Can you sink by blowing up your BC below 40m?

[Russoft]

This whole thing can be explained rationally with science.

See this here phase diagram?

The air transitions from a gas into a liquid as we increase pressure. It so happens 40 meters, or 5 ata, is that pressure (assuming the air is at 20 C or 68 F). This is why diving in cold water is more challenging, because the pressure at the phase change is lower. This is also why warm water diving is generally easier.

 

[Boyan]

I am pretty sure I wasn't trolled, but there is a good chance of misunderstandings. Interesting theories so far

 

[Schwob]

I am pretty sure I wasn't trolled, but there is a good chance of misunderstandings. Interesting theories so far

That's the spirit!
I think
@Kevrumbo
put forth a good stab at where the real misunderstanding might have been rooted in. But who knows.
If you ever find out from your friend, please do let us know.
Or maybe not, maybe someone can leverage this into a grant to research some of the alternative truthts... um, thoughts...

 

[NAM001]

Well let's see... a bubble is a nugget of air surrponded by water, so a negative bubble must be a nugget of water surrounded by air: a water droplet. So maybe he's telling you that if you fill your BCD with water at 40m, it won't float so great.

A negative bubble could also just be a manic-depressive bubble having a bad day.

******************

Please don't be offended by our having fun. Your friend may have been talking about many real and interesting things, he just didn't express himself well enough.

What if the diver self identifies as a negative bubble??????

 

[FinnMom]

This did make me think how much effort it would require to breath-inflate a BCD against 5 bar of pressure. 5x as difficult as on land is hard to accurately imagine, but it doesn't sound easy. Also thinking this effort would that cause CO2 buildup, or a fuzzy-headedness that would not great when you are removing/replacing your 2nd stage. Not something I intend to try underwater, but in a chamber this would be interesting.

 

[Patoux01]

This did make me think how much effort it would require to breath-inflate a BCD against 5 bar of pressure.

The air in your lungs is at 5bar as well at that depth.

 

[bowlofpetunias]

hubby.... @thanksforallthefish only ever orally inflates he says it really hasn't made a difference that he's noticed. He's been to that depth.

 

[dberry]

@Boyan I hope you realize that nobody here means to be disrespectful. Some of the answers do try to address why this statement might be thought to be true so it is a good thing you asked. Some of us are just playing with the concept for the fun of it without meaning to be disrespectful.

@boulderjohn your story reminded me of a talk we attended by a Marine biologist who was studying the fish that lives in the anus of the sea cucumber. People had arguing about it's existence for years.

This guy got a grant to try to prove it one way or the other. He spent a significant amount of time taking photos of the south end of seacucumbers travelling north and their excrement. Finally he saw a fish come out! More funding to get a picture to prove it.

Next question... (more funding) How did the fish get IN there? Turns out the seacucumber has an aspirating anus... Yup it breathes through it's butt. Turns out the fish just waits till the sea cucumber needs to breath and swims back in there.

Actually, I think the pressing question is WHY did the fish want to get in there...

 

[bowlofpetunias]

Ongassing???

 

[kafkaland]

This whole thing can be explained rationally with science.

See this here phase diagram?

The air transitions from a gas into a liquid as we increase pressure. It so happens 40 meters, or 5 ata, is that pressure (assuming the air is at 20 C or 68 F). This is why diving in cold water is more challenging, because the pressure at the phase change is lower. This is also why warm water diving is generally easier.

No. The critical point (C) of nitrogen is at 126K, that is below room temperature. So you cannot liquefy nitrogen just by compressing it, no matter how hard you try. It will just get denser and denser, but never outright undergo a phase transition and condensate unless you chill it.