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June 21

Please Help me find a botanical term and an existing page

Originally published in Teahouse (https://en.wikipedia.org/wiki/Wikipedia:Teahouse#Please_Help_me_find_a_botanical_term_and_an_existing_page) and I was guided to reference desk.

There is a terminology for when due to secondary growth a tree engulfs surrounding foreign objects . But I forgot the term and can't recall it back. There was an Wikipedia page about the term; which contained an image of a tree engulfing a barbed wire fence; upto best of my recall. (The image was from side view, and not from oblique view). Today I searched a lot of page; but could not find the page. Please help me to find the term and the page. Thanks in advance.

If I've asked the question in an inappropriate location or formatting then please do necessary guide/correction.

RIT RAJARSHI (talk) 04:38, 21 June 2018 (UTC)

• This is the right place, but I haven't found it yet. In the mean time, look at these: [[1]]. -Arch dude (talk) 05:08, 21 June 2018 (UTC)

That site asks at one point: "Is it possible there are items entirely consumed by trees that we don't know about?" I can confirm from personal experience (yeah, OR) that this is so. About 5 months ago I had a tree felled at the bottom of my garden which had grown too large (approaching a yard/metre thick at the bole) for its surroundings. The fellers discovered that it had entirely engulfed at least one metal fence post that had originally marked the garden boundary – they broke some chainsaw teeth when they unexpectedly hit the metal. Outside of the tree so few remnants of the fence remained that I (resident 27 years) had no idea it had once been there. {The poster formerly known as 87.81.230.195} 2.125.75.224 (talk) 10:44, 21 June 2018 (UTC)

I've found a few words, but none that are quite as specific or correct for "engulfment of foreign object". For example, burl (found where this question was asked at Talk:Tree archives and did not receive an answer), engulfment, inosculation, espalier, pooktre, edaphoecotropism. DMacks (talk) 05:18, 21 June 2018 (UTC)

There is such an image here but it doesn't seem to be used in any other articles.--Shantavira|^{feed me} 14:50, 21 June 2018 (UTC)

Plenty more pictures at commons:Category:Ingrown things in trees. DuncanHill (talk) 14:56, 21 June 2018 (UTC)

Spiders looking like ants

I've heard some spiders and other bugs appear like ants so they can sneak around among them and then eat them. That's right, isn't it? I've actually seen some bugs like that.

So, if ants cannot see well, why is looking like an ant so important? Anna Frodesiak (talk) 06:58, 21 June 2018 (UTC)

• Ant mimicry#Spiders says there are over 300 species of spider that have evolved Batesian mimicry of (or for?) ants. Just because ants can't see well doesn't mean that they can't recognize a typical spider shape. Abductive (reasoning) 07:08, 21 June 2018 (UTC)

• Batesian mimicry seems to be more about evolving to protect yourself not infiltrating other species communities. Ants rely very heavily on pheromones for communication (as stated in Ant) It would seem unlikely that looking like an ant but not smelling like an ant would be a successful strategy. And remember there are hundreds of ant species and most of these do not rub along too well together. So the answer to the original question is - no, that's not right. Richard Avery (talk) 07:47, 21 June 2018 (UTC)

• So, you think maybe the article is (partly) wrong? Abductive (reasoning) 16:03, 22 June 2018 (UTC)

In the case of the Large blue butterfly, the caterpillars are mimicking the ant larvae rather than the adult ants, but this broadly fits your scenario. The first article Richard Avery linked says, in the lede: "Some arthropods mimic ants to escape predation (protective mimicry), while others mimic ants anatomically and behaviourally to hunt ants (aggressive mimicry)" [my italics], and cites a paper. In all such cases physical resemblance will be necessary but not sufficient – the mimics will have to smell and move similarly to the ants as well, which means they will have to be mimicking a specific ant species and perhaps even a specific colony population. {The poster formerly known as 87.81.230.195} 2.125.75.224 (talk) 11:03, 21 June 2018 (UTC)

That makes sense. Thank you for clearing that up. And thank you for taking the time. It is appreciated. Anna Frodesiak (talk) 19:43, 21 June 2018 (UTC)

Mandatory swim caps

Is the mandatory swim cap thing baloney? So what if hair gets into filters? Isn't that what filters are for? Anna Frodesiak (talk) 06:58, 21 June 2018 (UTC)

Where is this rule in place. It's not in my little corner of the world - Australia. HiLo48 (talk) 07:16, 21 June 2018 (UTC)

The idea would be to prevent too much hair from getting in the filter and clogging things. ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:47, 21 June 2018 (UTC)

This is probably a health and safety issue [2], [3], [4]. In one case, a young woman was only saved when a bystander who had been in the bar the previous evening when a huge knife was delivered for cutting ice cubes rushed to get it. He handed it to the father (who had been attempting to cut her loose with a penknife) and with one slice she was free. 86.132.186.246 (talk) 10:35, 21 June 2018 (UTC)

It's also quite unpleasant while swimming to suddenly get a faceful of floating hair that has been shed by others and has then clumped together. I myself tend to gag if I unexpectedly get one of my own hairs in my mouth. {The poster formerly known as 87.81.230.195} 2.125.75.224 (talk) 11:17, 21 June 2018 (UTC)

Thank you all. Good points. Anna Frodesiak (talk) 19:43, 21 June 2018 (UTC)

@Anna Frodesiak: Having worked extensively with swimming pool filtration in my younger days, I'll say that pool filters are best at removing particulates (dirt, bugs, leaves, and other solid materials). Hair, on the other hand, isn't friendly. It's like trying to suck a string through a pump. What gets through the first stage basket gets tangled around the pump impeller and shaft, and accumulates. Short hair doesn't present a problem. But long hair (or thread or string) doesn't just get caught in the first stage basket or the final stage filter, it gets caught in the machinery. And if there's enough of it, the only way to get it out is to take apart the machinery, which is a lot harder than simply backwashing the filter or cleaning the removable components.

The UK Health and Safety Executive lists compulsory swimming caps amongst Health and safety myths; "There is no health and safety regulation which requires people to wear hats in swimming pools". I recall caps being compulsory in some public pools in France and Luxembourg a few decades ago, on the stated grounds of hygiene. Alansplodge (talk) 09:14, 22 June 2018 (UTC)

I agree, I see no hygiene reason to require swimming caps. I think the reason is more practical: Keep hair out of the machinery. Also there may be an added benefit to keep hair oil (if people use it) from scumming up the tiles on the pool walls. And to make the overall swimming experience more pleasant for everyone by keeping long floating hairs out of the pool. A good hair-band to tie back long hair, or wearing the hair in braids, would be just as effective, though. ~Anachronist (talk) 17:59, 22 June 2018 (UTC)

Ah, mainly hair in the works, understood. Still, I'd say tying one's hair back plus better filters would be better than requiring everyone to wear those daft caps. They're uncomfortable and rather spoil the experience. I do miss Canadian lakes. Thank you all again. Anna Frodesiak (talk) 23:21, 22 June 2018 (UTC)

Japan Meteorological Agency

Is there any reason why in Japan the Meteorological Agency handles the earthquakes instead of dedicated seismological authority, given the frequency of their earthquakes? Brandmeister^talk 08:48, 21 June 2018 (UTC)

It also covers volcanoes and tsunamis. Given that these as well as extreme weather, floods and earthquakes all require a warning network as well as sometimes being causationally linked, it makes sense to group them under the same umbrella rather than having separate agencies trying to co-ordinate. The article's reference 7 links to a 32-page PDF here which may shed light on the historical reasons for this arrangement having come about. {The poster formerly known as 87.81.230.195} 2.125.75.224 (talk) 11:12, 21 June 2018 (UTC)

The Philippines' hurricane warning center (PAGASA) is even broader. It handles meteorology, geophysics and astronomy (!) Sagittarian Milky Way (talk) 18:19, 22 June 2018 (UTC)

Australia, where I am, is at the other end of the seismological activity scale from Japan. Earthquakes are very much rarer and less extreme here. We don't have a "dedicated seismological authority". (Or if we do, it's low profile enough for me not to have noticed it.) I do know though than when earthquakes do occur (usually small tremors by global standards) people tend to phone up the local weather service to ask/tell them about it. I guess there's something in human nature that lumps these physical environmental things together. HiLo48 (talk) 22:42, 22 June 2018 (UTC)

Squashed molecules

A few years ago there was a new Wikipedia article on a kind of molecule where the two atoms were abnormally close to each other and electrons were pushed up to higher energy levels to accommodate. This type of molecule was very unstable emitting X-rays to drop energy and push the two atoms apart. I cannot find the article though. What is this kind of molecule called? It's not in Category:Chemical bonding. Graeme Bartlett (talk) 12:28, 21 June 2018 (UTC)

