What is light? In particular, what is light from the sun? What may be your answer when you are suddenly confronted with such a question?
Surely it would not be a surprise if the question elicits a shocking, caught-in-the-act, stammering realization in many persons.
Oftentimes the automatic answer is the funny “Well, light is light!” But this answer should not be a surprise too.
Light has always been there, and we live day after day without finding the necessity to know further what is light or what is the definition of light.