Journey Through The Solar System, Episode 04 - Earth, The Planet
Transcript
00:00There is a blue shimmering jewel-like planet called Earth. Earth is a third planet from
00:23the sun. When men first looked back at Earth on their way to the moon, they realized how
00:29fragile and small our world appears in the vastness of space.
00:59Clearly, the study of Earth and its thin protective atmosphere is important for us to pursue.
01:25Now let's go to a NASA film called Earth, Space, Our Environment to learn how the sun's
01:31emissions affect Earth.
01:39Weather and climatic changes, atmospheric pollution and disturbances of the ozone layer,
01:48worldwide magnetic storms that disrupt radar and radio, telephone communications, and even
01:55cause power failures. All these may well be controlled by eruptions on the sun, which
02:04affect Earth's magnetism and create the auroras by means of a vast engine around the Earth,
02:11the magnetosphere. Because this magnetosphere can affect Earth in so many ways, understanding
02:20how it works might help us cope with climate and pollution variations, and even help us
02:25in planning the use of our food and energy resources. But how can we start to understand
02:31the magnetosphere?
02:35In 1600, William Gilbert told us the Earth was a great magnet extending into space. Ten
02:43years later, Galileo Galilei turned his telescope on the sun and recorded how its surface constantly
02:50changed. But then for 300 years, the sun and Earth pursued their courses, and no convincing
03:00theory was able to connect Galileo's solar changes with Gilbert's terrestrial magnetism.
03:10Until a solar theory in 1890 suggested that the sun throws out particles which travel
03:16to the Earth to be caught by its magnetism. In the 1950s, the sun's own magnetism, it
03:25was suggested, flowed into space to envelop the Earth and generate the auroras high in
03:30the terrestrial sky. Yet this was only speculation on how the sun might affect the Earth through
03:36an invisible magnetosphere. Only by actually getting measurements in space could the true
03:44facts be unearthed.
03:49In the late 20s, Goddard, the American, built the first practical rocket craft. The Russian
04:02Sputnik was the first space success. The American exploded the rocket, and it was the first
04:14rocket that was ever built. The spreading of the Sun's auroras soon followed, carrying
04:15with it a Geiger counter. The signals produced by the counter enabled Dr. James Van Allen
04:21to confirm that he was recording something real but unexpected in space.
04:27It repeatedly did the same thing in the same general range of altitude and latitude and
04:32longitude and therefore it must be a true physical effect that we were observing.
04:39This was the first discovery in space.
04:42The Van Allen radiation belts, particles invisible to the eye, which came perhaps from the sun,
04:47were trapped in the space around the Earth by the planet's magnetism.
04:52This was the first step in establishing a link between the sun and Earth through the
04:57magnetosphere.
04:58And when the radiation belts were discovered, I was very keen on the idea that the first
05:06particles from the sun would be able to fill these radiation belts, and that the stored
05:11particles we were seeing there were in part, or perhaps in major part, coming from the
05:16sun.
05:18And so the paper in which the word magnetosphere was coined was that there would be a region
05:24around the Earth where the Earth's magnetic field dominated the circumstances.
05:30The first concept of the magnetosphere was that of a region where Earth held particles
05:35that were captured from the sun.
05:37But did these particles really come from the sun?
05:53To find out, instruments had to be fired further out into space to really discover if the erupting
05:59surface of the sun did throw out particles and magnetism all the way to the Earth.
06:05And from space, this answer came back.
06:10Streams of particles flowed from the sun, dragging out the sun's magnetism, a solar
06:15wind rushing into space.
06:18But Earth's magnetism in the magnetosphere deflected the solar wind around the Earth.
06:24So how then could the solar particles get in and be caught?
06:30Solving this space problem could be difficult.
06:34You're going to have to have them penetrate to the atmosphere.
06:37And so one of the exciting things that had been done in the last few years was find that
06:41if we went clear above the Earth's poles, the plasma from the sun would directly come
06:45down into the atmosphere.
06:47This was the breakthrough.
06:49Solar particles detected entering directly into the magnetosphere.
06:55While within the magnetosphere, further measurement showed what was also invisible to the eye,
07:00seas of plasma particles around the Earth, and huge particle streams moving thousands
07:06of miles back from the tail, perhaps to directly ignite the brightest auroras.
07:12But what could drive the magnetosphere into these vast movements?