I can't remember that WP article--do you remember if the two atoms were bonded or nonbonded? In the mean time, here is an item describing pushing the limits of nonbonded close contacts.[5] Perhaps WP:CHEM could help--lots of active editors there with diverse interests. For a newer ref that includes intermolecular not just intramolecular-cage, see doi:10.1021/jacs.7b01879. DMacks (talk) 12:49, 21 June 2018 (UTC)

The molecules were much more compressed than in the blog, so much so that one atom appeared to be embedded in the other. The repulsion was much stronger than the bond due to the closeness, but I would guess that the bond would be much stronger than a normal bond. However they still had defined quantum states. (They may form inside white dwarfs for example of the pressure needed). Graeme Bartlett (talk) 22:52, 21 June 2018 (UTC)

By chance, was it related to Rydberg polarons? Those allow you to put atoms inside another atom. 209.149.113.5 (talk) 11:27, 22 June 2018 (UTC)

That is a good suggestion, and the atom combination is like that but at much higher energy. So it was actually another article. I think they needed particle accelerators to get an ion with enough energy to penetrate into another atom. (I should have put the page on my watch list!). Graeme Bartlett (talk) 02:39, 23 June 2018 (UTC)

Diet pills

For me, any 'fat burning' claim of diet pills is automatically suspicious. However, some diet pills claim to block the absorption of fat, something that, at a first glance, seems possible. Could indeed something as small as a pill make our bodies extract less calories from fatty food? I assume ingesting some substances with more volume than a mere pill, like lots of fiber, would have it easier. But still, a pill could de/activate some mechanism, resulting in blocking fat digestion.--Doroletho (talk) 13:03, 21 June 2018 (UTC)

Eating fats don't make you fat, so blocking absorption of fats just seems counterproductive to health. Eating excessive carbohydrates make you fat. If there's a pill that is proven to block absorption of starches and sugars, I don't know what it is. ~Anachronist (talk) 13:48, 21 June 2018 (UTC)

You just haven't looked in the right places. http://media.philly.com/images/1200*800/TapewormDietPills.jpg

And please don't tell people that "Eating fats don't make you fat". Eating more calories than your body burns makes you fat. It matters little what form the calories take. See Healthy diet#Obesity. --Guy Macon (talk) 15:29, 21 June 2018 (UTC)

Beware of Products Promising Miracle Weight Loss, from the FDA, the agency responsible for regulating drugs and medical products, and making sure the advertisements do not make unscientific claims.

In particular:

• "Dietary Supplements are not FDA-Approved" - this means that if a product "isn't technically" a drug, the FDA will not validate the claims they make - even if the seller wraps the product up in a pill shape and puts it in pill-bottles for retail sales... as long as they technically make no medical claims
• Any products that make medical claims - including drugs and things that technically aren't drugs - are still subject to regulation
• A huge variety of products are sold in stores, and are not approved by the FDA. Such products were not put through rigorous independent scientific testing - but you can buy them and eat/drink them anyway (at your own risk of harm, let alone risk of being cheated by the merchant)
• A huge variety of products, including drugs, are approved for treating obesity, or otherwise assisting with weight loss, but those products must be subjected to intense scrutiny - especially about the way they are advertised to consumers
• Widespread efforts by scammy companies to circumvent that scrutiny are the reason why FDA publishes consumer protection messages, like this video: Health Fraud Scams - Weight Loss

I can't find a short statement by FDA that clearly specifies whether the words "weight loss" or "diet pill" are categorically regulated as "medical claims," which probably means that they evaluate each product or situation on an individual basis. Egregious violaters who get caught lying about their unregulated medical products can be subject to civil or criminal action.

Nimur (talk) 16:16, 21 June 2018 (UTC)

Excellent post. I would add that if you sell a pill with nothing in it but inert filler, the FDA will approve it as being safe without approving it as being effective, then the ads scream "FDA Approved!". Homeopathic quackery does this all of the time. --Guy Macon (talk) 18:20, 21 June 2018 (UTC)

Wouldn't a hoemopathic pill that contained nothing kill you from an overdose? (slightly labored reworking of an excellent joke) Greglocock (talk) 22:36, 21 June 2018 (UTC)

The Amazing Randi regularly starts out lectures by sending someone to the local drug store to purchase homeopathic sleeping pills and then when they arrive he "overdoses" on stage. I think that CVS, Walgreens, etc. should stop selling things that they know don't work.

BTW, I created 37 new homeopathic articles on Wikipedia this week. no, not articles on homeopathy; I wrote an article, diluted it a million times, and posted the result. --Guy Macon (talk) 22:55, 21 June 2018 (UTC)

Don't underestimate the power of such pills. And they can do harm. Count Iblis (talk) 23:13, 21 June 2018 (UTC)

Some of the stuff sold over-the-counter can be actually harmful. "And if you’re about to take what you think of as “natural” dietary supplements, ...be aware that FDA has found some of these products also contain hidden active ingredients contained in prescription drugs.", In general, it is not safe to assume that a material is inert, let alone safe in large quantity, simply because it's a "homeopathic" remedy. Worse still, some of these products are (accidentally or intentionally) mislabeled, tainted, or contain active substances that can cause serious harm.

Here is a list of a few hundred products including "herbal remedies" and "natural bee pollen pills" that were found to be illegally tainted with hidden ingredients, often including active drug ingredients that would normally be prescribed by a real medical doctor for totally different medical purposes. Selling a controlled substance and calling it a natural remedy is not only bad, it is actually the most prevalent and widespread drug crime in the United States. Real actual drug crime! The very stuff they don't turn into big-budget Hollywood action movies! In 2016, deaths related to illegal use of controlled prescription drugs exceeded deaths from cocaine and heroin combined.

Even if we know or suspect that a product's claims are pure "quackery," we would be wise not to automatically conclude that the product itself is a totally safe and inert substance - especially in large doses. Nimur (talk) 05:39, 22 June 2018 (UTC)

Do you have a citation that shows that any FDA-approved (for safety, not effectiveness) homeopathic medicine has ever been been tainted in this way? "Since 1988, it has been the de facto policy of the FDA to treat homeopathic remedies listed in the Homeopathic Pharmacopeia of the United States (a collection of homeopathic ingredients and practices continually updated since 1897), as safe and legal to market — so long as that marketing does not meet the FDA’s definition of making fraudulent claims."[6] --Guy Macon (talk) 05:57, 22 June 2018 (UTC)

• Homeopathic Products: "Examples of FDA’s concerns, include:"
  • Pleo Homeopathic Drug Products by Terra-Medica: Recall - Potential for Undeclared Penicillin...

...so, yes. There are just so many more - hundreds of cases each year - and this one example is simply the very first instance I found, after a very cursory reading through the FDA informational page.

In fact, just this week: June 18, 2018, "A 35-year-old Corpus Christi woman has pleaded guilty to one count of possessing a controlled substance with the intent to distribute and one count of receiving a misbranded drug in interstate commerce..." "The FDA found a number of the products X2Zero sold as “herbal weight loss supplements” to contain misbranded or unapproved foreign drugs." The defendant "knowingly possessed and sold diet drugs containing sibutramine," a drug illegal to sell in the United States because it "increased risk of heart attack, stroke and death."

Point being, we don't have to look hard for examples of herbal diet remedies with nasty, often illegal, contaminants.

Nimur (talk) 06:06, 22 June 2018 (UTC)

The pill that blocks fat absorption is orlistat, which is, in fact, FDA approved. I have never personally seen a plausible explanation for the "fat burning" pills, and honestly, that sounds like a really dangerous thing to do, just messing with your metabolism. Someguy1221 (talk) 01:47, 22 June 2018 (UTC)

I do NOT recommend this, but can't Amphetamines speed up your metabolism, and suppress your apetite? @Guy Macon:, can you please enlighten us about the exact nature of fat-burning potential of Crystal Meth, and why it is not a good idea to use it for this? Eliyohub (talk) 17:29, 25 June 2018 (UTC)

Glad to! Turns out that the following is some of the most popular advice I have ever given...

Here is some medical advice: Don't do crystal meth. It will screw up your health. Don't bother asking a doctor if crystal meth is good for you. It isn't. Here is some legal advice: Don't do crystal meth. It is likely to get you arrested. Don't bother asking a lawyer if crystal meth is illegal. It is. Here is some professional advice: Don't do crystal meth. It will use up all of your money and is likely to get you fired. Don't bother asking a certified financial planner if becoming a meth addict is good for your finances. It isn't. (general disclaimer, medical disclaimer. legal disclaimer, risk disclaimer.)

