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Comment by PaulHoule | Hacker News Reader

I wonder if the inner solar system is a ghetto.

If the base requirement for life is liquid water, then it is a generic property that you find it in most moons and dwarf planets, usually driven by pressure and geothermal or tidal energy. If the under layer is rock instead of ice you could have thermal vent economies like we have in ocean rifts.

In comparison the Earth is a really dry place, the most special thing about it is that the plants support an oxygen economy that might not be necessary for complex life but it sure helps.

Any species that masters interstellar travel is going to know how to cut up something like Ceres or Pluto into hundreds of thousands of miles of shopping malls and apartment buildings and might not find inner solar system bodies that interesting. In fact they might not even have an off-the-shelf landing vehicle that would work on Earth and might spend a few years developing one.

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It’s very difficult to tell what environment ‘typical’ aliens evolve in. It seems like Earth is probably a very unusual planet, mainly due to our very large moon which has stripped away so much of our atmosphere. Most planets our size will have atmospheres much more like that of Venus in terms of density at least. Smaller planets might develop atmospheres like ours in terms of density, as Mars did, but won’t be able to retain them for long.

Even a modest increase in Earths gravity, or significantly denser atmosphere would make reaching orbit unviable. I also don’t see how life evolving in liquid voids on outer planet moons, or similar environments, could develop much beyond simple invertebrates or equivalent.

I’m really despairing that spacefaring civilisations are at all likely. Life yes, I think it’s likely to be reasonably common at the galactic level. Intelligent life, sure. But I think we’re fantastically lucky to be in the situation we find ourselves. I know statistics says we’re supposed to most likely be typical, but random chance doesn’t care about how many possibilities didn’t show up. If a lottery has a winner, that ticket won just as much no matter if there were 10 losers or a billion of them.

Agreed. When I learned that bit about the rocket equation and gravity - that just a little more gravity would make all known rocket tech unable leave Earth's atmosphere/gravity - my thoughts of life zipping around the universe dimmed greatly. Maybe we should look at it as our duty to devise ways to 'rescue' other biomes from their gravitational jails? (if only we weren't space orcs.)

I've always thought something like the Skyhook described in Seveneves by Neal Stephenson would be perfect for lifting things off of high gravity worlds where the rocket equation is a deal breaker, provided you were starting in orbit or outside of the gravity well:

https://news.ycombinator.com/item?id=17900992

Maybe the materials science would still be a deal breaker, but in theory it would be easier to build than a space elevator.

Huh, very interesting. Yes, I wonder where current materials engineering puts us for a maximum length cable. It might be usable to just fly a plane up to it at some point. This also brings to mind capturing an asteroid in LEO. (Surely super dangerous though.)

I can't help but think SpaceX and the rest of us are missing out by targeting places like the moon or mars when there are so many asteroids out there. Maybe some of them could be used as a space station or slowly morphed into a spaceship with higher mass than we could ever launch? (like 1036 ganymed)

If we ever start really living and working in space it seems like we might reach a point where going down into deep gravity wells like Earth or even Mars will be too expensive to be worth it most of the time.

Just because traditional combustion engines can't do it doesn't mean much. More powerful nuclear thermal engines, direct fusion engines, etc are in development. There's other possibilities.

That’s true to a point, but it’s undeniable that as the cost of space technology increases the odds of bothering with it fall, and that the relatively modest changes in the conditions have exponential impact on the costs. A small increase in gravity rules out chemical rockets. Yes nuclear rockets might still be viable at that point, but increase gravity a bit more, or atmospheric density, and those become unviable too. And so it goes. The point is the range of conditions in which space tech is viable is very narrow compared to the range of possible conditions a species might find itself in.

It’s amusing how we are so improbable yet here we are. It’s like in novels where the book starts at an interesting environment for the protagonist. I often think “this is all pretty unlikely”. But it’s fun for the story and the story is about a protagonist in such a situation so it all works and as readers we can usually suspend disbelief. A similar principle applies to humans. We are incredibly improbable yet here we are doing our thing. I like to imagine other alien civilizations encountering us some day and marveling at how unlikely we are (and they are).

The fact that we find ourselves in such an incredibly unlikely situation, on a planet that seems perfectly designed to harbor life, is probably the best argument for the existence of a higher power.

I can see how that is attractive to people who believe in a higher power, but it’s really a terrible argument because it has no actual explanatory power. Exactly the same argument is used to justify various forms of multiverse for example - more rolls of the dice on types of universe equals a greater chance of us turning up. All it really means is ‘there must be a reason’, but it says nothing about what that reason is. Anything beyond that is just projection.

It's true that such an answer doesn't give any meaningful explanation by itself. But it can motivate us to somehow search for this higher power. I think the Voyager Golden Record is an example of such an action on behalf of mankind.

This is something that, I think, we all intuitively feel. The big question is: what is the nature of this "higher power"? Is it something external or related to our consciousness?

I think the other way theologically. If you think "God is Great" the majestry of creation known to astronomers is much greater than the theory that earth is 6000 years old and then Adam blew it.

Thus "the Lord has many mansions" and one would expect creativity to be generic in the universe.

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