WHAT IS ACID RAIN...?

Do you guys know what is acid rain....?

Acid rain is rain that has a larger amount of acid in it than what is normal. Acid rain is caused by smoke and gases that are given off by factories, and vehicles that run on fossil fuels. When these fuels are burned to produce energy, the sulphur that is present in the fuel combines with oxygen and becomes sulphur dioxide. Some of the nitrogen in the air becomes nitrogen oxide. These pollutants go into the atmosphere, and become acid. Sulphur dioxide and nitrogen oxide are also produced when coal is burnt for fuel. Acid rain destroys trees, harms wildlife and eats away the stonework in buildings. It also gives us asthma  and coughs!

IS THE EARTH A PERFECT SPHERE...?

A person who thinks about the shape of Earth may have a doubt that is the Earth a perfect sphere or not...?

If you look around, the Earth looks flat. Even before the middle ages, people did think it was flat. The flat Earth concept persisted till about 300 years ago. In fact, people used to think that if they sailed too far in one direction, they would fall off the edge of the Earth! Pythagoras was the first person to talk about the Earth being spherical. A practical demonstration on Earth's sphericity was achieved by Ferdinand Magellan's  expedition's circumnavigation. It was Sir Isaac Newton, who first claimed that the Earth is not spherical, but 'oval'. Today, we know that the Earth is not a perfect sphere. It is slightly flattened at the poles, and bulges at the Equator.