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February 13[edit]

Einstein's theory was wrong[edit]

Last sentence of this article Spacetime in General relativity says Einstein's theory was wrong, which surprised me. According to me, this is wrong since this article doesn't contain any reference. What do you think about this? 27.62.78.249 (talk) 02:40, 13 February 2013 (UTC)[reply]

That was just a vandal, and he's been reverted. It's a terrible article though, in any event. Someguy1221 (talk) 02:41, 13 February 2013 (UTC)[reply]

Holy cow, you aren't exagerating... Snow (talk) 02:48, 13 February 2013 (UTC)[reply]

Human beings can believe in terrible ideas. It is no wonder some people believed Eistein's theory was wrong. --PlanetEditor (talk) 03:50, 13 February 2013 (UTC)[reply]

My favourite wacky website Conservapedia has a particular problem with Einstein, see E=mc²? Not on Conservapedia Dmcq (talk) 11:45, 13 February 2013 (UTC)[reply]

It's there under Einstein himself,[1] and has been since at May of 2007.[2] Maybe no one has bothered to write a separate article about it there yet. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:32, 13 February 2013 (UTC)[reply]

OMG! I see why that vandal "improved" our article.

That's incredible...evidently, in the Bible: John 4:46-54, it says that a man visited Jesus saying that his son was dying - Jesus tells him to go home and his son will be just fine. The guy goes back and his household staff tells him that his son got better at 1pm the previous day which was the exact same time he was talking to Jesus! Cool!! So we may conclude that it took zero amount of time for Jesus' cure to reach the child - which means that the cure travelled faster than the speed of light - which Einstein said was impossible! The bible must be right, ergo Einstein was wrong and presumably the Missouri House of Representatives can mandate that it shouldn't be taught in schools. I guess Newton is still OK though...(although he rejected trinitarianism, so you'd better get your kids to learn "f=ma" while they still can - I fear calculus is already a lost cause!)

From which I infer that millisecond (or better) clocks were in routine use in Jesus' time, and that some Christians don't really believe in miracles. —Tamfang (talk) 19:10, 3 December 2013 (UTC)[reply]

Then...if that's not enough...we are told that Obama used Einstein's Relativity to "prove" that abortion is OK. The truth of that turns out to be that about 20 years ago, some legal theorist wrote that just as Einstein showed that space-time is curved by gravity, so the landscape of our legal system is changed by the way people interpret the law. He then goes on to use the abortion debate as an example of that changing legal landscape. This paper was published in an obscure law journal that Obama was the editor of. Obama neither wrote nor endorsed the paper, he merely accepted it for publication - the paper made no mention of relativity having anything whatever to do with abortion or even advocated on either side of the abortion debate. But now Einstein is on the religious nut's shit-list right up there with Darwin.

Wow!...just Wow!

SteveBaker (talk) 15:01, 13 February 2013 (UTC)[reply]

Clearly you haven't read much ID literature :-). Einstein has always been on the shit list. One of the greatest difficulties for ID proponents is to explain why, if the world is only a few thousand years old, light from distant stars appears to have been traveling toward us for millions or billions of years. Unless you assume that the light was created "in transit" -- which seems absurd even to ID proponents -- there is no way to make things work without trashing relativity. Looie496 (talk) 16:00, 13 February 2013 (UTC)[reply]

But without a finite speed of light, explaining red-shift would be exceedingly difficult. Understanding why there is a lag in transatlantic telephone calls made via satellite gets tricky...well, all manner of very obvious facts about what we see in our daily lives would be exceedingly hard to explain. These computers we're typing on would be very different beasts if the speed of light were any different than it is. Argh...there is simply no point in chasing it down this particular rabbit-hole. Demolishing these arguments is like shooting fish in a barrel. SteveBaker (talk) 20:41, 13 February 2013 (UTC)[reply]

Devils advocate: If you really wanted, you could explain redshift and propagation delay without a finite speed of light by assuming luminiferous aether exists (with some adjustments of course, perhaps assuming that the aether flows under gravity). Ariel. (talk) 23:05, 13 February 2013 (UTC)[reply]

I see Conservapedia now have a E=Mc² article. It was set up with the comment 'E=mc2 is a meaningless statement in physics that purports to relate light to matter. In fact, no theory has successfully unified the laws governing mass (i.e., gravity) with the laws'. So perhaps to say that they cover it is about equivalent to saying we cover the government conspiracy over 9/11. Dmcq (talk) 20:48, 13 February 2013 (UTC)[reply]

Wait a minute... Conservapedia actually says that 9/11 was a government conspiracy?! 24.23.196.85 (talk) 02:05, 15 February 2013 (UTC)[reply]

No it doesn't either -- in fact, it REFUDIATES all such conspiracist bullshit! Here's their actual article about 9/11 24.23.196.85 (talk) 02:11, 15 February 2013 (UTC)[reply]

No I should have been clearer, someone above said that they did have E=Mc² but I was saying they have that in only in the same sense as we have 9/11 was a government conspiracy in Wikipedia. Sorry for confusing things. Dmcq (talk) 14:31, 15 February 2013 (UTC)[reply]

"Simply put, E=mc² is liberal claptrap." --PlanetEditor (talk) 02:26, 14 February 2013 (UTC)[reply]

How many times thicker is the dermis than the epidermis?[edit]

At the same spot. Sagittarian Milky Way (talk) 02:59, 13 February 2013 (UTC)[reply]

Well, the thickness of dermis and epidermis are not the same at every spot of your body; the thickness varies. The epidermis is 0.05 mm ( eyelids) to 1.5 mm (palms and soles) thick at different places. On the other hand, the dermis is 0.3 mm to 4 mm thick at different spots. As a rule of thumb, the dermis is 10 times thicker than epidermis at the same spot. But this thickness can go further in the range of 10 to 40 times at some places. --PlanetEditor (talk) 03:09, 13 February 2013 (UTC)[reply]

