4 ms·

One of the biggest hypothetical great filters is massive war. Higher engineering requirements for rockets (or even simple projectiles such as cannons or arrows)

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.

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.