The video, the conversation about gravity, that the astrophysicist Janna Levein has with the child, is a world apart from the conversation she has with another expert in the field.
Janna is sensing the level of knowledge of the person with whom she is talking and adjusting the conversation to that level. It is quite magical. Knowledge is best shared through face-to-face conversation.
You will find several similar other sets of conversations on a variety of concepts here if you are interested.