There. I just provided medical, legal, and professional advice, and while I did make a point, I did so without being disruptive. There are some who believe that Wikipedia has a policy against giving medical, legal, and business advice, but no such policy or guideline exists. (If you are about to cite the reference desk guidelines, please read WP:LOCALCON and then show me where the Wikipedia community approved them).

Feel free to report my behavior at WP:ANI if you believe that I have violated any Wikipedia policy or guideline.

BTW, in my opinion both terminal cancer and AIDS are even more effective methods of weight loss than meth, so why not try all three at the same time? Also, don't get your medical advice from an electronics engineer. --Guy Macon (talk) 01:17, 26 June 2018 (UTC)

June 22

Ecoregions follow-up

OK, here's Part 2 of the question I asked earlier about ecoregions of North America (and the real reason why I asked in the first place): Which ecoregions of the United States do not have any native Papilionidae (swallowtail butterfly) species, except maybe near boundaries with other ecoregions, or as very rare vagrants? (NO PHOTOS OF SWALLOWTAIL BUTTERFLIES PLEASE, but maps of their native range are always welcome, especially if these have state lines, major cities and/or ecoregion boundaries shown for reference!) Oh, and I'm asking only about the continental USA -- I know that these critters are found pretty much everywhere in Hawaii, but you won't find them at all in Alaska! 2601:646:8A00:A0B3:4960:40AC:D40E:12AC (talk) 03:04, 22 June 2018 (UTC)

No swallowtail butterflies here
The Imperial Dunes in the Yuma Desert

See distribution map: [7]

Note: Canadian tiger swallowtail (Papilio canadensis) is indeed distributed in Alaska.

The main blank area in the map roughly corresponds with the Yuma Desert section of the Colorado Desert region of the Sonoran Desert.—2606:A000:1126:4CA:0:98F2:CFF6:1782 (talk) 17:43, 22 June 2018 (UTC)

Thanks... for the bad news! :-( So, how big can each of these critters grow (maximum size)? 2601:646:8A00:A0B3:4960:40AC:D40E:12AC (talk) 02:44, 23 June 2018 (UTC)

The largest butterfly that can be found naturally in the United States is the Giant Swallowtail (Papilio cresphontes) with a wing span of 4-6 inches.[8] —2606:A000:1126:4CA:0:98F2:CFF6:1782 (talk) 03:47, 23 June 2018 (UTC)

And the ones which are shown on the map? How big can they grow? (BTW, I was pretty sure P. rutulus could grow to 6 inches or more -- but maybe that's just me being too frightened to estimate size accurately! Or maybe it was P. cresphontes I saw on all those occasions -- is it native to California and/or Oregon?) 2601:646:8A00:A0B3:4960:40AC:D40E:12AC (talk) 06:38, 23 June 2018 (UTC)

Trademark symbols in academic writing

In academic writing is there any point in putting trademark symbols for company names and products like Thermo Fischer Scientific or SYBR Safe? — Preceding unsigned comment added by 129.215.47.59 (talk) 17:53, 22 June 2018 (UTC)

For company names, probably not, unless confusion is likely for some reason without it. For products, it may sometimes be useful. I have seen quite a number of papers using a trademark symbol when giving the proprietary name of a drug. For example, even doctors seeing the names diltiazem and Cardizem might not be certain which is the generic name and which is the proprietary name. Looie496 (talk) 18:04, 22 June 2018 (UTC)

I've never used or seen it in published academic writing. I wouldn't. If it was a requirement, the author guidelines for your journal of choice would say to do it. In my experience. none do. Fgf10 (talk) 08:12, 23 June 2018 (UTC)

Here's one 185.230.100.66 (talk) 00:17, 24 June 2018 (UTC)

I'd say omit ™ (and the related ® too) in general, if possible. Just use consistent and proper capitalization and spelling. From the Chicago Manual of Style: "Although the symbols ® and ™ often accompany trademark names on product packaging and in promotional material, there is no legal requirement to use these symbols, and they should be omitted wherever possible." source

--Doroletho (talk) 12:05, 23 June 2018 (UTC)

Estimating tree mass: is height and species enough?

How accurately can a tree's mass be estimated, given only its height and species? NeonMerlin 22:33, 22 June 2018 (UTC)

Try GlobAllomeTree. Alansplodge (talk) 22:58, 22 June 2018 (UTC)

June 23

Where is the south pole of a power meter's north pole?

I've read that a magnetic monopole has never been observed. In Toronto in the early 2000s, I used a magnetic compass for some science-class work and noticed that when close enough to a power meter, it would always mark the meter as the magnetic north pole. (My neighborhood was of older semidetached houses; I was told my home at the time had been built in the 1950s.) Where is the south pole of a magnet, whose north pole is a power meter of the type I would have observed? NeonMerlin 03:31, 23 June 2018 (UTC)

If I understand your question properly, the "north pole" would be the compass needle's attraction to the meter's electromagnetic field (EMF) -- and in effect, the "south pole" would be, in this case, "ground". 2606:A000:1126:4CA:0:98F2:CFF6:1782 (talk) 07:09, 23 June 2018 (UTC)

No. The compass needle aligns itself along a Field line that emerges from a south magnetic pole and curves through space to return to a north magnetic pole. Both these magnetic poles are located inside the electric power meter and produce an external Magnetic field. This could be prevented by shielding the meter with an iron case. DroneB (talk) 11:40, 23 June 2018 (UTC)

June 24

looking for news about some guy who dies due to using deodorant or perfume

I'm looking for news from many years ago (maybe 10-15 years ago) about a guy that died due to using of deodorant or perfume. In this news they explain that it's not healthy to use them because of that. I don't have any lead for these news. 93.126.116.89 (talk) 07:35, 24 June 2018 (UTC)

Jonathan Capewell or Daniel Huxley, mentioned in our List_of_unusual_deaths#1990s. Brandmeister^talk 09:42, 24 June 2018 (UTC)

No Huxley on that page. --76.69.47.228 (talk) 21:14, 24 June 2018 (UTC)

Because he was the second to die in that manner, so only the first is included. Brandmeister^talk 07:13, 25 June 2018 (UTC)

Remark that Capewell was not killed by the deodorant or perfume itself, but instead by the propellant (butane and propane) in the spray can. 194.174.76.21 (talk) 11:47, 25 June 2018 (UTC) Marco Pagliero Berlin

Yeah, hydrocarbon propellants are flammable, and cans using them usually contain warnings to this effect. Bach in the old days, they used Chlorofluorocarbon propellants, which I think are not flammable, (Halomethane was actually used as a fire-fighting agent) but these were phased out due to damaging the ozone layer Eliyohub (talk) 17:34, 25 June 2018 (UTC)

This is not really relevant, as Capewell was not burned but poisoned. According to Brandmeister's link above Capewell had 0.37 mg/l _each_ of butane and propane in his blood "whereas 0.1 mg per litre can be fatal". He apparently managed to spray his whole body from tip to toe, possibly several times in a day. 194.174.76.21 (talk) 10:37, 26 June 2018 (UTC) Marco Pagliero Berlin

Highest possible limit in nature

What accelerates the fastest particles in nature? Something that's moving below that speed?

And what is the highest possible frequency of an electromagnetic wave? Can a process cause a frequency higher than its own frequency? --Doroletho (talk) 12:24, 24 June 2018 (UTC)

Have you reviewed Electromagnetic radiation? ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:58, 24 June 2018 (UTC)

Yep, but there's no hint of a frequency limit. --Doroletho (talk) 13:19, 24 June 2018 (UTC)

I'm not sure I understand your question. The sun gives off sunlight, which moves at, well, the speed of light while the sun itself moves at a much lower pace (it will depend on which POV you measure from, but it's much less than the speed of light). The highest frequency electromagnetic waves are classified as gamma rays; the article lists some sources, including thunderstorms here on earth. Matt Deres (talk) 13:32, 24 June 2018 (UTC)

The Speed of light 299,792,458 metres per second is a limit that particles cannot exceed so a particle's acceleration is described in terms of its energy or momentum, usually measured in electron volts (eV). Among Particle accelerators the Large Hadron Collider located underground near Geneva reaches a record 6.5 teraelectronvolts (TeV) per beam. Higher energy accelerators will require even larger curved tunnels due to the increased beam rigidity, see Particle accelerator#Higher energies.

The highest possible frequency of an electromagnetic wave is when its wavelength is in the vicinity of the Planck length, such as a Gamma ray of frequency 10²⁰ Hz.

