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Fascinating. This may weigh down the Drake equation, particularly in reducing the average time civilizations survive on planets with high gravity because their

Fascinating. This may weigh down the Drake equation, particularly in reducing the average time civilizations survive on planets with high gravity because their ability to become multiplanetary and survive great filters is limited.

anonymouskimmer 3y ago
One of the biggest hypothetical great filters is massive war. Higher engineering requirements for rockets (or even simple projectiles such as cannons or arrows) would set limits on the rate of increase of warfare technology. It's possible other means of diplomacy would advance at sufficient speed to preempt population annihilation from global war. I'm curious what effect an increase of gravity may have on heavier-than-water displacement craft (canoes and other modern boats). I think probably none, since you're dealing with density, not weight. Except for any increase in density of early building materials and cargo/supercargo. But it's been long enough from physics I'm unsure. I think atmospheric density is more dependent on magnetic field than gravity.
- datameta 3y ago
  Buoyancy is indeed not affected by gravity, you're correct.
  - bugbuddy 3y ago
    This is technically wrong. Increase in gravity does affect buoyancy because air density changes with gravity. The reason is that the column of air above you is compressed by gravity. With very large gravity, all the atmosphere could be compressed down to possibly a few km.
  - antod 3y ago
    Depends how compressible the fluid you're floating in is right? Note that's 'fluid' rather than just liquid. As you increase gravity, with fully compressible fluids the buoyancy scales the same as weight, you wouldn't sink lower. But with any incompressibilty you'd need to displace proportionally more (ie sink down more) to counter the increasing weight. (I think)
    - Intralexical 3y ago
      > But with any incompressibilty you'd need to displace proportionally more (ie sink down more) to counter the increasing weight. The water would also weigh more. Buoyancy is the force of the water around the volume you displaced being pulled down into that space, exerting pressure that pushes you up. So you'd float just as well. Actually, the compressible fluids would become denser, and make it easier for you to float (assuming you're relatively incompressible). At the extreme end, you could swim in pressure-liquified air (assuming you survive being crushed, of course).
  - datameta 3y ago
    Replies are accurate (more precise?), it is more true to say that buoyancy in a virtually incompressible liquid is not affected by gravity because even if gravity is increased, the water experiences it the same as the buoyant mass.
- wolfram74 3y ago
  The thing I often think about is while the demands for an orbital class vehicle quickly become untenable, ICBM's stay viable for a lot longer. I don't know if MAD is more or less stable without the prospect of space exploration.
  - nine_k 3y ago
    I would argue that situation is usually more stable with less secrecy, so a lack of spy satellites would not be beneficial. Absence of comm satellites would also help fragment the world and make the idea of a surprise attacks more enticing.
    - Aeolun 3y ago
      Not beneficial, but I imagine you’d just see a lot more spyplanes.
      - nine_k 3y ago
        Spy planes can be shot from the ground, or with another plane. This is closer to an act of hot war :( Orbital space (around modern Earth) is ex-territorial, so killing a spy satellite would be seen as an act of aggression, not legitimate defense. This holds back "kinetic action" in near-Earth space.
        eru 3y ago
        > Orbital space (around modern Earth) is ex-territorial, [...] That's a historical accident of arrangements on earth (so less useful in the Fermi-paradox / filter debate), and could easily have gone differently. Ie air space could also have been seen as ex-territorial.
        wolfram74 3y ago
        Assuming something like air space territories in these other cultures, extending them out to infinity seems... tricky. Wouldn't it imply that the ownership of various celestial bodies changes with time? My recollection of how it evolved on Earth was the soviet's more asked forgiveness than permission and eisenhower basically shrugged and said "whatever, at least our spy satellites can go over you too"
- hermitcrab 3y ago
  >I think atmospheric density is more dependent on magnetic field than gravity. Atmospheric density is very much affected by gravity. I'm not sure magnetic field has any appreciable effect at all on the density of the earth's atmosphere. Why would it? The vast majority of the atmosphere isn't charged, so doesn't interact directly with magnetism.
  - slavboj 3y ago
    Magnetic field protects from solar wind that strips atmosphere.
    - outofpaper 3y ago
      It's often said but with heavy evidence to yhr contrary e.g. Venus. Venue's negligible magnetic field is almost non-existent yet its atmosphere is many many times thicker than ours.
      - idiotsecant 3y ago
        In fact, earth actively loses material to space because is has a magnetosphere, polar outflow of oxygen for example.
