I'm trying to find a book I read when I was child like 18-20 years ago.
It's a children's book and all I can remember is that there is the character of a young human woman who is an astronaut studying anthropology of Earth's humans. The timeline on Earth must be around 800 BC or ancient Greece. The woman is basically of advanced human race (like as in the ancient alien/astronaut theory).
The astronaut woman comes down to Earth and hides her ship behind the moon. I think she accidentally gets seen by a human man. So she interacts with him - she teaches him telekinesis - a skill future humans are able to do. He sees her holding a rock or stick mid air above her hand. She tells him he can do the same, just to believe he is capable of doing so - which he eventually does. The young human man sees her a goddess. So the astronaut woman is referenced as a Greek goddess (I'm not sure which one) from ancient Greek mythology.