Magnus Vinding's Quick takes

An argument in favor of (fanatical) short-termism?

[Warning: potentially crazy-making idea.]

Section 5 in Guth, 2007 presents an interesting, if unsettling idea: on some inflationary models, new universes continuously emerge at an enormous rate, which in turn means (maybe?) that the grander ensemble of pocket universes consists disproportionally of young universes.

More precisely, Guth writes that, "in each second the number of pocket universes that exist is multiplied by a factor of exp{10^37}." Thus, naively, we should expect earlier points in a given pocket universe's timeline to vastly outnumber later points — by a factor of exp{10^37} per second!

(A potentially useful way to visualize the picture Guth draws is in terms of a branching tree, where for each older branch, there are many more young ones, and this keeps being true as the new, young branches grow and spawn new branches.)

If this were true, or even if there were a far weaker universe generation process to this effect (say, one that multiplied the number of pocket universes by two for each year or decade), it would seem that we should, for acausal reasons, mostly prioritize the short-term future, perhaps even the very short-term future.

Guth tentatively speculates whether this could be a resolution of sorts to the Fermi paradox, though he also notes that he is skeptical of the framework that motivates his discussion:

Perhaps this argument explains why SETI has not found any signals from alien civilizations [because if there were an earlier civ at our stage, we would be far more likely to be in that civ], but I find it more plausible that it is merely a symptom that the synchronous gauge probability distribution is not the right one.

I'm not claiming that the picture Guth outlines is likely to be correct. It's highly speculative, as he himself hints, and there are potentially many ways to avoid it — for example, contra Guth's preferred model, it may be that inflation eventually stops, cf. Hawking & Hertog, 2018, and thus that each point in a pocket universe's timeline will have equal density in the end; or it might be that inflationary models are not actually right after all.

That said, one could still argue that the implication Guth explores — which is potentially a consequence of a wide variety of (eternal) inflationary models — is a weak reason, among many other reasons, to give more weight to short-term stuff (after all, in EV terms, the enormous rate of universe generation suggested by Guth would mean that even extremely small credences in something like his framework could still be significant). And perhaps it's also a weak reason to update in favor of thinking that as yet unknown unknowns will favor a short(er)-term priority to a greater extent than we had hitherto expected, cf. Brian Tomasik's discussion of how we might model unknown unknowns.