Wikipedia:Reference desk/Archives/Science/2011 October 17

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October 17

Redox question

Lets say we combust hydrogen with oxygen. The hydrogen is oxidized so the electrons surrounding it move from a higher energy state to a lower energy state, and it gives off a photon as a result yes? What kind of photon is it? ScienceApe (talk) 02:46, 17 October 2011 (UTC)

What are the options? I thought there was only one kind of photon. Vespine (talk) 03:04, 17 October 2011 (UTC)

Microwave photon, radio wave photon, visible light photon, ultra violet ray photon etc. ScienceApe (talk) 03:09, 17 October 2011 (UTC)

Oh right, I didn't think of that as different kinds, it's a continuous spectrum rather then "discrete" types, but that's fine, I don't see why you can't call them different kinds. In which case I'm pretty sure you get photons from the the top end of of infra red and the bottom end of the visible range. Vespine (talk) 03:17, 17 October 2011 (UTC)

Read hydrogen#Combustion, apparently most emissions are ultraviolet, and the flame is invisible. Graeme Bartlett (talk) 03:31, 17 October 2011 (UTC)

Related question, lets say you are burning wood. What photons are emitted from the electrons then? ScienceApe (talk) 14:54, 17 October 2011 (UTC)

Here's a study of the emmission spectra of the burning of "wildland fires"; i.e. the burning of vegetation in the wild, likely including wood. This should be pretty close to what you are looking for. There are also references there which lead to more articles on the topic. --Jayron32 16:14, 17 October 2011 (UTC)

I just want to acknowledge the terrible assumption I made above, I had no idea that combustion of hydrogen emits ultraviolet light. I knew arc welding did, but didn't expect that hydrogen would too.. Vespine (talk) 21:39, 17 October 2011 (UTC)

So.... Infrared then? ScienceApe (talk) 23:50, 17 October 2011 (UTC)

Flames are visible because soot products exhibit incandescent glow, ranging from yellow to blue in appearance (see Black-body radiation). elle _{vécut heureuse} ^{à jamais} (be free) 11:19, 20 October 2011 (UTC)

May-December Marriage -- Marriage Age Difference

What articles here cover this topic and where can I find a list of marriage age difference related statistics such as duration, income bracket, etc. --DeeperQA (talk) 03:11, 17 October 2011 (UTC)

See Age disparity in sexual relationships. Dismas|^(talk) 03:58, 17 October 2011 (UTC)

Which is the better DIY telepresence robot?

Robot A or robot B? Which elements of each are better than the corresponding elements of the other? Dualus (talk) 03:51, 17 October 2011 (UTC)

Better in what sense? They seem to me like they'd be better in very different sorts of situations. The laptop-on-a-carriage is cool but seems rather fragile and bulky. The iPhone-in-a-Roomba would have worse visibility but would probably be more maneuverable. There are no doubt other issues relating to power usage. "Better" will depend on what you are prioritizing. --Mr.98 (talk) 14:45, 17 October 2011 (UTC)

Which would make a better docent for a children's museum? I think they may both be on Roombas. Dualus (talk) 16:14, 17 October 2011 (UTC)

Is this related to XKCD strip 413: New pet? – b_jonas 17:08, 17 October 2011 (UTC)

Well, vaguely, in the sense that I gave my Android Accessory Development Kit to an MIT student named Aaron who said he was going to work on one of those, but without the external camera, months ago. I think you're right in that those might be good docents. Dualus (talk) 17:51, 17 October 2011 (UTC)

I hope he replaces the camera. Dualus (talk) 23:14, 18 October 2011 (UTC)

Volkswagen TwinDrive

We were promised a ~$22K BMW/VW plug-in hybrid car for the people. What happened? Dualus (talk) 03:51, 17 October 2011 (UTC)

It ain't here yet. Check back in 2015.

