The Aztec Empire was a despotic, militaristic state ruled by the tlatoani.
Electric current can be generated by rotating an armature loop in a magnetic field.
The Byzantine Emperor was the head of the Byzantine Empire, the direct continuation of the Roman Empire.
The most important weapons of medieval Arab warriors were the bow and the sword.
The Incas´ rudimentary weapons were inadequate in their struggle against the Spanish Conquistadors.
The ‘upright man’ used tools and could set fire.
This animation shows the hierarchical structure of the Medieval Christian church.
The process of the decay of unstable nuclei is called radioactivity.
In ecology, a niche is a term describing the way of life of a species.
A string quartet consists of four string players, it appeared in the late 18th century.
The piano is one of the most popular instruments in the world. It is a chordophone which produces sounds mechanically.
An introduction to the relief and hydrography of China.
A differential allows the driven wheels of a car to rotate at different speeds when the car is turning.
The animation shows the way forces act on wheeled vehicles and vehicles with runners.
The phosphorus cycle describes the movement of phosphorus through the lithosphere, hydrosphere, and biosphere.
Viking leaders were elected from tribe members by the right of blood or an act of bravery.
Red deer are even-toed ungulates, ruminants. Their males have spectacular antlers.
The anatomy of annelids is demonstrated through the example of the common earthworm.
The cause of a heart attack is the blockage of a coronary artery. It is one the most common causes of death.
The French monarch got his epithet because of his opulent and extravagant lifestyle.