[hdgvhicv]

How can a galaxy spanning civilisation fail. If life can spread to other worlds, unless you get FTL, how could you end all life in a galaxy

As such it seems impossible for life to have reached interstellar travel anywhere in the Milky Way before at most a few million years ago, otherwise we would see it.

Which is weird because life surely can’t be that rare in the entirety of space time.

Of course the galaxy could be teaming with non interstellar life, but once you reach mankind’s level of sentience and technology it dormant seem a massive jump to interstellar, and once that happens there’s no way to put the genie back in the bottle.

[DFHippie]

Though there is likely life throughout the galaxy, it's probably difficult for one sentient spacefaring race to find another habitable planet they'd be comfortable on, i.e., one with a similar atmosphere and mass. If it's a long way from your planet to another you'd care to set foot on, you're left with lots of space stations. But who wants to live in that precarity?

[hdgvhicv]

The main requirement is energy. From stars. Our system has a star, and thus is a resource to be tapped.

Without FTL you don’t get a single civilisation, so even if one civilisation doesn’t rant to expand evolution will mean the ones that do will do so.

So you’re left with “they haven’t tapped our star yet” or “nothing can reach us”

[mike_hock]

1.) It's definitely a giant leap from current technology to interstellar colonization.

2.) Other civilizations even in the nearest solar system would basically be impossible to detect. Even in our own solar system, there could be millions of undetected spacecraft right now. They're simply too small to see. To be detectable, they'd either have to be massive and massively disruptive, like Dyson spheres, which are and most likely will forever remain pure fiction, or they'd have to happen to use radio for communication.

3.) There are good reasons for them not to be using radio for communication. They might have discovered a different physical phenomenon that allows them to communicate in ways we can't detect. Or they might not be as reckless as humans and don't want to broadcast their presence and activity to completely unknown and potentially hostile other species.

[hdgvhicv]

Not compared to the leap from something as advanced as pyramid building to today, let alone the advancement in the last 100,000 years

Any life form will expand to use all resources. We know that nothing is consuming all resources in our solar system.