Huge Arizona Hole
There is a place where you can see these dangers written into the Earth's surface. This is the Barringer Crater in Arizona.
50,000 years ago a meteorite struck this site and excavated this dramatic hole. That impact spread debris over tens of thousands of square kilometres. This crater itself is more than a kilometre, or three quarters of a mile, across, so as to can imagine, it was an incredibly violent event.
To get an idea of the force involved in that impact, we can look at two types of rock that you find round here.
Now, this, this is Coconino sandstone. This is what was present before the meteorite hit. Now, down here, you can see what happened to this kind of stone after the impact. So, this rock here, it's chemically exactly the same, but what the impact did to it was just pulverise it.
And the reason for that is that the shock that went through from this impact just fractured all the tiny grains of quartz. Incredibly, all this was done by a meteorite just 50m across. There are thousands of objects circling the sun, trapped by its immense gravitational field. Every now and then, we collide with one. But not all of them are small as the one that created the Barringer Crater.
The Barringer Crater, Arizona
Hidden underneath what is today a place called Chicxulub in Mexico is a huge crater. The impact of the Chicxulub meteorite was cataclysmic. It blasted so much hot debris into the atmosphere that almost the whole planet caught fire. The overall impact was so great it eventually contributed to the extinction of the dinosaurs.
Our orbit regularly takes us into the path of asteroids and comets. And it's a sobering thought that our voyage through space could deliver a random disaster to the whole planet. The good news is that the bigger the potential disaster, the rarer it is. But there is another potential danger that comes from our orbit around the sun. And the best time to see it is at this time of year, in the middle of winter.