If you’re aiming for “as far as we know, not a single Greek suggested” things like that the earth revolves around the sun” or “everything is made of atoms” do n

If you’re aiming for “as far as we know, not a single Greek suggested” things like that the earth revolves around the sun” or “everything is made of atoms” do not qualify, and even “that atoms can be split” wouldn’t (https://en.wikipedia.org/wiki/Atomism https://en.wikipedia.org/wiki/Atomism proposes “that the physical universe is composed of fundamental indivisible components known as atoms”, but the Greeks did not make the mistake of calling what we call atoms atoms) Chemistry is rather new, though. I don’t think any Greek remotely knew that water is H₂O, and also guess the majority of teenagers would know. The existence of more than 5 planets also is a likely candidate. The Greeks didn’t know that, and knowledge of that in the English-speaking world under teenagers is helped by the fact that one of them is called Uranus.