Earth & Space Topics Overview
Earth & Space Topics Overview
Introduction
Our solar system consists of the Sun and the space surrounding it. Most of the space is virtually empty, but within it, there are the nine known planets and their moons. In addition, there are many millions of smaller objects: the asteroids and comets. These entire bodies orbit the Sun. Below is a diagram of our solar system.
The solar system
It is generally believed that our solar system formed nearly 5000 million years ago, from a cloud of interstellar gas and dust. Gravity caused the cloud to contract, with over 99.9% of the mass forming a young star (the Sun), at the centre of a flattened spinning disc. The planets formed within the spinning disc, and as a result, they all orbit the Sun in the same direction. All of the planets except Pluto orbit in the same plane (to within a few degrees), as would be expected from the 'spinning disc' model. Pluto's orbit, however, is tilted by about 17° to the plane of the Earth's orbit. This has led to speculation about Pluto's origin.
Orbits
Each planet has its own path around the Sun, called its orbit. The Sun is enormous thus; it has a very strong gravitational pull on the planets. Orbits are the paths, which planets move in due to the pull of the Sun. The further out you go, the weaker it pulls. The orbits of the planets are elliptical (elongated) rather than circular. This means that their distance from the Sun is continually changing. The average distance from the Sun to Pluto is much greater than the average distance to Neptune but because of the highly elliptical orbit of Pluto, there are times when Pluto is closer to the Sun than Neptune. The further the planet is from the Sun, the greater the time it takes to orbit it. The distance from the earth to the other planets depends on where they are in their orbits.
Relative size and distance of planets
Figure 1 Relative size
Planet
Astronomical
Units*
Millions of
Kilometres
Millions of
Miles
Mercury
0.4
57.9
36
Venus
0.7
08.2
67
Earth
.0
49.6
93
Mars
.5
227.9
42
Asteroids**
2.8
418.9
257
Jupiter
5.2
778.3
485
Saturn
9.5
,427.0
890
Uranus
9.2
2,869.6
780
Neptune
30.1
4,496.6
2810
Pluto
39.5
5,900
3670
* An astronomical unit (AU) is a distance unit based on the average distance of the Earth from the Sun.
** The asteroid belt is a region between the orbits of Mars and Jupiter in which most of the Solar System's asteroids are located. An asteroid is a small, generally rocky, solid body orbiting the sun and ranging in diameter from a few meters to hundreds of kilometers.
Earth and Moon
Locked together by gravity, the Earth and the Moon (the Earth's only natural ...
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2810
Pluto
39.5
5,900
3670
* An astronomical unit (AU) is a distance unit based on the average distance of the Earth from the Sun.
** The asteroid belt is a region between the orbits of Mars and Jupiter in which most of the Solar System's asteroids are located. An asteroid is a small, generally rocky, solid body orbiting the sun and ranging in diameter from a few meters to hundreds of kilometers.
Earth and Moon
Locked together by gravity, the Earth and the Moon (the Earth's only natural satellite) travel through space together, with the Moon circling the Earth about once a month. The Moon is the Earth's nearest neighbour in space, lying on average 385,000km away. During the lunar month, the Moon seems to change shape, going from a slim crescent to a full circle and back again. The Moon gives out no light of it's own and its apparent change of shape is caused by the fact that we see more or less of it lit up by the Sun as it circles the Earth. The changing shape of the Moon is called phases, and it goes through its phases every 291/2 days.
For a satellite, the Moon is remarkably large compared to its parent planet. Its diameter of 3476km is more than a quarter of that of Earth (12,756km). The Moon has less than one-eightieth of the mass of the Earth. Its gravity is also much less, being only one-sixth that of the Earth. However, weak as it is - it still affects the Earth. It tugs at the water in the oceans, causing the tides.
In contrast to the Moon's dry surface, the Earth is very wet - more than seven-tenths of Earth is water. The Earth's stronger gravity helps to hold down the atmosphere, which acts like a blanket by distributing the heat from the Sun by day. In addition, prevents too much of the heat escaping at night. This keeps the temperatures much more even than on any of the other planets or satellites.
The air on the Earth is a mixture of gases, mainly nitrogen (78%) and oxygen (21%). The presence of the oxygen coupled with the presence of abundant water on the surface; make it possible for life to exist on Earth in many different forms. Because of flowing water and winds, any part of the Earth's surface is no older than 1500 million years old even though the Earth is actually 4600 million years old. This is because of the effects off erosion and sandblasting. Therefore, the Earth's surface is geologically quite new. By contrast, the inactive Moon has been unchanged for 3000 million years.
Satellites
The term satellite refers essentially to one thing--a small body, natural or artificial, that revolves around a larger astronomical object. Data gathered from these satellites help us learn about the environment, the world, and the universe. The exciting new technologies being developed from these satellites have additional applications that benefit life on Earth.