        kijin 3y ago
        Venus loses a lot of material, too. One of the reasons Venus still has a dense atmosphere is because its atmosphere is mostly composed of a relatively heavy compound, CO2, which is harder to lose than lighter gases like H2, N2, and O2.
    - hermitcrab 3y ago
      If you turned off the earth's magnetic field today, then presumably the atmosphere would be gradually stripped, away over millions of years. Similar to what happened to Mars. But it would not make any immediate difference to the density.
- unsupp0rted 3y ago
  War may be the exception, not the rule. Just because we're built for it doesn't mean other species will be. If evolving in a different environment, they might be built for cooperation. That is, in a certain environment the only species that can evolve enough to go interplanetary might be a species that learned to co-exist internally and externally, otherwise the environment would have kept them down.
  - Intralexical 3y ago
    > War may be the exception, not the rule. > Just because we're built for it doesn't mean other species will be. You heard of what chimps get up to? Ants? Microbes? They don't just have wars; They have raiding parties, take slaves, serve as battlefield medics, compete in intrafactional and interfactional rivalries that slowly boil over… Hell, even trees actively release toxins to try to kill other nearby plants. On a long enough timescale, war is almost certainly highly (and lethally) maladaptive. But in a non-post-scarcity environment with social contact, creatures whose bodies disagree with entropy tend to learn that violence is an effective tactic for taking others' calories/oil and nutrients/minerals. Maybe there's exceptions. I hope so, anyway.
    - unsupp0rted 3y ago
      All those species evolved on the same planet, with the same constraints. War works well for them, so they evolved to get better and better at it. But war is resource-intensive and costs lives. Lives are easily replaced on Earth. It’s not hard to imagine a planet where going to war would be mutually assured destruction on a species level, even for ants and microbes.
      - Jensson 3y ago
        > It’s not hard to imagine a planet where going to war would be mutually assured destruction on a species level, even for ants and microbes. That is very hard to imagine, how do you reckon that would be possible? Does the planet only support a couple of anthills and then all resources are consumed? How would ants even appear on such a planet?
- exe34 3y ago
  If you can't shoot them, surely you can keep stabbing them until you develop bio-warfare? Then you can both go extinct and the filter keeps working.
BuyMyBitcoins 3y ago
You may find the concept of Superhabitabilty interesting. The hypothesis suggests that larger planets with more mass and gravity than Earth would be more favorable to life. It’s certainly possible that there is a lot more life out there on planets where getting into space is nearly impossible with conventional chemical rockets. We may be living on a comparatively barren rock, but the tradeoff of that we are actually able to get into orbit. https://en.wikipedia.org/wiki/Superhabitable_planet https://en.wikipedia.org/wiki/Superhabitable_planet
- scotty79 3y ago
  Imagine visiting such planet. They'd think you are gods because, how did you get up there? But you can't really land because it would be one way trip for your tech. So you just hang around and talk with radiowaves, sending them pictures of their world from above they could never see otherwise.
  - eru 3y ago
    Well, you could send remotely controlled probes. And there might be some volunteers for a one-way trip, too. There are certainly volunteers for one-way trips to Mars right now, and by the time humanity would be an interstellar species, our population size would have gone up by several orders of magnitude; so even if volunteers are rarer as a proportion, they would be much more numerous in absolute terms.
  - p-e-w 3y ago
    No advanced civilization would conclude they are dealing with "gods" just because they see someone with presumably better technology than themselves. In fact, if they are anything like humans, they have probably already realized that species that live on a lower-gravity planet could escape that planet using the same chemical reactions that are available to them also.
  - unsupp0rted 3y ago
    Rockets are out, but you could drop a space-elevator line down
brucethemoose2 3y ago
Is this really a big factor? Not being multiplanetary seems like the least of our existential problems here on Earth, and will continue to be that way for awhile. At the same time, chemical rocket efficiency becomes totally irrelevant for a slightly more advanced civilization than us.
- nine_k 3y ago
  You can't build a space elevator before getting to the orbit first. A jet engine capable of leaving a deep gravitational well must have a big ratio of thrust to weight. If a chemical rocket is too weak, a nuclear jet engine is the only remaining option. Would you be comfortable running it in the thick atmosphere of a densely inhabited planet?
  - brucethemoose2 3y ago
