Right. "Who, a few short years ago, would have suspected that light and heat still held scientific secrets in reserve? Nevertheless, we now have argon in the atmosphere, the x-rays of Roentgen, and the radium of the Curies, all of which illustrate the inadequacy of our former methods, and the prematurity of our former syntheses." That had to be from the early 20th century.

The problems today are either in areas where complexity is the limiting factor, like biology, or beyond current experimental reach, like string theory and dark matter. The complexity problem can probably be overcome with computer assistance. Experimental reach is harder.

I was going to post a criticism along the lines that all the historical examples given by the author were from the 19th Century until I saw you point this out!

The date definitely changes my perspective but I still think the essay is a little too waffley - it doesn't to give any actual examples or indications or where the author thinks important scientific problems lie. In fact it kind of begs the question. In response to a concern over whether there are important scientific problems left to solve, it simply lists some historical important scientific breakthroughs.

I suppose the point is that breakthroughs are unexpected...