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Q Is it true that the UK is tilted towards the south east?

A Yes - the south east of the country is slowly sinking into the sea while the north west of Scotland is slowly rising, because of a process called isostatic compensation, whereby something that has been covered by a heavy weight bounces back when that weight is removed. Scotland used to be covered by ice during the last Ice Age. When that weight disappeared, the area started rising, and has done so ever since. As Scotland rises, the rest of the UK is adjusting and the south of England has been sinking.

Q What was the biggest explosion in history?

A The biggest natural explosion was the eruption of Krakatoa on 27 August 1883. After a series of small explosions the volcano in Indonesia between Java and Sumatra blew itself to pieces. The explosion was heard four hours later on the island of Rodrigues, 2,968 miles away, where it was described as sounding like heavy guns firing. The largest unnatural explosion is claimed by the Russians, who say they detonated a 100-million-ton (100- megaton) nuclear bomb in the early Sixties.

Q How hot is oil when it comes out of the ground?

A There is a huge variation in temperature of oil from different reservoirs around the world. Oil from the Oola field, in the Norwegian North Sea, is at about 160C when it comes up from its reservoirs 3.6km deep. Oil from the Forties field in the British North Sea, formed at a depth of only 2.6km, arrives at the surface at about 96C.

Q How do we know snow crystals are unique?

A It's impossible to say that all snow crystals are unique because we can't examine every single one. However, we can say that snow crystals can form billions of different shapes, so it's unlikely you'll find two that are identical. The size and shape of each snow crystal depends on the temperature and amount of water in the air around it. This is constantly changing as they form, so their shape is very complex. And because it's the air very close to the crystal that matters, even two snowflakes forming right next to each other will be different.

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