SF author Greg Benford posts a ’97 Peter Nicholls talk:
I decided that I would write ALIEN ARTEFACTS but call it BIG DUMB OBJECTS. … But the joke was on me, because as I came to write the entry, I realized that the subject– which was vast alien enigmatic artefacts–was at the heart of what attracted people to science fiction. And even stranger, I realized that no matter what literary shortcomings you found in Big Dumb Object sf – and believe me, there are plenty – that Big Dumb Object stories were often successful, that even if badly written they were usually good to read. Why? …
There is in science fiction, even or especially (as I will argue later) in so-called Hard science fiction, something which in other context we tend to think of as unscientific, be it called sense of wonder, or the sublime, or the transcendent as the Panshins have it, or the romantic. And one rather mechanical way of creating this effect is for the storyteller to imagine something very very big and mysterious, like the spaceship Rama, or like Larry Niven’s Ringworld. That is, the mysterious something in science fiction often has its locus classicus in the Big Dumb Object. …
Of the BDO novels I’ve cited, [big] voyages in space become [big] voyages in time in the majority of them: … It is, as the celebrated cliché has it, the last frontier, and this ties in with what one does in frontiers of all kinds, one meets the “other”. I think the meeting of humanity with the other is now generally accepted as one of the great themes of science fiction. … The sublime … is dehumanising. It makes us feel small and unimportant and indeed hardly there at all. I think this feeling of our vulnerability and littleness in the context of cosmic vastness and indifference, is one of the root feelings of space fiction. … Sf writers capable of perfectly good straightforward, journeyman prose, tend to fall into florid poetics of the most excruciatingly embarrassing kind when trying to imagine what transcendence might feel like. …
BDO fiction … is about being dwarfed by space and hugeness, about attempting to maintain our own humanity, warts and all, in the light of this vastness, while at the same time yearning to be better or other than what we are. And this is not a theme that is intrinsically scientific at all, which makes it all the odder that it is in the hardest and most scientific sf that we tend to find the purest examples. …
I began by saying that I had recently re-read a dozen or so classics of hard science fiction, and I listed them. What I didn’t say then is that it was a rather disappointing experience. … The main problem is the sense of wonder, that feeling you get when confronted by the truly awe-inspiring in sf. It doesn’t tend to occur so poignantly the second time round. (more)
Immersing ourselves in images of things large in space, time, and social distance puts us into a “transcendant” far mode where positive feelings are strong, our basic ideals are more visible than practical constraints, and where analysis takes a back seat to metaphor. Many “hard science” folks who won’t allow themselves ordinary religious feelings do allow themselves these transcendant feelings. Which seems ok, but for the risk that it might overly infect their practical beliefs.
In my own case, I was raised in a rather bog-standard mainline protestant family. I had no bad experiences with religion. I just started reading about evolution, cognitive biases, bayesian probability etc and eventually admitted to myself I didn't assign a high probability to the existence of God. But I'm just one person.
She means the person's atheism is likely to be based on non-rational reasons, e.g. they were raised by atheist parents and never really questioned it, or simply had a bad experience with religion. Such a person is more likely to slip into hand-wavy spiritualism when exposed to transcendent far-mode feelings than someone who's already heard the sirens and held fast.