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I'm actually more interested in if there was ever some sort of extraterrestrial outpost on this planet in the past 1 billion years or so. At that time scale, e

I'm actually more interested in if there was ever some sort of extraterrestrial outpost on this planet in the past 1 billion years or so. At that time scale, exploring the entire galaxy seems reasonably practical. And stopping here to refuel and recuperate, not so unlikely, at least to me.

human20190310 7y ago
Wouldn't it make more sense to acquire fuel from bodies with weaker gravity, so that you don't have to burn as much of it to get the rest back into space?
- Zhenya 7y ago
  You're assuming they didn't have an anti-gravity engine
  - krapp 7y ago
    They didn't, because anti-gravity is not a technology that can actually exist.
    - human20190310 7y ago
      Why not?
      - krapp 7y ago
        Like FTL, nothing in physics as we understand it, or that we've observed in the universe, allows for even the possibility of anti-gravity. Theories always require some magical fudge-factor like "negative mass" that, as far as we know, don't really exist either, and can't apply to our universe. As far as is known, the only way to generate gravity is mass, and the only way to counteract gravity is to push against it in the other direction hard enough, but that's just rocketry.
  - vardump 7y ago
    Then they would just use anti-gravity engine near any sufficiently massive body and generate as much energy out of nothing as they wanted...
Noos 7y ago
It's possible that the kind of extraterrestrial beings that could do any form of FTL travel wouldn't even think in terms of "outposts" or "refuel." The task is so immense that any technology capable of doing it would belong to a society that would be gods to us. You're treating it like it would be them cruising route 66, but for them, it could be something like us browsing a web page or even just dreaming. I dream I want to be on earth, and here I am. A lot of SF is really bad in they assume people will be the same and just drive to different galaxies instead of drive to different states. But the technology between the two is so huge that to get there would probably entail a whole host of things that would transform them into something above us as mayflies are to us. Not sure we'd even be able to tell if they left anything or even stopped by.
- javajosh 7y ago
  You don't need FTL to explore the entire galaxy in 1B years. The Milky Way is only 100k ly across, so your fleet would only need an average speed of .1c to see it all. E.g. a robot fleet with a program to "see all parts of the galaxy" would colonize, refuel and rebuild another fleet, and send it off to repeat, and easily reach the entire galaxy. (The tech we're missing is a way to turn solar power into anti-matter, then power your ships with slow trickle matter/anti-matter annihilation.)
- simonsarris 7y ago
  Your last sentence is the premise of the novel Roadside Picnic
- repolfx 7y ago
  Possible - sure. But the default state should be to assume FTL aliens would need to refuel. Consider human civilisation circa 3000 years ago. People moved around on horses, with carts. Roads were usually poor or non-existent. We are incomparably advanced compared to back then. But: • They had outposts for travellers and we have airports. • They had to feed their horses, we have to refuel planes. • They needed infrastructure to establish new towns and colonies. We do too although the Earth being inconveniently full of cities often hides this fact. Whilst the technology has changed enormously the fundamentals of travel and colonisation haven't. If there's no refuelling process at all ever then that implies a violation of the conservation of energy laws anyway - even if you only refuel once when a ship is newly built with some incredibly long lasting energy source, that's still fueling.

human20190310 7y ago

Wouldn't it make more sense to acquire fuel from bodies with weaker gravity, so that you don't have to burn as much of it to get the rest back into space?

Zhenya 7y ago
You're assuming they didn't have an anti-gravity engine
- krapp 7y ago
  They didn't, because anti-gravity is not a technology that can actually exist.
  - human20190310 7y ago
    Why not?
    - krapp 7y ago
      Like FTL, nothing in physics as we understand it, or that we've observed in the universe, allows for even the possibility of anti-gravity. Theories always require some magical fudge-factor like "negative mass" that, as far as we know, don't really exist either, and can't apply to our universe. As far as is known, the only way to generate gravity is mass, and the only way to counteract gravity is to push against it in the other direction hard enough, but that's just rocketry.
- vardump 7y ago
  Then they would just use anti-gravity engine near any sufficiently massive body and generate as much energy out of nothing as they wanted...

Noos 7y ago

It's possible that the kind of extraterrestrial beings that could do any form of FTL travel wouldn't even think in terms of "outposts" or "refuel." The task is so immense that any technology capable of doing it would belong to a society that would be gods to us. You're treating it like it would be them cruising route 66, but for them, it could be something like us browsing a web page or even just dreaming. I dream I want to be on earth, and here I am. A lot of SF is really bad in they assume people will be the same and just drive to different galaxies instead of drive to different states. But the technology between the two is so huge that to get there would probably entail a whole host of things that would transform them into something above us as mayflies are to us. Not sure we'd even be able to tell if they left anything or even stopped by.

javajosh 7y ago
You don't need FTL to explore the entire galaxy in 1B years. The Milky Way is only 100k ly across, so your fleet would only need an average speed of .1c to see it all. E.g. a robot fleet with a program to "see all parts of the galaxy" would colonize, refuel and rebuild another fleet, and send it off to repeat, and easily reach the entire galaxy. (The tech we're missing is a way to turn solar power into anti-matter, then power your ships with slow trickle matter/anti-matter annihilation.)
simonsarris 7y ago
Your last sentence is the premise of the novel Roadside Picnic
repolfx 7y ago
Possible - sure. But the default state should be to assume FTL aliens would need to refuel. Consider human civilisation circa 3000 years ago. People moved around on horses, with carts. Roads were usually poor or non-existent. We are incomparably advanced compared to back then. But: • They had outposts for travellers and we have airports. • They had to feed their horses, we have to refuel planes. • They needed infrastructure to establish new towns and colonies. We do too although the Earth being inconveniently full of cities often hides this fact. Whilst the technology has changed enormously the fundamentals of travel and colonisation haven't. If there's no refuelling process at all ever then that implies a violation of the conservation of energy laws anyway - even if you only refuel once when a ship is newly built with some incredibly long lasting energy source, that's still fueling.