This means that merely achieving orbit would be approximately as difficult as launching a probe on a Hohmann transfer orbit to Mars is. (Except that such a launch vehicle would need nearly twice the thrust/weight, cutting down the mass ratio even further.) It is not unreasonable to think that a species on such a planet would have never seriously developed space travel.

To head off the common rebuttal of "maybe they wouldn't have any interest in it," with more advanced technology smaller and smaller groups of individuals would be capable of instituting such a project, to the point where any high school kid with a synthetic biology kit and some toy rocketry kits could colonize the entire universe (owing to relativistic effects). You'd have to assume their society underwent some kind of massive convergence of social norms away from any individuality such that no few members of their species ever had both the capability and desire.

The entire plan is mostly laid out by: http://www.tedxvienna.at/watch/why-aim-for-the-stars-when-th...

Progress is the exception, not the rule, so far in human history.

You're either cherry-picking your intervals or have a very weird definition of "progress".

If you don’t stick with Hydrogen Carbon Nitrogen Oxygen you’re going to have a much harder time finding what you need to grow on earth. For extra solar stuff even those might be hard to find.

If you do stick with HCNO it's hard to get a leg up on nature without simply making a few minor improvements which has limited value outside specific situations. There are also a lot of tradeoffs with binding energy etc.

1.https://en.wikipedia.org/wiki/Zoo_hypothesis

2.http://www.odditycentral.com/travel/north-sentinel-island-th...

If they took 100 years to get to the next star system 5-ly away and then 500 years to populate that system enough to start a new colonization, that's just ("just") 168,000 years to be here. Given a 2 billion year head start, that's easy.

Cathedral building in the middle-ages was a multi-generational 80+ year affair and some of the Pyramids took even longer IIRC. So societies were/are definitely capable of working on ~100 year missions :)

Maybe a generation ship needs to have some sort of 'cathedral-in-the-sky' religion connotation in order for us to commit to building it. Sounds like an interesting idea for a sci-fi plot!

But we've only been working on that for a few decades. 2 billion years is a lot longer. If there is a civilization there at all, it's extremely improbable that it hasn't figured out how to do exploration on a scale of thousands of light-years.

I suspect that's unlikely, even if there were advanced life there for 2 billion years.

Why do you think so? "Continuity" doesn't have to be having the same government or the same political structure, or even the same physical form (the article itself talks about uploads and nanomachines). It just means continuity of technological development. It doesn't have to mean steady progress either; our civilization hasn't had that, yet in ten millennia or so we have progressed from basic agriculture to space travel. For this planet, we're talking about two million millennia, or 200,000 times the time we've had. All the variables we've observed in our civilization's history become rounding error on that timescale.

Perhaps no civilization of any sort has ever developed there. Maybe conditions on the planet are inhospitable, perhaps evolution simply never went that way. I think people tend to assume that evolution naturally leads towards more intelligent creatures, but that's not true. Humans are a very very recent development on our planet, in geologic time scales, and our early existence was pretty improbable.

Perhaps civilizations have existed there, but never achieved technological advancement. There are still tribal civilizations on Earth that are using 50kya technology; there's no guarantee that a civilization must develop science and technology.

Perhaps it has had civilizations with similar technological advancements to our own, but they have been destroyed or set back by any of a number of things: extinction-level impact events (could easily happen to us), disease, warfare, or resource shortages. Maybe, for some reason, they never developed easy access to a high density fuel; imagine if humanity had tried to go directly from steam engines to nuclear or solar power because oil didn't exist or wasn't easy enough to find or its significance was never understood.

Perhaps they reached a level of technological advancement far, far superior to our own, but they never made an effort to explore the cosmos. The vast majority of people on Earth right now don't see any point to even exploring other worlds in our own solar system; that mindset could easily dominate for the rest of mankind's existence. Maybe we assume that there is some kind of shortcut around the speed of light and there isn't and, no matter advanced a civilization gets, there simply aren't enough volunteers for a 10,000-year journey to another tiny little planet that may or may not harbor life.

Perhaps all of these are wrong, but they simply visited Earth a million years ago and found it to be entirely uninteresting and haven't been back since. Maybe their civilization has even ceased to exist, and our civilizations will never ever cross paths because we missed eachother by a few minutes in geologic time.

I'm generally optimistic about the chances of advanced civilizations elsewhere in our galaxy, even relatively close by, and entirely pessimistic about our odds of ever being able to interact with those civilizations in any meaningful way.

Or that the distances and difficulty of transporting anything very large or complex between star systems turns out to be just too great of an engineering problem for any life form. The energy required to move a life-sustaining amount of mass between stars is mind-boggling huge and beyond our own technological capabilities for the foreseeable future ( we only anticipate interstellar life is a possibility by assuming our technological growth curve will continue unimpeded and then guessing there's life out there further along tha us, which may not be accurate or possible).

Or that they are indeed spreading but doing it in a way undetectable to our technologies we're looking with and we just didn't come up lucky enough to be directly contacted by them in their spread (yet?).

Or maybe they developed a Matrix-like utopia, a self-maintaining and long lasting support system and stopped outward appearing progress?

Or going in another direction, perhaps we really are inside a simulation and $life_bearing_planet is set to 1.

The hypotheticals are nearly endless and not necessarily due to overtly negative outcomes.

I wouldn't have expected every possible situation to have occurred given the finite history of the universe.

But I really have no idea what I'm talking about, so my request is serious.