Guess you're right but man has yet to discover everything that is "under the sun". That's the beauty of science. It isn't stagnant. Nuclear fission wasn't contemplated 200 years ago even though it was always possible awaiting our undestanding of the principles. Besides, the quote has more to do with human nature than our understanding of nature.
Arkie,
I don't think you want to use nuclear reactors as an example, in light of the Okla natural reactor in Gabon.
http://www.spacedaily.com/news/early-earth-04n.html
However as you say, man has yet to "Discover" everything, nor will we, but that doesn't mean it doesn't already exist under the Sun. I think Solomon's statement stands by itself without any qualification.
Regards,
Boiler Plate
Regards,
Boiler Plate