Will the oxygen on the earth run out in the future?
Among them, oxygen is an essential component of most life on earth. Take us humans for example. We breathe air all the time and get oxygen from the air for chemical reactions in our bodies.
Sometimes I wonder why life on earth needs oxygen. This makes the existence of life highly dependent on the atmospheric environment of this planet, and also seriously hinders the pace of human beings going to other planets;
Because outer space, including many planets outside, does not have the atmospheric conditions like the earth, we have to put on heavy spacesuits and carry oxygen bottles to survive in the world outside the earth.
In fact, the existence of life does not necessarily need oxygen, but the existence of a large number of oxygen on the earth has chosen the life form on the earth today.
Because the atmospheric environment of our earth is not always like today. At the beginning of the earth's birth, it was a fiery fireball, with volcanic eruptions and meteorite impacts. The surface of the earth was covered with flowing molten magma.
At that time, the earth's atmosphere was basically carbon dioxide, carbon monoxide, nitrogen, methane, ammonia, hydrogen sulfide, water vapor, etc., which are toxic and harmful to life on earth now. At that time, there was no oxygen in the earth's atmosphere.
Because the free oxygen at this time is basically fixed in molecules in the form of compounds, with the cooling of the earth, the formation of oceans, the reduction of asteroid impact and volcanic eruption, the release of these harmful gases gradually decreases until it stops releasing and tends to be stable.
It is this kind of earth that life was born in the ocean, but life at that time was just some simple single-celled life. They don't need oxygen to survive, they just need to get energy from sunlight and then use carbon dioxide, or methane, ammonia and so on. By synthesizing these substances into organic substances for their own survival, they will release oxygen.
This kind of life, this kind of atmospheric environment, has lasted for about 2 billion years since the birth of the earth. Then there was a big explosion of single-cell life called cyanobacteria on the earth, which consumed a lot of carbon dioxide and methane in the air and released oxygen continuously.
It triggered the famous "Great Oxidation Event" in the history of the earth. In just a few hundred thousand years, oxygen has increased rapidly, and carbon in the atmosphere has been fixed in organic matter and deposited on the seabed with geology. This change also led to the death of most anaerobic bacteria on the earth at that time.
But with the rise of aerobic bacteria and the emergence of multicellular life, the prosperity of aerobic life continues to this day, including us, so it is not human beings who choose oxygen, but the earth environment that chooses and creates human beings.
In 20 18, scientists discovered a large number of crystalline salt rocks in the strata of northwest Russia, which can be traced back to about 2 billion years ago. They are crystalline salts left by seawater evaporation in this area, and there are a lot of sulfates, which are formed by sulfur and oxygen.
This discovery proves that there was a great oxidation event on the earth, and it also proves that the event and speed of the great oxidation event are consistent with previous speculation.
Today, life on earth is just the opposite. We use oxygen to re-fix the oxygen in the atmosphere in compounds through various forms of oxidation reactions, such as various animals, bacteria, including human life activities.
More importantly, since the industrial age, a large number of organic fuels once buried underground have been dug up and burned, which not only consumes oxygen, but also releases a lot of carbon dioxide into the atmosphere.
In just 200 years, we have caused many climate problems. At present, the concentration of carbon dioxide in the atmosphere is 4 12.48ppm, and the annual growth rate is about 2. 1 ppm/ year, which is much higher than 280ppm before the industrial age.
Although there are still plants that consume carbon dioxide to produce oxygen on the earth, with the expansion of human life circle and the cutting down of plants, the current consumption of carbon dioxide by plants is far behind the output of human beings.
Compared with the "Great Oxidation Event" that happened 2.4 billion years ago, human beings are now making the earth experience a "deoxygenation event". Although the speed is very slow, the greenhouse effect caused by carbon dioxide emissions is a chain reaction.
The rising temperature of the earth will accelerate the melting of ice and snow at the poles, resulting in the release of methane sealed in the polar regions. The rising temperature of the ocean will also decompose methane hydrate deposited on the seabed and release methane, which has a greenhouse effect of 25 times that of carbon dioxide.
It will seriously raise the temperature of the earth's atmosphere, trigger more droughts and forest fires, destroy vegetation and release a lot of carbon dioxide.
If human beings continue to develop according to the present situation, the earth will be completely deprived of oxygen in just a few hundred thousand years, and then the wind and water will turn around and anaerobic bacteria will rule again.
If human beings develop clean energy, stop emitting greenhouse gases and control the rising trend of atmospheric temperature from now on, can they save themselves?
No, the earth will spontaneously experience a "deoxygenation event" in the future, and the increase of solar luminosity will cause this effect. As the sun grows older, its burning will not slow down. The older the sun, the more violent and rapid it burns.
With the increase of luminosity, the visible solar spectrum will change, and the whole will shift blue, that is, the red light in the sun will disappear, and more blue light and ultraviolet light will be added.
Even if ultraviolet rays don't kill plants, the change of solar visible spectrum will directly affect the photosynthesis of plants and reduce the efficiency of oxygen production by plants. Coupled with the rising temperature of the earth, it will also lead to the runaway greenhouse effect.
So there is bound to be a deoxidation event on the earth, which will happen about 654.38+0 billion years later.
At that time, the temperature of the earth will evaporate all the liquid water, and the earth will return to the high-temperature world full of poisonous gas.
This study on the future changes of oxygen in the earth's atmosphere was published in the journal Natural Geology. Research shows that oxygen is not an inherent and unchangeable feature of a livable planet. For the earth, the existence of oxygen in the atmosphere only accounts for 1/3 of the earth's life.
In the remaining time, there is no oxygen in the earth's atmosphere, but there is still life, so this can lead us to find alien life, and it doesn't have to be the same as the earth's atmospheric environment.
This study also shows once again that life on earth is only the product of the present environment of the earth, and human beings are all passers-by. The earth may not always be the home of mankind, which is what Hawking is worried about, and this is also the reason why mankind is looking for another home now.