Our Earth is inhabited by an estimated total population of 7.9 billion. Unfortunately, one day the Earth will be inhospitable to anything resembling life. Although life on this planet is not predicted to cease until billions of years from now, depending on changes of circumstances, it might happen tomorrow or anytime in between.
The Earth’s molten core might cool. The Earth is surrounded by a protective magnetic shield called the magnetosphere. Due to the magnetosphere, a field is generated by Earth’s rotation, which swirls a thick shell of liquid iron and nickel (outer core) around a ball of metal (inner core), creating a giant electric dynamo. If the core cools, the dynamo would shut off and we would lose our magnetosphere, along with the protection from solar wind, resulting in our atmosphere getting replaced by the cold vacuum of space. Mars was once rich with water and a thick atmosphere suffered the same fate billions of years ago.
The sun would start to die and expand, forming a red giant. Like all stars, our sun also has a limited source of energy it can burn. Near the end of its life, the fusion of hydrogen to form helium changes the interior composition of a star, which in turn results in changes in its temperature, luminosity, and radius, and so a ‘red giant sun’ forms. In approximately 5 billion years, the sun will begin the helium-burning process, turning into a red giant star. When it expands, its outer layers will consume Mercury and Venus, and reach Earth. Scientists are still debating whether or not our planet will be engulfed, or whether it will orbit dangerously close to the dimmer star. Either way, life as we know it on Earth will cease to exist.
A rogue planet could collide with Earth. A rogue planet is an interstellar object which has been ejected from its planetary system as they were never gravitationally bound to any stars. According to recent simulations, rogue planets may outnumber stars in the Milky Way by 100,000 to one. So, a rogue planet could shove Earth into a deadly orbit and even eject it from the solar system. As a rogue planet, our Earth would freeze into an ice ball.
Asteroids and comets could bombard the planet. Rocks from space can be pretty destructive; a big one probably wiped out the dinosaurs, although it would take a lot of asteroids to properly destroy the entire planet. Still, it could happen to Earth as the planet was heavily bombarded with asteroids for hundreds of millions of years after it was formed. The impact was so deadly that the ocean water boiled for an entire year. All life was single-celled at that point, and only the most heat tolerant microorganisms made it.
Unknown Unknown’s! The first four are the risks we can identify as potential threats. There are almost certainly other dangers out there with grave potential impacts that we cannot predict. It’s hard to even think about how to tackle this problem, but more research into global catastrophic risk could be helpful.
Our life is limited, so be sure to learn with STEM·E in the meantime!