Science desk
< April 28	<< Mar \| April \| May >>	April 30 >

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.

April 29

question regarding phsyics

why inertia have very miner effect (as compared to the passenger) on the driver of a vehicle? explanation: it is clearly noted that if the driver of a vehicle applied the brakes . then all of the passengers experience a force on them called inertia. and in the result all the passengers strikes there heads to there next seats,but driver of the vehicle feels very miner effect of that inertia . why?? — Preceding unsigned comment added by 139.190.40.237 (talk) 07:27, 29 April 2016 (UTC)[reply]

The driver has a steering wheel and foot pedals to push against, and additionally can exactly anticipate the inertial force she is responsible for as she pushes the brake pedal. So the driver is better placed to react to the inertial force applied; but in all other respects, she is subject to the force in exactly the same way as the passengers. --Tagishsimon (talk) 07:39, 29 April 2016 (UTC)[reply]

Agreed. If driver's didn't suffer from the same inertia we wouldn't need driver's side steering wheel airbags. StuRat (talk) 16:13, 29 April 2016 (UTC)[reply]

Burning quartz glass

What would it take to make any detectable "bubble" inside a piece of fused quartz glass? Can a DVD/BluRay laser be focused to do this? Bytesock (talk) 07:28, 29 April 2016 (UTC)[reply]

You need a fairly high power laser to do that sort of thing, see [1]. Dmcq (talk) 08:44, 29 April 2016 (UTC)[reply]

Does that apply even if the bubble only needs to be like 1 µm in diameter and the time to accomplish it can be long? The critical equation is if the amount of energy applied in the form of photons will be larger than the energy removed by thermal conduction at a temperature high enough to distort the material. Bytesock (talk) 14:47, 29 April 2016 (UTC)[reply]

Bilbana

What is the latin name for the bilbana tree? Röd Boll (talk) 09:17, 29 April 2016 (UTC)[reply]

"Bilbana" does not appear to be the English name of any tree. As far as I can find, it only means car track in Swedish. Looking for trees, I'm seeing Musa balbisiana, a type of banana tree. Ian.thomson (talk) 09:24, 29 April 2016 (UTC)[reply]

I did not ask about the English name. Röd Boll (talk) 12:45, 29 April 2016 (UTC)[reply]

Ok, in what language do you think "Bilbana" is a name for a tree? Maybe you misheard the name "Bilbana", and it is known as something similar. E.g. biloba - Ginko biloba, or perhaps bilbao - Baobab tree- Adansonia. SemanticMantis (talk) 13:24, 29 April 2016 (UTC)[reply]

Yeah the ultimate point is unless we know what tree you're talking about we can't help you. Since this is the English wikipedia, and given the phrasing of your question, the logical assumption is your were referring to a tree called bilbana tree in English.

(To give a counter example, I would likely ask "What's the Latin name for the tree that in Malay is usually referred to by the name of the flowers 'bunga kertas'". Or "What's the Latin name for the tree that is called "pokok bunga kertas" in Malay. I would not ask "What's the Latin name for the bunga kertas tree?")

However it sounds like Ian.thomson did look for the word anyway and didn't find anything. Perhaps you'll get lucky and someone will recognise the name, but since it sounds like the name you're referring to is some obscure name and isn't the name in English, there's a very good chance this won't happen. So some details like where this name comes from or where you heard it, what the tree looks like or whatever will probably be essential.

Nil Einne (talk) 14:34, 29 April 2016 (UTC)[reply]

Bilbana is also a town in ancient Arabia mentioned by Ptolemy, but nobody knows where it is now. [2] Alansplodge (talk) 01:20, 30 April 2016 (UTC)[reply]

Did any trees grow there? Shock Brigade Harvester Boris (talk) 03:33, 30 April 2016 (UTC)[reply]

I think the name "bilbana" is from the Yale (Kosarek) language and it appears to be in reference to a tree ("kal" in the text) [3].174.131.63.119 (talk) 02:38, 1 May 2016 (UTC)[reply]

Magnetic field dependence on recording material?

Will a magnetic recording material that has a higher Oersted (Oe) rating induce a more far reaching magnetic field, after being set or recorded into. Such that a harddisk recording material specified as 1700 Oe the magnetic bit-cell in question reach further into the free space above it in relation to its size. Than say the field of a floppy disk at 300 Oe, in relation to its size? Ie can a harddisk magnetic head sense the magnetic field from a floppy disk surface at a further distance than an ordinary floppy disk head can? Bytesock (talk) 14:59, 29 April 2016 (UTC)[reply]

The newer HDDs now use Magnetoresistive heads (called GMR heads) instead of pickup coils. So the more strongly the material is magnetised, the more response it will give to the GMR head. Old style heads relied on change in flux density (B) when the head passed over the magnetised regions to induce voltage in the coils. I believe this actually relied on flux reversals being detected for each bit recorded on the disk.--178.103.251.111 (talk) 15:46, 1 May 2016 (UTC)[reply]

How did the Amazon Reef go undiscovered for so long ?

