On this Wikipedia the language links are at the top of the page across from the article air fryer tofu. Air is a mixture of many gases and tiny dust particles. It is the clear gas in which living things live and breathe.

It has an indefinite shape and volume. Animals live and need to breathe the oxygen in the atmosphere. In breathing, the lungs put oxygen into the blood, and send back carbon dioxide to the air. Plants need the carbon dioxide in the air to live. They give off the oxygen that we breathe. Since early times, air has been used to create technology.

Ships moved with sails and windmills used the mechanical motion of air. Aircraft use propellers to move air over a wing, which allows them to fly. Air is invisible: it cannot be seen by the eye, though a shimmering in hot air can be seen. Earth’s atmosphere has changed much since its formation. At first it was mainly a hydrogen atmosphere. It has changed dramatically on several occasions—for example, the Great Oxygenation Event 2. 4 billion years ago, greatly increased oxygen in the atmosphere from practically no oxygen to levels closer to present day.

Outgassing from volcanism, supplemented by gases produced during the late heavy bombardment of Earth by huge asteroids, produced the next atmosphere, consisting largely of nitrogen plus carbon dioxide and inert gases. The constant re-arrangement of continents by plate tectonics influences the long-term evolution of the atmosphere. Carbon dioxide was transferred to and from large continental carbonate stores. Free oxygen did not exist in the atmosphere until about 2. Cold Spring Harbor Perspectives in Biology.