Wikipedia:Reference desk/Archives/Science/2016 July 8

= July 8 =

That thing that squishes dough
Does anyone know the common name for this? It is used in China and elsewhere to knead dough. Anna Frodesiak (talk) 08:52, 8 July 2016 (UTC)


 * The term rolling pin is pretty ubiquitous  in the English speaking world.--Aspro (talk) 11:18, 8 July 2016 (UTC)


 * It's a fiener - I think that's the Yiddish term for them, when they're used for working matzah. They're quite specific to the types of dough they're used with. Most bread making uses a dough hook to emulate hand kneading and the stretching of dough, but a fiener instead squashes the dough. I think this type of squash kneading is only used with unleavened doughs, such as matzah and noodles.
 * A rolling pin should work the dough as little as possible. It's for shaping the dough flat, not kneading it to change its properties. Andy Dingley (talk) 11:27, 8 July 2016 (UTC)


 * I agree with AD. One is not trying to activate the gluten (takes too long). One is just making it a consistent and well textured dough. Same with some noodles. Wheat noodles can be stretched by hand because the gluten has be activated but others are extruded (like spaghetti). But Fiener is a term exclusively for matzah. This is why I suggested rolling pin to cover all nationalities. (Note: I hasten to add that I'm not referring to 'real'  spaghetti which as every one knows comes from  the Spaghetti Trees of Europe  but to the extruded stuff Americans buy from their supermarkets  BBC: Spaghetti-Harvest in Ticino.


 * There must be an English name for it.
 * It doesn't roll, so it can't be a rolling pin or even a type of rolling pin.
 * I know someone who was totally fooled by the spaghetti harvest hoax video.
 * Nothing in the Yiddish-English dictionary.
 * I may write to a baker and ask.
 * I am an avid baker and two secrets to good bread are a bit of milk in the dough for a fine crumb, and letting the whole thing rot for 24 hours or so (which doesn't have anything to do with ''sour...", just develops flavour).


 * Thanks all. :) Anna Frodesiak (talk) 01:00, 9 July 2016 (UTC)


 * In the case of this bread, one can not leave it to rot for 24 hours, as it will start to ferment and thus won't be matzah. If they used traditional 'wooden sticks' (wooden rolling pins) they would have to be cleaned by sand-papering between each  batch of dough (in order to comply with tradition of no fermentation) (it is unleven bread after all). That takes time, so  stainless steel rollers are therefore more efficacious. Second: Who says It doesn't roll? How does one flatten a dough without rolling, either with a rolling-pin or  a mangle? Don't  “may write to a baker and ask” do it and report back here please. --Aspro (talk) 20:33, 9 July 2016 (UTC)


 * Hi Aspro. Thanks for the interesting reply. Sure, rotting would not be so good for matzos, but it is for bread. The ones used in China are large and do not roll. They are used in and up-and-down motion to knead the dough. What's a "mangle"? I did not suggest I would report back here, but why not? I checked baker's sites, but the big ones seemed to all be lobbying groups. Best, Anna Frodesiak (talk) 23:01, 9 July 2016 (UTC)
 * Mangle (machine). --Tagishsimon (talk) 23:06, 9 July 2016 (UTC)


 * Thanks, Tagishsimon. I'm not sure if that's the same thing because it's used for laundry and usually works by rolling. Then again, the last three images below seem like just heavy things to push down on rollers, and there is no anchor point for leverage.


 * By the way, I'm asking all of this because I thought I'd expand the kneading article or possibly make a standalone.


