Vayu the gaseous envelope that surrounds the earth with sufficient gravity to maintain it. On earth, air protects life forms from harmful radiation and cosmic debris. It is a mixture of gases, the most abundant of which are nitrogen and oxygen. The composition of the air is not constant. The principal variable components are moisture and carbon dioxide. The gaseous constituents of the air are nitrogen 78.09%, oxygen 20.95%, argon 0.93%, carbon dioxide 0.03%, and minute traces of neon, helium, methane, krypton, hydrogen, xenon, and ozone. The ozone concentration is highly variable. Ozone is both produced and destroyed by absorption of ultraviolet and infrared radiation. Most of it is found at great altitudes.

It is important in meteorology largely because it absorbs ultraviolet and infrared radiation. Carbon dioxide in the air reduces the loss of heat by infrared radiation from the earth. The widespread burning of fossil fuels (eg coal and oil) increased the carbon dioxide content of the air by about 12% during the first half of the 20th century. This, in turn, caused an increase in the average temperature of the earth by 1.1'C during the same period.

the god of wind according to the Hindu mythology, often linked with Indra, sometimes as his equal, driving in the same chariot, yoked to a thousand steeds. Later, his chariot was depicted as drawn by four parrots. In the Vedas his status is not high like that of Indra or Surya, but he is hailed as the friend of the waters, the first-born, but where it is not recorded, although it is noted in the Purusasukta hymn that he has sprung from Purusa (the spirit primeval), an epithet of Visnu himself, the lord of the north-west quarter, and the father-in-law of Surya (Sun God). All these characteristics in one way or the other allude to his natural characteristics as an elemental force or wind.

In the Ramayana, Vayu, also known as Pavana (wind), is depicted as the father of Rama, as Dasarathi's great friend Hanuman. Anjani was the wife of Vayu. In the Mahabharata, Vayu plays an important role. He has been identified with Indra; he assisted Menaka; was invoked by Kunti; he granted her a son, Bhimasena; instructed Arjuna in the use of weapons, including the mighty Vayuvastra; granted two companions to Skanda; and visited Bhisma while he was dying on a bed of arrows on the Kuruksetra battlefield. While Arjuna was wielding the Vayuvastra, Vayu took away the Samsaptakas. He was not credited with the knowledge of the Brahmasiras and he learnt from the sage, Suparna, the creed of Narayana (Visnu).

Vayu's elemental characteristics were transformed into some of his names. He was also called Anila (breath), Sparsana (one who touches), Pavana Vaha (the wind carrier), Gandha Vaha (fragrance bearer), Lala Kantara (one who's costume is water), Sada Gata (perennial mover). In sculpture and iconography, Vayu is portrayed as blue in colour, with two or four hands. In the case of the latter, he stands with his front two hands showing the boon (varada) and protection (abhaya) poses (mudra) while in his back hands he carries a flag and a fan. The fan is apparently symbolic of the wind or breeze.

In the Buddhist pantheon, Vayu is one of the eight Dikpalas (Protectors of the Quarters) and has been assigned to the Vayu corner (north-west). Among the Jainas also Vayu is, as with the Buddhists, one of the Dikpalas, acknowledged by both the Svetambaras and the Digambaras. [Md Mahbub Murshed]