5 ms·

Additionally, a bag of air of that volume would not give much time underwater - maybe an extra breath or two. The extra effort and drag of carrying the bag woul

Additionally, a bag of air of that volume would not give much time underwater - maybe an extra breath or two. The extra effort and drag of carrying the bag would make it less effective than just diving. A modern steel SCUBA tank is typically pressurized to 200 bar, or about 3000 psi, making it 200x more useful than a bag. An inflatable ball is only inflated to about 0.5 bar/8 psig, human lungs are only capable of about 0.1 bar/2 psi. This would be about as useless underwater as one of those little one-liter bottles with integrated mouthpiece that scams show being inflated with a bicycle pump... Still cool to see swimming like this depicted in 800BC! Puritan attitudes towards swimwear as well as imperial navies conscription of non-swimming sailors seem to have caused us to imagine swimming as a modern activity that we do better than anyone in history, but I expect that people throughout history did lots of swimming. I also find it interesting that he's depicted wearing a helmet, I wonder if that's to identify that "this guy's an Assyrian foot soldier" or if they actually swam in their helmets!

clipradiowallet 5y ago
> This would be about as useless underwater as one of those little one-liter bottles with integrated mouthpiece that scams show being inflated with a bicycle pump... These irk me too! The pictures never mention that the hand pump in them, isn't a bike pump at all, it's a high-pressure pump that you will have to pump for nearly an hour. I see these constantly in the "suggested products" when shopping for any diving kit on amazon.
Retric 5y ago
It’s more complicated than that because the bag can be deflated unlike a scuba tank so you’re benefiting from normal atmospheric pressure. Assuming the scuba tank was filled with normal atmosphere and this bag was about the size of someone’s torso, it’s probably much closer than 200x. First you don’t normally do ultra slow deep breathing with scuba gear which can increase the amount of oxygen extracted. Next the volume of scuba tanks isn’t that high normally and you lose reserve capacity. My guess is up to 5 minutes of air in a bag is probably possible which could be a quite a bit if their pearl diving or something. On the other hand it could simple be an inflatable bag useful as a flotation device.
- nradov 5y ago
  None of that is even close to correct. Are you a scuba diver?
  - Retric 5y ago
    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 bag started that size and got completely emptied it’s about right. The volume would decrease rapidly with depth but the available oxygen per breath would increase to compensate. Unless you have something specific to correct?
    - jessaustin 5y ago
      That's about the size of my torso, but I'm fat as hell. I suspect the average ancient swimming warrior was in better shape.
      - Retric 5y ago
        Unless your short your estimate seems odd. The torso is about 1/2 the volume of the average adult and people are close to the density of water of 1kg/l or 2.2lb/l. So 30l would be the expected torso volume of someone weighing ~60kg or ~130 lb. Edit: “47% trunk and neck” so 40% torso would be 75kg and 165lb seems reasonable as a smaller person would also need less air.
        jessaustin 5y ago
