Main Question or Discussion Point
I Am Wanting to Find out who Created the inverse square law.
It would have been much easier verify the ISL using light. His astronomical observations would not have given a direct 'proof' of ISL but he could have easily verified the effect of the ISL law with a simple photometer. You could do it yourself, on the 'kitchen table' with some light bulbs, tracing paper, oil and some cardboard boxes, painted black, to exclude extraneous light and reflections. No light meters need to be involved.the force of gravitation falls off in strength at a ratio of 1/r2
The ISL was known long before Newton came along, and not only in connection with gravitational concepts:I Am Wanting to Find out who Created the inverse square law.