    A civilization just a few decades ahead of us is (theoretically) almost unimaginable. Bio augmentation, true AIs, who knows what advances in fundamental physics knowledge... Just to start. What I'm saying is that whatever engineering and environmental limitations we currently perceive are probably irrelevant.
- eru 3y ago
  > Not being multiplanetary seems like the least of our existential problems here on Earth, and will continue to be that way for awhile. That might be true, especially if your 'for awhile' talks about millennia at most. But it's an extremely relevant concern in the context of the Fermi paradox.
awwaiid 3y ago
Yeah, but those evolved on high-gravity planets are smarter (and maybe stronger) since they too must calculate thrown-object trajectories but have to do so faster. Our brains use just enough energy, but no more, to keep us alive. Being smarter than we are would be a waste .... but if we HAD to think faster, we would evolve to match. So maybe they'd figure it out.
- eru 3y ago
  Humans are (nearly?) the only animals that got really into throwing stuff, especially throwing stuff with heft and precision. (As a corollary: you can train seals to balance balls, and apes might through excrement; but only (some) humans can juggle.) If throwing things well had been much harder, perhaps no animal would have ever bothered?
GuB-42 3y ago
The article limits itself to chemical rockets. They work well enough on Earth so that's what we are using, but we can do better. Replace chemistry with nuclear, and use the air in the atmosphere as a reaction mass. On Earth, that would cause more problems than it would solve, that's why we don't do that despite having the tech to do it. But on a higher gravity planet it may be what we would do. Harder, but not impossible. It is interesting how we got nuclear technology that would allow for way more capable rockets at the same time we perfected chemical rockets enough to get to orbit. So much that we could have been able to escape a 10g planet almost as soon as we have escaped Earth.
- eru 3y ago
  If you want to use nuclear technology to get to orbit on a planet with an atmosphere, you pretty much have to use bombs. See https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls... More conventional nuclear propulsion has similar trade-offs to an ion drive: great for long distance travel when you are already in space, but useless to get off a planet.
Intralexical 3y ago
> […] ability to become multiplanetary and survive great filters is limited. So, the known quantities that term refers to tend to be steps more like planetary habitability and abiogenesis, which might prevent complex life from getting established in the first place. But it sounds like you mean some kind of cataclysmic event which wipes out an already existing industrialized civilization. What, specifically, are the "Great Filter" scenarios which being multiplanetary is actually supposed to help with? Supernovas? GRBs? Simple asteroid impacts? You can usually see those coming from millions of years in advance. And surely building a couple layers of solar sail material to shield the planet, stockpiling ozone generators to repair the damage quickly, gently nudging the asteroid, or simply digging some holes/eating a gas giant and weathering the storm, would be easier and save vastly more people than establishing a sizable population in another star system. The other "Great Filter" idea which seems to be memetically adapted for proliferating in modern discourse is the idea of a locust-like swarm of technologically advanced aliens that kill any industrial civilizations which do emerge. But in that case, presumably settling multiple star systems is the opposite of what you'd want to do; You'd be better off quieting your emissions to shrink your footprint than spreading even more biomarkers around at high blueshift. Frankly, I think this entire idea of needing to "become multiplanetary and survive great filters" is more mainstreamed now largely due to one specific individual fancying himself a savior of humanity. SpaceX builds interesting machines, but I liked it better when it was people like Sagan, Aldrin, and Zubrin getting excited about Mars. But even then, I'm not sure if the idea of colonizing more planets in order to survive planet-scale catastrophes really jives with how people think— Plenty of us already live within splash radius of the Pacific Ring of Fire, Yellowstone Caldera, tornadoes, tropical cyclones, land below sea level… and yet there's no billion-dollar emergency backup cities in Antarctica to "make San Francisco into a multicontinental city and survive great quakings".
- ikari_pl 3y ago
  > surely building a couple layers of solar sail material to shield the planet, stockpiling ozone generators to repair the damage quickly, gently nudging the asteroid, or simply digging some holes/eating a gas giant and weathering the storm, would be easier The assumption is that we have a problem getting anything off the planet. All these would require some good rocket engineering. I agree with everything else here a lot.
njarboe 3y ago
Maybe if you can't launch rockets into orbit with chemical rockets then your path to becoming multiplanetary would probably be quicker rather than slower. You would have to develop nuclear rockets (quite doable) and then have a much better tech for exploring the solar system and beyond.