(edit conflict)

"The dermis is 10 to 40 times thicker than the epidermis.""^[3]

~:74.60.29.141 (talk) 03:13, 13 February 2013 (UTC)[reply]

But this "rule" does not apply uniformly. For example, according to the Wikipedia article Skin, the skin on the palms is 4 mm thick and the epidermis on the palms is 1.5 mm thick. So the dermis on the palms is 4 - 1.5 = 2.5 mm thick. So the dermis on the palms is 1.6 times thicker than the epidermis on the palms. How is it 10 times thicker? --PlanetEditor (talk) 03:41, 13 February 2013 (UTC)[reply]

Value chain of SLES (Sodium Lauryl Ether Sulfate)[edit]

Need to know the value chain of SLES (Sodium Lauryl Ether Sulfate) with all the respective % , sources, Process and cost indication details — Preceding unsigned comment added by 170.252.219.1 (talk) 04:24, 13 February 2013 (UTC)[reply]

Please do your own homework.

Welcome to Wikipedia. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know.--Jayron32 06:06, 13 February 2013 (UTC)[reply]

I'm not so sure it's homework, but I'd be curious how you answer this. I looked up value chain... I know the difference between sodium laureth sulfate and sodium laurel sulfate (the former has some ethanol units pasted between the twelve carbon chain and the sulfate), and from the article I know it is made by "ethoxylation of dodecyl alcohol. The resulting ethoxylate is converted to a half ester of sulfuric acid, which is neutralized by conversion to the sodium salt." The dodecyl alcohol apparently comes from reduction of coconut or palm oil. But how do you find out what companies do this, what their efficiency and profit margin is in modern practice (as opposed to probably ancient journal publications about efficiency of the synthesis in the lab)? Does a question like this go all the way back to the coconut plantation? It would be good to see this answered properly. Wnt (talk) 04:48, 15 February 2013 (UTC)[reply]

I'm not so sure that the coconut plantation has to be involved in the production process in any shape or form -- last I checked, they could also make sodium lauryl sulfate from ethylene by Ziegler-Natta polymerization (and I know these things -- petrochemicals are my area of expertise). 24.23.196.85 (talk) 06:17, 15 February 2013 (UTC)[reply]

Homo sapiens subspecies[edit]

I was just going through the article Elephas maximus and found the basis of their subspecies classification:

Elephas maximus maximus: shoulder height between 2 and 3.5 m, 19 pairs of ribs, skin color is darker than of indicus and of sumatranus
Elephas maximus indicus: shoulder height between 2 and 3.5 m, 19 pairs of ribs, skin color is lighter than of maximus with smaller patches of depigmentation, but darker than of sumatranus
Elephas maximus sumatranus: shoulder height between 2 and 3.2 m, 20 pairs of ribs, skin color is lighter than of maximus and indicus with least depigmentation

Then I read the article Subspecies. According to Subspecies#Criteria,

Members of one subspecies differ morphologically or by different coding sequences of DNA from members of other subspecies of the species. Subspecies are defined in relation to species.

This means a species may have two or more subspecies which are:

either morphologically different, or
genetically different, or
both.

Now I have a thought. If elephants can be divided into different subspecies based on morphological differences, why can't humans be classified into different subspecies given that humans have vast morphological as well as genetic differences. I'm not talking about the extinct Homo sapiens idaltu or the extinct Homo sapiens neanderthalensis, I'm talking about extant Homo sapiens. Also, it has nothing to do with scientific racism which is the scientific manifestation of the political belief of racial superiority. Differentiating humans into different subspecies should be scientific (just as in the case of Asian elephants) and does not claim one subspecies is superior to the other, it is just morphological and genetic differences. So I'm curious to know why humans have not been classified into subspecies. --PlanetEditor (talk) 09:20, 13 February 2013 (UTC)[reply]

In modern times with modern techniques, a new classification of subspecies would only be accepted if it had at least a hypothetical phylogenetic basis. And although you can classify people into groups based on genetic similarities, it's very difficult to form a monophyletic groups of humans that can be distinguished from other such groups by any significant, unique characteristics. You can certainly group people by race, and these groupings will have some genetic and morphological traits they share more often with eachother than with outgroups, but it will not be taxonomically valid. And that's not to even mention all the interbreeding that takes place. Read more at race and genetics. I know you didn't ask specifically about race, but that's the most on-topic article. Someguy1221 (talk) 09:33, 13 February 2013 (UTC)[reply]

Thanks for the explanation. --PlanetEditor (talk) 10:57, 13 February 2013 (UTC)[reply]

Homo sapiens sapiens, Homo sapiens neanderthalensis. μηδείς (talk) 18:02, 13 February 2013 (UTC)[reply]

Homo sapiens idaltu. RNealK (talk) 22:23, 13 February 2013 (UTC)[reply]

