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Comment by MichaelZuo | Hacker News Reader

How could 3 adults, even lying perfectly still, not use up all the oxygen in that air pocket within 35 hours?

I thought human beings needed several cubic meters of fresh oxygen (at 1 atm) per hour…

You got me wondering and I thought maybe there was some kind of gas diffusion where carbon dioxide is absorbed by the ocean water instead of building up in the enclosed space, and finding the most closely related stack exchange question I think I’m satisfied with this answer:

probably that four-foot bubble communicated with a larger volume or air under the hull of the boat - and that's the most reasonable explanation of this miraculous survival.

When picturing it we might assume the rest of the boat is flooded and this pocket of air is all that remained but that may not be the case.

https://physics.stackexchange.com/questions/67970/surviving-...

They were in the engine room. The engine would have both air intake and exhaust systems. There was potentially some portion of one or both systems interacting with other air pockets.

Yeah, I think the co2 and o2 would diffuse in and out of the water below and eventually equalize, similar with how aquarium co2 indicator works.

Mr Nimbus gave them gills to save them and wiped their memory :)

Mr nimbus also controls the police!

It might be enough. Google says a human needs 300-550 liters of oxygen a day. That equals to about 6.8-12.4 cubic meters of air for the 3 of them for 36 hours.

The space does seem like it could be large enough to hold that much air, especially if it's compressed a little.

Not at 1atm. The air was pressurized.

It doesn’t sound to me like the boat actually sank. In the article it mentioned that they heard the rescue helicopter from within. Wouldn’t that imply that the pressure inside would be one atmosphere? Am I thinking about the physics of this wrong?

The pressure of any trapped gas will be equivalent to the depth of the lowest level containing air - so if the bottom of your air bubble is a meter below sea level, your pressure will be 1.1 atm.

Sound does carry remarkably well through water - but you're right. The ship capsized, but the hull held enough air that it stayed afloat.

Mostly, the weight of the boat pulling down would compress the air bubble a bit, probably not very much though.

It was floating upside down.

There is a picture towards the end of the story.

How is that? It was at surface pressure and then rolled over.

If the booyancy of the trapped air was a significant factor in the boat not sinking, then the air would have been at pressures over 1atm.

Put a barometer in an empty, upside-down cup. Force the upside down cup 1/2 way down into the water, trapping the air inside.

The barometer will be at the sea pressure of the bottom of the cup.

Makes sense if the glass is perfectly vertical, air can’t escape and force is applied from the top. But if you capsize a glass by slightly turning it on its side such that most of it sinks and the air escapes by water displacement you would get some compression on the remaining air but its unclear how much.

In this case, the boat was floating, albeit upside down. So the volume of air trapped must have been sufficient to keep a 44 metre boat afloat; i.e. not a trivial amount.

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