Wikipedia:Reference desk/Archives/Science/2013 August 23

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.

August 23

the shape of heart

What is the geometric shape of the heart? Can I say that the heart is a truncated cone? (I do not think it is a truncated cone that is not really like that) — Preceding unsigned comment added by 46.210.149.99 (talk) 00:18, 23 August 2013 (UTC)

Asked and Answered on the Maths Desk
The following discussion has been closed. Please do not modify it.
For what purpose? In what context? μηδείς (talk) 00:28, 23 August 2013 (UTC) Let's presume the context is the human heart. Why does the purpose matter? Perhaps it's so that the IP can make a Heart-Shaped Box. --Demiurge1000 (talk) 02:06, 23 August 2013 (UTC) Kind of like a softball that's been hit a few too many times. ←Baseball Bugs What's up, Doc? carrots→ 03:12, 23 August 2013 (UTC) Is softball played much in Israel? CambridgeBayWeather (talk) 04:55, 23 August 2013 (UTC) Nah, they play strictly hardball. ←Baseball Bugs What's up, Doc? carrots→ 06:01, 23 August 2013 (UTC)

Breathing

If I inhale a mixture of gases called air which is 78.09% nitrogen, 20.95% oxygen, 1 % water vapour, 0.93% argon, 0.039% carbon dioxide, what mixture of gases do I exhale? Th4n3r (talk) 10:48, 23 August 2013 (UTC)

Amongst other things, it'll depend on your species, how long you held the breath, and the various physical conditions of your body. 86.141.186.4 (talk) 12:49, 23 August 2013 (UTC)

I think we can expect that the vast majority of those posting questions here are homo sapiens, and I might even go out on a limb and suggest that they are homo sapiens sapiens. StuRat (talk) 01:54, 25 August 2013 (UTC)

It depends on a great number of factors. Googling "rest oxygen consumption" returns a number of sites that give the oxygen consumption of adults as around 5% of what's available. It's converted to an equal volume of carbon dioxide. On this basis, the exhaled air will be 78.1 % nitrogen, 19.9% oxygen, 1.09% carbon dioxide, 1% water vapour, and 0.93% argon. Note that what you breaqth out is little changed from what you breath in, which is why mouth to mouth rescusitation works. Anything that increases metabolic rate will increase the conversion of oxygen to carbon dioxide - digesting a meal, physical exercise, thinking hard. Reacting to enviromental conditions will also increase it - for example shivering when cold. If you increase your body rate by either eating to much and getting fat, or building up muscle mass by exercise, your metabolic load increases but your lung volume capacity does not. (If you are quite obese, you lung capacity may be reduced, making you breath harder even at rest) Hence an increase in body weight will increase the percentage conversion of oxygen to carbon dioxide. Note that 1% water vapour in air represents 100% relative humidity at temperatures lower than 16 C, but only 20% rel humidity at 40 C. At the higher temperatures within the human comfort range, the body looses small amounts of water vapour to expired air. 1.122.214.154 (talk) 13:07, 23 August 2013 (UTC)

Don't forget that the water content will also increase; there's a lot of wet surface area inside the lungs. (The number above corresponds to only about 45% humidity at 20°C.) TenOfAllTrades(talk) 13:35, 23 August 2013 (UTC)

As is evident, especially in the winter, or when exhaling onto a glass surface. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:29, 23 August 2013 (UTC)

Alternative classification of Carnivora

Since not all Carnivora are in fact obligate carnivores and some are omnivores, is there some better and common (possibly unique) feature among them? Perhaps some taxonomists have proposed something on that? Brandmeister^talk 10:58, 23 August 2013 (UTC)

I would venture to suggest: their descent and relatedness. Linnean taxonomy used to be based on an ad-hoc mixture of visually obvious physical similarities, which taken in aggregate gave clues to organisms' actual relatedness (and were sometimes ambiguous or misleading), but nowadays it uses the much more rigorous methods of Cladistics, and can be corroborated by direct genetic comparisons. Characteristics that specific groups might have largely or uniquely in common are handy aide-memoires, but not ultimately definitive, because Evolution (if you'll excuse the trope). {The poster formerly known as 87.81.230.195} 212.95.237.92 (talk) 12:53, 23 August 2013 (UTC)

