All around you, in the air and the ground, is the most common element on Earth: Oxygen.
As you are certainly well aware, Oxygen is required for life on Earth as we know it. But you might realize that the Earth didn’t always have oxygen in its atmosphere.
Oxygen has been responsible for everything from the rise of multicellular life to the space program.
Learn more about the element oxygen, what it is, and how it came to be in our atmosphere on this episode of Everything Everywhere Daily.
Before I get too deep into the discussion of oxygen, I should probably explain what oxygen is and what makes it so special.
Oxygen is the eighth element on the periodic table. It also has the distinction of being the third most abundant element in the universe after hydrogen and helium and the most abundant element in and on the Earth. Oxygen is almost twice as abundant as silicon in the Earth’s makeup.
What makes Oxygen so special, and what you need to understand to make sense of the rest of the discussion on oxygen, is that it is very reactive.
Oxygen’s outer electron shell has six electrons out of a possible eight. Atoms really want to have full electron shells. They can do this by bonding with other atoms and using their electrons to fill up that outer shell.
Oxygen is one of the most reactive elements on the periodic table. When oxygen reacts with something, it is called oxidization. (Actually, oxidization has a more general meaning as well. If an atom gives up electrons, it is being oxidized, and if it gains electrons, it is being reduced. In a strict chemical sense, you don’t need oxygen in an oxidizing reaction, but the name comes from reactions using oxygen because it was the first known oxidizing reagent….and this episode is about oxygen)
You are probably familiar with many forms of oxidization. Rust is a form of oxidization. Burning and combustion are forms of oxidization. If you’ve ever seen an apple or a piece of fruit turn brown, that is because it is reacting with oxygen.
So Oxygen, in addition to being responsible for life as we know it, oxygen is also responsible for decay and destruction.
Oxygen in the atmosphere is almost never in its atomic form. Instead, it tends to bind to itself to form oxygen molecules. This is usually in the form of O2, which is just two oxygen atoms bound together, or sometimes O3, which consists of three oxygen atoms and is called ozone.
If we go back far enough, there was a time when the Earth’s atmosphere had almost no oxygen in it. The atmosphere mainly consisted of gases such as methane (CH4), ammonia (NH3), and water vapor (H2O). The microbial life forms on the planet at this time were all anaerobic, meaning they didn’t use oxygen.
Then, about 2.4 billion years ago, something happened.
A form of life developed known as cyanobacteria, also known as blue-green algae, which could conduct photosynthesis. These cyanobacteria consumed carbon dioxide and gave off oxygen as a byproduct.
This began what is known as the Great Oxidation Event.
The addition of oxygen to the atmosphere didn’t really do much at first. Given how reactive oxygen is, it would bind itself to rocks and other organic matter, quickly removing it from the air.
However, over time, as cyanobacteria spread and the rocks around the world became fully oxidized, oxygen began to accumulate.
This was not good news for the microbes, which were adapted to a reducing atmosphere with methane and ammonia. This is why the Great Oxidization Event has also been called the Oxygen Catastrophe and the Oxygen Holocaust. It resulted in the death of most of the lifeforms that existed on the planet at the time.
Over the course of several hundred million years, more and more oxygen accumulated in the atmosphere, which resulted in more life forms that were adapted to oxygen.
Aerobic metabolism, which uses oxygen, is more efficient at the production of adenosine triphosphate ATP, which is the primary molecule used for energy in cells.
The Great Oxidization Event may have resulted in the creation of eukaryotes, which are cells that have a nucleus and are the basis of multicellular life.
Oxygen in the atmosphere kept increasing over a period of hundreds of millions of years. Today, the percentage of oxygen in the atmosphere is approximately 21%.
However, there was a period when oxygen levels reached 35% at the end of the Carboniferous period, which was about 300 million years ago.
A world with an atmosphere with 35% oxygen would be one very different than the world we live in. For starters, you could probably breathe in that environment for a least a little while. However, over an extended period, you would probably suffer from oxygen toxicity, a condition normally only encountered by deep sea divers.
This oxygen-rich world allowed for the development of enormous insects. Insects don’t have lungs for gas exchange. They have to rely on the direct exchange of gas through their bodies.
When oxygen levels increased, it allowed for more oxygen to be consumed by insects, which resulted in larger body types.
The largest insect that ever existed lived in such a high-oxygen environment. It was a dragonfly-looking insect with a wing span of 27 inches or 68.5 centimeters.
A 35% oxygen atmosphere also would have seen an enormous amount of fires. Combustion takes place much more easily in an oxygen-rich environment. These fires may have resulted in the rich layer of carbon in the ground from which the carboniferous period gets its name.
Oxygen continues to exist in the Earth’s atmosphere because of plant life, which is continually creating it.
If all the living things in the world were to disappear instantly, the amount of oxygen in the atmosphere would start to decrease. Organic matter would decay, pulling oxygen out of the air, and geologic processes would remove oxygen as well.
The amount of oxygen in the atmosphere would be down to just 5% within 1.5 million years and down to half a percent within two million years.
This is why astronomers look for signatures of oxygen as a potential biomarker for life on other planets. Any planet with an oxygen-rich atmosphere would have to have some means of replenishing the oxygen as, over time, all of it would eventually react with rock and other chemicals.
While oxygen has had a pivotal role in the creation of life on Earth, humans had no clue that it even existed for thousands of years.
There were philosophers who believed that there was something in the air which was responsible for life. The 17th-century Polish scientist Michael Sendivogius called it “cibus vitae,” or the food of life, and went so far as to identify it as the gas that was given off when potassium nitrate was heated.
That gas was oxygen.
