The Gregorian calendar

Developed nearly 500 years ago, it is a variant of the Julian calendar. Today it is the most widely used calendar.

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Weather fronts

When masses of cold and warm air meet, weather fronts develop.

The subtropics

The subtropics are located between the tropical and temperate zones, between 23.5° and 40°...

The atmosphere

The atmosphere surrounds us everywhere on this planet. We take its presence so much for granted...

The terrestrial planets

Mercury, Venus, Earth and Mars may have they formed in much the same way, but only the Earth is...

Why is seawater salty?

Water covers about 71% of the Earth’s surface. But why are there two types of water on Earth,...

Exogenic forces

The surface of the Earth has been formed into its present state both by external and internal...

Oasis

Within the lethal embrace of deserts, life can only flourish because of large springs. Here...

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