 * Anna Frodesiak (talk) 06:58, 10 July 2016 (UTC)

Hepatitis B carrier can bring children without to transfer them his virus?
A man has an hepatitis B and his wife doesn't have hepatitis at all, and they want to bring children. Is there any way to make it safty without to transfer it to their child (Eccept of IVF)? 194.114.146.227 (talk) 09:10, 8 July 2016 (UTC)
 * In your hypothetical couple, your question is "is hepatitis B virus transmitted via the male germ line?". Given this study, the answer would seem to be no.  If a child is born with hepatitis B, it's because the mother is infected and has transmitted it to the fetus.  It might be worth mentioning that there are medical options available for mothers who are hepatitis B positive that may prevent hepatitis in their children, which generally would involve giving immune globulin and hepatitis vaccine to the newborn child.  But any non-hypothetical couple would surely consult their physician to get medical advice before proceeding.  After all, if the man and woman are having sex, he should be concerned about transmitting Hepatitis B to his wife. And she could be vaccinated to prevent her from becoming infected, and if she doesn't become infected, neither will her future fetuses. This is known as "pre-conception hepatitis B vaccination".- Nunh-huh 10:27, 8 July 2016 (UTC)
 * The wife should be vaccinated against hepatitis B regardless of any intention to have a child - just to prevent infection, which may cause long term health problems. Ruslik_ Zero 16:54, 8 July 2016 (UTC)
 * This sounds awfully like a request for medical advice ("I have this friend who has Hepatitis B..."). Anyone who has questions regarding a health condition they have should consult a health care professional. --71.110.8.102 (talk) 20:50, 8 July 2016 (UTC)
 * It's actually a request for medical information. Not the same thing. - Nunh-huh 23:35, 8 July 2016 (UTC)
 * I absolutely disagree with you--to me it seems like a question very likely being asked by someone with a real stake in the answer to their questions--and anyway, whenever the nature of a question leaves that possibility at all open, longstanding WMF legal policy, local consensus and basic common sense and respect for the well being of the OP all direct us to refer them to a medical professional. Especially when we are talking about someone who clearly has limited comprehension of the language we are all writing our responses in.  What if he all the op clearly takes away is your statement that the father cannot transmit the disease.  With your further clarification in later sentences, your meaning becomes clear, but frankly that's a bizarre way to answer that question even for a native English speaker.  Of course the disease isn't passed down through the germline; it's a sexually transmitted disease, and presumably the OP knows the distinction since they realize IVF is an option.  But clearly any father could easily infect the mother during efforts at conception and, thereby, the child as well.  That's a risk the OP should be aware of but you went quite a bit deeper, re-wording their question and then dumping a fair bit medical information ranging from the means of infection to vaccines, much of which the OP will probably not fully process, given the language divide.  Now, this does seem like to be a "first stage" kind of inquiry looking for methods they can broach with a doctor, but, meaning no offense to your good-faith intention to provide accurate information here, this is still exactly the kind of advice we are meant to avoid giving and exactly the situation where it's most obvious why.   S n o w  let's rap 02:08, 10 July 2016 (UTC)
 * Actually, until recently it was thought that it was possible to pass sexually transmited diseases such as syphilis from father to fetus without infecting the mother—and one still encounters muddled thinking along this line in modern historical writing that suggests syphillis caused miscarriages in Henry VIII's wives— so my way of answering the question wouldn't be thought to be "bizarre" to most people. And it certainly wasn't "bizarre" to those who investigated it in the 2013 paper I cited, or to the journal editors who published it. - Nunh-huh 11:37, 10 July 2016 (UTC)
 * You've completely misinterpreted what I found "bizarre" about the nature of your answer and are now basically arguing the same point as I was; my point was that to say that the father "can't infect the child" simply because he won't be doing so in a direct fashion (but can infect both mother and child) completely misses the point of the OP's question, which was about the overall outcome concerning whether the child would become infected as a result of efforts at conception, not an inquity as to whether the father infected the child in a technical sense. Your answer does not in fact respond to the OPs original question, but rather your re-phrasing of that question into your own terms, making it about whether the father can infect the child directly, as opposed to the OP's inquiry as to whether the child will be infected at all; and all of this done with very little chance that the OP will understand the distinction when they clearly struggle with basic English grammar and syntax.


