Recently, Astronomers have noted the Earth has been hit by a stream of cometary debris. Meteor showers are common; but, this stream of meteors was more dense than usuall.
When a comet becomes bound up with a star such as our sun(as oppossed to comets that come from interstellar space, come in and leave the solar system for good), it leaves a stream of debris in that orbit. So, if you find some unusually dense or active meteor showers, you might wonder if it is due to a comet. And, if so, then you can bet there's a good chance that some day, that comet will come by and hit your planet.
Astronomers perhaps were a bit more alarmed about this latest meteor stream because they've never seen it before; they don't know what comet this stream is associated with.
Astronomers have recently become more concerned about possible cometary impacts due to quite probably the refutation of the Nemesis hypotheses. This hypotheses is that our star has a companion that periodically disturbs the Oort cloud of comets(way past thr orbit of Pluto or Neptune, whichever is the furthest solar system object at the time); and, so our planet gets hit by comets on a periodic pattern. Mathematicians have recently shown that the statistical analyses is biased(it's remarkable it took them this long to due this imo). This means that we could be hit by a comet now, tomorrow, or soon enough instead of fifteen million years from now(the Nemesis star was on a 26 million year cycle; we were midway through the last periodic impactor).
And so, I thought it appropriate to show this Arthur C. Clarke Mysterious world episode about the 1908 Siberian explosion!
I think this show is good for more than the fascination/fear of a cometary impact. It shows science when it doesn't have the answers; tunguska presented a bit of a problem; if this was due to an asteroid or cometary impact, where's the crator? There was no crator. So, people were imagining all kinds of possibilities; black holes, alien spaceships(where's the spaceship much less the impact crator?). In the end, it seems that we had a piece of a comet explode in midair.