Wikipedia:Reference desk/Archives/Science/2018 September 8

= September 8 =

Forest planets and city planets
I know lately that astronomers talk about ocean planets, iron planets, ice planets, and lava planets and are mentioned in scientific journals. I also believe there exists forest planets and city planets such as seen in science fiction. But why haven't the possibilities of forest planets and city planets seriously considered by astronomers and mentioned in journals? (though I've seen one mention of forest planets when talking about observing fingerprint of red edge vegetation using spectra) Forest planets provide evidence of complex vegetation on the surface, while city planets have evidence of intelligent civilization. Forest planets would have trees that cover most (but not all) of the planet's surface, while city planets have urban areas that cover much of the surface. Planet Star  03:15, 8 September 2018 (UTC)
 * Wouldn't either of those just be terrestrial planets? 139.194.67.236 (talk) 03:42, 8 September 2018 (UTC)


 * Although evidence + speculation = theory,[me] speculation is the realm of science fiction and evidence is the realm of science journals. I'm sure, however, that astronomers and astrophysicists discuss such things around the water cooler (so to speak). 107.15.157.44 (talk) 04:33, 8 September 2018 (UTC)
 * A "forest planet" is unlikely to exist, unless you significantly dilute the definition of "forest". It would require most of a planet's land to be covered by a certain type of life, regardless of variations in climate, terrain, etc. To look at our single example, Earth, trees can't thrive where it's too arid, or it gets too much below freezing for too long, or the soil is unsuitable. Even in some of these habitats where it's possible to grow certain trees (e.g., grasslands), other organisms out-compete them because they're better-adapted. A ecumenopolis is hypothetically possible, but efforts to detect other planets will naturally focus on the more likely scenario (as here on Earth) of large urban areas, but not ones covering the entire planet.
 * The examples you've given are the result of processes not involving life, and these processes are fairly well-understood, most with examples in our own Solar System: ice planet, ocean planet, iron planet, lava planet. --47.146.63.87 (talk) 06:24, 8 September 2018 (UTC)


 * I believe forest planets do exist, albeit rarely. Our galaxy contains billions of planets, at least few of those are forest planets. Naturally making into forest planets with trees or tree-like organisms growing over much of the surface are naturally difficult but not impossible. Forest planets can still have mountains, deserts, savannahs, bodies of water, and ice fields and glaciers, albeit covering substantially less than 50% of the planet in total. Several forest planets are seen in science fiction, including Dagobah and Endor (moon) in Star Wars. A related type is jungle planet, which would have jungles covering more than 50% of the planet's surface. I believe city planets like Coruscant are even more rare than forest planets and jungle planets. Planet  Star  02:12, 9 September 2018 (UTC)
 * Well sure, if you define "forest planet" as simply "any planet with more than 50% of land occupied by forest", such planets are more likely. I think "forest planet" in science fiction generally implies near-total coverage. Earth has 30% of land occupied by forest, so we're not too far from being a forest planet under that definition. --47.146.63.87 (talk) 07:05, 9 September 2018 (UTC)
 * How many of the earth's trees can be seen from the earth's moon? ←Baseball Bugs What's up, Doc? carrots→ 11:19, 8 September 2018 (UTC)
 * None individually, but attempts at analyzing exoplanets don't involve trying to spot trees through a telescope, which is impossible, but tools such as spectroscopic analysis. If there are lots of photosynthetic organisms that absorb certain wavelengths of light, that will cause an effect that may be detectable. Another smoking gun would be the presence of free oxygen in the atmosphere, which is also detectable through spectroscopy. --47.146.63.87 (talk) 07:05, 9 September 2018 (UTC)
 * If a planet were covered in trees, where would they get their water? ←Baseball Bugs What's up, Doc? carrots→ 10:55, 9 September 2018 (UTC)
 * From rain, deriving ultimately from the planet's oceans. I don't think anyone (else) in this discussion is envisaging a planetary surface 100% covered by forested land, but rather a planet whose land surface is so covered. If that land surface were confined to the temperate, tropical (in the geographical sense) and equatorial zones, with the Polar regions landless, 100% forest land cover seems feasible – I suspect even Earth has been in such a state for some periods in the past, such as during parts of the Devonian.
 * Then again, there's also Kelp forest.
 * Nor need we restrict our thought to planetary atmospheres, climates and ecosystems closely resembling Earth's. A somewhat denser atmosphere with a different composition, different patterns of circulation, and forms of life completely unrelated to ours could perhaps plausibly combine to allow "forests" at all latitudes – where's Hal Clement when we need him? {The poster formerly known as 87.81.230.195} 2.122.60.253 (talk) 00:16, 10 September 2018 (UTC)


