate hypothesis.

831
00:50:32,840 --> 00:50:37,840
Think about a common problem that affects small electronic devices when they're in the field.

832
00:50:37,840 --> 00:50:38,840
What would that be?

833
00:50:38,840 --> 00:50:40,840
How about bad batteries?

834
00:50:40,840 --> 00:50:41,840
Take care, kids.

835
00:50:41,840 --> 00:50:42,840
Good luck.

836
00:50:43,840 --> 00:50:44,840
Bye.

837
00:50:53,840 --> 00:50:55,840
I'm not telling Jacob about this one.

838
00:50:59,840 --> 00:51:01,840
Thanks, RJ, and good work.

839
00:51:01,840 --> 00:51:04,840
I thought I lost you for a few minutes, but I understand when nature calls.

840
00:51:04,840 --> 00:51:05,840
Over.

841
00:51:06,840 --> 00:51:07,840
Well, I got lucky.

842
00:51:07,840 --> 00:51:09,840
My hypothesis is correct after all.

843
00:51:09,840 --> 00:51:11,840
I think it was more than just luck.

844
00:51:11,840 --> 00:51:12,840
You did good research.

845
00:51:12,840 --> 00:51:13,840
We all did good research.

846
00:51:13,840 --> 00:51:17,840
Now all we need to do is plan our geocache and complete our assignment.

847
00:51:17,840 --> 00:51:19,840
Let's not congratulate ourselves just yet.

848
00:51:19,840 --> 00:51:22,840
RJ said that NOAA might be able to confirm our hypothesis.

849
00:51:22,840 --> 00:51:23,840
Further.

850
00:51:23,840 --> 00:51:24,840
That's true.

851
00:51:24,840 --> 00:51:26,840
You don't always know for certain that you're 100% correct.

852
00:51:26,840 --> 00:51:29,840
Right, but hopefully they'll be able to help us get closer to the answer.

853
00:51:29,840 --> 00:51:32,840
Let's plan our cache and wait for Tony's report from NOAA.

854
00:51:32,840 --> 00:51:34,840
I'm ready for coordinates.

855
00:51:34,840 --> 00:51:36,840
North 37.

856
00:51:43,840 --> 00:51:46,840
I'm meeting with Mr. Joe Cunches who works with NOAA

857
00:51:46,840 --> 00:51:49,840
and the Space Environment Center here in Boulder, Colorado.

858
00:51:49,840 --> 00:51:51,840
He studies space weather and how to predict it.

859
00:51:51,840 --> 00:51:54,840
Hopefully he can tell us whether there was any solar activity

860
00:51:54,840 --> 00:51:57,840
the day we experienced the problem with our GPS.

861
00:51:57,840 --> 00:52:01,840
Space weather refers to conditions near the Earth that affect man-made technologies

862
00:52:01,840 --> 00:52:04,840
such as satellites and other human activities.

863
00:52:04,840 --> 00:52:06,840
That's why it's so important to predict space weather.

864
00:52:06,840 --> 00:52:07,840
Right.

865
00:52:07,840 --> 00:52:10,840
Satellites were once rare and mostly government-owned,

866
00:52:10,840 --> 00:52:13,840
but today they are more numerous and many are commercially owned,

867
00:52:13,840 --> 00:52:17,840
so that's why it's important to know where and when they may be affected.

868
00:52:17,840 --> 00:52:18,840
Right.

869
00:52:18,840 --> 00:52:20,840
Satellites are very important in our lives

870
00:52:20,840 --> 00:52:23,840
and also a nice addition to a well-balanced portfolio.

871
00:52:23,840 --> 00:52:26,840
We heavily depend on satellites for weather information,

872
00:52:26,840 --> 00:52:29,840
television, communication, and navigation.

873
00:52:29,840 --> 00:52:31,840
We have learned about predicting weather here on Earth,

874
00:52:31,840 --> 00:52:33,840
but how do you predict space weather?

875
00:52:33,840 --> 00:52:38,840
Predictions are made primarily using data from satellites that monitor the sun.

876
00:52:39,840 --> 00:52:43,840
For example, NOAA's GOES and POSE satellites

877
00:52:43,840 --> 00:52:48,840
help forecasters know atmospheric conditions at low Earth orbits and higher up.

878
00:52:48,840 --> 00:52:50,840
Do you work with NASA satellites as well?

879
00:52:50,840 --> 00:52:51,840
Yes.