If you're interested in this, the starting point of your research should be Human mitochondrial DNA haplogroup and Early human migrations. There is a torrent of information in those articles, much of it quite recent, and I haven't kept up with all of it. But to cut to the chase, the best candidates for a subspecies would be the members of Haplogroup L0 (mtDNA), which our article says is 100% prevalent in the ǃKung people, renowned to us for their differences as Bushmen and "Hottentot Venus". Everyone not in L0 has mitochondria more related to one another than to the L0 members. That said, however, the various mitochondrial subtypes are very commonly mixed in a race; races with different haplotypes can look very similar and can look very different with the same haplotype; and even if populations are separate in matrilineal contributions that doesn't mean there hasn't been other gene flow, nor does it immediately rule out a more recent founder effect to explain the prevalence of one mitochondrial type. I recall that mainstream opinion, e.g. Stephen Jay Gould, was that the people of South Africa carry 99% of all human genetic variation among them, making the distinction in mitochondrial subtype quite an anomaly. One might try to present the !Kung are some rare remnant of an ancestral subspecies with much of Africa as a hybrid zone, but it would appear that nobody has made that case, to say the least. Now looking to see if anyone has tried to go down this path and claim enough genetic separation to make a subspecies a meaningful thing, I run into rather disturbing "European Culture" type websites that talk about "Khoisanids", formerly Capoids, but it has a very fringey feel to it. Hunting for the most interesting bit, the steatopygia and L0 (relating the mitochondrial marker to some visible sign would at least be a beginning) I came up with [4] which says that some southern Sandawe have steatopygia like the Khoisan, and it turns out that according to our article on Macro-haplogroup L (mtDNA) they have some L0d "indicating a connection to the Khoisan". So there's the absolute skeleton there of an argument that you could say that humans should "really" be counted as a polytypic species with big beautiful butts associated with this marker and smaller daintier butts with all the others, but, well, nobody has put in the research to prove it. Dunno why, it sounds like you could recruit volunteers to wield the tape measures pretty easily. :) Plus, you have the obvious flaw that the Onge (also listed in steatopygia) are in subgroup M (of L3, of L1-6, not L0) so the trait can arise in other populations, which rather undermines the idea of using it to define two independent taxons. In any case, it seems like too small and pedantic a character to really justify calling the humans two subspecies, and of course I wouldn't be surprised if some researchers are wisely steering clear of the point for fear that some idiot will try to use it for a racist argument, though not a particularly logical one. Wnt (talk) 23:17, 16 February 2013 (UTC)[reply]

What is the latest on olive oil and antioxidants? Are they supposed to be good or bad for you now?[edit]

What is the latest on olive oil and antioxidants? On balance of the best evidence available, are they supposed to be good or bad for your health? --173.49.81.79 (talk) 13:36, 13 February 2013 (UTC)[reply]

On the balance of what? Insofar as you use olive oil in stead of other oils, it is probably better for you than those other oils, but in general it is best to keep overall fat consumption low (not zero, but probably lower than the average western diet). So olive oil is both good (better than other, highly refined oils) and bad (too much fat in a diet of any sort can be problematic). And there are several "antioxidants"(which is a marketing term that has become almost meaningless due to its overuse) which are not only good, but are vital, such as Vitamin C. --Jayron32 13:46, 13 February 2013 (UTC)[reply]

Too much anything (fat, carbohydrates, protein, vitamins, mineral, water, oxygen) is bad for health. What is important is to check the daily total calorie consumption. A popular misconception exists about carbohydrates. Carbohydrates are not essential nutrients; although dietary fibers are important for health. Carbohydrates only provide energy, and processed carbohydrates (high glycemic load) and fruits (due to presence of fructose) do a lot of harm. --PlanetEditor (talk) 14:14, 13 February 2013 (UTC)[reply]

"Fruits (due to presence of fructose) do a lot of harm"?^{[citation needed]} From Fructose#Compared to sucrose:

Fructose is often recommended for diabetics because it does not trigger the production of insulin by pancreatic β cells, probably because β cells have low levels of GLUT5.[57][58][59] Fructose has a very low glycemic index of 19 ± 2, compared with 100 for glucose and 68 ± 5 for sucrose.[60] Fructose is also seventy-three percent sweeter than sucrose (see relative sweetness) at room temperature, so diabetics can use less of it. Studies show that fructose consumed before a meal may even lessen the glycemic response of the meal.[61]

And from Fruit#Nutritional value:

Fruits are generally high in fiber, water, vitamin C and sugars, although this latter varies widely from traces as in lime, to 61% of the fresh weight of the date.[31] Fruits also contain various phytochemicals that do not yet have an RDA/RDI listing under most nutritional factsheets, and which research indicates are required for proper long-term cellular health and disease prevention. Regular consumption of fruit is associated with reduced risks of cancer, cardiovascular disease (especially coronary heart disease), stroke, Alzheimer disease, cataracts, and some of the functional declines associated with aging.[32]

Diets that include a sufficient amount of potassium from fruits and vegetables also help reduce the chance of developing kidney stones and may help reduce the effects of bone-loss. Fruits are also low in calories which would help lower one's calorie intake as part of a weight-loss diet.[33]

Duoduoduo (talk) 16:08, 14 February 2013 (UTC)[reply]

Sorry I made mistake. Actually I should have said fruit juice instead of fruit. The main benefits of eating fruits are fiber, vitamins and minerals. Anyway here are two interesting pieces: [5] and [6]. --PlanetEditor (talk) 16:28, 14 February 2013 (UTC)[reply]

Still not right. From Fruit juice#Health effects:

For example, orange juice is rich in vitamin C, folic acid, potassium, is an excellent source of bioavailable antioxidant phytochemicals[9] and significantly improves blood lipid profiles in people affected with hypercholesterolemia.[10] Prune juice is associated with a digestive health benefit. Cranberry juice has long been known to help prevent or even treat bladder infections, and it is now known that a substance in cranberries prevents bacteria from binding to the bladder.[11]....fruit juices are actually known for their ability to raise serum antioxidant capacity and even offset the oxidative stress and inflammation normally caused by high-fat and high-sugar meals.[13]....fruit juice intake has been consistently associated with reduced risk of many cancer types,[15][16][17][18][19][20][21][22] might be protective against stroke[23] and delay the onset of Alzheimer's disease.[24]....

