NCERT Geo Class 6 Chap – 1 – Page 4
Sun's Location, Composition and Pulling Force ? Sun's Distance from Earth ? Check Previous Page More Info Check Previous Page More Info Pluto Why not a Full-Sized Planet? What are Dwarf Planets? Check Previous Page More Info Earth Shape What is Sol ? Origin of Word Geography Who are Astronomers ?

Sun's Location, Composition and Pulling Force ?

While the Sun is Located in the Centre of the Solar
System but when we talk about its location in the Milky
way Galaxy The Sun (and, of course, the rest of our
solar system) is located near the Orion arm, between
two major arcs (Perseus and Sagittarius)
The sun Composition by mass :

⇒ Hydrogen: About 71% of the sun's mass
⇒ Helium: About 27% of the sun's mass
⇒ Other elements: About 2% of the sun's mass

The Sun accounts for 99.85% of all the matter of the
solar system

Suns Pulling Force

The sun's gravitational force is 274 meters per second
squared (m/s²), which is 28 times stronger than Earth's
gravity. The sun's gravitational field extends out to a
distance of up to two light years.

Sun's Distance from Earth ?

The distance from Earth to the Sun is 93 million miles
(149 million kilometers). In terms of light-years, it can be
quantified to 1.58 × 10-5 light-years. This is actually the
mean distance of the centre of the Sun to the centre of
the earth.

⭕Additional iNFO: Light Year?⭕ 

A light year is a unit of distance. It is the distance light
travels in one Earth year. A light-year is used to represent
astronomical distances. One Light Year = 9.4607×1012
kilometres

Pluto Why not a Full-Sized Planet? What are Dwarf Planets?

So, the three criteria of the IAU for a full-sized planet are:

1. It is in orbit around the Sun.
2. It has sufficient mass to assume hydrostatic
equilibrium (a nearly round shape).
3. It has “cleared the neighborhood” around its orbit.

⭕Additional iNFO: Dwarf Planets, Kuiper Belt⭕

Pluto meets only two of these criteria, losing out on the
third. It has not cleared the neighborhood around its orbit,
Pluto is considered a dwarf planet It orbits in a disc-like
zone beyond the orbit of Neptune called the Kuiper belt,
a distant region populated with frozen bodies left over
from the solar system's formation.

⇒ So Pluto is a Dwarf Planet and by definition Dwarf
planets are celestial bodies that orbit the sun and have
enough mass to be nearly round, but have not cleared
their orbit of debris.

The first five recognised dwarf planets are Ceres,
Pluto, Eris, Makemake and Haumea.

Earth Shape

Earth is a little flattened at the poles. We call this shape
Geoid. It has an equatorial circumference of 40075 km,
while that of Polar is 40008 km, thus a difference of 67
kilometers.

⭕Additional iNFO: Who gave the term Geoid?⭕

The term "geoid," which refers to the shape of the Earth,
was coined by Sir George Biddell Airy, an English
mathematician and astronomer. Airy served as the
Astronomer Royal of England from 1835 to 1881

What is Sol ?

In Roman mythology, Sol is the sun god, or the
personification of the sun. The family of the sun is,
therefore, called the solar system.

⇒ In geography, a sol is a solar day on Mars, which
s a unit of timekeeping on the planet.

Origin of Word Geography

The word geography comes from the Greek Origins,
Geo (Earth) and Graphia (Writing). Writing about Earth.
Other Words and their Origins from Greek are also given.
Geo (Earth) + Logy (the study of) = Study of the Earth
Geo (Earth) + Metry (Process of measuring) =
Measurement of the Earth

Geo (Earth) + Oid (Something resembling a (specified)
object) = Resembling the Shape of Earth

⭕Additional iNFO: Who Coined the Term
Geography⭕

The Greek scholar Eratosthenes (276–194 BC) was the
first person to use the word geography. He is known as
the "Father of Geography".

Who are Astronomers ?

Astronomers are scientists who study the universe and
the objects in it, such as planets, stars, galaxies, and
black holes. They use ground-based and space-based
equipment to make observations and conduct
experiments.

⭕Additional iNFO: Some Famous Indian
Astronomers and their Contribution to Geography⭕

⇒ Aryabhata (476–550 CE): A mathematician and
astronomer from ancient India who concluded theories
of earth rotation on its axis. He also measured the
distance between the earth and the moon to the nearest
millimetre. He also explained that planets and the moon
shine due to reflected sunlight. He also provided a
theoretical explanation for solar and lunar eclipses.
Famous books - Aryabhattiya. The final two parts of
Aryabhattiya, also known as Khagol-shastra, are about
astronomy.

⇒ Brahmagupta (598–668 CE): A mathematician and
astronomer who proposed a mathematical model for
planetary motion and contributed to the understanding
of eclipses. Calculating the Earth's circumference and
Also First to describing gravity as an attractive force.
Famous books- Brahmasphutasiddhanta - which covered
many topics related to astronomy and mathematics

⇒ Varahamihira (505-587 CE) He wrote about weather
patterns, cloud formation, rainfall, and how to predict the
weather using astronomical observations. Famous books
- Pancha Siddhantika: An account of the five systems of
Astronomy. Brahjataka: An astrological work

⇒ Bhaskara II (1114–1185 CE): His work documented
his observations of planetary positions, eclipses, and
cosmography. He also defined many astronomical
quantities, such as the length of a sidereal year.
Famous books -Goladhyaya, Siddhānta Shiromani are
an astronomical treatise