Ask Mr Brain . . . all will be explained

PUBLISHED : Friday, 13 October, 2000, 12:00am
UPDATED : Friday, 13 October, 2000, 12:00am

Can a spider get trapped in another spider's web?

Spiders have been observed getting caught in others' webs and ending up as someone else's dinner.

Some spiders are expert hunters and prey on other spiders, but can travel easily on their webs.

These include the pirate spider and the comb-footed spiders.

Spiders avoid getting stuck to their own webs by walking on the non-sticky threads.

Some species have special adaptions to help them navigate their webs.

The orb-weavers, for example, have a third claw, which slides along and catches on the non-sticky lines that originate from the centre of the web.

What is antimatter?

All matter is made up of atoms which consist of a nucleus surrounded by negatively charged particles called electrons.

In 1930, Paul Dirac formulated a theory which led to a prediction of the existence of particles with the same mass as electrons but with an opposite, positive charge.

This particle, called the positron, is the opposite of the electron and the first example of antimatter.

Dirac's predictions applied not just to electrons, but also to all the fundamental constituents of atoms.

Each type of particle had to have a corresponding 'antiparticle' which was of the same mass, had similar properties but with electrical charges reversed.

Today, after laboratory experiments, the existence of antimatter partners for all matter particles has been well verified.

Any pair of matching particle and antiparticle can be produced when there is sufficient energy available.

But similarly, any time a particle meets its matching antiparticle, they destroy each other and both disappear.

In laboratory experiments, antimatter that is produced does not last long and quickly disappears again when it meets up with matching matter.

Today the question scientists are asking is: as the universe has more matter than antimatter, where has all the antimatter gone? Is there a parallel universe somewhere made completely of antimatter?

What is a hospice?

Like 'hospital', the word 'hospice' comes from the Latin term for 'hospitality'.

During the Middle Ages, hospices run by religious orders offered places of rest and meals to travellers and pilgrims.

Cicely Saunders, a British physician, adopted the term to describe practices and institutions that provide pain relief and comfort to dying patients and their families.

She said that the name suggested 'something between a hospital and a home, with the skills of one and the hospitality, warmth and time of the other'.