[Astromancer]

Unless there is a truly spectacular development, like cheap high-temperature superconductors or cheap durable quantum computing, we might not be able to see a Tech Level change. The transition from TL4 to TL5 makes good sense, there were many changes coming together in the Early 18th century. But someone living in the Cotswolds might be excused for not noticing the changes. Heck, there would be perfectly clear headed people in London, Paris, and Amsterdam, that would have missed the transition.

How do we know that we could see the difference between late TL8 and early TL9 even if it was right in front of us?