Why do ISS crew members often cross their arms?

Question

I am watching live stream from ISS to follow the return of two ISS crew members, Thomas Pesquet and Oleg Novitskiy.

At several moments, they crossed their arms in a not really natural way:

Crossed arms 1

Crossed arms 2

Why do they cross their arms like that? Is that a standard procedure to not touch anything by accident?

SCUBA divers do the same thing to prevent their arms from flapping around. — mustaccio, Jun 02 '17 at 13:36
@mustaccio And you can achieve the same effect by filling up a bathtub and submerging yourself in it (or going swimming). It's quite fun to experiment with buoyancy. — JAB, Jun 02 '17 at 20:17
upvote this comment if you too read it as "why ISIS crew members..." on the hot network questions list. — Will Ness, Jun 04 '17 at 14:17
@Mehrdad And the two guys in SF's answer are a little further into the routine. — David Richerby, Jun 05 '17 at 08:21
@mustaccio thats what i thought too..... Scuba diving has some parallels to space diving — toesslab, Jun 05 '17 at 18:22

score 67 · Accepted Answer · answered Jun 02 '17 at 11:24

It's about as standard procedure as crossing your legs when you're sitting.

Arms in microgravity, without conscious effort to keep them by your body, will tend to extend the elbows to the sides - just like holding knees together when sitting, at least for men, requires active (if minor) effort. Holding arms like this simply prevents sticking elbows into the person next-to, and takes less effort than actively squeezing them along your body.

Compare to these:

arms loose
people keeping arms along their body, do this consciously - you can see the positions are forced. Others are either spreading their elbows, or holding their arms.

Cool photo! I've asked a tangential follow-up question. – uhoh Jun 02 '17 at 16:18 — uhoh, Jun 02 '17 at 16:18

score 54 · Answer 2 · edited Jun 05 '17 at 15:12

54

Offered as a supplement to @SF's answer:

This shows the fully relaxed arm position obtained by a sleeping astronaut.

From here

edited Jun 05 '17 at 15:12

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answered Jun 02 '17 at 13:09

Organic Marble

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He is cute - smiling in his sleep. I guess I would do so as well in that particular sleeping place! :) – AnoE Jun 02 '17 at 15:02
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Looks like dreaming about braaains... – Agent_L Jun 05 '17 at 13:31
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Dreaming about space sheep? – Wayne Werner Jun 05 '17 at 15:43

Digger · Answer 3 · 2017-06-04T18:50:11.930

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For many astronauts, it is simply a matter of being considerate to your fellow astronaut who is appearing alongside you. It would not be nice to let your arm drift into contact with the other astronaut - astronauts have "personal space'" too.

Plus, I think we'd all agree that Earth-bound humans by and large think the natural position that arms want to attain in microgravity conditions looks "sort of dumb."

Astronauts have egos, too!

edited Jun 04 '17 at 18:50

answered Jun 04 '17 at 18:32

Digger

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"personal space" huhu..! – le_daim Jun 04 '17 at 18:46

score 5 · Answer 4 · answered Jun 02 '17 at 11:29

There is no special procedure there - just microgravity.

Note that the one on the left looks like a normal relaxed pose, with his arms dropped down as they would be on Earth.

The other two do look a little "unnatural", but if you ignore their arms being pointed forward, it is exactly the same pose, and just as comfortable with no gravity pulling their arms down.

Why do ISS crew members often cross their arms?

4 Answers4

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