Science desk
< December 3	<< Nov \| December \| Jan >>	December 5 >

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.

December 4

semi-starvation and multivitamin supplements

Medical Question Removed. APL (talk) 00:06, 4 December 2011 (UTC)[reply]

Request for identification

Please, if possible, help me identify the cloud and crab. The cloud was seen looking south from the summit of Mount Merapi in northern Sleman, Indonesia. The crab was found at Bandengan Beach in Jepara, Indonesia; it is standing on a woman's size 36 (UK) shoe, so I estimate about 10 to 15 centimeters in width. Thanks Crisco 1492 (talk) 00:04, 4 December 2011 (UTC)[reply]

The cloud is either a Towering cumulus cloud or a Cumulonimbus cloud, likely a Cumulonimbus calvus as it has not yet formed its "anvil top" seen on fully mature cumulonimbus clouds. Taking a bit of a stab in the dark at the crab, but it looks like a Ghost crab, though I am not sure which species. --Jayron32 02:13, 4 December 2011 (UTC)[reply]

In the aviation community, this type of cloud is commonly known as "cumulo bumpus" because it's often associated with severe turbulence. 67.169.177.176 (talk) 05:49, 4 December 2011 (UTC)[reply]

The crab is a ghost crab (genus Ocypode). Possibly Ocypode kuhlii.-- Obsidi♠n Soul 07:52, 4 December 2011 (UTC)[reply]

UK shoe size 36 would be colossal, I think you mean EU (see comparison) Jebus989 ^✰ 13:45, 4 December 2011 (UTC)[reply]

one piece CP9 abilities?

would it be physically possible for a human to run on water/on air, or create a "scythe wind"(you move an arm or leg really fast; the "scythe wind" is the movement of air afterward) that could cut something (nevermind how much training you would need)? Heck froze over (talk) 05:21, 4 December 2011 (UTC)[reply]

No -- the area acting on the fluid is much too small for this. You could propel small pieces of paper/plastic through the air with the "scythe wind", but that's just about it. 67.169.177.176 (talk) 05:52, 4 December 2011 (UTC)[reply]

Mythbusters did a segment on the running-on-water bit. Busted. Deor (talk) 11:03, 4 December 2011 (UTC)[reply]

I saw a different documentary that had Chinese monks running on thin floating sheets of bamboo or some other material on water, and it seemed to work for short distances. As for "running on air", does freefall count? ~AH1 ^(discuss!) 21:03, 4 December 2011 (UTC)[reply]

Why wouldn't running on floating bamboo work? The buoyancy of the bamboo keeps you from sinking, it's no different from running on the deck of a boat (the buoyancy may be increased by the effects of surface tension if the sheets are designed correctly, which might trick someone into thinking there wasn't enough bamboo to provide the necessary buoyancy). --Tango (talk) 00:15, 5 December 2011 (UTC)[reply]

But then it's not technically "running on water". 67.169.177.176 (talk) 01:56, 5 December 2011 (UTC)[reply]

Let's link to our description of that episode: MythBusters (2011_season)#Episode 162 .E2.80.93 Running on Water

Isn't running on water essentially a question of how long/much the surface tension will hold/take, and how much thrust you can apply? Heck froze over (talk) 18:53, 5 December 2011 (UTC)[reply]

Exactly right -- and a human's feet simply don't have a sufficient area to support his/her body weight on water by surface tension alone. 67.169.177.176 (talk) 23:58, 5 December 2011 (UTC)[reply]

Article on environmental impact of production of electronics

Do we have an article about the environmental impact of the production of electronic equipment? Electronic waste is about the environmental impact of the disposal of electronic equipment, but I'm more interested in the impact of the production. I'm editing Mobile phone#Environmental impact and want to mention that - according to this web site - "A Swiss assessment has found that 40-50% of the environmental impacts ... occur during the ... manufacturing ...". A list of relevant articles here would help. And/or join in the discussion at Talk:Mobile_phone#Environmental.2C_end_social_effects. Mitch Ames (talk) 06:49, 4 December 2011 (UTC)[reply]

Wikipedia has the article “Computers and the environment” and formerly had the article “Electronics and the environment”. If you are able and willing to start an article “Environmental impact of manufacture of electronics”, please do so. The topic interests me very much. See All pages with titles beginning with Environmental impact of.