880
00:52:51,840 --> 00:52:54,840
NASA's ACE satellite samples the solar wind,

881
00:52:54,840 --> 00:53:00,840
and SOHO allows forecasters to see the solar eruptions that cause space weather.

882
00:53:00,840 --> 00:53:02,840
Are there other ways to monitor space weather?

883
00:53:02,840 --> 00:53:03,840
Yes.

884
00:53:03,840 --> 00:53:05,840
We use data from the ground-based observatories

885
00:53:06,840 --> 00:53:08,840
run by the United States Air Force

886
00:53:08,840 --> 00:53:13,840
as well as the magnetometer network run by the United States Geological Survey.

887
00:53:13,840 --> 00:53:15,840
What is a magnetometer?

888
00:53:15,840 --> 00:53:19,840
A magnetometer is an instrument that measures the behavior of the Earth's magnetic field

889
00:53:19,840 --> 00:53:23,840
and tells forecasters when a magnetic storm is developing.

890
00:53:23,840 --> 00:53:25,840
Wow, you have a lot of data to monitor.

891
00:53:25,840 --> 00:53:26,840
How do you get it all?

892
00:53:26,840 --> 00:53:31,840
We get data through the Internet, dedicated telephone lines, and email.

893
00:53:31,840 --> 00:53:34,840
We also have our own antennas that receive data.

894
00:53:34,840 --> 00:53:36,840
And once you have the data, you have to analyze it.

895
00:53:36,840 --> 00:53:42,840
Forecasters continually monitor the space environment to provide short-term, three-day predictions.

896
00:53:42,840 --> 00:53:47,840
They don't have daily space weather predictions on the news, so who receives your forecasts?

897
00:53:47,840 --> 00:53:51,840
The alerts go to a number of places, such as private and commercial users,

898
00:53:51,840 --> 00:53:54,840
as well as other government agencies such as NASA.

899
00:53:54,840 --> 00:53:56,840
Do you send out alerts often?

900
00:53:56,840 --> 00:53:59,840
It varies depending on the time of the solar cycle,

901
00:53:59,840 --> 00:54:03,840
but usually we average 20 to 30 alerts per week.

902
00:54:03,840 --> 00:54:04,840
What's a solar cycle?

903
00:54:04,840 --> 00:54:08,840
As you know, the Earth's weather changes over time with different seasons.

904
00:54:08,840 --> 00:54:10,840
The sun's weather does, too.

905
00:54:10,840 --> 00:54:15,840
The changes on the sun are caused by the reversal of its magnetic poles.

906
00:54:15,840 --> 00:54:17,840
I didn't realize that the poles of the sun switched.

907
00:54:17,840 --> 00:54:22,840
Over an 11-year period, the reversal of the sun's poles completes half of its cycle.

908
00:54:22,840 --> 00:54:26,840
During this time, the number of sunspots seen on the surface of the sun

909
00:54:26,840 --> 00:54:29,840
goes from high to low and then back again.

910
00:54:29,840 --> 00:54:30,840
Sounds intense.

911
00:54:30,840 --> 00:54:36,840
Yes. The period with lots of sunspots is intense and is called sunspot maximum.

912
00:54:36,840 --> 00:54:39,840
The period with fewer sunspots is called sunspot minimum.

913
00:54:39,840 --> 00:54:45,840
So during a sunspot maximum, there would be more solar flares and coronal mass ejections.

914
00:54:45,840 --> 00:54:49,840
We would see increased auroras and more disturbances in the ionosphere,

915
00:54:49,840 --> 00:54:51,840
causing problems with the satellite systems.

916
00:54:51,840 --> 00:54:53,840
Good job. I think you have it.

917
00:54:53,840 --> 00:54:58,840
But remember that even during a sunspot minimum, there can still be lots of interference.

918
00:54:58,840 --> 00:55:00,840
If you don't mind, I have one last question.

919
00:55:00,840 --> 00:55:01,840
Sure. What's your question?

920
00:55:01,840 --> 00:55:04,840
We're fairly certain that our GPS devices went crazy

921
00:55:04,840 --> 00:55:09,840
while we were geocaching due to a solar flare or space weather event that affected the ionosphere.

922
00:55:09,840 --> 00:55:11,840
Is there any way we can be sure that was the cause?

923
00:55:11,840 --> 00:55:15,840
We can find out if an alert was issued for that date,

924
00:55:15,840 --> 00:55:18,840
but not if the storm affected your GPS device.