APL (talk) 05:17, 17 October 2011 (UTC)

@#$%&*! Dualus (talk) 09:51, 17 October 2011 (UTC)

Generating MIST from still water

How much velocity / acceleration (linear) is needed to be imparted to water lying at rest (at atmospheric pressure) to convert it into MIST ? (pipeyoga 17:10, 14 September 2011 (UTC))

<Copy-paste of a bunch of clutter from the archives removed -- Looie496 (talk) 15:54, 17 October 2011 (UTC)>

Gentlemen, is there any other forum inside wiki wherin I can post this query ? (pipeyoga 15:42, 17 October 2011 (UTC)) ... I still havent got any reply on this one ...!! — Preceding unsigned comment added by Pipeyoga011 (talk • contribs)

Obviously nobody who read this page knows an answer. There is no use shouting. Looie496 (talk) 15:54, 17 October 2011 (UTC)

My Apologies .. as I forgot that BOLD font means "shouting "... I was merely trying to differentiate from previous posts ...but thanks for reminding me ...the basics ( pipeyoga 15:59, 17 October 2011 (UTC)) — Preceding unsigned comment added by Pipeyoga011 (talk • contribs)

This looks like a job for COMSOL Multiphysics -- if you ask them nicely, they will give you a free 30 day evaluation CD and key. Tell them you've stumped the Wikipedia Science Reference Desk and you will publish your results here. Dualus (talk) 16:15, 17 October 2011 (UTC)

It's not really clear to me what you are trying to measure. Mist is generally very small droplets of liquid water suspended in air. You can certainly turn a bucket of water into mist, but the amount of energy involved is strongly dependent on the machine used (e.g. spray misters with hoses, vibrational misters, etc.) and the size of the droplets required. In addition, depending on the apparatus it is not clear why measuring a velocity or acceleration is a natural thing to look for. If you want to turn water into water vapor (which would generally be described as "steam" rather than "mist") then there is a clearer answer for the amount of energy involved (which depends on the starting temperature and the mass of water), but it still isn't clear why you'd want to measure a velocity. Perhaps if you can more clearly describe the situation that you are imagining we would be better able to help. Dragons flight (talk) 18:11, 17 October 2011 (UTC)

It is clear to me. He wants to know what velocity of wind is required at the surface of perfectly still water to cause a droplet of water to break the water tension and float up into the wind. Because that scenario is not possible to replicate, I'm not certain it is possible to measure. Blowing wind over water will cause it to stop being perfectly still. -- kainaw™ 18:17, 17 October 2011 (UTC)

This article from Nature looks like it might have some promising leads. It may not directly answer the OP's question, but if one follows the references therein, or searches for similar articles, there may be somewhere to go. --Jayron32 19:28, 17 October 2011 (UTC)

Vaporiser?

From an energy stndpoint you have to do two things - 1 create a series of droplets. This means creating more surface area, for which a certain amount of energy is required. Then you have to disperse the droplets. If you do this vertically then they will gain gravitational potential energy. So the amount of energy assuming 100% efficiency = 1/2*m*g*h+A*FSE where h is the height of the mist cloud, m is the mass of the water, g is gravity A is the total surface area of the droplets and FSE is the energy per unit area to create a free surface. Implementation is left to the OP. Greglocock (talk) 03:17, 18 October 2011 (UTC)

Try Beaufort scale. Hurricanes, breaking waves and the Niagara Falls have mist, while calm open seas generally do not. See also salt spray. ~AH1 ^(discuss!) 02:21, 19 October 2011 (UTC)

I'm quite interested in the physical chemistry implied by this question. How would one measure the entropy of misting? Surely mist has a different molar entropy from bulk water, but not the same as water vapor? elle _{vécut heureuse} ^{à jamais} (be free) 11:18, 20 October 2011 (UTC)

The psychology and science behind folk dentistry

I realize many people *are* afraid of dentists... most likely due to the inevitable pain that most will be afflicted by, even if only through the needle for the anesthetic...

