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October 12

New Earth Like Planets

General question, The knew possible earth like planet reported in the news could be covered in water, with the current scientific methodology if this is so could we also assume it would have an oxygen rich environment or can water exist in fluid form with out producing any oxygen? 5.175.72.42 (talk) 09:19, 12 October 2016 (UTC)

We can't assume it has oxygen rich environment just because it has water. Our atmosphere is oxygen rich because early life on earth produced lots of oxygen. Fuortu (talk) 10:06, 12 October 2016 (UTC)

See Great Oxygenation Event. The Earth's atmosphere contained very little oxygen for the first quarter of its existence (despite the presence of the oceans). Tevildo (talk) 18:00, 12 October 2016 (UTC)

Is it possible through current scientific methods to see the makeup of the environment...as we do with in our solar system or is the exo-planet to far away? an aded question i know sorry. — Preceding unsigned comment added by 5.175.72.42 (talk) 11:14, 12 October 2016 (UTC)

An oxygen atmosphere can be abiogenic, if hydrogen is stripped away from the planet by solar wind. With the flare activity of young red dwarfs, this doesn't seem implausible. See Habitability of red dwarf systems for a mention of this. Here is the original paper: [1] Note it is simulation of a range of possibilities and doesn't actually say much. Wnt (talk) 11:45, 12 October 2016 (UTC)

We can often estimate an exoplanet's mass and orbit size by observing the motions of its host star. That, plus the brightness of its host star is enough to get a rough idea about its surface temperature (if one assumes it is a rocky planet). That gives us a clue about whether it might possibly be habitable for earth-like life. If the planet happens to pass directly in front of the star from our point of view, it is also possible to estimate the composition of the atmosphere by the nature of the small changes observed in the star's light during the time the planet is passing in front. Most planets don't happen to have orbits that pass in front of their host star. As far as I know there is no feasible way right now to learn about an exoplanet's composition if it doesn't happen to pass in front of host star. Dragons flight (talk) 12:09, 12 October 2016 (UTC)

• Tevildo's link above is the most relevant. Once photosynthetic organisms started producing carbohydrates and O2 from water and CO2; the oxygen they released was highly reactive, and it took millions of years for the oxygen and free iron dissolved in the oceans to "rust out" before O2 could accumulated in the atmosphere.

Super earths might be very tectonically active, still producing free iron long enough in their lifetimes to prevent the buildup of an O2 rich atmosphere even when we had long developed one. Hence the lack of free atmospheric O2 would not mean the lack of organisms producing it. The key in finding life will be whether the atmosphere is in a long-term chemical imbalance of some sort.

This book, [pubs.acs.org/doi/abs/10.1021/ed068pA112 The elements, their origin, abundance, and distribution (Cox, P.A.)] addresses the matter at length in its treatment of the atmosphere. μηδείς (talk) 00:26, 16 October 2016 (UTC)

Regenerating a li-ion battery?

Is it possible to regenerate a li-ion battery that has degraded due to normal use (that is, several cycles of charging and discharging)? I suppose the wikihow solution of putting the battery in the freezer does not help. However, is there an industrial scale refurbishing of old batteries? Maybe not for small smartphone batteries, but for hybrid/electric vehicles. --Llaanngg (talk) 10:23, 12 October 2016 (UTC)

Battery recycling generally involves taking the battery apart, melting down the components to separate out the valuable metals, and then using the resulting materials to build new batteries. At industrial scales, such recycling is often cheaper than buying freshly mined raw materials. However, that's not really a "refurbishment". As far as I know there is no simple process to restore the longevity of a li-ion battery. They degrade due to chemical and physical changes in the battery itself and I am unaware of any method of reversing those processes that doesn't involve scraping the battery. Dragons flight (talk) 12:17, 12 October 2016 (UTC)

(ec) The article Li-Ion#Battery life describes a variety of different ways that these batteries can degrade and there is no way to reverse them all. It is true that their life is longer if kept at low temperature and if a battery management system prevents operation outside each cell's safe operating area (max-charge, min-charge, safe temperature range). Experiments in reviving Li-Ion batteries by methods that have been suggested, such as "zapping crystal dendrites away with an electric welder" (that has been proposed to treat Nicad batteries that have an unrelated chemistry) are too dangerous due to the documented liability of Li-Ion batteries to explode. Thus the only option is to replace degraded Li-Ion battery cells with newly manufactured ones. Ideally old Li-Ion batteries should be recycled to recover their elements including iron, copper, nickel and cobalt but not much has been invested into recycling Li-ion batteries due to costs, complexities and low yield. AllBestFaith (talk) 14:28, 12 October 2016 (UTC)

"Several" discharge cycles should have no effect on the battery; it should take several hundred cycles at least for any noticeable loss of charging capacity. If you were being literal, and you have a battery that is new, it's defective and you should return it if it's under warranty. --47.138.165.200 (talk) 19:43, 12 October 2016 (UTC)

With "several" I meant enough wear and tear under normal circumstances to reduce its capacity, but nothing that would be covered by a warranty. Llaanngg (talk) 17:12, 13 October 2016 (UTC)

What's the Maximum cruise speed for Boeing 767 at 5000 ft?

And what's happening when the plane pass the cruise speed? 37.142.197.179 (talk) 12:51, 12 October 2016 (UTC)

Wikipedia has a general article on Cruise (aeronautics) which covers some of the general concepts, such as how optimum cruise speed is arrived at. That may help some with your second question. --Jayron32 13:01, 12 October 2016 (UTC)

The normal cruising height for a large jet is above 30,000 feet. At 5,000 feet the plane will have difficulty reaching its normal cruising speed. Wymspen (talk) 13:24, 12 October 2016 (UTC)

14 C.F.R. §91.117 (a) Aircraft Speed states: "Unless otherwise authorized by the Administrator, no person may operate an aircraft below 10,000 feet MSL at an indicated airspeed of more than 250 knots (288 m.p.h.)." (These rules apply in the United States, but generally, almost all other nations have similar or stricter requirements).

If you happened to be near San Francisco this week, you might have seen a United Airlines 747-400 operating low and slow - here's a video of Saturday's show. The aircraft maneuvered below 5000 feet MSL at speeds between 145 mph and 300 mph (with special approval from the FAA).

A large airliner like a 747 or 767 is not designed to operate efficiently at cruise configuration at 5000 feet MSL - but it is capable of flying in that configuration.

In normal cruise flight, a 767 is operating at or below V_NO. That means its flaps are up, its gear is up, and its multiple engines are configured for long-term, efficient flight; and it is not making any abrupt control surface deflections.

Nimur (talk) 15:53, 12 October 2016 (UTC)

Had the pilots of El Al Flight 1862 known what was going on, they would have had a shot at a survivable outcome by dumping more fuel and then attempting a landing at a speed of around 200 knots. Count Iblis (talk) 17:34, 12 October 2016 (UTC)

Sorry, but...  ? Do you make this claim because a reliable source - like the post-crash investigation report - indicated that the accident would have been survivable if the pilot(s) had done something differently? Because... if not, you probably shouldn't repeat that kind of a ludicrous claim on our encyclopedia, especially if you aren't an expert in the detailed analysis of 747 accidents.

After a major aviation accident that involves such great loss-of-life, experts study the event in great detail and publish their findings. If it is determined that different pilot-decision-making could have saved lives, that type of important detail gets published, and usually gets incorporated into training material. I do not believe any reputable accident-investigator believes that El Al Flight 1862 could have been made survivable if the pilots had made different decisions.

A detailed analysis of crew decision making is included in Chapter 2.5 of the Nederlands Aviation Safety Board AIRCRAFT ACCIDENT REPORT 92-11, available in English from archive.org. There is no mention whatsoever that Count Iblis' proposal - which does not even comply with the emergency-operations procedures for a 747 - could possibly have made the situation work out any better. Specifically quoting the accident report: "the possibility for a safe landing was highly improbable, if not virtually impossible" - even if the pilots had done something differently. That's the official, published opinion from a team of aviation experts - who specifically studied the accident - and know far more than you and I about 747 operations.

