Can we swim forward in space with wide enough arms or wings attached in vacuum?
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Not really. Space is very empty, there’s nothing to push against. So no accelerating, decelerating or changing direction. You’d be at the mercy of gravity.
You could use a giant sail though to use solar wind to propel you.
Newton’s 3rd Law is going to stop you here. When you swim in a pool, you push against the water in the pool to drive yourself forward. In space there is nothing to push against so you won’t have any translational acceleration; that’s a fancy way to say your center of gravity won’t be affected.
You might be able to get some kind of rotational acceleration by waving your limbs tucking them into your body but your center of gravity is still going to just do its thing.
Not meaningfully.
Swimming relies on Newton’s third law – for every action, there is an equal and opposite reaction. More specifically: When you swim, your limbs push water. The water pushes back on you, and this push causes you to accelerate.
In the vacuum of space, there is nothing for your limbs to push against. You can flail your arms and legs about however you like, but all you will do is change how you’re rotating. In order to move through a vacuum you need to eject mass away from yourself in the opposite direction that you want to travel. This is what rockets do: They eject mass (exhaust) at high velocity to generate thrust. If you want to move, you would likewise need to eject mass away from yourself.
Technically, there actually is mass in space, but it’s very diffuse and for all practical purposes it may as well not even be there – roughly on the order of one atom per cubic meter. This is nowhere near enough mass to generate meaningful thrust for a massive object like a human.
Well, actually….
Think of swimming as a pushing liquid wall. the lighter and more fluid the wall is, you’ll need bigger hand to push better. Thus, bigger wing on birds proportionally compare to fishes.
Now, the space is not entirely vacuum. There is some hydrogen molecules floating around although they are arguably negligible amount.
So, technically, if you have very very big wing, you will be able to push forward in very slow and inefficient rate.
But at that point, solar wind (which is radiation from the sun which contains some hydrogen atoms too) will going to push the wing better than your flapping of it.
I suggest you to snip off this humongous wing and use it as a wall to push against.
You can’t swim in vacuum.
When you move your arms and legs you don’t have any air or water to push against.
You can twist and turn, but that will not move you forward.
The problem is that all the moment um of all your parts always adds up the same no matter how you redistribute the sum.
To get a change you would need to throw something away from you.
You can “swim” in zero g if you do it inside a space that has air.
In theory you could probably also swim in zero-g in water.
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