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Assyrian soldier diving with an inflatable goatskin bag (ca. 865–860 BC)

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Re: Assyrian soldier diving with an inflatable goatskin bag (ca. 865–860 BC)

#41

Post by aix1 »

Retric wrote: post #17
nradov wrote: post #15

Earlier quoted context omitted.

None of that is even close to correct. Are you a scuba diver?

Not regularly and only very shallow so my recall of the details isn’t great. But I do recall asking about even slower breathing and the response was it extracted more oxygen but wasn’t recommended due to the risks of disorientation. I think the 2x was in relation to failing to do slow deep breathing though. As a sanity check 6l of air per minute x 5minutes is 30l which is about the size of your torso. Assuming that b…

> The volume would decrease rapidly with depth but the available oxygen per breath would increase to compensate.

> Unless you have something specific to correct?

Firstly, how would you bring the highly buoyant bubble of air underwater, in a controller manner?

But let's say, for the sake of argument, that you could. Even though the volume of the bubble would indeed decrease with depth (e.g. it would halve at 10m), the volume of each breath would remain roughly unaffected by depth. This is the reason scuba divers deplete their air supply faster the deeper they go.

The amount of available oxygen per breath is irrelevant. Even at sea level the exhaled air is about 16% oxygen (down from 21%). Giving the body access to more oxygen per breath won't make the air supply last longer[*].

[*] Interestingly, there's a point at which oxygen becomes toxic. The circumstances in which this happens is well outside the parameters of this discussion, however. https://en.wikipedia.org/wiki/Oxygen_toxicity#Underwater

Re: Assyrian soldier diving with an inflatable goatskin bag (ca. 865–860 BC)

#42

Post by handrous »

tragomaskhalos wrote: post #25
abeppu wrote: post #18

I think it's interesting that he's shown swimming mostly nude but wearing a protruding hat which seems pretty impractical. Is the hat symbolic?

A related oddity - according to "Navies of the Napoleonic Era", Turkish ships had higher decks than was normal for other navies allegedly to allow for elaborate headgear, even though this actually compromised the stability of the ships.

Is that a hold-over from Byzantium/Eastern-Roman-Empire, kept after the Turkish conquest? They were all about elaborate hierarchies of ranks and titles, often expressed through big hats or helmets.

Re: Assyrian soldier diving with an inflatable goatskin bag (ca. 865–860 BC)

#43

Post by dakial1 »

pbhjpbhj wrote: post #16

Fascinating, the second image attached to https://twitter.com/FedeItaliano76/status/143532682797161267... is good too -- I'm not settled in that confirming the second hypothesis (surface use), as the Twitter user says, it seems to me to also give stronger weight to the first (under water use). In this image the 'goatskin' users appear fully clothed in dresses (could they be scale armour or other weighted clothing), o…

I think it is settled among historians that this is a flotation device. There are multiple descriptions about it around: (http://www.iro.umontreal.ca/~vaucher/History/Prehistoric_Cra...)

Re: Assyrian soldier diving with an inflatable goatskin bag (ca. 865–860 BC)

#44

Post by seiferteric »

killjoywashere wrote: post #36
pbhjpbhj wrote: post #16

Fascinating, the second image attached to https://twitter.com/FedeItaliano76/status/143532682797161267... is good too -- I'm not settled in that confirming the second hypothesis (surface use), as the Twitter user says, it seems to me to also give stronger weight to the first (under water use). In this image the 'goatskin' users appear fully clothed in dresses (could they be scale armour or other weighted clothing), o…

The work of submerging air at atmospheric pressure vastly exceeds the potential energy value extractable from the oxygen in terms of ATP. He's using it to float.

That's what diving weights are for.