This is Wikipedia - the free encyclopedia that anyone can edit - but we have a standard for sourcing our claims. Just like you can't make up random numbers and facts about general science and post them in our articles, you should not post procedures, airspeeds, or analyses, if you don't know them and can't cite sources for them.

Nimur (talk) 18:09, 12 October 2016 (UTC)

See here: "The analysis indicates that the accident aircraft was recoverable from a technical point of view. However, the required procedures to perform such a recovery are not part of current industry training practices for complex in-flight emergencies or handling qualities in degraded modes. It is therefore understandable that a successful recovery of the aircraft was highly improbable." Count Iblis (talk) 19:10, 12 October 2016 (UTC)

Thank you for citing a source. At least we can now attribute the claim, irrespective of my personal opinions about that claim.

The author of the conference-paper you cited, M.H. Smaili, has his entire thesis available at this link, hosted by Netherlands Aerospace Centre: NLR-TP-2003-392 Flight data reconstruction and simulation of the 1992 Amsterdam Bijlmermeer airplane accident. It is worth consideration. I read most of the 40-some pages, and it is true that the author of that paper does recommend your idea, including a fuel jettison and a "high-speed landing or ditch at 200/210 KIAS", and also acknowledges that this recommendation is in contravention of the ordinary emergency operating procedure.

Even still, the source you cite is a student's thesis (abridged into a conference-paper presentation). Here's my two cents: pilots should not turn to students for advice on how to fly damaged aircraft. Even very smart people - who work out math very carefully, and perform elaborate simulation - are not necessarily qualified to provide advice or instruction on the safe operation of an aircraft in any condition. The author even admits that the procedure he recommends deviates from the procedure that industry-experts recommend. For example: here are a few bits of techno-babble that you might have lost in the details: "Weight reduction was achieved by simulation of fuel jettison up to a remaining quantity for about 20 minutes of flight." "Further speed reduction below approximately 220 KIAS at flaps 1 resulted in a loss of go-around capabilities." Are you - or the author - qualified to evaluate that statement to determine the impact of those consequences? Do you believe that you could make the judgement-call between one statistically-unsafe outcome, and another, different, statistically-unsafe outcome? (For example: do you know whether it is safe to jettison fuel on a Boeing 747 when the cockpit instruments are indicating an engine fire? Do you know whether there is enough precision to dump the correct amount of fuel when an aircraft is damaged in this way? What if you inflame the fire and blow up a wing? What if you jettison all your fuel and lose all propulsion? You just made your catastrophic emergency into an even worse catastrophic emergency!) This is exactly why pilots are highly trained to follow standard procedures, even during catastrophic emergencies.

In this case, I would defer to the accident report, which found that safe control of the aircraft was a virtual impossibility.

Here's a life-tip: Go Fly. During the pre-flight brief, ask your flight instructor to demonstrate an emergency-procedure during your first flight. It will change the way you think about aviation safety. Because, at some random time during the flight, probably while you are out sight-seeing and having a great time, the instructor will simulate an emergency and do something with a small airplane that will scare the lights out of you. Surprise! You're a mile from earth and don't have an engine! How will you react?

Demonstrating, and practicing, and preparing, for emergency operation is a very normal part of flying and flight training. Just a few weeks ago, I practiced something like five or ten emergency-landings. You can even listen to me having a pleasant conversation with our air traffic controller as I repeatedly kill the engine. This stuff has to be beaten into your head during practice flights so that you do it right when you're in a real actual emergency. Don't panic. Follow the checklist. Definitely don't try anything new.

Nimur (talk) 19:19, 13 October 2016 (UTC)

Caterpillars and butterflies

Here it says that butterflies are "able to remember the solution to a puzzle that they were taught how to solve when they were a caterpillar". How can you teach a caterpillar how to solve a puzzle? How can you even teach ANYTHING to an animal as inferior as a caterpillar? --Qnowledge (talk) 16:13, 12 October 2016 (UTC)

Insect nervous systems may be quite primitive, but that doesn't mean they don't have a capacity for learning. This source may be helpful. NorthBySouthBaranof (talk) 16:21, 12 October 2016 (UTC)

Note that the "puzzle" could be quite basic, like remembering that the red leaves are bitter and the green leaves are good. StuRat (talk) 16:39, 12 October 2016 (UTC)

"...that they were taught how to solve..." Who taught them? ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:07, 12 October 2016 (UTC)

Invertebrates are very capable of learning quite advanced tasks. I suggest the OP should read Pain in invertebrates#Learned avoidance and Pain in invertebrates#Cognitive abilities. DrChrissy ^(talk) 17:28, 12 October 2016 (UTC)

These scientists. When volunteering to help at a reference desk, it's a good idea to look for references before posting. It can be hard, so I'll tell you how I did it. I remember reading the work, but forgot who published it and where. So I went to google and typed /caterpillar learn butterfly/ [2]. The top hit is this Wired article [3], and a quick skim of that gave me an author name, Weiss. Now it's just another click over to google scholar, where I typed /weiss caterpillar learn/ [4], where the mentioned PLoS ONE article is the second hit. That's how you can help provide references on the reference desk. It took me longer to type this up (~3 minutes) than it did to find the answer for OP (<1 minute), but I hope that helps. SemanticMantis (talk) 17:42, 12 October 2016 (UTC)

The famous recent work on butterflies Lepidopterans remembering what was learnt as a caterpillar is Blackiston et al. (2008) "Retention of Memory through Metamorphosis: Can a Moth Remember What It Learned As a Caterpillar?" [5] It explains in the abstract:

“ Fifth instar Manduca sexta caterpillars received an electrical shock associatively paired with a specific odor in order to create a conditioned odor aversion, and were assayed for learning in a Y choice apparatus as larvae and again as adult moths. ”

The paper is freely accessible, and include diagrams of the puzzle/challenge setup. SemanticMantis (talk) 17:37, 12 October 2016 (UTC)

Other examples of memory and learning surviving metamorphosis include -[6][7][8] DrChrissy ^(talk) 22:43, 12 October 2016 (UTC)

As described, this does not necessarily have to mean the nervous system carries the memory. Most notably, aversive associations have been reported to be passed on in mice through two generations. [9] I would take a guess that this involves the epigenetic alteration of specific genes closely associated with the odor reception itself, though I don't know that - what I do know is that spermatozoa don't have brains. :) Wnt (talk) 15:45, 13 October 2016 (UTC)

Yeah, the second generation mouse "memories" together with the trans-pupation "memories" form a captivating picture. You're right that sperm don't have brains, but structural content for the moths could conceivably be preserved in the Imaginal discs. SemanticMantis (talk) 16:28, 13 October 2016 (UTC)

I have traced the mouse study back to its original source here[10]. Rather oddly, hidden away in the text is a statement that pups born by artificially insemination were not behaviourally tested. This, to my mind, makes their statements dismissing observational learning as weaker than might be perceived. DrChrissy ^(talk) 17:01, 13 October 2016 (UTC)

User:DrChrissy Interesting, thanks. Are you suggesting that parents could some how teach pups odor aversion even when not they are exposed to the odor simultaneously? I don't think the mothers were challenged with the odor while pregnant, so that rules out in utero "observation," right? Maybe I should just dig into the design/protocol myself but I'm curious what you're getting at. SemanticMantis (talk) 19:01, 13 October 2016 (UTC)

Ah - I have just seen that in the cross-fostering study, the pups were fostered On Day 1 postnatally. This means there would have been very, very limited opportunity for observational learning. And you are correct the females were not (deliberately) exposed to the odour while pregnant. DrChrissy ^(talk) 19:30, 13 October 2016 (UTC)

Human travel to Mars

How are we going to shield the astronaults brains from radiation?--86.187.174.75 (talk) 17:34, 12 October 2016 (UTC)

Read this. --Jayron32 17:36, 12 October 2016 (UTC)

