A visual story by Mavromatika.com
The majority of us human beings has spent their lifes on the "ground", only occasionally flying a few thousand meters above. If scientists hadn't figured it out a few centuries ago most of us probably wouldn't know that the Earth is a sphere. We have a good excuse : we're terrestrial mammals, we can't fly, and our understanding of our environment is severely limited by what we experience as individuals every day.
The chart below aims at giving you an idea of the size of the Earth's atmosphere relative to the solid part of the planet. I have included 4 layers to show the atmosphere, although there is another one called the Exosphere, where gazes are extremely rare and which slowly dissolves into outer space.
You might think that that's quite a lot of "air" above our heads. Breathable air however is only found in the layer closest to the ground called the Troposphere. On the chart below it is represented by the barely visible white line just above the brown crust.
Here's a close up of the chart above, where you can see the last solid layer of Earth - the Crust - and the four atmospheric layers to scale. Even with 10x magnification the Troposphere doesn't look very thick, does it ? To give you a little perspective on the other layers, the Stratosphere is where a few jet planes can fly - such as the Concorde or the U-2. The Mesosphere is where most meteors burn into shooting stars. And the Thermosphere is where the International Space Station is orbiting the Earth. At this height human survival requires a space suit.
Sources : Wikipedia
The troposphere is where most the Earth's "air" is. Did you know that 50% of the atmosphere's mass is below 5.6 km of altitude? This layer is really the only breathable air there is for us. And not even all the troposhere is safe for us. It is generally considered that above 8 000 meters is the "death zone" for humans, meaning that none can survive without artificial oxygen intake.
The last chart below shows the entire Troposphere's height, compared to heights we can relate to.
Sources : Wikipedia
As you can see in the chart above, there is very little breathable air above our heads. 8000 meters at most. That's less than 10 times the height of the tallest building on Earth. On land that would be about half the width of the Straits of Gibraltar, which is 14 kilometers wide.
Photo : Arkangel
Seeing this makes it a bit easier for us to understand why human activity has disturbed our atmosphere so much in recent decades. Now you have a better idea of where all the sighs go. They can't go very far at all. And neither can the gaz from our cars, planes and cargo ships.
They all end up in the same tiny air capsule all of us living creatures breath from every second.