When we look at the universe, it seems almost perfectly set up for the existence of life. Many of the laws of physics work in just the right way to allow stars to form, planets to exist, and complex life to develop. This idea that our universe is “fine-tuned” for life has led to many discussions about what it really means. Some believe it might be just a lucky accident, while others think there could be a deeper reason. These debates bring us to the Anthropic Principle, which is a way of explaining why we see the universe as so well suited for living things. The Puzzle of Fine-Tuning Scientists have found that if certain physical laws or constants—such as the strength of gravity or the charge on the electron—were slightly different, stars might not form or atoms might not stay together. If that happened, life as we know it would not be possible. The universe’s seeming “perfect fit” for life is sometimes called the “fine-tuning” problem, because it is as though these constants were set ...