07:16Could the solar wind rushing past, outside the magnetosphere, supply the energy?
07:21Well, if I knew the answer to the question of how energy was transferred from the solar
07:28wind to the magnetosphere, I wouldn't be sitting in front of this camera talking about it.
07:33I'd be in my office writing as hard and as fast as I could to demonstrate what I believe
07:38to the colleagues which are also investigating this problem.
07:42It is contentious.
07:44One theory hinges on a magnetic connection, magnetism from the sun connecting with and
07:50dragging back Earth's magnetism.
07:55This would work like a dynamo in space, transferring energy into the magnetosphere where it is
08:00stored until suddenly released in a magnetic storm to disturb the Earth and create auroras.
08:11Now such auroras appear to be created when stored energy is released in a violent eruption
08:15throughout the magnetosphere.
08:19But where can proof of this be found?
08:22One place is the Arctic, where auroras are seen almost every night, and scientists search
08:30for clues to show how the magnetosphere collects energy from the sun, stores it, and suddenly
08:36releases it to the Earth, creating auroras and a burst of energy equal to that of a large
08:42earthquake.
08:54So analysis today concentrates on finding how the magnetosphere works and, in particular,
09:00what triggers its energy releases.
09:03Could it be changes in the solar wind?
09:08The solar wind does not flow steadily and regularly.
09:13It carries perturbations, shockwaves.
09:16Even the magnetic field changes in direction and intensity.
09:21When this happens, an instability is triggered in which suddenly an explosion occurs in the
09:27tail in which magnetic energy that has been accumulated during a certain time is suddenly
09:33converted into particle energy.
09:36And that typical solar wind particle that had been trapped in the tail now suddenly
09:41is accelerated toward the Earth.
09:44So changes on the sun, which change the solar wind, appear to trigger an energy-filled magnetosphere
09:51into a sudden spasm, creating a magnetic storm, the brightest auroras, and affecting
09:59the whole Earth environment.
10:04But there are still many of the apparent effects of the aurora borealis and the magnetic storms
10:13that defy detailed explanations, so there's a great deal more to be learned in the ionosphere
10:19and in the upper atmosphere of the Earth.
10:23So investigations continue.
10:26This is a computer simulation of the Earth and auroras from space, part of an experiment
10:31to measure exactly how magnetosphere energy creates them.
10:35And beyond this, there are active experiments.
10:39You really want to try to actively perturb the magnetosphere, the ionosphere, and the
10:43atmospheric system in controlled ways so that you're actually doing a laboratory experiment.
10:48If you know what the input is, then you can measure the response of the system.
10:53When we get to that point, we'll be able to really probe the specific processes which
10:58couple these regions together.
11:03In Canada, there is an active experiment underway in which radio signals, which disturb the
11:07magnetosphere, are received from the opposite hemisphere of the world, the Antarctic.
11:13The signals injected here arc through the magnetosphere to give a record of the changes
11:18that are happening there.
11:22The most active experiments will be done with man in space, on the space shuttle.
11:27With the space shuttle, we get the opportunity to put man into the experiments.
11:33Given the new capability that the shuttle will have, we'll be able to conduct a brand
11:39new variety of experiments that we've never had the capability to do before.
11:44And the scientist will be able to interact with the medium surrounding the vehicle, will
11:49be able to probe the medium, perturb the medium, and measure the responses.
11:52And that's really the way you understand things.
11:56So what is understood of Earth space today?
12:00Laboratory simulations of a magnetic Earth and the solar wind streaming at it have been
12:04able to produce a visible representation of the magnetosphere.
12:10But the picture is blurred and out of scale.
12:14Only space measurements are valid in constructing a true diagram of the magnetosphere and its
12:19movements.
12:20Simplified images of this complex engine in Earth space, where until recently there was
12:25thought to be only empty stillness.
12:28This is, however, a gauge of our present-day understanding and ability to predict how changes
12:33on the sun will, in some ways, affect the magnetosphere and Earth environment.
12:40So today, at forecast centers like this, the sun is kept under watch around the clock.
12:45Activity in region 331.
12:47What kind of activity do you have?
12:50The filament in 331 is active.
12:53It is shifting off bands to the red.
12:56Flare.
12:57Beginning in 331.
12:58Start time 1958.
12:59Location, north 13, east 28.
13:02Dad, I've got a big flare.
13:06Could you give me some help?
