> aggressive, exponential expansion is a fairly valid Darwinian strategy. Earth exists for around 4.5 billion years, life on Earth for 3.5 billion years, the w

> aggressive, exponential expansion is a fairly valid Darwinian strategy. Earth exists for around 4.5 billion years, life on Earth for 3.5 billion years, the whole known Universe just less than 14 billion years (and we can send some small probes to the limits of our own Solar system only during the last decades). So the Universe is not "old" and the distances between the areas suitable for the life to "expand" are immense and real barriers. Knowing the distances involved, I believe that had we discovered that we are in much later age of the Universe, not seeing "others" would mean more than it means now. For now, knowing the distances, whatever could be somewhere far could simply be too far from us, nothing more. Edit: Re: "The galaxy is only 100,000 light years across" note that that are the light years -- the distance that the light has to travel that much. We know that the whole islands on Earth were unreachable for many otherwise common species for millions of years. But these distances are nothing compared with problems of maintaining complex life over the cosmic distances and in the cosmically hostile environment. Also "10-50 million years ahead of us" doesn't have to mean what we think it could mean. For a context, the dinosaurs were, historically, 60 million years "ahead of us". Nobody can "just assume" the we will cross the limits that are ours limits now. Biologically, we did multiply "exponentially" as soon as we were able to use the natural resources to do so (1). But apart from that (the certainty of life using available resources for biological growth), the growth in technical capability for interstellar travel is not guaranteed. Not to mention that the resources are by definition limited. So nobody should ask "why aren't others here" when we can't even claim that we reached somewhere else. What we surely can ask is "why don't we get some signals" because, for example, we are able to send a radio message, but I personally wouldn't assume that the other civilizations make such kind of intentional signalling that we must necessarily be able to detect, being where we are now. It's not "just connect the headset to the wire and a crystal and listen." It's something that has to concentrate immense amounts of energy to reach exactly us. At the moment it's not "is there anybody anywhere" but "is there anybody in the conveniently close neighborhood who's capable to send exactly what we expect to receive, and, most probably, to target exactly in this direction." It's immensely hard to even "see" the planets by the closest stars, that how far everything is. I think that probability for that "targeted messaging" is too low, not to mention that I don't think that the "intelligence" in our sense is inevitably happening on every planet -- we know that from the 3.5 billion years of life on Earth, not even plants existed for 3 billion years. Life can indeed be relatively common but the development that the Earth up to now had could still simply be uncommon enough. 1) https://ourworldindata.org/grapher/world-population-since-10000-bce-ourworldindata-series https://ourworldindata.org/grapher/world-population-since-10...