Ever since humans looked up to space and its vastness, it was easy to imagine possible dangers coming from above. And they had good reason because Earth has dealt with cosmic threats ever since its creation. Whether by meteors, gamma ray bursts or wandering black holes, the possibility of our destruction coming from outer space is unfortunately a very likely scenario.

Doomsday Scenario No. 5: Cosmic Threats

We as people cower and fret over major disasters that come our way. But trying to imagine how we would face certain extinction from astronomical events is difficult. That is because in our recorded history we haven’t dealt with that kind of phenomenon. What is really frightening is that if we found out tomorrow that any one of these threats were to happen, there is very little that can be done to cope with it. Here are some of them:

Comets and Meteors: This scenario is probably the best known cosmic threat. Every school kid knows that about the theory that a comet or meteor struck Earth and wiped out the dinosaurs 65 million years ago. Earth is constantly threatened by these celestial objects. In fact, meteors enter our atmosphere all the time. Luckily most are tiny and harmless and make great light shows. But all it takes is that one large rock or ice ball to wreck havoc. It happened most recently in Tunguska, Russia in 1908. Though no remains of the meteor or comet have ever been found, the destroyed forest stands as a stark reminder of how powerful the collisions can be.  Some notable sci-fi books about such impacts are Lucifer’s Hammer by Larry Niven and Jerry Pournelle, The Hammer Of God by Arthur C. Clarke and Moonfall by Jack McDevitt, which is a variant of the theme in that a comet destroys Earth’s moon and the lunar debris is what threatens our planet. For films, there is Deep Impact, Meteor and the much-maligned Michael Bay epic Armageddon. Even though there are efforts underway to catalog all the asteroids and comets in our vicinity and have an early warning system, a rogue rock or iceball can slip by our sensors. Oddly enough, thanks to our technology, this is one disaster that can in theory be prevented. Most now know that lobbing nukes at them won’t work, but if there is enough warning then it’s possible to use rockets or satellites to nudge the orbits of the threatening meteors and comets.

Cosmic Collisions: Some scientists believe that our moon was created from another planetary body colliding with Earth. This happened way before life emerged on Earth but if it were to happen today, it would be devastating. Life will not be able to recover. Our only hope as a species would be to do as the characters did in the book and film When Worlds Collide, build a spaceship to escape and settle elsewhere. In When Worlds Collide, the survivors were lucky that they found a habitable world to colonize. For us, our best bet is to head to Mars and try to terraform the planet.  Of course in these situations a lot depends on how much time and capability we have. In the film Melancholia there wasn’t anything that could be done to save humanity and the Earth when it collided with a rogue planet. One thing to note is that a near collision is enough to disrupt life on Earth by causing the world’s orbit to shift and radically altering our ecosystem.

Gamma Ray Bursts: This is caused by the death of a nearby star when the energy is released from the star’s poles. According to scientists this happens in our galaxy every day. If Earth were to be bombarded by these bursts the ozone layer would be depleted and all life would be subjected to lethal exposure to radiation. Thankfully the bursts are too far away to threaten us.  Scientists believe that any supernova occurring about 8,000 light years or closer to us would be a concern. Actually some scientists theorized that gamma ray bursts are responsible for the periodic mass extinctions in our planet’s prehistory. In the book Starfire by Charles Sheffield, our planet is threatened by the radiation unleashed when our closest solar neighbor Alpha Centauri undergoes a supernova. Of course, if our own star were to undergo a supernova, life on Earth would be wiped out. However, our sun still has a few billion years left before it decays. That is unless the sun undergoes that transformation by artificial means. but that would take technology way beyond what we have today.

Solar Storms: Our sun often ejects solar flares or radiation. Back before we became technologically advanced this phenomenon had little effect on us. We would (and still) get brilliant light shows a.k.a auroras in the skies. But today, the electromagnetic pulses (EMP) from a solar flare would fry our computers and machines’ circuits and render them useless. It’s unlikely our civilization would be able to rebuild circuitry and transformers fast enough to stave off a technological collapse. Knocking on wood, this hasn’t happened yet. The most powerful solar storm in the past 500 years happened in 1859 (a.k.a the Carrington Event) and resulted in auroras appearing as far south as the Caribbean. Our technology was in its infancy then and the only machinery affected were the telegraph systems in North America and Europe. Solar storms also pose a grave risk to manned spaceflight in that astronauts would be bombarded by lethal radiation during a solar storm. In the novel Aftermath by Charles Scheffield (which is the prequel to Starfire) Earth undergoes a severe EMP when Alpha Centauri undergoes a supernova. The electronics worldwide are fried and society has to cope with the sudden loss of power and prevent a return to the Dark Ages.

Traveling Black Holes: It’s not likely to happen in our lifetime or even centuries from now, but it is a danger to regard. Scientists believe that our galaxy if filled with wandering black holes, many of them are supermassive black holes; in fact, they occupy the galaxy’s center. Their immense gravity fields would literally rip apart a solar system. If one were to pass by our solar system, its effect would be felt years before it actually arrived. Just on Earth, the orbit would be shifted and massive. By the time the black hole would siphon off our world atom by atom, all life would be long gone. In science fiction, there are many stories about creating artificial black holes and the consequences. This was shown in the last Star Trek film where the villain Nero created a black hole on the planet Vulcan and destroyed it. Later in the film, Nero tries to create a black hole on Earth to destroy it as well. So far, our world is safe from black holes and these other phenomenon. But they should serve as a drive for us to become a true space-faring civilization. This is the best way to guarantee that we would survive far into the future.