we have come to see those as similar, except that my notion of diversity is over space while my friend's notion of novelty is over time. notably, the two can be distinguished by the following experiment:
a planet right now contains 10 quite different cultures. you get to choose which of the two possible future states it will go in:
if it makes a difference: other values are the same, all cultures mentioned here are reasonably non-evil and all about equally "good", you won't ever get to interact with that planet or see their culture yourself, and this planet will not exist after experiencing the selected future — the only two real times at which it's instantiated are its present state, and the future you pick.
a space-diversity perspective compares the two future states and says: "10 > 3, so i pick the first future, it is a present state with more diversity".
a time-novelty perspective, however, compares the two timelines and says: "10 < 10 + 3, so i pick the second future, it is a timeline experiencing more total diversity".
i wonder if there is a more generalized notion of diversity that doesn't care about time vs space, and if i value that one instead of space-diversity. another difficult question is: what about diversity between parallel universes or bubbles ?
time is still weird, huh.