Today’s [Triviatime](https://triviatime.app/) had a Q which asked what % of the earth’s air is made of Oxygen. The answer was 21% but this only left me with more questions!
How??? What else is there and what are the implications of those elements/things being literally everywhere in the air. Fellow laymen eggheads, please add to this list of thoughts you have about this which need to be addressed:
– How does our breathing filter the other stuff out?
– What actually is air if it’s made up of so many different things, I thought air basically = oxygen?
– How steady is this 21% level? Can this change overtime, is that dangerous, and if so how?
– Etc
In: 0
Air is made almost entirely of Nitrogen, an inert gas. Then oxygen, then water vapor, then carbon dioxide, then argon and other trace elements.
Your body only makes use of the oxygen. The rest of it you just breathe back out.
The air is mostly nitrogen gas, then oxygen, then small amounts of other gases.
It’s not dangerous for us. We evolved in this environment. We simply breathe the nitrogen gas out. Nitrogen is a very stable molecule meaning it doesn’t really react with stuff easily. So it just goes in and then out.
If the air was pure oxygen that wouldn’t necessarily be good. Things would be even more flammable since oxygen is an ingredient in combustion. Like rather than a small burn, something might explode. Also funny enough, you can be poisoned by too much oxygen. Your lungs don’t really like the excess oxygen when it’s a lot.
The percentage of oxygen does fluctuate, but that’s on timescales of hundreds of millions of years. Fun fact, the reason some prehistoric insects could grow so much larger than insects today is because their atmosphere was more oxygen-rich than ours.
Oxygen is the second-largest component of Earth’s air. Almost all of the rest is nitrogen, with some water vapor and small amounts of argon, carbon dioxide, and other gases.
There isn’t much effect from that nitrogen, though. Nitrogen in the air (that is, the molecule N_2 made of two nitrogen atoms bonded together) has an exceptionally strong bond that is almost impossible to break apart, which means that nitrogen doesn’t really react chemically with much of anything. You don’t ‘filter it out’ – your blood contains some dissolved nitrogen – but your body also doesn’t actively pull nitrogen from the air the way it does oxygen (that’s the point of the hemoglobin in your blood).
The level is pretty steady the vast majority of the time. It might dip a little indoors, but not much; by the time you’ve consumed enough oxygen to meaningfully change that number you’ve *added* enough carbon dioxide to feel very sick. You can tolerate a wide range of oxygen levels anyway, though. For example, if you go up to high altitude, you’re effectively breathing something like 2/3 of the normal oxygen level because the air is much thinner.
The rest of the air is made up of nitrogen (78%) and other gases, including argon, carbon dioxide, and water vapor.
> How does our breathing filter the other stuff out?
by not reacting with it, the biggest mass of out atmosphere is nitrogen, an inert gas which you just breathe back out.
> What actually is air if it’s made up of so many different things, I thought air basically = oxygen?
“air” would effectively be atmosphere so the mix of gases + pressure.
> How steady is this 21% level? Can this change overtime, is that dangerous, and if so how?
its’s as steady as it gets outside of a extinction level events.
fun fact, an Atmosphere with too much oxygen is toxic(100% oxygen would just straight up kill you as the lung tissue doesnt like htis type of enviroment). too much is also bad in general since oxygen is a very reactive fuel source for combustion.
Funny story: not only is the air a (basically) Nitrogen/Oxygen mix, but humanity would not survive if it were very far off from the percentages given. See…humans need oxygen and don’t really do much with the Nitrogen, but nitrogen is required for plant health and is part of a support cycle involving CO2->O2 conversion. Without the Nitrogen that basically just takes up space (for animals), plant life would die out and there would be no mechanism for converting CO2 back into breathable oxygen. The balance of nature is an amazing thing.
Most of the air you breathe is nitrogen- about 80%. Nitrogen is inert, and your body doesn’t care about its molecular form. The molecular form is so stable that the only way for you to get the nitrogen your body needs is to eat it, and the way it got into your food is that many plants have symbiotic bacteria in their roots that convert molecular nitrogen into bioavailable nitrogen. When you take in a lung full of air, molecular oxygen is taken up by your red blood cells while the molecular nitrogen is more happy to remain as a gas.
The amount of oxygen in the atmosphere does change over time, but usually over geologic time periods, and it’s always much less than nitrogen. Hundreds of millions of years ago the atmospheric oxygen concentration was closer to 30%, and one of the ways we know this is from fossils of the enormous insects that lived back then- dragonflies with a 60 cm wingspan, or millipedes 2 meters long.
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