1.      THE EARTH BECOMES A MICROWAVE AND WE BOIL FROM THE INSIDE OUT LIKE THAT GERBIL IN THAT CARTOON.
The outer layer of Earth’s core is hot. We’re talking, so damn hot that the iron and nickel are liquid and sloshing around as the Earth twirls and revolves around the sun. Fortunately for us, it is because of this liquid core that Earth has the magnetic field that protects us from the Sun’s Evil Death-Bursts of Doom, or, in laymen’s terms, “solar wind.” If you paid any attention to the September 29 post, you’d remember that solar wind is enormous buckets of charges particles that the sun occasionally hurls at the universe and wooshes past our Terra. And the only reason the wind wooshes PAST our planet is because of that magnetic field.
Now, even though all our compasses point north, the Earth’s polarity hasn’t always been as such. Over the last 4.5 billion years of the Earth’s existence, the Earth’s polarity has switched many times (this is caused by the sloshing about of the liquid outer core). As the polarity of the Earth switches, the magnetic field gets weaker and weaker. And weaker. And weaker. And supposedly, it could get so weak that it no longer protects of from the Fiery Rays of Fury and we’ll one day get hit by one and roast from the inside.
2.      THE SUPERVOLCANO UNDERNEATH YELLOWSTONE DECIDES IT’S TIME TO WAKE UP
Yes, I did say “supervolcano.” Yellow Stone National Park – we take our kids there, we laugh at bubbling puddles of mud, we gaze in awe at Ol’ Faithful, we steer clear of the buffalo. What we don’t realize is that Yellowstone lies in a giant caldera – a crater left from a huge volcano. All you +30-year-olds remember Mt. St. Helen’s, right? Well that eruption was a breath of fresh spearmint-scented air compared to the explosion that caused Yellowstone’s 40-mile-wide caldera. 650,000 years ago that mother erupted and sent lava flowing all the way to our own west coast.  Since then, the supervolcano has experienced 3 major blasts and 30 smaller ones. Its last violent episode was 70,000 years ago, and scientists know that it’s still incredibly active. Scientists say that there is no reason it couldn’t blow again.
3.      TIME ENDS
To human beings, it’s a comfort to know that life will go on. Physicists must not be human beings then, because they predict that life will end someday. According the laws of physics, it is impossible for time to go on forever, because at some point EVERYTHING has to stop, and why should time be an exception? We know that the universe is expanding, and apparently it can’t expand forever. Physicists suggest that within the next 3.7 billion years, something so catastrophic will occur that time will end (2012, anyone?)
Read about it here: http://www.technologyreview.com/blog/arxiv/25807/
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4.      THE EARTH GETS HIT BY A MASSIVE METEOR
65 million years ago it killed the dinosaurs (supposedly) – a giant meteor, 180 km long and 10 km deep, smashed into the Earth which resulted in the Yucatan Peninsula. This meteor wiped out all life within a half-continent radius, then sent debris like missiles into the sky, only to be rained back down on the rest of the planet. 90% of all life was wiped out. There’s nothing that’s stopping this kind of event from happening again. Space is filled with junk the size of the Yucatan Peninsula meteor, and it’s all flying around. Of course, nowadays we have technology that could tell us when a meteor was approaching Earth, but we may have no way to stop it. I suppose this won’t mean THE WORLD would end, but certainly most everything living on it would die. Hopefully Bruce Willis will be around when the next meteor is sighted.
5.      OUR SUN GOES SUPERNOVA
Actually, our sun could never go supernova because it’s too small – only stars that are 5 times the size of our sun can go supernova, and when that happens a black hole is formed. When our sun dies, it will become a white dwarf, but that’s not as cool a name. A star only burns as long as it has hydrogen to burn in its core. Once all the hydrogen becomes helium, the star no longer has fuel and it dies. A star the size of our sun becomes a white dwarf – it will swell to become a red giant and burn a second layer of hydrogen into helium, and the helium will become carbon. Once all the carbon burns out, the sun will cool down for billions of years and eventually be the same temperature as space. In the meantime, Earth may or may not get eaten up by the swelling red giant. And even if it doesn’t get eaten, temperatures will rise to lethal numbers, all the water will evaporate, and we’ll die anyway. But no worries – the sun still has about half its hydrogen left and isn’t scheduled to burn out for another 5 billion years. And time will two billion years before that, anyway.