Duoduoduo (talk) 22:04, 14 February 2013 (UTC)[reply]

Olive oil is low in saturated fat (commonly called "bad fat" linked with coronary heart disease), high is MUFA (good fat), and moderate in PUFA (another fat which is both "good" and "bad"). A high PUFA consumption is detrimental to health, and there have been a lot of noise made about the effects of saturated fat. So olive oil is an ideal choice for cooking and salad dressing, it will give you the good fat MUFA, and limit your saturated fat consumption. Another oil that you can chose is canola oil. --PlanetEditor (talk) 13:54, 13 February 2013 (UTC)[reply]

Antioxidants are essential. But a study shows excess intake of vitamin c can reduce the benefits of exercise. However in that study the volunteers took 1000 mg vit. C per day, which is a very high dose and well above the RDI. --PlanetEditor (talk) 14:02, 13 February 2013 (UTC)[reply]

KWh problem[edit]

I have a problem where a fridge has a COP of 1.4. A 20W light in the fridge is switched on when the fridge door is open which is for 31,317,000 seconds of the year. I require the energy consumption of the fridge (for the light bulb only so ignoring energy consumption to power fridge itself) in KWh/year. I know from my calculations that the energy the bulb requires in a year is 20x31,317,000 which is 626340000J. The energy the fridge can supply is 20/1.4 which is 14.29J. This would be per second I think. I'm lost from here because of the KWh/yr. I don't understand this unit and I don't know how to get the energy consumption of the fridge for the bulb in KWh/yr. Clover345 (talk) 16:42, 13 February 2013 (UTC)[reply]

Are you sure about this setup? Your time value is equal to the full number of seconds in a year, so you are assuming that the door is open all the time. Is that really what you want to do? Regardless of the answer, converting to Joules here does not help you. Basically your problem is to convert from Watt-seconds to Kilowatt-hours -- the "/yr" part simply indicates that you should do this on a one-year basis. Looie496 (talk) 16:55, 13 February 2013 (UTC)[reply]

I couldn't find the TLA "COP" in Wikipedia (unless you meant Coefficient of performance which doesn't apply to the light bulb), so I'm not sure where the 1.4 comes in. I agree with Looie496 that the joule isn't the simplest unit to use here, but, if you insist, then 20W is 20 joules per second, and one kWh is: 1000 (joules per second) times 60 (seconds in a minute) times 60 (minutes in an hour) ~~times 24 (hours in a day)~~ joules. Alternatively, if you look at the Kilowatt hour article you will see that one kWh is equivalent to 3.6 million joules. Leaving the fridge door open for a full year with the fridge switched on will waste a lot more energy than that used by the light bulb. Dbfirs 17:29, 13 February 2013 (UTC)[reply]

Leave out Dbfirs' last "times 24" or you'll be dealing in "kilowatt days" Rojomoke (talk) 17:41, 13 February 2013 (UTC)[reply]

Oops! Brain slipped out of gear! Dbfirs 20:58, 13 February 2013 (UTC)[reply]

Don't forget that the bulb dumps waste heat into the refrigerator - which it then has to remove - so the actual amount of energy consumed if the light inside fails to turn off when you shut the door is going to be at least twice what the bulb consumes...probably much more. SteveBaker (talk) 20:36, 13 February 2013 (UTC)[reply]

Your estimate is far too high. Typically it takes %25 of the input energy to cool that amount. So a 40 watt light will consume 10 watt in order to cool it. Maybe slightly more because the fridge is cold, but certainly not "twice what the bulb consumes". Ariel. (talk) 01:07, 14 February 2013 (UTC)[reply]

I think I recall this problem from my 'Physics 101' exam. -Which doesn't necessarily mean that I recall the answer. ;) ~:74.60.29.141 (talk) 21:09, 13 February 2013 (UTC)[reply]

COP (coeficient of performance) is the ratio of heat removed to electrical energy consumed and applies to any form of refrigeration - airconditioners, fridges, thermo-electric beer cooler, etc. To get the electricity consumed in kW.hr due to the 20 W light, you need to multipy 20 watts by 1 plus 1/COP, and then multiply by the total door open time in hours. You need to add 1 because the light draws power directly, as well as causing the refigeration to draw more power. However, the COP given by the OP is way too low. Typical kitchen fridge COP's will be in the range 3 to 4. Some very small units can be as low as 2. Wickwack 124.178.132.174 (talk) 00:17, 14 February 2013 (UTC)[reply]

If the fridge has a faulty door switch (so that the 20w bulb is always on), then the power consumed by the lamp plus fridge motor just because of the faulty switch will be 20 watts times (1 + 1/COP) as explained by Wickwack, but if the door is left open in a warm room, then the power used might be even greater, and the interior temperature is unlikely to be maintained. Dbfirs 08:21, 14 February 2013 (UTC)[reply]

Where can I find real video of the moon orbiting the Earth from perspective outside Moon's orbit?[edit]

A few years ago, I remember watching a video of the Moon orbiting the Earth from a perspective outside the Moon's orbit, but I can't seem to find it. This is actual footage, not an animation. I don't remember all the details, but obviously there can't be too many videos of the Moon orbiting the Earth from this perspective. The video was short, maybe a minute or two, and time-elapsed. I'm guessing the video was taken from a satalite orbiting the Sun, but I could be mistaken on that. Can anyone help me out here? A Quest For Knowledge (talk) 16:49, 13 February 2013 (UTC)[reply]

Was it this 2008 video of the transit of the Moon in front of Earth, as seen by the Deep Impact probe? TenOfAllTrades(talk) 17:05, 13 February 2013 (UTC)[reply]

For bonus points, I'll also throw in this small collection of still images taken by other missions. The Voyager image at the bottom of the page was the very first of its kind. TenOfAllTrades(talk) 17:11, 13 February 2013 (UTC)[reply]

@TenOfAllTrades: Yep, I'm pretty sure that was it. Thanks! A Quest For Knowledge (talk) 17:21, 13 February 2013 (UTC)[reply]

Coefficient of Performance[edit]

Are my calculations here correct?

My air con unit has a temp of 5C in its coils, and the temp outside is 25C, the rate of heat transfer from the coil to the refrigerant is 5000kj/hour, and the power input required is 1250 kj/hour.

