Where did the radically ambitious thinking go?

[Epistemic status: Speculation based on two subjective datapoints (which I don’t cite).]

Turing and I.J. Good famously envisioned the possibility of a computer superintelligence, and furthermore presaged AI risk (in at least some throwaway lines). In our contemporary era, in contrast, these are fringe topics among computer scientists. The persons who have most focused on AI risk are outside of the AI establishment. And Yudkowsky and Bostrom had to fight to get that establishment to take the problem seriously.

Contemporaneously with Turing, the elite physicists of the generation (Szilard, in particular, but also others) were imagining the possibility of an atomic bomb and atomic power. I’m not aware of physicists today geeking out over anything similarly visionary. (Interest in fictional, but barely grounded technologies like warp drives doesn’t cut it. Szilard could forecast atomic bombs and their workings from his knowledge of physics. Furthermore, it was plausible for Szilard to accomplish the development of such a device in a human lifetime, and actively tried for it. This seems of a different type than idle speculation about Star Trek technologies.) At least one similarly world-altering technology, Drexlarian Nanotechnology, is firmly not a part of the discourse between mainstream scientists. (I think. I suppose they talk about it among themselves surreptitiously, but in that case, I would be surprised by how little the scientific community has pursued it).

I have the impression (not based on any hard data) that the scientists of the first half of the 20th century regularly explored huge, weird ideas, technologies and eventualities that, if they came to pass, could radically reshape the world. I further have the impression that most scientists today don’t do the same, or at least don’t do so in a serious way.

One way to say it: in 1920 talk of the possibility of an atomic bomb is in the domain of science, to be treated as a real and important possibility, but in 2018, nanotech is in the domain of science fiction, to be treated as entertainment. (Noting that atomic bombs were written about in science fiction.)

I don’t know why this is.

• Maybe because current scientist are more self-conscious, not wanting to seem unserious?
• Maybe because they have less of a visceral sense that the world can change in extreme ways?
• Or maybe “science fiction” ideas became low status somehow? Perhaps because more rigorous people were hyping all sorts of nonsense, and intellectuals wanted to distance themselves from such people? So they adopted a more cynical attitude?
• Maybe the community of scientists was smaller then, so it was easier to create common knowledge that an idea wasn’t “too out there”.
• Maybe because nanotech and superintelligence are actually less plausible than atomic bombs, or are at least, more speculative?

I want to know: if this effect is real, what happened?