## Checking the math

When I see numbers in fiction that are in some kind of mathematical relationship with each other, I reflexively check the math. (Well, for basic math/arithmetic, anyway.)

Like, if a story says “They traveled at 500 mph from California to Japan, arriving in 45 minutes,” then I think, Hmm, it’s 5,000+ miles from California to Japan, so if they’re traveling at 500 mph, the trip would take 10+ hours. Wait, the text says it would take only 45 minutes! This text is WRONG!!!

I’ve done this kind of checking for as long as I can remember. And I’m not sure why.

In almost all cases, the question of whether the math is correct or not makes no difference at all to the story. (Yes, I know, there are some cases where it makes a big difference, but I’m not talking about those cases.) And in most cases, it’s not immediately obvious at a glance whether the math is right or not; if I didn’t take the time to explicitly check, then I wouldn’t know and it wouldn’t matter.

But somehow, I feel the need to check. If the math is right (as it usually is), I suppose I get a small sense of satisfaction—maybe because it reassures me to find that the author’s reality and my reality are in sync and that math works the same for both of us, or maybe just because at some level of my mind, correctness is in itself a virtue. (I recognize that that’s a problematic attitude, and I try not to get carried away with it.) If the math is wrong, I get a small sense of unhappiness, similar to how I feel when I see a typo, because something is wrong.

If math comes up in a work that I’m editing, then it makes perfect sense for me to check it. But in most cases where I do this kind of checking, I’m not editing, and the work that I’m reading was published long ago; it’s not like I’m going to drop a note to the author or the publisher asking them to fix a story that was published in 1950.

So I’m not sure how I got into this habit. I do this checking-the-numbers in non-sf too, and even nonfiction, but I suspect that I picked up the habit from reading a lot of 1940s-1950s sf in which the math is explicitly written out. At this point, I’ve been doing it for so long that it feels completely ordinary to me. I think it was only sometime in the past few weeks that it consciously occurred to me that I don’t really need to check all the math I run into.

I generally don’t check advanced math or physics or other fields that I don’t know as well or can’t check as easily. Once in a while, a claim in a story will seem so unlikely to me that I’ll go do some research about it to find out whether it’s true, but that’s a different category of issue; in that case, I’m checking something because I think it might not be true, rather than just out of habit.

But for basic math, if I see it in a story, I’ll check it.

So now I’m wondering: is this a common habit? Do y’all who like math do this kind of checking as a matter of course? Again, I don’t mean noticing obvious errors, I mean pausing in your reading to do some calculations in order to see whether the numbers given are correct.

### One Response to “Checking the math”

1. #### Sumana Harihareswara

I do not do it EVERY time, but I think I do this arithmetic once in a while, if something feels really off, or if I’m trying to work out some worldbuilding I don’t understand yet and I think the word problem is a form of incluing. For instance, the “shift” unit of time in Situation Normal features in a conversation where someone is trying to understand some duration (measured in shifts) in terms of our usual time measurements (e.g. days). I probably stopped and tried to check as a way of understanding how long shifts, decishifts, centishifts, etc. were.