The idea that the universe has a beginning and an end is a fundamental concept that Stephen Hawking explores in his book. He explains that scientists have determined that the universe began with the Big Bang, which occurred approximately 13.8 billion years ago. Before the Big Bang, there was nothing, not even time or space. The universe was created from a single point and has been expanding ever since.

Hawking also discusses the concept of the "arrow of time," which points from the past to the future. The universe is not static, it is constantly changing, and time plays a crucial role in this process. The author uses a variety of examples, such as the expansion of the universe and the cooling of stars, to illustrate this concept.

Another piece of evidence that supports the idea of a beginning to the universe is the cosmic microwave background radiation. This radiation is present in all directions and was first discovered in 1964 by Penzias and Wilson. It is believed to be the leftover radiation from the Big Bang and is a critical piece of evidence that supports the idea that the universe had a beginning.

The idea that the universe has an end is also discussed in the book. Hawking explains that the universe will eventually run out of energy and will stop expanding. This will lead to a contraction of the universe, which is often referred to as the "Big Crunch." The author explores various scenarios for the end of the universe, such as the collapse of stars and the eventual decay of black holes.

Overall, the concept that the universe has a beginning and an end is a crucial idea that forms the foundation of modern cosmology. Through a variety of evidence and examples, Hawking shows that the universe is not static but is constantly evolving. The author's engaging style of writing and use of anecdotes and examples makes this complex idea accessible to a wide audience.