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Questions and answers provided by Science Line's Dial-a-Scientist on 0345 600444

Q Could you tell by looking at a brain whether it was male or female?

A You couldn't be sure whether one brain was male or female, because there is so much variation between individuals. But there are average differences in external appearance between brains of the two sexes. The main difference is size - female brains are, on average, 10 per cent smaller than male brains. However, women's bodies are on average more than 10 per cent lighter than men's, so their brain weight is a higher percentage of the whole body.

Q What affects the rate of decay of fruit and vegetables?

A Decay occurs naturally as an extension of the ripening and maturing process. Fruit (especially bananas) produce a gas called ethene (C2H4) that aids ripening. This eventually ripens the fruit so much that it rots. Besides the ethene, bacteria, fungi and even fruit flies can speed up this process.

Q What did clothes moths eat before there were clothes?

A Clothes-moth larvae don't attack only woollen clothing. They also live in bird and mammal nests, and on bird and mammal corpses. They feed on a mixture of detritus and the fur or wool of the animal, plus fungal material. Clothes moths belong to a small group of closely-related species that have developed the ability to digest keratin - the protein that makes up fur, wool, hair, feathers, toenails and dead skin. Clothes moths were thriving long before we began storing their food in wardrobes.

Q Who first suggested that light had a finite velocity?

A Empedocles, in around 500BC, is the first documented person who assumed that light had a finite velocity. But he couldn't prove this, or measure it. The first person to measure the speed of light was a Dane, Ole Romer, in 1675.

Q What happens to plants grown in weightless conditions?

A Without gravity to determine in which direction the roots grow, plants have to rely on other factors. In general, the shoots keep growing in the direction the seed was planted, while the main root heads off in the other direction. But the root is also sensitive to moisture, and will grow towards it.

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