I think you might not have clocked the OP’s comment that the morally relevant being as just those that exist whatever we do, which would presumably rule out concerns for lives in the far future.*
What I tried to say is that the spacetime of the universe(s) may contain a vast number of sentient beings regardless of what we do. Therefore, achieving existential security and having something like a Long Reflection may allow us to help a vast number of sentient beings (including ones outside our future light cone).
**Further pedantry: if our actions changed their children, which they presumably would, it would just be the first generation of extraterrestrial visitors who mattered morally on this view.
I think we’re not interpreting the person-affecting view described in the OP in the same way. The way I understand the view (and the OP is welcome to correct me if I’m wrong) it entails we ought to improve the well-being of the extraterrestrial visitors’ children (regardless of whether our actions changed them / caused their existence).
What I tried to say is that the spacetime of the universe(s) may contain a vast number of sentient beings regardless of what we do. Therefore, achieving existential security and having something like a Long Reflection may allow us to help a vast number of sentient beings (including ones outside our future light cone).
I think we’re not interpreting the person-affecting view described in the OP in the same way. The way I understand the view (and the OP is welcome to correct me if I’m wrong) it entails we ought to improve the well-being of the extraterrestrial visitors’ children (regardless of whether our actions changed them / caused their existence).