WBBSE Class 9 Geography And Environment Chapter 1 Earth As A Planet Notes

WBBSE Chapter 1 Earth As A Planet Salient Points Introduction

In ancient times, people thought that the Earth was flat and in Greek civilisation people considered that the Earth was flat and rounded as a disc.

According to Greek scholar Anaximander, the Earth was a floating disc in the ocean surrounded by a round sky.

The Portuguese globetrotter Ferdinand Magellan provided the first direct evidence in favour of the concept that ‘the Earth is round’.

Earth appears blue from space because water bodies cover 71% of the Earth’s surface.

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Greek philosopher, Aristotle stated the concept of the Earth being a sphere by observing the relative position of the stars and the shadow of the Earth that falls on the Moon during a lunar eclipse.

To prove the spherical shape of the Earth, the Bedford Level experiment was conducted in 1870.

The boundary where the sky seems to meet the ground or the sea is known as the horizon.

A spherical object flattened at the top and bottom (north-south) and bulged out at the middle or centre (east-west) is an oblate spheroid.

WBBSE Class 9 Geography And Environment Chapter 1 Earth As A Planet Notes

WBBSE Class 9 Earth as a Planet Notes

The equatorial and polar diameters of the Earth are 12757km and 12714km respectively.

On the Earth’s surface, the gravitational force is lowest at the Equator and maximum at the Poles.

Scientist Henry Cavendish first determined the Earth’s weight.

Geoid means—like the Earth or the shape of the Earth is like the Earth itself.

Key Terms Related to Earth in Geography

Johann Benedict Listing was the first person to use the word ‘geoid’.

The Science related to measuring the shape of the Earth is called Geodesy.

IAU (International Astronomical Union) listed Pluto as a dwarf planet in 2006.

In ancient days, the distance measurement unit used in Greece was called stadia. 1 stadia = 185 metres.

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Earth As A Planet Class 9 WBBSE Geography Summary

The Pole Star’s angle of elevation is 90° at the North Pole and 0° at the Equator i.e. the Pole Star is visible at the horizon in the Equator.

The light of the Sun takes 8.2 minutes to reach the Earth.

The area of the Earth’s surface is about 510 million sq. km.

The actual circumference of the Earth is about 40075km.

Examples of Earth’s Habitable Conditions

The South Pole of the Earth is about 20 m flat.

The average temperature of the Earth is about 15°C.

The average density of the Earth is 5.515 grams/cubic centimetre.

The full form of GPS is the Global Positioning System. GPS helps to know the exact or correct location of any place on the Earth’s surface.

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