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Then President Kennedy decided that an American should land on the moon. He provided funds to NASA (National Aeronautics and Space Administration) to run the space program. In addition to space flights, NASA has put many satellites into orbit. Satellites stay at a specific height and move at a specific speed as they circle our planet. The Earth’s gravity holds them in orbit. We rely on these satellites every day.
Six kinds of satellites orbit our planet. Earth observation satellites keep track of the conditions of oceans, icebergs, volcanoes, and deserts. They also track forest fires and animal herds. Spy satellites watch military movements. Weather satellites record cloud movements and wind speeds. Global Positioning System (GPS) satellites let cars, planes, and ships know their precise position on the Earth. Astronomy satellites keep track of the sun, stars, and comets.
Communications satellites get signals from computers, telephones, and TV cameras. Then they send these signals to another computer, phone, or TV. They handle e-mails and long-distance phone calls. They let you watch what’s happening in another part of the world while it’s happening.
Out in space the sun always shines because there is no night or clouds. So satellites use solar cell power. The solar cells collect the sun’s rays and change them into electricity. Solar cells work for many years, and astronauts on the space shuttle can go up and fix them if there is a problem.
1. What is a satellite?
2. Name some different kinds of satellites.
3. Would you like to be one of the astronauts who fixes satellites out in space?
Airplanes fly their long-distance flights in the stratosphere, the second layer of the Earth’s atmosphere. One reason for flying in the stratosphere is the density of the air greatly decreases in this region 15 – 30 kilometers above Earth’s surface. Airplanes tend to stay toward to lower portion of the stratosphere to take advantage of the jet stream, a fast moving air current located near the border of the troposphere.
A few characteristics of the other layers are as follows:
Troposphere: location of weather patterns
Contains 75% of the mass of the atmosphere
Mesosphere: low air density
rapidly decreasing temperatures
Thermosphere: very thin
The few molecules of air are extremely hot
Other than the reasons already given, why do you think airplanes fly in the stratosphere rather than in the troposphere, mesosphere or thermosphere?
Some people still believe the Earth is flat. Members of the Flat Earth Society believe that the Earth is a disk centered at the North Pole with a 150-foot wall of ice at the edge.
Proponents of the flat Earth theory were challenged when photographs of a spherical Earth were taken from space and the moon. The Society responded by claiming that the moon landings were a hoax that was staged by
The most recent president of the Flat Earth Society died in 2001 and the future of the Society remains uncertain. You can, however, still find information supporting their theories on the internet.
Science, of course has much evidence to a spherical Earth. Some of these points are presented here:
- Photographs of a spherical Earth
and Sunset Sunrise
- Ships on the ocean see landmarks rise or fall on the horizon
- Lunar and solar eclipses
Which of science’s explanations do you feel is the strongest proof that the Earth is indeed round? How do you think it is possible that some people still believe in a flat Earth? At what point, if ever, does any scientific explanation become proof?
Perspective is an amazing thing. It is our perspective from Earth that leads to one of the greatest astronomical events the average person can see: the solar eclipse.
The sun is approximately 400 times the size of the moon. How is it, then, that the moon can appear to completely cover the sun? It’s like this… if you close one eye and hold your thumb up to the other one, your thumb can almost completely cover anything you choose… a house, your mom, the large plate of broccoli on your plate. It’s just a matter of perspective.
The sun also happens to be approximately 400 times the distance from the Earth as the moon. Because these ratios of distance and size are the same, the sizes of the sun and the moon from Earth are about the same. This allows for the phenomenon of the solar eclipse.
There are three types of solar eclipse:
PARTIAL SOLAR ECLIPSE
This occurs when the moon partially covers the sun
TOTAL SOLAR ECLIPSE
This occurs when the moon completely covers the sun
ANNULAR SOLAR ECLIPSE
This occurs when the sun and moon are exactly aligned as in a total eclipse, but the moon appears smaller than the sun, thus leaving a bright ring surrounding the outside of the moon.
How do you think an annular solar eclipse occurs? What must be true to give us this different perspective? Have you ever seen an eclipse? What was it like?
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