The highlights of the Big Bang model, which says that the universe evolves from an initial hot, dense state; finding that the Big Bang is not necessarily the beginning of the universe, but rather the energetic start of an existing expansion phase.

Beginning a hundred-billionth of a second after the Big Bang, trace events as the universe quickly cooled from a quadrillion degrees. Learn about the strong, weak, and electromagnetic forces, and the fundamental particles-all of which precipitated from the seething cauldron of energy, even as matter and antimatter were mutually annihilating.

Continue the story of the early universe by exploring such highlights as the formation of the first atoms at 370,000 years, when space transitioned from opaque to transparent; the accretion of hydrogen and helium gas into protogalaxies after millions of years due to gravitational influence of dark matter; and the collapse of the gas into ever denser balls eventually leading to the first stars.

Is it possible to calculate the size of the universe at the instant of the Big Bang? Assemble the clues that scientists use to address this question. In the process, discover a number of remarkable properties of the universe, including that it must be bigger that what we can see, extending beyond the boundary that limits our knowledge due to the finite speed of light and the age of the universe.

Evaluate three mysteries connected to the Big Bang model that baffled theorists beginning in the late 1960s. Why was the early universe so uniform? Why does the universe obey the laws of geometry we teach in high school? And how did the universe come to be made of the kinds of particles we see and not others? A single solution to all three questions seemed too much to hope for, yet one turned up.

Dig into the bizarre theory of inflation developed by physicist Alan Guth, which holds that for a fraction of a second just after the Big Bang the universe expanded at a mind-boggling rate, making the cosmos effectively infinite. Analyze how this idea solves the three puzzles introduced earlier. Learn about associated concepts, such as the scalar field and its decay, known as “reheating.”