But is there any reason why one would not only *not* be afraid of dentists, but actually enjoy the experience? (The operations themselves mostly, not the pain.) Is there an established psychology theory behind it, or even better, any science that explains that? 62.255.129.19 (talk) 16:25, 17 October 2011 (UTC)

This is tangential to the question, but my understanding (and my experience over the last several years) is that dentists, periodontists, and oral surgeons will apply a topical anesthetic (typically benzocaine, xylocaine, or similar in a gel preparation) to numb the gums before they insert the needle for the nerve block. Is this standard procedure now, or have I just dealt with the most tenderhearted of dental practitioners? TenOfAllTrades(talk) 17:08, 17 October 2011 (UTC)

My dentist does that. Doesn't (or didn't in my case) work when receiving a needle under the top lip. That's the worst place, in my experience. Felt like my face was trying to jump off my skull - and immediately made my eyes and nose stream. --Kurt Shaped Box (talk) 20:24, 17 October 2011 (UTC)

Anecdotal: I quite enjoyed the experience of having my wisdom teeth removed. I was in a teaching facility, and there were many other procedures going on around me. A steady stream of nitrous oxide and twilight sleep meds turned the cacophony of drills into a beautiful symphony, at least for a few minutes before I went under :) SemanticMantis (talk) 17:19, 17 October 2011 (UTC)

TenOfAllTrades, yes, that's what my local dentists do around here too (specifically lidocaine was used). SemanticMantis, I can imagine that being pleasurable, but weirdly enough, even though I was only applied a topical anesthetic and as such never went under, I still enjoyed it (although not the 'noise' of the drill, at all, just generally). 62.255.129.19 (talk) 17:28, 17 October 2011 (UTC)

Do you also enjoy getting your hair cut? In some ways minor dentistry is similar... SemanticMantis (talk) 18:02, 17 October 2011 (UTC)

You are so right on this last comment, SementicMantis. Both professions, hair cutters and dentist, were even the same in the past. Believe it or not. 88.8.75.87 (talk) 18:53, 17 October 2011 (UTC)

Indeed; though our article sucks, the modern term for such practitioners were barber surgeons. The medieval barber was expected to, besides cut hair and trim beards, perform surgery and tooth extractions. From a personal experience, I find the experience of a barber to be different than that of a dentist, because most barbers don't work in places which obstruct my airway... --Jayron32 19:00, 17 October 2011 (UTC)

Map scaling

Can someone please help me on this question on maps: Which scale is the biggest? a) 1:50000 b) 1:10000 c) 1:150000 Can you also please give a explanation for your answer? Thank you! — Preceding unsigned comment added by 41.18.66.69 (talk) 16:48, 17 October 2011 (UTC)

There really is no single answer. The scale 1:10000 makes objects in the map the biggest, but the scale 1:150000 makes the total area represented by the map the biggest. Looie496 (talk) 16:57, 17 October 2011 (UTC)

What these numbers mean is that, taking case (a) above as the example, any length you want to measure on the map represents that length times 50,000 in reality. So if you measure a 2cm distance between two points on the 1:50,000 map, the distance in reality is going to be 100,000cm. Answer (b) is going to be the largest physical map. Answer (c) will let the map represent the largest area. Comet Tuttle (talk) 17:01, 17 October 2011 (UTC)

You may also be interested in map projection to get a broader overview as map projections inevitably involve distortions too. Sean.hoyland - talk 18:50, 17 October 2011 (UTC)

Perhaps the OP just wants to know what 'large scale' and 'small scale' mean when applied to maps. A given feature on the ground is drawn larger on a large scale map than on a small scale map. According to Wikipedia tradition, you have to work out whether that means (a), (b) or (c). --Heron (talk) 19:07, 17 October 2011 (UTC)

A straightforward guide to map scales is here. Alansplodge (talk) 08:53, 19 October 2011 (UTC)

Do parrots copy human mannerisms?

