Carl Sagan once called Earth a “pale blue dot.” It’s true since, compared to the vastness of the universe, we’re truly diminutive.

As it turns out, our “pale blue dot” is also quite fragile. Countless void-borne hazards threaten life on Earth. I’m going to count us down, starting with the rarest danger.

3. The Gamma Ray Burst: The Universe’s Answer to the Death Star

Since 1991, we’ve seen about one Gamma Ray Burst (GRB) per day in galaxies far, far away. Each of those galaxies sees one approximately every 10,000 years.

Why are they so rare? Space.com tells us that they’re the side-effects of the formation of black holes from two neutron stars collapsing into one another or when a black hole consumes another neutron star. They’ll also blind you with a burst of light more brilliant than supernovas or even hypernovas.

But that’s not what should worry you. What you do need to worry about are the dense directional lines of gamma rays they spew across the void. That’s the actual GRB.

They’re nothing to scoff at. GRBs can shear Earth’s Ozone layer, irradiate most of our ecosystems, and cause a chemical reaction in our atmosphere that would form harmful ozone at ground level to choke us. A GRB may have already hit Earth 450 million years ago (m.y.a.), potentially causing an ice age and the Ordovician Extinction Event which massacred marine life.

Thankfully, GRBs are deadlier the closer we are to their origin. We should be fine as long as no black holes form nearby.

2. Losing Earth’s Magnetic Field: Our Natural Planetary Shield

Closer to home, Earth’s magnetic field is a big part of why we’re alive. With it, we get to keep our atmosphere, get an umbrella against cosmic radiation, and shelter from solar winds and flares. Losing it would be catastrophic to life on Earth. We should be thankful, especially since we get the northern and southern lights as a bonus!

The field isn’t without its hiccups. It will periodically flip its poles every 300,000–500,000 years, which can drastically weaken it. The Laschamps Excursion, a temporary flipping of the poles 42,000 years ago, reduced the field to a mere 5% of its strength and may have been responsible for numerous extinctions. Another flip may have been responsible for the End-Ediacaran Extinction 542 m.y.a.

Every shield has its limits. According to the European Space Agency, our magnetic field has weakened approximately 9% over the last two centuries. Even then, let’s not forget a solar flare in 1989 was strong enough to knock out power in Québec, Canada with our shields still up.

1. Asteroids: More Than What Killed the Dinosaurs

Here we are. The literal “big one.” This is the astronomical fear that spawned not one, but two movies in 1998: Armageddon and Deep Impact. It’s natural to be afraid, especially since there are so many tracked—and untracked—near-earth objects: over 1350 known threats as of 2022.

Earth is used to invasive space rocks raining down onto it. Theia, the biggest known Earth impact, ejected enough molten material from earth to form the Moon.

But the best-known impact is the one that wiped out the dinosaurs 65 m.y.a. A 13-kilometre-wide rock slammed into us at 72,500 km/h, kicking up trillions of tons of dust into the atmosphere, halting all photosynthesis, and wiping out 80% of life.

Asteroid impacts aren’t always bad, though. A study on Yarrabubba’s crater tells us its impact 2.29 billion years ago through an ice sheet several kilometres thick may have vaulted trillions of tons of water into the atmosphere. It may have given us the greenhouse effect that shaped the atmosphere we know today.

Thankfully, our biggest known threat, Asteroid 1950 DA, is only 1.1km across and has only a one-in-three-hundred chance of hitting us in the year 2880. Mark your calendars!

So, is it the end of the world as we know it?

Our “pale blue dot” is truly vulnerable. Thankfully, probability says all these Earth-shattering things will likely happen anywhere but Earth. At the very least, if we have to live in a real world with real threats, we don’t have to worry as much about fiction’s most popular space-borne threat: alien invasions.    

 Or do we?

Shawn Brixi — I’m an avid fan and writer of science fiction and fantasy. From the Alien to Star Trek, I’ve always been a fan of any media taking place in space and of the science of space and stellar exploration as a whole! I even built a model of the Hubble Telescope back in Grade 8 (before some goof broke it).

It’s my hope to eventually write a great book; whether it takes place in the cosmic void or another world entirely is anyone’s guess. In the meantime, I hope to entertain you all here on this blog!