I've always placed the beginning of the 20th Century at the formation of Nietzsche's concept of "nihilism". If you remove God, the lynchpin from the moral equation, the structures of meaning and valuation fall apart and the result is the void of nihilism. That is what Nietzsche believed we had unknowingly done and what he was describing with Zarathustra's notorious proclamation that "God is dead".
At the close of the 19th century and the start of the 20th science was asking and answering questions that supplanted God with mechanistic explanations for the structure and order of the universe. Some of the paradigm shifting examples along these lines include Darwin's "Origin of Species", Frued's theories of the unconscious and Einstein's Theory of Relativity.
Recently, I've noticed a renewed and vigorous interest in "pulling back the curtain" and "popping the hood" in scientific literature for lay audiences. What's most striking about the kind of examinations being conducted is that they tend to inquire about primary processes or fundamental aspects of human experience. Take for example a recent Wired article: Inside Jokes: Science Writer Jim Holt Explores Why We Laugh.
WNYC's Radio Lab is a scientific journalism series that explores simple questions like what is laughter, sleep, time and space.
A steady stream of books by economists and behavioral economists in the "freakonomics" mold have been published. See Slate's Undercover Economist Series.
I'm currently reading two books that make fundamental inquiries and examine primary processes: Snoop: What Your Stuff Says About You and Made to Stick: Why do some ideas thrive while others die?
Is it a coincidence that a concurrent striving to answer very basic questions and widespread cultural divergence on issues of values and ethics (fundamentalism vs militant atheism) is taking place?
From a cosmological point of view, the hits just keep on killing.