original russian text
and translation:
At one time we had a long discussion with the grandfather about the structure of the world, since he was an outstanding scientist, and his opinion was more than valuable to me. Once he smiled and said that everything that we know about physics or astronomy is only basically theory. The same applies to the earth’s core and stars, and much more. "Did a man see with his eyes the core of the earth?" - once told me a grandfather, doctor of geophysical sciences, all his life engaged in pure science (just like Hawking). It was then that I seriously thought that everything that we actually know is just our conjectures. After all, nobody really saw the same earthly core with their own eyes, but only assumed that it exists. Only one conclusion. There is nothing exact and absolute in this world.
That is a pretty cool statement
Oh yeah my grandfather was the gem of statements