Page 110 - SST Class 06

other colours because it travels as smaller waves. The Sun and the Stars
That is why we see a blue sky most of the time. The Sun (or Sol), is the star at the centre of our

Closer to the horizon, the sky fades to a lighter solar system and is responsible for the earth’s
blue or white. The sunlight reaching us from low climate and weather. The Sun is an almost
in the sky has passed through even more air than perfect sphere with a difference of just 10 km in
the sunlight reaching us from overhead. As the diameter between the poles and the equator. The
sunlight has passed through all this air, the air average radius of the Sun is 695,508 km (109.2
molecules have scattered and rescattered the × that of the earth) of which 20–25% is the core.
blue light many times in many directions. The Sun is 150,000,000 (read 150 million) km
Also, the surface of the Earth has reflected and away from the earth. The light from the sun takes
scattered the light. All this scattering mixes the about eight minutes to reach the earth. This, in
colours together again so we see more white and other words, means that sunlight travels at a
less blue. speed of about 3,00,000 (exactly 299,792.458)
SOLAR SYSTEM km per second. The Sun is made up of extremely
The solar system is the family of the Sun. It is hot gases. It is said to have been formed from
described as a family because these heavenly moving cloud of hot gases called a Nebula. It
bodies go round the Sun and receive light and radiates energy in all directions. The Sun’s
heat from it. In fact, the Sun is the only source of
light and heat in the solar system. The other
members of the solar system are planets, their
moon, asteroids, comets and meteorites. We will
describe each of them, briefly.
Planetary Rings

The planet Saturn has amazing system of rings.
Some of the rings can be seen from the earth
through a telescope. The outer parts of the ring
system orbit at slower speed then the inner parts.
On the basis of this, scientists have concluded
Planets
that the rings consist mainly of ice and dust.
surface temperature is about 5,500°C and at its
center about 16,000,000°C. Another basic force
in the Universe is the force called the force of
gravity. The force of
gravity is an inher-
ent feature of
celestial dynamics
and is quite inde-
pendent of other
factors. Gravity
controls the move-
Planetary Rings
ment of all planets Sun

Social Science-6 110