I've calculated the Coeffecient of Performance as 5000/1250 = 4 and the maximum coefficient of performance if the system were reversible as 1/(298/278)-1 = 13.9.

I've also calculated what it's Coefficient of performance would be as a heater if I reversed the unit as 1/1-(278/298) = 14.9. This is the max Coefficient of Performance as a heater so in reality it would be 4(from the Coefficient of performance as a air con) + 1 =5. 1 is from 14.9 -13.9. Clover345 (talk) 17:51, 13 February 2013 (UTC)[reply]

I see nothing wrong with your math, except I don't know where you got the 298/278 numbers. For heating COP you want: (5000+1250)/1250 = 5. BTW this is a pretty efficient A/C, I don't believe any units of this size, and still this efficient are available on the market. (This efficiency is usually only available for much larger sizes than this.) Ariel. (talk) 18:30, 13 February 2013 (UTC)[reply]

Also "the rate of heat transfer from the coil to the refrigerant" - for a system like this you actually want the rate from inside air to outside air. There are two heat transfers in this system, so don't just calculate one of them. Ariel. (talk) 18:31, 13 February 2013 (UTC)[reply]

The 298/278 are the temps in kelvin. And can you elaborate on the second system I should calculate? Thanks. Clover345 (talk) 19:06, 13 February 2013 (UTC)[reply]

Heat transfer from the room to the cold coils, and from the hot coils to the outside air. If you are using temperature to do your calculations you have to do it twice (you started your question by mentioning temperatures). If you just look at net flow then both will be the same of course, except that the hot side also deals with waste heat. Ariel. (talk) 23:09, 13 February 2013 (UTC)[reply]

basic theoretical question (no application)[edit]

Hi,

I have a basic theoretical question that has no application. Is a glider, like a sailboat, able to "glide" against wind (when looking at ground coordinates, I mean). What are the theoretical constraints? What I mean is, theoretically if you are at an altitude, A, and have a glider of mass m and wing area w that is willing to lose y meters of height in order to go straight into the direction from which wind is coming from at a velocity V - will that be possible? Or, normally, will a glider be unable to perform this overall action. If it can perform the action overall (including via crisscrossing) what is the average theoretical limit of the speed it can gain (wrt to ground) in directly same direction wind is coming from? This is a point of curiosity only and has no intended applications at present, but is intended to help me understand basic ralationships. Thanks. 178.48.114.143 (talk) 18:41, 13 February 2013 (UTC)[reply]

No. A glider can (for a while) steer into the wind and make progress by losing speed and/or altitude - or by maintaining altitude in a rising air stream...but it can't "tack" into the wind like a sailing ship. To do that the sailing ship is using the resistance of the water against the flow of the air. A land-yacht does is using friction against the ground with its' wheels. The glider doesn't have anything to push against, so it can't do that. A glider that could fly up-wind would be a perpetual motion machine - and those don't work! SteveBaker (talk) 20:32, 13 February 2013 (UTC)[reply]

Could you or someone specify what "for a while" is theoretically, for different wind speeds, altitude a, mass m, wing area w, and so forth. Am I supposed to just take the potential energy that the glider has due to its altitude, and convert that into forward motion directly (i.e. in newtons)? i.e. I can theoretically give a glider as much forward thrust as it loses in kinetic energy from losing energy? In that case would I simply subtract the speed of the wind from that to see if it can (even theoretically) move forward with respect to ground when faced with that wind, losing altitude to do so? My suspicion is there is a limiting rate, thus for any combination of the above there is a wind you cannot fight for any amount of time as you just can't convert altitude to forward motion fast enough. I'd like to know the equation I can use to calculate this, if possible. This is meant to increase my theoretical understanding only. Thanks for any help. 178.48.114.143 (talk) 21:36, 13 February 2013 (UTC)[reply]

It's far from possible to answer your question using just mass, wing area "and so forth". The shape of the glider is critical - and it requires wind tunnel testing to know for sure what the glide ratio, drag coefficient, angle-of-attack-versus-lift curves and so forth are like.

The easiest way to think about flight through wind is to ignore the wind and instead, pretend that the ground is moving in the opposite direction and the air is stationary. As far as the glider is concerned, the ground doesn't even exist past take-off and landing! So do your math in the coordinate system of the air and then add in the wind vector at the end. This works great when the wind speed is constant - or varying very slowly...but in gusty or turbulent air, things get much more complicated - especially for sailplanes that have very flexible wings.

The art of flying gliders over long distances (and the world record is something like 1800 miles!) is in finding sources of naturally upwelling air such as:

Thermals created by some weather systems
The upwelling air over a large tarmac parking lot or a cornfield on a sunny day
Slope lift caused by wind blowing up a steep hillside

By spiralling around to stay within one of these upwelling airflows, you can gain altitude. Once you get high enough (or the air ceases to move upwards) - then you must push the nose of the glider downwards and trade the height that you've gained for more forward speed so that you can glide away towards the next thermal. By doing that expertly, you can (in principle) keep the glider in the air indefinitely - and fly against the wind. The trick is to find those upwelling airflows from tens of miles away with sufficient confidence to make it worth flying there to get another altitude boost. The ability to spot those things reliably is what make a great long-distance glider pilot - they do things like watching birds, cloud formations or dust whipped up by the wind - and just knowing where the thermals are likely to be. Having found one, staying inside the thermal is another tricky matter...especially because there is often down-moving air right next to the up-moving air! SteveBaker (talk) 15:09, 14 February 2013 (UTC)[reply]

Have you read Polar curve (aviation)? --catslash (talk) 22:39, 13 February 2013 (UTC)[reply]

If you want to increase your theoretical understanding, please start by reading our article on gliding flight. Looie496 (talk) 22:46, 13 February 2013 (UTC)[reply]

Could any engineer devise a toilet operation contingency plan for cruise-ships?[edit]

Seen this? http://www.cnn.com/2013/02/13/travel/cruise-ship-fire/index.html

Whenever I get on my first cruise ship, I would like to be reassured that the ship's sanitary systems have some kind of contingency plan so that if the main source of power fails, there will be some way to keep the toilets running anyhow; a fail-safe.