1) I would expect it to be visible from above, in the air or from space. Is the water particularly dark there, so the reef is not visible ?

2) And the hazard to navigation would seem to have required that it be mapped long ago, do no ships travel there ? StuRat (talk) 16:10, 29 April 2016 (UTC)[reply]

95% of the ocean floor is unexplored (for any given definition of unexplored. It is all technically mapped to a resolution of 5km/pixel using satellites). It is not entirely surprising when large structures get missed. It should also be noted that it wasn't suddenly tripped over in 2016 and someone said "Holy shit, there's a coral reef here we totally missed." A few factors, already noted in the article you linked make that concept wrong. First, it wasn't first discovered in 2016. It was first discovered in the 1950s, though at the time it wasn't fully evident that it was a functioning coral reef, just a large underwater structure. Second, as noted in the article you linked, scientists didn't think to look for a reef on said structure because reefs don't usually form at the mouths of rivers, so looking for a heretofore unidentified reef at the mouth of the largest river in the world seemed like a low-probability event, so they probably spent time looking for reefs elsewhere. It should also be noted that "discovered in 2016" is a bit misleading, it's more like "was slowly uncovered over 6 decades and finally published in 2016". Thirdly, it seems the reef is in deep enough water to not interfere with shipping channels because it hasn't interfered with shipping channels. I figured that one out on my own, because there are no reports of ships crashing the fuck into it. --Jayron 32 16:21, 29 April 2016 (UTC)[reply]

"Absence of evidence is not evidence of absence". Also, coral reefs need to be in shallow water, since they depend on sunlight to fuel them. So, that's why I am leaning towards the idea that shipping routes don't go through the area. Maybe currents coming out of the Amazon make shipping dangerous there ? As for the 95% figure, that applies to the depths of the ocean, not the shallows. And even having been undiscovered until the 1950's is still remarkable. StuRat (talk) 16:27, 29 April 2016 (UTC)[reply]

Not really that remarkable that it wasn't discovered until the 1950s. Until the 1950s, the Longest mountain range in the world was undiscovered. That a deep water coral reef was also missed until that time doesn't seem to odd. Until the advent of modern Bathymetry techniques during World War II, the ocean floor was basically entirely unknown. --Jayron 32 16:58, 29 April 2016 (UTC)[reply]

Coral reefs don't need to be in shallow water -> Deep-water coral. Sean.hoyland - talk 17:15, 29 April 2016 (UTC)[reply]

Not the best source but [4] suggests only the southern portion is significantly photosynthetic. Our article suggests something similar with another source. As for depth, many sources suggest 30m-120m [5]. I'm not sure what's the highest reach, but many sources suggest the reef is below the "freshwater “plume”, or outflow, of the Amazon". You can probably work out more by reading the published paper if you can understand it [6]. BTW as for being dark, the answer appears to be yes, according to some sources like the first one because of that very same outflow. Nil Einne (talk) 16:51, 29 April 2016 (UTC)[reply]

BTW this source [7] seem to confirm what I semi expected. This outflow is visible from space. (Of course visible from space or in satellite imagery or whatever depends significantly on the imagery system including resolution, lens, sensor size, what the sensor is detecting etc etc as well as the conditions at the time but the point is the reef not being very noticable in such imagery doesn't seem surprising.) Nil Einne (talk) 17:21, 29 April 2016 (UTC)[reply]

On shipping: draft_(hull) for Panamax shipping is 12 m. This reef is "30 to 120 metres deep". I don't know if boats commonly go there or not, but I don't think many boats have a draft of 30 m /100 feet below water line. Looks like even the Seawise_Giant (which is one of the biggest boats ever built) had a draft of "only" 25 m. SemanticMantis (talk) 17:37, 29 April 2016 (UTC)[reply]

The article doesn't say how deep below the surface the top of the reef is; the 30–120 m figure is for the depth of the surrounding water, i.e. to the bottom of the reef. I'd like to see figures on the height of the reef and how near it comes to the surface. --69.159.61.172 (talk) 04:23, 30 April 2016 (UTC)[reply]

Pillar coral is among the tallest coral in the world, and maxes out at about 3 meters. That still leaves a minimum of 27 meters below the surface, plenty of clearance for all but the most singularly unusual ships, such as the aforementioned Seawise Giant. --Jayron 32 05:12, 30 April 2016 (UTC)[reply]

That's the height of one coral colony, but doesn't one colony often build atop some other object, like a boulder or other species of coral ? StuRat (talk) 15:55, 30 April 2016 (UTC)[reply]

Since you're so sure ships are crashing into this reef, perhaps you can provide reports thereof. --Jayron 32 01:29, 1 May 2016 (UTC)[reply]

Adding water to aquifers

I heard on NPR that in California, despite drought, they dump water from reservoirs prior to what should be the rainy season, just in case they do get more rain than they can handle and have flooding. Would it be possible to use this water to replenish the aquifers, rather than letting it run out to the sea ? StuRat (talk) 16:21, 29 April 2016 (UTC)[reply]

