Ask Uncle Pai

Coal is formed as a result of the decomposition of vegetation: leaves and trunks of trees, under immense pressure at great depths, below the earth’s surface.

Why do floods generally occur along the banks of rivers flowing down from the Himalayas?

Jay R Shah, Dongersi Road, Mumbai

Human population has been increasing over the decades. To meet, the increasing needs of the massive population, trees are being cut and uprooted in large numbers. Laws have been passed to conserve our forests and trees. But many of these laws are ineffective because of the rampant corruption in our country.

Trees help preserve the soil. In the absence of enough trees on the banks of rivers, soil erosion takes place and the level of the silt in the river basin rises. This gives rise to the possibility of floods. More and more people have been polluting rivers not only by washing their clothes and utensils in them, but also throwing all kinds of dirt, thus cluttering up the river basins.

Rivers that flow down the Himalayas have a long journey before reaching the Bay of Bengal. As a result, the dirt collected is substantial. A major source of water for Himalayan rivers is the snow on mountain peaks, which melts in summer. This is also one of the reasons for floods, though far less important than the soil erosion that occurs.

Do people living in high-rise buildings get affected in any way?

Deepak, Mumbai

Recently, when I addressed youngsters of a residential society, I was asked whether the force of gravity on a person, living on the 30th floor, is lower than on the one living on the ground floor. Of course, the difference in the gravitational force is very marginal and is therefore of no consequence. However, recent studies have revealed that people living in the upper floors of high-rise buildings could be affected by vibrations not only in their building but by those in buildings close to their residence too. These sounds, referred to as infra sounds, might not be audible. Yet they can be disturbing and could affect the performance of those subjected to these vibrations (and sounds). My friend’s mother has been operated on for breast cancer. Does heredity play any role as far as cancer is concerned? What are the chance of my friend getting cancer? At what age should my friend go for a check-up?

Nirali Shah, Borivli (west)

Cancer of the breast is the most common type of cancer in women. Medical experts say that a family history of breast cancer is often found among patients of breast cancer. People who have a fat rich diet, stand the risk of breast cancer. But women below thirty years rarely suffer from it. Therefore, stop worrying.