Ask Mr Brain...all will be explained

PUBLISHED : Monday, 08 March, 1999, 12:00am
UPDATED : Monday, 08 March, 1999, 12:00am

Why is the atom bomb so destructive? The weapon derives its explosive force from the release of atomic energy through the fission (splitting) of heavy nuclei.

The first atom bomb was produced by the United States and successfully tested on July 16, 1945.

Practical fissionable nuclei for atom bombs are the isotopes uranium 235 and plutonium 239 which are capable of undergoing a chain reaction.

If the mass of the fissionable material exceeds the critical mass, the chain reaction multiplies rapidly into an uncontrollable release of energy.

An atomic bomb explosion produces, in addition to the shock wave accompanying any explosion, intense neutron and gamma radiation, both of which are damaging to living tissue.

The area surrounding the site of the atomic explosion becomes contaminated with radioactive fission products.

Some radioactive products are borne into the upper atmosphere as dust or gas and may subsequently be deposited as radioactive fallout far from the site of the nuclear explosion.

How do animals stay clean? Animals in the wild do not have the luxury of a nice, warm bath. Believe it or not, zebras roll around in dirt to get clean! It's old skin and bugs they need to clean off.

Chimps have a 'friend' pick out the bugs and dirt from their fur.

Cats use their tongues to lick themselves clean, while elephants wallow in dust - or water.

Rhinos depend on the help of a special bird which feeds on the bugs on its hide.

What is a black hole? A star in the last phases of gravitational collapse is often referred to as a 'black hole'.

Gravitational collapse may begin when a star has depleted its steady sources of nuclear energy and can no longer produce the expansive force, which is a result of normal gas pressure, that supports the star against the compressive force of its own gravitation.

When a star (or supernova remnant) shrinks below a certain size determined by its mass, the extreme curvature of space seals off contact with the outside world.

Because light and other forms of energy and matter are permanently trapped inside the black holes, it can never be observed directly. But it can be detected by its effects on external objects.

How does your cut stop bleeding? As soon as you cut yourself, parts of your blood called platelets begin to gather. They stick to each other and to the edges of your cut, forming a thin cover over it.

If the cut is big, the platelets may need extra help to stop the bleeding. Along comes fibrin - another special part of your blood - to the rescue.

It weaves a criss-crossing tangle of long, sticky strands over the cut. Then the strands dry out to form a scab. The scab acts like a bandage and allows new skin to grow underneath. So do not pick at it.