If you can’t explain it to a six-year-old, you don’t understand it yourself.
Albert Einstein
The above quote clearly illustrates what we know about quantum physics. In the sense that referring to another quote by the physicist Richard Feynman…
If you think you understand quantum mechanics, you don’t understand quantum mechanics.
Richard Feynman
No one can explain quantum physics to anyone, let alone a six-year-old, so by definition, we don’t understand quantum physics.