Earth’s Atmosphere: The Invisible Shield That Sustains Life

As we know, the Earth is surrounded by a layer of air. This layer extends up to about 560 kilometers and is composed mainly of gases — 78% nitrogen, 20% oxygen, and 2% other gases. We call this layer the atmosphere.

Since the atmosphere is made of gases, it might be expected to drift off into space. However, gravity keeps it bound to the Earth, allowing us to breathe. The atmosphere acts like a protective blanket. It comes into direct contact with space — and especially with the sun, filtering out much of the harmful ultraviolet radiation. As a result, sunlight reaches us in a gentle, life-sustaining way. Without this “blanket,” the Earth would become a scorched wasteland.

The atmosphere itself is made up of several layers. The lowest layer, the troposphere, is where we live, extending about 8–16 kilometers above the ground. Most weather phenomena such as rain, snow, hail, and clouds, occur here. Remarkably, the composition of gases in this layer is perfectly suited to support life. In higher layers, for example, gases like ozone are present in ways that would be harmful if they existed at ground level.

The Delicate Balance of Ozone

A thin protective shield surrounds the Earth: the ozone layer. It is not a uniform sheet but exists at varying altitudes and constantly changes from place to place and from day to day.

Ozone is a colorless gas with a sharp smell, constantly being created and destroyed in a cyclical reaction. As it performs its role of blocking harmful UV radiation, it breaks down, but there is no need to worry. The oxygen atoms released quickly recombine to form new ozone molecules, ready to continue the protection. This delicate balance is maintained in a remarkable cycle, perfectly suited to the needs of life on Earth.

When the Balance Is Disrupted

For many years, the amount of ozone remained relatively stable. However, in recent decades, human activity has significantly impacted this balance. In the early 1970s, scientists believed that high-altitude airplane emissions were the main threat to the ozone layer. Later, it became clear that the primary damage came from chemical compounds known as “freons.”

Freons, developed in 1928 for refrigeration, are highly stable and widely used in air conditioners and refrigerators. When leaks occur, these gases escape into the atmosphere. Over time, they rise and accumulate. In extremely cold regions like Antarctica, unique ice clouds form at high altitudes. Chemical reactions on the surface of these ice crystals break down the stable freon molecules, releasing chlorine and fluorine atoms, which rapidly destroy ozone.

This process led to the discovery of the “ozone hole” over Antarctica, where ozone levels dropped by about 40% during certain months. Today, there is global awareness of the importance of protecting the ozone layer and efforts are underway to restore it.

Breathing Life: The Oxygen Cycle

Oxygen makes up about 20% of the air we breathe, while nitrogen accounts for 78%, and the remaining 2% consists of other gases. In ancient times, people feared that oxygen might one day run out.

Eventually, scientists discovered a remarkable natural cycle: plants require large amounts of carbon dioxide to grow, while animals depend on oxygen. Plants absorb carbon dioxide released by animals and produce oxygen in return. This mutual exchange ensures that oxygen never runs out and that life continues.

The Importance of Perfect Balance

This balance must be carefully maintained. If oxygen levels were to increase significantly, fires would spread rapidly and uncontrollably, and even a small spark could trigger a global blaze. On the other hand, if oxygen levels decreased, breathing would become difficult, and life might not be sustainable.

For thousands of years, this balance has been preserved with extraordinary precision. Even a slight deviation could have had catastrophic consequences.

The Weight of Air — and a Hidden Balance

Take a deep breath — your lungs just filled with about four liters of air. Scientists have discovered that air has weight: one cubic meter of air weighs about 1.25 kilograms. Given the immense height of the atmosphere, this means that enormous pressure is constantly exerted on our bodies.

Why, then, don’t we feel crushed?

Because within our bodies, there is an internal pressure that perfectly counterbalances the external atmospheric pressure. This precise equilibrium allows us to live comfortably, without even sensing the immense forces around us.

Who ensured this perfect balance?