On Friday, January 17, 2020 at 7:05:11 AM UTC-8, wrote:

I still say black holes ( and event horizons et al ) are essentially theoretical.

Theoretical, sure, but yet, there is plenty of evidence that black holes exist. For example...

https://www.cfa.harvard.edu/~narayan...McClintock.pdf

It is up to you to provide evidence to the contrary, if you can.