Yes, ultimately ancestry is the real basis of classification. Often there are physical features that are highly characteristic, but they may not be obvious -- for example the layout of the teeth is often one of the most informative things. So is the bone structure of the foot. I don't know enough about this group to say anything specific, though. Looie496 (talk) 14:59, 23 August 2013 (UTC)

Yes, not all Carnivorans are obligate carnivores -- so what? As Carnivora indicates, the extant Carnivorans form a monophyletic group, which is about as good as it gets for modern cladistics/systematics. I'm not sure what feature they would all share, because the pinnipeds are a rather different from the rest. Perhaps there is some shared skeletal feature, but it would be pretty opaque to a non-specialist. As .195 says above, what they share is common descent. Conceivably, we could change the name to "Foofles", while keeping all members the same, but that would cause its own headaches. The way the International_Code_of_Zoological_Nomenclature works, names should follow the Principle of priority, unless there is some other good reason to change them (e.g. splitting an old paraphyletic group into two or more new monophyletic ones). Finally, beware the etymological fallacy! Hope that helps, SemanticMantis (talk) 15:03, 23 August 2013 (UTC)

That is, in my opinion, naming that order because of dietary habits is problematic (and, possibly, in other cases too): several non-carnivorans also prey and eat meat as their staple food, thus also being eligible for the name Carnivora. Just found a source, which says in particular: "carnivorans never develop shearing dentition beyond the original P4/mi carnassial pair, and this combination of shearing and grinding dentition has served Carnivora well". Perhaps the International Commission on Zoological Nomenclature will someday reconsider :) Brandmeister^talk 17:51, 23 August 2013 (UTC)

I understand your objection to Carnivora, but it is actually very common for things to work out this way. It's just what happens when we prefer original names, but also want to use modern tools to make clades as large and inclusive as they can correctly be made. Does it bother you that not all hemiptera have "half-wings"? Or that not all Orthoptera have "straight wings"? It's a terrible system, but it's the best we've got :) SemanticMantis (talk) 18:15, 23 August 2013 (UTC)

• See etymological fallacy. Come back if you have some questions about the relevance of that article to this problem. --Jayron32 14:56, 24 August 2013 (UTC)

Enemy locked onto heat signature; release flares

In the game Battlefield 3, one mission requires the player to occupy the gunner position in some sort of fighter aircraft. When the enemy locks onto the heat signature, a system of the aircraft occupied by the player warns the player and warns further when a missile is fired. The player is expected to release flares to thwart the enemy missile. How does the system recognise that the enemy aircraft has locked onto the heat signature? --89.241.229.123 (talk) 14:14, 23 August 2013 (UTC)

By what method does the attacker "lock on"? If it's via radio waves, those waves could be detected by the target vehicle's systems. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:28, 23 August 2013 (UTC)

Is the question about how the video game software operates this feature, or how its real-world counterpart works? Video games tend to use "omniscient software" that is aware of enemy moves, which simplifies the design and allows the creators to provide the desired user-experience.

In real life, a heat-seeking missile is not easy to detect. Because infrared missiles uses passive homing, they don't broadcast any type of strong signal. So the defending aircraft must use its own active RADAR to detect an unidentified object in the area; its onboard computer must calculate a trajectory and identify it as a potential missile; and then by deduction, it can be assumed to be a heat-seeker if it satisfies certain characteristics (size, velocity, RADAR signature - or lack thereof). This is an estimation problem that is prone to error and misidentification. Electronic warfare aircraft may escort fighter-aircraft in combat; these special airplanes carry more and better RADARs and computers (and other instruments) to help reduce error. Modern air doctrine emphasizes "Coordinated Command and Control" - enabling multiple airplanes, as well as ground and satellite facilities, to share combat information in real time, to help reduce errors in identification of unknown targets. Nimur (talk) 14:43, 23 August 2013 (UTC)

Here's a link to a Missile Launch Detector that Lockheed Martin makes [1]. It's a bit hard to tell, but it seems to work by detecting the IR flash of missile launch and then tracking the hot exhaust during flight. This discusses, briefly, the large dust and smoke plume from a Surface-to-air missile. Neither of these detection methods will work with a passive IR guided missile until the missile launches.Tobyc75 (talk) 18:18, 23 August 2013 (UTC)

Is there any condition in which two vectors can be divided?