 * But this is all incredibly incidental to the main point of my comment, and every little bit of this parsing of semantics only underscores the reasons why we do not here allow ourselves to step into the role of doctors and provide medical advice. Honestly, your answer would be a perfectly serviceable one if we were discussing this matter in the abstract, but we're not talking about Henry VIII's children--we're talking very possibly (indeed, very probably) about a real couple struggling with a medical complication to their plans to build a family, which falls as precisely within the prohibition on medical advice as any question I've ever seen here.  This is the last bit of commentary I will provide in this thread; if you think there is something novel to the perennial debate on medical advice worth pursuing here, I am at your disposal on the talk page, though I doubt we're going to create any seismic shift on the general consensus of that matter.  But we do need to stop providing any direct advice here.  S n o w  let's rap 23:18, 10 July 2016 (UTC)

Bristles on Zora
Hello! I found a Zora species in Ireland, and I would like to identify it. In [this key], it asks in couplet 1 how many bristles it has on its first and second metatarsus. Anybody have any ideas as to what the differences are between setae, spines and bristles? Thanks, Megaraptor12345 (talk) 12:54, 8 July 2016 (UTC)
 * The Zora are piscine humanoids. Going by seta and spine (zoology), setae and bristles are synonymous for (basically) "hair" (i.e., flexible) while spines are rigid. I am not sure how that distinction applies in your context though. Tigraan Click here to contact me 14:24, 8 July 2016 (UTC)
 * Zora Rach, on another hand, is a mountain. —Tamfang (talk) 08:49, 9 July 2016 (UTC)


 * Well, apparently specimens of individual species within certain subfamilies of Zorinae are generally very difficult to tell apart without high-resolution images of the genitals; note that our article is worded in such a way as to suggests that all members of Zorinae are difficult to tell apart without these genital morphologies, but clearly there can be substantial differences between members of certain subfamilies those of certain other subfamilies. Anyway, it's not unheard of for the differenation of species requiring this detail, when it comes to spiders, either because multiple closely-related but genetically distinct species still share a common morphology or, conversely, because specimens identified as genetically within a species vary some in the phenotypes of their superficial morphologies. Anyway, it would seem this is the ideal method with regard to members of the Zora subfamily, judging by how much attention is focused on the pedipals and seminal recepticals in the source you provided and [other arachnological guides].


 * All of that said, I'm rather guessing that you don't have extreme resolution images of this particular zora's hoo-has, and are doing the best with the guidance you have on larger distinguishing features? That may prove impractical for the reasons described above, but I will give you what context I can for the terms you inquired about, though the problem is that all of them are rather broad biological terms that, even within the context of taxonomical arthropodology, have been used inconsistently.  Still, generally setae in insects and arachnids are small hair-like appendages which appear (and may or may not be) flexible.  They can appear together in a clustered fashion, you can generally make out their individual bases, which is one of their main distinctions from bristles, which often present in closely packed structures.  Setae and bristles both serve functions that vary from the harvesting, hunting, production, or consumption of food, mating (either as part of the actual conceptual anatomy or as markers in sexual selection), various mechano- and chemo-receptive sensory roles,  kin identification and so-on.  Spines tend to be quite a bit thicker (especially at the base), but generally taper to a point, and are almost always much fewer in number than those features identified as setae or bristles.   They can serve in several of the same functions as those listed above for setae and bristles, but they are typically a more rigid, larger and obvious part of the carapace.  Those, at least, are the general features I associate with each, but they may be somewhat idiosyncratic to my experience; entomologists/arachnologists working in particular areas might have more specific criteria, be they morphological or functional.  Maybe  can shed more light on this?  S n o w  let's rap 03:12, 10 July 2016 (UTC)

Californian bird that smashes snails?
I live in Southern California, and last year around Christmas I found a bunch of broken snail shells at a local park. (photo) The way they're broken looks similar to those crushed on rocks by the British song thrush. Could these shells I saw have been smashed by a local bird in a similar way? There were lots of American robins and a few hermit thrushes around when I found those smashed shells, so I was wondering if they break snails like song thrushes do. 2602:304:B041:2949:E9C7:FF65:AF81:67C2 (talk) 14:25, 8 July 2016 (UTC)
 * In addition to the song thrush that you mentioned, see Common blackbird. This bird exists in North America and many other places, including New Zealand, where I frequently hear and see them smashing snail shells against my wooden deck. Akld guy (talk) 00:22, 9 July 2016 (UTC)
 * The page says those blackbirds have only been spotted in Canada, though. I doubt there are any in California. But your observation implies that this snail-cracking behavior may be shared by several species in the genus Turdus, which includes the American Robin. 2602:304:B041:2949:E9C7:FF65:AF81:67C2 (talk) 03:02, 9 July 2016 (UTC)
 * Our Kanab ambersnail article lists the American robin as a predator, but it doesn't say if it smashes the shell. Alansplodge (talk) 18:51, 9 July 2016 (UTC)

