Time Between Milk and Meat

Why do we wait six hours after eating meat before drinking milk or eating milk products, and only a short time after milk before meat?

Because dairy digests much faster than meat it is permissible to eat meat almost immediately afterwards. For most dairy products one need only wait half an hour. Certain very hard cheeses such as mature cheddar, parmesan take a long time to digest, and a person has to wait six hours after eating them before eating meat.