Is there any condition in which two vectors can be divided? Concepts of Physics (talk) 14:52, 23 August 2013 (UTC)

This is not a common terminology for any commonplace operation in engineering or physics. You can define many mathematical operators that have qualitative similarities to division and accept vectors as inputs. But most people who use those operations prefer to use a different, more precise term, like computing an inverse or left-multiplication by the adjoint matrix. Nimur (talk) 14:57, 23 August 2013 (UTC)

This was discussed at length a month ago. Red Act (talk) 15:04, 23 August 2013 (UTC)

This page shows division of two vectors. Is this method correct? Concepts of Physics (talk) 15:28, 23 August 2013 (UTC)

That is a correct example for R (programming language) where the term "vector" is understood to be a one-dimensional array and where division is done element by element. This is a different use of "vector" than Vector (mathematics and physics). -- 200.7.90.57 (talk) 15:52, 23 August 2013 (UTC)

Division is the inverse of multiplication, so before answering that question you must chose some kind of multiplication to invert. The most common multiplication methods for vector dot product and cross product cannot be inverted. Dauto (talk) 18:20, 23 August 2013 (UTC)

If you want a fancy name for the operation described by 200.7.90.57, try Hadamard product. --Wrongfilter (talk) 21:05, 23 August 2013 (UTC)

Gap spanners on the International Space Station

What are the "gap spanners" that I read about astronauts installing on the International Space Station? The best I can find is that they are "used by spacewalkers to get from one module to another", but I can't find any details. Are they cables? Are they rods? What are they made out of? How are they attached? Are there any good photos of them online? -- 200.7.90.57 (talk) 15:30, 23 August 2013 (UTC)

Astronaut Jerry L. Ross, who flew on STS-88, explains gap spanners in this crew interview, available from spaceflight.nasa.gov:

“ Because the Unity node is so large in diameter we couldn't mount all the hardware on the outside of its structure that we wanted to, while it was still in the payload bay of the orbiter, and the launch environment that exists there. So, Jim and I will be installing a series of additional handrails, or handholds, on the outside of the station which we'll need for tasks, either on our flight or future ones. We'll also be putting some additional foot restraint sockets on the outside of the structure that we can plug our foot restraints into to do tasks on this EVA as well as others. We have a thing called a gap spanner, which is really nothing more than a long piece of strap that we're going to attach between a couple of handholds and cinch tight. That is a way of bridging a gap that was too long between handholds to provide a continuous translation path for crewmembers to operate on the station. ”

So, it seems like a gap spanner is a pretty mundane piece of cloth... until you realize that it's a festering breeding ground for orbital space-fungus! Here's a very high resolution photo from the same page of a ground technician swabbing the fungus off a gap spanner. Nothing is mundane or routine in manned space flight! Nimur (talk) 14:24, 24 August 2013 (UTC)

Thank you, Nimur. You're my hero! -- 200.7.90.57 (talk) 15:39, 24 August 2013 (UTC)

the haert rate in different bodies sizes

What is the reason that the big body is with low heart rate and a small body is with high heart rate? In example: addult from 10 years and above has heart rate of 60-100 per minute while an infant (until 90 days) has heart rate of 80-205 per minute! The same things are in animals. In example: the elphent has 25 HR per minut while the mouse has about 500 heart rate per minuts! So, in short: Why does as much as the body smaller the heart has high heart rate? 95.35.239.134 (talk) 16:36, 23 August 2013 (UTC)

It's partially related to one's activities. Many small animals are much more active than big ones, as such they require higher physical performance (particularly, better oxygen supply) which in turn requires high heart rate. Mice in particular are constantly vigilant to avoid predators, requiring higher physical performance and as such high heart rate. Brandmeister^talk 18:08, 23 August 2013 (UTC)

All right on mice you can say that they are active, but what do you say about babies compared to children? Children more active and yet they have only 60-100 beats per minute compared to babies who sleep most of the day and have between 85 -205 beats per minute.95.35.239.134 (talk) 19:56, 23 August 2013 (UTC)

