How long until the sun is a mile in diameter ? Finn

The sun will never be a mile across, it's much larger than that - over 110 times the diameter of the Earth and a million times the Earth's volume. But the sun will not remain in its present form for ever. At the moment it is about 4.5 billion years old and is 'burning' hydrogen to produce the heat and light that we rely on for our life on earth today. So far it has burned up about 50% of its hydrogen stores meaning that it should be okay for another 5-6 billion years. But once the hydrogen is all gone the sun will begin to burn up helium in its core and at the same it will swell into a 'Red Giant', engulfing the innermost planets in our solar system as it does so. This phase will last about 500 million years before the sun shrinks back to become a very dense 'white dwarf' not much bigger than the size of the earth. Although it will be very small, the white dwarf will be extremely dense - a teaspoonful of the material it is made from will weigh more than a tonne.

March 2003

What would happen if a bird drank fizzy water ? Rowena

Legend says that giving birds fizzy water can make them explode as gas builds up in their stomachs. But this is probably not correct - birds can burp it up. Bird's guts are somewhat different to humans, containing different chambers, but they do have an oesophagus which allows the bird's food to reach the crop (where a human's stomach would be). As bird's have no teeth they swallow food whole. It travels down to the crop ready for regurgitation to feed their young. It follows that, if they can regurgitate food, they should be able to regurgitate gas too. However it's not really natural for birds or other animals to drink fizzy water so best to stick to still water for your pets!

March 2003