—Wavelength (talk) 17:52, 6 December 2011 (UTC)[reply]

Cricket Feet

I asked above for an identification of a cricket: http://wiki.riteme.site/wiki/Wikipedia:Reference_desk/Science#Unidentified_Cricket , and agree that the answer, spider cricket is correct. I also asked for an explanation of the fact that it has multiple digits on its limbs, i.e., "hands", rather than the normal unbranched limbs of arthropods. Looking at thge article arthropod leg (redirected from trochanter) provides no help. Can someone advise on this? The fact that cave crickets among all insects uniquely have hands seems noteworthy. Hurriquake (talk) 11:42, 4 December 2011 (UTC)[reply]

I don't see any 'hands' on your cricket. What I do see are a number of spikes around some of the joints of the legs, are these what you are referring to? I can only suggest (after some fruitless googling) that they are a sensory bristles which assist the cricket in interpreting its environment. Particulary useful in a lightless cave. On the ends of all the crickets and grasshoppers legs that I have examined closely there have been one or two hooked claws which seem to be slightly articulated. OR but the best I can do. Richard Avery (talk) 12:45, 4 December 2011 (UTC)[reply]

A bit off-topic but Trilobites had spikes on the inside of their upper leg joints, in their case the spikes were used to rip up and guide food particles along the midline of the animal towards the mouth, making something called a gnathobasic jaw (the mouthparts had no teeth). I'm not suggesting that this cricket uses those spikes in the same way, just that spikes on leg joints are common enough in the arthropods. Mikenorton (talk) 14:56, 4 December 2011 (UTC)[reply]

Such spikes are called 'apical spines' I think, and I might speculate that they could also have a role in trapping prey, but that's just more OR I'm afraid. Mikenorton (talk) 15:33, 4 December 2011 (UTC)[reply]

There are two types of appendages in arthropods - uniramous and biramous appendages. A biramous appendage is one which branches out at a segment. Crustacean limbs for example are biramous. The most obvious example being their uropods (the "tail fan" in e.g. lobsters and shrimps) which are actually composed of a pair of appendages that branch out into two platelike "fins" each. Note however that the crustacean claw (chela), is not an example of biramy, as the fixed "segment" is actually merely an extension of the propodus, the segment behind the tipmost segment (the dactyl). While the appendages that hold the chelae are also biramous, the branches are way down at the base - the gills, which are actually the exopods (the claw bearing larger branch is the endopod). See illustration.

Uniramous legs are those which are only composed of successive segments with no branching whatsoever. All insects have uniramous legs. Those on the cave crickets are not true branching segments. Rather they are outgrowths of the tarsomeres (the individual "segments" of the tarsus, the "foot" of the insects). To put it simply (as Richard Avery already pointed out), those are spines not "fingers", including the two "claws". They have multiple functions. Claws are obviously for gripping; the large backward pointing tibial spurs are for a larger area of contact on surfaces when jumping or swimming; the spines on the tarsus are for regular walking and running; all of them have some defense functions (in the related wetas, the spines are formidable enough to deter reptilian predators); and lastly they are used for cleaning (acting like a comb).

The trochanter is a whole other matter. It's simply the segment after the coxa, both are the segments most proximal (closest) to the body. In human anatomy, they would be the hip and the shoulders, I guess.-- Obsidi♠n Soul 16:14, 4 December 2011 (UTC)[reply]

magnetic influence on water molecule clusters

We have indeed heard a lot of inputs on how magnetic water would help in breaking water molecule cluster size and how nutrients can travel effectively through cell membranes when water molecule exists as single molecules. Can you throw some light in these inputs. — Preceding unsigned comment added by 117.206.238.166 (talk) 14:14, 4 December 2011 (UTC)[reply]

Magnetic water treatment? ~AH1 ^(discuss!) 20:48, 4 December 2011 (UTC)[reply]

What's more dangerous propellant or the explosive warheads?

Lets say you have a naval warship with a large bore cannon that fires large shells with explosive warheads. If the ship takes hits by the enemy, what's more dangerous or more likely to blow up and destroy the ship, the propellant or the explosive warheads? ScienceApe (talk) 14:39, 4 December 2011 (UTC)[reply]

The cases of HMS Hood (51) and USS Arizona (BB-39) are instructive, as both suffered catastrophic failure that is believed to have been caused by hits on their magazines; that is, gunpowder storage. — Lomn 15:17, 4 December 2011 (UTC)[reply]

As far as I can tell, for battleships of that era, the cordite propellant magazine and the shell room were either horizontally or vertically adjacent to one another. So if the cordite was ignited (which is surely easier than the shells being triggered) and the propellant magazine becomes fully involved, doesn't the intense heat of this destroy the plating between the two spaces and cause the shells themselves to cook off? That is, just because the cordite was burning doesn't necessarily mean that's what sank the ship, but just that's what triggered the shells to explode and shatter the ship. -- Finlay McWalterჷTalk 15:51, 4 December 2011 (UTC)[reply]

I guess I'm suggesting that if Hood and Arizona had only carried a full magazine of cordite but no shells, wouldn't the burning cordite (while intensely hot) have simply melted the surrounding decking, framing, and plating, perhaps eventually china-syndroming through the hull. But Hood exploded with such force as to break the whole hull in two. Can even a large mass of low explosive like cordite, loosely contained and being triggered haphazardly, really generate enough force to promptly fracture the steel hull and heavy steel armour of a battleship over a long enough locus to break the hull outright? -- Finlay McWalterჷTalk 16:10, 4 December 2011 (UTC)[reply]

You've got different characteristics that come into play. High explosive is going to be more damaging but is less sensitive and there is less of it. Propellant is a lot more sensitive but will generate less damage. There is a lot more of the propellant, and the burn is a bit slower than HE.

