Pax atomica means "atomic peace" and it is a term used to describe a period of time when there is no war or fighting between countries, but instead, countries focus on building relationships and working together. Think of it like when you and your friend have an argument, but then you both apologize and decide to work together on building a fort instead of fighting. During the pax atomica, countries come together to solve problems and to promote peace, often through things like diplomacy and treaties. Instead of fighting and using bombs and weapons like in the past, countries use science and technology to make the world a better place. It's like everyone agreeing to use their words and ideas instead of fists and weapons!