The Little Book of the End of the World (2 page)

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PLANET-KILLERS AND CREATORS

Most of what the planet throws our way does a lot more damage to humans and man-made structures than to the face of the Earth. For humans, a ‘natural disaster’ may cause the loss of life or limb, but to the planet such events are more like a minor case of acne.

But before we look at some of these internal threats, we should look at the bigger picture: what about those that come from outside? Like the neighbours’ bratty kids, the universe has a tendency to throw rocks at our windows. Even as mankind looks to the sky with aspirations and promises of success, there are still things up there just waiting for their opportunity to fall on us.

ASTEROIDS, METEORS AND COMETS: WHAT’S THE DIFFERENCE?

Like terms about the End of the World itself, the above three words get used almost interchangeably, but there are some very specific differences. Of course, nobody really argues semantics when a giant ball of rock is flying at their planet.

Asteroids

These are the dangerous ones, but there isn’t much reason to worry: most of the asteroids we know about come nowhere near the Earth.

Most of them.

Asteroids are planetoids, chunks of rock and metal that float around our solar system: some formed on their own, while others are the debris left over after small planets or other celestial bodies have broken up.

Most of the asteroids in our solar system are located between Mars and Jupiter, suggesting that, at some stage, there were other planets or large bodies occupying this space. This was a common view amongst nineteenth-century astronomers, but later discoveries have challenged those opinions: these asteroids are made up of different minerals and rocks, too dissimilar to have a common origin.

There are several million asteroids in this asteroid belt, with anywhere up to 2 million of them a whopping kilometre in diameter. If you’ve ever dropped a bowling ball – average diameter of 21cm – you should have an idea of the destruction any asteroid impact could cause to planet Earth.

The sheer distance from these asteroids means that an impact from any of them is unlikely to ever happen. However, there are other asteroids loitering around our solar system, just looking for their opportunity to cause some damage: some of these are so close that they’re even designated as being ‘near-Earth’.

NASA has estimated that there are nearly 1,000 of these near-Earth asteroids – if there is any immediate danger to our planet, it will come from these. Both the Aten and Apollo asteroid ranges have sent visitors our way recently, and if something even bigger comes, it would have its origin here.

Meteors

Meteoroids are significantly smaller than asteroids, up to a metre in diameter, making them about the size of a Mini Cooper.

Size is the only real difference between an asteroid and a meteor: in fact, they’re likely to have the same origins, with most meteors formed from the debris of asteroids. Some meteors could have their origins closer to home, however, with some formed by rubble from a prehistoric Earth or the moon.

There’s a precise science to naming meteors too:

  the piece of rock in space (or entering the Earth’s atmosphere) is referred to as a meteoroid;

  as the meteoroid enters the atmosphere, it will start to break up, forming a meteor. This word specifically refers to the blazing trail left by the meteoroid, not the piece of rock;

  when what is left of the meteoroid has burnt up and reacted with the Earth’s atmosphere, the metallic rock that strikes the Earth is known as a meteorite.

Comets

Like a meteoroid, a comet is a small body, but it is not formed of rocks and minerals: instead, a comet is formed from ice and dust, with the visible effects of the comet’s tail caused by the reflection and refraction of light as the comet flies through space.

Comets typically have an orbit, either around the sun or another celestial body: that means that their appearance can be predicted, and most of the comets that we see today have visited before. It also means that impacts are very unlikely, with comets and our home planet having partaken in this complicated dance for millions of years.

However, small changes to the orbit of a comet can take place, so comets can still end up moving closer – or further away – on successive passes. Halley’s Comet in particular has caused numerous scares involving potential impacts, usually caused by predictions made about what the comet could bring with it.

ROCKS IN SPACE AND THE END OF THE WORLD

With all those rocks floating around our planet, it’s little wonder that there are so many opportunities for collisions: it’s not just the concern of movies like 1998’s inappropriately titled
Armageddon
.

In fact, there are plenty of collisions that never quite make it to the evening news. These are typically called ‘impact events’, but don’t always involve an impact: in many cases, a meteoroid or other body will burn up as it enters Earth’s atmosphere, turning an impact event into a non-event.

