There is zero gravity at the centre of earth.

Oceanography, the study of oceans, is a mixture of biology, physics, geology and chemistry.

Earth orbits the sun at an average speed of 29.79 km/s (18.51 miles/sec), or about 107 000 km/h (about 67,000 miles/hour).

Earth is the densest planet in the solar system and the only one not named after a god.

the deepest mine in the world is Western Deep Levels near Charletonville, South Africa. It is 4,2km (2.6 miles) deep.

The US has one of the highest fire death rates in the industrialised world, with more than 2 million fires reported each year.

The one place where a flag flies all day, never goes up or comes down, and does not get saluted, is the moon.

The largest iceberg ever recorded was 335km (208 miles) long and 97km (60 miles) wide.

There are 1040 islands around Britain, one of which is the smallest island in the world: Bishop’s Rock.

The magnetic south pole was discovered off the coast of Wilkes Land in Antarctica.

The Dead Sea is 365 m (1,200 ft) below sea level.

Summer on Uranus lasts for 21 years – but so does winter.

Planets, meaning wanderers, are named after Roman deities: Mercury, messenger of the gods; Venus, the god of love and beauty; Mars, the god of war; Jupiter, king of the gods; and Saturn, father of Jupiter and god of agriculture; Neptune, god of the sea.

One year on earth is 365.26 days long. One day is 23 hours, 56 minutes, and 4 seconds long. The extra day in a leap year was introduced to compensate for the discrepancy in the Georgian calendar.

There are more than 326 million trillion gallons of water on Earth.

More than 70% of earth’s dryland is affected by desertification.