Here is the second batch of annotations for The Alloy of Law. As with all of the other annotations here on the site, each annotation contains spoilers for the current chapter. Spoilers for chapters after the current one are hidden by spoiler tags. We recommend you read the book before reading the annotations!

The group investigates the railroad tracks and canal

So, let’s talk about the realities of speed bubbles. I did research on this, and got different answers from people on what really should happen if you could slow time like this. One of the issues is that light doesn’t change speeds based on this sort of issue, so there was discussion of what things would look like inside looking out or outside looking in. It seems likely that there’d be some sort of red shift, and also that things might grow more dim inside a speed bubble. This is all really very theoretical, however, and so—in the end—I decided that there was enough disagreement among scientists with whom I spoke that it wouldn’t be glaringly irregular if I just had the shimmer at the borders and stayed away from dealing with speed of light issues.

There’s a much larger issue dealing with slowed time that rarely gets addressed by this type of fiction. I considered using it, and it’s this: conservation of energy. Inside the speed bubble, Wax and Wayne are moving far more quickly, and therefore have a ton of kinetic energy compared to those outside of it. And so, a coin tossed from inside the bubble going outside would suddenly move with a proportional increase in speed (proportional to how much slower things were outside).

In essence, speed bubble = railgun.

This is dangerous for narrative reasons. I’ve often said that the limitations of a power are more interesting than the powers themselves. (It’s Sanderson’s Second Law of Magics: Limitations > Powers.) One of the reasons for removing Mistborn and Full Feruchemists from the setting was so that we could focus in on the usefulness of the individual powers in Allomancy and Feruchemy. That falls by the wayside if any of the individual powers become too strong on their own.

I didn’t want Wayne to be able to slow time, then sit inside his bubble and leisurely pick off enemies one at a time. And so, I had to place strong limitations on the speed bubbles. (Much stronger limitations than on other aspects of Allomancy. Pushing and Pulling, for example, have their limitations based in solid science. With speed bubbles, I eventually decided that solid science made them way too powerful. So I had to change things.) Therefore, the rules became: No shooting/throwing things out of speed bubbles, no moving speed bubbles, and a required couple second cool-down between creating different speed bubbles. The first rule broke required objects to be deflected when leaving the bubble and that we have the bubble absorb excess kinetic energy when something leaves it.

Disappointing for the scientists, I know, but it makes for a stronger story.