Astronomical Waste Given Acausal Considerations

October 27, 2025

[speculative draft]

Bostrom's original astronomical waste argument is as follows:

1. Consider all stars in the Virgo supercluster.
2. Now consider the total number of digital humans simulatable with the energy stored in these stars, given that the energy is harvested with technologies currently assessed to be feasible.
3. This provides a lower-bound on the potential value lost per-unit-time, assuming an ethical stance at least somewhat similar to an aggregative total utilitarian.
4. This is a lot of value per-unit-time.
5. Correspondingly, existential risk poses a threat so large it dominates all other considerations, as it eliminates the possibility of human colonization.

This model is static. In particular, it does not consider dynamism in the size of the actualizable universe. By restricting to the local supercluster, one ignores the potential resources of the stars beyond, including those turned inaccessible by cosmological expansion. For the purposes of establishing a conservative bound on the potential value left on the table, these are nitpicks are minor. However, when assessing the tradeoffs between safety-focused and progress-focused policies under various ethical viewpoints, they matter.

Obviously, the natural extension is to introduce models of spacefaring civilizational expansion and develop more quantitative estimates of "median"-case spatial diffusion under reasonable hypotheses. This analysis would be informative and useful. I will not be pursuing it further in this post.

Rather, I am interested in a more esoteric setting. Acausal bargaining strategies give agents the ability to influence universes beyond their traditionally considered scope (e.g. the lightcone) by independently considering and instantiating the values of agents who would, given their value instantiation in our world, take actions in partial accordance with our values in theirs. A "coalition" then forms between agents who engage in this reciprocal trade.

What properties might this coalition have?

• It is composed of agents who care about their values being instantiated across the space of universes the agents in the coalition occupy. These agents then likely have values which are universal.
• It is composed of agents whom are sufficiently cognitively advanced to reason in similar thought-patterns to the ones described. Given that human understanding is at a nascent stage, this puts a rough lower bound on capability.
• The coalition is necessarily composed of agents which are willing to trade with us.
• [other properties that can likely be gleaned by a mind with more intelligence than mine]

These are local properties, in that they are agent properties which then place some constraints on the environments the agents find themselves in. They are not global properties (constraints on the laws of physics of the relevant universes). Our reasoning about the space of acausally-influencable universes via acausal bargaining is thus necessarily agent-centric.

Under these considerations, the actualizable universe of a member of a given coalition is the union of the causally-actualizable universes of the members of the coalition. Astronomical waste concerns would then occur whenever considering actions or inactions leading to a decrease in the size of the actualizable universe.

What actions or inactions would affect the size of the actualizable universe? It's difficult to come up with a natural conception of global temporality in this setting: local constraints on agent environments tell us little about what stage of the cosmological lifetime the agent exists in. Interpreting temporality within a member's lightcone is easier: waiting to implement acausal bargaining strategies leads to a loss of value-bargaining-power, given that the size of the member's causally-actualizable universe decreases in accordance with classical astronomical waste arguments.

It is tempting to say that this loss is massive, much more massive than the temporal loss associated with one's own causally-actualizable universe. I refrain from claiming this strongly because I do not have a good understanding of what bargaining strategies within an acausal coalition look like. Finnveden's Asymmetric ECL and Treutlein's Modeling evidential cooperation in large worlds are good places to look to star thinking about this. (Dai makes the argument that it seems like our universe is pretty small, so it stands to reason there's much more to be gained via acausal trade.)

[even more speculative]

It is also possible that a multiplicity of coalitions is induced by agents throughout the multiverse having conflicting values. Given the aggregative tendency to ensure value-lock-in for successor agents, it is potentially the case that coalitional lock-in at the civilizational level occurs shortly after knowledge of basic acausal bargaining strategies. It is not insane to assume heterogeneity in size of the coalitional actualizable universes. Implying that large sources of astronomical waste may come from choosing incorrectly, or joining coalitions of less size.

[I note that it is possible the notion of an "acausal coalition" is flawed and in fact acausal trades are not closed in this manner---A can trade with B and B can trade with C while C might not be able to trade with A.]

[TODO: introduce bargaining models, quantify classical astronomical waste in the spatial setting, quantify universe "smallness" under variety of cosmological models]