My guess is that the size of the heart is also important, as a bigger heart can of course pump more blood than a smaller one if both were pumping at a similar speed. Since blood flow is limited by the elasticity of the blood vessels, I'm guessing a big heart pumping very quickly could create too much pressure and rupture the veins, especially if the diameter of the various types of veins does not increase proportionally to the size of the heart. I'm unable to confirm my guesses with reliable sources at the moment, however. Effovex (talk) 20:11, 23 August 2013 (UTC)

The typical operating speed (and presumably the most efficient speed) of mechanical devices, such as pumps, motors, and engines, trends to be inversely proportional to their size. Perhaps someone here with a mechanical engineering background can speak to this point. -- 200.7.90.57 (talk) 20:37, 23 August 2013 (UTC)

Indeed, though the reasons are somewhat different. The heart pumps by successive contractions. That means that at every beat it accelerates a small quantity of blood, which then gets decelerated in the blood vessels. The kinetic energy imparted to the blood depends on the ex-chamber spurt time, and the stroke/spurt distance. In a small animal the stroke distance (which is proportional to the length and to the width of the heart) is less, so to impart the same kinetic energy per unit volume of blood, and thus get the same blood velocity, the time per beat must be shortened. In animals of all sizes, the required blood velocity is much the same, as it is set by capilary wall thickness, gas and nutrient diffusion range, and tissue requirements. 1.122.171.86 (talk) 00:36, 24 August 2013 (UTC)

survive in a space station without air renewal

Suppose you are in the International Space Station, with destroyed air renewal systems and no other sources of oxygen.

You have plenty of food and water (but you cannot use it to produce oxygen). At the beginning the air is fresh.

How long can you survive there? Months? --Blacknight87 (talk) 17:27, 23 August 2013 (UTC)

Several days, certainly not reaching one month, I think (around one week at best) until the buildup of carbon dioxide reaches critical point. To extend the survival period it's possible to isolate every room by sealing hatch or whatever and once the CO2 level in one room reaches uncomfortable point, move to another. But still there should be some emergency backup system out there. Brandmeister^talk

There are Oxygen candles in the ISS. CO2 is usually deadly at about 10%. A human produces about 1 kg of CO2 a day. The molar mass of CO2 is 44 g, so 1 kg is about 23 moles or about 500 l of CO2 under normal condition. The ISS has a pressurized volume of 837 m³. So 10% concentration should be reached in 160 (person-)days. That is a lot longer than I would have expected. --Stephan Schulz (talk) 18:33, 23 August 2013 (UTC)

But is it enough oxygen for 160 days? --Zhitelew (talk) 18:57, 23 August 2013 (UTC)

Since one molecule of O2 makes one molecule of CO2, and both gasses have more-or-less (for small values of less!) the same volume under normal conditions, yes. Unless I made a stupid mistake ;-). --Stephan Schulz (talk) 19:40, 23 August 2013 (UTC)

I suspect that that 10% figure is rather too high. NIOSH (CDC) puts the IDLH level at 4% [2], noting that it produces symptoms of intoxication within 30 minutes at 5%, and unconsciousness after a few minutes at 7%. A study on submariners reported that extended exposure to 3% CO2 produced only mild symptoms, provided sufficient oxygen was provided. Using a more realistic 4% threshold, the lone astronaut on the ISS is good for perhaps 60 days—assuming that there are no other chemical or biochemical processes on board that produce additional carbon dioxide..... TenOfAllTrades(talk) 23:22, 23 August 2013 (UTC)

To look at it from another direction, the Lunar Excursion Module (LEM) on the ill-fated Apollo 13 mission had an internal volume of 6.7 cubic meters...less than 1% of the internal volume of the ISS. The oxygen and CO2 removal provided in the LEM was intended to be enough for 72 man/hours (2 men, one and a half days) - and had to suffice for 288 man/hours (three men, four days) to get the crew safely home. Notably, they didn't run even close to being short of oxygen - but when the CO2 removal system was rapidly overwhelmed, they ran to the brink of CO2 poisoning until the famous "square peg into a round hole" fix was developed. But you can see that even with only 1% of the volume, it took a considerable amount of time for the extra astronaut to overwhelm the LEM's filters to the point of danger. With over 100 times as much volume, that would take 100 times a long. This suggests that (a) Oxygen deprivation would not be an issue - CO2 would be the major problem and (b) that User:Stephan Schulz's calculations are probably about right. SteveBaker (talk) 21:16, 23 August 2013 (UTC)

