NIOS Environment Important Notes Part 2 for AEES, KVS, NVS, DSSSB, UPTET, REET, CTET, BTET, MPTET, HTET and All other Teaching Exams
The Earth
- The earth with its blue skies, vast oceans and lush green forests is the home to wide variety
of organisms. It has its own unique atmosphere. - The atmosphere also helps to regulate the
ambient (surrounding) temperature which is suitable for supporting life. - If you could dig a deep hole into earth the deeper you go, the hotter it becomes.
- At the
depth of about eight km it is hot enough to roast a human body. About 32 km deep you
would reach the part of earth which is called mantle. This is made of hard rock. - The
centre or core of the earth is approximately 6,400 km from the surface having a temperature
close to 5000ºC. Much of the earth’s core is hot liquid.
- As you already know, once every 24 hours, the earth rotates on its axis like a spinning top.
So the day and night cycle is of 24 hours. - A planet’s axis is an imaginary line passing
through the centre of the planet. - The earth not only rotates around its axis but
also revolves around the sun . The earth completes one full circle around the sun or completes
one orbit of the sun in 365¼ days. - An orbit is the path along which a planet moves around
the sun.
While earth revolves around the sun, moon orbits the earth. - The moon completes one
orbit in 27.33 days. The moon, as we know today, is without water and air and life. - From
the space, the earth looks like a beautiful bright bluish planet because of its blue oceans.
Ques 1: Approximately how old is the earth?
Answer: 4.5 billion years
Ques 2: Name the stare around which the earth revoloves along with other planets of the solar system.
Answer: Star
Ques 3: What do you mean by “solar system”?
Answer: Planets orbiting central star.
Ques 4: Why does the day and night cycle consists of only 24 hours?
Answer: Because earth completes one full rotation on its axis in 24 hours.
Ques 5: If you were to view earth from space, which colour would earth reflect?
Answer: Blue
Earth- The Unique Planet which sustains Life
In our solar system, earth is the only planet which is known to sustain life. Only earth has
air and water to support life.
air and water to support life.
Let us briefly review the conditions on the other seven planets of the solar system.
- Mercury (Buddha) is closest to the sun. It has a temperature range of 427ºC on its
side facing the Sun and – 270ºC, on its dark side. It has no atmosphere. - Venus (Shukra) is the closest neighbour of the earth. It is about 40 mk away. It is an
extremely hot planet with a temperature of 480ºC. Its atmosphere has 96% carbon
dioxide and poisonous gases like sulphur dioxide and carbon monoxide. - Mars (Mangal) is also close to earth. It is called the red planet. It has 95% carbon
monoxide and reddish dust. It is relatively a very cold planet and as of now presence of life on it has not been conclusively established. - Jupiter (Brahaspati) is the largest planet of the solar
system. It is mainly a rapidly spinning ball of gas specially
clouds of ammonia, and has no solid surface. - Saturn (Shani) consists mainly of hydrogen and helium.
Its atmosphere has 90% nitrogen and a temperature of
(-184ºC). It is also made up of hydrogen cyanide which
is a highly poisonous gas. It is characterized by a ring
that surrounds it. - Uranus (Arun) is also a very cold planet. Uranus is a
distant planet of solar system and 7th in order from the
sun. Uranus and Neptune are the outermost planets of
the solar system. Uranus has a highly tilted rotational
axis. - Neptune (Varun) is much smaller than earth, cold and
dark with its surface coated with frozen methane. - Earth is the only planet known to sustain life.
Scientists do not know of any other planet in the universe
besides the earth, where there is life. There are hundreds of
stars in the universe and they have planets orbiting round them. But whether the necessary
conditions to support life exist there is not known.
besides the earth, where there is life. There are hundreds of
stars in the universe and they have planets orbiting round them. But whether the necessary
conditions to support life exist there is not known.
As compared to other planets mentioned above, earth has the following unique conditions
which have enabled it to sustain life.
which have enabled it to sustain life.