Bombs used by US police
In 1985 the Philadelphia police dropped a bomb or bombs on a building held by MOVE activists, causing an explosion and fire which killed 11 people and a fire which destroyed 65 buildings. In the recent Dallas police shootings, the police used a bomb robot to carry a bomb to the location of a shooter and blow him up, without destroying the building or neighborhood. Do US big city police departments have bombs or grenades as part of their official equipment? Do they have RPGs, or other military weapons designed to kill perpetrators when automatic weapon fire is not enough? It seems chancy to expect them to just build a bomb and detonator on the spot. The Move case might be considered as an attempt to gain entrance to the building or to disable a generator on the roof, and not as a clear effort to kill the people in the building. Besides today's use of a police bomb to kill the suspect, are there any other cases in US history where US police or FBI (not military) outside actual wartime used a bomb with the clear intent to kill a suspect, shooter, or perpetrator, not including cases where teargas cause a fire (such as Waco or the SLA shootout)? Edison (talk) 16:49, 8 July 2016 (UTC)
 * According to the Austin-American Statesman (the major newspaper from the Texas state capital), the Dallas police department used a breaching charge, which is an item that a well-equipped American police special-tactics team would have access to. It is not "standard" to use the breaching device (or the bomb-disposal robot to which it was attached) as an offensive lethal weapon.  I have read at least a few newspaper articles - including the one I just linked - in which legal experts opined that there was not any specific restriction on this use by the police.
 * In my neighborhood, our police Special Operations team has a special response vehicle - I call it a tank - and it has been used at least once to respond to an active shooter who crossed into my hometown from the nearby city of Cupertino. Against our tank, the heavily-armed criminal assailant did not last very long.
 * I toured Miniatur Wunderland last month - the largest model railroad in the world. It has exhibits for several different nations showing off the great trains of Germany, Scandinavia, Austria... and they also have a model railroad exhibit for the United States, which features a model train careening past a police shoot-out.  It's an unfortunate representation of our nation's unfortunately-earned reputation.
 * Nimur (talk) 23:16, 8 July 2016 (UTC)


 * Calling the 1985 device used by Wilson Goode a "bomb" is quite inaccurate.  It was intended and announced as an incendiary device that would drive the violent and illegal squatters from their location, but was delivered (to mine and the shock of millions of others) even after MOVE had been depicted on live TV press as having openly and publicly doused their roof with an inflammatory organic petrochemical. μηδείς (talk) 02:44, 10 July 2016 (UTC)


 * You can call it what you like, but MOVE has the use of that term well-cited, even including the government commission's official investigation of the event. DMacks (talk) 20:57, 10 July 2016 (UTC)


 * Well, thanks for your permission. Having watched the event live, I saw MOVE members cover the roof in what looked like gasoline and which was commented on by TV announcers. (MOVE were not averse to apocalyptic self immolation, see the Rizzo-era event--our article on both events is horrible, sorry)
 * Then a police helicopter-delivered concussive device ignited the roof. The device itself did not destroy any buildings with an "explosion" but it did ignite the accelerant. Flash grenades are not usually called bombs, but you have my permission not to use the term "entry device".
 * In any case, "firefighters, who had earlier deluge-hosed the MOVE members in a failed attempt to evict them from the building, stood by as the fire caused by the bomb engulfed the first house and spread to others, having been given orders to let the fire burn." μηδείς (talk) 03:17, 11 July 2016 (UTC)
 * Indeed, "bombings cause fires when exploded near flammable material" is not an unusual situation. The commission report and related investigations note that there was a gas can on the roof. The device is citedly a bomb (trying to follow WP:V here) regardless of its intended or actual effect in terms of destructive process. And again per refs, the inteneded effect was to destroy a bunker on the roof, not directly to flush out occupants of the houses. DMacks (talk) 08:16, 11 July 2016 (UTC)

