Wikipedia:Reference desk/Archives/Science/2018 November 10

= November 10 =

Celery powder less harmful than curing salt
Is there any evidence that processed meat cured with celery powder is less likely to cause cancer than meat cured conventionally? What do scientific research studies show? — Preceding unsigned comment added by Mister Johnston (talk • contribs) 00:58, 10 November 2018 (UTC) PAGE ]]) 16:22, 12 November 2018 (UTC)
 * I don't think there's really any evidence that cured meat causes cancer. One could argue that it's the smoking that introduces carcinogens. But for sure, fer suure, the nitrites in celery powder are exactly the same as the nitrites in curing salts, and will have exactly the same risk. Abductive  (reasoning) 19:49, 10 November 2018 (UTC)
 * Not according to the IARC, which classifies cured meat as carcinogenic to humans. The sodium nitrite produces nitrosamines, which are carcinogenic. --47.146.63.87 (talk) 09:17, 11 November 2018 (UTC)
 * No, there is not. Celery contains nitrites, which is why it's used. As to why celery is used, at least in the U.S. it's because of a big fat loophole in FDA labeling standards. If you use celery juice/salt instead of curing salt, you can label your product as "all natural" and "nitrate/nitrite free", even though the celery product you added to it contains nitrites. This is because the FDA considers "celery salt" to be just that, "celery salt", not "nitrate". Then you can stick this on your packaging/advertising and get people to buy it over competitors' products because they think it's "better for you", when chemically there's no difference. It's illegal in the U.S. mass market to sell uncured and unfermented sausages, etc., for a very good reason, because they might kill you from botulism. But the poorly-educated public has come to view preservatives as "bad", because they're supposedly "unnatural", without stopping to consider why preservatives are used in the first place. Botulism is perfectly "natural", so it must be good for you, right? --47.146.63.87 (talk) 09:17, 11 November 2018 (UTC)
 * Actually, every such package I've seen in the U.S. always explicitly has fine print saying "nitrite/nitrate free except for that present naturally in celery..." or some such. That said, there is at least one noticeable distinction in that celery contains nitrate rather than nitrite.  Supposedly the two are interconvertible pretty freely, but I am not sure if that applies before they are cooked or eaten.  And I'm not sure how many of the carcinogens produced by nitrite are generated by chemical reaction within the meat during storage rather than after consumption.  Note I'm saying "not sure" literally, doesn't mean there is a difference either! Wnt (talk) 23:27, 11 November 2018 (UTC)
 * To follow up a bit, here's a paper that discusses some roles for nitrate supplementation in humans.  They were expecting somehow to reduce blood sugar but it had no effect on that.  I thought this demonstrated instantaneous conversion of nitrate to nitrite in the human liver, but  says that beetroot juice may or may not contain lots of nitrite, depending on whether bacteria are active, though industrially it is usually pasteurized lightly to prevent that, or keeping it cold slows it down.  The original paper credits their beetroot juice to "Beet It", a company whose website claims that nitrate can "only" be converted to nitrite by bacteria on the tongue, according to the Google blurb (I didn't find the statement when I went to the site, but it's repeated here).  Which to readers of the first papers is clearly bonkers, even if common sense failed them otherwise.  Bottom line: I don't know how much nitrite is present in food products made with these juices, and I don't think I'd believe the stats without seeing an analysis of the specific product in question. Wnt (talk) 15:39, 12 November 2018 (UTC)
 * If you believe that nitrates/nitrites are actually bad for you (the jury is still out on that, and your body produces large amounts of nitrates/nitrites by itself regardless of what you eat), than most "uncured" meats that use celery juice/extract actually have more nitrates/nitrites than traditionally cured meats. That's because a certain minimum amount of nitrates are needed to ensure that pathogens don't grow on the meat, but since celery juice/extract is a natural product whose concentration may vary from batch to batch, extra is added to make sure that the food is safe no matter how weak that particular batch of celery was. The USDA has a limit on how much artificial nitrite can be added to food, but there is no such limit for celery powder. It's also a bit worse than that, as food with artificial nitrites is required to have vitamin C or E added to it to help prevent the nitrites from forming nitrosamines, but there is no such requirement for foods containing celery extract. To respond to Wnt's point, there's not really a meaningful distinction between artificial nitrites and the nitrates in celery, as the celery powder/extract is usually treated with bacteria to convert the nitrates into nitrites (see ), and your saliva is pretty good at converting any remaining nitrates into nitrites. In any case, most of your dietary nitrates/nitrates come from vegetables, not cured meats, so it's not worth worrying about. --Ahecht ([[User talk:Ahecht|TALK

