Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

Fermat's principle states that light will always take the path of the least amount of time.
Fermat's principle states that light will always take the path of least amount of?

Proteins are long chains of amino acids.
What are long chains of amino acids?

Weight is the measure of the force of gravity pulling down on an object.
What is the measure of the force of gravity pulling down on an object called?