Wikipedia:Reference desk/Archives/Science/2016 March 9

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

March 9

Some structures on a ship's deck

This and this are tiny screenshots from the film Titanic. Specifically, they are from the scene early in the film wherein the sailors are on the ship's deck, running toward Jack and Rose after hearing her screams when she slips off the railing and nearly falls into the ocean. Questions:

1. What is the large white cylindrical structure, with what looks like a door with six handles, to the left of and behind the sailors?
2. If that is a door, why does it need six handles instead of just one?
3. What is the white column, curled forward at its top end so that it is sort of shaped like an upright bowl pipe for smoking, to the left of the large cylinder?
4. What are the two black barrels/posts to the right of the sailors?

—SeekingAnswers (reply) 05:44, 9 March 2016 (UTC)

The bowl-pipe thing is a cowl on a ventilation duct to get fresh air to some lower deck area. DMacks (talk) 05:57, 9 March 2016 (UTC)

And to make it slightly harder to throw cigarette butts down it and stuff? Sagittarian Milky Way (talk) 04:55, 10 March 2016 (UTC)

More to keep rain and sloshing waves from pouring down the shaft, I believe. Pointing it towards the front might also provide extra air flow when the ship is in motion. StuRat (talk) 05:37, 10 March 2016 (UTC)

Clearly it's for rain but maybe it's not shaped like the more obvious mushroom because a straight shaft would be too tempting for jerks to throw shit down. The Titanic deck is at least 50 feet high (C-deck, D-deck, E, F, G and part of a deck), it would take a hurricane to put waves in the ventilators and there would be water all over the deck and in anyone's room if they left the portholes open. Millionaires might get seasick or afraid on the most luxurious ship in the world and take their business to a competing carrier. This is easily avoidable with meteorology. Sagittarian Milky Way (talk) 06:21, 10 March 2016 (UTC)

See rogue wave. It would be nice not to sink if one of those hit. StuRat (talk) 18:42, 10 March 2016 (UTC)

Oh right. Presumably they don't point it where it's more likely to get swamped so that a mushroom open at the stem top is inferior. Also I didn't look at the screenshots, for some reason I thought they bent 180 degrees (maybe I saw a picture of that somewhere). Sagittarian Milky Way (talk) 19:22, 10 March 2016 (UTC)

I wondered why they don't use a mushroom shape myself. All I can think of is that it would restrict air flow too much, versus facing them forward and thus getting the speed of the ship driving air down the hatch. They then must have decided that it's worth the risk that a rogue wave won't come from that direction. I suppose they could have a type of check valve that closes the hatch if water flows down it, but that would be expensive and need maintenance. StuRat (talk) 03:07, 11 March 2016 (UTC)

I'm more than a bit skeptical of all this unsourced logic around. I mean, let's start with the notion that a "rogue wave" was a myth until very recently - any sensible, well trained sailor or scientist could have told you that claiming to be hit by one was like saying your ship rammed into one of those giant turtles with an island on its back. Besides, if a wave hits that is high enough to spray the deck of the Titanic my guess is they have other problems. And surely you can throw cigarette butts down it whether it is a mushroom or a bent pipe. My guess - I don't claim it's right either - is we see people hide in them so often in the movies because they're actually meant to be gotten into for something, cleaning, probably some sailor caught with a shirt button undone had to go down there with a toothbrush and some abrasive and not come back up until you could eat off it. Wnt (talk) 16:04, 11 March 2016 (UTC)

Yes, but if the pipe was bent into a ∩ shape at the top, some people (that are not quite willing to drop it wherever they stand) might decide to litter in a plant pot or lifeboat or something instead (or God-forbid an ashtray happens to be the closest thing so they put it in that). Cigarette butts don't bounce well so if you shape the ∩ right it might provide some discouragement to jerks or especially jerky extreme convenience seekers. Sagittarian Milky Way (talk) 17:08, 11 March 2016 (UTC)

While rogue waves 3 times the height of Titanic's deck have been observed, I suspect that more ordinary things, like heavy rains, provided enough incentive to not leave the ventilation tubes open at the top. (I supposed they could cap the tubes during heavy rains, but how long could they survive with no ventilation down below ? The could also let rain pour down the shaft and just use the bilge pump to get rid of it, but it's not good to be overly dependent on that.) StuRat (talk) 20:23, 11 March 2016 (UTC)

Dover gun turret.

