A US ton is equivalent to 900 kg (2000 pounds). A British ton is 1008 kg (2240 pounds), called a gross ton.

Hydrogen gas is the least dense substance in the world.

The double-helix structure of DNA was discovered in 1953 by James Watson and Francis Crick. The length of a single human DNA molecule, when extended, is 1.7 metres (5 ft 5 in).

A square piece of dry paper cannot be folded in half more than 7 times.

Since space is essentially empty it cannot carry sound. Therefor there is no sound in space, at least not the sort of sound that we are used to.

The ozone layer averages about 3 millimeters (1/8 inch) thick.

The sun is 330,330 times larger than the earth.

The deepest point in the sea: the Mariana Trench off Guam in the Pacific Ocean; it is 10,9 km (6.77 miles) below sea level.

The tallest waterfalls in the world are Angel Falls in Venezuela. At 979 m (3,212 ft), they are 19 times taller than the Niagara Falls, or 3 times taller than the Empire State Building.

The order of the planets, starting closest to the sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.