Wikipedia:Reference desk/Archives/Science/2016 May 11

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May 11

Lightning strike

In a thunderstorm, is it (relatively) safe to be outside in an area with lots of high-rise buildings close together? Because intuitively, it follows that these could act as lightning rods, but how effective is it in practice? 2601:646:8E01:515D:F88D:DE34:7772:8E5B (talk) 01:24, 11 May 2016 (UTC)

I don't know, maybe? I think it suffices to say you shouldn't rely on high-rises protecting you, as lightning can do all kinds of wacky things depending on what path(s) it wants to take. People have been struck by lightning inside buildings through openings (windows, doors, chimneys). Also the current can travel along the ground, which means that even if the bolt "misses" you, you can still get a nasty shock if you're nearby. --71.110.8.102 (talk) 04:51, 11 May 2016 (UTC)

Safe regions are discussed in Lightning Rod#Lightning protection system design. --catslash (talk) 09:19, 11 May 2016 (UTC)

It should be relatively safe inside such buildings; their metallic skeletons would likely act as a Faraday cage. --Jayron32 11:04, 11 May 2016 (UTC)

That assumes the electricity can actually get to the frame, which would mean going through cement/concrete, which is a good electrical insulator (it needs to be, or it will corrode, see electrical resistivity measurement of concrete). StuRat (talk) 17:40, 11 May 2016 (UTC)

The lightning just made it through a mile and a half of air. A few centimeters of cement isn't going to do jack. The lightning more than exceeds the breakdown voltage of the cement, meaning it tears through it like it isn't there. --Jayron32 20:11, 11 May 2016 (UTC)

Do you have any source to support it getting to the frame ? Otherwise I suspect it will take the path of least resistance, which, if it lacks a lightning rod, may well be the (presumably) wet side of the building, as rainwater with some contaminates in it makes a good conductor. There's also the rain gutter system, which tends to be internal in large buildings as opposed to down the side, but water filled metal pipes should make an excellent conductor, in any case, right down to the ground. StuRat (talk) 13:25, 12 May 2016 (UTC)

"Any steel-frame structure, such as a skyscraper, is a lightning rod in itself. A lightning bolt striking it is automatically carried harmlessly to the ground by the steel." --Jayron32 14:06, 12 May 2016 (UTC)

How many percents of proteins and fats are taken by our bodies?

How many percents of proteins and fats are taken by our bodies? For example if it's written on some food that it contains 20g proteins and 5g fats, does it say that our body take all this proteins and fats and store them or use them? or it says that this is the maximum value that the body can take from it but in fact it can be less significantly (of course I'm not talking about exceptions or pathological cases, but generally)93.126.95.68 (talk) 06:49, 11 May 2016 (UTC)

The values shown in the nutritional content show the amount that actually exists in the food. The ability of the human body to absorb nutrients depends on the specific nutrient in question, the makeup of the food (most especially the fiber content, with higher amounts of fiber impeding absorption), and miscellaneous personal factors. It's generally estimated the human body or its microbiota consumes about 95% of the nutrients you eat [1]. What I haven't been able to find is an estimate of how many calories are burned by your microbiota instead of being absorbed by your own body. Someguy1221 (talk) 10:13, 11 May 2016 (UTC)

So that ref goes (eventually) to here [2], presenting a research bulletin of the USDA from 1899. If you download the PDF, there is a big warning saying that it is an archived document, and that we should "not assume content reflects current scientific knowledge". Now, I don't necessarily think that 95% figure has changed much, but we probably can and should find a more contemporary ref :) SemanticMantis (talk) 14:07, 11 May 2016 (UTC)

The efficiency may depend on how much you eat. If you eat excess protein, your body dumps amino acids (broken down proteins) out in urine. Not sure what happens if you eat excess fats. StuRat (talk) 17:37, 11 May 2016 (UTC)

• Two points. First, if all the microbiota in your body were to cease to exist, you'd suddenly find yourself cadaverous, unable to engage in the symbiotic metabolic biome they provided, and would be like a reef that had lost all its bilateria. In other words, you are your own human framework, with all its inhabitants.

