The curvature of the lens of the eye changes when we look at a distant or at a near object, to ensure a sharp image.
This animation demonstrates how a turbojet engine works.
This animation demonstrates the functioning of the 3 basic types of water tap.
The army of Alexander the Great successfully deployed siege towers in its attacks against fortifications.
Yuri Gagarin became the first human in space on 12 April 1961.
The first supersonic passenger airliner entered service in 1976.
The Wright Flyer was the first successful powered, heavier-than-air aircraft, designed and built by the Wright brothers.
The excellent road and aqueduct system covering the whole empire reflects well the development of the Roman civilisation.
The first commercially successful technique of photography was invented by the French Louis Daguerre.
The central nervous system consists of the brain and the spinal cord, the peripheral nervous system consists of nerves and ganglia.
The Cassini spacecraft was exploring Saturn and its moons for nearly 20 years.
The two groups of angiosperms are monocots and dicots.
Commercial maritime routes of container ships form a global network.
A widespread snail species, also popular as food.
One of the best known buildings in the world, this is the residence and office of the President of the United States.
Olfactory receptors produce electric signals when stimulated by odours.
The centre of the Indian mausoleum complex is a white marble tomb built by Shah Jahan for his beloved wife.
In the Tudor Era around 200 buildings were built on the bridge across the River Thames.
When producing sound, the vocal cords are vibrated by the air flowing out of the lung.
Observatories are often built at high elevations to minimise the effects of atmospheric turbulence