Wikipedia:Reference desk/Archives/Science/2016 April 25

= April 25 =

Why do we sometime listen a sharp beep sound for some period of time?
I really got scared when I first time noticed a beep sound and I asked with my other friends about it and they also told that they have also experienced it but we don't know the reason. Please help. — Preceding unsigned comment added by Sahil shrestha (talk • contribs) 16:08, 29 April 2016 (UTC)

Could it be that a person can stop his pulse or is it fake?
This video (around the minute 6:30) shows how a person stops his pulse for 15 seconds. I just would like to ensure if it's possible (true) or not fake). 93.126.95.68 (talk) 00:29, 25 April 2016 (UTC)
 * Supposedly Superman can. But how would a mere mortal stop his heartbeat and live to tell about it? ←Baseball Bugs What's up, Doc? carrots→ 11:02, 25 April 2016 (UTC)
 * This and this may be relevant. The simple method is to simply hold a rubber ball in the right spot under the arm to cut off the blood flow to the wrists (how most people measure the pulse).  Doesn't affect heartrate at all.  The harder method involves training the muscles throughout the body to slow blood flow (though this does not actually stop the heart).  Does affect heartrate, and could be combined with the rubber ball trick to make one appear totally freaking dead (as long as they're checking the pulse from the wrist).  If they had attached monitors somewhere besides his finger tips (I'm not counting a credulous hand as a monitor), they'd've spotted it.  Ian.thomson (talk) 11:24, 25 April 2016 (UTC)
 * Great answer! thank you 93.126.95.68 (talk) 18:01, 25 April 2016 (UTC)


 * I would be skeptical because cardiac muscle is spontaneously pulsatile. External nerves govern the rate, but have they evolved to make it stop?  Nothing's impossible in biology but some things seem pretty darn unlikely, demanding good evidence. Wnt (talk) 20:38, 25 April 2016 (UTC)

Trying to identify a berry
My fiancee and I live in the Seattle area, and we came across some orange relatives of the blackberry that grow very low, a type of ground cover. She called them salmonberries, but we've now discovered that that name refers to Rubus parviflorus, an obviously related but clearly different species. The last time I saw them was at Saint Edward State Park growing at the base of the walls around the old seminary building. She indicated that there are also patches of them near SeaTac. It's possible that these are Rubus spectabilis, but the description on that page indicates a taller shrub with substantial height. The orange berry image on that page, however, appears accurate, though the red is clearly the wrong berry. Is it possible that these are just smaller versions of the same plant, or is this a different species? 73.19.23.200 (talk) 11:57, 25 April 2016 (UTC)
 * Maybe some kind of Euonymus? -- Jayron 32 12:55, 25 April 2016 (UTC)


 * It would appear that both parviflorus and spectabilis are sometimes called salmonberry (which is why biologists prefer the Latin binomials rather than the common names). Don't put too much weight on the described size of the plants: any shrub can end up being stunted if the conditions are not right. Planted up close to a wall may mean little soil, or in a coastal area the effects of salt winds might reduce plant growth. If flower, fruit and leaf match that counts for more than the general shape and size of the whole plant. 81.132.106.10 (talk) 13:47, 25 April 2016 (UTC)


 * Just for the fun of it, check out dewberry - another Rubus species complex. . SemanticMantis (talk) 14:11, 25 April 2016 (UTC)
 * Also, in general, the way to ID a berry is not through the berry or the bush shape, it's by the flower. SemanticMantis (talk) 14:14, 25 April 2016 (UTC)
 * Unfortunately, if they are seeing the fruit, it is probably the wrong season to spot the flowers. 81.132.106.10 (talk) 16:02, 25 April 2016 (UTC)
 * Phenology varies quite a bit. Also it's not that odd to see flowers and berries on the same plant at the same time . Also this general advice may be useful for next season, or to ID other berries :) SemanticMantis (talk) 16:40, 25 April 2016 (UTC)
 * Asked this question a couple of other places, and one suggestion was Rubus chamaemorus. I'll take a look at the flowers next time I see one, though.  73.19.23.200 (talk) 05:07, 26 April 2016 (UTC)
 * Thanks for the follow-up. Rubus is tough to ID to the species level, in my opinion. SemanticMantis (talk) 13:36, 26 April 2016 (UTC)