Contaminating Jupiter
Let's imagine some Johnny Appleseed sabotaged the Lego figurines aboard the Juno, filling each one with hardy endospores in a mirrored thermos and a teeny burst charge set to go off when the atmospheric pressure rises to about 1 atm (which is a region with liquid water clouds in the atmosphere of Jupiter. Is it believed that Earth bacteria could colonize these clouds?  How visible would the effect on Jupiter be? Wnt (talk) 16:55, 8 July 2016 (UTC)
 * You can find a wide range of atmospheric densities, so there might be an altitude at which something deployable from a probe would float, regardless of whether the individual bacteria would float. Lego plastic is ABS which has a density of 0.9 g/cm3 - 1.53 g/cm3 : median 1.07 g/cm3. The article on Jupiter's atmosphere refers to pressure gradients rather than density, so it's not clear at what level a Lego might float suspended, or a bacterium might float, or whether it would be quickly melted or sterilized. On Earth, updrafts can keep hail suspended in clouds until it is larger than a baseball. Might similar boluses of high density material be suspended by updrafts on Jupiter? There is high radiation in space near Jupiter. Would atmospheric radiation or high temperatures or toxic gases quickly sterilize all known extremophiles from Earth? Edison (talk) 17:17, 8 July 2016 (UTC)
 * The Legos that were sent with Juno were not the standard Legos. They were specifically made of aluminum for the mission. And the OP's question isn't about the figures, it's about endospores sent with the figures. Dismas |(talk) 17:43, 8 July 2016 (UTC)
 * Thanks for the correction. The standard Lego has about the density of water, or of a drop of water or bit of water ice contaminated with bacteria. The point is that a spaceprobe has some components with low density. If contaminated, could they float at some altitude after the probe breaks up during entry? Do water drops or ice swirl about in the Jovian atmosphere?Edison (talk) 19:20, 8 July 2016 (UTC)
 * First, water clouds in the Jovian atmosphere are thought to lie in the pressure range from 3 to 7 atm, not 1 atm. Second, I doubt that any terrestrial life can survive there due to presence of toxic compounds and lack of necessary nutrients. Ruslik_ Zero 20:19, 8 July 2016 (UTC)
 * I was being approximate. And yeah, I doubt it.  But .... has someone doubted it in a higher level of resolution than this? Wnt (talk) 01:34, 9 July 2016 (UTC)
 * I love that phrasing! —Tamfang (talk) 08:51, 9 July 2016 (UTC)

