Hubble's mirror was ground wrong by 2.2 micrometres, dozens of times thinner than a hair.

1990 · 1993 · apart: 3 years

That was enough to blur its view: in 1993 astronauts flew up to fit corrective optics, in effect a pair of glasses.

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The event

• Launch of the Hubble Space Telescope1990 · Cape Canaveral. On 24 April 1990 Space Shuttle Discovery carried the Hubble Space Telescope into orbit. Once its flawed mirror was corrected in 1993, it helped pin down the age of the universe and discover its accelerating expansion.

20th century

More amazing facts

• 1989 In 1989, the year Tim Berners-Lee proposed the World Wide Web, the golden toad was seen for the last time in Costa Rica's forests.
• 1989 In 1989 PepsiCo bartered for 17 Soviet submarines.
• 1991 The world's first webcam watched a coffee pot. In 1991 Cambridge University computer scientists pointed a camera at their coffee machine so colleagues would not make a wasted trip to an empty pot.
• 1991 A single eruption cooled the whole planet.
• 1991 · 1992 Sergei Krikalev left Earth from the USSR and came back to Russia.
• 1992 The first text message ever sent was a Christmas greeting.

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