KILLER UNIVERSE

RELATIVELY SAFE IN OUR PROTECTIVE BUBBLE, SOME FORCES COULD END LIFE ON EARTH FOREVER. IS THE COSMOS OUT TO GET US?

- Nikole Robinson

While Earth isn't free of destructive impulses - natural disasters, climate change, radioactive rocks and deadly viruses, to name but a few - it's a relatively safe haven for humans among the stars, hence why humans have managed to evolve to live here so successfully. But leaving the confines of our planet's protective atmosphere, the universe gets a lot deadlier. As it turns out, space isn't the most welcoming place for us Earth dwellers, with many ways the universe could wipe us all out in just the blink of an eye.

1 A GAMMA-RAY BURST MELTS THE ATMOSPHERE

Gamma-ray bursts (GRBs) are the most intense, high-energy radiation events in the universe, thought to be produced from explosive cosmic events like hypernovae, black hole formation and colliding neutron stars. Though these beams typically last just a few seconds, they release 10 billion years of solar energy in this tiny timeframe.

We've only observed GRBs in distant galaxies so far, but there's no reason the same physics couldn't apply in our Milky Way. If a nearby event triggered such a burst, and the electromagnetic beam was directed straight at our planet, we wouldn't feel any immediate effect. However, the intensity of the radiation would strip away the ozone layer of our atmosphere in mere seconds, leaving us vulnerable to cosmic rays and the full ultraviolet radiation that the Sun sends our way. And because of the split second nature of GRBs, it would be nigh impossible to predict when one could strike us. It also might not be the first time: a local GRB is one theory put forward to explain the Late Ordovician mass extinction - one of Earth's five major extinction events - which took place around 450 million years ago, wiping out 85 per cent of species in our primitive oceans.