The Earth is almost spherical in shape, but slightly flattened at the poles and bulging at the equator. This shape is called an oblate spheroid.

• Equatorial diameter: approximately 12,756 km
• Polar diameter: approximately 12,714 km
• Circumference at the equator: approximately 40,075 km

Because the Earth is so large, its surface appears flat to us in our daily lives.

The Solar System consists of the Sun and eight planets that orbit around it. The Earth is the third planet from the Sun, between Venus and Mars.

The planets in order from the Sun are:

1. Mercury
2. Venus
3. Earth (our home)
4. Mars
5. Jupiter
6. Saturn
7. Uranus
8. Neptune

The Earth is about 150 million kilometres from the Sun. This distance is ideal for supporting life because temperatures are neither too hot nor too cold.

The Earth has two main movements:

Rotation

The Earth rotates (spins) on its own axis from west to east once every 24 hours. This causes day and night. As one side faces the Sun, it experiences daylight, while the other side faces away and experiences darkness.

Revolution

The Earth also travels around the Sun in an elliptical (oval-shaped) orbit. This journey takes approximately 365¼ days (one year). This movement, together with the Earth's tilted axis, causes the seasons (summer, autumn, winter, spring) as different parts of the Earth receive more or less direct sunlight throughout the year.

Latitude (also called parallels) are imaginary horizontal lines that run east-west around the Earth. They measure how far north or south a place is from the Equator.

Key facts about latitude:

• The Equator is the main reference line at 0° latitude
• Latitude increases from 0° to 90° north (North Pole) and 0° to 90° south (South Pole)
• Lines of latitude are parallel to each other and never meet

Important parallels:

Latitude helps us understand climate zones. Places near the Equator (0°) are generally hot, while places near the poles are cold.

Longitude (also called meridians) are imaginary vertical lines that run from the North Pole to the South Pole. They measure how far east or west a place is from the Prime Meridian.

Key facts about longitude:

• The Prime Meridian (also called Greenwich Meridian) passes through Greenwich, England, and is 0° longitude
• Longitude is measured from 0° to 180° east and 0° to 180° west
• All meridians meet at the North and South Poles

Using Latitude and Longitude Together

When we combine latitude and longitude, we can find any location on Earth. This is called geographical coordinates.

Example: A location at 40°N, 60°W means the place is 40 degrees north of the Equator and 60 degrees west of the Prime Meridian.

Longitude and Time

The Earth rotates 360° in 24 hours, which means:

• 1 hour = 15° of longitude
• 1° of longitude = 4 minutes of time

Worked example: If it is 12:00 noon at Greenwich (0°), what time is it in Dar es Salaam, Tanzania (39°E)?

• Time difference = 39° × 4 minutes = 156 minutes = 2 hours 36 minutes
• Dar es Salaam is east of Greenwich, so it is ahead in time
• Time in Dar es Salaam = 2:36 PM

In Tanzania, latitude and longitude are used by pilots and sailors to navigate aircraft and ships safely across the country. For example, when a plane flies from Julius Nyerere International Airport in Dar es Salaam to Kilimanjaro International Airport, pilots use coordinates to follow the correct flight path. Similarly, fishermen on Lake Victoria use these lines to mark their fishing zones and report locations accurately to rescue services if needed. Time zones also matter: Tanzania uses East African Standard Time (UTC+3), so when it is 12:00 noon in London (GMT), it is already 3:00 PM in Dar es Salaam.