2) The big white cylinder looks like a gun turret (compare with the pic I've added here). Did they by any chance use a decommissioned military ship for that scene ? If so, the guns (cannons) would have been removed from the top, but the turret left in place. As for the door, perhaps shells would be loaded that way, and the massive armored door would need several latches to hold it in place under enemy fire (more sophisticated designs had elevators to lift shells into position from below deck). Here's a diagram of a Dreadnought class battleship, with turrets and guns in place: [1] (you can only see the top of the turrets in the side view, since most is below the rails). StuRat (talk) 06:03, 9 March 2016 (UTC)

My guess: the base of an electric crane, towards the front of c-deck. See http://www.encyclopedia-titanica.org/titanic-deckplans/c-deck.html --Tagishsimon (talk) 06:49, 9 March 2016 (UTC)

Or ditto, towards the rear of b-deck. http://www.encyclopedia-titanica.org/titanic-deckplans/b-deck.html ... seems to tie in better with the ventilation doodab and the, err, grey rope thingies. See also figure 129 on this page - http://www.copperas.com/titanic/dynamo.htm --Tagishsimon (talk) 06:51, 9 March 2016 (UTC)

Yup, crane. [2] has a ton of photographs and descriptions of the various structures on this class of ship. DMacks (talk) 06:59, 9 March 2016 (UTC)

As to the 6 handles. They are securing a curved watertight door to a curved structure & protecting an otherwise exposed electrical motor ... I suspect 6 were necessary to ensure watertightness ... one on each corner & two in the middle. By the looks, the crane was operated from above the circular platform we see - see the photo in this discussion - [3] - and so I guess the door provided access for maintenance purposes (i.e. quite rare) rather than for operation. All speculation, of course. --Tagishsimon (talk) 07:12, 9 March 2016 (UTC)

I'm surprised that Wikipedia does not have a watertight door article. The closest we seem to come is Compartment (ship)#Doors. Multiple dogs (see Dog (engineering)#Hatch dogs) are necessary to fully secure a watertight door whether it is sealing against a curved surface or a flat one. It is possible to connect the dogs together with lever mechanisms so that they are all activated simultaneously via a single wheel or lever, but this adds complexity which increases the cost of the door and its required maintenance. I don't know if such quick acting watertight doors were in use back in 1910, but individually acting watertight doors are still used extensively today where there isn't sufficient traffic to justify a quick acting one. Ships will often have small deck houses solely for providing access to a companionway (steps) to a lower deck (the alternative being a deck hatch and ladder), but they are typically smaller than the "white cylinder" in your images and often sloped on the side opposite the door. I think that DMacks and Tagishsimon are right on target and it is the base of a 2-1/2 ton electric crane. See this photo. I also concur with them regarding ventilator cowl for #3 and bitts for #4. -- ToE 14:28, 9 March 2016 (UTC)

Quick acting watertight doors were provided on the Titanic, designed and built around 1910. They were controlled electrically from the bridge. Akld guy (talk) 17:55, 9 March 2016 (UTC)

"What are the two black barrels/posts to the right of the sailors?" I think they're called bollards. Rope used to tie up the ship is passed between them, and they're designed to be strong enough to resist movement fore or aft. Ah. Also called bitts, mooring bitts, double bitt bollards, &c. --Tagishsimon (talk) 09:34, 9 March 2016 (UTC)

What is this US Navy electronic thing?

A friend found this at a ham radio club flea market - https://farm2.staticflickr.com/1502/25650380485_f00cde1ba4_o.jpg What is it? Roger (Dodger67) (talk) 19:29, 9 March 2016 (UTC)

It might help if we could read the top line of labels. Can you add that info ? StuRat (talk) 19:47, 9 March 2016 (UTC)

I see it was made by General Mills. Some sort of electric pastry warmer ? :-) StuRat (talk) 19:50, 9 March 2016 (UTC)

The main selector switch appears to be "OFF","W/H SAFE","W/H ARMED" and the red label says it came from the Bureau of Ordnance's Naval Ordnance Laboratory. So "W/H" is probably "warhead", and this is either a controller or some sort of dummy simulator for a weapon system of some sort. DMacks (talk) 19:58, 9 March 2016 (UTC)

Much better than what (talk) suggested and accurate as well. As for General Mills, I've personally fired a M2 Browning made by IBM and another made by the Singer Sewing Machine Company. Who has the equipment at a specific era makes the device for the government.Wzrd1 (talk) 20:16, 9 March 2016 (UTC)

Likewise, Remington (the gun makers) and Remmington (the shaver and hair-care-products maker) used to be the same company (which also made typewriters). Iapetus (talk) 14:26, 10 March 2016 (UTC)

The markings I could decipher are:

USN = United States Navy

BUORD = Buro of Ordnance - 1862 to 1959 when it became the Buro of Naval Weapons (BUNAVWEPS)

NAVORDLAB = Naval Ordnance Laboratory

White Oak = a part of Silver Spring, Maryland. In 1993 the site was transferred to the Food and Drug Administration when many of the naval facilities around and near Washington DC were consolidated in the Washington Navy Yard.

General Mills established its Electronics division in 1946 so that sets the earliest date, the latest is 1959, when the label would have changed from BUORD to BUNAVWEPS.