• As for fat, look up Olestra. I'm not sure whether there's a means of extruding fat per say, fat metabolism will help her. And you could always have a series of fatty meals, then boil the turds to see what floats to the top. μηδείς (talk) 04:31, 12 May 2016 (UTC)

Don't ever invite me over to dinner ! :-) StuRat (talk) 13:21, 12 May 2016 (UTC)

To follow up on your first point there, it's worth noting that the human mental condition is believed to be influenced, even to pathological degree, by substances produced by microbiota. [3] So just as a person's frame of mind is affected not just by neurons and glia but also by hormones from various far-flung organs, it is affected by the bacteria that are part of them; it is not really the human soul but the human-and-microbes' soul, so to speak. Wnt (talk) 21:43, 12 May 2016 (UTC)

Loud as a refrigerator

Our Wind power#Environmental effects says, "Wind turbines generate some noise. At a residential distance of 300 metres (980 ft) this may be around 45 dB, which is slightly louder than a refrigerator." Louder than a refrigerator at what distance? Is there a standard distance at which the loudness of a refrigerator is measured? Here is the reference for that statement. It gives db(A) values for various machinery, but with no indication of how close to those items the values apply. -- ToE 18:58, 11 May 2016 (UTC)

I can't think of a science more habitually dishonest than the estimation of noise. Even computer science, whose practitioners each year become more beholden to large corporations, still is not so bad as "scientific" statements about the planned noise of an industrial project.

The first lie is A-weighting itself. There are people who claim to be unable to hear noise below a certain frequency, whose perceptions influenced this curve; nonetheless, the infrasound has effects on them. Moreover, the curve details perception, but not penetration. Low frequency noise will come straight through the walls and pillows in a way that high frequencies won't, and there's no weighting for that. There is a different weighting used in Europe that is also bad, but not this bad. Another trick routinely used makes multiplication a suspect practice: instead of simply going by the decibel scale, which details the actual 10-fold differences in intensity, they instead have surveyed some people in a room at some time and gotten them to say that one sound "is about twice as loud" as the other, and then use this mistaken subjective estimation to claim that their company's sound is a lesser multiple of whatever than it is. So when they say "slightly", they could mean several-fold actual difference in sound level! And of course, as you noticed, the sound of a refrigerator does depend on the distance, and on the refrigerator, and when they don't tell you what parameters they used, it's fairly safe to assume the worst. And believe me, people who care about noise will go to great lengths to avoid the noise of a refrigerator! Wnt (talk) 20:39, 11 May 2016 (UTC)

Minor Sound volumes in the open are very dependent on wind direction and additionally 300 metres is very close to a wind generator. In Bavaria, Germany the minimal distanct to the closest settlement must be 10 times its height including the wings but atleast 2000 metres. Strangely this grafic on your source only reaches till 500 metres. Also the volume seems to high at the start. I doubt you would have any trouble talking to someone next to you even on top of one of these turbines but you will shurely have that next to an lawnmower that is used as comparrison in this grafic. That seems completely exaggerated. --Kharon (talk) 04:52, 12 May 2016 (UTC)

Norse pineapples

Jeopardy! just claimed that the Norse gods drank pineapple mead. Pineapple notes that the plant is native to South America and that Columbus, 1493, was responsible for first taking it to the Old World. Is or was "pineapple" also used to refer to an Old World plant or other substance? The article also notes that the term was previously used as a reference to pine cones, but I can't imagine creating an alcoholic beverage from pine tar or anything else present in pine cones. Nyttend (talk) 23:52, 11 May 2016 (UTC)

The question does not have to be parsed "the Norse Gods drank pineapple mead", and in fact does not state that. The statement instead means "I drank the pineapple type of this drink, which the Norse Gods also drank." Pineapple mead exists. Norse Gods Drank mead. It only states those facts, both of which are true. It does not say the Norse Gods drank pineapple mead. --Jayron32 00:21, 12 May 2016 (UTC)

• Alex Trebek, announcing a scoring correction on the question, did say explicitly that the Norse gods drank pineapple mead. Presumably the judges actually ruled on the basis that Jay describes, but Alex misinterpreted. --69.159.60.83 (talk) 07:56, 13 May 2016 (UTC)

Yes, the problem was with the phrasing. I thought of the answer "pineapple ambrosia", since ambrosia is the "food or drink of the (Greek) gods", and there is a pineapple version of it (although that's a food, not a drink). Still, that seems to satisfy the Q: "Drinks in the Fridge”: "I didn’t bring in pineapple juice but the pineapple type of this godly drink." The "not juice" part of the clue made me think it was a non-liquid with the same name as a godly drink, but with solid pineapple, hence my guess.StuRat (talk) 12:57, 12 May 2016 (UTC)

With reference to the idea that you can't make an alcoholic drink using anything from a pine, bear in mind that Greek Retsina is a drink made using resin of the Aleppo Pine to flavour it. 81.132.106.10 (talk) 08:14, 12 May 2016 (UTC)

You can't? Gin contains juniper, order Pinales, which makes it broadly a "pine". --Jayron32 13:58, 12 May 2016 (UTC)

Also Pine Liqueur, Pine Beer, Fir Brandy. Alansplodge (talk) 16:29, 12 May 2016 (UTC)