 * Here are a few famous writings by actual scientists:
 * Search for Artificial Stellar Sources of Infrared Radiation, (Freeman Dyson, Science, 1960)
 * Pale Blue Dot (Carl Sagan, 1994).
 * Both of these are scientific evaluations that detail how planets appear from very far away. The short summary is that at astronomical distances, there is almost no way to reasonably measure or observe the presence of life - even if it manifests on a planetary scale as an Earth-like forest or city.  The primary method we might reasonably use to detect life on other worlds would be analysis of the electromagnetic absorption and emission spectra of a planet or a star.  One of the main efforts in the search for extraterrestrial intelligence is to characterize natural astrophysical electromagnetic emissions - radio astronomy - so that we might some day recognize an anomalous signal, if there is any such signal to be observed anywhere in our universe.
 * Nimur (talk) 01:36, 11 September 2018 (UTC)

Where is Dnieper arising from? Is its origin considered a wellspring?
Dnieper river is one of the impressive rivers of eastern Europe that goes through 3 countries: Russia, Belarus and Ukraine. My question is where does this river arising from? The article (Dnieper) here says that it is arising from Valdai Hills in Russia. What does it mean? Does it mean that its origin is a wellspring in fact? (I tried to find a picture of Dnieper's origin but I didn't find it.). I'm trying to understand what gives a supply of water to Dnieper, is it rain that directly falls on Dnieper or around it, or is it a huge wellspring in Valdai Hills in Russia that gives it its capacity?93.126.116.89 (talk) 05:14, 8 September 2018 (UTC)
 * If you read the article you linked to you would know that the source of the Dnieper is the sedge bogs (Akseninsky Mokh) of the Valdai Hills in central Russia.. The article includes a reference which will lead you to which confirms this: The source of the Dnipro lies in the northwest part of the Central Upland—in the Valdai Upland, at an elevation of 220 m, among turf swamps.. So the answer to your question is that the river's source is in bogs or swamps, not a spring. Bazza (talk) 12:17, 8 September 2018 (UTC)

Request article review: Levonorgestrel
Our article on Levonorgestrel is likely to be in the news in the next few days, based upon this news story:

I would like to request a review of the article and its sourcing to make sure that everything is accurate.

When it comes to medical topics, an electronics engineer like myself is pretty much lost (I have this mental picture of a non-engineer M.D. trying to "fix" our Cockcroft–Walton generator or Hall effect articles...), but the following quote from a citation in the article seems to my untrained eye be in conflict with WP:MEDRS, even though the source seems otherwise reliable.


 * "In 2002, a judicial review ruled that pregnancy begins at implantation, not fertilisation"

As I said, I have zero expertise here and am making no suggestions for specific changes. Its just that the above quote looks more political than medical to me. I just think medical questions should be answered through research, not judges and juries. --Guy Macon (talk) 14:32, 8 September 2018 (UTC)


 * Our article describes some debate over whether there might be a post-fertilization effect. If there is one it is not the major effect, but understandably those who think life begins at conception will be appalled at the possibility.  I have not done enough review - if it is possible at all - to tell if one point of view can be relegated to a fringe theory. Wnt (talk) 16:27, 8 September 2018 (UTC)


 * The article on emergency contraception though says several times that there is no post-fertillization effect and stresses the distinction between emergency contraceptives and abortifacients . Despite what the article says though at least one abortifacient, mifepristone, is also prescribed as an emergency contraceptive. Additionally, it notes that copper based spermicides almost certainly have abortive properties. 139.194.65.208 (talk) 03:04, 9 September 2018 (UTC)


 * Perhaps we need to take a close look at that article to make sure that the claims are backed up with WP:MEDRS compliant sources. The article claims:


 * "The best available evidence is that they do not have any post-fertilization effects such as the prevention of implantation"


 * But one of the sources cited in the article says


 * "To make an informed choice, women must know that ECPs—like the birth control pill, patch, ring, shot, and implant,76 and even like breastfeeding77—prevent pregnancy primarily by delaying or inhibiting ovulation and inhibiting fertilization, but may at times inhibit implantation of a fertilized egg in the endometrium".