Can a process cause a frequency higher than its own frequency? Yes, when a single frequency (sinusoidal) signal is distorted by a non-linearity then harmonic component frequencies are produced at integer multiples of the input frequency, see Frequency multiplier. DroneB (talk) 13:35, 24 June 2018 (UTC)

Plank frequency is actually about 3×10⁴² Hz, not 10²⁰ Hz. Ruslik_Zero 20:59, 24 June 2018 (UTC)

The OP may find information, and further links of interest, in our article on the Oh-My-God particle. {The poster formerly known as 87.81.230.195} 2.125.75.224 (talk) 21:11, 24 June 2018 (UTC)

Particles with rest mass not only can't exceed c, they can't even attain c, the speed of light in a vacuum, though they can get arbitrarily close. Photons always travel at c in a vacuum, and moreover all observers agree that they travel at c. This is one of the two fundamental premises of special relativity. There isn't anything that "accelerates" photons, because they always travel at c or, if traveling through a medium, slower. --47.146.63.87 (talk) 07:24, 26 June 2018 (UTC)

To be precise, special relativity doesn't say anything about photons, per se. It would be fine with SR if photons had positive rest mass and did not travel at exactly c. The important thing is just that there be a finite c that all observers agree on.

I recall a Scientific American article that detailed how Maxwell's equations would have to be altered if photons were found to have positive rest mass. That was one I found in some ancient stacks in my high-school library. I gather that things have moved on in the interim and that most physicists are convinced that the rest mass of the photon is exactly zero. However that isn't necessary for special relativity. --Trovatore (talk) 03:57, 27 June 2018 (UTC)

• Massless particles (photons) travel at exactly the speed of light, starting when they are created. But particles with mass cannot reach the speed of light, so it's not clear (to me) how to think about their acceleration. In particular, the neutrino is said to have mass. However, neutrinos thought to have been created in the heart of SN 1987A, 168,000 lightyears away, reached Earth slightly before the light did, (the light was delayed within the star by bouncing around, hitting matter.) This means that these neutrinos were moving at most a few parts per billion less than the speed of light. I don't know if we can say that the nuclear decay processes that created the particles "accelerated" them. -Arch dude (talk) 03:13, 27 June 2018 (UTC)

Our article Emission spectrum may be of interest - especially the Origins section. Richerman (talk) 14:25, 27 June 2018 (UTC)

How fast would a lineac have to accelerate protons and nuclei to disintegrate them without collision?

The neutrons and down quarks would be left behind if the electromagnetic field was strong enough to overcome the strong force right? How hard would it be to actually build a lineac that can make an electromagnetic field strong enough to break nuclei or protons? Is it like something we could build (in space?) with $100 billion or $10 trillion or is it forbidden by the known laws of physics or somewhere in between? Sagittarian Milky Way (talk) 16:17, 24 June 2018 (UTC)

The process of accelerating a particle is inherently a type of collision, insofar as momentum and energy are imparted to the particle. A good article to start at would be scattering theory, which introduces some pretty heavy concepts.

The original question - "how fast ... could a particle accelerate ...without a collision..." is almost as meaningless as asking "how fast could a particle move if it wasn't moving?"

Sometimes, it's hard to put ideas about physics into words of the English language; but this is why physicists spend so many years in formal study, so that their terminology is standardized and so they can encapsulate complicated ideas in mathematical formulations that concisely and precisely summarize the statement. A really good introductory physics textbook might be worth your time, before you dive headfirst into theoretical limits that take a toll on simplification.

If you're looking for more palatable fare, here's last week's SLAC public lecture: The End of Spacetime

Nimur (talk) 19:27, 24 June 2018 (UTC)

The electromagnetic force must become larger than the QCD string tension. A charge particle that enters a strong electromagnetic field will accelerate, emit bremsstrahlung, and lose energy. This will happen long before the field has had a chance to build up to the required strength. So, you must consider a neutron which enters a region where there exists a strong field. You can e.g. consider an ultra high energy cosmic ray with a kinetic energy of, say ,$10^{20}$ eV in the form of a neutron that enters the magnetic field of a magnetar, see this article for details. Because the neutron has net zero charge, it won't get deflected by the magnetic field. However, the Lorentz force on the quarks becomes extremely large, so large that this will overcome the QCD string tension. This causes quark anti-quark pairs to be created forming pions, and these pions are ten subject to the extremely strong fields, causing more pions to be formed. Count Iblis (talk) 19:55, 24 June 2018 (UTC)

Neutron has a magnetic moment. So, it is deflected by an inhomogeneous magnetic field. Ruslik_Zero 20:56, 24 June 2018 (UTC)

June 25

Tokamaks and actual fusion

Having looked over the tokamak article, I find myself still in doubt about a pretty central point: Have tokamaks, thus far, achieved actual fusion, at a measurable level?

I guess there are two different sorts of "measurable" that could be of interest here. More academically, one could look for the neutrons and other particles that would be emitted from a fusion reaction, and say whether they have been detected and whether other explanations have been ruled out.

Somewhat more practically, there's a metric called Q that indicates the amount of power produced by the reaction, divided by the power needed to keep the reaction mixture at the indicated temperature and pressure. Is it possible to measure this Q and give a confidence interval for it that does not include zero?

And for both questions, if so, then how long has this been so? --Trovatore (talk) 03:14, 25 June 2018 (UTC)

It's not technically a Tokamak, but the Wendelstein 7X has achieved fusion. It's always been a net power consuming process though, and the experiment was never expected to generate net energy. 202.155.85.18 (talk) 04:07, 25 June 2018 (UTC)

Our Fusion energy gain factor article (the Q factor) says: "As of 2017, the record for scientific breakeven is held by the JET tokamak in the UK, at Q = (16 MW)/(24 MW) ≈ 0.67, first attained in 1997." DMacks (talk) 04:10, 25 June 2018 (UTC)

Thanks (both)!

I think this should be covered in the main tokamak article. As it stands, you can read the whole thing without learning whether they've achieved fusion with the things or not. --Trovatore (talk) 05:48, 25 June 2018 (UTC)

Technically, fusion occurs at all temperatures all the time, just at a very slow rate. Any amount of heating and compression of a gas will increase the rate of fusion. So all fusion experiments achieve fusion in a sense, even Martin Fleischmann's. The question is when you would consider the border to be crossed between a trivial increase in the rate of fusion and one with significant implications for a useful reaction. 202.155.85.18 (talk) 06:28, 25 June 2018 (UTC)

Well, sure, in a "what is not forbidden is required" sense (I'm sure we have an article on that but I can't find it). That's why I specified "measurable". --Trovatore (talk) 19:11, 25 June 2018 (UTC)

The early uses I can find of it are in religious-law practices, such as Thomas Smyth (note none of these DAB entries is the right person?) in 1858 (Complete Works, Volume 9 at Google Books, page 482). DMacks (talk) 19:28, 25 June 2018 (UTC)

I'm talking about the QM concept, not the phrase in general. --Trovatore (talk) 19:29, 25 June 2018 (UTC)

I know that:) But it's a general logical concern too. In physics, it seems to be called "Gell-Mann's Law" (or ...Dictum), for Murray Gell-Mann. DMacks (talk) 19:33, 25 June 2018 (UTC)

Ah, that helps. Our article is at totalitarian principle. --Trovatore (talk) 20:11, 25 June 2018 (UTC)

I could be wrong, but it was my understanding that the rate at which fusion happens "all the time" is not particularly meaningful. Say, could it turn out to be one fusion reaction in a trillion years per ton of deuterium-tritium mixture at standard temperature and pressure? In any case it would have to be something you would detect, if at all, only by detecting the high-energy reaction products escaping, and not by measuring the power output of the reaction. --Trovatore (talk) 19:11, 25 June 2018 (UTC)

Muons catalyse fusion reactions and they are constantly incident on the earth from cosmic sources. About 10,000 impact per square meter of earth every second. Under laboratory conditions each muon can catalyse up to 150 fusion events before they decay or bind thus ending the catalytic cycle. Deuterium molecules confined to a lattice at room temperature can undergo fusion at a rate of around 3000 events per second per mole [9]. I don't know the exact measurements for background fusion rates, but they're reasonably frequent and definitely within the range of measurability. 202.155.85.18 (talk) 00:06, 26 June 2018 (UTC)

Ah, interesting. I wasn't considering muon-catalyzed fusion. But since the tokamak concept is not relying on muon catalysis, it seems like a bit of a distraction.

My vague thoughts on the subject are that a tokamak has to create an environment where D-D and D-T collision events greater than the energy barrier for fusion are common. If you're below the temperature where a typical deuteron/triton has kinetic energy of that order, then you can still get a fusion event if (a) just by luck you get a couple of nuclei colliding that happen to be on the far-right tail of the energy distribution, or (b) the energies aren't that high, but they tunnel over the barrier.