Eye damage due to eye exams
An eye exam seems to involve them shining bright lights into a fully dilated eye. Couldn't they use a dim light, paired with a highly light-sensitive digital camera, instead ? StuRat (talk) 20:59, 25 April 2016 (UTC)


 * What eye damage? ←Baseball Bugs What's up, Doc? carrots→ 22:13, 25 April 2016 (UTC)


 * Well, the most "classic" exam you see in movies and TV all the time when a doctor shines a pen light into someone's eye is a Pupillary light reflex test, which is not an eye exam but a neurological test. Apart from that, while a bright light can be uncomfortable and leave you with spots in your vision that can last a while, it doesn't actually damage the eye, it's actually the heat and radiation from something like the sun, welding arc, or a powerful enough laser that cause damage to the retina, just a "bright light" is typically not enough. disclaimer: Don't use this as an excuse to stare into extremely bright lights, it's still not a GOOD idea even if it doesn't cause permanent damage. Vespine (talk) 00:03, 26 April 2016 (UTC)


 * Indeed. See Photokeratitis for our relevant article.  It's the ultraviolet that does the damage, which shouldn't be an issue with an opthalmoscope. Tevildo (talk) 00:05, 26 April 2016 (UTC)


 * Here is a 1980 paper: Retinal light exposure from ophthalmoscopes, slit lamps, and overhead surgical lamps; An analysis of potential hazards
 * "The indirect ophthalmoscopes tested appear to be "safe" under moderate voltage settings, provided exposure is reasonably brief Slit-lamp biomicroscopy of the fundus, however, merits caution. It produces a three-times-higher retinal irradiance than the indirect ophthalmoscope."
 * Links: Slit lamp, fundus (eye). -- ToE 02:58, 26 April 2016 (UTC)


 * How about just to avoid spots in the eyes, then ? StuRat (talk) 02:02, 26 April 2016 (UTC)


 * Why care? The payback in terms of cheaper equipment and hence lower eye examination costs by far outweighs a few spots that'll go away by the time you've left the building anyway. SteveBaker (talk) 15:28, 26 April 2016 (UTC)


 * Well, like gynecologists that use ice cold speculums, it's an issue of caring about your patient's comfort. If you need a medical reason, some patients may avoid eye exams because of the blinding light, and suffer medical problems as a result.  If you want a business reason, the "no blinding light" exam could be a selling point to acquire new patients, and then sell them glasses and contact lenses.  StuRat (talk) 19:23, 26 April 2016 (UTC)
 * "Ice cold"? Cosby talked about how doctors keep their stethoscopes in the freezer. But I'm fairly certain he was exaggerating. ←Baseball Bugs What's up, Doc? carrots→ 10:41, 27 April 2016 (UTC)


 * And if they don't go away in a reasonable time, you had best make another appointment. ←Baseball Bugs What's up, Doc? carrots→ 15:47, 26 April 2016 (UTC)

Thanks for all the replies so far, but nobody has directly answered the Q as to whether it is possible to do an eye exam using a dim light and an extremely light-sensitive digital camera. StuRat (talk) 19:29, 26 April 2016 (UTC)


 * Before an eye exam, my opthalmologist has his nurse routinely take a digital camera photograph of my retina. That is neither rocket science nor a novel idea. However the eye is a 3-D structure and the opthalmologist uses his Slit lamp and microscope to investigate throughout the structure. Symptoms of problems such as scratched cornea, floaters or Retinal detachment which are vital to catch early will be discovered by skilled search at different focus distances, magnifications and positioning of the analysis light. Given the importance of the eye diseases that slit lamp exam detects there is no reason to restrict the analyst to work from a single 2-D photograph because of an unfounded fear of a few seconds exposure to the light of the properly calibrated medical instrument, though nervous children may need reassurance that nothing bad is happening. AllBestFaith (talk) 07:38, 27 April 2016 (UTC)


 * Why just take a single image ? You could take multiple images from different angles and even use that to form a 3D computer model. StuRat (talk) 14:30, 27 April 2016 (UTC)

Painting the Moon
Wikipedia has a harebrained scheme to send a draft of the encylopedia to the Moon. I want to see the idea improved on with this invention, which claims to keep 360 TB stable for 13.8 billion years. With that kind of stability, you can leave a message for some future species that is trying to figure out what Earth was like, even if the planet has been entirely resurfaced like Venus after some man-made climate mishap.

