Sound travels through water 3 times faster than through air.
A square piece of dry paper cannot be folded in half more than 7 times.
Air becomes liquid at about minus 190 degrees Celsius.
Liquid air looks like water with a bluish tint.
A scientific satellite needs only 250 watts of power, the equivelant used by two hour light bulbs, to operate.
The thin line of cloud that forms behind an aircraft at high altitudes is called a contrail.
Radio waves travel so much faster than sound waves that a broadcast voice can be heard sooner 18,000 km away than in the back of the room in which it originated.
A US ton is equivalent to 900 kg (2000 pounds). A British ton is 1008 kg (2240 pounds), called a gross ton.
The Space Shuttle always rolls over after launch to alleviate structural loading, allowing the shuttle to carry more mass into orbit.
Most of the air is about 78% nitrogen gas. Only 21% consists of oxygen. The remaining 1% consists of carbon dioxide, argon, neon, helium, krypton, hydrogen, xenon and ozone.
Argon is used to fill the space in most light bulbs. Neon is used in fluorescent signs. Fluorescent lights are filled with mercury gas.
Hydrogen gas is the least dense substance in the world.
Water expands by about 9% as it freezes.
In a desert, a mirage is caused when air near the ground is hotter than air higher up. As light from the sun passes from cooler to warmer air, it speeds up and is refracted upward, creating the image of water.
The typical bolt of lightning heats the atmosphere to 50,000 degrees Fahrenheit.
An electric oven uses one kilowatt-hour of electricity in about 20 minutes, but one kilowatt-hour will power a TV for 3 hours, run a 100-watt bulb for 12 hours, and keep an electric clock ticking for 3 months.
In the 6th century BC Greek mathematician Pythagoras said that earth is round - but few agreed with him.
Greek astronomer Aristarchos said in the 3rd century BC that earth revolves around the sun - but the idea was not accepted.
In the 2nd century BC Greek astronomer Erastosthenes accurately measured the distance around the earth at about 40,000 km (24,860 miles) - but nobody believed him.
In the 2nd century AD Greek astronomer Ptolemy stated that earth was the centre of the universe - most people believed him for the next 1,400 years.