Some good stuff at radiation protection and radiation hardening (though that second one is geared more towards protecting equipment). We don't seem to have a specific article devoted to the subject of protecting astronauts from radiation, but it shows up in a number of other areas. Matt Deres (talk) 17:46, 12 October 2016 (UTC)

You'll want to shield more than just the brain. Actually, the brain is more radiation-resistant than some other parts of the body, because (especially in adults) it doesn't contain a lot of actively-dividing cells. Human spaceflight and Effect of spaceflight on the human body may be of interest. --47.138.165.200 (talk) 20:13, 12 October 2016 (UTC)

Whilst you make the certainly important point that the brain is largely post-mitotic, there is still a lot of damage that can be done in the absence of cell division, see our excellent article central nervous system effects from radiation exposure during spaceflight. Fgf10 (talk) 07:00, 13 October 2016 (UTC)

I'd say start here: [11]. It is possible to take a portion of the radioresistance of tardigrades and put it into human cells, allowing for the possibility of gene therapy or other penetrating treatments getting Dsup to where it could protect the DNA directly. Wnt (talk) 15:48, 13 October 2016 (UTC)

Purported car that runs on sea water

I came across this recently which appears to boast that their car can run on ordinary sea water. It sounds bogus but I wanted to confirm with the experts here. This is bs right? ScienceApe (talk) 18:53, 12 October 2016 (UTC)

Yep, total bs, more precisely some mix of pseudoscience, hoax, and fraud. We have a pretty good article on water-fueled cars that explains the problems and some history, Snopes is also always a good place to check for this kind of thing. They don't seem to have a full article but their discussion thread on the topic is here [12]. SemanticMantis (talk) 18:58, 12 October 2016 (UTC)

(Sorry, I flubbed this one by skimming the source link too quickly and jumping to conclusions. Best to ignore my whole post.) SemanticMantis (talk) 03:16, 13 October 2016 (UTC)

It not purported to run on seawater, that is merely what the journalist described it as. No, in fact the nanoFlowcell is described by its inventor as running on "bi-ion liquids" which he claims was conceived by NASA decades ago (though I can find no evidence of this). If you read his description, it sounds like a relatively ordinary battery, and the water is simply the solvent for the electrolytes. If you buy his description of how it is supposed to work, the advantage of this over an electric car is that instead of recharging the battery, you simply refill the emptied electrolyte tanks. If it worked, that would certainly be a lot faster than recharging. The one part of the description that sounds extremely fishy is the inventor's claim that one side contains a positive charge, and the other contains a negative charge. Two tanks of water separated by a membrane doesn't seem like an especially good capacitor, so that doesn't seem like a winning design for a car battery. We can give him the benefit of the doubt and assume he's talking about the general way that batteries work, with chemical reactions continuously generating positive charges on one side and negative charges on the other. This description is too vague to violate the laws of physics, but it has other hallmarks of a scam. The biggest red flag is that he is going public with this project while at the same time being extremely secretive about how it works - giving general descriptions but no specifics. In my experience reading about scams, any time someone presents what is basically a magic box that does something revolutionary, but won't let you look inside, it's a scam. And believe me, this car is pretty magical. Battery design is a very hot field, and making a battery light enough to power a car any significant distance is quite a feat. The batteries currently used in electric cars run on some fairly exotic electrolytes in organic solvents or fancy solid substrates, and are the result of decades of research and development. For someone to claim he did it with something he could dissolve in ordinary water is hard to believe. The typical evolution of all of these water-fueled-car scams is to go public with a revolutionary invention, be incredibly vague about how it works so no one can point to a violation of the laws of physics, collect millions of dollars in investments, then disappear into the aether. Someguy1221 (talk) 20:37, 12 October 2016 (UTC)

I erroneously jumped to the conclusion this was the same old junk. In fact it seems to be merely conceptually similar junk, so thanks for clarifying :) SemanticMantis (talk) 21:24, 12 October 2016 (UTC)

Flow batteries are commercially available and in use worldwide. Vanadium pentoxide, from memory. Greglocock (talk) 22:12, 12 October 2016 (UTC)

We apparently haven an article on flow batteries, and apparently a number of laboratories are trying to develop ones suitable for cars. Someguy1221 (talk) 22:19, 12 October 2016 (UTC)

Any student who took college chemistry and is familiar with the Nernst equation will also hopefully remember the concept of the concentration cell, of which a flow battery is basically a highly engineered version of. --Jayron32 22:39, 12 October 2016 (UTC)

The "water dust" part sounds pretty fishy to me. I don't know what the secret ionic liquids are, but I bet whatever they are if you dump the residue from 150 liters of them on the road pretty often, the ecologists will have something to say about it. I mean, they don't even like road salt, and if this were as easy as road salt you'd think it would have been invented before. Wnt (talk) 15:53, 13 October 2016 (UTC)

It is also worth noting that if he were a real scientist, he'd use the damn right terms. I suppose he could be talking about some of the more exotic low-temperature ionic liquids, though most actual chemists I know tend to use the term to refer mostly to molten salts. Unless he means simply an aqueous solution of a salt. I'm pretty sure one of the indicators on the Crackpot index is someone who confuses basic terms from the very science he's purporting to be an expert in. --Jayron32 19:02, 13 October 2016 (UTC)

Lord, there is a year and a half old Wikipedia article on this dubious Liechtenstein company NanoFlowcell which is asking for investors on its linked to website. Car show flash, and not even close to being enough grit, and perhaps worthy of deletion. --Modocc (talk) 20:08, 13 October 2016 (UTC)

Acousto-magnetic tags

This is about acoustto-magnetic tags, particularly about the role of the second "magnetically semi-hard metallic strip". According to the wikipedia article its purpose is to offset the magnetic anisotropy within the first strip, which "makes the [first strip] respond much more strongly".

• How exactly does the external field make the response stronger and what does "stronger" mean here?

Somewhere else I read that the second strip provides a "bias" which causes the first strip to vibrate at the same frequency as the external pulse frequency (58 kHz) from the detector. Without the "bias" it would oscillate at twice this frequency.

• Is this correct?

bamse (talk) 20:49, 12 October 2016 (UTC)

There are two reasons for the magnetised strip.

• Firstly it's a "switch". By being either magnetised or not, the tag can be turned on or off. This isn't essential for all tags (some are mechanically detached, some are always active but passed around the detector by staff), but it's useful and is used here.
• Secondly, it increases the sensitivity of these tags - they may just not be viable devices without. The way it works is that (all?) magnetic devices demonstrate hysteresis: the relation between applied field strength $H$ and resultant magnetisation $M$ isn't linear or even a simple mapping. However if $H$ is increased (by the nearby strip) it shifts the material's behaviour away from the $H=0$ point (the least linear point) to a place where the behaviour between the two is more approximately linear, or at least where the available change in $H$ (i.e. how much the reader's field coils can apply) gives a larger and more easily detectable change in $M$. Andy Dingley (talk) 21:08, 12 October 2016 (UTC)

Thanks that argument with the hysteresis makes sense to me. However, unless I misunderstand magnetic anisotropy, this is not exactly what it says in the article, is it? Also what about the frequency argument, is it correct? bamse (talk) 22:29, 12 October 2016 (UTC)

The frequency argument is correct but Andy Dingley's hysteresis description (though relevant to magnetic recording) is not relevant to the acousto-magnetic tag.

The sentence "The magnetized strip makes the amorphous strip respond much more strongly to the detectors, because the DC magnetic field given off by the strip offsets the magnetic anisotropy within the amorphous metal." was posted by Oosacker[13] and may be challenged. I find no source for it and instead believe this explanation [14]:

"[The acousto-magnetic tag] requires bias magnet material in addition to active element material. The [magnetorestrictive] material will shrink no matter which direction the magnetic field is placed upon it. If the tag is driven with Frequency, F, it gets smaller as the magnetic field increases and larger as it's driven towards zero. This means that while it is being driven at F, the tag is trying to work at 2F, because at both positive and negative halves of the drive signal, the tag is getting smaller. To get the tag to work at F, a bias field is required. The bias is provided by a semi-hard magnetic element in the label. When magnetized, the bias prevents the active element from ever being in a zero field condition. So for an entire half of the drive signal, the tag shrinks. Then it expands for the other half. This results in an F response.