 * I have no strong opinions on this topic, but I can understand why a religious person who believe as part of their religion that anything that gets between initial egg fertilization and delivery of a baby is a form of murder would be concerned. --Guy Macon (talk) 04:10, 10 September 2018 (UTC)
 * Honestly, reading the emergency contraception article it feels like it's imbued with a fairly deep ideological tinge, and doesn't adhere to WP:NPOV, but I'm sure my own POV is influencing that feeling. 202.155.85.18 (talk) 08:32, 10 September 2018 (UTC)


 * Seeing this debate, I took it to PubMed and came up with this review. They cite one study which found "There is no significant difference in the attachment of embryos following treatment with UPA compared with controls and no observable degenerative changes in the embryos."  They cite another two studies which finds "After 13 week of UPA treatment, the glandular epithelium appeared inactive, the glandular architecture was altered, and abnormal stromal vessels were also often observed."  However, the reviewers say "Thirdly, the authors that showed an endometrial suppression after treatment with the same SPRM utilized for treatment of myomas (Williams et al., 2012) did not demonstrate that this is also true for the UPA dosage utilized for EC."


 * It would seem like a reduction in implantation that is only 'significant' at higher doses than used, and which only affects fertilized embryos that are prevented by the true contraceptive effect, would be insignificant. Then again, religious people do things like separate their entire kitchen utensils into those used with meat and those used with milk based on the fear that they might accidentally boil a lamb in traces of its mother's milk, so I can kind of see how the doctrine of insignificant 'murder' might not be accepted. Wnt (talk) 13:16, 13 September 2018 (UTC)

Meth mouth, "krokodil", and phosphorus
I was just watching a documentary on the remarkable nasty effects of Russian homemade desocodeine desomorphine, called "krokodil" because the users' skin becomes badly infected and scarred. There is a good article about it here; the photos are intense. Apparently it is made the same way, the "Nagai route", as methamphetamine, which has been blamed for "meth mouth". Both can involve phossy jaw, a syndrome initially encountered from white phosphorus contamination of workers. White phosphorus causes that syndrome via its conversion to bisphosphonates, one very similar to a drug used to treat osteoporosis (in milder dosage!)

Now what's confusing me is -- what is the harmful substance that gets into the victims? (Aside perhaps from whatever the "krokodil" does to injection sites on the skin, most likely, which might be something as simple as acid-base)  I mean, I've mulled over a few ideas...

1. Red phosphorus. Lots of it is left in the homemade reactions, and users consume it. Problem: red phosphorus is supposed to be pretty much nontoxic as far as I know, which is why you find it on matchboxes or even inhaled.

2. White phosphorus back reaction. I was thinking maybe somehow the red phosphorus reaction could equilibrate backward and deposit white phosphorus as part of an equilibrium. The problem is, the Nagai route as far as I know goes from 2 P (polymeric) + 3 I2 -> 2 PI3 and PI3 + H2O -> PI(OH)2 + HI etc. until all the hydriodic acid is released. The first reaction is not reversible and the second quickly destroys the possibility of the product to go backward anyway.

3. Direct bisphosphonate production. According to that source above, white phosphorus can react inside the body to form bisphosphonates. So can the red phosphorus, under clandestine reaction conditions, form some kind of bisphosphonate with the organic compounds in solution? Problem: I'd have thought that this contaminant would be found in forensic analyses of the drugs.... though that might also be true of any other idea.

4. "Leftover" white phosphorus. The structure of red phosphorus is supposed to be amorphous. Is it possible that reacting it with iodine leaves over some tetrahedra, because they might be somewhat better "leaving groups" than the other potential units of red phosphorus, so that some is converted to white phosphorus after all?

