“. . . a unique research problem: We neither have a theory nor data! [ . . . ] Some theories suggest spacetime is a kind of substrate or fluid . . .”

Sabine, I just saw this piece, thank you. You might like the first part of my article (on a different subject). It’s a new way to think about gravity, commencing: Consider for a moment that space is . . .

https://garyblaise.medium.com/dark-matter-a-shy-unicorn-4667ae72073b

If you like it, how does one experiment with an abstract component? A brilliant "thought experiment" ?