And I think both of those possibilities go down at least exponentially with the energy deficit, correct?

So would it be fair to say there is no measurable non-muon-catalyzed fusion at room temperature? --Trovatore (talk) 00:17, 26 June 2018 (UTC)

The linked article claims ~3000 events per second per mole for deuterium. While any given experiment might not being specifically trying to use muon catalysis, if muons are present, it will benefit from them anyway (they may not be present if the magnetic confinement that keeps the plasma in also keeps the negatively charged muons out...not sure). Without a catalyst of some kind the energy required to overcome the coulomb barrier between two nuclei is prohibitively high. Without it, the sun wouldn't achieve it's large fusion rates (the nuclear fusion inside stars is catalysed via the CNO cycle, positron catalysis and probably also a fair bit of muon catalysis, and possibly also quarks and other poorly understood, speculative processes). You could crunch the numbers and determine the fusion rate at room temperature excluding all catalysis if you really wanted to, but I'm not sure it would be very relevant for a comparison to real systems that have all kinds of catalysis happening all the time. 202.155.85.18 (talk) 00:38, 26 June 2018 (UTC)

"[I]f muons are present it will benefit them anyway" -- sure, but not proportionally. You have muons creating those catalyzed events. You increase the temperature and pressure to the levels of a tokamak that's actually generating power, you don't get any more muons, so who knows, maybe they catalyze a few more events, but presumably not enough to be noticed compared to the the thermally generated ones.

That's why I think it's a distraction to talk about muons. OK, I hadn't thought of them, and it's an interesting point, so thank you for raising it. But I don't think it's really relevant to my question. I was talking about events created by the mechanism the tokamak relies on, and I think muon catalysis is completely irrelevant to that. --Trovatore (talk) 00:47, 26 June 2018 (UTC)

Well, ok then. Here's another irrelevant fact that you might nonetheless find interesting, and it also highlights the banality and commonness of fusion reactions. Commercially available neutron generators for industrial applications like moisture detection use D-T fusion reactions to generate their neutrons. 202.155.85.18 (talk) 04:09, 26 June 2018 (UTC)

That is indeed interesting, thanks! Following on that link, I also found the fascinating fusor article, which seems more "thermal". --Trovatore (talk) 05:06, 26 June 2018 (UTC)

Yes, it's not hard to get nuclei to fuse: just accelerate them to high enough speeds to overcome the Coulomb barrier. This can be done with a fusor you can build yourself that fits on a table, as noted. The thing is, this takes more energy than is released by the fusion reactions. No big deal if what you want is, for instance, a neutron source. Projects like the tokamak are trying to accomplish fusion that gives a net energy release, for generating power. Stars accomplish this because of their enormous mass that compresses the nuclei in the core. The problem is we can't fit a star inside the building next door, so we instead have to use extremely strong magnetic fields that take a lot of energy to produce. --47.146.63.87 (talk) 07:16, 26 June 2018 (UTC)

Moment of Inertia, Torque and Angular Momentum

This excerpt from my textbook appears to contradict itself. It seems to give two different definitions for torque: one being the first derivative of the moment of inertia with respect to time, the other being the first derivative of angular momentum with respect to time (both circled in red). I can't see how it's possible for both to be true. In a normal circumstance we wouldn't expect the moment of inertia to change with respect to time anyway during the course of applying a torque (maybe orbits are a different story where accelerating a body will cause the radius of its orbit to increase, but simple, classical systems like a spinning disc or whatever wouldn't see a change). By the analogy implied by the textbook itself, force is not the first derivative of mass in linear kinematics either. Is this a mistake in the text, or am I missing something? 202.155.85.18 (talk) 04:06, 25 June 2018 (UTC)

Lousy textbook. T=I*d(omega)/dt , or as they also say T=dJ/dt. Typo maybe. Greglocock (talk) 05:02, 25 June 2018 (UTC)

Yes, probably the printers mixing up Is and Js, and not knowing any mathematics or physics. This is the sort of error that a good specialist proof-reader should have corrected. Dbfirs 06:29, 25 June 2018 (UTC)

It's possible it's a typo... or, it's an advanced physics book, and they're analytically decomposing the formula for torque by applying the product rule to calculate it for a nonrigid object. Conceptually: if the object is deforming inelastically, there can be a torque that relates to the change in shape, hence change in the moment of inertia. Which textbook are you using?

Torque is the derivative of angular momentum; so it is ${\frac {d(I\omega )}{dt}}=I{\frac {\partial \omega }{\partial t}}+\omega {\frac {\partial I}{\partial t}}$. It is very rare - in textbooks, at least - for the partial of the moment of inertia to be non-zero. A non-zero rate of change in the moment of inertia means that mass is moving in the object; a classical case would be a complex pendulum, which is invariably the pedagogical instrument that is specifically used to knock physics students out of Newtonian mechanics and into advanced dynamical analytic tools, mostly by shaking a lot of time-varying force equations at them.

By analogy to linear dynamics - it is rare but not impossible to impart momentum by changing an object's mass with respect to time: ${\frac {dp}{dt}}={\frac {d(mv)}{dt}}=m{\frac {\partial v}{\partial t}}+v{\frac {\partial m}{\partial t}}$. Although it is rare in elementary physics to change mass with respect to time, it is a critical element in non-rigid body analysis. This full expansion, it turns out, is the foundation of the rocket equation. The other textbook example cases are a heavy chain falling off a table, or a massive train derailing, changing the mass of its cars. If we zero out that second term, we get our familiar "F=m a" formulation, which is the kind of ancient, centuries-old Newtonian physics they teach to teenagers in schools.

My copy of Marion & Thornton - which is now apparently available online at Archive.org - introduces torque in a few important places - notably, in the chapter on, ahem, "rocket dynamics," where a younger version of myself penciled in the margins: "very horrible algebra." Every physicist should read this book, and real physicists should own a copy so they can pencil in their own commentaries.

Sadly, in the case brought by our OP, it looks like it's just an unfortunate typographical error, and not a foray into exciting nuances of physics. But why waste a learning opportunity?

Nimur (talk) 14:39, 25 June 2018 (UTC)

The textbook is ATKINS, P. W., & DE PAULA, J. (2006). Atkins' Physical chemistry. Oxford, Oxford University Press. The probable typo is from page 11 in the "Foundations" section; essentially a review of basic chemistry and physics that is assumed knowledge for the rest of text. 202.155.85.18 (talk) 00:17, 26 June 2018 (UTC)

I agree that formula (B.6) contains a typo but still the partial derivative of I by time is quite often non-zero when, for instance, a non-spherical body rotates. This of course depends on choice of the reference frame. Ruslik_Zero 18:25, 25 June 2018 (UTC)

In such cases, it's more common to expand the scalar moment of inertia into an inertia tensor so that it is non-time-variant, irrespective of the axis of rotation. (...grumble, grumble, something about why this is always guaranteed to be possible). But you could, of course, use a wacky coordinate system and encapsulate the object's apparent change in moment-of-inertia by writing it as a time-varying scalar property, functionally coupled to the rate and axis of rotation. I'm not sure that would be easier... but hey, it presents an awesome opportunity to conduct some fun with equations! Nimur (talk) 20:49, 25 June 2018 (UTC)

Swallowtails follow-up (last question on this subject, I hope)

Hello again, since it was shown to me a few days ago that swallowtail butterflies are found pretty much everywhere in North America and I can never be sure to avoid them completely (unless I move to the western half of Alaska, or to the Yuma Desert), I've decided to see if I can overcome my fear of them instead -- and I'm trying to think of a strategy to do that. But for this, I'll absolutely need the following info:

• 1) What is the native range of Papilio cresphontes (the biggest of all, and therefore the one which would scare me the most)?
• 2) How large (in terms of wingspan) are each of the most common North American swallowtail species, P. appalachiensis, P. canadensis, P. eurimedon (sp.?), P. glaucus, P. multicaudata and P. rutulus? (I need either the range of wingspans, or the maximum wingspan, in either inches or centimeters.)
• 3) Excluding the above-named species, I need the following info on any and all swallowtail species which are found in the USA and which can reach a size (in terms of wingspan) of more than 3 inches (excluding Battus philenor, because I have already looked up the info for that one and discovered that photos of it do not scare me): species name, native range, wingspan (either maximum wingspan or range of wingspans), and whether or not the species is tiger-striped (i.e. has any pattern of contrasting dark stripes or veins on a bright background, like the above-named species, or vice versa -- this is a major factor in my phobia of them).
  

