In 1832, our planet is known to have actually
passed through the tails of comets, but nothing came of it. What would
happen if we unfortunately encountered the actual nucleus of one is a
question more easily asked than answered.
Pearson's Magazine (1900)
Every now and again since about the early 19th century a
new asteroid or comet would be discovered and some crude calculations
would show that it would pass near the Earth. In the popular
press this would soon be changed from "pass" to "hit" and a minor
panic would ensue before cooler heads prevailed. Sometimes the
body in question didn't even have to be in danger of hitting the
Earth. In 1910, the Earth passed through the tail of Halley's
Comet, which caused no end of excitement when people learned that the
comet's tail contained deadly cyanogen gas. The fact that the
tail was so diffuse that only an expert could tell it from hard
vacuum didn't seem to matter much and hawkers of oxygen bottles and
"comet pills" had a profitable little day.
But what about when something the size of a planet shows up making a
bee line for Times Square? This is one of those nasty little
scenarios that you really can't do a whole lot about, because it's
pretty much a matter of Earth, planet: BOOM unless the planet in
question is Mongo and your name happens to be Flash Gordon.
only way that you can get anything interesting out of colliding
planets is to either a) deal with how to prevent it, which is pretty
much avoiding the issue or b) talk about how to get the heck out of
the neighbourhood before your planet gets the finger.
This is basically the plot of When Worlds Collide
Wylie and Edwin Balmer, which was published in 1932, and the George
Pal film version in 1951. In this take on the problem, the
offending body that will do for the Earth just happens to be dragging
along an Earth type planet in tow that will, by astonishing
coincidence, plop right into Earth's orbit after the old homestead has
been reduced to gravel. A load of scientists with remarkable foresight
and maddeningly glossed over technical developments manage to build a
space ark that carries a handful of refugees and assorted livestock to
the new world. In the novel, which was authored by a pair of
pulp writers who were trying desperately to create "adult" fiction, this
was accompanied by some of the most overwrought dialogue and a plot
that reads like it was dropped into a Cuissinart. The film, on
the other hand, is so straightforward and so sanitised that it manages
to make the end of the world positively mundane.
Maybe it was their way of easing our hypothetical loss.