Rebecca Elson was an astronomer. Her work took her to the boundary of the visible and measurable. "Facts are only as interesting as the possibilities they open up to the imagination", she wrote. Her research involved "dark matter" - hidden mass which can be inferred only from its influence on observable objects: "As if, from fireflies, one could infer the field". Her poems, too, make inferences and speculate, setting out always from meticulous observation and not deterred by a knowledge of how little we can know of the universe. She agreed with Einstein's "A clear explanation that anyone can understand": she makes it possible for general readers to imagine how space curves, how each of us centres a universe of our own, and how much more there may be than our technologically enhanced perceptions allow us to experience. Extracts from notebooks record the ways in which she refined her understanding. "A Responsibility to Awe" collects her best poetry and extracts from her notebooks. An autobiographical essay provides background to this alert imagination, from her upbringing as a geologist's daughter in Canada to her scientific career around the world.