No, I’m responding to the repeated assertion that aquatic systems are “an effectively 0-G environment”. The reality is that gravity plays a huge role in the function and health of aquatic ecosystems (far moreso than terrestrial life where small plants, fungi, and most microfauna rely very little on gravitational mechanisms for nutrient transfer, waste removal, or mobility), and while you might be able to keep a fish alive in a freefall tank through actively filtering water, mechanically driven currents, et cetera, it isn’t going to be a comfortable environment or will “do the best”.
It has clear disadvantages. Mainly that it would weight much more than a habitat for air breathers for the same volume of containment, and it has to be stronger to withstand a higher pressure differential and the forces on it do to changes in acceleration or centrifugal effects.
Perhaps the problem of animal excreta in microgravity could be solved using daipers. I think that’s what they used with Ham the space chimp. I don’t know what they used with Laika the space dog.
In a suitably advanced space future, maybe all the animals in space would wear some kind of still-suit that collects waste efficiently for re-use.
Arthur C. Clarke write in the essay “Which Way Is Up” in the book “Report on Planet Three” :
I was once diving in a somewhat gloomy coral cave whose floor was covered with light sand when I was surprised to see that most of the fish around me were swimming upside down. All the light came from below, and they’d been fooled into thinking that this direction was up.
You are talking about the ocean, not an aquarium in space which would be expected to function exactly like an ocean any more than a space ship in 0-G conditions will function identically as the surface of the earth does. There are aquariums that don’t have any problems with nutrient transfer and waste removal because they don’t function exactly like the ocean in letting the waste settle to the bottom. And it is effectively a 0-G environment for most species of aquatic animals. Some of them depend on buoyancy in the varying pressure of their natural environment but that’s it. Under water it is effectively a 0-G environment. That’s why astronauts train underwater. Terrestrial animals are far more dependent on gravity in every way.
No, that isn’t correct. As someone who is an experienced tec-rec diver and has done parabolic ‘weightless’ flights, I can speak from direct knowledge that the neutral buoyancy of ocean is not at all like freefall conditions in terms of sensation or mobility. The primary reason that astronauts train in neutral buoyancy pools is really to gain experience in working in an EVA suit, which is too awkward and heavy to effectively move around and train in on land. Astronauts also spend an extensive amount of time doing parabolic flights (far more than the couple of hours that I did) because that is really the only way to experience actual freefall conditions without going to orbit.
No, and I’m getting increasingly tired of being deliberately misconstrued on this point. The effects of being in a neutral buoyancy condition in water are not equivalent to freefall, and an aquatic animal in a freefall condition is going to experience numerous handicaps to locomotion, orientation, et cetera. That a fish can survive for some duration in a ‘freefall aquarium’ is something I’ve repeatedly acknowledged but the titular question of the thread is “Which animals would do best in space?” and there are numerous stated reasons why fish and most other aquatic animals would not be better adapted, and in many ways hampered, by inhabiting a freefall environment, notwithstanding all of the problems in maintaining a large aquarium in a spacecraft.
I’m not misconstruing anything. If humor isn’t good enough, I’ll spell it out. I was specifically refuting your silly claim to have personal insight into what’s relevant here - the difference between aquatic neutral buoyancy under gravity and aquatic freefall. You have experienced both diving and freefall in a parabloic weighless flight, but it’s obvious that the great difference in “sensation and mobility” that you experienced was because in the latter case you were in air rather than water.
Again, the primary reason that astronauts train in neutral buoyancy pools is really to gain experience in working in an EVA suit, which is too awkward and heavy to effectively move around and train in on land. Training in a neutral buoyancy pool helps to simulate how to handle an EVA suit during spacewalks, but it is not otherwise like being in freefall conditions in terms of sensation or mobility. If it were, NASA and other astronauts would spend more of their training time in the pool, which is relatively cheap, rather than doing weeks of training in expensive parabolic flights.
That’s nice to know yet does not refute my statement that fish are adapted to an effectively 0-G environment. Fish don’t have to train to live in free fall conditions because it’s meaningless to them. Minor water movements have more effect on them than gravity does.
Fish do not live in or are adapted to “an effectively 0-G environment”. They are evolved to live in a 1 gee gravitational environment where they can achieve neutral buoyancy in the surrounding medium.
Could you explain the difference? Imagine we had a 1 m³ aquarium, cubic, with six quadratic glass panels, sealed and completely filled with water. Ignore for a moment that this would be a bad idea, as it would shatter if the temperature increases. Let me also put the problems of filtering and feeding aside for the time being. We put a fish, a shrimp and an octopus in it. What would those animals experience differently from their subjective POV in 1g and in 0g until they run out of oxygen?
The internal organs of the creature still feel a gravitational force.
If you’re inside a neutrally buoyant submarine in 1 g, you’ll still be pulled to the floor of the sub and recognize up from down. In 0 g, you’ll float inside the sub just as you would under any other 0 g conditions.
Our internal structures all have a similar density to water, which is part of the reason why blue whales can exist. But it’s not identical, so dense structures will be pulled down and light ones will float. In 0 g, that doesn’t happen.
Are you sure of that? Can we humans feel those subtle differences? I have read that scuba divers can get disorientated and may not know which way is up and which way is down in the dark, which can be deadly. I was never a scuba diver, only a snorkler, so I may be wrong. And what about fish, shrimps and octopuses? IDK, genuinly asking.
Sure, but this is not relevant to aquatic creatures.
This seems like the relevant part. A hypothetical completely homogenous creature with neutral buoyancy would feel no internal force. A realistic creature creature with internal structure that varies in density with feel some internal force, depending on how much that internal density varies. But in realistic creatures it can be very much less than 1g.
