Scott Kelly spent a year on the ISS while his twin brother Mark stayed on the ground for comparison studies.

https://www.nasa.gov/twins-study

https://en.m.wikipedia.org/wiki/Scott_Kelly_(astronaut)

I really feel like it's high time we try a rotating wheel space station to see if the artificial gravity fixes problems people develop in zero gravity.

My impression is that a rotating wheel space station, while theoretically well within the grasp of current engineering ability, would be extremely expensive given that we've never done it before.

These guys are planning to fly a prototype in 2023. https://orbitalassembly.com/

That's awesome! At least the prototype part for an automated truss build that they have the engineering for. The subsequent project timelines seem pretty fanciful, like we've built a truss then "hey presto", Pioneer station appears. That then made me question the initial prototype (which is q4 2023 so really 2024/2025). Have you been following this group for a while?

No, I just found out about them.

You wouldn't need an entire wheel, just two equally weighted compartments spinning about a centre point. In theory that's far cheaper. Perhaps you would purposely pump fluid back and fourth to maintain the correct centre of mass.

You could imagine a system where you 'space elevator' objects and people via the connecting cabling, whilst pumping fluid to offset the mass. You would likely want each side to be manned by two people.

You could later add more modules if designed correctly too. They would likely approach and attach to the centre (in a pair, one either sude), match the spin and then slot into their respective 'slots' and rotate on an arm.

It is prohibitively expensive until SpaceX's Starship brings launch costs down further.

It depends on what level of gravity is needed. The mass scales dramatically with acceleration.

And that it's big and heavy.

IIRC a spinning space station would only be beneficial if it was very large and thus far from Earth and expensive.

Otherwise the difference in gravity acting on different sides of the body and more importantly the Coriolis forces would wreak havoc and cause more harm than good.

There may be processes that use gravity to either sort proteins or concentrate chemicals. I can't think of much else, besides hormone response to stress caused by gravity.

From what I remember, the lymphatic system is basically open-ended. Blood vessels "leak" interstitial fluid, which flows through the body, collects into lymph vessels, and gets "pumped" by various processes back to the circulatory system.

Everything in chemistry is equilibrium-driven, so I can readily see some process evolving with the assumption of X units of some chemical flowing through this system, and trying to restore homeostasis in space by increasing hemolysis.

Ah, good point. That is most obvious. Blood pressure is unrqual and too high in the head in 0g, too low in the bottom extremeties.

I was imagining intracellular processes being effected. There are such processes in plants that are usually used for steering. In animals cells, if such thing exists, it may be minor efficiency changes in processes that add up to diverging from homeostasis.

Gravity is probably the big one as it is the hardest to approximate in space, but we're likely dependent on a lot of stuff that exists on Earth. We evolved to live on Earth. Earth may not be particularly suited for life, but what we consider life may be particularly suited for Earth.