But don’t get too confident.

There have been noteworthy impact events in the past that might have changed the shape and future of this planet. Who knows what could happen if another one like these occurred?

The Moon’s Secret Origins?

Back 4.5 billion years ago, the Earth was just a toddler. And like every foundling child, the planet was prone to a few bumps and scrapes.

A number of scientists have put forward a theory that the moon was created after a ‘giant impact event’ but this would have had to be with the mother of all asteroids: the current theory is that this impact was with something the size and density of Mars.

This doesn’t mean that this impact created a moon-sized crater that we’ve somehow not noticed over the last few millennia: at this stage of the Earth’s formation, the planet would not have been fully solid, and the impact would have kicked up significant amounts of the material that would soon form the surface of the planet. As this matter cooled and recovered, there would have been enough gravitational forces at work to force things back into a spherical shape.

Tests carried out on samples from the lunar surface have made this a pretty likely suggestion for the moon’s origin: our planet’s only satellite is made from very similar materials to the planet itself, but is curiously lacking in some of the minerals that are found closer to the Earth’s core. In other words, if the moon was formed by the galactic equivalent of an organ donation, it was done with surface material.

What Killed the Dinosaurs?

Sixty-six million years ago, dinosaurs ruled the Earth. That’s what Richard Attenborough told us in
Jurassic Park
, and I won’t hear it any other way.

In reality, there was plenty of other life roaming our planet around then, and scientists have found proof of insects, lizards, birds and fish that aren’t too dissimilar from the animals that are still alive today.

So why don’t we see any dinosuars?

The notions of an asteroid killing the dinosaurs creates visions of a massive impact, with the dinosaurs dying rapidly in the following shockwaves, but what likely happened was a little bit slower and a lot less dramatic: any impact would have raised a massive dust cloud that killed off most of the plant life and had lasting effects up the food chain.

Proof of this brings us all the way to Mexico and a place called Chicxulub: the area’s interesting topography means this could have been the site of a massive impact event, and geological studies done in the 1970s appear to confirm just that. In a massive coincidence, this impact would have occurred around 66 million years ago. While this wouldn’t have killed off all the dinosaurs in one go, and some species would have survived a little longer than that, the timing is too close to be a coincidence.

Brace yourself for the figures: the Chicxulub crater is about 180km wide and was probably caused by an asteroid nearly 10km in diameter. That’s about the size of New York’s Central Park.

30 June 1908: Tunguska, Russia

A streak of blue light moves across the sky near the Tunguska River, followed by an explosion that smashes windows, knocks people off their feet and flattens 2,000sq.km of woodland.

Even a century later, the Tunguska event courts the attention of conspiracy theorists, in no small part due to the closed borders and secrecy of different Russian regimes throughout the twentieth century. But various studies have been carried out in the area, all of which agree that the site saw some form of impact event, but leaving scientists nonplussed by the lack of an obvious crater.

So when is an impact event not an impact event?

When the asteroid explodes in mid-air with such force that the shockwave is solely responsible for the destruction. It almost sounds too good to be true, had the events not been repeated just over a century later.

15 February 2013: Chelyabinsk, Russia

Russia gets another close call with a collision, this time near the city of Chelyabinsk, only 2,000km away from Tunguska. Once again the celestial body burned up before impact, creating a shockwave that could be seen and felt for miles around, smashing windows and causing considerable destruction.

Like the Tunguska event, there was significant property damage. Unlike Tunguska, the Chelyabinsk event took place in the age of digital media and got caught on camera, with footage and images making their way onto international news networks.

THE PLANET KILLER

With so many impacts and near misses, we have to wonder if it’s possible that an impact event on a massive scale could wipe us out. Hollywood would have us believe that it would be a fiery, quick death, but as we’ve learned from the dinosaurs, it’s far more likely that it would be slow and involve a significant lack of food: after all, our dependence on plant life and the bottom of the food chain is no less important to us than it was to the dinosaurs.

As we discover more about the history of the planet on which we’re living, we realise it is only a matter of time before an impact event occurs of significant size to create damage to a town or settlement. Whether that would spell the End of the World probably depends on how close you live to this impact.