Modern allopaths do not consider kajal safe. All the same it has been used in India for at least 2,500 years and no harm has been reported.Q Why is the human blood classified into groups? Karthik Seshadri, PuneGrouping of blood is a classification of blood vessels based on properties of the red blood cells, as determined by the antigens in them. They are A, B, AB and O. Karl Landstenner, a biologist, discovered these blood groups in 1900. The four blood types differ because of substances called antigens, that are found in the serum. If the blood of the donor is not of the same type as that of the receiver, the blood cells in the receiver's blood would get clumped together by serum from the other person. Besides this, the human blood also may or may not have a factor called Rhesus factor. If we have this factor, the blood is considered RH positive. If the blood does not have this factor the blood is called RH negative.People who have the blood group O are considered to be universal donors. Theserum of their blood will not make the blood cells of the receiver's blood clump. Those who have the blood group AB are universal receivers because the blood cells in their blood will not get clumped together whether they receive blood of Group A or B.Q How is a volcanic mountain formed? Manas R Marathe, PuneMost of the earth's volcanoes are based on the boundary between two plates of the earth - the continental crust (Sial) and the oceanic crust (Cima). The molten lava erupts where the crust is weak. It is a general misconception that volcanoes are seen in mountainous regions alone. In fact, it's the other way round. Volcanoes create mountains.Q Why do ants bump into each other? S Prashant, MumbaiAnts are social animals. The worker ants inform each other about the source of food or about the possible dangers. Soldier ants exhort other soldier ants to fight. The ants produce special chemicals called pheromones, which help them carry on such communication. They bump into each other for the exchange of information.Q Why are igloos always semi-circular in shape?The shape of the igloo is semicircular because the shape can bear the impact of snow blizzards or other small objects that come hurling towards it. The sun, the moon and the stars are also spherical for the same reason. It is the most stable shape. Eskimos hardly live in igloos any longer though.Q How is a whirlpool caused? Garima Chauhan, BarodaInstead of flowing in a single direction, sometimes, water spins around rapidly and with great force. This is called a whirlpool. It may occur when a water current strikes a bank and the passage for water is narrow at that point. Sometimes a whirlpool is produced by the interaction of the rising and falling tide in an ocean. It may also be caused by the action of strong wind or presence of rocks in the way of an oceanic current.Q Who was the first woman to go around the earth in a spacecraft? K Vishwant, UlhasnagarA russian cosmonaut, Valentina Tereshkova, was the first woman to go into space in 1963.
