Cave

Cave

A cave or cavern is a hollow place in the ground, especially a natural underground space large enough for a human to enter. Caves form naturally by theweathering of rock and often extend deep underground. The word cave can also refer to much smaller openings such as sea caves, rock shelters,

and grottos. read more

Deserts

Far from being barren wastelands, deserts are biologically rich habitats with a vast array of animals and plants that have adapted to the harsh conditions there. Some deserts are among the planet's last remaining areas of total wilderness. Yet more than one billion people, one-sixth of the Earth's population, actually live in desert regions. read more

Paper

Paper is a thin material produced by pressing together moist fibres of cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets. It is a versatile material with many uses, including writing, printing, packaging, cleaning, and a number of industrial and construction processes.read more

Space

This article is about the general framework of distance and direction. For the space beyond Earth's atmosphere, see Outer space. For the keyboard key, see Space bar. For other uses, see Space (disambiguation).

A right-handed three-dimensionalCartesian coordinate system used to indicate positions in space.

Space is the boundless three-dimensional extent in which objects and events have relative position and direction.^[1] Physical space is often conceived in three linear dimensions, although modern physicists usually consider it, withtime, to be part of a boundless four-dimensional continuum known as spacetime. read more