## The Earth

Topic 1 – Planet Earth

1.1 - Know that the shape of the Earth is an oblate spheroid

1.2 - Be able to use information about the mean diameter of the Earth (13,000 km)

1.3 - Understand the Earth’s major internal divisions and their features:
a} crust
b) mantle
c) outer core
d) inner core

1.4 - Be able to use the latitude and longitude co-ordinate system

1.5 - Be able to use the major divisions of the Earth’s surface as astronomical reference points, including:
a) Equator
b) Tropic of Cancer
c) Tropic of Capricorn
d) Arctic Circle
e) Antarctic Circle
f) Prime Meridian
g) North Pole
h) South Pole

1.6 - Understand the effects of the Earth’s atmosphere on astronomical observations, including sky colour, skyglow (light pollution) and ‘twinkling’ (seeing)

Topic 7 – Early models of the Solar System

7.6 - Be able to use the astronomical unit (1 AU = 1.5 × 108 km)

Topic 11 – Exploring the Solar System

11.9 - Be able to use the astronomical unit (1 AU = 1.5 × 108 km), light year (l.y.) and parsec (pc)
11.11 - Know that most bodies in the Solar System orbit the Sun in, or close to, a plane called the ecliptic
11.12 - Understand the use of transits of Venus (as proposed by Halley) to determine the size of the astronomical unit and thus the absolute size of the Solar System

In this section you will find out more about the Earth.

Earth is the planet we live on, and it’s the only place in space that we know sustains life.

The Sun sends light and heat to Earth, and because the Earth is round, only half of it is lit from the Sun at any time. The lit side is day, the unlit side is night, and day and night change for us because the Earth rotates, which takes one day.

We have seasons on Earth because it’s tilted, and takes a year to orbit the Sun.

An imaginary line goes around Earth at its widest point called the EQUATOR. North of this is the Northern Hemisphere, and south of it is the Southern Hemisphere.

Earth rotates on its axis at an angle of 23.5°. This is a key part of understanding our seasons and how stars move throughout the year.

At the end of this section take the mini quiz to test yourself.

###### Did you know?

The Earth is estimated to be 4.5 billion years old.

Every minute there are 100 lightning strikes around Earth.