A neutron walks into a bar and asks how much for a drink.

This classic science-based pun tickles the funny bone by playing on a fundamental property of subatomic particles. The humor hinges entirely on knowing that a neutron, a particle found in the nucleus of an atom, carries no electrical charge. So, when the bartender offers "no charge," it's a clever double entendre, referring both to the cost of the drink and the inherent nature of the neutron itself.

The setup of a neutron walking into a bar sets the stage for this witty wordplay, transforming a basic physics fact into a humorous interaction. It's a delightful example of how scientific concepts can be woven into everyday scenarios to create a quick, intelligent laugh. The joke's charm lies in its simplicity and the satisfying click of understanding when the audience connects the scientific definition with the bartender's seemingly generous offer.