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Radio Waves and Electricity

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Subido el 28 de mayo de 2007 por EducaMadrid

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Fifth segment of NASA Sci Files The Case of the Technical Knockout explaining how an observatory studies the atmosphere and the different types of waves. This segment describes the electromagnetic spectrum and how GPS uses microwaves to communicate. It also shows how electricity can be used to create a magnetic field.

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We're about 25 meters from where we were, and when we last experienced some problems 00:00:00
with the GPS. 00:00:22
Over. 00:00:23
Can you still hear me? 00:00:24
The radio's coming in loud and clear too. 00:00:25
Keep us posted. 00:00:27
We shouldn't really assume whether or not the technical problem was permanent. 00:00:28
My guess is that one of the satellites was broken. 00:00:31
Now, Jacob, don't jump to conclusions. 00:00:33
And besides, Mr. Gunnow said the 29 GPS satellites orbit the Earth. 00:00:36
It's possible, but not likely, that they're all broken. 00:00:40
I guess you're right, but what other explanation is there? 00:00:43
Either way, if we want to complete our assignment, we have to make sure this works. 00:00:46
It should be another 8 meters. 00:00:52
A little to the right. 00:00:54
I don't see anything. 00:00:55
Another 5 meters. 00:00:56
Oh, wait, I see something. 00:00:57
This is so cool. 00:00:58
I can't believe we found it. 00:00:59
RG to Headquarters. 00:01:00
We've found the geocache. 00:01:01
I repeat, we have found the geocache at the exact coordinates listed on the website. 00:01:02
Good work, guys. 00:01:16
Are you sure the coordinates are correct? 00:01:17
We're sure. 00:01:19
We've double-checked and double-confirmed. 00:01:20
Mission accomplished. 00:01:21
We're returning to Headquarters. 00:01:22
Over. 00:01:23
It looks like you were right. 00:01:24
I shouldn't have jumped to a conclusion. 00:01:28
Clearly, the satellites and the GPS devices are working properly. 00:01:30
And that's a good thing, but we still don't know what caused the problem in the first 00:01:33
place. 00:01:36
Let's go to the problem board. 00:01:37
Okay. 00:01:38
What do we know? 00:01:39
We know that our GPS malfunctioned in two different locations at the same time. 00:01:40
And we also know from Catherine and Tony's report that satellites communicate with GPS 00:01:44
devices through radio waves. 00:01:47
Of course. 00:01:49
And now we know that the problem was only temporary. 00:01:50
True. 00:01:53
Satellites and GPS devices are working fine now. 00:01:54
So what do we need to know? 00:01:56
We need to know more about radio waves and how they might be affected. 00:01:57
It might also help if we knew anyone else who had a similar problem. 00:02:00
So where do we go? 00:02:04
Let's email Ulla and Nina in Norway and see if they had the same problem on the same day. 00:02:05
Great idea. 00:02:09
We may not have this problem solved, but we're making progress. 00:02:10
Yes. 00:02:13
And we need to make a report for Tony. 00:02:14
Maybe he can help us from Colorado. 00:02:16
For some great ideas on creating your own reports, visit the Treehouse on the NASA SciFiles 00:02:18
website. 00:02:22
We read about the Treehouse detectives' problem with their GPS, but we weren't much help. 00:02:23
We were not geocaching on the same day. 00:02:35
And we haven't had any problems with our GPS. 00:02:38
We decided to ask Dr. D about it when we meet at the Alomar LiDAR Observatory. 00:02:41
I'm excited to finally be here at the observatory. 00:02:46
I read so much about it. 00:02:50
Dr. D, what kind of research is done here? 00:02:52
The scientists are investigating the middle atmosphere using lasers like this and radar 00:02:54
instruments. 00:02:58
Isn't radar what the police use to bounce off cars and see how fast they're going? 00:02:59
And weathermen use it to track rain and snow storms. 00:03:02
Exactly. 00:03:05
Radar sends out a beam of light which is reflected off the atmosphere and is then analyzed. 00:03:06
Did you just say that radar sends out a light beam? 00:03:10
