All facts — Page 4

The Andromeda galaxy, 2.5 million light-years away, is the most distant object easily seen with the naked eye.

Under a dark sky it appears as a faint, elongated smudge. The light we see left it about 2.5 million years ago, when…

Mimas, a moon of Saturn, has a crater so big that it looks like the Death Star from Star Wars.

Herschel crater is about 139 km wide, roughly a third of the moon's entire diameter. The impact that made it nearly…

A comet's tail always points away from the Sun, even when the comet is moving away from it.

The tail is not a trail left behind by motion: it is gas and dust pushed by the solar wind and the pressure of…

The Earth is closest to the Sun in early January, in the middle of the northern hemisphere's winter.

At that point the Earth is about 147 million km from the Sun; in early July it is about 152 million km away. The…

Mercury has a tail of sodium atoms millions of kilometres long, similar to a comet's.

Sunlight and micrometeorite impacts knock sodium atoms off the surface, and the pressure of sunlight pushes them…

Phobos, Mars's largest moon, gets closer to the planet every year and will eventually be torn apart.

Phobos orbits so close to Mars that gravity is slowly braking it: it drops about 1.8 metres per century. In 30 to 50…

By solving reCAPTCHA tests, millions of people unknowingly helped to digitise old books and newspapers.

Created in 2007 at Carnegie Mellon University, reCAPTCHA showed one known word and another that computers had failed…

The Java programming language was originally called Oak, after an oak tree.

In 1991 James Gosling of Sun Microsystems named the language after the oak tree outside his office window. Since…

The Ctrl+Alt+Delete shortcut was created in 1981 by an IBM engineer to restart the computer without switching it off.

David Bradley designed it for the programmers of the first IBM PC, picking three keys far apart so that nobody would…

Nokia started out in 1865 as a paper pulp mill in Finland.

The engineer Fredrik Idestam opened the mill by a river, and the name came from the town of Nokia, where it later…

Samsung was founded in 1938 as a small company selling dried fish, vegetables and noodles.

Lee Byung-chul opened the business in Daegu, Korea, with about 40 employees, exporting goods to China. The name means…

The first hashtag was proposed in 2007 by a Twitter user, not by the company itself.

Chris Messina suggested using the # symbol to group conversations, with the example #barcamp. Twitter thought the…

Junk email is called 'spam' because of a Monty Python sketch.

Spam is an American brand of canned meat from 1937. In a 1970 sketch set in a café where every dish contains Spam, a…

The first iPhone, from 2007, could not copy and paste text.

The feature only arrived in June 2009 with version 3.0 of the system. The first iPhone also had no app store, no…

Velcro was inspired by burdock burrs stuck to a dog's fur.

In 1941, after a walk with his dog, the Swiss engineer George de Mestral saw under a microscope that the burrs had…

Tetris was created in 1984 at a research centre in Moscow, in the Soviet Union.

Alexey Pajitnov worked at the Academy of Sciences and programmed the game on a computer with no graphics, using…

Super glue was discovered by accident in 1942, during a search for a clear plastic for gun sights.

Harry Coover, at Kodak, tested cyanoacrylates, but they stuck to everything and were set aside. In 1951 he came…

Osmium is the densest natural element: a litre of it would weigh more than 22 kilograms.

At about 22.6 grams per cubic centimetre, it is twice as dense as lead and slightly denser than iridium. It is a…

A corn kernel pops at about 180 °C, when the water inside it turns into steam.

The hard hull keeps the steam trapped, and the pressure rises to about nine times that of the air. When the hull…

On a very hot pan, water drops skate around and last longer than on a pan that is merely hot.

This is the Leidenfrost effect, described in 1756. Above about 200 °C, the underside of the drop evaporates instantly…

Fluorine is the most reactive chemical element and reacts even with glass and some noble gases.

It is so aggressive that several chemists were injured or killed trying to isolate it. The Frenchman Henri Moissan…

Aluminium was once more valuable than gold, and the tip of the Washington Monument is an aluminium pyramid.

Although it is the most abundant metal in Earth's crust, it was extremely hard to extract from ores. In 1884 the…

Penicillin was discovered by accident in 1928, in a mould that grew on a forgotten laboratory dish.

Returning from holiday, Alexander Fleming noticed that bacteria had died around a mould of the genus Penicillium…

The first X-ray image, made by Wilhelm Röntgen in 1895, showed his wife's hand, wedding ring and all.

Röntgen discovered an invisible type of radiation that passed through skin but was stopped by bones and metal. He…