atmospheric friction
The atmosphere functions as a protective shield against the enormous energy impacts that small space objects can cause when colliding at very high speed against the surface of the planet.
Without an atmosphere, the collision speed of these objects would be the sum of their own inertial space speed (measured from our planet) plus the acceleration caused by the Earth's gravitation.
The kinetic energy of meteorites is transformed into heat by their friction in the air and from the surface we see a meteor "Meteor (astronomy)"), meteorite or also shooting star.
Friction is the macroscopic manifestation of a transfer of kinetic energy, or its transformation into another type of energy, by which one body "loses" movement, giving it to another, either by transferring part of its own movement or by transforming it into molecular movements (heat, sound vibration, etc.).
A body in free fall within the atmosphere can have decreasing velocity, since gravitational attraction produces uniformly accelerated motion only in a vacuum.
If a body begins to fall through the atmosphere, it accelerates until its weight is equal to the friction force produced by the movement through the air. At that moment it stops accelerating, and its speed begins to decrease as the atmosphere increases its density, causing a greater friction force.
It can slow down the rate of fall not only by the density of the atmosphere but also by the variation of the cross-sectional area, which increases friction. Aerial free fall acrobats can vary their fall speed by accelerating or decelerating: if they move upside down they accelerate until their weight balances, and if they open their arms and legs they decelerate.
Biogeochemical cycles
The atmosphere has great importance in biogeochemical cycles. The current composition of the atmosphere is due to the activity of the biosphere (photosynthesis), it controls the climate and the environment in which we live and encompasses two of the three essential elements (nitrogen and carbon); apart from oxygen.
Human activity is modifying its composition, such as the increase in carbon dioxide or methane, causing the greenhouse effect, or nitrogen oxide, causing acid rain.
Solar radiation filter
Harmful solar radiation, such as ultraviolet radiation, is almost 90% absorbed by the ozone layer in the stratosphere. The mutagenic activity of this radiation is very high, causing thymine dimers") that induce the appearance of melanoma in the skin. Without this filter, life outside the protection of water would not be possible.[3].
Greenhouse effect
Thanks to the atmosphere, the Earth does not have great thermal contrasts; due to the natural greenhouse effect, which is produced by all the gaseous components of the air, which absorb a large part of the infrared radiation reemitted by the Earth's surface; This heat is retained in the atmosphere instead of being lost in space thanks to two physical characteristics of the air: its compressibility, which compresses the air in contact with the Earth's surface by the own weight of the atmosphere, which, in turn, determines the greater absorption of heat from the air subjected to greater pressure and diathermancy, which means that the atmosphere allows solar radiation to pass through almost without heating (the direct absorption of heat from the sun's rays is very little), while it absorbs a large amount of dark heat ([4]) forwarded by the terrestrial and, above all, aquatic surface of our planet. This greenhouse effect plays a key role in the planet's mild average temperatures. Thus, taking into account the solar constant (calories that reach the Earth's surface per square centimeter per minute), the average temperature of the planet would be -27 °C, incompatible with life as we know it; On the other hand, its real value is about 15 °C precisely due to the greenhouse effect.[3].