UHD: How does forward compatibility work?
I read Wikipedia's article Ultra-high-definition television but I am wondering about something. If a program is broadcast in UHD, how do older TVs (1080p) display the program? A friend was telling me that the older TVs can just downgrade the signal, but I am doubtful about that. Wouldn't the broadcaster have to send out two separate signals, one with the program in HD and another in UHD? I'm not talking about Netflix or anything like that, I'm referring to free service from regular TV stations (such as the Rio Olympics on NBC, or in a couple of years presumably all primetime US network programming will be UHD). Mathew5000 (talk) 17:35, 8 July 2016 (UTC)
 * The simple answer is that they don't. While I think there's enough forward compatibility that it's nominally possible to design compression formats which are backwards compatible with older codecs and are able to output a lower resolution, these aren't generally very efficient. If you want backward compatibility with older TVs, it makes most sense to simply continue to broadcast older compatible streams alongside new incompatible streams. In the US which you seem to be referring to, the situation with broadcast terrestrial TV is particularly acute since AFAIK ATSC standards in the US is limited to MPEG-2. So HD streams are already using significantly more bandwidth than necessary and you're even more likely to lose more than you gain if you attempt to reuse the HD stream for the UHD. For cable and satellite, I believe it's more complicated but some still use MPEG-2. In any case, even for those using H.264, it's still going to be better to simply transmit a seperate HEVC (or whatever) stream than a stream which includes a backwards compatible 1080P H.264 component. It isn't just compression either, advancements in broadcasting means newer standards allow great bandwidth efficiency even without considering the codec. (Our article suggests ATSC is up to v3 now. Of course this isn't universal. While many countries use DVB-T for their HD streams, some do use DVB-T2 and I'm not sure if a T3 or whatever is likely.)  In the terrestrial space, due to limited number of radio channels and competition from mobile phone networks, simultaneous transmission may mean initially more TV channels will be back into each radio channel in both the HD/SD and UHD arenas resulting in lower quality (and probably fewer UHD). Once these are switched off, more UHD TV channels may be available and at higher quality. Note that this doesn't mean old TVs will need to be thrown away, a small STB will enable reception of UHD channels and display of them downscaled on older TVs. Really it probably won't be that different from analog switch off. Also there's no guarantee current UHD TVs will be able to receive broadcast UHD unless the standards are already set.  The situation in the satellite/cable arena is similar except that there's generally more available bandwidth so less of a crunch. And also most people already use STBs, so it's just a matter of replacing existing ones.  Nil Einne (talk) 14:24, 9 July 2016 (UTC)
 * Then repeat process with 8K. Maybe even 16K. The 2020 Olympics will be broadcast in 8K (at least in Japan) Sagittarian Milky Way (talk) 16:39, 9 July 2016 (UTC)


 * 8K is just absurd, unless the idea is to be able to zoom in on sections. Even 1080 can be a bit much, as I don't care to see the stubble on everyone's faces.  What Olympic coverage does need, however, is a faster frame rate.  Too often the athletes look so jerky it's like they are under a strobe light.  I think satellite bandwidth restrictions are responsible for this, but the higher the resolution the lower the frame rate has to be to fit in the same bandwidth.  They could also show the same event from different angles (I think DVDs and/or Blu-Ray had that capability, but it was never used much.) StuRat (talk) 05:29, 10 July 2016 (UTC)


 * Zooming in on sections is called "getting closer to the TV". And 4K is awesome. You can see blades of grass in most soccer coverage. The pixels look so tiny! They're almost not there. They show things like hummingbirds filling the screen in the store and you're like "Woah!". 1080p is like garbage when you see that. Wanting to avoid unpleasant details like male hairs is called "getting further from the TV".


 * Ultra HD actually has double the max frame rate of 1080 HD, 120 Hertz. (per Rec. 2020). Get TV that arrives in a wire. They don't have to worry about sharing bandwidth with a million uses. And some TVs interpolate frames halfway between the real ones to make 240 Hz. The standard can show more vivid colors and 30- or 36-bit color instead of 24, with 33 being necessary to not be distinguishable from life by man. Some have 22 channels of surround sound and 2 center channels of the main left and right ones mixed 2 low bandwidth "subwoofer channels". I don't need surround sound. Sagittarian Milky Way (talk) 10:26, 10 July 2016 (UTC)


 * The low frame rate problem was caused by a lack of satellite bandwidth from the Olympics themselves. Interpolation can help somewhat, but reconstructing info that just isn't there to begin with has it's limits.  I'm not sure how close we are to the physical limits of how much info can be broadcast, but you are right that eventually we will need more and thicker wires to send more info.  For fiber optics, for example, one photon to represent one bit of a pixel per frame (ignoring compression) would seem to be the lower limit (but you may need more than that). StuRat (talk) 20:52, 10 July 2016 (UTC)


 * With 8K you couldn't even see pixels. That'd be like Star Trek. Unless you were really close. This will not stop until no one can see pixels anymore. Then they'll find a way to make people need more pixels so they can keep making money. They'll make a 16 foot long 16K TV that can show more than one 480 Hz (interpolated) 240 Hz (real) sports game at once. Or they'll bring 3D back so you'll need more pixels. That's what they'll do when 8K TVs are so cheap and low profit margin that anyone could buy one (4K TVs are now $249 at Walmart!). One day they'll make a TV where you sit in the center of a sphere on a stalk and the entire sphere is a screen and speakers. Either that or virtual reality goggles that have the same effect. Sagittarian Milky Way (talk) 18:49, 10 July 2016 (UTC)


