The Age of the Universe by Amelia Williamson Smith.
Looking out from our planet at the vast array of stars, humans have always asked questions central to our origin: How did all of this come to be? Has it always existed? If not, how and when did it begin?
How can we determine the history of something so complex when we were not around to witness its birth?
Scientists have used several methods: checking the age of the oldest objects in the universe, determining the expansion rate of the universe to trace backward in time, and using measurements of the cosmic microwave background to figure out the initial conditions of the universe and its evolution.