I wouldn't mind if the toilets even opened a "contingency valve" that releases the waste directly to the waters (but ONLY during such emergencies like the Carnival Triumph's) as that emergency would make the waste-release the lesser of our concerns.

But what is preventing that from happening? And what would it take to invent a contingency system that will keep a cruise ship's toilets working anyhow during this kind of emergency? How hard is it to invent, what would the cost be, how much extra $ would that be passed on to passengers in terms of ticket prices, and how many years off do you suppose such inventions are?

Remember that necessity is the mother of invention! There's very much a necessity for this happening lately! Thank you. --70.179.161.230 (talk) 19:28, 13 February 2013 (UTC)[reply]

Ships use vacuum toilets to keep pipe size and weight down and to assure operation when the ship is in motion. Buildings, which don't move, operate entirely by gravity, but need bigger pipes and more-or-less direct runs to a drain or sump, and aren't suitable for seagoing use on a large scale. I'm not sure what the pertinent maritime law is, but I doubt that it allows for an emergency sewage system on large vessels: they must operate under all circumstances. It seems to me that backup power is needed to assure that the vacuum system works: it apparently wasn't a priority in this case, or it failed or was damaged in the fire. Acroterion (talk) 19:33, 13 February 2013 (UTC)[reply]

The "pertinent maritime law" is the International Convention for the Prevention of Pollution From Ships (know as MARPOL 73/78), specifically its Annex IV - Sewage. Our article doesn't go into the details, but this IMO page does, and it states that untreated sewage may be regularly discharged overboard when the vessel is more than 12 nautical miles from the nearest land, and that properly treated (comminuted and disinfected) sewage may be discharged when more than 3 nautical miles from the nearest land, both while outside designated special areas. Here is the complete annex. Even this has the exception that the regulation does not apply to the discharge of sewage from a ship necessary for the purpose of securing the safety of a ship and those on board or saving life at sea, or resulting from damage to a ship or its equipment if all reasonable precautions have been taken before and after the occurrence of the damage, for the purpose of preventing or minimizing the discharge. -- ToE 07:25, 15 February 2013 (UTC) To the OP: Hello Manhattan, Kansas![reply]

Buckets, gunwale, lots of wet wipes... passengers might raise a ruckus, but it's simple, it works and it is cheap. And for a short term emergency solution it's good enough. WegianWarrior (talk) 20:24, 13 February 2013 (UTC)[reply]

The solution is to make sure you don't totally lose power - and that requires generators and fuel for those generators to be stored someplace OTHER than where the main generators and their fuel is stored. If it hadn't been the toilets backing up - or the food running out - or the A/C not working, there would have been something else. A ship like this simply can't function without adequate power...and a design that allows it to lose all power from a single point of failure (like a fire in the engine room) is a poor design. They needed to spend the money to keep a couple of days of reserve power and not on some complicated solution for zero-powered toilets. That sounds tough to do though. SteveBaker (talk) 20:54, 13 February 2013 (UTC)[reply]

They could have a supply of Porta-John™ folding portable toilets: "Ideal for special events, emergencies, disaster relief and military use".^[9] (They can be shipped/stored 12 per pallet)^[10] ~E:[edit]74.60.29.141 (talk) 22:21, 13 February 2013 (UTC)[reply]

This is about the sixth total power outage on such a cruise ship in recent years. The owners seem to register the ships in countries which do not require publishing the results of root-cause investigations, so it is hard to find out why having two separate engine rooms does not provide the expected redundancy when one diesel generator catches fire. Surely a fire in one engine room does not lead to spraying water or foam in both rooms. If it spreads to the 6600 volt switchboard and knocks it out, that might be an explanation. Redundant switchboard design (ring buses) at increased cost might be an option. Complete loss of propulsion in a storm or with the wind driving the ship towards the rocks might doom the 4000 aboard in some future failure. If i somehow get the money for a cruise, I'll go somewhere and stay in nice hotels instead. Edison (talk) 01:01, 14 February 2013 (UTC)[reply]

The usual procedure while fishing is to squat over an empty bait bucket and toss it over the side, or just aim over the side if you're equipped for that. Unless a bucket's unsuitable for Hyacinth?— Preceding unsigned comment added by Medeis (talk • contribs) 18:06, 13 February 2013 (UTC)[reply]

If Hyacinth was put in charge of the bucket brigade she would perform... her duty, spectacularly I am sure, although she will be repeatedly wishing she could be providing fancier chamber pots for the more "prestigious" guests. :-) --Modocc (talk) 01:12, 14 February 2013 (UTC)[reply]

They don't seem to have much of an emergency plan, do they ? I can think of many ways to improve things:

1) Bring ships alongside and connect cables to provide electricity.

2) Offload passengers onto other ships.

3) Deliver many Port-a-Potties.

