Thanks for all the many different ways to speculate on the light-time travel connections.

I wonder, do you think it's possible to go back or go forward in time and change things or just observe them?

There's been several occasions where people report there's been time-shifts and they saw either the past or the future. But off hand I can't recite a specific case.
Except for a person I met on a forum many years ago who used to speak of time-shifts he'd been in. As best as I can recall, He said during one, he was observing a home place like setting from maybe the early 1800's. He tried to take photos but he couldn't get his camera to work.
I thought it was interesting and made sense that the camera didn't work, because perhaps you can't use a device if it wasn't invented at that time of the century and region you're in.

Thanks for your feedback. I enjoy it greatly. Your chessboard theory is much like the bubble theory of poli-verses that I like so well.