anonymouskimmer 3y ago

One of the biggest hypothetical great filters is massive war. Higher engineering requirements for rockets (or even simple projectiles such as cannons or arrows) would set limits on the rate of increase of warfare technology. It's possible other means of diplomacy would advance at sufficient speed to preempt population annihilation from global war. I'm curious what effect an increase of gravity may have on heavier-than-water displacement craft (canoes and other modern boats). I think probably none, since you're dealing with density, not weight. Except for any increase in density of early building materials and cargo/supercargo. But it's been long enough from physics I'm unsure. I think atmospheric density is more dependent on magnetic field than gravity.

datameta 3y ago
Buoyancy is indeed not affected by gravity, you're correct.
- bugbuddy 3y ago
  This is technically wrong. Increase in gravity does affect buoyancy because air density changes with gravity. The reason is that the column of air above you is compressed by gravity. With very large gravity, all the atmosphere could be compressed down to possibly a few km.
- antod 3y ago
  Depends how compressible the fluid you're floating in is right? Note that's 'fluid' rather than just liquid. As you increase gravity, with fully compressible fluids the buoyancy scales the same as weight, you wouldn't sink lower. But with any incompressibilty you'd need to displace proportionally more (ie sink down more) to counter the increasing weight. (I think)
  - Intralexical 3y ago
    > But with any incompressibilty you'd need to displace proportionally more (ie sink down more) to counter the increasing weight. The water would also weigh more. Buoyancy is the force of the water around the volume you displaced being pulled down into that space, exerting pressure that pushes you up. So you'd float just as well. Actually, the compressible fluids would become denser, and make it easier for you to float (assuming you're relatively incompressible). At the extreme end, you could swim in pressure-liquified air (assuming you survive being crushed, of course).
- datameta 3y ago
  Replies are accurate (more precise?), it is more true to say that buoyancy in a virtually incompressible liquid is not affected by gravity because even if gravity is increased, the water experiences it the same as the buoyant mass.
wolfram74 3y ago
The thing I often think about is while the demands for an orbital class vehicle quickly become untenable, ICBM's stay viable for a lot longer. I don't know if MAD is more or less stable without the prospect of space exploration.
- nine_k 3y ago
  I would argue that situation is usually more stable with less secrecy, so a lack of spy satellites would not be beneficial. Absence of comm satellites would also help fragment the world and make the idea of a surprise attacks more enticing.
  - Aeolun 3y ago
    Not beneficial, but I imagine you’d just see a lot more spyplanes.
    - nine_k 3y ago
      Spy planes can be shot from the ground, or with another plane. This is closer to an act of hot war :( Orbital space (around modern Earth) is ex-territorial, so killing a spy satellite would be seen as an act of aggression, not legitimate defense. This holds back "kinetic action" in near-Earth space.
      - eru 3y ago
        > Orbital space (around modern Earth) is ex-territorial, [...] That's a historical accident of arrangements on earth (so less useful in the Fermi-paradox / filter debate), and could easily have gone differently. Ie air space could also have been seen as ex-territorial.
        wolfram74 3y ago
        Assuming something like air space territories in these other cultures, extending them out to infinity seems... tricky. Wouldn't it imply that the ownership of various celestial bodies changes with time? My recollection of how it evolved on Earth was the soviet's more asked forgiveness than permission and eisenhower basically shrugged and said "whatever, at least our spy satellites can go over you too"
hermitcrab 3y ago
>I think atmospheric density is more dependent on magnetic field than gravity. Atmospheric density is very much affected by gravity. I'm not sure magnetic field has any appreciable effect at all on the density of the earth's atmosphere. Why would it? The vast majority of the atmosphere isn't charged, so doesn't interact directly with magnetism.
- slavboj 3y ago
  Magnetic field protects from solar wind that strips atmosphere.
  - outofpaper 3y ago
    It's often said but with heavy evidence to yhr contrary e.g. Venus. Venue's negligible magnetic field is almost non-existent yet its atmosphere is many many times thicker than ours.
    - idiotsecant 3y ago
      In fact, earth actively loses material to space because is has a magnetosphere, polar outflow of oxygen for example.
      - kijin 3y ago
        Venus loses a lot of material, too. One of the reasons Venus still has a dense atmosphere is because its atmosphere is mostly composed of a relatively heavy compound, CO2, which is harder to lose than lighter gases like H2, N2, and O2.
  - hermitcrab 3y ago
    If you turned off the earth's magnetic field today, then presumably the atmosphere would be gradually stripped, away over millions of years. Similar to what happened to Mars. But it would not make any immediate difference to the density.
unsupp0rted 3y ago
War may be the exception, not the rule. Just because we're built for it doesn't mean other species will be. If evolving in a different environment, they might be built for cooperation. That is, in a certain environment the only species that can evolve enough to go interplanetary might be a species that learned to co-exist internally and externally, otherwise the environment would have kept them down.
- Intralexical 3y ago
  > War may be the exception, not the rule. > Just because we're built for it doesn't mean other species will be. You heard of what chimps get up to? Ants? Microbes? They don't just have wars; They have raiding parties, take slaves, serve as battlefield medics, compete in intrafactional and interfactional rivalries that slowly boil over… Hell, even trees actively release toxins to try to kill other nearby plants. On a long enough timescale, war is almost certainly highly (and lethally) maladaptive. But in a non-post-scarcity environment with social contact, creatures whose bodies disagree with entropy tend to learn that violence is an effective tactic for taking others' calories/oil and nutrients/minerals. Maybe there's exceptions. I hope so, anyway.
  - unsupp0rted 3y ago
    All those species evolved on the same planet, with the same constraints. War works well for them, so they evolved to get better and better at it. But war is resource-intensive and costs lives. Lives are easily replaced on Earth. It’s not hard to imagine a planet where going to war would be mutually assured destruction on a species level, even for ants and microbes.
    - Jensson 3y ago
      > It’s not hard to imagine a planet where going to war would be mutually assured destruction on a species level, even for ants and microbes. That is very hard to imagine, how do you reckon that would be possible? Does the planet only support a couple of anthills and then all resources are consumed? How would ants even appear on such a planet?
exe34 3y ago
If you can't shoot them, surely you can keep stabbing them until you develop bio-warfare? Then you can both go extinct and the filter keeps working.