4) During construction, they could have covered the sides and top of the ship with solar panels, which should hopefully be enough to operate the toilets during daylight, at least. When everything is working, they could also supply extra power. StuRat (talk) 00:51, 14 February 2013 (UTC)[reply]

There isn't really a "top" available to cover - that's the deck, and people walk on it. The sides would get hit with saltwater which would destroy the solar panel in short order. Ariel. (talk) 01:31, 14 February 2013 (UTC)[reply]

Put a clear lacquer over them, both to protect from salt-water and footsteps. The panels would need to be cleaned regularly, but they clean those areas anyway. StuRat (talk) 01:39, 14 February 2013 (UTC)[reply]

I wonder how much ~~tidal power~~ wave energy a cruise ship could extract from waves lapping up against it (without spending too much on the backup system that is). Wnt (talk) 01:35, 14 February 2013 (UTC)[reply]

Good point! --70.179.161.230 (talk) 06:01, 14 February 2013 (UTC)[reply]

It's a customer problem, not an engineering problem. Any reasonably competent electrical engineer can design a redundant power system that makes a ship-wide power outage about as likely as the ship being hit by a meteor. The customers have not demanded that, but they have demanded lower ticket prices, and so they are getting what they want. --Guy Macon (talk) 01:36, 14 February 2013 (UTC)[reply]

I wonder if the customers can sue for pain and suffering ? Then again, if they were sailing to a third-world nation, how wonderful to have a taste of life in the third world for themselves: no food, no light, no electricity, no running water, and sewage everywhere ! StuRat (talk) 01:43, 14 February 2013 (UTC)[reply]

Well, remember that the cruise ship also flies the flag of some third-world nation or the like, so suing them requires a long stay in that country. Plus the Athens Convention limits liability to $80,000. [11] Wnt (talk) 15:42, 14 February 2013 (UTC)[reply]

I'm not sure I'd call Bahamas a third-world nation, given their per-capita GDP, literacy rate, life expectancy, and such. And it's not an unpleasant place to stay at all. (And just $250 or so round-trip from Miami.) --jpgordon^{::==( o )} 21:54, 14 February 2013 (UTC)[reply]

I don't see it as a customer problem. You can't expect tourists & holidaymakers, most of whom are probably making a one-time trip, to understand anything about what it takes to run a ship properly. I don't know anything about that particular ship and what happened to it. But as a professional Engineer who has investigated incidents elsewhere, and performed maintenance audits, I can say that these sorts of problems are almost NEVER due to deficiencies in design. It is sufficiently easy, and quite the norm, in ships, hospitals, and other large projects where life must be protected, to design and build in redundancy in power generation and electrical distribution. And, if the operating Engineers and maintenance staff are left alone to do their jobs, mostly they will maintain that designed in redundancy, becaue hey understand its' importance. The problem arises with non-technical management at the top - business managers, promoted matrons, and the like in hospitals, captains and admin officers in ships, who came up from the business or navigation career path (or, in one case I know about, the captain was a complete fool who passed exams and got promoted up out of the ship's security team!) Upon learning that a) the ship/hospital/whatever has a dual power distribution, and b) one of the duals has failed, but the ship/hospital can still function with only one, they tell the engineers "don't fix it yet - the budget is tight / we need to leave port / whatever.) And then the one remaining system fails. Ratbone 121.221.231.100 (talk) 02:24, 14 February 2013 (UTC)[reply]

That assumes that the managers in charge of running the ship are willing to sacrifice redundancy for increased profit but the managers in charge of building the ship are not. Do you have a theory as to why this might be so? We can test your theory; somewhere there is information about whether that ship had no redundant generators on the other end of the ship that were not maintained or whether they weren't built in the first place. I am betting on the latter. Let's check to see what our Carnival Triumph page says. Port of registry: Bahamas. That wasn't decided by operations managers. Let's see what Google has: http://www.usatoday.com/story/cruiselog/2013/02/12/carnival-triumph-cruise-ship-fire-stranding/1914191/ "By law, they do have emergency back-up systems, but only enough to operate critical functions" So clearly they could have built-in enough capacity to run the toilets, and maybe the refrigerators in the kitchens. But it would have cost money to build that in, money for the fuel to lug around the extra weight, and money would be lost by having fewer cabins. So they didn't. --Guy Macon (talk) 05:03, 14 February 2013 (UTC)[reply]

Your newspaper article has a limitation in that it doesn't define what "critical function" is. It has been stated (the Wiki article has this) that an onboard emergency generator was operational, but some other fault or deficiency meant that it could not run the sewage system for half the ship. You make a good point on builder managers vs operator managers. My theory, based on experience, is this: Builder/construction managers employ professional engineers with appropriate professional (university) qualifications and professional body accreditation. It is a very brave manager who overrules a professional engineer on safety or reliability. For me personally, every time I dug my heals in on safety and reliability, the manager has backed off. They weren't happy but they backed off. And such engineers are very mobile - when the thing's finished they move on. In contrast, operational guys are more dependent on their manager for a job, they don't have the same professional qualifications and acreditation. So while they DO know their job, they are more easily dictated to. Safety Of Life At Sea (SOLAS - see Wiki article) requirements are detailed and very high. Regardless of where a ship is registered, it will have to meet requirements for registration and it WILL have to meet requirements at commisioning or it cannot be insured. But once at sea, slack and dumb crew leadership can let all manner of things go downhill. Ratbone 120.145.48.96 (talk) 06:32, 14 February 2013 (UTC)[reply]

We have a hotel chain in the US which takes slack maintenance to the extreme, Econo Lodge. A new Econo Lodge link is perfectly fine, but, as things break, they don't bother repairing them. This seems to be the plan from the start, because it's not designed to permit maintenance, such as having pipes and wires inside solid concrete walls. They just close off non-functional rooms until so many become non-functional that they can't make a profit any more, then they tear the whole mess down and start over. They appear to have perfected the concept of the disposable motel. StuRat (talk) 06:48, 14 February 2013 (UTC) [reply]

This looks off topic, besides it sounds like a "cash flow problem" to me, but please, quit these hijinks. Wnt (talk) 04:36, 15 February 2013 (UTC)[reply]

That's the approach I'm using with my current car. -- Jack of Oz ^[Talk] 07:53, 14 February 2013 (UTC) [reply]