See these videos. Question as topic. Any ideas? --Kurt Shaped Box (talk) 20:13, 17 October 2011 (UTC)

Yes. And, at the risk of a blatant point of view, it is awesome. Dualus (talk) 21:44, 17 October 2011 (UTC)

I thought the OP meant gestures rather than speech. μηδείς (talk) 22:55, 17 October 2011 (UTC)

Maybe speech is like a gesture to a bird. 67.6.179.27 (talk) 06:59, 18 October 2011 (UTC)

Here's another example:[1] ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:36, 18 October 2011 (UTC)

Fossils in the future

Hello, I am interested in fossils and have a rock collection. As I understand it, some of the most "recent" fossils date back to the Holocene era (about 10,000 years ago), so I have 2 questions: 1. When can we expect to start finding fossils of human presence, such as ax heads and such? Second, and most interesting to me, what will be the most likely fossils found of modern man in the next 10,000 years? Beer cans? Automobiles? Glass bottles? Other stuff? Thanks! Quinn ^{❀ BEAUTIFUL DAY} 22:22, 17 October 2011 (UTC)

I have a young friend who is excited by the prospect of one day being a fossil. See subfossil. μηδείς (talk) 22:57, 17 October 2011 (UTC)

Anatomically modern humans have been around for something like 200,000 years, and plenty of fossils of their/our bones and artefacts have been excavated. Most people would extend the term "human" to cover, at the very least, Archaic "Homo sapiens", which takes us back a further 300,000 years, if not to earlier hominids predating Homo sapiens.

The study of such fossils is called Paleoanthropology, and overlaps considerably with Archaeology which (as our article suggests) can be considered to cover everything human-related from 3.4 million years ago to the present. Note that while fossils are most commonly thought of as being only the mineralised remains of organisms, the term originally meant anything dug up, including tools and other artifacts; moreover, even fossils of organisms millions of years old are not necessarily entirely mineralised. Conversely, stone axes and other tools are already mineralised, so cannot become "more fossilised" over time. {The poster formerly known as 87.81.230.195} 90.197.66.153 (talk) 23:52, 17 October 2011 (UTC)

I look forward to one day eventually becoming a coal ball. →Στc. 00:01, 18 October 2011 (UTC)

If it needs to be said, the chance that any one individual will become a fossil is exceedingly rare. The strange thing isn't that we have so called "gaps" in the fossil record, it's that we even have fossils to begin with. The conditions have to be extremely specific for fossilization to occur. The far FAR more common fate of all life forms is simple decomposition and 'recirculation'. Vespine (talk) 00:38, 18 October 2011 (UTC)

My teenage son thinks I'm an old fossil already. Mitch Ames (talk) 12:03, 18 October 2011 (UTC)

We already have Bronze Age artefacts. ~AH1 ^(discuss!) 02:19, 19 October 2011 (UTC)

Hummingbird speech?

This article http://www.bbc.co.uk/news/magazine-14930062 says that not only some songbirds and parrots but also hummingbirds mimic speech. I've never heard of it. Is it true? μηδείς (talk) 23:08, 17 October 2011 (UTC)

I think you are over-interpreting the article. It says that songbirds, parrots and hummingbirds can learn new sounds, but not that those new sounds are necessarily imitations of human speech. That they sometimes are in the case of some songbirds (most famously some species of Corvidae) and parrots does not necessarily mean that the same applies to hummingbirds. On the other hand, it might, but since hummingbirds are rarely kept as pets in the same way as some of the other two groups, the opportunities to observe the phenomenon in them may hitherto have been limited. {The poster formerly known as 87.81.230.195} 90.197.66.153 (talk) 00:07, 18 October 2011 (UTC)

Note BTW that the BBC article is out of date - Psittacopasserae includes parrots, songbirds, and nothing else, and so likely these capabilities evolved just once for that group. Not sure about the hummingbirds though. Wnt (talk) 16:20, 18 October 2011 (UTC)

Interesting, I follow such things closely but had not heard of the parrot/songbird link until now.μηδείς (talk) 18:26, 18 October 2011 (UTC)

I guess I should have DYK'd it, but didn't get around to it. Wnt (talk) 20:23, 19 October 2011 (UTC)