The catch is, how do they find the disk? It should gradually sink into the regolith. (of course, it could get hit by a meteor directly, but I'm assuming luck or multiple scattered disks laid over time)

On to the question: is it possible to take some freaky, rare element, I dunno, lutetium or something maybe one of the tracers described in File:Rareearthoxides.jpg, and spray a small amount of it on the Moon, and taint the small area where it lands so thoroughly that it can be detected from an orbital survey, and have micrometeorites hitting anywhere in the small area constantly stirring it up, so that the mark never fades? What stands out the most, and can the logic here hold or is it doomed to be diluted into invisibility? Wnt (talk) 21:02, 25 April 2016 (UTC)


 * Rather than make it visually obvious, how about placing a strong, permanent magnet there ? Probably not detectable from space, but some future aliens might notice the disturbance of the magnetic field when exploring the surface near the area. StuRat (talk) 21:33, 25 April 2016 (UTC)


 * In Tycho, of course. ←Baseball Bugs What's up, Doc? carrots→ 22:11, 25 April 2016 (UTC)


 * Why ? StuRat (talk) 22:30, 25 April 2016 (UTC)


 * To turn the tables on a key plot element of 2001: A Space Odyssey. ←Baseball Bugs What's up, Doc? carrots→ 22:35, 25 April 2016 (UTC)


 * To be clear, I was hoping that a small quantity of rare earth, even a mere kilogram might suffice to create a notable spectroscopic anomaly on the order of ten meters wide that can withstand the gradual tilling of the regolith by micrometeorites over millions of years. (a large impact would vaporize the disc, so there's no sense worrying about it).  Whereas a buried permanent magnet would definitely involve an impractical amount of mass to be noticed. Wnt (talk) 00:21, 26 April 2016 (UTC)


 * I would expect anything flat on the surface would quickly be covered with dust and rendered invisible. Can anyone estimate the distance at which a one kg permanent magnet, on the surface of the Moon, could be detected ?  StuRat (talk) 01:44, 26 April 2016 (UTC)


 * When you say "quickly", do you mean on a planetary timescale? The moon is relatively inert now, except for the occasional small meteor strike, of which the moon attracts relatively few, compared to the earth. The lowest estimates I have found of how long the footprints left by the astronauts will last is several tens of thousands of years, the longest is many millions. Vespine (talk) 02:42, 26 April 2016 (UTC)


 * Yes, on a planetary timescale. How long would the permanent magnet last ? StuRat (talk) 02:56, 26 April 2016 (UTC)


 * Another thought is to just move the Moon dust around to write something there, like a big arrow pointing to the Wikipedia archive. Deep enough furrows ought to last for millions of years, based on how long it would take for the footsteps to fill in.  StuRat (talk) 03:00, 26 April 2016 (UTC)


 * Impact gardening by micrometeorites is estimated to overturn the top 1 cm of the lunar surface every 10 million years. Dragons flight (talk) 09:30, 26 April 2016 (UTC)


 * So does that mean a 1 meter deep furrow would last a billion years ? Somehow I doubt if it's as simple as that. StuRat (talk) 14:41, 26 April 2016 (UTC)


 * The practical problem with this is that of launch weight. While the effort to put a privately-funded lander/rover on the moon may be able to accomodate a tiny memory chip weighing a fraction of a gram - it's not going to be able to carry a 1kg magnet or something capable of making giant arrows or deep furrows.  The memory chip will remain attached to the lander - and that's probably going to be tens of centimeters tall - so the 1cm/10My number should keep it above the surface for a few hundred millions of years.  To detect it from orbit might be tricky - but probably the best chance is to put a retro-reflective surface on the top of the entire machine...sadly, that's likely to be impossible for the reasons described above.


 * I'm always deeply skeptical of these efforts to put stores of knowledge out there for aliens to find. In the case of a memory chip, it's not going to survive all of the radiation and freeze/cook cycles it'll go through - and even if it did, it's unlikely that aliens would figure out how to power it up and what protocol to use to extract the data and so forth.   Probably the most valuable thing they could find would be the lander/rover itself - and for that purpose, we already have the six moon landers scattered over the surface of the moon - plus numerous other landers and rovers put out there over the last fifty years.