Sorry, this photo is all I have currently. Roger (Dodger67) (talk) 20:19, 9 March 2016 (UTC)

I'm really going to have to start going to flea markets, especially since we've relocated to just outside of Barksdale AFB.  ;)Wzrd1 (talk) 20:22, 9 March 2016 (UTC)

This [4] covers a lot of "test set" equipment the navy uses to test missiles and such. They list diagrams for many similar sized gizmos with TS-XXXX numbers. Your example has T-3026 and says "test set". So I think it's a test set for testing ordnance, basically per DMacks. Here [5] is a very nice page listing the manuals for many bits of testing equipment the Navy used in that era, but it only covers radio test equipment. I suspect the owner of the website could be contacted for further assistance, as he has a lot of knowledge and interest in US Navy electronics of the era. SemanticMantis (talk) 21:11, 9 March 2016 (UTC)

As a hunch, it might have something to do with torpedoes. Shock Brigade Harvester Boris (talk) 04:13, 11 March 2016 (UTC)

Why during a total solar eclipse one can't see stars?

On almost all photos of a total solar eclipse stars are not visible. Thanks.--93.174.25.12 (talk) 20:58, 9 March 2016 (UTC)

Even during a total eclipse, there still is sunlight from the corona to light things brighter than the stars.Wzrd1 (talk) 21:14, 9 March 2016 (UTC)

They are not visible without any eclipse either. Light pollution. --AboutFace 22 (talk) 21:18, 9 March 2016 (UTC)

In fact, at totality it is possible to see stars in the sky - but only if you look well away from the sun. As the photos of an eclipse are all looking right at the sun, there is too much light from the corona for the stars to be visible in the area of sky close to the sun.109.150.174.93 (talk) 21:20, 9 March 2016 (UTC)

I can report from personal experience in France in 1999 that it's possible to see the corona during a total solar eclipse even if there is a thin layer of cloud. I would not expect to see stars in that situation. This shows how bright the corona is, and supports what 109.150 says.--69.159.61.172 (talk) 21:26, 9 March 2016 (UTC)

I've heard that the corona's only as bright as the full moon (when there's a reasonable amount of totality, not when you're seeing pink chromosphere with the naked eye). They average 2 minutes, 7.5 minutes max which is not be enough time for the eyes to adjust much to the lack of daylight. And Guy Ottewell's Astronomical Calendar seems to imply that you could see planets and extremely bright stars (also most people stare at the Sun instead of the darkest part of the sky for the rare stars bright enough (like Sirius) because the star thing is just twilight which is pedestrian but totality's so beautiful and rare (2 minutes every 360 years if you don't travel (on average))). Sagittarian Milky Way (talk) 00:00, 10 March 2016 (UTC)

I think I remember now that large distances from the edge of totality are key (low sun helps) and those eclipses are usually inconvenient and rare: I used an eclipse search engine to find when parts near or on the centerline of eclipses magnitude 106.2% to 108.1% (the maximum) were on land with low sun. I was wondering what the most recent one that many Westerners saw was. The unabridged list is 2009 India during the monsoon, 1991 Hawaii (Big Island only) and Amazon (most people went to Baja because they didn't know that the desert would be cloudy and Hawaii would be clear), 1973 Guyana/Suriname, 1940 Colombia 1937 Micronesia? and Peru (not Titicaca), 1922.. and many more like and it was not until 1733 Gotland and 1724 Alps where a deep eclipse with low Sun was seen by many Westerners (and kind of before the Enlightenment when people cared about these things). So I can see how a myth of no stars during an eclipse might develop outside Hawaii. I might remember something about someone staying dark adapted till totality and then looking at the stars before watching the Sun. So the next time you see an eclipse (2017 USA?) be blindfolded pitch black the entire half hour or more before totality and then see the stars in the few seconds while the streetlights have just lit and are still weak. Sagittarian Milky Way (talk) 01:39, 10 March 2016 (UTC)

http://www.enchantedlearning.com/subjects/astronomy/sun/solareclipses.shtml says "During totality the sky is dark enough to see stars in the sky". Loraof (talk) 21:28, 9 March 2016 (UTC)

And varoius other sites say the same thing--google "seeing stars during total eclipse". Loraof (talk) 21:31, 9 March 2016 (UTC)

There's a detail here worth noting. The original poster asks specifically about photos of a solar eclipse. The thing is, you can't photographically capture both stars and a much brighter object like the Sun (as mentioned above, there's still light from the Sun's corona even during a total solar eclipse) at the same time. This is an issue of optics. This is also an issue in space photographs, and is sometimes brought up by uninformed people as "proof" that photographs from the Apollo missions are fake because you can't see stars in them. Here's an article about this and other aspects of the Apollo pictures. --71.119.131.184 (talk) 21:46, 9 March 2016 (UTC)

You can do it as a composite pic:

1) Take one pic of the solar eclipse.

2) Take a pic with the area of the eclipse and corona all blocked off, so the stars are visible This would require exceptionally clear skies, so a pic from a mountaintop observatory would be best, or better yet from Hubble, to avoid scattering of the light from the eclipse.

3) Combine the two images into one composite. StuRat (talk) 23:21, 9 March 2016 (UTC)

The corona and stars can be captured in the same image, but the stars are very difficult to discern. For the most famous example of this, see Solar eclipse of May 29, 1919. {The poster formerly known as 87.81.230.195} 185.74.232.130 (talk) 14:18, 10 March 2016 (UTC)