You should add a link to the previous post at the top, so people who come across this don’t get confused by the sand metaphor.
This will hopefully be addressed in later posts, but on its own, this reads like an attempt to legislate a definition of the word ‘scarcity’ without a sufficient justification for why we should use the word in that way. (It could also be an explanation of how ‘scarcity’ is used as a technical term in economics, but it is not obvious to me that the alternate uses/unsatiated desires distinction is relevant to what most economists spend their time on. If this is your intention, could you elaborate and give evidence that economists do in fact use the term in this way?) Naively, it seems that if we have enough Star Trek replicators or whatever to satiate all human desires, then for all practical purposes scarcity has been eliminated, and insisting that it hasn’t really because things have alternative uses because some things still have alternative uses seems like playing unproductive word games. Can you explain why thinking of scarcity in your terms is advantageous?
Overall, this series has so far been quite fun to read. I look forward to more.
You cannot possibly gain new knowledge about physics by doing moral philosophy. At best, you have shown that any version of utilitarianism which adheres to your assumptions must specify a privileged reference frame in order to be coherent, but this does not imply that this reference frame is the true one in any physical sense.