13:09Today, we know that the magnetosphere is a complex engine through which the sun causes
13:15enormous disturbances to the Earth's environment.
13:18FAA, this is the forecast center in Boulder.
13:21I'd like to report a major solar flare in progress.
13:25When we learn all the details of how the magnetosphere works, we will be able to predict its effects
13:30on the atmosphere and its influence on short- and long-term weather patterns and on changes
13:36in the Earth's ozone layer.
13:38Then we would know what changes to expect in our environment when we see the sun shaken
13:43by a huge eruption.
13:46All this lies in the future, but many think the groundwork is now being laid.
13:52Ecology, the balance of nature, is important to all life.
13:57One of the tools we can use to monitor this balance of nature on Earth is the satellite.
14:03Satellites can be used to observe our planet from a high vantage point.
14:08A NASA film called Remote Possibilities tells the story.
14:13From far out in space, the Earth appears serene and beautiful, displaying no hint of our crowded
14:19planet's many problems.
14:27As we have used and changed our planet, we have become aware that in many ways we are
14:36exhausting.
14:38Exhausting our food supplies, our sources of energy, our natural lands.
14:47Exhausting the potential of even the once seemingly limitless oceans.
14:52Management of Earth's resources is at a critical stage.
14:56It has never been more important that we understand the environmental relationships
15:00of our planet.
15:06Scientists are striving to apply the technology of the space age, the quest for more and better
15:12information about these complex relationships.
15:16In 1972, a new kind of satellite left the launch pad and rose to an altitude of 910
15:23kilometers from Earth.
15:26There it settled in a circular orbit around the planet.
15:30This satellite, called Landsat, opened a new era of Earth resource management.
15:38Landsat's recordings of the Earth's surface are not photographs as we usually think of
15:42them.
15:43They are images.
15:45Images formed using the techniques of remote sensing, that is, sensing from a distance.
15:51We're all familiar with remote sensing.
15:54You're using a remote sensor to view this film.
15:57Landsat uses another kind of sensor, an oscillating mirror, which captures the light reflected
16:03from the Earth's surface.
16:08Different areas of the Earth's surface reflect varying amounts of light.
16:19The oscillating mirror of Landsat's multispectral scanner directs light reflected from the surface
16:25of the Earth to four sets of sensors inside the satellite.
16:33Each of these four sets of sensors is sensitive to a different wavelength of light.
16:39Light as perceived by our eyes is only a part of the electromagnetic spectrum.
16:44Other parts of this spectrum include ultraviolet light and infrared light.
16:49Landsat is sensitive to the red and green bands of light in the visible spectrum and
16:54to two infrared bands.
16:59These are the wavelengths of light, called spectral bands, which are used to create Landsat's
17:05unique images.
17:11An astronaut can bring back film when he returns to Earth, but Landsat, which will orbit for
17:16years, cannot.
17:20Instead, it transmits signals which are used to form images.
17:30Landsat's oscillating mirror scans the ground and receives light from small areas called
17:36picture elements, or pixels.
17:39Each pixel is 1.1 acres, approximately the size shown here.
17:47Landsat receives the light reflected by a pixel.
17:50Sensors inside the satellite give the light a number between 0 and 63.
17:56Bright areas receive high numbers.
17:58Areas with less reflectance receive lower numbers.
18:02Each area of the Earth is seen as a pattern of lights and darks, coded with numerical
18:07values in each spectral band.
18:23Landsat sends these numbers to receiving stations on Earth, where technicians record them for
18:28future use.
18:315304
18:34Transmitter drive is on.
18:392A, go for command.
18:415354
18:43Victory orbit 13, 5952
18:536493
18:566493
19:02Link 4 signal strength negative 113.
19:06The numerical information is received and stored on tape, which can then be used to
19:14make images on film.
19:18There are over 7 million pixels in a Landsat image.
19:24The amount of light each pixel reflects is recorded as a numerical value.
19:28These numbers, one for each pixel, are now converted to the blacks, whites, and grays
19:33of a Landsat image.
19:35This process happens simultaneously in each of the four spectral bands, producing four
19:41black and white images of the same scene.
19:46At any given point in an image, the reflectance value is different in each of the four spectral
19:51bands.
19:53For example, the outlined area, a redwood forest, might vary in reflectance from 15
19:59to 35.
20:01By combining these separate black and white images and printing them through color filters,
20:06the differences in them can be used to emphasize specific Earth features.
