Science: When a banana gets fruity

Technoquest

Questions for this column may be submitted by e-mail to sci.net@campus.bt.com

Why do bananas change from green to yellow when they ripen?

During the ripening process, fruit produces ethene, a gas which permeates the cells of the edible parts. That makes the fibres in the fruit break down so the fruit goes soft. It also converts the starch to sugar, making the fruit sweet, and destroys the chemical that makes the fruit green - chlorophyll - so that other colours can come out. In the banana's case, that colour is yellow. By controlling the gene that switches on ethene production, scientists can dictate how fast, or even if, fruits ripen.

What is the smallest bone in the body?

The stirrup bone, one of the three little bones in the middle ear, is 2.6-3.4mm long and weighs 2.0-4.3mg. It is about the size of a grain of rice.

Can members of the public name stars?

A number of organisations around the world claim to name stars on your behalf. However, none is officially recognised by the International Astronomical Union, hence their naming has no scientific weight.

Apart from the few dozen bright stars named by the ancients, stars are always designated by some alphanumeric system involving their placement in the sky, such as their ordering by position in a zone of declination, by brightness (or by variability of brightness) in a constellation, or simply by their coordinates.

There is one completely valid way to get heavenly things named after you - discover them. Comets and "minor planets" (asteroids) are always named by those who find them - hence the Shoemaker-Levy and Hale-Bopp comets - so get your telescope out and get hunting. The only time members of the public had the chance to name astronomical objects was for features (especially craters) on Venus: all are named after women, so people were asked to nominate their favourite female characters from history or the present day.

Do wombats have square faeces, and which way do their pouches open?

Wombats do, indeed, produce cuboid faecal pellets. They are solitary creatures which live in burrows in Australia, and come out at night to feed mainly on grasses. They mark their territory with splashes of urine - and their strangely shaped faecal pellets. Their pouches, along with those of other marsupials that crawl along the ground, open in the opposite direction to that of a kangaroo: if the wombat was to stand on its back legs, the pouch would open downwards.

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