Satellites of 1960's:
During the 1960's, satellite use began to flourish for the regular use of humans. In August 1960, the United States launched Echo I; this satellite reflected radio signals to Earth making satellite communication possible. Also in April in 1960, Tiros I was sent out to space. Tiros was the first weather satellite that sent pictures of clouds to Earth. The U.S. navy developed the first navigation satellite, the Transit IB navigation satellite that first orbited in April 1960. By 1965, more than 100 satellites were being placed in orbit each year.
Satellites of 1970's:
During the 1970's, there was innovation in the satellite world. New and more effective satellite instruments were being used. They have made use of computers and miniature electronic technology in satellite design and construction.
Satellites of 1980's:
During the 1980's, satellites were used to save people and other satellites. The first satellite salvaging operation took place in November of 1982, when the Palapa B-2 satellite was coaxed into Challenger's (another satellite) cargo hold by space walking astronauts.
Satellites of 1990's:
The uses of satellites in the 1990's rapidly grew for common, everyday tasks. For example, an independent company TRW Inc. planned to create a satellite system that would dominate the satellite communications network. This system called Odessey would be used for the phone business. TRW's satellites would focus on populated areas, as it would cover the Earth uniformly. According to Coy, "the company hoped to build a cost effective lucrative entry into the potentially explosive satellite phone business". These innovations have been getting better each day.
Conclusion:
For years to come, we the people will continue to innovate throughout the 21st century. With the development going the way it is the satellite industry will be productive for years to come.
Benefits
Communications
Communication satellites work non-stop 24 hours a day to keep the entire world linked together. Until recently NASA had been the only one's launching satellites, but now many private companies are benefiting from what a satellite can do. Once a satellite becomes geosynchronous, rotates with the earth orbit, a satellite is ready to work. It then beams messages to a ground station; the ground station receives these messages by using a device called a transponder. This interrupts the message and then distributes it. By doing this, satellite stations can than transport telephone service, data, or television transmissions to almost anywhere. These communication satellites are used for things like an overseas phone call or beaming 150 channels into your living room.
New advancements look to focus on packing more information into frequencies, because virtually all frequency transmitters are being used. In addition, this would allow more and more companies to transport all types of data.
Oceanography
Another use for satellites is in the field of oceanography. In 1798, the first three oceanography satellites went out ( Tirus, Nimbus 7, Seasat) and although they did not do, much they led the way to huge discoveries (Robinson 34). Now marine scientists and marine biologist are able to detect almost everything that goes on in the ocean. They use satellites to detect the oceans affect on environment, analyze wave patterns, monitor marine surface life, analyze ocean tendencies and currents, and get a complete synoptic view of the ocean. These things help them tell you what the water will be like, and help them find out about ocean life.
Astronomy
Astronomy satellites are mostly new technology. These satellites are mounted on earth-orbiting satellites or on deep space probes, and therefore can give us an unobstructed view with out the earth's atmosphere interfering. These satellites carry detectors to record electromagnetic radiation at wavelengths shorter than visible light (McGraw-Hill 41). Many different satellite astronomy techniques are used; one of the more prevalent ones is ultraviolet. Evolving in the 1940's, when Lyman Spitzer pointed out that the Earth's atmosphere is opaque to ultraviolet light. Out of ultraviolet developed solar ultraviolet, with a deeper space base it uses low and high spectral lines, to determine radiation on an object throughout the solar atmosphere. X-ray satellites are all used; it looks at x-ray emission from the sun and stars.
Surveillance
Lastly, an interesting satellite use is in the field of surveillance or spy satellites. There are four kinds of major satellites (White 100). The most commonly used one, reconnaissance use cameras to take pictures of a particular place from up above. They also have radar and infrared detectors so they can detect things in the dark or things that are covered by something or camouflage. Most of Russia's reconnaissance is known as COSMOS, the U.S. first one was called Big Bird. Ocean Surveillance satellites are used to search for ships or submarines. They can spot nuclear vessels. In addition, new advancements may allow them to scan the depths of the ocean. Early warning and "Elint" satellites are primarily used by the armed forces. These protect countries from sneak attacks, and can be used to detect if other countries are building or storing nuclear warheads. Elint is the basic spy satellite it picks up radio transmissions, and maps location of countries defense bases. It is the most important military satellite because it does not let another country to put together an attack without another country knowing.
Conclusion
As you can see satellites are integral parts of everyday life. They have thousands of uses and perform it without most ever being seen. Just think now how many satellite dishes you have seen on top of a house and that are just one aspect. Satellites are becoming increasingly advanced every year and will lead the way into the 21st century.
Aleemuddin Mohammad Khan Page 1 02/05/2007
