Introduction

The atmosphere is not some distant, abstract layer — it is the very envelope of air we live inside, and we depend on it every few seconds. That dependence is the starting point for studying what the atmosphere is made of and how it is arranged. This section lays the groundwork by asking a simple question: can a person live without air?

We eat food two or three times a day and drink water more frequently, but we breathe every few seconds. Air is essential to the survival of all organisms. Some organisms, like humans, may survive for some time without food and water, but cannot survive even a few minutes without breathing air. That alone shows why we should understand the atmosphere in greater detail.

The atmosphere is a mixture of different gases, and it envelopes the earth all round. It contains life-giving gases — oxygen for humans and animals, and carbon dioxide for plants. The air is an integral part of the earth's mass, and 99 per cent of the total mass of the atmosphere is confined to a height of 32 km from the earth's surface. The air is colourless and odourless, and can be felt only when it blows as wind.

The section also poses a thought-provoking question: what would happen to us in the absence of ozone in the atmosphere? This sets up the importance of the atmosphere's composition and structure, which the chapter goes on to examine in detail.