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Exploding asteroids and falling spaceships: Five crazy lights in the sky

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By Daniel Martins
Digital Reporter
@DFLCMartins
Sunday, March 23, 2014, 9:09

People in the Maritimes were scratching their heads this week at a mysterious light in the skies over their homes on Tuesday night.

Whatever it was, it flashed brightly enough to be seen all across the region, and the mystery deepened when another one just like it was spotted the very next day.

Any time there's a huge light in the sky, it sends people scrambling outside to catch a glimpse, whether it's just a harmless lightshow, or a sign of destruction.

Here are five things that got us out of bed to go and take a look.

The Tunguska Event

How’s this for a wake-up call: The largest explosion known to history, a powerful blast in the sky that flattened 80 million trees over 2,000 square kilometres, with the force of 1,000 Hiroshimas.

That kind of power is easily enough to wipe out a whole city, so we were super lucky it happened in a remote and sparsely populated region of Siberia, in 1908.

It wasn’t completely empty region. though. There were several native Siberian inhabitants, along with Russian settlers, who saw a blast “as bright as the sun” and described a shockwave powerful enough to knock people down and kill hundreds of reindeer, although fortunately no human lives were lost.

It was detected by seismometers as far away as England, and cities in Asia reported bright clouds in the sky, likely noctilucent clouds, enough to allow them to read newspapers in the street at night.

Because of the difficult political climate – which included two revolutions, one failed revolution, a World War and a wide-ranging civil war – Russia could only send an expedition to the area in 1927, and its leader had to do some fast talking to persuade the locals to lead him into the zone: They figured, not unreasonably, that the gods had cursed the place.

But while he found a devastated landscape, there was no impact crater, leaving people to wonder for more than a century just what the heck it was.

Some of the weirder theories are entertaining: It was a small black hole! It was an alien space ship! It one of Nikola Tesla's experiments! 

But now the main theory is it was a comet or meteor, around a third the size of a football field, exploding around 5-10 km above the earth.

And it will happen again. NASA says an asteroid the size of the one at the centre of the Tunguska Event enters Earth’s atmosphere once every 300 years.

The Chelyabinsk Meteor

No mystery over this light in the sky. Thanks to social media and dashboard cameras – not to mention the fact it happened over a city of more than a million people – EVERYONE got a glimpse of the huge explosion of the Chelyabinsk meteor in Russia's Ural region last year.

The blast was around 30 times stronger than Hiroshima. As with Tunguska, no one was killed, but 1,500 people were injured, due to windows being shattered by the shockwave.

People reported burns on their faces, and several people were temporarily blinded by the flash, 30 times brighter than the sun. And that was in the city of Chelyabinsk itself, 60 km away from where the blast happened.

The meteor itself was around 20 m across, and when it disintegrated, it scattered debris over a wide area. The largest, recovered from a lake after it smashed through 70 cm of ice, was around 650 kg.

The whole thing was a wake-up call for humanity. Despite being more technologically advanced than ever before, we had no idea this was going to happen until it did

And one of the many studies that have come out since February 2013 suggests Chelyabinsk-sized space rocks in our cosmic neighbourhood may be ten times more numerous than originally thought.

We, ah, might want to start pumping funds into a few more asteroid detection programs. Any time now.

Noctilucent Clouds

Up in the entry on the Tunguska event, we mentioned noctilucent clouds. We were talking about the clouds that start appearing about midway through the video below, glowing in the sky long after sunset.

Noctilucents are the highest-known type of clouds, typically forming 80 km up, just where the upper atmosphere meets the vacuum of space. 

For something so spectacular, it wasn’t until quite recently that scientists figured out more or less how they were formed.

According to records, they were only really noticed in the late 1800s, after the catastrophic eruption of Krakatoa belched enough material into the atmosphere to make for stunning sunsets, along with these clouds. But even after the effects of Krakatoa faded, people still reported noctilucents.

Their behaviour seems to have changed with time, too. Whereas post-Krakatoa, you had to travel to high latitudes such as Alaska and northern Canada to see them, they are now viewable as far south as Nebraska in the northern hemisphere, and we know they typically only form in the summer months.

NASA studies, including the AIM satellite launched in 2007, finally concluded that most of them correlate to meteor sightings. It seems space rocks disintegrating in the upper atmosphere leave enough particles to serve as nuclei for clouds. This theory was confirmed when NASA tracked the water vapour from a re-entering space shuttle's exhaust, and found noctilucent clouds were more plentiful in its wake.

There are still some kinds of noctilucent clouds we can’t quite explain yet, although NASA said their behaviour may be linked to climate change, after they started showing up in May last year, much earlier than usual.

While they’re figuring that one out, we’ll just kick back and enjoy the show.

NEXT PAGE: Those lights in the sky mean there's an earthquake coming

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