Ultrasonic Sound
Could an ultrasonic sound explode human heads or cause weather problems, say one of 240dB-1000dB? déhanchements (talk) 16:26, 10 November 2018 (UTC)
 * I don't know, but I presume you've already read Sonic weapon. As documented there, "Studies have found that exposure to high intensity ultrasound at frequencies from 700 kHz to 3.6 MHz can cause lung and intestinal damage in mice . . . Tests performed on mice show the threshold for both lung and liver damage occurs at about 184 dB", so hugely larger energies (its a logarithmic scale, remember), are bound to cause grosser (in both senses) injuries to a human body. The range of 240dB-1000dB you quote, starts at the loudness of atomic bombs ("240-280 dB", according to a Quora answer and "A nuclear bomb. Decibel meters set 250 feet away from test sites peaked at 210 decibels. The sound alone is enough to kill a human being, so if the bomb doesn't kill you, the noise will" from the same set of answers), so I'm wondering what your envisioned source of your hypothetical sound is.
 * As for weather "problems" (as opposed to "detectable effects"), Effects of nuclear explosions (where "blast" might be roughly equated to sound) may be of some relevance (since it's dealing with the sort of energies implied by your "240dB-1000dB").
 * Overall, your question presumes energies which only governments (or natural forces) have the means to deploy, so some of those knowledgeable in the area might be constrained in what they can say. Others, however, might wish to present at least abstract calculations (and will be better qualified than I to do so). {The poster formerly known as 87.81.230.195} 2.218.14.42 (talk) 17:20, 10 November 2018 (UTC)
 * Re the link to "sonic weapon" this may have been an accident.  See . 86.157.229.93 (talk) 17:49, 10 November 2018 (UTC)
 * I'm wondering what your envisioned source of your hypothetical sound is. Hypothetically, the source of this sound is the Spirit of Katavi national park. déhanchements (talk) 19:59, 10 November 2018 (UTC)
 * The sonic capabilities of spirits of place are largely unexplored by conventional science, so your attribution of extensive capital disruption to one would be difficult to refute; I know its not something I'd be inclined to investigate at Chanctonbury Ring after dark! {The poster formerly known as 87.81.230.195} 2.218.14.42 (talk) 22:23, 10 November 2018 (UTC)
 * Katavi national park in western Tanzania is named after the legendary hunter Katavi whose spirit is believed to possess a Tamarind tree and where the locals go begging for blessings. Either a constant loud sound (85 dB(A) or above) or a one-time extremely loud sound (120 dB(A) or above) can cause permanent deafness but safari organizers are your source of reassurance if you are concerned this might occur. DroneB (talk) 00:19, 11 November 2018 (UTC)
 * Unless I have a wrong factoid buzzing around, it is not even possible for sound (in air) to reach 1000 dB. Strictly speaking, 1000 dB is a ratio, and doesn't mean anything without a reference value, but for the usual one used for sound intensity level, 1000 dBA or 1000 dB (SIL) is not a possible value, because air cannot carry that much power flux as sound.  Above some much lower value (maybe around 190 dBA?  can someone find it?) the mathematics of pressure waves in air breaks down, and you can have a shockwave, but not "sound".  1000 dB would be a ratio of a googol, so not even shockwaves are a sensible model &mdash; you'd have to start talking about black holes forming from that much energy all in one place. --Trovatore (talk) 23:20, 10 November 2018 (UTC)
 * Let's pretend I said 240dB-280dB, about that comment up there that mentions 1000dB, yeah...it doesn't exist. And thank you DroneB, I can finally rest easy. déhanchements (talk) 02:10, 11 November 2018 (UTC)
 * Sound pressure level suggests 194 dB peak or 191 dB SPL for 1 ATM although the value in the table is disputed. There's some discussion in the talk post. (I don't mean the most recent post but back in 2008.) Nil Einne (talk) 09:26, 11 November 2018 (UTC)
 * Thanks, Nil. --Trovatore (talk) 01:21, 12 November 2018 (UTC)


 * Audible and inaudible sound waves at these exceptional levels correspond to extraordinarily energetic pressure fronts - explosions. After a certain point, it is not meaningful to measure the "sound" using the units of decibels.  Such very energetic wave-fronts are measured using units of pressure, duration, and total energy or energy-flux.
 * The article on blast-induced barotrauma is informative. There are profound physiological and psychological effects for people who are exposed to such explosive energy.
 * Here's a fun pamphlet I pulled out of my emergency reference bookshelf that's also available online: the American College of Emergency Physicians' Pocket Guide to Bombing Injury Patterns, part of their care guidance website. This reading-material is not suitable for the faint-hearted.
 * Nimur (talk) 18:55, 15 November 2018 (UTC)

Energy
Im by no means a science major so correct me if im wrong. But i believe some physics law state that energy cannot be created from nothing and energy cannot be destroyed only transformed.