 * A 24-bit color representation allows 224 or 16,777,216 color variations. The human eye can discriminate up to ten million colors (ref). What is the claim that 33 [bits] are necessary to not be distinguishable from life by man based on? AllBestFaith (talk) 15:47, 10 July 2016 (UTC)


 * Rec. 2020 says that 11 bits per color channel are needed. 24 bit is sufficient to not be able to tell some colors apart (I've noticed this myself) but you can tell say, 00AF00 from 00B000 or anything else that doesn't use the other color channels enough. And my mistake the dot channels in surround sound are "LFE channels". I always assumed I knew what the dot channels were cause 6 speakers (5.1) seems the minimum possible to "surround" you and still have a center speaker (1 per wall plus the original 2). BS name. Sagittarian Milky Way (talk) 18:12, 10 July 2016 (UTC)


 * As I recall, our eyes are far more sensitive to subtle changes in brightness than hue. Therefore, color models which encode the brightness separately, like the HSV color space model, can allocate more bits to brightness and fewer to hue, and thus get by with fewer bits overall than the RGB model. StuRat (talk) 22:32, 10 July 2016 (UTC)

Clock accuracy on spacecraft like Juno
Apparently the Deep Space Atomic Clock, in development at NASA, will be accurate to within 1 nanosecond every ten days. How accurate are the clocks on current NASA space missions such as Juno? (I know that there is some drift due to relativistic effects, but that can be predicted and compensated for; what I'm asking about is the inherent accuracy of the clock itself.) It was reported that the orbital insertion at Jupiter hit its target "within one second", but was the timepiece accurate enough that it stayed within much less than a second, since departing Earth in 2011? Or was it kept synchronized with clocks on Earth by other means, and if so what? For example, I've heard about using eclipses of the Jovian moons to synchronize timepieces. Or the obvious, send a radio signal and have the spacecraft send a timestamped response immediately on receipt but that method must introduce other inaccuracies and also depends on knowing position. Mathew5000 (talk) 21:03, 8 July 2016 (UTC)


 * According to this thread, Juno does its time keeping primarily by radio link to Earth-based clocks. There are various uncertainties and inaccuracies at each stage in the link, and they give an Allan variance - a measure of how unstable the clock's ticking is - of between 10-16 and 10-15 per 1000 seconds for each part of the link (I think they're saying that there are four parts each contributing roughly the same amount of uncertainty. The DSAC on the other hand is expected to have an Allan variance of 3×10-15 per day, which is about 3×10-17 per thousand seconds. This makes it much more accurate, allowing better ranging measurements. I must admit, I don't fully understand our article on Allan variance (nor the details of how timekeeping over Deep Space Network works - i.e., whether they verify and adjust Juno's clock every so often), but it seems that Juno's timekeeping is accurate enough to allow measurement within 1 second after 5 years. Smurrayinchester 09:50, 10 July 2016 (UTC)

Effect of a magnetar-strength magnetic field on matter
The magnetar article claims that "The magnetic field of a magnetar would be lethal even at a distance of 1000 km due to the strong magnetic field distorting the electron clouds of the subject's constituent atoms, rendering the chemistry of life impossible.". So if the magnetic field of the Earth became that strong, what would happen to matter? Would it fall apart? Would I be able to walk through walls (since electromagnetism gives solids their solidity)? — Melab±1 &#9742; 21:56, 8 July 2016 (UTC)
 * there is indeed a school of thought that says you would be able to walk through walls. --Trovatore (talk) 00:36, 9 July 2016 (UTC)
 * In a superstrong magnetic field atoms become stretched out along the field lines, and much narrower perpendicular. Atoms can bond together in ways we do not normally see making things like a linear shaped H42+. Everything would be fibrous, and probably cannot be turned across the magnetic field lines without massive force and chemical disruption. Graeme Bartlett (talk) 04:42, 11 July 2016 (UTC)