Re: Assyrian soldier diving with an inflatable goatskin bag (ca. 865–860 BC)

#45

Post by caymanjim »

killjoywashere wrote: post #36
pbhjpbhj wrote: post #16

Fascinating, the second image attached to https://twitter.com/FedeItaliano76/status/143532682797161267... is good too -- I'm not settled in that confirming the second hypothesis (surface use), as the Twitter user says, it seems to me to also give stronger weight to the first (under water use). In this image the 'goatskin' users appear fully clothed in dresses (could they be scale armour or other weighted clothing), o…

The work of submerging air at atmospheric pressure vastly exceeds the potential energy value extractable from the oxygen in terms of ATP. He's using it to float.

I was thinking that as well; it's not going to get you more than a few breaths of air, and it's not going to be easy to submerge with one. Even bogged down with weapons and armor, I suspect it would be impossible to submerge while holding something that large filled with air.

Re: Assyrian soldier diving with an inflatable goatskin bag (ca. 865–860 BC)

#46

Post by lb1lf »

aix1 wrote: post #41
Retric wrote: post #17

Earlier quoted context omitted.

Not regularly and only very shallow so my recall of the details isn’t great. But I do recall asking about even slower breathing and the response was it extracted more oxygen but wasn’t recommended due to the risks of disorientation. I think the 2x was in relation to failing to do slow deep breathing though. As a sanity check 6l of air per minute x 5minutes is 30l which is about the size of your torso. Assuming that b…

> The volume would decrease rapidly with depth but the available oxygen per breath would increase to compensate. > Unless you have something specific to correct? Firstly, how would you bring the highly buoyant bubble of air underwater, in a controller manner? But let's say, for the sake of argument, that you could. Even though the volume of the bubble would indeed decrease with depth (e.g. it would halve at 10m), the…

> Even at sea level the exhaled air is about 16% oxygen (down from 21%). Giving the body access to more oxygen per breath won't make the air supply last longer[*].

-Incidentally, in the survival suits we wear when helicommuting in the North Sea contain a rebreather device - which is simply a small bag in the suit's lining with a mouthpiece and a valve.

The idea is that when getting underwater is imminent, you take a few deep breaths. When you exhale into the bag, you can then draw the spent air back in for another gulp or two of air.

The idea being that in a couple of breaths you'll either be in the clear or dead - so a couple of extra breaths is all you realistically need. (Ever the cynic, I suspect part of the reasoning behind it is to keep you busy and un-panicked in your last few seconds alive, but anyway...)

Re: Assyrian soldier diving with an inflatable goatskin bag (ca. 865–860 BC)

#47

Post by caymanjim »

sbacic wrote: post #5
nradov wrote: post #2

He's swimming on the surface. That bag would be too buoyant for diving.

Yep. One of the first issues you'll encounter when learning to dive is getting your body to sink (that's what all those lead weights are for). I also don't think an inflatable goatskin has enough air capacity to be relevant.

One cubic foot of air displaces one cubic foot of water (compression notwithstanding). A cubic foot of water weighs 62lbs. I think you're vastly underestimating the bouyancy of an inflated bag. Try to pull a standard birthday party balloon underwater. It's nearly impossible to do. You would need a tremendous amount of extra weight to submerge a goatskin full of air.

Re: Assyrian soldier diving with an inflatable goatskin bag (ca. 865–860 BC)

#49

Post by simonh »

3pt14159 wrote: post #28
notorandit wrote: post #24

You cannot dive with an inflated goatskin, unless you carry extra weight, like stones.

Swords and armour are heavy.

As soon as you breathed in the air from the skin, you would lose the buoyancy form it and sink to the bottom.

Re: Assyrian soldier diving with an inflatable goatskin bag (ca. 865–860 BC)

#50

Post by djrogers »

3pt14159 wrote: post #28
notorandit wrote: post #24

You cannot dive with an inflated goatskin, unless you carry extra weight, like stones.

Swords and armour are heavy.

Not that heavy. Air displaces about 62 lbs of water per cubic foot, so a goatskin the size of your torso would require more weight than a soldier could carry to offset it.
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