If the captain of ship a fires a missile, counts 10.0 s on his watch, and then fires a second missile, how much time δt will the captain of ship b measure to have passed between the firing of the two missiles?

If none of the ships are moving, the elapsed time for ship B will be the same Δt = 10s

Explanation:

If no ship is moving then the elapsed time between missiles for both ships will be the same.

On the other hand, if one of them (or both) were moving, then the relative motion of the ships would make Δt seem smaller if the ships were getting closer, or greater if they were distancing from each other.

does anyone know or what?

that tool is called an altimeter which measures your altitude which can be used to tell which atmosphere you are currently in, including the stratosphere.

hope this ! : )