When you walk through the gate with a tag, the transmitter in the gate energizes the material and causes it to resonate at F. The transmitter then stops. The tag will continue to "ring" at F for a short period of time, and the receiver listens for that frequency. If it hears it, it knows there is a tag and sounds the alarm.

When the AM tag is demagnetized, it is deactivated. When it's magnetized, it is activated. (This is the opposite of how the deactivation of EM tags works.)"

The above explanation makes sense and could be rewritten for use in the article. @Oosaker: last posted to the article discussion page in 2008[15] and was aware of the howstuffworks reference. AllBestFaith (talk) 15:58, 13 October 2016 (UTC)

What's the smallest nm node that's inevitable in consumer electronics (as far as we know)?

I guess I could wake up in a holodeck on a Discworld in a universe where matter's infinitely divisible at any time so nothing's inevitable but assume that unlikely shocks to civilization like that or a comet ending humanity or something don't happen. 7nm is still not inevitable yet, right? Is 10nm inevitable? When it gets to the point where manufacturers realize a full node is too hard will they start releasing ever smaller percentage shrinks just so the time between nodes doesn't accelerate astronomically or to try to take the asymptotically decelerating record from company X for awhile? Sagittarian Milky Way (talk) 23:40, 12 October 2016 (UTC)

We actually have articles on these. The 10 nanometer chip appears to be commercially inevitable. The 7 nanometer chip is more iffy, but major corporations are planning to produce them in bulk in the future. 5 nanometer chips and under are still highly experimental and it doesn't look to me like these will be inevitable until some completely new chip technology has matured, after which we'll have to reassess what's possible. Someguy1221 (talk) 23:59, 12 October 2016 (UTC)

http://www.theregister.co.uk/2016/10/10/boffins_eschew_silicon_to_build_tiniestever_transistor_just_1nm_long/ 196.213.35.146 (talk) 07:47, 13 October 2016 (UTC)

People may have to use molybdenum disulfide or molybdenum ditelluride or another of the Transition metal dichalcogenide monolayers and graphene to get smaller, but these are still at an experimental stage, and not a technology yet. Graeme Bartlett (talk) 11:08, 13 October 2016 (UTC)

October 13

Do T3 and T4 hormones play role in regulation of the body temperature?

I know that they play role in stimulation of the metabolism rate, growth and development and brain maturation during fetal development. but my question is on the regulation of the body temperature. (I can understand that the metabolism rate relates in such way or another to the temperature) 93.126.88.30 (talk) 00:26, 13 October 2016 (UTC)

I had high hopes for the article Thermoregulation in humans, but it doesn't seem to go into that kind of detail. I didn't watch this video here: [16]. But the title has some potential to be useful. --Jayron32 02:00, 13 October 2016 (UTC)

Unfortunately there's no information there. but thank you for your motivation to help. 93.126.88.30 (talk) 17:44, 13 October 2016 (UTC)

Are follicles the structural units for all types of glands or just thyroid gland?

I am reading about the thyroid gland now and the book states: "Thyroid tissue is composed of follicles, which are structural units of the gland". It's not clear if it refers to any gland or to the thyroid only. According to what I read here (follicular cell) it seems to be in thyroid glands only, but I'm not sure about it. 93.126.88.30 (talk) 01:17, 13 October 2016 (UTC)

Have a look at Endocrine gland, all of them are linked and have a "structure" section. While I admit it's a little ambiguous, I think using "the gland" in the sentence indicates reference to the object, in this case "Thyroid", not "glands" in general. If instead follicular tissue was the substance all glands are made out of, the sentence would make a lot less sense. Vespine (talk) 01:26, 13 October 2016 (UTC)

Just analyzing the sentence, "units of the gland" means a specific gland, to me, while "units of a gland" or better yet "any gland", would have the more general meaning. StuRat (talk) 14:19, 13 October 2016 (UTC)

Google's dictionary says a follicle is "a small secretory cavity, sac, or gland, in particular." NOAD's definition is identical. Arnold's Glossary of anatomy [17] has a similarly broad definition, as does Wiktionary [18]. Our own article Follicle_(anatomy) gives the broad sense too. Ovary has follicles. Peyer's_patch is described as a follicle. Lymphatic_system says there are lymphoid follicles in tonsils.

These links show that the term 'follicle' has a general anatomical usage, and it is clear that glands other than thyroid have sub structures called follicles. I would not assert, based on this evidence, that all glands have substructures described as follicles. SemanticMantis (talk) 15:46, 13 October 2016 (UTC)

Anatomical usage is basically descriptive Latin. wikt:follicle from wikt:folliculus, a small wikt:follis. In common Late Latin, a follicle is a little sac, like the scrotum; in anatomy, the term has since been applied at the end of a microscope. Wnt (talk) 15:59, 13 October 2016 (UTC)

Just looked at this again and tried some random searches. "Mammary follicle", "Harderian follicle", "parotid follicle" basically strike out. "Pituitary follicle" and "prostatic follicle" hit on stuff. "Sebaceous follicle" is the gland. "Salivary follicle" hits really old literature, comparative anatomy. I'm not sure though how much difference is biological and how much is cultural, basically random chance of who uses what term (also Harderian is pretty obscure, but "lacrimal follicle" picks up only junk hits also). It would take a long time to think this one through properly. Wnt (talk) 22:28, 13 October 2016 (UTC)

That is consistent with some of my research as well. Another tack is to search each article in List of glands of the human_body to see which use the term. I noted a few that did, many that did not. It's hard to rule out linguistic/cultural trends in science. I don't think we have any actual physiologists or anatomists in the house, but I'd be happy to be proven wrong on that. SemanticMantis (talk) 14:28, 14 October 2016 (UTC)

Mortality during pregnancy

What happens when a pregnant woman dies during the middle of her pregnancy? What happens when a married man dies during the middle of his wife's pregnancy? GeoffreyT2000 (talk, contribs) 16:48, 13 October 2016 (UTC)

"What happens?" is very broad. Can you specify what aspects you are interested in? Life insurance may come into play in either scenario. Maternal death is our article about women who die during pregnancy. SemanticMantis (talk) 17:10, 13 October 2016 (UTC)

See en ventre sa mere for the legal implications in common-law jurisdictions of the second case. Tevildo (talk) 18:11, 13 October 2016 (UTC)

There is also Posthumous birth although it includes cases where the father isn't married to the mother, sometimes not even alive during conception. And in rare cases of the first, there is Coffin birth. Nil Einne (talk) 07:02, 14 October 2016 (UTC)

October 14

How long would electrons take to stop accelerating if homes used DC?

Drift velocity not field propagation velocity. Is this why AC has less resistive losses? (the electrons not getting that "fast" in 1/200th 1/100th or 1/240th 1/120th of a second) Sagittarian Milky Way (talk) 00:54, 14 October 2016 (UTC)

No, the average time between collisions is orders of magnitude shorter than the switching time of AC current. Dragons flight (talk) 01:27, 14 October 2016 (UTC)

So since the voltage hardly changes in the short time between the first and second collision after the current's on does that mean both collisions are about same speed, at least for the average electron? (luck at dodging atom centers and quantum mechanics and all that) Sagittarian Milky Way (talk) 02:09, 14 October 2016 (UTC)

As I understand it, the advantage of AC for long-distance transmission is that you can use a higher voltage; therefore you don't need as high a current to transmit the same power. (Power = voltage times current, but resistive power loss = resistance times the square of current).

