John Wheeler was one of the great physicists... worked with Einstein, was on the Manhattan project, and was one of the leaders in the field of general relativity.

He wrote a musing on the topic in a short little book called 'Beyond the Black Hole'. It is more philosophy than physics... I have a copy he gave my father, you can find a pdf here:

https://www.google.com/url?sa=t&source=web&rct=j&url=https://jawarchive.files.wordpress.com/2012/02/beyond-the-black-hole.pdf&ved=2ahUKEwjKiZq_kInbAhWtnuAKHXVMCcIQFjAAegQICRAB&usg=AOvVaw2wCJTPqgMmUx7x6MHMABwS

You might want to skip down to pg 362 to whet your appetite, and then read through.

As a young child I was lucky enough to sit in on a couple of conversations he had with my dad on the question of what qualifies as an observer, and the observer's place in the universe...

It was a fascinating topic for me... and perhaps someday science can answer those questions, but for now it is still relegated to the realm of philosophy.