I feel like someone should have worked this out, or at least that it can be worked out with the data available. There are methods like treatment with copper sulfate and silver nitrate that can decontaminate white phosphorus even on skin and so I wonder if they could also be applied to users or to the drugs before their consumption. Similarly, bisphosphonate would be expected to adhere to bone, so filtering through ground bone might remove it. Of course, I have no idea either is true. Wnt (talk) 17:06, 8 September 2018 (UTC)
 * You are mistaken: "krokodil" is desomorphine, not desocodeine. Ruslik_ Zero 19:03, 8 September 2018 (UTC)
 * Sorry! I looted that article for a figure to put in the other (it's on the synthesis pathway) and managed to confuse myself. ;) Wnt (talk) 12:56, 9 September 2018 (UTC)
 * The first article linked by Ruslik0 has a section on this specific question: Desomorphine. It claims:
 * Causes of this damage are from iodine and phosphorus (and other toxic substances) that are present after synthesis. Addicts often use readily available but relatively toxic and impure solvents such as gasoline or paint thinner during the reaction scheme, without adequately removing them afterwards before injection. Strong acids and bases such as hydrochloric acid and sodium hydroxide are also employed without measuring pH of the final solution and analysis of leftover solutions of "krokodil" in used syringes showed the pH was typically less than 3 (i.e. as acidic as lemon juice). Failure to remove insoluble fillers and binding aids from the codeine tablets used as starting material, as well as co-administration with pharmaceuticals such as tropicamide and tianeptine, are also cited as possible contributors to the high toxicity observed in users.
 * There's no inline cite for this para so it's hard to tell which of the sources is being used, but there are some for the section so it may be there.
 * On a side note, I would just point out that the relative non-toxicity of red phosphorus, compared to white phosphorus, doesn't necessarily make it a good idea to inject it. Hope that's not "medical advice". --Trovatore (talk) 22:01, 8 September 2018 (UTC)
 * I would imagine that even if meth mouth is in part due to the fact that the users are inhaling phosphorus, injecting phosphorus would have different effects most likely not localized to the mouth. That's obviously pure speculation though. 139.194.67.236 (talk) 22:15, 8 September 2018 (UTC)
 * You still get meth mouth if you inject.
 * "[Meth] users can go from having a sparkling smile to one of decay and tooth loss in about a year. For one, the drug dries out a person's salivary glands leading to the cottony-mouth feeling. Without the diluting effects of saliva, the acids in your mouth--produced by various foods and bacteria--begin to eat away tooth enamel.
 * Adding fuel to this mouth decay, meth users may forget to brush their teeth. Whereas the effects of cocaine last about an hour, a meth high can linger for 12 hours. During this half-day high, personal hygiene may not be at the top of the list of things to do.
 * The extensive tooth decay of meth mouth is attributed to the drug's dry-mouth effect and its propensity to cause cravings for high-calorie carbonated beverages, tooth grinding and clenching, and extended periods of poor oral hygiene"
 * I know, that's why I was specific to the effects of phosphorus, assuming there are any. In everything I've read on the matter previously, meth mouth was attributed to the dry mouth, teeth grinding and poor hygiene you mentioned. I've never heard of phosphorus being involved. 139.194.65.208 (talk) 02:58, 9 September 2018 (UTC)
 * The same article also implies that pure desomorphine injected with a sterile syringe will be relatively harmless though highly addictive. People can live for decades injecting it regularly. Ruslik_ Zero 20:47, 9 September 2018 (UTC)
 * The same is true of all opioids routinely used in humans (whether injected or otherwise administered). Opioid overdoses are usually the result of 1) administration of impure or uncertain quantities of drug(s), as in street drugs which are usually contaminated, or may not even be the purported substance; 2) co-administration with other drugs like benzodiazepenes or alcohol. --47.146.63.87 (talk) 07:58, 11 September 2018 (UTC)

During evolution what was the fovea good for?
Modern humans use the fovea for reading and driving. This can be extracted from the corresponding article. But all this time before the invention of writing systems or cars, what was the fovea good for? Shouldn't this go into the article? — Preceding unsigned comment added by 31.4.141.17 (talk) 22:48, 8 September 2018 (UTC)


 * Does our article on Evolution of the eye answer your question? --Guy Macon (talk) 22:52, 8 September 2018 (UTC)
 * The word "Fovea" does not appear in that article. ←Baseball Bugs What's up, Doc? carrots→ 23:45, 8 September 2018 (UTC)
 * No, it does not. 31.4.141.17 (talk) 01:27, 9 September 2018 (UTC)
 * The existence of the fovea is implied in the discussion about the development of the lens. A lens to focus fine details and a part of the eye optimized for seeing those fine details go hand in hand.
 * As for the implied question "why is sharp vision better than blurry vision", it help one to find prey, fruit, etc that is far away, it stops you from bedding down on an anthill, and it helps in recognizing facial expressions, especially from across the room cave. --Guy Macon (talk) 01:56, 9 September 2018 (UTC)
 * One might argue that the fovea saves having to devote as much brain volume to processing vision as have a whole retina that was as sharp as a fovea. Abductive  (reasoning) 03:11, 9 September 2018 (UTC)

The fovea has curiously been gained and lost several times in the evolution of animals. I recommend this article:. Someguy1221 (talk) 05:45, 9 September 2018 (UTC)


 * The reason, the article (Fovea centralis?) does not go to deep into the general use from evolutionary perspective, may be that it would be to speculative. There is some hint towards hunting since the anterior lateral eyes of jumping spiders seem to be of similar function but with a very different construction. Like many other carnivores they also have the (focusing) eyes aligned for a rather limited, pure frontal field of view compared to most herbivores who have their eyes on the sides to achieve an almost completely field of view all around them, so predators can not openly sneak up on them. --Kharon (talk) 06:13, 9 September 2018 (UTC)