BuyMyBitcoins 3y ago

You may find the concept of Superhabitabilty interesting. The hypothesis suggests that larger planets with more mass and gravity than Earth would be more favorable to life. It’s certainly possible that there is a lot more life out there on planets where getting into space is nearly impossible with conventional chemical rockets. We may be living on a comparatively barren rock, but the tradeoff of that we are actually able to get into orbit. https://en.wikipedia.org/wiki/Superhabitable_planet https://en.wikipedia.org/wiki/Superhabitable_planet

scotty79 3y ago
Imagine visiting such planet. They'd think you are gods because, how did you get up there? But you can't really land because it would be one way trip for your tech. So you just hang around and talk with radiowaves, sending them pictures of their world from above they could never see otherwise.
- eru 3y ago
  Well, you could send remotely controlled probes. And there might be some volunteers for a one-way trip, too. There are certainly volunteers for one-way trips to Mars right now, and by the time humanity would be an interstellar species, our population size would have gone up by several orders of magnitude; so even if volunteers are rarer as a proportion, they would be much more numerous in absolute terms.
- p-e-w 3y ago
  No advanced civilization would conclude they are dealing with "gods" just because they see someone with presumably better technology than themselves. In fact, if they are anything like humans, they have probably already realized that species that live on a lower-gravity planet could escape that planet using the same chemical reactions that are available to them also.
- unsupp0rted 3y ago
  Rockets are out, but you could drop a space-elevator line down

brucethemoose2 3y ago

Is this really a big factor? Not being multiplanetary seems like the least of our existential problems here on Earth, and will continue to be that way for awhile. At the same time, chemical rocket efficiency becomes totally irrelevant for a slightly more advanced civilization than us.