 * "We existed and had technology of this level" is probably the best and only message we can leave. Given the extreme difficulties of interstellar travel, it's really quite unlikely that aliens will visit our solar system anyway.


 * What Wikipedia is doing is properly called "A Publicity Stunt" - and if we're completely honest about that - and treat it as such, it has some value. People still talk about Voyagers' "golden record" - and "Wikipedia on the Moon" will continue to pay back our efforts over the coming decades as science documentaries talk about it - and that'll drive more (human) traffic to our site.  It really doesn't much matter what we send - nobody will care about the exact content a decade from now.


 * To get the maximum bang-for-buck, we should probably invite the general public to nominate articles to go to the moon - sure, we'll get a bunch of junk - but it really doesn't matter.


 * SteveBaker (talk) 15:24, 26 April 2016 (UTC)

The disc is glass with internal defects that supposedly can endure a long time. I doubt that it can be as resilient as the zircons people use to probe what happened in the Archaean, but I would not rule out an ability to survive freeze/thaw cycles, especially if it is an internal space shielded from direct sunlight. And while a space probe may tell *something* about life on Earth, it is not nearly so informative as a picture of Shanghai or a koala bear or a baseball game. Given time and intelligence, substantial amounts of the text may be decipherable. It is also possible (and more of a motivating force) that the content may be of great interest in mere centuries from the present time. The human race has a bad history of censorship and the destruction of libraries. While it may seem that information transmission has the upper hand, consider the future availability of AI that can write totally made-up articles about any topic with internal consistency, complete with a whole fake comment section in which all the various factions of AI bots carry on a pretend debate while any human is lost in the bulk of it. So it is possible that this kind of well-dated, well-preserved archive, placed away from Earth where future generations may be unable to get at it and falsify it, might one day be of supreme interest. Wnt (talk) 17:00, 26 April 2016 (UTC)
 * If you go to the discussion page Meta:Talk:Wikipedia to the Moon, you'll see you're not the first person to mention the 360TB (I think it's been mentioned at least 3 times independently in various places there and in proposals area). The team is already aware of it, I think from before the advertising. It's been looked at but currently they've chosen the 25GB M-DISC because it seems to be the best one with some decent testing behind it. (Mostly for earth based storage rather than space/moon surface but still...) While I think it's true the general idea of sending the (I think multiple) discs with various content (not just the 20GB offered to Wikipedia) is about publicity, they also not surprisingly want something which at least has a chance of being read in a few decades, hopefully centuries or more just in case. (So something like an flash memory as a lot of people seem to be proposing is definitely out.) For that reason they've leaning towards the 25GB M-DISCs rather than the 100GB ones or the 360TB research disc. I say research for a reason, I've you been paying attention as long as I have which at 17 years or something isn't that long, you'll know how everyone is always coming up with this super technology which can store X amount of data but then is barely heard of again. (As with many other areas of technology where there's some claimed superb invention.) Most of these may have been because they could work out a way to turn it into a consumer product which probably doesn't matter so much. However there would still be need for something was can be reliably produced in the time frames needed and for a resonable price. Going to the moon is expesive, but I suspect they can't afford to throw away e.g. $250k on a disc unless someone else is willing to pay for it. In this particular case they're also claiming very long life spans, but while rarer I think I've seen that before too. They could change their minds but ultimately it's their project so their decision and they have their reasons. The M-DISCs also have the advantage of simplicity of reading compare to the 360TB research disc. I think they're more thinking of humans but either way while you may assume anyone who is smart enough to find the disc would be smart enough to be able to read it and willing to spend the time and effort. But they would have to know it's something to read. Additionally, I suspect the most likely thing if it is ever read, is for it to be read in perhaps a few decades or centuries to confirm what's on it. In that case, the easier it is to read, the more likely someone is to bother. In the case of the research disc or something similar, it's one thing that could actually be worth adding as an extra, so perhaps they'll do that if they can find the space and volume. It's very small and light so I assume they probably could find something. If my understanding is correct and there are multiple M-DISCs planned they could potentially remove one or more if it fits with whatever they planned to store on it. (I don't know the history but I'm guessing the M-DISC and other options were probably something they started to look in to long before February so the 360TB is still new.) BTW as for SteveBaker's point, I'm pretty sure getting non editors (or very irregular editors) involved was a reason for the site wide advertising. I strongly suspect there'll be more come June 10 when the voting starts. Nil Einne (talk) 19:13, 26 April 2016 (UTC)