So you may ask, why can you use a higher voltage? Well, theoretically, you could use just as high a voltage for DC transmission, but then what are you going to do when you want to power a house? Stepping down DC voltage is complicated and costly. For AC it's easy; you just use a transformer. --Trovatore (talk) 01:34, 14 October 2016 (UTC)

Ah, I did not know your penultimate sentence. I always guessed AC was to keep drift velocities down and they didn't exceed 60Hz to avoid needing gears for the generator. Sagittarian Milky Way (talk) 02:27, 14 October 2016 (UTC)

Also some further info can be found in HVDC converter. Vespine (talk) 04:11, 14 October 2016 (UTC)

See also War of Currents for the history of AC vs DC mains electricity. Tevildo (talk) 07:10, 14 October 2016 (UTC)

• Is this why AC has less resistive losses? No. Shameless self-promotion of a section I wrote: Electric_power_transmission#Advantage_of_high-voltage_power_transmission

If you are interested in those questions, you might also want to give a look at the skin effect, which is the reason why power cables everywhere have the same diameter (well, High-voltage cables are larger, but the extra section is not made of copper). Tigraan^{Click here to contact me} 07:40, 14 October 2016 (UTC)

The Drift velocity of electrons in wires is typically 1570 km/s (related to the Fermi energy concept in quantum mechanics). Please compare the values in bold as they relate to the OP's question. As derived in detail in the linked article[19]:

- 1A DC flowing in a small copper wire changes the electron velocity by 0.000 023 m/s. It's probable that the majority of electrons in a switch when it left the factory never move out of it throughout the life of the switch.

- Going from DC to AC means the change direction reverses 120 (US) or 100 (Europe) a second. Here the original electrons certainly never leave the switch or indeed any metallic conductors.

This may make it clear that electrons never "stop accelerating" and our use of them for electric power distribution has almost negligible effect on their individual paths.

Virtually all electronic equipment in the home, including the computer or phone you are using, uses DC supplies. Homes could be (have been) supplied by DC mains but AC distribution is universally preferred because of its advantages of low-cost voltage conversion by transformers, the possibility to balance generators and loads in a network by phase control, and other minor advantages in avoiding corrosion at connections between dissimilar metals, arc quenching and avoiding permanent magnetization.

The saving in cable weight by using a high voltage (low current) for long-distance distribution applies to both DC and AC. However AC conductors need more insulation to handle 41% higher peak voltage than DC for the same power level. The choice of AC frequency is a compromise between contradictory requirements.

Lower frequency	Higher frequency
More reliable rotating generators and converters	Smaller transformers for a given power  :-)
Negligible skin effect	Skin effect reduces effective cross section of conductors
Negligible power factor loss	Power factor effects require correction and over-dimensioning of generators and network components to handle extra reactive current
Negligible impact of cable capacitance	Cable capacitance hinders long-distance power transmission
Tolerable audio hum from transformers or interference from mains wiring to audio equipment	Increasingly noticeable noise from transformers (see Magnetostriction) and potential for man-made EMI

The main results of standardization are:

• Home distribution in Europe and Asia: 50 Hz
• Home distribution in USA: 60Hz
• Aircraft on-board power distribution: 400 Hz (for low weight)
• New long-distance high-power lines: DC (as new HVDC conversion equipment becomes economical). AllBestFaith (talk) 17:42, 14 October 2016 (UTC)

Magnetostriction, incidentally. Worth a redirect as a likely misspelling? Tevildo (talk) 18:28, 14 October 2016 (UTC)

Thank you for the correction. AllBestFaith (talk) 19:36, 14 October 2016 (UTC)

@AllBestFaith: Oh crap, nevermind. I should have read what you wrote... Wnt (talk) 20:44, 14 October 2016 (UTC)

• I think the common misconception as "electricity is the flow of electrons" is what is at heart of the misunderstandings here. Such misunderstandings come from MANY common misunderstanding of electrons as little, discretely identifiable little hard balls of negative change, bouncing around like ping pong balls. I'm not sure that level of misunderstanding is capable of being rectified in this scope of this discussion, so let's ignore it, and use the "little balls" model (wrong as it is) to show that even if we were to assume it correct, electricity is still not the movement of electrons. Electricity is the flow of energy through an electric field. Not a single one of the electrons actually has to carry the energy individually from one place to another. Even if we think of electrons (quite wrongly, but lets keep it for now) as little rigid balls; those little rigid balls don't travel down a wire as though they were marbles being rolled down a tube. Direct current is NOT all of the balls rolling down the tube in one direction, and alternating current is NOT all the little balls shaking back and forth, though some simplified models try to show it that way. Instead we should think about electrical energy being passed through a medium in the same manner that energy gets passed though the stationary ball in the roquet move in the game of croquet. See this video if you're unfamiliar. Notice how the red ball doesn't go anywhere and yet is able to transmit a bunch of energy to the blue ball. Electricity is like that: the electrons don't go anywhere in either AC or DC. They just "pass the energy" down the chain. Of course, that's still a very wrong way to think of electrons and electricity, but it's right enough to get us to reach the correct conclusion that electrons don't move. --Jayron32 18:49, 14 October 2016 (UTC)

  I think you're overstating this a bit, Jayron. Direct current in particular does involve flow of charge, and you can't have flow of charge without movement of charge carriers. If you take a line carrying one ampere, and pick an arbitrary point, one second later, there will be approximately six quintillion electrons to the right of that point, that were to the left of the point when you started. (That's a net figure; there could be electrons to the left of the point that were to the right when you started, but they count negatively.) --Trovatore (talk) 22:26, 14 October 2016 (UTC)

  Yes, you're probably right there; but the issue is that when we consider electrons as isolatable, individual particles with a clear identity, it introduces all sorts of problems with how physics works. Your statement also isn't strictly correct; it would imply a "hole" with six quintillion less electrons to the left of that point. Instead, what we know is that the electrons to the left of that point have lower potential energy than the ones to the right of that point. The problem is, you can't say that any specific 6 quintillion electrons actually moved; like if you painted them red and followed them with a little microscope. Electrons are not individually identifiable. To say that some arbitrary number of electrons moved implies you could say which ones moved and which ones didn't. It's not even a limit of our measuring capabilities, like we know that they are moving, but we just can't build a device capable of tracking them. We literally couldn't track them because the physics says we can't, per Heisenberg and all that jazz. Certain aspects of electron behavior imply movement and motion and mobility, so we have concepts like electron spin and electron mobility; the mathematical predictions of such concepts bears out fine, but considering electrons as discrete balls that can spin and travel around freely creates problems as well; if electrons were discrete balls, then we wouldn't have the contradictions of the double slit experiment and the like. --Jayron32 00:09, 15 October 2016 (UTC)

  Well, so we need to keep two aspects of the question separate, those being the classical picture, and the quantum weirdness.
  For the classical picture, the point about the "hole" is addressed by the fact that what we really have is a circuit. It's like a big hula hoop with sand inside, the sand being the electrons. For AC, the sand is sloshing back and forth, and energy is transmitted via the sloshing. For DC, the sand is moving in a consistent direction around the hoop, and that is how it transmits energy. Complications being that the energy is not transmitted via the kinetic energy of the particles, but rather via their interaction with the EM field; and that the particles are individually moving much faster than their collective drift.
  Now when you get to quantum weirdness, what you can do is think of each of the possible classical descriptions as being a single Feynman diagram, and then you take the path integral over all of them. --Trovatore (talk) 00:22, 15 October 2016 (UTC)

  Yes, but the problem is that "classical picture" doesn't represent what happens, because the classical picture makes too many inaccurate predictions about the behavior of electrons. Electrons as grains of sand we could track if we wanted to, but just can't be bothered to is still not the same thing as saying that electrons are not actually discretely identifiable particles. If one is taking a VERY long birds-eye view of electricity, the classical description works fine as a lie-to-children for broad behavior like Ohm's law. Once we start getting down to the small picture, however, and looking at what is going on with those electrons, the classical model is woefully inadequate. --Jayron32 00:48, 15 October 2016 (UTC)

  It's inadequate, but not on the question of whether electrons transmit energy by moving. They do transmit energy by moving. --Trovatore (talk) 01:03, 15 October 2016 (UTC)

