Ask Mr Brain . . . all will be explained

PUBLISHED : Wednesday, 04 October, 2000, 12:00am
UPDATED : Wednesday, 04 October, 2000, 12:00am

Why do we cry when we are sad?


Carmel Secondary School

Humans are a social species, and it is very important for an individual to express his feelings to fellow individuals.

Laughing and crying are expressions of very basic emotions - happiness/joy/contentment and pain/sadness/confusion/anger. An individual can get help and comfort by sharing his pain or sadness with another person.

Humans are very strongly oriented towards vision and sound, and most of our communication is based on vision and hearing - using facial expressions and other body movements together with speech and other sounds. Laughing and crying are both types of communication which use these forms of expression.

Babies laugh and cry without being taught how to do so. Even new- born babies use crying to show they are unhappy, long before they are capable of anything else. These actions simply evolved as the most adequate means for humans to express these basic emotions. Early humans most certainly laughed and cried, as did our ancestors and so do chimpanzees.

Why do wisdom teeth emerge later than our other teeth?

Third molars or wisdom teeth usually do not appear until the age of 17 because until then, there is not enough room in the jaw for them to grow. Sometimes, even in adult hood, there is not enough room for third molars, which is why many people have them removed.

Dentists usually recommend patients to remove their wisdom teeth because they do not serve any purpose and food gets caught in between easily.

Why does smoke from a cigarette rise in a smooth, vertical column before it suddenly scatters in a multitude of directions?

Smoke rises from a cigarette because it is hot and lighter than air. The stream is smooth and shaped like a column because it is laminar, and all the smoke particles travel in parallel.

The flow is laminar because the area where a cigarette burns is small, and the energy output that is driving the stream upward is only about one watt. Larger sources of smoke such as smokestacks or bonfires do not produce laminar streams.

The scattering of the smoke marks the transition of the flow from laminar to turbulent, and is caused by small disturbances to the smoke stream. Turbulent flow is characterised by random fluctuations of speed and direction.