One of the things you'd start seeing would be secondary effects. The propellant would create a hot enough burn that you'd get HE explosions as a result.

Something else to factor in, if the incident isn't enough to create fatal damage, is that the HE will melt and when cooling goes into a very sensitive crystalline state that makes clearing the debris very dangerous.

ALR (talk) 15:43, 4 December 2011 (UTC)[reply]

This naval history forum thread makes reference to the film of the sinking of HMS Barham which the poster describes as "a cordite deflagration very fast enveloping entirely the ship and maybe causing other chain effects". You can see the film here. If enough cordite burns fast enough in a confined space (such as a sealed and armoured magazine), does it not explode? Another factor to consider is that the majority of projectiles carried in capital ships were Armour Piercing shells rather than High Explosive shells. AP shells (known as "Common Pointed Capped" in British service) had a much smaller bursting charge than HE. Alansplodge (talk) 16:50, 4 December 2011 (UTC)[reply]

According to the article that you link to the explosion was attributed to the AA ammunition, stowed outside the ammunition storage. I don't know enough about ammunition stowage and regulations of the period to make any judgement. Modern methods developed quite fast and the most significant influence is the Forrestal fire.

High explosive is the normal use now in 4.5in and 5in guns, since the main use is for Fire Support rather than Anti-Surface.

Of course that rather highlights that nobody asked era, and what the ship would be hit with. I've assumed contemporary issues rather than the historic context. In that instance you'd be looking at either missile threat or potentially a fast moving surface threat; (Boghammar).

ALR (talk) 22:54, 4 December 2011 (UTC)[reply]

I've re-read the linked article and I'm not sure that it actually does say that "the explosion was attributed to the AA ammunition". Anyway here ia a transcript of the Admiralty enquiry into the loss of the Hood. If you will allow me to pick out the salient point of the findings:

"From the last war (World War I) there are three examples of the effects on battle cruisers of cordite explosions - explosions which both in appearance and effect gave very similar results to those experienced in the loss of Hood... there is little room for doubt that the immediate destruction of the after end of the ship followed by the rapid sinking of the remainder would result from the blowing up of the 4-inch or 15-inch magazines - in the case of the former because their explosion would cause the 15-inch also to blow up. We conclude:
(1) That the sinking of Hood was due to a hit from Bismarck's 15-inch shell in or adjacent to Hood's 4-inch or 15-inch magazines, causing them all to explode and wreck the after part of the ship. The probability is that the 4-inch magazines exploded first.
(2) There is no conclusive evidence that one or two torpedo warheads detonated or exploded simultaneously with the magazines, or at any other time, but the possibility cannot be entirely excluded. We consider that if they had done so their effect would not have been so disastrous as to cause the immediate destruction of the ship, and on the whole, we are of the opinion that they did not.
(3) That the fire that was seen on Hood's Boat Deck, and in which UP and/or 4-inch ammunition was certainly involved, was not the cause of her loss."

So in all probability, Hood was destroyed by the cordite propellent exploding in her aft magazines, after the smaller one had been penetrated by a German shell. Alansplodge (talk) 23:53, 4 December 2011 (UTC)[reply]

This is all talking about WW2 era ships though right? And they used more conventional propellants. Is that still the case for modern ship-based artillery shells? Many military explosives these days are plastic explosives because of their superior stability and expansion rates. Just musing here... curious if anyone knows details. Shadowjams (talk) 07:21, 5 December 2011 (UTC)[reply]

You're quite right. There's a long discussion in the Hood report about the vulnerability of the large calibre charges, which were in silk bags and used (for technical reasons) old fashioned black powder detonators. As Boghammar says, modern warships use much smaller shells, the charges are in protected in brass cases and much safer detonators are fitted. Cordite is now obsolete and has been replaced by more stable propellants. Of modern RN warship losses, HMS Sheffield (D80) caught fire after bieng hit by an Exocet missile, and HMS Coventry (D118) was sunk after beig hit by bombs. In neither case was there an explosion of the magazines. HMS Antelope (F170) was set on fire by a bomb that was being defused and blew up when her Seacat missile magazine exploded.[1] The Type 21 frigates were infamous for being very lightly built and I imagine that newer warships have better protected magazines. This website advertises composite armour for naval ships which can be "used to protect mission-critical areas on board, including ammunition magazines". Alansplodge (talk) 09:19, 5 December 2011 (UTC)[reply]