  Which electrons moved? That's the problem. Saying "the electrons move" leads to the question "which ones moved and which ones stayed put?" Which is why we need the reminder that we can't identify individual electrons as such, and then say electrons move. We can say both "charge moves down the wire" and we can say "electrons carry the negative charge". The problem comes from the chain of thinking that says "this electron here moves over there..." as though that were a question that were even answerable. I agree with you that I was way too overzealous in speaking in absolutely, but the problem is that we really need to unask the question. QM causes such confusing leaps of logic, because our brains operate in a classical world. The same problem exists with considering electron spin. Electrons clearly behave as though they have spin; and yet if electrons are true point particles, then we have the geometric paradox that a point can't spin. Being able to work in quantum mechanics requires one to carry physical contradictions happily in one's brain. I guess I would have done best here to listen to David Mermin. "Shut up and calculate". --Jayron32 01:36, 15 October 2016 (UTC)

Going back to the question "how long", this is determined by the inductance of the conductors. The current will not stop instantaneously, instead it will have some tendency to keep flowing into whatever load is on the wires. Our article will be hard to understand, but what you would have with a powerline, is a pair of parallel wires. You can expect that the current will stop on the order of several nanoseconds. If your try to stop it too fast, a high voltage will appear across what ever you try to stop it with, so for example flicking a switch or pulling out a plug may make a spark. Graeme Bartlett (talk) 22:53, 14 October 2016 (UTC)

This is correct and is a consequence of the fact that utility power transmission lines are not impedance matched transmission lines. An ideal matched line has uniformly distributed inductance and capacitance that together give it a characteristic impedance. It can successfully deliver a wideband waveform such as an abrupt on/off pulse to a load that has the same impedance. Near-ideal matched lines and loads are used throughout electronic circuits that handle high frequencies. The exactness of their match can be measured by TDR technique and expressed in SWR values at frequncies of interest. Matched power feeding is essential for, say, a radio Transmitter antenna but would be very impractical for utility power distribution. AllBestFaith (talk) 12:57, 15 October 2016 (UTC)

The science behind how "Metanium" cream works

Please could you explain to me how the ingredients in "Metanium" cream actually treat nappy rash. According to this website the cream contains;

Titanium dioxide 20.0% w/w
Titanium peroxide 5.0% w/w
Titanium salicylate 3.0% w/w
Dimethicone 350
Light liquid paraffin
Tincture of benzoin
White soft paraffin

I am only interested in the scientific understanding of how the ingredients in this cream treat nappy rash. I believe this question is acceptable on the Reference Desk and does not contravene the medical advice prohibition because I am not asking for any diagnosis or treatment plan. To make absolutely clear, I do not have nappy rash and I am not asking this question in relation to any specific case of nappy rash that has ever existed. This is purely a scientific question.

ありがとう — Preceding unsigned comment added by 2A01:430:D:0:2CC:B0FF:FE9B:CC73 (talk) 12:57, 14 October 2016 (UTC)

Irritant diaper dermatitis#Treatments has some information. DMacks (talk) 13:08, 14 October 2016 (UTC)

"A review of the pathophysiology, prevention and treatment of irritant diaper dermatitis" [20] - seems to be a very comprehensive and relatively recent review, including titanium dioxide ointment treatments like the one you mentioned, mechanisms, and many further refs. It is unfortunately paywalled, I can provide a copy to interested readers upon request. Here [21] is a less comprehensive but freely accessible overview of topical agents in neonates. SemanticMantis (talk) 14:20, 14 October 2016 (UTC)

We currently redirect titanium peroxide to titanium oxide, but this seems invalid, as it apparently contains a true peroxide group. Actually, the combination of this peroxide + the organic chemicals in this mixture leaves me a little bit surprised it doesn't go boom... Wnt (talk) 15:57, 14 October 2016 (UTC)

10% benzoyl peroxide hasn't blown me up yet. The article says it can be explosive in pure form, but apparently diluting and mixing it with a base makes it safe, or else it presumably wouldn't be sold in every drugstore. I can definitely vouch for its bleaching effect though! Even a little bit of residue is great at bleaching all your towels. --47.138.165.200 (talk) 09:52, 15 October 2016 (UTC)

What's larger, follicle cell or parafollicle cell?

it's not clear to me if the follicle itself is cell or something which composed of many epithelial cells 93.126.88.30 (talk) 19:27, 14 October 2016 (UTC)

A follicle can be a single cell, a group of cells, or even a subpart of a cell. A follicle just means "little pocket", and the term can refer to any number of structures, its basically a description of a shape, not of a specific type of structure or functional part. --Jayron32 19:58, 14 October 2016 (UTC)

October 15

Would the world be in a worse state if we still relied on horse and cart?

Economically, environmentally etcetera? JoshMuirWikipedia (talk) 02:39, 15 October 2016 (UTC)

The use of cars is not allowed by any Old and New Order Amish who consider the rules of their church, particularly regarding rural life, manual labor and humility, to be consonant with a better world obedient to God's will. AllBestFaith (talk) 15:13, 15 October 2016 (UTC)

Sort of a general theme of economics is that making it cheaper for people to do something they already want to do allows them to spend more money on other things. This spurs demand, which spurs hiring, which increases the money available to buy things, which... so on and so forth. It's hard to say precisely how much economic damage would be caused by such a drastic change, but you could imagine a massive collapse of various businesses (caused by the vastly increased cost of travel) would cost jobs, incomes, tax revenues, charitable contributions, and government expenditures on lots of worthwhile things. So, potentially huge. As for environmental issues, horses are pretty awful for the environment, despite being "all natural" (well, so is oil). See for instance the great horse manure crisis of 1894. Someguy1221 (talk) 02:54, 15 October 2016 (UTC)

(edit conflict) Read this and this and this for some background on the environmental question. We of course cannot answer questions of opinion such as "better" or "worse". But those articles should help you become more informed so as to reach your own conclusions. Also consider that the transportation of people and goods by horses is of a smaller scale than other transportation methods, such as rail, air, and road vehicles. This article covers the amount of goods moved through one country (the United States) by road transport. One can drive across the U.S. in 3-4 days by automobile. According to this a horse can travel only about 100 miles in 24 hours under optimal conditions; it would take well over a month to cross the U.S. like that. Also according to This a horse can at best carry 300-400 pounds for at most 8 hours per day. You can extrapolate from these calculations what it would take to move goods around the U.S. solely by horse. Again, "worse" is for you to decide without us telling you. But I've probably given you enough references to make your own comparisons regarding economic differences between using horses vs. trucks for transporting goods; this also ignores rail and air contributions as well.--Jayron32 02:56, 15 October 2016 (UTC)

(edit conflict)I take that to mean you're excluding steam engines. Checking Google maps, it's roughly 1400 miles (2250 km) from Florida to Wisconsin. A horse and buggy gets maybe 6 miles/9.5 km per hour. A single horse with a rider might be able to travel 60-100 km (or 37-62 miles) during a maybe 12 hour period. Horses have to eat, sleep, and even get additional rest even when not sleeping; cars and trucks just need to refuel. It's not unreasonable to assume that a horse pulling a cart with cargo might only be able to safely travel six hours. Even if you had stations for switching off horses and drivers every six hours (and had the swap down to a science), it'd still take about five days to ship oranges from Florida to Wisconsin. That would be too expensive for (at most) a couple dozen crates of oranges though. So, most non-canned, non-pickled foods would have to be grown locally, which would increase malnutrition (if not outright starvation).

The Mississippi river flows about 1.2 miles per hour, and north to south, so it wouldn't help with oranges. Indeed, it would be useless for anything that can't wait a couple of months (assuming you're sailing and rowing as much as possible). An enterprising Wisconsin cheese manufacturer might use the ride to age his wax-sealed cheese, cutting down on production time. Otherwise, the river is useless without steam engines.

And it's about 1850 km (or about 1150 miles) from Valencia to London, which includes at least 33.3 km (20.7 mi) of sailing. It took about a week to sail from Tunis to Genoa, which (per Google maps) is just under 900 km (roughly 550 miles). So, premodern sailors could get about 125 km/75 miles per day on a good day. If the crew rotates shifts and the weather is good, they should be able to pull 5 km/3 miles per hour, making the English Channel a six or seven hour crossing at best (two days at worst). Again, assuming you have stations to switch horses and drivers every six hours, have the sailing crew rotate, and everything's down to a science, it's still just over a week to get a crate of oranges from Valencia to England.