As before, NO PICTURES PLEASE (but maps are welcome) -- I don't want to get an anxiety-induced heart attack from seeing close-ups of those critters, seeing them every summer IRL is bad enough! 2601:646:8A00:A0B3:4960:40AC:D40E:12AC (talk) 08:14, 25 June 2018 (UTC)

A tentative suggestion: in the UK we have recreational Butterfly farms (as I am accustomed to calling them, but our article is at Butterfly house – NB: one photo of NOT-Swallowtail butterflies lower down in the article), where one can visit hothouses containing (in both senses of the word) native and exotic butterflies that one can walk amongst – if one so wishes. (Understandably, this might not be something you've previously sought out in your locality.) At such a venue one could, perhaps, arrange to observe the problematic butterflies from the other side of glass or mesh barriers without immediate "danger" of physical contact. I will not presume to discuss the details of what amounts to medical treatment (as I suppose you have already given this topic much thought), but our articles Specific phobia and Exposure therapy might be of broad interest.

That first article has a link to List of butterfly houses (NB: photos of large butterfly-shaped billboards, though none clearly showing actual butterflies), which contains a lengthy list of such venues in the USA. {The poster formerly known as 87.81.230.195} 2.125.75.224 (talk) 15:40, 25 June 2018 (UTC)

Yeah, in fact the strategy I have in mind is a sort of impromptu DIY exposure therapy (in fact, I've been doing this since early childhood and this has helped me to overcome my fear of many other butterfly species, from cabbage whites to monarchs) -- I just want to take this to the next level, now that I've narrowed down the problem species to only tiger-striped swallowtails, I think that if I deliberately occasionally expose myself to the smaller-sized species in this category (while avoiding the big ones, at least until my fear has faded significantly), my fear will fade over time. The only problem is, this takes time (several years for each "kind", as defined by wing shape and coloration), and my place of residence is within the native range of some VERY large swallowtails (including, possibly, P. cresphontes, the worst offender of them all) -- so every spring and summer, I see the really big ones and it traumatizes me all over again and undoes any kind of exposure therapy I might have done, and in fact leaves me worse off than before. So tell me, where can I go to see the smaller ones while avoiding the bigger ones? And, once again, what is the size of the common North American species listed above (P. canadensis, P. glaucus, P. multicaudata, etc.) -- would they be too big for me, or not? 2601:646:8A00:A0B3:4960:40AC:D40E:12AC (talk) 09:19, 26 June 2018 (UTC)

I am on the wrong side of the Atlantic to be giving detailed advice about either sizes and distributions of North American lepidoptera, or the species bred at particular establishments. For the latter, you could contact conveniently located venues directly and discuss your problem (about which I'm sure they'd be sympathetic); for the former, you might search for and read the Wikipedia articles on the individual species with the pictures turned off – I don't know how to do this but I'm fairly sure it can be done, so an editor with more Wiki-fu will hopefully be along shortly to advise about this. {The poster formerly known as 87.81.230.195} 2.125.75.224 (talk) 16:03, 26 June 2018 (UTC)

There are a number of options here: Help:Options to hide an image -- To do so specifically for Wikipedia requires logging on as a registered user and editing a file; otherwise, there are browser-specific options. —2606:A000:1126:20CE:0:98F2:CFF6:1782 (talk) 19:05, 26 June 2018 (UTC)

Thanks, 2606 IP -- I'll do this shortly. 2601:646:8A00:A0B3:157E:9722:AD27:3562 (talk) 10:03, 27 June 2018 (UTC)

Reducing neutronium

Is it possible in theory form a BCS pair from two disimiliar fermions, namely the neutron and electron? If so, can this be considered to be analoguous to reduction in the chemical sense; can one then consider a BCS paired, neutron infused electride to be a neutronide compound, even though it would only be stable at nano-Kelvin temperatures? Plasmic Physics (talk) 13:10, 25 June 2018 (UTC)

These usually requires identical particles as their Fermi energy should be the same. Ruslik_Zero 18:43, 25 June 2018 (UTC)

'Usually' or 'absolutely'? I thought that it would be determined by the common denominator. Plasmic Physics (talk) 19:43, 25 June 2018 (UTC)

Radiation Symbol T-Shirts

Are there any efforts to ban this (or similar uses) type of use of the radiation icon? Wouldn't that dilute the powerful message the icon is meant to conceive? --Doroletho (talk) 17:24, 25 June 2018 (UTC)

To my knowledge, there are many regulations and laws in the United States that require markings and placards for certain hazardous materials - (e.g. for purposes of transportation, 49 C.F.R. §172.300 and onward); but I am not aware of any American laws that prohibit incorrect or unauthorized use of markings or placards in cases where a real hazard does not actually exist. On a technicality, you could probably find some regulation or local law that prohibits these types of unauthorized markings... or if you can technically classify wearing the t-shirt as "transportation" then you could cite §172.303 or §172.401 or §172.502, but those are DOT rules and probably do not apply to a t-shirt.

Generally, especially when I'm around lab newbies, I try very hard to indoctrinate that warning-signs are not "cool-looking decorations." They are actual, functional warning signs, and should be used correctly.

Nimur (talk) 20:43, 25 June 2018 (UTC)

• The first amendment of the constitution of the US protects freedom of speech, which includes display of icons. In theory, no law can prohibit the display of these symbols. However, if such display results in actual harm, then the person who displayed it can be prosecuted for causing that harm: the "don't yell fire in a crowded theater" scenario. -Arch dude (talk)

If you could earn a dollar for every time you found an instance in which the conjunction of two laws yielded a logical contradiction, then mathematicians would get paid more than lawyers. Anyway, I'm pretty sure that constitutional protections of free speech are not equivalent to a universal inalienable license to speak or display any thing, at any time, at any place. Here's a philosophical rumination on the topic from the Plato Encyclopedia; and here's a 2014 summary on the limits of free speech, a report prepared by the attorney for the Library of Congress on behalf of the Congressional Research Service. Nimur (talk) 12:52, 26 June 2018 (UTC)

Technically, people are radioactive, so the shirt isn't even wrong. I am a radiation safety officer in Australia, and the regulations require us to affix radiation warnings if certain criteria are met, but do not prevent us from using the signage just to be safe in cases that may fall short of the criteria. 61.247.39.121 (talk) 23:27, 25 June 2018 (UTC)

If you're in a counting lab, it's not so unusual to see things warning stickered (bananas?) if they merely have a high background count (far from a hazardous one), and so shouldn't be left near or in the shielded counting chambers. I've even seen this on packets of welding rod - specially prepared low-background rods were to be used, not the standard grade stuff. Some scrap armour from the German fleet was spray-stencilled with a green logo when it was recovered in the 1980s to distinguish it. Andy Dingley (talk) 09:15, 26 June 2018 (UTC)

June 26

Could all diesel engines use pure cetane if it's warm enough?

Are there cons besides wasting money and freezing at 18 Celsius? Sagittarian Milky Way (talk) 00:27, 26 June 2018 (UTC)

All "regular" fuel contains various fuel additives to impair engine wear and tear. So if you were to use pure anything as fuel, you'd beat up the engine. Apart from that, I believe you can use just about anything in a diesel engine as long as it will ignite under the conditions in the engine. --47.146.63.87 (talk) 07:05, 26 June 2018 (UTC)

Is there anything in Diesel engine which confirms what you believe? ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:20, 26 June 2018 (UTC)

Almost certainly not. The highest grade of premium diesel fuel has a cetane index around 60. Pure cetane would ignite too early in the compression cycle, and would exert force that pushes backward against the engine. Looie496 (talk) 12:46, 26 June 2018 (UTC)

According to our article Since only air is compressed in a diesel engine, and fuel is not introduced into the cylinder until shortly before top dead centre (TDC), premature detonation is not a problem and compression ratios are much higher.

Beside that (and independently from what there is in Diesel engine) it is common knowledge that with some proper adjustment most diesel engine would run on almost everything, see e.g. http://www.uniteddiesel.co.uk/faq/can-a-diesel-engine-run-on-fuel-other-than-diesel and https://www.quora.com/Is-it-possible-to-make-motor-engines-which-can-run-on-both-petrol-and-diesel-at-the-same-time 194.174.76.21 (talk) 14:39, 26 June 2018 (UTC) Marco Pagliero Berlin

Does that "almost everything" include banana peels, for example? ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:52, 26 June 2018 (UTC)

You could produce ethanol with the banana peal, and run on a ethanol-diesel blend. Doroletho (talk) 16:29, 26 June 2018 (UTC)

Good luck running today's diesel engines on (pure) ethanol.

Simplifying to the extreme: a diesel engine works by compressing air to high temperature/pressure, injecting fuel, and waiting for fuel auto-ignition and combustion. The cetane number basically is a measure of whether the fuel is easy or hard to auto-ignite.

