Step four, send their spectroscope back in time to step one.

Now, Keltham isn't sure that part will work, but, if Civilization's teachings about the fundamental nature of reality are true, it shouldn't be that hard for him to create a small time-loop using Prestidigitation -

Step four, send their spectroscope back in time to step one.

Now, Keltham isn't sure that part will work, but, if Civilization's teachings about the fundamental nature of reality are true, it shouldn't be that hard for him to use Prestidigitation to create a small time-loop -