Part of the reason why the CO2 level rose so 'slowly' in the LM was that the scrubber unit wasn't fully exhausted. As the scrubber gets to the end of its lifetime, the particles of lithium hydroxide in the canister acquire a coating of lithium carbonate, making them much less efficient absorbers of CO2 (as the gas has to diffuse through the inert carbonate to get to the active hydroxide). While the scrubber canister would normally be replaced at that point, if one is willing to tolerate an elevated partial pressure of CO2 in the cabin then one can run the canister much closer to exhaustion—let those little particles marinate in more concentrated CO2, consuming the lithium hydroxide more completely and absorbing more CO2 before their retirement.

In the case of the LM, its original canisters had a design capacity for efficient scrubbing of 60 man-hours, but could remain in service for twice that time at a cost of higher ambient CO2 levels if absolutely necessary. (On Apollo 13, they ran for 107 man-hours before the CM units could be connected.) In addition, there was a spare unit good for another 40 man-hours of normal use (80 man-hours in an emergency) if the square-peg-round-hole fix took longer than anticipated. [3] If the scrubbers were completely gone, using the 1 kg per day per person round figure Stephan employed above, the lunar module would have been out of luck in less than half a day. TenOfAllTrades(talk) 23:11, 23 August 2013 (UTC)

Thanks! That's great information. But I think the conclusion is the same - it's not running out of oxygen that's the problem. It's build-up of CO2. If CO2 could be perfectly removed, how long would it be before the astronauts have too little oxygen? My gut feel is that it's MUCH longer. SteveBaker (talk) 15:55, 24 August 2013 (UTC)

Do they have suicide pills on board so they don't have to suffocate to death? How long /would/ they last if the zombie apocalypse suddenly happened or something? Is it CO2 poisoning or is there something else needed from the ground that must happen before the air runs out? 108.27.81.195 (talk) 00:56, 24 August 2013 (UTC)

Under normal conditions, they keep a Soyuz capsule docked on the station that can be used as an emergency return vehicle if necessary. Assuming conditions on the Earth's surface are survivable there is a good chance that the crew would attempt to return to Earth before they ran out of air. However, I'm not entirely sure how easy or difficult it would be to manage a reentry if ground control had been destroyed. Dragons flight (talk) 04:23, 24 August 2013 (UTC)

They don't really need suicide pills - CO2 is commonly used for animal euthanasia, and of course they have a perfect "high altitude chamber" close at hand. Wnt (talk) 07:03, 25 August 2013 (UTC)

Also, until 2007, cosmonauts were issued with the TP-82 pistol - according to our article, they're still issued with "a regular semi-automatic pistol" - so they probably have at least one gun up there as well. Tevildo (talk) 17:35, 25 August 2013 (UTC)

Femininity facial analysis?

The Bradley/Chelsea Manning story has me wondering: with all the fancy facial recognition software, and research into reactions people have toward averaged faces, is there a program available that can analyze "femininity" in a face, either from a 2D picture or in person/3D? To me Manning's face always seemed a little bit female, and I was wondering if that is quantifiable. If so, does it actually predict some increase in odds of being transgendered or gay? Wnt (talk) 18:59, 23 August 2013 (UTC)

Here's a good list of refs, 101 of them about determining/sex gender of human faces via computer vision algorithms [4] (search is articles related to a seemingly influential paper on the topic [5]). There seems to have been a boom in the 1990-2006 range, but it's still being researched at a steady pace. It looks like even 10 year old routines can discriminate about as well as humans (~90% accuracy, hair removed or hidden), using things like support vector machines. Two articles jumped out as highly relevant to your question: "What's the difference between men and women? Evidence from facial measurement" [6], and "Boosting Sex Identification Performance" [7]. Some of these papers might have code online as supplementary material, or allow a (sufficiently savvy) reader to implement the algorithm. I didn't look for "off the shelf" software. SemanticMantis (talk) 21:01, 23 August 2013 (UTC)

Well, how does one DEFINE femininity? Seems to me like this is a highly subjective thing to evaluate. 24.23.196.85 (talk) 01:07, 24 August 2013 (UTC)

How about with science, like SemanticMantis demonstrated with references and logic, and a surprisng lack of caps. Shadowjams (talk) 06:05, 24 August 2013 (UTC)

