> think it's hard to know how far along they were the first time they visited It doesn't really matter. The difference in human technology over the past 100 ye

> think it's hard to know how far along they were the first time they visited It doesn't really matter. The difference in human technology over the past 100 years is night and day. Even a thousand years is likely to be incomprehensibly advanced relative to where we sit. If you choose a random point in time to start a civilization, the likelihood of choosing a point in time within 1,000 years is 1,000 / ~14,000,000,000 for the timescale of the universe or 1,000 in 4 billion by the age of the earth for a more conservative estimate. Naively, you would expect a random space civ to have a couple billion years head start on earth. Do we really think there's going to be noteworthy technological advancements between years 2,000,000,000 and 2,000,000,005? I think not. Civs habitually going extinct could avoid this, but this becomes much harder for civs with intergalactic travel.