The moment at which fuel is injected can be changed (I believe, but found no source to check, that it is changed in real time by the engine control unit in order to fix deviations in engine temperature or fuel composition), so that if you use a fuel that autoignites more rapidly you inject later to make up for the difference in delay, and keep the pressure peak at roughly the same "optimal" position (injection timing will change engine efficiency and pollutant production). In particular, cetane is always OK. However, if the fuel has a very long autoignition delay (e.g. ethanol), you can inject sooner, but thermodynamic conditions may not allow autoignition if you are too far from top dead center (temperature is high only when the piston is close to TDC). (For more mathy details about auto-ignition delays when temperature varies, a good search term is "Livengood-Wu integral").

TLDR - for diesel engine fuels, easier to ignite = better (all other things being equal). Tigraan^{Click here to contact me} 08:41, 27 June 2018 (UTC)

So there would be no lubricity issues? How warm would the pure cetane have to be to not lower engine life by trying to force a too viscous liquid through a high pressure and tiny common rail fuel injector hole? Sagittarian Milky Way (talk) 18:01, 27 June 2018 (UTC)

Well, there could be, I have no idea. If you want to ask about lubricity of fuels, I would suggest opening a new thread. Tigraan^{Click here to contact me} 14:21, 28 June 2018 (UTC)

Chicago Manual of Style: 1% vs 1 % ?

Does the Chicago Manual of Style dictate whether there should be space between a number and the percentage symbol? --129.215.47.59 (talk) 12:26, 26 June 2018 (UTC)

No space. See example and pointers to specific MoS rules at [10]. DMacks (talk) 12:40, 26 June 2018 (UTC)

(ec) When in doubt about what the Chicago Manual of Style has to say, see the Chicago Manual of Style. TenOfAllTrades(talk) 12:48, 26 June 2018 (UTC)

Well, "see" if you or your affiliated institution has paid for it. That's why I went with a secondary but freely-accessible one. I'm not near a VPN-able machine right now, could you see what 10.52 and 10.61 are about (mentioned in the FAQ I linked)? DMacks (talk) 13:18, 26 June 2018 (UTC)

If you can't use a VPN, the Tor browser can do a lot of what you normally do with a VPN. --Guy Macon (talk) 00:01, 27 June 2018 (UTC)

Wut? DMacks was obviously talking about VPN-ing into their institution's credentials for the CMS. I doubt many Tor exit nodes have an institutional subscription. Tigraan^{Click here to contact me} 14:24, 28 June 2018 (UTC)

Determination of hydration number of ions

I see that the article Hydration number has a section titled Determination of .. where methods like NMR, neutron scattering and X-ray scattering are mentioned to involve radial distribution function, but some details about how the hydration number follows from those methods are missing. So I'd like to ask here how this quantity is derived from those methods? Which are the derivations steps? Thanks.--5.2.200.163 (talk) 15:46, 26 June 2018 (UTC)

These derivations are not trivial. You really have to go to the sources that are cited in that section to read how the derivation was performed for each method, and then each of those links to even earlier literature that explains how the equations they use were derived. Someguy1221 (talk) 20:26, 26 June 2018 (UTC)

NanoDrop ND-1000 from Thermo Scientific or Thermo-Fischer Scientific?

If I'm writing that I used a piece of equipment and want to put the manufacturer in parantheses but the company merged since the time of manufacture, changing from Thermo Scientific to Thermo-Fischer Scientific, do I write the old or current name of the company? 129.215.47.59 (talk) 17:46, 26 June 2018 (UTC)

Thermo Fisher Scientific is an American multinational biotechnology product development company, created in 2006 by the merger of Thermo Electron and Fisher Scientific, and currently owns the brand NanoDrop . Giving the current name of the company will be more useful to a reader seeking further information. DroneB (talk) 19:18, 26 June 2018 (UTC)

References

The Biology of Human Starvation

Where can I download the full text of "The Biology of Human Starvation" by Ancel Keys from 1950? Thanks for your help.— Preceding unsigned comment added by 180.183.85.18 (talk • contribs)

The book is not in the public domain, so downloading it would be book piracy, which is illegal for most users on this site. Ian.thomson (talk) 18:11, 26 June 2018 (UTC)

According to Google Books there is no electronic version of this text available. Your best bet would be to find a library on WorldCat that carries it. It can be found in many university libraries. Someguy1221 (talk) 20:17, 26 June 2018 (UTC)

• I recently needed to refer to a book. It was cheaper and far less hassle to just order a used one from Amazon than it would have been to try to get it via inter-library loan. -Arch dude (talk)

What is this and should I be worried?

I have a large stand of alders on my property that are just coming to maturity after a decade or so. In the last week I’ve seen these weird yellow spots on some of them. It doesn’t looks like anything good, but I don’t know if there is anything I cnan or should try to do about it. Beeblebrox (talk) 22:18, 26 June 2018 (UTC)

Perhaps Phytophthora alni? Count Iblis (talk) 22:37, 26 June 2018 (UTC)

Doesn't look like that to me, my thought was an insect laying eggs. Would it be possible to get some more close up pictures, and of the reverse of the leaf as well? DuncanHill (talk) 22:42, 26 June 2018 (UTC)

I think they are alder leaf galls, perhaps caused by Eriophyes inangulis. (You can find pictures online that look a lot more like yours than the ones in our article, for example https://www.alamy.com/stock-photo-a-leaf-gall-caused-by-the-mite-eriophyes-laevis-on-alder-leaves-dorset-20563260.html.) Looie496 (talk) 22:57, 26 June 2018 (UTC)

I think that’s pretty likely, it looks a lot like some of those images. Sounds harmless so that’s a relief. Beeblebrox (talk) 00:37, 27 June 2018 (UTC)

Effects on refrigerated food of exposure to ozone

What are the effects on refrigerated food of exposure to ozone? I ask because a well-known brand of refrigerator advertises itself with the claim "Active Oxygen removes bad smells, such as strong cheeses, and keeps bacteria at bay to keep your food fresher for longer. Active Oxygen technology releases tri-oxygen molecules (O3) into the fridge, which neutralises unpleasant odours and helps prevent bacteria growth by oxidising it away. Active Oxygen is a molecule made up of 3 oxygen atoms – the same type that are present in nature and released into the atmosphere during a thunderstorm. Active Oxygen technology recreates this process inside your machine, so it doesn't need any refilling or maintenance." I'm not sure I'd want a lungful of ozone every time I made a cup of tea, but that's another matter. DuncanHill (talk) 23:48, 26 June 2018 (UTC)

That would depend on the concentration of ozone in the air volume within the refrigerator. At low concentrations, it would only react with the surfaces of food items. Ozone can in theory degrade nutrients (especially anti-oxidants) in the food items by oxidising them, so you wouldn't want the ozone to penetrate too deeply beyond the surfaces of food items. When ozone reacts, it generates regular, harmless oxygen in the process. If the concentration is significant, you could be damaging your health in the long term from the cummulative effect of repeatedly inhalling ozone everytime you open the refrigerator door. I can't say for sure whether any of these things are worth worrying about, as I don't know the concentration involved here. Plasmic Physics (talk) 00:55, 27 June 2018 (UTC)

Seems like a combination of uselessness and danger; you don't want to be inhaling ozone on a regular basis - see Ozone#Health_effects. Maybe they should instead come up with a way to displace the oxygen in the fridge with nitrogen and reduce spoilage that way. Matt Deres (talk) 12:50, 27 June 2018 (UTC)

June 27

Post-merger LIGO data

Does the LIGO data from after a black hole merger support either one of the following, and if so does that resolve the inner lives of black holes?

• Post-merger two point masses continue into each other and become a single point mass

or

• Post-merger two blobs simply become one big blob with no further evolution.