        30L is 8 gallons. The average torso is somewhat longer than a five gallon bucket, but of course it's much slimmer than a five gallon bucket. An eight gallon bucket, if it existed, would be larger yet. I would question both the assumption that a torso is half the volume of a human and the further assumption that the density of humans is uniform. Obviously the thorax, which contains the lungs, is less dense than the legs, which just have muscles and massive bones with a thin layer of fat. Sorry it took a while to respond; I got rate-limited this morning.
nradov 5y ago
Swimming was quite common in ancient Mediterranean area societies. They even did a lot of breath hold free diving, hunting for sponges and shellfish. Modern swimmers probably are better than anyone in history. An optimal front crawl stroke technique isn't intuitively obvious at all. There have been significant improvements just in the last few decades. https://en.wikipedia.org/wiki/Front_crawl#History?wprov=sfla1 https://en.wikipedia.org/wiki/Front_crawl#History?wprov=sfla...
- setr 5y ago
  Don’t know about “optimal”, but apparently the front crawl itself isn’t too novel.. from that wiki page: > The "front crawl" style has been in use since ancient times. There is an Egyptian bas relief piece dating to 2000 BCE showing it in use.
- deleted 5y ago
  [deleted]
cesis 5y ago
Strictly speaking every 10m under water increases pressure by one bar. So elastic bag 10m under water would take up 2x less space.
MisterTea 5y ago
When I was a kid we had an above ground pool that was about 3 feet/~1 m deep. One day in the shed I found a 6 foot/2m length of hose that looked to be about the same diameter as the tube on the my little snorkel. Ah ha! I can attach this to my snorkel, tie the other end to a pool float and breath under water like a diver! My idea did not work out as planned. At the surface I was able to breath through the hose but once I tried to "dive" down I found that drawing a breath was difficult. At the full depth I could not draw a breath. I told my father later on (who was an engineer) and he explained the physics of water pressure.
- robocat 5y ago
  That was dangerous due to the risk of hypercapnia: "increased CO2 levels could lead to unconsciousness which, if happening while in the water, can result in drowning.". Note that our breathing is regulated by the amount of CO2 in our bloodstream, not the amount of oxygen. There is a fantastic explanation of the danger here: https://blog.daneurope.org/en_US/blog/are-full-face-snorkeling-masks-dangerous https://blog.daneurope.org/en_US/blog/are-full-face-snorkeli... There are safety regulations to limit the volume of air inside a snorkel (the dead space). "Snorkels constitute respiratory dead space. When the user takes in a fresh breath, some of the previously exhaled air which remains in the snorkel is inhaled again, reducing the amount of fresh air in the inhaled volume, and increasing the risk of a buildup of carbon dioxide in the blood, which can result in hypercapnia. The greater the volume of the tube, or the smaller the tidal volume of breathing, the more this problem is exacerbated." —https://en.wikipedia.org/wiki/Snorkel_(swimming) https://en.wikipedia.org/wiki/Snorkel_(swimming)
  - bscphil 5y ago
    > When the user takes in a fresh breath, some of the previously exhaled air which remains in the snorkel is inhaled again For a long snorkel, you would want to exhale through your nose.
mcswell 5y ago
IIRC, the average air consumption is about 1 cu. ft./ min. at atmospheric pressure. Assuming the bladder is not pressurized, at a guess it could hold ~2 cu. ft., so maybe a couple minutes worth of air. If you could manage to submerge, that would be substantially longer than the average person can hold their breath, maybe enough to be worth it. (Notice the "if".)