With that in mind, I have difficulty understanding Dams. As far as I can tell there is 0 difference for a river whether or not it runs through a dam on its way down. and that generates massive amount of energy for us. Where does this energy come from? Here I dont mean dynamo nor gravity. I mean where would all this massive energy have gone if the dam hadnt been there since it seems like nothing else in the area would have changed if the water hadnt gone through the dam first. — Preceding unsigned comment added by 91.101.26.175 (talk) 22:24, 10 November 2018 (UTC)
 * You are correct that energy can be transformed, it can exist as Potential energy or Kinetic energy. Examples of things that have potential energy are a book on a shelf, a stone on a mountain, an unused AA battery or water that has accumulated upstream of a Dam. Examples of kinetic energy are the mechanical movements of any machine that does physical work, sound vibration, fluid turbulence and heat. Potential energies readily transform to kinetic energy. Examples of that transformation are the sounds of the book or the stone falling, or the heating of a lamp filament by the battery in a Flashlight. Virtually all potential energy eventually converts to the kinetic energy of heat. That happens constantly to the potential energy of most rainfall. Humans manage to capture some of rainfall's energy in dams equipped to generate Hydroelectricity which is kinetic energy in a useful and saleable form that consumers can use to drive electric motors, heat their homes and power the Internet computer that brings you Wikipedia. DroneB (talk) 23:54, 10 November 2018 (UTC)
 * See Energy, which uses dams as an example of transforming energy. Mikenorton (talk) 00:02, 11 November 2018 (UTC)
 * Are you saying energy can transfer between potential and kinetic energy? How do you differentiate between a book sitting on a shelf with potential energy, and 0 potential? 67.175.224.138 (talk) 04:13, 11 November 2018 (UTC).
 * Yes that's correct, PE and KE can be exchanged. PE is measured relative to something else, one datum that could be used is the height of the bookshelf, or the surface of the Earth, or the centre of the earth, or far out beyond the solar system. They are all useful in certain circumstances. Greglocock (talk) 05:23, 11 November 2018 (UTC)

Both of you are completely missing the point of my question. Im not asking how a dam works. — Preceding unsigned comment added by 91.101.26.175 (talk) 01:27, 11 November 2018 (UTC)
 * Without a dam, the water would still fall somewhere and convert potential energy to kinetic energy. Most of the kinetic energy would quickly be converted to heat when obstacles or friction slow down the water. PrimeHunter (talk) 01:44, 11 November 2018 (UTC)
 * I would note that most modern hydroelectric dams tends to be massive constructions which can significantly affect the river they're built on hence why they can cause concern to environmentalists and also often those concerned about the people downstream. This discussion [//www.researchgate.net/post/Do_dams_built_solely_for_electricity_generation_affect_the_river_flow_velocity] and this source aren't the best sources but I think they do illustrate the larger point namely it's probably not simple to compare the situation before the dam and after the dam. Nil Einne (talk) 05:09, 11 November 2018 (UTC)
 * …where would all this massive energy have gone if the dam hadnt been there… It would have produced turbulence in the body of water, and friction with the earth. Any river canyon will show you the power of erosion generated by moving water. A dam stops that from happening by harvesting the energy. This can be an environmental problem, because a dam stops sediment from being carried downstream. For instance, the Aswan Dam has stopped the flooding of the Nile, which means farming along the Nile is now mostly dependent on chemical fertilizers and manmade irrigation, and the Nile delta is eroding away (as it's not being replenished by new sediment). --47.146.63.87 (talk) 09:03, 11 November 2018 (UTC)
 * All this is really chickenfeed compared to the fact that the power of the tides is changing the dynamics of the earth-moon system so that both bodies will eventually turn the same face to each other and the day and the month will both be 47 days long. 86.129.48.146 (talk) 11:34, 11 November 2018 (UTC)
 * And that pales into insignificance compared to the effects of our sun becoming a red giant well before that happens, according to our article. Mikenorton (talk) 13:46, 11 November 2018 (UTC)
 * ...which is why tidal power stations do exist and generate lots of power, even though they need much larger constructions than dams for the same power (quick-and-dirty summary: a mountain dam can harness water falling hundreds of meters, while tidal stations are limited to the amplitude of the tide, so the efficiency of the latter is lower). Tigraan Click here to contact me 10:21, 12 November 2018 (UTC)