I thought that radar used radio waves. 00:03:12
It does, but radio waves are a form of light. 00:03:14
There are many forms of light that are not visible. 00:03:17
Like what? 00:03:19
For example, this observatory uses microwave light to measure water vapor, infrared light 00:03:20
to detect clouds, and ultraviolet light to measure the ozone layer. 00:03:25
I've heard of ultraviolet light, but it's not visible. 00:03:28
All these different forms of light are part of what is called the electromagnetic spectrum. 00:03:31
Every form of light travels at 300 million meters per second in a vacuum and has a wavelength. 00:03:35
We learned that the wavelength is the distance between the crest of two successive waves. 00:03:41
That's right. 00:03:45
Some radio light has wavelengths that are hundreds of meters long, where ultraviolet 00:03:46
light wavelengths are very tiny, only about one ten-thousandth of a millimeter. 00:03:50
That's a big difference. 00:03:55
It is. 00:03:56
Light also has a frequency, which is its rate of vibration. 00:03:57
Here, hold on to this spring. 00:04:01
I'm going to make it vibrate and create what's called a standing wave. 00:04:04
The faster you move your hand, the shorter the wavelength. 00:04:16
Exactly. 00:04:24
And the shorter the wavelength, the higher the energy. 00:04:25
Which light has the most energy? 00:04:28
That would be gamma rays, followed by X-rays, ultraviolet, visible light, infrared, and 00:04:30
radio waves. 00:04:35
Wow. 00:04:36
I still can't believe that they're all called light. 00:04:37
Dr. D, the treehouse detectives want to know more about the radio waves the satellite uses 00:04:39
to communicate with GPSs. 00:04:43
Good question. 00:04:45
First, you need to know that there are a lot of different types of radio waves. 00:04:46
GPS satellites communicate with a type of radio wave called microwave. 00:04:51
I've heard of shortwave radio. 00:04:54
That's another type. 00:04:55
There are also AM and FM radio and TV. 00:04:56
But GPS satellites communicate with microwaves because these pass easily through the atmosphere 00:04:59
and are not absorbed. 00:05:04
Are the other forms of light absorbed by the atmosphere? 00:05:05
Not all of them. 00:05:07
Ozone in the atmosphere is absorbed most, but not all of the ultraviolet light. 00:05:08
Unfortunately, most of the X-rays and gamma rays are also absorbed. 00:05:13
But visible lights get through pretty easily. 00:05:17
Yes, the atmosphere is transparent to visible light. 00:05:19
I heard that some radio waves, like AM and shortwave radio, can bounce off the atmosphere 00:05:22
and travel great distances. 00:05:27
That's correct. 00:05:28
But FM radio and TV don't. 00:05:29
I also mentioned that all radio waves can be created by moving electrical charges. 00:05:31
The Kids Club members said you might want to learn more about electricity to solve your 00:05:36
GPS problem. 00:05:41
I agree. 00:05:42
And if camping conditions aren't too primitive, I recommend that you look up Dr. Baganal, 00:05:43
a friend of mine who studies electricity at the University of Colorado. 00:05:48
I know that we use electricity all the time, but I'm not sure what it is exactly. 00:05:53
It's a physical phenomenon associated with static and moving electrical charges. 00:05:57
Oh, I get it. 00:06:01
I'm sorry, would you repeat that again? 00:06:03
I know. 00:06:06
It's complex. 00:06:07
Electricity doesn't have a simple explanation, nor is it easy to understand. 00:06:08
So let's start with the basics. 00:06:12
Take this plastic stick and rub it against this cloth. 00:06:14
Okay. 00:06:17
Okay, now take this other one, made of the same material, rub it with the cloth and see 00:06:18
if you can try and put the ends together. 00:06:27
It looks like one is pushing the other. 00:06:36
Now rub this one made of a different material. 00:06:38
So now try and put them together. 00:06:42
The different stick pulled the first stick. 00:06:52
Why did it do that? 00:06:54
Well, let's figure it out. 00:06:55
Do you remember the parts of the atom? 00:06:56
Yes. 00:06:58
There is a nucleus with protons and neutrons surrounded by electrons. 00:06:59
That's correct. 00:07:02
And the protons are positively charged and the electrons are negatively charged. 00:07:03