Yes, defining femininity is problematic. Note also that the papers are mostly about determining sex, not gender. In this case "female-ness" might be a better word than femininity, when discussion how computer algorithms score faces. SemanticMantis (talk) 14:24, 24 August 2013 (UTC)

How about those physical traits that estrogen gives. For testosterone that would be square face, baldness, beard etc. Electron9 (talk) 17:29, 26 August 2013 (UTC)

And note that feminine men are only a subset of gay men ("twinks"). There are others who are ultra-butch ("bears"), and everything in-between. StuRat (talk) 01:46, 25 August 2013 (UTC)

I should thank SemanticMantis for some good sources ... though I haven't managed to access several of them in full as of yet. Do you know whether these 90% or so accurate algorithms misidentify the same people as being of the wrong sex, or is it different for each one? It didn't look like anyone was actually trying to identify "quantitative" variations in sex though. Wnt (talk) 07:00, 25 August 2013 (UTC)

Wnt, I think that quantitative "scoring" does happen inside the algorithms, but no idea on if one face fools all the algorithms, or each is tricked by different faces. I suppose there should be some "Standard face set", but not sure how many of those papers use it.

For the support vector machine approach, some finite list of quantified attributes is used to represent each face as a vector. The goal of the machine is to make the best hyperplane to separate the data so that females are on the "right", and males on the "left". In this case, the hyperplane would describe the the most androgynous faces. So you could at least come up with an "androgyny score", based on distance to the separating hyperplane, and then large distances would be either "very male" or "very female", depending on which side of the hyperplane the face is on. Anyway, if you want a specific paper, drop me a line on my talk page or email, I can probably send you pdf. SemanticMantis (talk) 18:13, 26 August 2013 (UTC)

Geology/Pleistocene/CLIMAP

During the 1970's, CLIMAP was created to draw a map of the world at the time of the glacial maximum, 13Kya, (or is it earlier?). Where can I find that map and where can I find maps of North America between then and now. I have a particular interest in Lake Bonneville and Lake Agassiz.Bobgustafson1 (talk) 19:19, 23 August 2013 (UTC)

You might start with out article on CLIMAP: Climate: Long range Investigation, Mapping, and Prediction. It contains a reference to "CLIMAP (1981). Seasonal reconstructions of the Earth’s surface at the last glacial maximum in Map Series, Technical Report MC-36. Boulder, Colorado: Geological Society of America.", which probably provides many more details, though you'd probably need a good research library to find that book. However, it would be a mistake to think of CLIMAP as aiming to "draw a map". Rather it was a collection of related research projects to document conditions as they existed on Earth about ~18 kya. There would be many maps, some regional, some global, each reflecting or summarizing different parts of the investigation. In addition, other results of the related studies are probably scattered through various academic journals from that time period. Since you asked, reading about Lake Agassiz and Lake Bonneville might also be useful. My impression though is that our understanding of Lake Agassiz and its changes through time have improved greatly since the 70s, so you might want to look at more recent reviews. Dragons flight (talk) 20:14, 23 August 2013 (UTC)

Adults

Do mle adults have XY chromosomes and female adult humans have XX chromosomes? If so, is it possible to change theses chromosomes? Pass a Method talk 22:07, 23 August 2013 (UTC)

See biological sex, gender, sex chromosomes, XY sex-determination system, aneuploidy, sex differences in humans. The short answer to the first question is "mostly". The short answer to the second is "no". 86.163.2.116 (talk) 22:17, 23 August 2013 (UTC)

Yes, mostly; no. See also, incomplete penetration. μηδείς (talk) 04:54, 24 August 2013 (UTC)

See also, hmmm, androgen insensitivity, testicular feminization, freemartin, intersex, Klinefelter syndrome Turner syndrome, XYY syndrome. Note that there is research underway to extend X inactivation to chromosome 21 so as to offer treatment to people with Down syndrome, for example, but this is still far off (no obvious research path to a successful, safe whole-body gene therapy of every cell to do it). But it wouldn't be much to modify that to a goal of changing the sex chromosomes. That said, wrong-sex gonads and other tissues in someone of the other sex hormonally can be cancer risks, so even if you make the change without incident the goal itself might have additional dangers. Wnt (talk) 19:42, 24 August 2013 (UTC)