This is part two of a series (Part 1) (Part 3) (Part 4) (Part 5) covering several ways that humanity’s time on Earth could conceivably come to an end. The study of the apocalypse, known as eschatology has been a pervasive force in religion, science, and popular culture since the development of the first cultures on Earth. Some of the theories about the end of days are more plausible than others, but all are thought-provoking nonetheless. In Part Two, I describe a few of the most likely ways in which the world as we know it could end due to Natural Disasters from Space. Cheers to the end of the world!
We’ve all seen the movies: asteroids and comets, earthquakes and volcanoes, solar flares and gamma-ray bursts…all natural ways in which our world can come to an end. And while the most popular films are also the least scientifically accurate, the events that they portray are rooted in fact. Follow the break to read about a few of the most common apocalyptic natural disasters, as well as a few you probably have never heard of.
Death by Cosmic Collision
We’ll get the most obvious one out of the way first. This has been the topic of the most popular disaster movies within the last two decades, and reasonably so: the thought of a giant piece of rock smashing into Earth is horrifying. After all, we were all taught from a young age that a comet or asteroid likely caused the extinction of all dinosaurs on Earth about 65 million years ago. Even though we have not directly observed a major impact event on Earth, we know quite a good deal about the effects that they have had based on geological and archaeological evidence. Not only this, but advanced models have been developed that predict the precise details of an impact based on our knowledge of physics.
Even though we live close to a massive asteroid field and comets regularly come through our solar system, the odds of an impact are incredibly small – about one in 100,000,000 for a disastrous collision in any given year (there is a meaning behind the phrase ‘astronomical odds’). NASA currently runs a program designed to spot and catalog “near-earth objects”, and there is a high degree of confidence that all 736 such objects have been found. However, in 2004, a discovery was made that had possibly apocalyptic implications: Asteroid 99942 Apophis was believed to have as high as a 2.7% chance of impacting the Earth in 2029, creating intense interest in this and other near Earth objects. However, after more observation, it was concluded that Apophis would only have a 1 in 250,000 chance of impacting Earth, and that it could happen in 2036 instead of 2029.
For curiosity’s sake, I used the impact calculator to see what would happen if an iron asteroid the size of London hit land while travelling at 11km/s. Needless to say, the effects would be devastating. The impact crater would be roughly 45 miles deep and 136 miles in diameter. The energy released by the impact would be equivalent to almost 340 billion of the atomic bomb dropped on Hiroshima. It would cause an earthquake of magnitude 11.1 on the Richter scale, and the displacement of air would cause winds in excess of 1,500 miles per hour. Nearly everything and everyone on the Earth would be destroyed. Don’t worry though – an impact event of this size will likely never happen on Earth, ever ever ever.
This phenomena is well known in astronomical circles but rarely discussed anywhere else. Basically, when a huge star is dying, it reaches a point when the mass of the star no longer has enough gravity to hold itself together, leading to a spectacular event known as a supernova. During this process, most of the outer material of the star is thrown out into space in a brilliant explosion, and the rest of the star collapses to form tiny neutron stars or even black holes. Because this collapse typically takes the form of a spiral, the events can be accompanied by a massive blast of gamma radiation shot in a thin “jet” in both directions along the star’s axis of rotation.
Were the Earth to lie in the path of a gamma-ray burst, the effects would most likely lead to mass extinctions; the ozone layer could literally be pealed away, and any living thing on the side of the world exposed to the burst would simply be fried or succumb to acute radiation poisoning. Mass starvation and food-chain depletion would likely follow.
Should you be worried? Probably not – these events are very rare, and the odds that Earth will lie in the path of one are even more remote. Astronomical satellites detect about one gamma-ray burst a day, but most are billions of light-years away. A burst originating from a star in the Milky Way is estimated to happen only about once every 100,000 to 1,000,000 years. Unfortunately, since these bursts travel up to 99.95% of the speed of light, we probably would not know it was coming until it was already here.
Here Comes the Sun…Seriously
Whether or not the Earth is able to outlast the extremely improbable events listed above, we do know for sure that one day, all life on Earth will likely cease to exist. Ironically, the object that currently sustains life on our planet – the sun – will also be the object that will end it. Allow me to explain.
Currently, our sun is about half-way through its primary life cycle. As mentioned before, stars are so massive that they are able to virtually hold themselves together by the force of their own gravity; however, as the fuel within the sun is slowly converted to light and sent out into space, it will inevitably lose mass, and therefore, gravity. The result of this is the gradual expansion of the sun into what is called a “red giant”. In this phase, the radius of the sun will increase 250 times – well beyond Earth’s current orbit. The loss of gravity, however, could also mean that the orbits of the planets will drift further and further away from the sun, essentially sparing them (except Mercury, which will likely be swallowed by the sun).
Unfortunately, none of that will matter. In the past billion years, the sun has become about 10% brighter and its surface temperature has increased as a result of the natural processes described above. It is likely that billions of years before the sun starts turning into a red giant, the surface temperature on Earth will increase to 60° C (140º F), causing our oceans to virtually evaporate into space. At that point, life on Earth will no longer be able to exist in the natural environment. We will be better off than Venus though – the sun will be so intense that its atmosphere will be blown off into space.
Should you be worried? Hardly: the earliest that the “ocean evaporation” scenario is estimated to begin is in around 500 million years. Still, this means that we came a little late to the party because we could now be inhabiting Earth during the last 10% of its habitable life. There is a bright side, however – assuming that humans spread throughout the galaxy long before this starts to happen, we would probably have the technology to come back to Earth in cool spaceships or something. So, billions of years from now, after the sun has thrown off its outer layers to form a nebula, a human could stand on a cold, rocky Earth, look up into the sky, and see it filled with an image just like this:
Is your mind at ease, or did you discover even more things here that send chills down your spine? Let us know below! Also, don’t forget to look our for the next installment in this series where I take a look at some ways the world could end due to natural disasters caused by our very own planet.