When the Sun, Earth, and the Moon are arranged in a straight line, the Moon can partially or completely obscure the Sun.
Saturn is the second largest planet in the Solar System, easily recognisable by its rings.
Dry land on the surface of Earth is divided into continents which are separated by oceans.
The rise and drop of sea levels caused by the gravitational force of the Moon.
Lateral compressive forces cause rocks to form folds. This is how fold mountains are formed.
Water on Earth is in a continuous state of change. The water cycle includes processes such as evaporation, precipitation, melting and freezing.
Machines converting the energy of flowing or falling water into useful forms of power were already in use in the Middle Ages.
The device that transmits human voice as electrical signals was invented by Bell in 1876.
The American inventor presented his invention revolutionising telecommunication at New York University in 1837.
One of the most modern means of transport is the Maglev, capable of travelling at speeds of over 400 km/h.
The atomic bomb is one of the most destructive weapons in human history.
Typical settlements of the Norsemen were not only established in Scandinavia, they appeared on distant areas as well.
The army of Alexander the Great successfully deployed siege towers in its attacks against fortifications.
This animation demonstrates the structure of nitrogen molecules, with one sigma and two pi bonds holding the atoms together.
A series of fortifications built to prevent incursions from northern nomadic groups.
The excellent road and aqueduct system covering the whole empire reflects well the development of the Roman civilisation.
The largest bronze-age building complex of ancient Crete was probably the centre of Minoan civilisation.
Archimedes was one of the most brilliant Greek scholars of ancient times, who made his mark with military inventions as well.
The magnificent capital of the Aztec Empire astonished even the Spanish Conquistadors.
Legendary geographical discoveries at the beginning of the Modern Age had not only redrawn maps, but also had a truly diverse impact.
At the end of the 18th century, mining boomed because of the great need for raw materials in the dynamically developing industry.
A phase transition is the change of a substance from one state of matter to another.