Here is a website that explains how groundwater replenishment could work. --Jayron 32 16:23, 29 April 2016 (UTC)[reply]

OK, good, so it is possible. I saw that there is a relatively small project in Orange County, CA. Next Q, has anyone proposed expanding this in areas of the (US) West where aquifers are being quickly drained ? StuRat (talk) 16:35, 29 April 2016 (UTC)[reply]

They actually do that already. A major part of the Central Valley consists of permanent wetlands, and there are also specially designated flood zones such as the Yolo Bypass -- but in a wet year there is often too much water in the north anyway. Looie496 (talk) 17:28, 29 April 2016 (UTC)[reply]

This is my point. "Too much water" means an opportunity to add to the aquifers. StuRat (talk) 17:32, 29 April 2016 (UTC)[reply]

The Central Valley is astonishingly flat. You could build levees to keep in the water, but (a) you'd be sacrificing a lot of extremely productive land, and (b) the water table is close to the surface there anyway. Outside the Central Valley the only way to retain water is to build reservoirs. Looie496 (talk) 22:07, 30 April 2016 (UTC)[reply]

Does Central Valley (California) still have a high water table, despite the recent drought ? Central Valley (California)#Climate says "the more southerly parts in rainshadow zones are dry enough to be Mediterranean steppe (BShs, as around Fresno) or even low-latitude desert". StuRat (talk) 23:47, 30 April 2016 (UTC)[reply]

Shepherd's rose identification

In Rural Rides, William Cobbett is very complimentary about the fields of Hertfordshire, particularly the shepherd's rose in the hedgerows - "The hedges are now full of the shepherd's rose, honeysuckle, and all sorts of wild flowers, so that you are upon a grass walk, with this most beautiful of all flower gardens on your one hand, and with the corn on the other ... Talk of PLEASURE-GROUNDS indeed!" In A Year's Residence in the United States of America he regrets its absence from America "No shepherd's rose, no honeysuckle, none of that endless variety of beauties that decorate the hedges and the meadows in England". Now, what I want to know is this - what is our modern name for what Cobbett called the Shepherd's rose? DuncanHill (talk) 19:54, 29 April 2016 (UTC)[reply]

Tough one. Googling the name /"Shepherd's rose"/ gets you into old books by the second page. I found another old book that mentioned them in conjunction with blooming foxgloves. Along with the honeysuckle this strongly suggests we are searching for something that blooms in late spring/early summer. By the way, we have plenty of honeysuckle in the USA, and about 20 species are native to North America. Anyway, what are we looking for then? Something that is 1) an early summer bloomer 2) common in UK hedgerows 3)not common in USA at the time 4) Rose-ish by look. So my deductive and consistent guess is hollyhock: No natives to USA, it looks a bit rosy, it's taxonomically a Rosid, and the epithet of the common hollyhock is rosea. SemanticMantis (talk) 20:17, 29 April 2016 (UTC)[reply]

Hum, but you don't find them in English hedgerows, and they're not very rose-like. I was thinking of maybe a dog-rose or field rose, or some other native rose. DuncanHill (talk) 20:54, 29 April 2016 (UTC)[reply]

Interesting. I was only assuming you'd find hollyhocks in English hedgerows because I see them with some frequency on agricultural field edges here in the states. Oh well, hope someone else can help then. SemanticMantis (talk) 21:37, 29 April 2016 (UTC)[reply]

Hollyhocks are a common garden plant in the UK, but haven't "gone native" as far as I know. My guess is a dialect name for dog rose, but I couldn't find any proof. Curiouser and curiouser... Alansplodge (talk) 01:12, 30 April 2016 (UTC)[reply]

On the Popular Names of British Plants: Being an Explanation of the Origin and Meaning of our Indigenous and Most Commonly Planted Species, London 1863 by Richard Chandler Alexander Prior (p. 205) lists shepherd's cress, shepherd's needle, shepherd's purse, shepherd's rod and shepherd's weather glass, but NO shepherd's rose! I give up. Alansplodge (talk) 01:12, 30 April 2016 (UTC)[reply]

No shepherd's rose in W. Keble Martin either. DuncanHill (talk) 17:50, 1 May 2016 (UTC)[reply]

Possibly another name for the dog rose (Rosa canina) which is common in the UK but not native to the US [8]. The common name of most wild plants in the UK have many regional variations. Richerman (talk) 06:13, 30 April 2016 (UTC)[reply]

The OED defines it as "? some species of rose growing in hedges." So I guess the official answer is that nobody knows the exact species he was referring to. --Heron (talk) 08:04, 30 April 2016 (UTC)[reply]

I live in Hertfordshire at present, and dog rose is certainly very common here in early summer. Alansplodge (talk) 12:49, 30 April 2016 (UTC)[reply]

Wikipedia:Reference desk/Archives/Science/2016 April 29

Contents