And the neutrons are neutral. 00:07:07
Very good. 00:07:08
And positive and negative charges are attracted to each other. 00:07:09
We call that the attractive force. 00:07:12
Aren't all atoms basically neutral? 00:07:14
Yes, but when you put different materials together, sometimes the parts of the atoms 00:07:16
like to move. 00:07:20
However, some nuclei like to hang on to their electrons stronger than other nuclei. 00:07:21
The stronger nuclei gather electrons from the weaker nuclei. 00:07:26
Is that what happened when I rubbed the two different sticks with the cloth? 00:07:30
When you rubbed the first two sticks with the cloth, the electrons left the cloth and 00:07:33
gathered on the sticks. 00:07:37
And then because they were both negatively charged, they repelled each other. 00:07:38
So why did the different sticks attract one another? 00:07:42
Well, different materials cause electrons to move differently. 00:07:45
Oh, I get it. 00:07:48
With the different stick, the electrons gathered on the cloth, leaving the stick positively charged. 00:07:49
Because one stick was positively charged and the other one was negatively charged, 00:07:53
they attract each other. 00:07:56
Yeah, I think you've got it. 00:07:57
So this kind of electricity is called static electricity because the charges are stationary 00:07:59
and don't move. 00:08:03
Now, shuffle your feet on the carpet and then touch this metal object. 00:08:04
I have a bad feeling about this. 00:08:08
Shocking. 00:08:13
Can you explain why? 00:08:14
I'll try. 00:08:15
When I shuffled my feet, I gathered electrons from the carpet, making me negatively charged. 00:08:16
That's correct. 00:08:20
And what happened when you touched the metal object? 00:08:21
The extra electrons jumped over to the metal, causing pain. 00:08:23
Sorry, but you're right. 00:08:28
It's an example of what we call current electricity. 00:08:30
Watch what happens when I connect this end of the wire to this end of the hand generator. 00:08:33
This looks like a complete circuit, where the light bulb has the load. 00:08:39
When you turn the crank, you produce current, which is electrons flowing through the circuit. 00:08:42
And the light bulb glows. 00:08:46
Exactly. 00:08:49
Now watch what happens when I connect the generator to this circuit near these compasses. 00:08:50
Wait a minute. 00:08:56
The compasses moved. 00:08:57
Why'd they do that? 00:08:58
Initially, the compass was pointing towards the Earth's North Pole. 00:08:59
When we cranked the generator to make the current flow, a small magnetic field was created. 00:09:02
This field caused the compass needle to swing, 00:09:07
because the needle is, itself, a small magnet with a north and south end. 00:09:10
Very interesting. 00:09:15
The trails detectives need to know about this. 00:09:16
I'm sure they will. 00:09:18
I'm sure they will. 00:09:19
Very interesting. 00:09:21
The trails detectives need to know about this. 00:09:22
Thanks, Dr. Bagnall. 00:09:24
You're welcome. 00:09:25
I have some more experiments. 00:09:26
I didn't know that electricity was so cool. 00:09:28
Dr. Bagnall said that flowing electricity creates a magnetic field. 00:09:30
If that's true, then we need to know more about magnets and magnetism. 00:09:34
So what's up? 00:09:39
Will learning about magnets help the treehouse detectives? 00:09:40
What other information do they need to solve the mystery? 00:09:43
Find out in the next exciting chapter of The Case of the Technical Knockout. 00:09:46
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Idioma/s:
en
Niveles educativos:
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Autor/es:
NASA LaRC Office of Education
Subido por:
EducaMadrid
Licencia:
Reconocimiento - No comercial - Sin obra derivada
Visualizaciones:
746
Fecha:
28 de mayo de 2007 - 15:34
Visibilidad:
Público
Enlace Relacionado:
NASAs center for distance learning
Duración:
09′ 53″
Relación de aspecto:
4:3 Hasta 2009 fue el estándar utilizado en la televisión PAL; muchas pantallas de ordenador y televisores usan este estándar, erróneamente llamado cuadrado, cuando en la realidad es rectangular o wide.
Resolución:
480x360 píxeles
Tamaño:
59.33 MBytes

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