News USS Johnston: Sub dives to deepest-known shipwreck

jedidia

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What's those white streaks/snowflakes in the video? Some kind of artifact?
 

Arvil

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I’ve seen that in many deep sea videos. There’s always little bits of stuff floating about. Maybe small critters, maybe small bits of plant and other material from above, some could be bits of plastic and other stuff we put there. What’s living down there is the cleanup crew for the oceans. Like vultures and dung beetles.
 

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Also remember that ocean at that depht is pitch black, no light at all can make it there, even on a sunny day, there are simply too many water molecules in the way. So the sub uses bright headlights and the smallest grain dust passing by is like glowing, its a contrast thing a bit like Apollo pictures "showing no stars" (that's the inverse situation, the focus is set on a very bright object while stars are very faint light from very far away).
 

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I'd say the paint and overall metal quality looks much better than on the Titanic... There's only 32 years between the two and Titanic is currently falling apart eaten by iron-hungry bacterias... There even smaller elements like the turrets and the guns really look in good condition.
 

jedidia

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I knew about marine snow, but I had no idea it actually looks like snow. I had a suspicion this might be it, but in some sequences it looked to be moving pretty fast, and sideways. Probably an artifact from the combination of high exposure and camera movement?

There's only 32 years between the two and Titanic is currently falling apart eaten by iron-hungry bacterias...

Metallurgy has taken leaps in those 32 years. But as far as I gather from the article, it's also because there's very little oxygen at the depth that destroyer is lying...
 

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Its impressive that it wasn't more damaged by the four mile descent to the ocean floor.
This depends on how it was sank. If I remember correctly, the Johnston got into one hell of a fight during the Battle of Samar and was later sunk by the sheer amount of shell hits, she had taken. So, most of the ship was flooded when she sank and only very few compartments with air trapped inside had suffered damage during the sinking.
 

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The Titanic is at such poor condition because of cheaper sulfur rich manufacturing of the iron used. It is an artifact of the time.
 

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Though it's interesting to note that Britannic, which sank in a depth less than her own length at a lower latitude than Titanic (and so is in a warmer, brighter environment more hospitable to life) is less biodgraded than Titanic. But it actually makes sense, because more hospitable to life means that higher energy metabolisms like carbohydrate/oxygen outcompete lower energy metabolisms that digest things like iron, but are more tolerant of the conditionsof the deep sea.

I wonder if there are differences in the quantity and composition of the marine snow in the North Atlantic vs. the vicinity of the Philippines. That might make a difference in what can survive at depth.
 

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The Titanic was made of steel. Do you mean the iron used in the steel manufacturing?


For actual human use of the metal in non laboratory contexts, "iron" and "steel" are pretty much synonymous. There's not much use for pure iron, and until the last few centuries, pure iron was not even possible to isolate, you either got nickel iron from meteorites or smelted some grade of carbon steel from ore, and to this day pretty much all practical uses of iron in bulk are in some sort of alloy.
 

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Yes, steel in its forms is ubiquitous, but "iron" ships are a different class from "steel" ships?

I'm not sure quite what the metallurgical difference is between "iron" and "steel" in shipbuilding contexts, but in general, the types of alloys that get called "iron" vs "steel" are not very consistent. Cast iron has a very high carbon content, while wrought iron is very low carbon. About the only hard and fast rule that I can figure out is that pure iron is always called iron, other than that the difference between what gets called iron and what gets called steel seems more to have to do with the degree of control over composition afforded by the manufacturing process than with the composition itself.
 

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I'm not sure quite what the metallurgical difference is between "iron" and "steel" in shipbuilding contexts, but in general, the types of alloys that get called "iron" vs "steel" are not very consistent. Cast iron has a very high carbon content, while wrought iron is very low carbon. About the only hard and fast rule that I can figure out is that pure iron is always called iron, other than that the difference between what gets called iron and what gets called steel seems more to have to do with the degree of control over composition afforded by the manufacturing process than with the composition itself.
We have a German industry norm that specifies what is steel and what is not, DIN EN 10020. Important for the definition is the 2% limit for carbon. If less than 2%, its steel. If more than 2%, its wrought iron (UNLESS: Its a certain historic type of chrome steel - this is still called steel, despite violating the scientific limit).

Its all about metallurgy in the definition:

1000px-Eisen_Kohlenstoff_Diagramm_Deutsch.svg.png
 

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That's what I was taught re the carbon content. Lots of thanks to Mr Bessemer for the help with the Industrial Revolution.
 

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"Gusseisen" is equivalent to English "cast iron", not "wrought iron", which is "Schmiedeeisen".

The problem with the definition "steel is anything below 2% iron" is that wrought iron falls in that category, but is generally not considered steel, and pure elemental iron has 0% carbon by definition, but is not considered steel (otherwise the element would be called steel, not iron).
 

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"Gusseisen" is equivalent to English "cast iron", not "wrought iron", which is "Schmiedeeisen".

The problem with the definition "steel is anything below 2% iron" is that wrought iron falls in that category, but is generally not considered steel, and pure elemental iron has 0% carbon by definition, but is not considered steel (otherwise the element would be called steel, not iron).

The definition specifies, that it has to be an alloy which is mostly made of iron, with less than 2% carbon. Wrought iron is actually a type of steel, even if the historic name contains iron. The forging reduces the amount of slag in the sponge iron.
 

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The definition specifies, that it has to be an alloy which is mostly made of iron, with less than 2% carbon. Wrought iron is actually a type of steel, even if the historic name contains iron. The forging reduces the amount of slag in the sponge iron.

That still leaves the problem of elemental iron.
 
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