Even if we don’t destroy ourselves, we always have the Universe to contend with.
Wiping out all life on Earth is hard, but causing mass extinctions is easy.
Five major extinction events have occurred since the Cambrian explosion, each eradicating over 60% of terrestrial species.
At least five extraterrestrial scenarios are capable of wiping humanity out.
1.) Asteroid/comet strike: a giant impact triggered the last great mass extinction 65 million years ago.
Comet Swift-Tuttle, which could strike Earth in 4479, carries 28 times the destructive energy of that event.
2.) Gamma-ray burst: the brightest electromagnetic events of all are a once-per-million-years risk.
If one occurred within 6,000 light-years of Earth, it would destroy our ozone layer, causing a mass extinction.
3.) A random encounter: the galaxy is full of stars, planets, stellar remnants, and black holes.
If one passes through our inner Solar System, it could gravitationally eject the Earth, destroying us all.
4.) A supernova: these have affected Earth many times, but we have endured without significant harm.
A Type II supernova must occur within <25 light-years of Earth to endanger us, an extremely uncommon occurrence.
5.) Our own Sun: it will eventually incinerate us.
After 2 billion years, the Sun’s increasing energy output will boil the oceans, unambiguously terminating all life on Earth.
Mostly Mute Monday tells an astronomical or scientific story in images, visuals, and no more than 200 words. Talk less; smile more.Ethan Siegel is the author of Beyond the Galaxy and Treknology. You can pre-order his third book, currently in development: the Encyclopaedia Cosmologica.