# Why do we never see astronauts doing breaststroke or the "Man from Atlantis" swimming movements, say, and thus swimming in air in free fall?

Why do we never see astronauts and others swimming in air in free fall?

The swimming strokes that work well under water on earth are the breast stroke and especially that "Man from Atlantis" stroke that has recently somewhat revolutionized competitive swimming. I'd like to see astronauts on the ISS or failing that, people in free fall in an airplane flying in a parabolic path swimming in air like that.

It might be an idea to get a champion swimmer like Mark Phelps to try swimming in air in a parabolic path airplane. Or the guy in this video:

A way to correct for the effect of air currents and unplanned movements of the airplane or space station during a demonstration that swimming in air either works or doesn't would be to have pairs of air swimmers swim in opposite directions.

Swimming in air might be a good form of exercise and relaxation. Astronauts could have races or set records.

If it's impossible to make any headway, why don't we ever see that fact demonstrated?

• – uhoh
Commented May 2, 2021 at 0:45
• – uhoh
Commented May 2, 2021 at 0:47
• I think when you swim, your forward motion is caused by drag as you push back against water. At room temperature and standard pressure, the density of air one thousandth the density of water. This means air drag itself is one thousandth of water drag---unless you paddle faster. Since drag varies with the square of velocity, I think you'd need to paddle sqrt(1000)=30 times faster? Not sure, but at a minimum, it seems you'd need to paddle way way faster in order to propel forward in air.
– user39728
Commented May 5, 2021 at 5:46
• "...paddle way faster in order to propel...." I've got an idea, we could call a device to do that a propellor Commented May 5, 2021 at 12:36

Air is very different from water. It is much less dense, and it is much less viscous. When you thrust your outspread arms back under water, the water can't "get out of the way" of your arms very easily, so you succeed in forcing a decent volume of water back relative to you; and because water is heavy (per unit volume), you don't have to accelerate that much of it backwards to generate noticeable forward acceleration in your own body. (On average, you accelerate on the pulling stroke, and decelerate due to water resistance between strokes, so your overall speed is constant.)

With air, on the other hand, it flows right past your arms, and in any case, you have to push a lot of air backwards to even have a small forwards acceleration.

It could be done with large paddles or wings, but large open spaces aren't terribly practical on a space station anyway.

If it's impossible to make any headway, why don't we ever see that fact demonstrated?

Here you go:

At about 00:16, you can see swimming in space demonstrated. It doesn't work very well.

• That's now how you swim, though ;-)
– user39728
Commented May 5, 2021 at 5:40
• @user39728_i_said_user_39728_i_ You can see several swimming-style techniques (at the very least, movements that'd move you around significantly in water) attempted with little luck in the video. I've seen worse technique in public pools. :-p Commented May 5, 2021 at 10:45
• It wasn't very good swimming. Quite good for standing waist deep in water and splashing water on someone else, but not very good for swimming especially not while totally immersed in the fluid. It did work, though, and a better technique would work better. Commented May 5, 2021 at 21:57
• @MatthewChristopherBartsh I'm not sure how you watch that video and go "oh yeah, it works". It takes several minutes to make even the tiniest bit of headway, and there's clear attempts at scooping air. Commented May 6, 2021 at 11:35
• @ceejayoz "oh yeah, it works". I don't know what you are talking about. Commented May 6, 2021 at 18:53

To be a good form of exercise you need a certain amount of resistance to breaststroke swimming. For the very low viscosity of air the human hands are too small for the necessary resistance. Swimming fins for the hands would increase the area and thus the resistance.