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 arms (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 is 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