nine_k 3y ago
You can't build a space elevator before getting to the orbit first. A jet engine capable of leaving a deep gravitational well must have a big ratio of thrust to weight. If a chemical rocket is too weak, a nuclear jet engine is the only remaining option. Would you be comfortable running it in the thick atmosphere of a densely inhabited planet?
- brucethemoose2 3y ago
  A civilization just a few decades ahead of us is (theoretically) almost unimaginable. Bio augmentation, true AIs, who knows what advances in fundamental physics knowledge... Just to start. What I'm saying is that whatever engineering and environmental limitations we currently perceive are probably irrelevant.
eru 3y ago
> Not being multiplanetary seems like the least of our existential problems here on Earth, and will continue to be that way for awhile. That might be true, especially if your 'for awhile' talks about millennia at most. But it's an extremely relevant concern in the context of the Fermi paradox.

awwaiid 3y ago

Yeah, but those evolved on high-gravity planets are smarter (and maybe stronger) since they too must calculate thrown-object trajectories but have to do so faster. Our brains use just enough energy, but no more, to keep us alive. Being smarter than we are would be a waste .... but if we HAD to think faster, we would evolve to match. So maybe they'd figure it out.

eru 3y ago
Humans are (nearly?) the only animals that got really into throwing stuff, especially throwing stuff with heft and precision. (As a corollary: you can train seals to balance balls, and apes might through excrement; but only (some) humans can juggle.) If throwing things well had been much harder, perhaps no animal would have ever bothered?

GuB-42 3y ago

The article limits itself to chemical rockets. They work well enough on Earth so that's what we are using, but we can do better. Replace chemistry with nuclear, and use the air in the atmosphere as a reaction mass. On Earth, that would cause more problems than it would solve, that's why we don't do that despite having the tech to do it. But on a higher gravity planet it may be what we would do. Harder, but not impossible. It is interesting how we got nuclear technology that would allow for way more capable rockets at the same time we perfected chemical rockets enough to get to orbit. So much that we could have been able to escape a 10g planet almost as soon as we have escaped Earth.

eru 3y ago
If you want to use nuclear technology to get to orbit on a planet with an atmosphere, you pretty much have to use bombs. See https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls... More conventional nuclear propulsion has similar trade-offs to an ion drive: great for long distance travel when you are already in space, but useless to get off a planet.

Intralexical 3y ago

> […] ability to become multiplanetary and survive great filters is limited. So, the known quantities that term refers to tend to be steps more like planetary habitability and abiogenesis, which might prevent complex life from getting established in the first place. But it sounds like you mean some kind of cataclysmic event which wipes out an already existing industrialized civilization. What, specifically, are the "Great Filter" scenarios which being multiplanetary is actually supposed to help with? Supernovas? GRBs? Simple asteroid impacts? You can usually see those coming from millions of years in advance. And surely building a couple layers of solar sail material to shield the planet, stockpiling ozone generators to repair the damage quickly, gently nudging the asteroid, or simply digging some holes/eating a gas giant and weathering the storm, would be easier and save vastly more people than establishing a sizable population in another star system. The other "Great Filter" idea which seems to be memetically adapted for proliferating in modern discourse is the idea of a locust-like swarm of technologically advanced aliens that kill any industrial civilizations which do emerge. But in that case, presumably settling multiple star systems is the opposite of what you'd want to do; You'd be better off quieting your emissions to shrink your footprint than spreading even more biomarkers around at high blueshift. Frankly, I think this entire idea of needing to "become multiplanetary and survive great filters" is more mainstreamed now largely due to one specific individual fancying himself a savior of humanity. SpaceX builds interesting machines, but I liked it better when it was people like Sagan, Aldrin, and Zubrin getting excited about Mars. But even then, I'm not sure if the idea of colonizing more planets in order to survive planet-scale catastrophes really jives with how people think— Plenty of us already live within splash radius of the Pacific Ring of Fire, Yellowstone Caldera, tornadoes, tropical cyclones, land below sea level… and yet there's no billion-dollar emergency backup cities in Antarctica to "make San Francisco into a multicontinental city and survive great quakings".

ikari_pl 3y ago
> surely building a couple layers of solar sail material to shield the planet, stockpiling ozone generators to repair the damage quickly, gently nudging the asteroid, or simply digging some holes/eating a gas giant and weathering the storm, would be easier The assumption is that we have a problem getting anything off the planet. All these would require some good rocket engineering. I agree with everything else here a lot.

njarboe 3y ago

Maybe if you can't launch rockets into orbit with chemical rockets then your path to becoming multiplanetary would probably be quicker rather than slower. You would have to develop nuclear rockets (quite doable) and then have a much better tech for exploring the solar system and beyond.