1 Adam: So what happens if we blow up while travelling through time?
2 Jamie: I'm not sure, but I suspect some sort of insanely overpowered fireball that causes a rip in the space-time continuum.
3 Adam: Hah! Take that, history! Who says you can't change the...
4 SFX: Fwackoom!

Oops.

Let this be a lesson to anyone planning to take unstable explosives on a time journey. It's much better to simply make your own gunpowder when you get there. You all have one of those T-shirts, right?

EDIT: I was thinking of this shirt, by Ryan North, most excellent author of Dinosaur Comics. Alas, that shirt actually doesn't include a recipe for gunpowder! So I have filled the gap with this essential T-shirt for every time traveller.

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2025-04-04 Rerun commentary: I've removed the link to the T-shirt I designed, since it's no longer available. It was basically a shirt with the recipe "75% saltpetre, 15% charcoal, 10% sulphur" on it.

Nowadays that could probably get you arrested for terrorism in some parts of the world.