According to Purushasukta, the vedic society was divided into four varna as Brahman, Kshatriya, Vaishyas and Shudras. This classification of society was based on the professions or occupations of the individuals.

In 1905, Rudrapatnam Shamashastri discovered the Arthashastra among a heap of manuscripts. He transcribed, edited and published the Sanskrit edition in 1909 and proceeded to translate it into English Publishing it in 1915.

Insolation is the solar radiation that reaches the Earth’s surface. It is measured by the amount of solar energy received per square centimeter per minute. Insolation affects temperature.

In 1954, the Hindi names Rajya Sabha and Lok Sabha were adopted by the Council of States and the House of People respectively.

Light year is a unit to measure the distance travelled by light in a vacuum in one Julian year. It was defined by the International Astronomical Union (IAU).

Rainbows appear in seven colours, because water droplets break sunlight into the seven colours of the spectrum. When light meets a water droplet, it is refracted at the boundary of air and water and enters the droplet, where the light is dispersed into the seven colours.The rainbow effect occurs, because the light is then reflected inside the droplet and finally refracted out again into the air.

The main source of naphthalene is coaltar. Its chemical structure is

Blood type become very important during blood transfusion. In the process of blood transfusion, a patient must receive a compatible blood type. If this does not happen, the RBCs will clump together making clots that can block the vessels and leads to death of a person.

Biological death occurs when brain cells start to die due to lack of oxygen. Biological death follows clinical death (when a person stops breathing). 4-6 minutes of oxygen deprivation can cause minor brain damage.

The weight of average adult human brain is 1200-1300 g. While in newborn babies it is 350-400 g. The brain is most complex and magnificent organ of human body. It controls our actions, body movement and sensitivity.