20:11The colors, however, are not normal.
20:13Vegetation, for example, is seen as red.
20:18For many uses, these photographic products of Landsat data are a great advancement over
20:23any other form of aerial surveillance.
20:29The photographic product is a very useful tool, but it does have one disadvantage.
20:34It does not allow us to display and analyze each pixel, that is, each picture element.
20:40However, this can effectively be done with a digital computer.
20:46We can use the cursor or the light square there in order to train the computer on a
20:51particular theme that we want to analyze.
20:54In this case, it's the sediment emptying out into the ocean from a river.
21:01We can now display all similar areas of sedimentation in the image in a particular color.
21:09In this way, we can display the numerous themes which exist in the imagery on the digital computer.
21:18Landsat views offer researchers one totally new service.
21:23The satellite orbits the Earth in such a way that it always passes over the same area at
21:28the same time of day, recording exactly the same spot on Earth once every 18 days.
21:34This repetitive coverage provides an ideal tool for monitoring changes on the Earth.
21:40For example, note how well these images of the Washington, D.C. area show seasonal changes.
21:47The bright reds indicate the healthy vegetation of spring and summer.
21:57The edge of a snowfall is clearly defined on the winter image.
22:01Landsat images contain a wealth of detailed information, some of it obvious, but much of it very subtle.
22:07These images provide raw material to be studied and interpreted by people engaged in many kinds of research.
22:15I've been working with managers of the Great Dismal Swamp to make a plant association map of this 125,000 acre area.
22:25The managers of the Great Dismal Swamp are very interested in finding a method that is reliable to make these maps
22:33because the area to be mapped is so difficult to walk around in.
22:38Not only difficult to walk around in, but difficult because of all the bugs and standing water.
22:46The importance of monitoring the Great Dismal Swamp is to preserve one of the eastern seaboard's last remaining wildlands.
22:55Music
23:03When we began mapping the Dismal Swamp, certain features were easily located.
23:08Lake Drummond, in the center of the swamp, stood out clearly.
23:12Music
23:24The cleared areas show up distinctly.
23:27This area was cleared by a lightning fire.
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24:03One area on the computer scene puzzled us.
24:06It showed up as evergreens, but different from the evergreens which we had previously mapped.
24:12Music
24:15We checked it out with a trip to the swamp.
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24:28We discovered that Landsat had identified a beautiful cedar forest.
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24:44The final product of our research was a thematic map of the Dismal Swamp showing plant associations.
24:51In the future, we will be able to compare new Landsat images to this base map
24:56in order to monitor changes that take place in the swamp.
24:59Music
25:04Landsat's imagery is available for use by anyone in any nation.
25:09The EROS Data Center in Sioux Falls, South Dakota, distributes images and tapes to people all over the world.
25:16Music
25:22Landsat's images are providing new sources of information about many different kinds of Earth resources.
25:28Music
25:33A satellite is being used to map the extent of flood damage.
25:37Landsat's before and after images make excellent maps to study how fast water recedes and damaged land recovers.
25:46Landsat is keeping track of land development.
25:49For example, how well areas damaged by strip mining are being reclaimed.
25:53Music
25:58Scientists are using Landsat to map remote areas as possible wildlife habitats.
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26:05To search the Earth's surface for clues to new mineral deposits.
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26:15To inventory the world's agricultural crops so that food and fiber resources can be better managed.
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26:24Future geography books will use Landsat images to show the world as it really is.
26:29This map, made of 569 separate Landsat images carefully pieced together, gives a dramatic view of the United States never before available.
26:38Music
26:43Perhaps it is Landsat's beautiful views of the Earth which remind us most of all that the Earth is a treasure.
26:52Other satellites in orbit some 22,000 miles above Earth provide important views of weather.
26:59Daily forecasting of weather is more accurate than in the past.
27:03Because satellites are able to see the formation of storms and other weather conditions at remote parts of the Earth.
27:10The storms can then be tracked to the more populated regions.
27:15Twelve American astronauts walked on the moon looking for clues about the origin of the solar system perhaps preserved there.
27:24But first we had to photograph the moon from close range and land probes to see if it was safe for men to land.
27:32During our next program, assignment Shoot for the Moon, we will see how the moon was studied before men went there.
27:39This is Larry Ross saying goodbye from NASA's Lewis Research Center in Cleveland, Ohio.
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