clipradiowallet 5y ago

> This would be about as useless underwater as one of those little one-liter bottles with integrated mouthpiece that scams show being inflated with a bicycle pump... These irk me too! The pictures never mention that the hand pump in them, isn't a bike pump at all, it's a high-pressure pump that you will have to pump for nearly an hour. I see these constantly in the "suggested products" when shopping for any diving kit on amazon.

Retric 5y ago

It’s more complicated than that because the bag can be deflated unlike a scuba tank so you’re benefiting from normal atmospheric pressure. Assuming the scuba tank was filled with normal atmosphere and this bag was about the size of someone’s torso, it’s probably much closer than 200x. First you don’t normally do ultra slow deep breathing with scuba gear which can increase the amount of oxygen extracted. Next the volume of scuba tanks isn’t that high normally and you lose reserve capacity. My guess is up to 5 minutes of air in a bag is probably possible which could be a quite a bit if their pearl diving or something. On the other hand it could simple be an inflatable bag useful as a flotation device.

nradov 5y ago
None of that is even close to correct. Are you a scuba diver?
- Retric 5y ago
  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 bag started that size and got completely emptied it’s about right. The volume would decrease rapidly with depth but the available oxygen per breath would increase to compensate. Unless you have something specific to correct?
  - jessaustin 5y ago
    That's about the size of my torso, but I'm fat as hell. I suspect the average ancient swimming warrior was in better shape.
    - Retric 5y ago
      Unless your short your estimate seems odd. The torso is about 1/2 the volume of the average adult and people are close to the density of water of 1kg/l or 2.2lb/l. So 30l would be the expected torso volume of someone weighing ~60kg or ~130 lb. Edit: “47% trunk and neck” so 40% torso would be 75kg and 165lb seems reasonable as a smaller person would also need less air.
      - jessaustin 5y ago
        30L is 8 gallons. The average torso is somewhat longer than a five gallon bucket, but of course it's much slimmer than a five gallon bucket. An eight gallon bucket, if it existed, would be larger yet. I would question both the assumption that a torso is half the volume of a human and the further assumption that the density of humans is uniform. Obviously the thorax, which contains the lungs, is less dense than the legs, which just have muscles and massive bones with a thin layer of fat. Sorry it took a while to respond; I got rate-limited this morning.

nradov 5y ago

Swimming was quite common in ancient Mediterranean area societies. They even did a lot of breath hold free diving, hunting for sponges and shellfish. Modern swimmers probably are better than anyone in history. An optimal front crawl stroke technique isn't intuitively obvious at all. There have been significant improvements just in the last few decades. https://en.wikipedia.org/wiki/Front_crawl#History?wprov=sfla1 https://en.wikipedia.org/wiki/Front_crawl#History?wprov=sfla...

setr 5y ago
Don’t know about “optimal”, but apparently the front crawl itself isn’t too novel.. from that wiki page: > The "front crawl" style has been in use since ancient times. There is an Egyptian bas relief piece dating to 2000 BCE showing it in use.
deleted 5y ago
[deleted]

cesis 5y ago

Strictly speaking every 10m under water increases pressure by one bar. So elastic bag 10m under water would take up 2x less space.

MisterTea 5y ago

When I was a kid we had an above ground pool that was about 3 feet/~1 m deep. One day in the shed I found a 6 foot/2m length of hose that looked to be about the same diameter as the tube on the my little snorkel. Ah ha! I can attach this to my snorkel, tie the other end to a pool float and breath under water like a diver! My idea did not work out as planned. At the surface I was able to breath through the hose but once I tried to "dive" down I found that drawing a breath was difficult. At the full depth I could not draw a breath. I told my father later on (who was an engineer) and he explained the physics of water pressure.

robocat 5y ago
That was dangerous due to the risk of hypercapnia: "increased CO2 levels could lead to unconsciousness which, if happening while in the water, can result in drowning.". Note that our breathing is regulated by the amount of CO2 in our bloodstream, not the amount of oxygen. There is a fantastic explanation of the danger here: https://blog.daneurope.org/en_US/blog/are-full-face-snorkeling-masks-dangerous https://blog.daneurope.org/en_US/blog/are-full-face-snorkeli... There are safety regulations to limit the volume of air inside a snorkel (the dead space). "Snorkels constitute respiratory dead space. When the user takes in a fresh breath, some of the previously exhaled air which remains in the snorkel is inhaled again, reducing the amount of fresh air in the inhaled volume, and increasing the risk of a buildup of carbon dioxide in the blood, which can result in hypercapnia. The greater the volume of the tube, or the smaller the tidal volume of breathing, the more this problem is exacerbated." —https://en.wikipedia.org/wiki/Snorkel_(swimming) https://en.wikipedia.org/wiki/Snorkel_(swimming)
- bscphil 5y ago
  > When the user takes in a fresh breath, some of the previously exhaled air which remains in the snorkel is inhaled again For a long snorkel, you would want to exhale through your nose.

mcswell 5y ago

IIRC, the average air consumption is about 1 cu. ft./ min. at atmospheric pressure. Assuming the bladder is not pressurized, at a guess it could hold ~2 cu. ft., so maybe a couple minutes worth of air. If you could manage to submerge, that would be substantially longer than the average person can hold their breath, maybe enough to be worth it. (Notice the "if".)