"Answers to big questions, from the titular one (answer: "Everything!") to what happens to pee in space ("it would boil, then freeze"). The co-authors--one an astrophysicist, the other author of Geometry Is as Easy as Pie (2020)--offer chatty but cogent responses to a free-floating set of astro-queries. Along with frequent reminders that outer space is unimaginably enormous, readers will get relatively detailed lowdowns on diverse topics including black holes in general ("You'd only see this blindingly bright, white light in the fraction of a second before you were vaporized"), the nature of mass, the possibility that "rain" on planets like Jupiter is made of diamonds, space trash, Cepheid variables, the recordings on the Voyager probes, and the notion of multiple universes: "Crazy, right? But kind of cool too." Highlighted by images of galaxies colliding in a "beautiful cosmic trainwreck" and 2019's breakthrough photograph of a supermassive black hole, an array of well-placed space photos and digital renditions add small but evocative notes of visual wonder that complement the text's abundant enthusiasm. The substantial text is not broken up into chapters, but text-message-shaped callout boxes presenting the questions help walk readers through the narrative, with logical related questions presented in yellow boxes. There is no backmatter beyond image credits. A tasty, digestible buffet of cosmic phenomena for readers with their eyes on the skies." --Vicky Smith, Kirkus Reviews.