For millions of years after the Big Bang, nearly all the matter in the universe was in the form of hydrogen and helium; other elements like carbon, nitrogen, and oxygen only formed later, in nuclear reactions inside stars. To learn what the universe looked like back then, MIT astrophysicist Anna Frebel studies the oldest stars we can find—13 billion years old, to be precise—scanning them for traces of elements that will give a clue to their history. As Professor Frebel explains to Sarah Hansen in this episode, curiosity about the origins of the universe we live in is a profoundly human trait, just like curiosity about one’s own family history. To help communicate to laypeople the wonder and amazement that motivates astronomers like herself, Prof. Frebel has written a book and recorded a companion series of videos, both of which are intentionally designed to be as user-friendly as possible. It doesn’t matter, she says, if viewers and readers don’t grasp all the details; her hope is that they will develop the desire to understand more, and that that desire will spark further learning.