A two-stroke engine is a type of internal combustion engine with a cycle of only two (power) strokes.
The battle of the Greek-Persian War became famous for the heroic sacrifice of the Spartan soldiers.
The oxygen cycle describes the movement of oxygen within its three main reservoirs.
The masterpieces of ancient Greek potters are important archaeological artefacts.
The building complex was one of the most important Benedictine abbeys for centuries.
Viking leaders were elected from tribe members by the right of blood or an act of bravery.
The battle ended with the overwhelming victory of the Macedonian army over the Persian army led by Darius III.
Quetzalcoatlus was one of the largest known flying animals of all time.
Gladiators were combatants who entertained audiences in fights against each other or wild animals in ancient Roman arenas.
This animation demonstrates the structure and operation of different types of optical disc drives.
The phosphorus cycle describes the movement of phosphorus through the lithosphere, hydrosphere, and biosphere.
A species of venomous snakes widespread in Europe. Its bite is rarely fatal to humans.
The battleship USS Missouri, first deployed during WWII was also deployed in the Gulf War.
Two meshing gears transmit torque during their rotational motion.
One of the most important monocot crops.
In summer, monsoon winds bring heavy rainfall from the ocean to the continent.
Types of bridges include beam-, arch-, suspension-, cantilever and truss bridges.
This animation demonstrates the structure and operation of digital cameras.
This animation demonstrates the geographical locations of the Earth's major cities.
This animation demonstrates the main sources of soil pollution.