 * The glass disk approach isn't going to work either. According to M-DISC "Millenniata claims that properly stored M-DISC DVD recordings will last 1000 years." - so improperly stored...what? 10 years? 100 years?  Certainly not enough to be worth the effort.  We have 20Gbytes - that's not much.  I don't think we'll be sending too many fancy high-rez photographs.  A photo of a Koala bear might as well be a bunch of random pixels if you don't know what you're looking at.  Especially if we also include articles with things like teddy bears in them...it would be alarmingly easy to confuse the aliens.  But it's not going to last long enough to matter.  It's a publicity stunt and nothing more...which is not to say that it's a worthless activity - just that if you're putting it there for aliens to read then you're kidding yourself.  Putting it inside the great pyramid of Giza would give them a better chance of finding it after the zombie apocalypse wipes us all out. SteveBaker (talk) 19:26, 26 April 2016 (UTC)
 * But why do people keep bringing up aliens? The FAQ itself says it's not very likely and the primary goal is humans. As for zombie apocalypse, again this seems a bit of an extreme example. With the way the internet etc works nowadays, it seems unlikely that someone could say semi-secretly modify the bible as almost definitely happened before publishing. Dumping it in the Great Pyramid of Gaza seems a little rude. I'm sure you could find somewhere else, but still guaranteeing your time capsule on earth isn't modified, particularly if it's widely publicised is a little harder. Until and unless regular moon visits or even moon base are a thing, it's a time capsule that we can be fairly sure isn't modified. So by that token checking the contents in decades or may be centuries seems at least nominally interesting. Particularly perhaps checking our records of what was sent. This doesn't change the fact it's largely a publicity gesture as I said above and elsewhere, but it does mean thinking of it as solely a publicity gesture and not something that will ever be looked at in the future is as I said above IMO a mistake. All this assumes it even makes it to the moon intact, which probably isn't that likely. (Of course the other thing is the process of selection and selection is probably significant and may be interesting in the future, but to get that you need to have a catalyst for the selection.) P.S. What glass disc are you referring to? The M-DISC composition is a trade secret but AFAIK is normally called ceramic or stone. Our article says Glassy carbon which suggests either ceramic or carbon or perhaps glass-like carbon would be resonable. I guess you could call it glass, but this may be best avoided since the term is often used restrictively enough that it won't apply to glass like carbon. The 360TB disc is AFAIK often called glass or quartz, but it's claimed to last billions of years however as I said above it's a research project so such claims have more scepticism. P.P.S. Rereading the talk page, I remember now the specific claim was the testing for the 25GB M-DISC qualfies it (I guess in the opinion of the PTS) for use in space. I'm not sure what testing this is as I couldn't find any specific mention, but it's difficult to search for obvious reasons. Something else I read a while ago in the talk page which seems to be confirmed by is that the biggest risk (on earth and probably in space) is the polycarbonate outer layer. This would likely be significantly affected by conditions on the moon surface so I expect decades may be more resonable. Technically I wonder how easy it will be to replace this layer, or simple read without it. Realisiticly it doesn't seem likely anyone is going to be using a bog standard BD-ROM drive centuries from now. And unless the 360TB tech really takes off, it seems very likely it'll be far easier to read than that. So I stick by my earlier point, getting someone interested enough would likely be easier than with the 360TB disc and it may very well still be possible in centuries. The next concern is the glass like carbon recording surface. It seems this is susceptable to oxidation over millinea so that shouldn't be much of a concern. However I'm not sure how well we know how something like that will survive in space (or specifically on the surface of the moon). Nil Einne (talk) 20:20, 26 April 2016 (UTC)
 * It may be a research project, but it is also possible that this invention will go by the wayside for purely commercial reasons. So this may be the first time and the last that a medium holding this much storage for that much time can be sent to the Moon.  It could be worth taking the risk on the new technology. Wnt (talk) 21:33, 26 April 2016 (UTC)


 * If we are talking about marking the moon for real (and not as part of some publicity stunt), then I would suggest your best strategy would be to design a long-lasting rover type robot to slowly lay down a large geometric design of a colossal scale. Something similar the the Nazca lines.  A pattern that is large enough and deep enough should survive billions of years on the moon.  Dragons flight (talk) 21:49, 26 April 2016 (UTC)