How Will Life on Earth End?

Life is flexible. And the word ‘Apocalypse’ has become a very common term used these days. Whereas, we are in the phase of revelation of what is more important and which was hidden for a long period of time. It is basically the heavenly secrets that make sense of earthly realities according to Bart Ehrman. We, the humans make a choice on which path we choose, whether a flowery one amongst the other terrifying ones.

The first living organisms on Earth appeared 4 billion years ago, according to some scientists. Back then, our planet was still hit by giant space rocks. But anyway, life still exists. Throughout Earth's history, she's witnessed all kinds of catastrophes. Various apocalypse - from supernova explosions and asteroid strikes to massive volcanic eruptions and sudden climate change - have killed off innumerable life forms. And sometimes, these massive extinctions even wiped out most of the species on Earth. However, life goes on, new species keep emerging. It keeps constantly repeating itself.

It turns out that while humanity can be amazingly fragile, it's not easy to sterilize an entire planet. However, here are a few possible disastrous events that could cause all life on Earth to be destroyed forever. When a city-sized asteroid hit the Gulf of Mexico 66 million years ago, it was time for the extinction of dinosaurs, as well as most other species on Earth. And while our ancestors have not yet evolved, the impact is perhaps the most important event in human history. Without this asteroid strike, the dinosaurs could have continued to roam the path of Earth, leaving us with mammals still hidden in the dark. However, humans will not always be on the winning side in such random events. A future asteroid could easily wipe out everyone on Earth. Fortunately, this is unlikely to happen anytime soon according to this very article. Based on geological records of cosmic impacts, Earth is hit by a large asteroid about every 100 million years, according to NASA. However, impacts from smaller asteroids do happen all the time. There is even evidence that some people may have died from small meteorite impacts over the past thousands of years. 

But what is the probability that our planet will be hit by an asteroid large enough to wipe out all life on Earth? For example, what if the sun explodes just like any star exploding it could cause the end of the all humanity on the walks of Earth. Killing all life on Earth would require an impact that could literally boil the oceans. And only asteroids like Pallas and Vesta - the largest in the solar system - are large enough to do so. There is evidence that Infant Earth was attacked by a large carnivorous creature called Theia. But today, collisions of such large objects are extremely unlikely. To get a clearer picture of an Earth-changing cataclysm, we must look to the distant past. 

Approximately 2.5 billion years ago, a period known as the Great Oxidation Event gave us the breathable atmosphere on which we all now depend. An eruption of cyanobacteria, occasionally called blue-green algae, has filled our atmosphere with oxygen, creating a world where multicellular life forms can exist and organisms like Humans can finally breathe.

However, one of Earth's great deaths, an event 450 million years ago known as the Late Ordovician mass extinction, likely happened because the opposite happened. The planet experienced a sudden drop in oxygen levels that lasted for several million years.  During the Ordovician, the continents were a confused mass known as Gondwana. Most of life on Earth still lives in the ocean, but plants began to appear on Earth. Then, at the end of the Ordovician, severe climate change caused the supercontinent to be covered with glaciers. This global cooling alone is enough to start killing off species. 

But then a second mutation accelerates as the oxygen concentration plummets. Scientists are seeing evidence of this variation in seafloor samples collected around the world. Some researchers believe that glaciers have fundamentally altered the ocean's layers, which have unique temperatures and specific concentrations of elements like oxygen.

Whatever the cause, the end result is that more than 80 percent of life on Earth died in the Upper Ordovician mass extinction. So, this may have happened before, in a curious comparison to current life, climate change is reducing oxygen levels in our oceans, potentially killing marine life. GRBs (gamma-ray burst) are mysterious events that appear to be the most intense and energetic explosions in the universe, and astronomers suspect they are related to extremely large supernovas. However, we have yet to see a breakout close enough for us to fully understand what is happening. So far, GRBs have only been detected in other galaxies. 

If it happens in the Milky Way, as it may have in the past, it could cause a mass extinction on Earth. A GRB heading towards us might last for only about 10 seconds, but it could still destroy at least half of Earth's ozone layer in that short amount of time. As humans have known for the past few decades, even a small amount of ozone depletion is enough to erode our planet's natural sunscreen layer, causing many serious problems. Ozone removal on a large enough scale could wreak havoc on the food chain, killing off large numbers of species. A GRB would eliminate life forms in the upper oceans, which currently contribute significant amounts of oxygen to our atmosphere. And, it turns out that gamma rays also separate oxygen and nitrogen in the atmosphere. These gases are converted into nitrogen dioxide, commonly known as smog, which blocks the sun on heavily polluted cities. This smog covering the entire Earth will block out the sunshine and stimulate a global ice age. 

All of the devastating scenarios above, while certainly terrible for life, are only a fraction as bad as the eventual fate of Earth in the future. Gamma ray debris or not, in about a billion years, most life on Earth will eventually die from lack of oxygen.

The article is insightful in ways that says our oxygen-rich atmosphere is not a permanent feature of the planet. Instead, in about a billion years, solar activity will cause the amount of oxygen in the atmosphere to drop to levels before the big oxidation event. To determine this, there is a model combined with both climatic and biogeochemical to simulate what will happen to the atmosphere as the Sun ages and produces more energy. It is found that the Earth eventually reached a point where atmospheric carbon dioxide will break down. At this point, plants and oxygen-producing organisms that depend on photosynthesis will go extinct. Our planet will not have enough life forms to maintain the oxygen-rich atmosphere that humans and other animals need. Exactly when it starts and how long it takes - deoxygenation can take as little as 10,000 years - depends on a range of factors. But in the end, this cataclysm is inevitable for the planet. 

But humans still have a billion years to decide on what can be done to prevent the inevitable.