Hcobb (talk) 00:16, 27 June 2018 (UTC)

Define "post-merger". The LIGO data fits extremely well with the inspiral-merger-ringdown model that was constructed from numerical simulations of general relativity. The black holes don't instantly become one sphere after their horizons touch - a thread forms between them that expands, and the black hole becomes an elongated sphere, which then oscillates between that and a flattened sphere, emitting more gravitational waves until it settles into a final state. You can never observe events occurring beyond the event horizon, and if such a thing was consistent with LIGO data, you can bet there would be a lot of noise about that. Someguy1221 (talk) 01:12, 27 June 2018 (UTC)

Our article is at binary black hole. The ring down phase gets exponentially weaker over time, and it should really be gravitationally red shifted for ever. So basically the signal gets too weak to detect, and there is no detection of anythiing inside the event horizons. Graeme Bartlett (talk) 01:52, 28 June 2018 (UTC)

Electrons

I'm looking for evidence that the electron is not in fact a particle but a bundle of electromagmetic energy vibrating at the speed of light. Can anyone refer me? 80.2.21.17 (talk) 01:39, 27 June 2018 (UTC)

Well that's not what the electron is, so why would there be anywhere to refer you to? It's also not even clear what "a bundle of electromagnetic energy vibrating at the speed of light" even means. It sounds like one of those gobbledygook chains of sciency words that's so vague it's not even wrong. Someguy1221 (talk) 03:03, 27 June 2018 (UTC)

Wave–particle duality might be of interest. —107.15.157.44 (talk) 03:16, 27 June 2018 (UTC)

• I would kindly suggest to read our article about confirmation bias. Online search engines are very good at finding "evidence" for anything no matter how far-fetched, but setting out to search evidence for a particular position is not how you inform yourself about the validity of that position. Tigraan^{Click here to contact me} 08:21, 27 June 2018 (UTC)

An electron has finite mass that cannot move as fast as the speed of light, though accelerating an electron causes Bremsstrahlung i.e. "braking radiation" emission of photons that do travel at light speed in a vacuum. DroneB (talk) 17:21, 27 June 2018 (UTC)

The current state on the debate relating to quantum wave-particle duality is concisely discussed here:[11]. It references the following study which concludes: "According to our analysis, the duality principle in its standard form is safe and sound, but our duality relation remains to be thoroughly tested.":[12]. 2606:A000:1126:20CE:0:98F2:CFF6:1782 (talk) 18:54, 27 June 2018 (UTC)

The first thing you should do is read these two pages: [13] [14]. The main point is, if you don't have a mathematical framework worked out then all you have is a vague guess, which we call a hypothesis. The next thing to do is to come up with ways to test that hypothesis. What observations are predicted if your proposal is true? Just as an interested layman, the thing that jumps out at me is that, assuming you mean "vibrating at the speed of light in a vacuum", this I believe violates special relativity. The electron has rest mass, which means it can't attain c, the speed of light in a vacuum. Admittedly I'm not completely sure if something "vibrating" at that speed violates it, but I'm not sure that statement has any real meaning. What frequency do you think it's vibrating at? Does this relate to the electron's de Broglie wavelength? If you really want to pursue this, you need to work out what your prediction implies. Also, nothing personal, but be prepared to accept that you're probably wrong. I'm assuming you don't have a physics background, and it's very unlikely for anyone without one to develop some groundbreaking new physics. But don't let this discourage you from learning more. And feel welcome to ask us for help in learning more. --47.146.63.87 (talk) 23:34, 27 June 2018 (UTC)

Neuroscientific plausibility of BLIT (short story)

David Langford's BLIT and its companion stories describe images which cause instant death (or at least harmful symptoms) when viewed by "crashing" the brain. Given what is known about visual processing, is it plausible that viewing an image could kill someone as described by Langford? 169.228.167.108 (talk) 03:18, 27 June 2018 (UTC)

It would be quite a stretch, but in sci-fi that is common. One could imagine certain images triggering a spontaneous fatal occipital epileptic event. —2606:A000:1126:20CE:0:98F2:CFF6:1782 (talk) 04:48, 27 June 2018 (UTC)

• There are several earlier sci-fi treatments of this. Victor Contoski Wrote "Von Goom's Gambit" in 1966, wherein any chess master who discovers this particular chess sequence is so horrified that death immediately follows. Stephenson's 1992 Snow Crash is about a linguistinc "virus" crashing the brain's operating system. -Arch dude (talk) 05:20, 27 June 2018 (UTC)

Or Monty Python's "Funniest Joke in the World" (1969). —2606:A000:1126:20CE:0:98F2:CFF6:1782 (talk) 05:24, 27 June 2018 (UTC)

Zwei peanuts ver valking down ze Strasse, von vas assaulted. Peanut. Sagittarian Milky Way (talk) 18:04, 27 June 2018 (UTC)

Is there any way to see scientifically plausible Earths that almost were?

Is deriving today's (or even the Cambrian's?) world map from only a near-omniscient knowledge of 4 billion BC and the laws of physics the realm of the butterfly effect? Planetesimal orbits/impacts are only probabilistic beyond a few million years and many left lava seas of pierced crust so maybe right? Then is there a way I could see a scientifically accurate or at least plausible simulated world map with the minimum change needed to butterfly effect away the current world map into randomness? Are these computationally cheap enough to make to do statistical analyses? i.e. is the longest continent of 4.56 billion year old Earths more likely to be longer or shorter than current Eurasia, how often are the South Poles of 4.56 billion year old Earths in ocean trenches, odds of unbroken equatorial current, smallest world's largest continent in X simulations.. Sagittarian Milky Way (talk) 17:55, 27 June 2018 (UTC)

Short answer: no. 2606:A000:1126:20CE:0:98F2:CFF6:1782 (talk) 20:28, 27 June 2018 (UTC) ... CAUTION: attempting to read above query may result in spontaneous crashing of the brain's operating system

I've seen the current continent configuration my whole life, I just wanted to see another one. One of the more likely ones, not "perfectly square Pangea" or "roll dice, each map pixel under 3 is land". Sagittarian Milky Way (talk) 01:53, 28 June 2018 (UTC)

Here's one purported "scientific" what-if alternative Earth map: Daily Mail (ignore article on Gabrielle Union in nude bikini). —2606:A000:1126:20CE:0:98F2:CFF6:1782 (talk) 02:21, 28 June 2018 (UTC)

Please be aware the Daily Fail is an odious publication filled with hate speech. It is also widely known for it's terrible reporting of anything vaguely scientific. You really shouldn't link to it. Fgf10 (talk) 07:58, 28 June 2018 (UTC)

The article about Gabrielle Union seems scientific enough. ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:37, 28 June 2018 (UTC)

• Continental drift appears to be driven by convective upwelling currents in the mantle. Convective upwelling is notoriously chaotic in the technical sense of the term, so any sort of actual prediction is pretty much a non-starter. It might be possible to build a simulation that would be realistic, but not not one that would yield Earth's actual continents over time. Other processes that result from convective upwelling include Mesoscale convective systems of thunderstorms and boiling liquids in a pot. The weather guys cannot predict the locations of thunderstorms within a mesoscale system, but they can tell us roughly what percentage of the area will have the storms. Similarly, you cannot produce a model that will show exactly where the steam bubbles will be in a roiling pot, but you can describe them statistically. -Arch dude (talk) 03:36, 28 June 2018 (UTC)

• The mechanisms driving continental drift are not understood well enough to support long-term modeling. It is possible to make predictions for a few million years by assuming that the continents will keep moving in the same way they are now, but the mechanisms that cause continents to change their speed and direction of motion are very poorly understood. Looie496 (talk) 13:23, 28 June 2018 (UTC)

4.56 billion years ago the Earth was a boiling ball of liquid rock. Count Iblis (talk) 15:44, 28 June 2018 (UTC)

Giraffe's Feet

I read in a paper: "Although the giraffe's toes are indeed separate from one another, a thin layer of spongy tissue sits beneath the toes and attaches them one to the other." I would be grateful if a user could please inform me whether or not this statement is correct. Thank you.Simonschaim (talk) 18:19, 27 June 2018 (UTC)

See even-toed ungulate, the group of which giraffes are a member. They all have the same basic foot anatomy. --47.146.63.87 (talk) 23:10, 27 June 2018 (UTC)

Neither of those articles (nor any other I have so far found) address the query. It might help us to assess the statement if Simonschaim tells us where it was found. {The poster formerly known as 87.81.230.195} 2.122.0.113 (talk) 12:38, 28 June 2018 (UTC)

It could be http://www.dailyhalacha.com/m/halacha.aspx?id=502 But the photos of giraffes' feet I found on the net ( https://www.google.com/search?q=%22giraffe%22+%22hooves%22&sa=X&complete=0&hl=de&tbm=isch&tbo=u&source=univ&ved=0ahUKEwi02dPq4vbbAhUBUlAKHd5nCAQQsAQIKQ&biw=1280&bih=923 ) show clearly separated nails/hoofs, even if the toes are not. It is possibly a question of definig toes vs. hoofs? Which question I think is rather clear in English, but it is maybe not so clear in the language of the Torah?194.174.76.21 (talk) 16:28, 28 June 2018 (UTC) Marco Pagliero Berlin

June 28

Reporter gene affecting expression of other genes?

Are there any cases where a reporter gene in an experiment has affected the expression of other genes which were being studied? --129.215.47.59 (talk) 13:21, 28 June 2018 (UTC)