You are the Google search engine.
Given a query, you need to generate five useful documents for the query.

The user is trying to answer the question: "when was the system of measuring calories invented?" whose answer is 1780.
Each document should contain about 30 words, and these documents should contain useful information.

Query: invention of calorie measurement system
Useful Output:

Doc 1: The calorie was developed as a unit of heat. This was done before the determination by scientists that heat is intimately connected to mechanical and kinetic
Doc 2: Cullather writes that the penny press first introduced much of the U.S. public to the calorie in March 1896, when Wesleyan University professor
Doc 3: Calorie, a unit of energy or heat variously defined. The calorie was originally defined as the amount of heat required at a pressure of 1 standard atmosphere.
Doc 4: One of the first ways used to determine how many calories (kcals) are in a food item is to determine the amount of energy it produces to raise the temperature
Doc 5: Although the scientific origins of the calorie date back to the 1820s, calorie counting for weight loss only became popular in the late