Err, StuRat! Having pipes and wires inside solid concrete walls has been the normal way in most if not all countries for 70+ years. With pipes, you can pretty much always unblock them with plummer's "snakes", as inspection/access ports are required by plumming codes. The ones that can't be unblocked with snakes, well, the plumber just gets his electric jackhammer out - a few minutes and he's exposed and unblocked it, just neeed to trowel over some new concrete. With wiring, if it is installed per code, fuses and circuit breakers will prevent the actual wiring from failing. Whatever ideas the management have for constrction standards, any construction will still have to comply with legally enforced standards - in the USA the National Electrical Code (NEC) and whatever plumbing standards you have. It is quite normal for hotels at all levels of rating to close & seal rooms from time to time. Easy meaintenance is done by the hotel's own staff if any; with the more involved maintenance, except in season when bookings are high, it is more economic to acuumulate rooms with faults and then get a contractor in and do one big job and fix the lot, rather than have them come and go all the time. Is this another one of your joke posts or off the cuff nonsense posts? Wickwack 121.221.85.179 (talk) 08:22, 14 February 2013 (UTC)[reply]

Let's see some sources proving that solid concrete interior walls are the normal construction method in the US, where this chain is located. Also, you seem to be neglecting the accumulation of scale in the pipes, meaning they eventually need to be replaced. And using a jackhammer in a motel with occupants is definitely out. StuRat (talk) 16:48, 14 February 2013 (UTC) [reply]

Please give a source for your claim. I'm not going to join the stupid edit war, but your comment naming a specific business is not appropriate unless you can actually back it up with some sources. --Onorem ♠Dil 01:10, 16 February 2013 (UTC)[reply]

I doubt if they would admit this strategy publicly. I suggest you stay in an old one, and see what condition it's in (failing that, check out the numerous one star reviews here, especially the one with pictures: [12]). Our article does say that the power can be cut off to each room individually, though, which does support the idea of them planning to shut down a good portion of the rooms, at some point. StuRat (talk) 01:21, 16 February 2013 (UTC) [reply]

A simple 'no' would've been fine. Please redact. --Onorem ♠Dil 01:39, 16 February 2013 (UTC)[reply]

Did you even bother to look at those pics ? No sign of maintenance being done there. StuRat (talk) 01:42, 16 February 2013 (UTC) [reply]

That still just adds up to a big pile of OR and doesn't belong here. There is no sign of maintenance in those pics, therefore "We have a hotel chain in the US which takes slack maintenance to the extreme, (Redacted) is perfectly fine, but, as things break, they don't bother repairing them...." and the rest of your unsourced and inappropriate commentary. It doesn't belong here. Please source your comment or remove the name of the business. --Onorem ♠Dil 01:48, 16 February 2013 (UTC)[reply]

It's just typical StuRat nonsense. The odd complaint from a few guests who might have had a shitty on or some agenda means nothing. He's again claimed that the ability to cut power to individual rooms is evidence of some sort of intent. But it is normal practice to have cicuit breakers or isolating switches for each room or suite in a hotel. Ratbone 124.178.182.98 (talk) 02:52, 16 February 2013 (UTC) [reply]

If it was typical, our article wouldn't have mentioned it, now would they ? That would be like saying "This motel chain has windows in every room." StuRat (talk) 17:35, 16 February 2013 (UTC) [reply]

Yes, it would be like saying every room has a window. It is like saying every room has a window. As to why the article mentioned it, who knows? Wikipedia articles vary in standard - this one is definitely not one of the best - it contains many statements not supported by any reference. It also says that management reduced maid workload by having box beds so the maids don't have to clean under the beds. Multitudes of motels, the cheaper hotels, and church-run youth hostels have done that for a very long time. The YMCA, where I used to live and work at, has done that at least 70 years. Wickwack 60.230.238.152 (talk) 02:45, 17 February 2013 (UTC) [reply]

As long as we're off-topic anyway — the business model suggested by Stu strikes me as very unlikely to be cost-effective, but I haven't actually run the numbers, so who knows. Assuming arguendo that it were cost-effective, I'm not sure what would be so terrible about it from a customer perspective; if they close the bad rooms as they fail, then you don't get stuck in one, unless you're the unlucky first customer on that day (which can happen to you in any hotel). --Trovatore (talk) 23:06, 17 February 2013 (UTC) [reply]

Yes, as we are off topic:- As is typical with Stu, he's not entirely wrong. Stu is a pretty smart guy, but he just loves to post without checking - possibly to see what we do about it (ie trolling). It is actually common practice in hotels to close rooms with problems rather than fix them right away. Most of the year, most hotels can't get full occupancy. Where he is most likely wrong is in assuming this particular chain, which I am not familiar with, never fixes anything ever. What some hotels do is just let the number of rooms closed due to faults accumulate, and then, often enough to satisfy occupancy rate needs, get them all fixed in one go. When I was a young lad, I worked for and lived at a 14-storey low cost but very nice hotel owned by the YMCA - they did the same thing, getting all crook rooms fixed up just before tourist season, when they needed all the rooms. Consider getting a plumber out to fix one blocked toilet (common in hotels as some guests use far too much paper and/or put tissues in the loo). In my city, a typical plummer charge is $180 callout plus $55 per 15 minutes on site. Unblocking a toilet might take him 10 minutes, and he'll use the remaining 5 to write up the paperwork, so total change is $235. Now, say the hotel has called a plummer to unblock 20 toilets. At least 6 or so will have pretty much come good anyway if just left for a few days and the paper & poo dissolves, and only need 2 minutes. The charge will be $180 + (14 x 10 minutes + 6 x 2 minutes + 5 minutes) x $55/15 = $711.67. If each toilet was fixed one by one when it failed, the total would have been $4700. The other aspects Stu mentioned, having wiring and pipes buried in the concrete or brick walls, and being able to isolate electrical service to each room, is standard practice in hotels as Ratbone said, and box beds not at all unusual. Wickwack 120.145.59.43 (talk) 23:59, 17 February 2013 (UTC) [reply]

Even if they added one, I'm not sure their emergency toilet will have a bidet, so will you be satisfied? Nil Einne (talk) 07:15, 14 February 2013 (UTC)[reply]