Since uncut oranges can last just over a fortnight, the 1975 series Survivors might have been exaggerating when one of the characters surmised that none of their children would ever taste an orange; but it would certainly be an exotic, decadent, foreign luxury.

And those are the best case scenarios. Realistically, the land travel would probably take two to four times as long. Ian.thomson (talk) 03:55, 15 October 2016 (UTC)

No need for malnutrition. If you can't get your vitamin C from oranges, just eat apples instead. Vitamin pills might be a good idea, too. StuRat (talk) 17:20, 15 October 2016 (UTC)

We know how to travel upriver without steam power. It is slower than downstream but not impossible. Just ask any voyageur. Rmhermen (talk) 04:04, 15 October 2016 (UTC)

I knew about rowing, but figured that it'd be unfeasible over the couple thousand miles involved except for very light travelers (like Huck and Jim). The voyageur article's description of the dangers would (under modern legal conditions) render land travel preferable to that. That said, there were indeed trading posts up the Mississippi, though I expect they'd still have to restrict the goods to something more portable than crates of oranges. Though there does appear to have been plans for (if not actual use of) animal-driven paddle boats after all, so maybe not. No idea what the speed would be. Ian.thomson (talk) 05:20, 15 October 2016 (UTC)

If there were real canals, then animals could pull heavy boats. This used to happen in the Netherlands. Rivers would be too shallow on the edge and not have a track on the side for the horse/ox. One person would be needed to steer the boat, and another to make the animal pull. Graeme Bartlett (talk) 11:36, 15 October 2016 (UTC)

You might find this account of the 1894 great horse manure crisis in London of some interest - http://www.historic-uk.com/HistoryUK/HistoryofBritain/Great-Horse-Manure-Crisis-of-1894/ Wymspen (talk) 11:39, 15 October 2016 (UTC)

Bubbles on puddles

Why is it that when bubbles form on the surface of puddles during rain, this is considered a sign that the rain will continue? My personal hypothesis is that this indicates that dissolved air is coming out of the water, which is a sign that barometric pressure is still falling (and therefore that the low-pressure system bringing the rain is still on the way in) -- am I on to something here? 2601:646:8E01:7E0B:ADC2:429C:883B:48A1 (talk) 10:11, 15 October 2016 (UTC)

What is the basis of your first sentence? ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:38, 15 October 2016 (UTC)

Yes, without commenting on the factuality either way, I can't say I've ever heard the expression. During a rainfall you're unlikely to see many bubbles just because the water in the puddles would be in constant motion. Or are you talking about during gaps in the rainfall? There are a number of factors that would influence the presence of bubbles, including pockets of air in the soil itself. Matt Deres (talk) 13:04, 15 October 2016 (UTC)

I think surface tension traps air under a canopy of water until the bubble bursts due to its own inherent instability. I think the formation of the bubble results from the impact of the raindrop on the surface of the puddle, displacing some water and momentarily trapping some air. Bus stop (talk) 15:32, 15 October 2016 (UTC)

Searching for bubbles puddles rain I find half a dozen totally non-reliable sources saying this is a genuine old wives' tale, right up there with the thing about red sky in the morning. As such, well, it has a fair chance of being true. Wnt (talk) 18:08, 15 October 2016 (UTC)

Feynman Lectures. Lecture 31. Sec. 31–2 The field due to the material [22]

I have understood everything except one phrase: "the driven motion of the electrons produced an extra wave which travels to the right (that is what the factor e^iω(t−z/c) says)"

I don't understand why does factor e^iω(t−z/c) say the wave travels to the right. Why not to the left (as we know that waves are source-symmetrical)? In the case of Sec. 31-2 the position z=0 is the glass plate (not the source S). So to use the shifts of the graphs E(t) and E(r) as proof we should assume where source is situated and in what direction the wave goes. But direction is what we have to prove. Besides it is written in Table 31–1 that z is perpendicular distance from the plate (so positive no matter in what point field is measured: to the left or to the right of the plate).

I understand that if the graph of E(t) is like this, then the graph of E(z) is like this in accordance with Fig. 29–2 and Fig. 29–3 and in accordance with rules of graph transformation (like with y=f(x) and y=f(-x)).

Can somebody explain how does factor e^iω(t−z/c) (or Cos[ω(t−z/c)]) prove that direction of wave is rightward? I feel the answer must be simple, but I reached a deadlock. Username160611000000 (talk) 11:51, 15 October 2016 (UTC)

• If the wave from accelerated electrons of the plate would be moving to the left then the factor would become e^iω(t+z/c). Is it correct? Username160611000000 (talk) 15:59, 15 October 2016 (UTC)

Magnesium sulphate and mineral water

Our article on Magnesium sulphate says "It is naturally present in some mineral waters" with a citation needed tag. Is it possible to state this? I know that magnesium ions and sulphate ions could be present in some mineral waters (those in the town of Bath, for example) - but it seems to me that, unless those are the only salt ions present, then the compound itself can't be said to be present. Is this correct?--Phil Holmes (talk) 12:05, 15 October 2016 (UTC)

IUPAC changed the spelling of sulphur/sulphate to sulfur/sulfate in 1980.
Sleigh (talk) 12:13, 15 October 2016 (UTC)

IUPAC has no authority whatsoever over the English language. (Given that they prefer the atrocious "aluminium", it's a good thing they don't.) --Trovatore (talk) 21:57, 15 October 2016 (UTC)

My English dictionary still says sulphur, so that's good enough for me. But can you answer my question?--Phil Holmes (talk) 12:41, 15 October 2016 (UTC)

@Sleigh: it was actually 1990[23]. DMacks (talk) 21:27, 15 October 2016 (UTC)

There are certainly quite a few Br⁻ anions in the sea, but we don't have much of a problem saying that there is common salt (NaCl) in it, right? Same principle. Double sharp (talk) 12:51, 15 October 2016 (UTC)

By extension, if the water has unusually high levels of both magnesium and sulfate but not of other ions, one could say "it has high levels of magnesium sulfate" because there's not any other obvious way it could have only these two being high. And likewise if there are lots of ions but those two are present in a 1:1 ratio and no other ion levels provide the correct ratio for this substance one could deconvolute the components. But you're right, that if you toss certain amounts of MgSO₄ into certain amounts of ocean water, you can't tell after the fact whether you added MgSO₄ to water containing NaCl vs adding MgCl₂ into water containing Na₂SO₄. DMacks (talk) 21:21, 15 October 2016 (UTC)

Mission to Europa

In April 2016 issue of Astronomy, a popular magazine, there is a feature article: "FINALLY. The historic journey to Europa." Europa is a Jupiter satellite of course. They say on page 25 that it will be a flyby mission with 45 revolutions around the moon only because the craft will eventually be destroyed by a powerful electron wind emanating from Jupiter. My questions are: (1) If there is a stable wind of electrons that means that Jupiter must be strongly positively charged and that charge must keep increasing. Is it what's happening? The second question is: (2) "What is the origin of those electrons? Thanks, --AboutFace 22 (talk) 16:32, 15 October 2016 (UTC)

We have an article about the mission at Europa Multiple-Flyby Mission (not sure it needs italicizing, but it is in the article) which leads to Magnetosphere of Jupiter, a featured article all about the topic of your question. Give those a look and come on back if there's anything that's still unclear. Matt Deres (talk) 16:36, 15 October 2016 (UTC)

(ec)Could it be that electrons move away from Jupiter at that location, but move towards Jupiter at other locations, in an equal amount, guiding by the Jovian magnetic field ? The other possibility is that the electron wind is in orbit, neither leaving nor hitting the planet. The actual answer may be a bit of both. (Hopefully Matt's links answer these follow-up Q's.) StuRat (talk) 16:42, 15 October 2016 (UTC)

The electrons are trapped in the same way as they trapped in Earth's radiation belts: they gyrate around the magnetic field lines while cyclically moving along the lines up and down out the equatorial plane. The word "wind" is a misnomer. Ruslik_Zero 18:55, 15 October 2016 (UTC)

Loudspeaker's size and weigh

Does a good loudspeaker, one that has deep basses and precise high frequencies, have to be heavy and bulky?--Llaanngg (talk) 17:00, 15 October 2016 (UTC)

As far as the bass goes, yes. To reproduce the lowest bass frequencies at a reasonable volume you have to move a lot of air, which means a cone with a large diameter and a long excursion, and the box itself has to be large and rigid. You can lighten it a bit with neodymium magnets and using plywood instead of heavier particle board, but that only helps some.

