Is it possible, by looking into an empty vessel, to see a map of our Universe? Answer: yes! After all, the contents of an empty (at first glance) vessel is a seething world, full of molecules that rush at breakneck speeds. And the behavior of gas molecules illustrates numerous mathematical theories that are fundamentally important for understanding the world order. It was studies of the properties of gas that allowed scientists to take a closer look at such complex concepts as randomness, entropy, information theory, and so on. Let's try to look at the Universe through the neck of an empty vessel!