925
00:55:18,840 --> 00:55:19,840
That makes sense.

926
00:55:19,840 --> 00:55:22,840
Let's go over to the computer and check out the website.

927
00:55:23,840 --> 00:55:27,840
You can find out all about space weather and geomagnetic storms

928
00:55:27,840 --> 00:55:30,840
when you visit NOAA's Space Environment Center website.

929
00:55:32,840 --> 00:55:35,840
NOAA confirmed that there was an alert while we were geocaching.

930
00:55:35,840 --> 00:55:38,840
We can't be certain, but we may have solved another mystery.

931
00:55:38,840 --> 00:55:41,840
Of course, I'm sending my report to the Trios detectives.

932
00:55:41,840 --> 00:55:45,840
Hopefully, they will get it before they go to pick up Dr. D from the airport.

933
00:55:46,840 --> 00:55:48,840
Look, it's Dr. D.

934
00:55:51,840 --> 00:55:53,840
Hi, Dr. D. We solved our mystery.

935
00:55:53,840 --> 00:55:56,840
That's great. Did it have anything to do with batteries?

936
00:55:56,840 --> 00:55:59,840
That's funny. Dr. Udenwald mentioned the same thing.

937
00:55:59,840 --> 00:56:02,840
We did have a small battery problem, but not with our GPS.

938
00:56:02,840 --> 00:56:06,840
Batteries aren't the problem. Remembering to check them can be.

939
00:56:06,840 --> 00:56:10,840
Right. To solve our GPS problem, we actually researched electricity,

940
00:56:10,840 --> 00:56:13,840
To solve our GPS problem, we actually researched electricity,

941
00:56:13,840 --> 00:56:16,840
magnetism, space weather, and auroras.

942
00:56:16,840 --> 00:56:18,840
We've learned all about how GPSs work.

943
00:56:18,840 --> 00:56:22,840
It's amazing how many new things we can learn while we're trying to find the solution to our problem.

944
00:56:22,840 --> 00:56:26,840
I was thinking about your problem as I was watching the auroras in Norway.

945
00:56:26,840 --> 00:56:30,840
It appears to me that the same space weather events that influenced the auroras

946
00:56:30,840 --> 00:56:32,840
probably also affected your GPS.

947
00:56:32,840 --> 00:56:36,840
Dr. D, why didn't you tell us earlier? We came to the same conclusion.

948
00:56:36,840 --> 00:56:38,840
Isn't it more fun to find the solution yourself?

949
00:56:38,840 --> 00:56:41,840
You're right. Antoni's report from Colorado finally nailed it down.

950
00:56:41,840 --> 00:56:45,840
Dr. Udenwald told us that storms on the sun can affect the ionosphere

951
00:56:45,840 --> 00:56:50,840
in ways that slow down the GPS signal so that the receiver reads the false distance.

952
00:56:50,840 --> 00:56:55,840
Antoni told us that there had been a space weather advisory the day that we had the problems.

953
00:56:55,840 --> 00:56:59,840
But don't worry, Dr. D. We know that that doesn't necessarily mean the storm caused the problem.

954
00:56:59,840 --> 00:57:02,840
But it is a very possible solution.

955
00:57:02,840 --> 00:57:05,840
Did you consider a multi-path signal error?

956
00:57:05,840 --> 00:57:06,840
What's that?

957
00:57:06,840 --> 00:57:12,840
What's an inaccuracy caused when the GPS signals bounce off of buildings or large rock surfaces?

958
00:57:12,840 --> 00:57:17,840
Well, we weren't around any buildings and I don't remember seeing any large rocks.

959
00:57:17,840 --> 00:57:22,840
I don't mean to alarm you. I really think your explanation is probably the best in this situation.

960
00:57:22,840 --> 00:57:24,840
I'm just trying to keep you on your toes.

961
00:57:24,840 --> 00:57:29,840
Thanks, Dr. D. Can you tell us about the auroras that you saw? What colors were they?

962
00:57:29,840 --> 00:57:31,840
Did they really dance around in the sky?

963
00:57:31,840 --> 00:57:34,840
Yes, they did. Let's take one question at a time.

964
00:57:34,840 --> 00:57:39,840
The auroras were absolutely wonderful. Mostly kind of a pale green, a little red on the borders.

965
00:58:34,840 --> 00:58:39,840
NASA Jet Propulsion Laboratory, California Institute of Technology