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Earth
Many dream of traveling in space and viewing the wonders of the universe. In reality all of us are space travelers. Our spaceship is the planet Earth, traveling at the speed of 108,000 kilometers (67,000 miles) an hour. Earth, our planet, is the only planet in the solar system known to harbor life. All of the things we need to survive are provided under a thin layer of atmosphere that separates us from the uninhabitable void of space. Earth is made up of complex, interactive systems that are often unpredictable. Air, water, land, and humans themselves combine forces to create a constantly changing world that we are striving to understand.
Some facts are well known. For instance, Earth is the 3rd planet from the Sun at a distance of about 150 million kilometers (93.2 million miles). It takes 365.256 days for the Earth to travel around the Sun and 23.9345 hours for the Earth rotate a complete revolution. Our planet rotates on its axis at a surface speed of approximately 0.5 km/sec at mid-latitudes while orbiting the Sun at a speed about 30 km/sec. We experience these motions as the daily routine of sunrise and sunset and the slower change of the seasons. The four seasons are a result of Earth's axis of rotation being tilted more that 23 degrees. Earth has a diameter of 12,756 kilometers (7,973 miles), only a few hundred kilometers larger than that of Venus. Our atmosphere is composed of 78 percent nitrogen, 21 percent oxygen and 1 percent other constituents. The changing nature of the planet's systems are the mysteries that
scientists study today. For instance, the North American continent
continues to move west over the Pacific Ocean basin, roughly at a rate
equal to the growth of our fingernails.
We are Oceans at least 4 km deep covers nearly 70% of Earth's surface. Water exists in the liquid phase only within a narrow temperature span (0 degrees to 100 degrees C). This temperature span is especially narrow when contrasted with the full range of temperatures found within the solar system. The presence and distribution of water vapor in the atmosphere is responsible for much of the Earth's weather. On
the surface, we are enveloped by an ocean of air that consists of 78%
nitrogen, 21% oxygen, and 1% other constituents. Earth's atmosphere
shields us from nearly all harmful radiation coming from the Sun, and
protects us from meteors as well most of which burn up before they can
strike the surface. Satellites have revealed that the upper atmosphere,
which was thought to be Besides affecting Earth's weather, solar activity gives rise to a dramatic visual phenomenon in our atmosphere. When charged particles from the solar wind become trapped in Earth's magnetic field, they collide with air molecules above our planet's magnetic poles. These air molecules then begin to glow and are known as the auroras, or the Northern and Southern lights. Our planet's rapid spin and molten nickel-iron core give rise to a magnetic field, which the solar wind distorts into a teardrop shape. The solar wind is a stream of charged particles continuously ejected from the Sun. The magnetic field does not fade off into space, but has definite boundaries. As you observe Earth's finite boundaries, depicted on the front of this lithograph, consider the many unanswered questions and discoveries yet to be made on our own, home planet.
At the time the image was taken, Earth was 142 million kilometers (88 million miles) from Mars, On the Earth image we can make out the west coast outline of South America at lower right, although the clouds are the dominant features. |
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The Future
Astronauts of America Foundation Title; 'We help launch the future' slogan;
Character and Name Ikky;
and
The Future Astronauts of America
Foundation Logo are
intellectual property of The Future Astronauts of America
Foundation
From the
perspective we get on Earth, our planet appears to be big and sturdy with
an endless ocean of air. From space, astronauts often get the impression
that the Earth is small with a thin, fragile layer of atmosphere. For a
space traveler, the distinguishing Earth features are the blue waters,
brown and green land masses and white clouds set against a black
background.
NASA, in
partnership with other U.S. and international agencies, has been studying
Earth as an integrated system. Viewing Earth from the unique perspective
of space provides the opportunity to see Earth as a whole. Scientists
around the world have discovered many things about our planet by working
together and sharing their findings.
made aware of this
movement when it is interrupted by earthquakes. Scientists noticed a
distinctive pattern to those earthquakes, leading them to conclude that
Earth is dynamic, with its spherical surface separated into moving caps or
plates. Earthquakes result when plates grind past one another, ride up
over one another, collide to make mountains, or split and separate. These
movements are known as plate tectonics. Developed within the last thirty
years, this explanation has unified the results of centuries of study of
our planet, long believed to be static.
calm and uneventful, actually swells by day and
contracts by night due to solar activity. The upper atmosphere contributes
to Earth's weather and climate and protects us from the Sun's harmful
ultraviolet radiation.