One good way around this is to use high-quality headphones. I highly recommend the Audio-technica ATH-M50. --Guy Macon (talk) 17:21, 15 October 2016 (UTC)

There are expensive systems that have good bass and small size, such as this one from Bose: [24]. But, there are limits, which is why built-in speakers on even high-end flat-screen TVs often sound horrid. The solution, if you don't need much volume, is a good 2.1 plug-in speaker system (right, left, and subwoofer speakers), which can give you decent bass for like $30. StuRat (talk) 17:24, 15 October 2016 (UTC)

• No, but it has to be stiff. Unless you have a supply of unobtainium, the necessary stiffness has usually been achieved (as this is the cheapest way) by using materials that are heavy and bulky. In a few cases, esoteric materials (mostly carbon fibre composites) have been used to produce lightweight bass speakers - often as horns (although most horns are used as mid-range drivers, large horns can handle bass). Bose speaker systems have tried this, using cheap injection moulded plastics and marketing. WP used to have a lot more on Bose, but it was deleted during one of the religious wars. So it goes.

A bass speaker will still have to be large though.

Headphones are a little different. The frequency response of eardrums are themselves limited, so much of the low frequency comes from bone conduction. This allows headphones to achieve a useful bass performance, despite the limits of their small drivers. Andy Dingley (talk) 19:15, 15 October 2016 (UTC)

Blood tests

When you look at your blood test results, which is the specific blood test that would indicate concerns for high cholesterol? Which is the specific blood test that would indicate concerns for diabetes? And are these specific tests usually included in the CBC (Complete Blood Count)? Or are they ordered specially and individually? Thanks. Joseph A. Spadaro (talk) 19:19, 15 October 2016 (UTC)

Cholesterol is tested using a Lipid profile. Diabetes is tested for by using Glycated hemoglobin levels. Neither is included in a Complete blood count, and will be requested specifically. Of course, to discuss the results of a particular blood test, or if you're worried about your health, you should consult an appropriate professional. Tevildo (talk) 19:49, 15 October 2016 (UTC)

At least in the U.S., they generally only order a glycated hemoglobin test if you have elevated glucose levels. Glucose level is part of the basic metabolic panel, which in turn seems to be part of the standard tests most doctors order. To the original poster, if you are having tests ordered for yourself, your doctor or other practitioner will probably answer any questions you might have. --47.138.165.200 (talk) 03:52, 16 October 2016 (UTC)

How do you *spill* methyl mercaptan?

The L.A. Times just published an enraging story about a community (Eight Mile, Alabama) reported to have endured 8 years of stench affecting 1300 people from 500 gallons of spilled methyl mercaptan.

What's confusing me is that methyl mercaptan is a gas sold in pressurized cylinders. How do you spill it, and why didn't it rapidly volatilize?

This is somewhat interesting since I see that a cylinder of methyl mercaptan seems to go for $200-$300 [25], so for $10,000 a person could have fifty of them and (perhaps) build a "dirty bomb" that apparently can leave an entire community seeking long term evacuation. Wnt (talk) 20:31, 15 October 2016 (UTC)

Under pressure higher boiling point gases will liquefy. When spilt as a liquid, it would boil and cool down more. Perhaps there are also traces of less volatile mercaptans contaminating the original gas. These could stay around longer. Also methyl mercaptan could have reacted with ambient substances to make other longer lasting smelly sulfur compounds. One cylinder would disrupt a shopping centre but we don't want too many WP:BEANS.Graeme Bartlett (talk) 20:51, 15 October 2016 (UTC)

Also after reading the article, it claims to be in ground water. It could be stored underground for quite a while. Bacteria should be able to dispose of it if they can get oxygen. Face masks as seen in the protest will do nothing to stop the odor. Graeme Bartlett (talk) 21:00, 15 October 2016 (UTC)

From the article Wnt linked, I found Mobile Gas' FAQ website, explaining that their investigation discovered a line used to carry odorant was damaged by lightning. So there was a continuous source of new chemical flowing through that line - and leaking - over a potentially long period of time. The facts about total quantity and duration, it seems, are subject to some dispute - hence the scandalous story as reported by the Los Angeles Times' reporters.

The website of Mobile Gas links to the State of Alabama's document archive, which contains even more information on the history and facts of the incident as they are known to the state government.

To follow up on Wnt's other concerns: most sources conclude that methyl mercaptan isn't harmful in the very low doses that one normally expects to encounter - but this material safety data sheet published by Chevron Phillips does list toxicity hazards as part of the full safety information for the chemical. In sufficient quantities, this chemical - like almost any other - transgresses beyond nuisance to become a real hazard. Once again, because there is some dispute about quantities and durations of exposure, the community and the company seem to disagree about whether the case in Eight Mile, Alabama, was a mere nuisance or a true health-hazard.

But the same is true of many hazards: if a malicious group wanted to create nuisance or hazard, they could do so with many hazardous items that are freely available in the United States. On the spectrum of things to worry about, I'd say methyl mercaptan "dirty bombs" are low on the priorities list. Emergency responders would probably be able to handle such an event by following "normal" HAZMAT emergency procedures. I'm inclined to link again to caltrops - if an anarchic and malicious person wanted to harm a community, they could do tremendous damage using only a few dollars of parts and no special skills; this doesn't diminish the threat of "unique" chemical attacks, but it does demonstrate that difficulty-of-execution is not the primary barrier that prevents such antisocial behavior.

Nimur (talk) 20:54, 15 October 2016 (UTC)

Thanks for pointing out that link! I should feel guilty for not checking that link when I read the article, but I think the author should feel more guilty for not checking it when she wrote the article. It says "Mobile Gas purchases its mercaptan from a vendor whose product contains a combination of tert-Butyl mercaptan and Methyl ethyl sulfide." I still have to look these up, but tert-butyl sounds heavy and more liquid and stickier.... yeah, we have an article! The methyl boils at 6 C, but the tert-butyl boils at 62-65 C. So indeed it can be spilled as a liquid and can take much longer to evaporate. I see prices as low as allegedly $600 a metric ton, if I believe Alibaba -- then again, I'm not sure I believe anyone here. I mean, the simplest answer to the riddle of the stench is that somebody is lying about how much was leaked out of that line by several orders of magnitude... Wnt (talk) 03:21, 16 October 2016 (UTC)

The same way you spill helium: Really fast. Sagittarian Milky Way (talk) 03:43, 16 October 2016 (UTC)

October 16

Radioactivity sucker

Is there such a device that can suck all the radioactivity out of something radio active. I just saw it on a science film?--86.187.171.5 (talk) 01:25, 16 October 2016 (UTC)

What was the name of the film? Ian.thomson (talk) 01:27, 16 October 2016 (UTC)

Usually you would have to do something like isotope separation. The time when you might be able to "suck" is when you remove radon, which is a gas. See radon mitigation. Nuclear reprocessing can be used if the radioactive substance is a different chemical element. Graeme Bartlett (talk) 02:01, 16 October 2016 (UTC)

Are you by any chance talking about X the Unknown, the article of which you edited prior to posting this question? If so, well, it's a science fiction film. There's a reason it's called that. --47.138.165.200 (talk) 03:58, 16 October 2016 (UTC)