Pyramid ( free topic )
A pyramid is
a structure whose outer surfaces are triangular and converge to a single point
at the top, making the shape roughly a pyramid in the geometric sense. The base
of a pyramid can be trilateral, quadrilateral, or of any polygon shape. As
such, a pyramid has at least three outer triangular surfaces (at least four
faces including the base). The square pyramid, with a square base and four
triangular outer surfaces, is a common version.
A pyramid's
design, with the majority of the weight closer to the ground, and with the
pyramidion on top, means that less material higher up on the pyramid will be
pushing down from above. This distribution of weight allowed early
civilizations to create stable monumental structures.
Civilizations
in many parts of the world have built pyramids. The largest pyramid by volume
is the Great Pyramid of Cholula, in the Mexican state of Puebla. For thousands
of years, the largest structures on Earth were pyramids—first the Red Pyramid
in the Dashur Necropolis and then the Great Pyramid of Khufu, both in Egypt -
the latter is the only one of the Seven Wonders of the Ancient World still
remaining.
Khufu's
Pyramid, built mainly of limestone (with large red granite blocks used in some
interior chambers), is considered an architectural masterpiece. It contains
over 2,000,000 blocks ranging in weight from 2.5 tonnes (5,500 lb) to 15 tonnes
(33,000 lb) and is built on a square base with sides measuring about 230 m (755
ft), covering 13 acres. Its four sides face the four cardinal points precisely
and it has an angle of 52 degrees. The original height of the pyramid was 146.5
m (488 ft), but today it is only 137 m (455 ft) high as 9 m (33 ft) has gone
missing due to theft of the fine quality white Tura limestone covering, or
casing stones, for construction in Cairo. It remains the tallest pyramid