I'm working on a bit of world building, and I was curious if it seemed to much more experienced worldbuders than I that including a collision with Halley's Comet in 1835 or 1910 as a major plot would seem to preposterous to be taken seriously. The closest Halley's has ever been recorded to pass to earth is 1/15 of an astronomical unit (the distance between the earth and the sun). It was known to pass our orbit in 1835, 1910, and 1986, with 1910 the closer shave.

Would something so preposterous invalidate the world I am building?

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    $\begingroup$ Um, what exactly are you wanting to know? $\endgroup$ – bowlturner Sep 3 '15 at 20:36
  • $\begingroup$ Excelseo, it may not be obvious but you'll want to re-state your question, in greater detail, inside the body. Don't just rely on it being present in the question title. Also this is fairly short, feel free to elaborate on what exactly you're wanting to know, or why - for example - you think it might be preposterous. $\endgroup$ – Dan Smolinske Sep 3 '15 at 20:46
  • $\begingroup$ Mostly if something so unlikely would invalidate the world I'm building. $\endgroup$ – Excelseo Sep 3 '15 at 20:47
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    $\begingroup$ You could always make it Helford's Comet or in '34 or Bailey's Comet in '11. $\endgroup$ – o.m. Sep 4 '15 at 5:26

I actually recommend using Sanderson's First Law of Magic to resolve this. Technically what you are looking for is not magic, but the rule turns out to be so useful for things like this that it's worth trying to convert it to an applicable wording for your problem:

Sanderson's First Law of Magic

An author’s ability to solve conflict with magic is DIRECTLY PROPORTIONAL to how well the reader understands said magic.

By that law, the question you should ask is how much conflict do you solve with the collision, and how well do your readers understand it. The more conflict you try to solve, the more you should take the time to make sure it is physically reasonable.

On the other hand, if the specifics of the collision are not important for the story, you may get away with it just being one of the many details which make a world seem "real."


I don't see why it would be a problem as the basis for a story. Its not too unbelievable to think in an alternate timeline that its path projections were a bit off, or that some other body nudged it slightly off into a collision course with Earth.

But... Haley's comet is thought to be bigger than the one that killed the dinosaurs off, so it will be a planet changing event (at least for humans).


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