If indeed that viewport collapsed at 4000m as the article suggests, they probably didn't even have time to realize they were dying.

I'm Hollywooding it here, but I bet it develops crack lines before collapsing. Most things in nature fail slowly, then all at once - think of standing on an iced-over puddle or pulling tree limbs.

This is likely less the case when the pressure differential is ~480 bar.

Failure is going to occur on the order of fractions of a second at those huge pressures. (Fortunately?)

Here's a pressure vessel failing at only 1 bar:

https://youtu.be/Zz95_VvTxZM

Agreed on the likely short timescale. I am imagining having just enough time to think 'something's not right...' Musicians are sensitive to latencies on the order of 10-20 milliseconds; I doubt there was time for a conversation about it.

I think 400 atmospheres of pressure change the dynamics a lot here.

Perhaps there might be a hairline crack that makes a window shatter when it's hit with a hammer. Except the hammer impact is constant. I don't think there would have been a lot of time.

I don't mean that it had a crack in it, but that it developed one as a precursor to total failure. My experience of physical materials is that they almost never just atomize, rather there's a weakpoint from which the failure cascades. I'm envisioning a process that might only last a few seconds, or be measurable in milliseconds.

The forces are immense and act all the time. In your daily life, you don't usually have that kind of system, so this feels counterintuitive.

Press against a solid object gently with one hand on each side, then suddenly yank away one hand. The object will be accelerated gently. Now do that with all your strength and send the object flying through the room in no time, with a few dozen kg of pressure. Now imagine that you could apply hundreds of tons of pressure. In such a system, every change will be nigh instantaneous.

I understand the physics just fine, thanks. I'm not disputing that it will be 'nigh instantaneous', I'm talking about how it fails. You and downvoters are also neglecting the fact that the submersible isn't suddenly teleported to/near its destination at which point it suddenly fails. It gets there slowly, passing through its safety envelope on the way.

The article says they were going for 4000m, but it was only rated for 1300m.

That would imply a collapsing somewhere between the two.

Also, would the body, being mostly made of water itself, really get crushed instantly? I would certainly expect the pressure to squeeze all the air out of your lungs.

I know nothing about how the body behaves under high pressure.

I looked up a depth to pressure calculator, at even 1300m, the pressure is 1892.67 psi.

"psi" is pounds per square inch, and a human has ballpark 3000 square inches of surface area.

So to get a (very) rough approximation, picture what would happen if you squeezed a human with 3000*1892 pounds of force. Or try not to picture it, because I imagine it being pretty gross.

MythBusters did this with a realistic (pig?) manikin. Pretty gross, yes.

For anyone that would want to see that: ‘Mythbusters - Compressed diver’ https://youtu.be/LEY3fN4N3D8

Yeah. Reminds me of this underwater pressure awareness training video on youtube from a few years ago: https://www.youtube.com/watch?v=PXgKxWlTt8A (if you're squeemish, don't click that link)

Industrial divers / welders / etc get all kinds of training to avoid that stuff, for good reason.

I'm sure they never imagined this video being paired with an incident like this but wow, their joyful and excited reactions (with no context of the lead up to this experiment) feels really morbid/sick. I realize they were trying to prove a myth and it worked, but still found it unsettling.

You'd have to subtract about 1atm from that, but yes the sudden pressure change would be quite gross.

That said, if divers are slowly "eased in" to the high pressure environment, it is actually possible to equalize pressure slowly and acclimatize. Though 1.3km would still likely be beyond the limits of that https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5110125/

The watery bits of the body would be ok but the airspaces like the lungs would rapidly compress to almost nothing.

Relatively, exceedingly merciful.

How long would it take to get down to 4000m though, didnt they lose contact like 1 hour in?

The ascent and descent to Titanic is about 2 hours one-way. The exact time they say they lost contact was after around 1 hour and 45 minutes. It was likely at or close to at the depth of Titanic.