Over a century later, in 1772, the Swedish chemist Carl Wilhelm Scheele created a substance he called “fire air” by heating various substances such as mercury oxide. It was the only substance he could find that would support combustion rather than extinguish it.
In 1774, English scientist Joseph Priestly discovered what he called dephlogisticated air.
However, it was the French chemist Antoine Lavoisier who figured out that the substance that Priestly and Sheele discovered was, in fact, a new element. He dubbed the new element oxygen, which came from the Greek words oxys, which means acid, and gens, which means the creation of.
Lavoisier mistakenly thought that oxygen was part of every acid.
In 1877, French chemist Raoul Pierre Pictet liquefied oxygen for the first time, even though it was only a few drops. Oxygen doesn’t become a liquid until it reaches a temperature of ?182 °C, ??297 °F.
In 1891, the Scottish chemist James Dewar managed to create enough liquid.
It turned out that liquid oxygen exhibited properties that weren’t expected, given how gaseous oxygen behaves.
For starters, liquid oxygen isn’t colorless. It actually has a light blue color. You can see videos online of experiments using liquid oxygen where you can clearly see its blueish hue.
The other amazing property of liquid oxygen, and this one no one expected, is that it is paramagnetic. It doesn’t act as a magnet per se, but external magnets can influence it.
Liquid oxygen turned out to be extremely useful.
For starters, you can have a lot more oxygen in liquid form than you can in gaseous form. Oxygen has an expansion ratio of 861: 1. Meaning that liquid oxygen will have 861 times more oxygen than gas at standard temperature and pressure in the same volume.
There are many applications where you want to have pure oxygen.
One of the biggest is in rockets and spaceflight. Rockets require combustion, and combustion requires oxygen. However, the higher up a rocket goes, the less oxygen there is, and when you are in space, there is no oxygen at all.
The solution is liquid oxygen. Liquid oxygen plus fuel, such as liquid hydrogen, kerosene, or methane, can provide combustion and thrust even in a total vacuum.
Pretty much every liquid-fueled rocket, including the Saturn V, used in the Apollo program and the space shuttle, has used liquid oxygen.
Liquid oxygen can also be used for industrial purposes, mostly just as a convenient storage and transportation for pure oxygen.
Pure oxygen can aid in combustion when something needs to burn hotter or more efficiently than just using oxygen in the air.
The biggest commercial use of oxygen is in producing iron and steel. A jet of pure oxygen is injected into molten iron, which removes impurities.
Another big user of liquid oxygen is the chemical industry, where pure oxygen is used to make various chemical compounds that include oxygen.
Another big use of pure oxygen is in cutting and welding applications. A stream of pure oxygen can create a hotter flame, making it possible to cut and weld metals.
The application that most people are familiar with is the medical use of oxygen.
Supplemental oxygen is often given to people who have pulmonary or circulatory diseases where not enough oxygen is able to get to the body. By breathing oxygen with a higher partial pressure than the atmosphere, more oxygen is able to get into the blood.
High-pressure oxygen treatments are used on people who have suffered from decompression sickness or carbon monoxide poisoning. By putting them in an environment with more oxygen, it is possible to displace the carbon monoxide that has bound to the oxygen receptors in hemoglobin, the molecule that transports oxygen in blood.
In the case of decompression sickness, high-pressure oxygen can help redissolve nitrogen bubbles in the body, which occurs, usually when SCUBA divers ascend too rapidly.
Supplemental oxygen is often used by mountain climbers who climb peaks like Mount Everest, where there is very little oxygen at the top. Likewise, pilots in military aircraft will often use supplemental oxygen when flying at extremely high altitudes.
In commercial aircraft, during an emergency, oxygen masks will drop to allow people to breathe during a loss of pressure at high altitudes. The oxygen in these systems usually doesn’t come from oxygen canisters but rather is produced on demand via a chemical oxygen generator.
This will usually consist of iron filings, which are mixed with sodium chlorate to produce oxygen. By using a chemical oxygen production system, it isn’t necessary to have high-pressure tanks on board a plane, and you don’t have to worry about the tanks leaking.
One place you have probably seen oxygen being used is on the sidelines of sporting events. Believe it or not, there is actually very little evidence to indicate that this does anything beyond a placebo effect, as there is a limit to the amount of oxygen that the hemoglobin in your blood can support.
Breathing oxygen can produce a euphoric feeling, which is probably the reason why people think it works.
It is also the reason why you sometimes might see oxygen bars. I’ve seen these in several airports around the world. You literally sit down to breathe oxygen out of a tube for several minutes. It can produce a temporary euphoric feeling, but it doesn’t really do anything beyond that.
Oxygen is everywhere, and most of the major lifeforms in the world depend on it. We use it for industrial purposes and in medicine, and one day, its presence might even let us know there is life somewhere else in the universe.
That isn’t too bad for a gas that didn’t even exist in our atmosphere 2.5 billion years ago.
The Executive Producer of Everything Everywhere Daily is Charles Daniel.
The associate producers are Thor Thomsen and Peter Bennett.
Today’s review comes from listener bzawi over on Apple Podcasts in the United States. They write:
Gary is my fishing buddy!
I’ve recently become a completionist club member after listening to 1000+ episodes…mostly while fishing. Thank you for being such a good companion. Gary’s voice is perfect at 1.25x, and the topics are interesting and informative. Thank you from another proud Wisconsinite and Packer fan. My all-time favorite is The Peshtigo Fire episode. I thought I knew all about it, but I learned a lot. Keep up the great work!
Thanks, bzawi! I am happy to welcome you to the Wisconsin chapter of the Completionist Club. The Wisconsin chapter is actually a supper club that servers brandy old fashions and, of course, fish every Friday. You can have your choice of perch or walleye.
Remember, if you leave a review or send me a boostagram, you too can have it read on the show.