Wikipedia:Reference desk/Archives/Science/2014 December 8

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December 8

Virus contagiousness

Why is it that myocarditis caused by viruses is not contagious? Surely the virus that caused it is contagious but I read in an article that once it causes myocarditis it's no longer contagious. — Preceding unsigned comment added by 194.66.246.104 (talk) 00:26, 8 December 2014 (UTC)

Myocarditis is a late stage of viral infection. By this time the virus can disappear from mucosal sites, from where it can spread. Ruslik_Zero 02:27, 8 December 2014 (UTC)

Convenience link: Myocarditis. --220 of ^Borg 05:53, 8 December 2014 (UTC)

Baldness in males

Is there an age by which a male can stop worrying that he may go bald? In other words, can the blank be filled in, for the following sentence? "If you are not bald by the age of _______, then you have a pretty good chance that you will never go bald and you can stop worrying about it" I assume it is rare that a guy makes it to, say, age 71 with a full head of hair and then, all of the sudden at age 72, he goes bald. Thanks. Joseph A. Spadaro (talk) 01:19, 8 December 2014 (UTC)

No, I think there's just a lot of variation in extent, onset and speed of baldness, and a wide variety of causes. I suppose one could make a claim that if you are not thinning on top or receding at the front by the age of 40, then you have a better than even chance of retaining hair into your seventies. Our article on hair loss doesn't give any such prediction, and I don't know whether anyone has published any statistics to support my suggested claim. Dbfirs 09:13, 8 December 2014 (UTC)

You stop worrying about it starting when it starts. Greglocock (talk)

For what it's worth, I lost all of my hair through Alopecia totalis over a period of about six months when I was aged 53. Before that I had not shown any signs of male pattern baldness. AndrewWTaylor (talk) 12:37, 8 December 2014 (UTC)

• This source notes that 25% of males have some noticeable hair loss by age 21, 2/3rds by age 35, and 85% by age 50. So, a rough estimate shows that 14 years produced an increase of 42 percentage points, while another 15 years produced another increase of only about 17%. So, the older you get and still have your hair, the greater chance you have of keeping it another year, but human population being both as large and as variable as it is, there is no way to say with perfect certainty that there is some age at which you cannot ever expect to lose your hair. Certainly, there's been at least one person, of the billions who have ever lived, which meet the exact specifications you have (full head of hair at 71, cue-ball bald at 72), but there would not be a LOT of people in that situation. --Jayron32 12:56, 8 December 2014 (UTC)

• Luxon, K., Fletcher, R., & Leeson, H. (2009). [Predictors of Future Anxiety About Male Pattern Baldness in New Zealand Males. New Zealand Journal Of Psychology, 38(3), 35-41, in its introduction, states that male pattern baldness (MPB) can occur any time after puberty and affects two thirds of all men by the age of 60. Citing Hamilton, J. B. (1942). Male hormone stimulation is prerequisite and an incitant in common baldness. American Journal of Anatomy, 71 , 451-480, it states that "Three determining components of the time of onset, rate of loss, and extent of MPB, are age, genetics, and androgens. MPB is therefore unpredictable..." This suggests to me that no, there is no "safe" age one reaches where if hair loss hasn't started yet, it never will. I think Jayron32's response above makes sense. It seems to me a hypothetical man's determining factors for MPB are not likely to change dramatically at any point in time, so if he still has most of his hair at age 40, 50, or whenever, his rate of hair loss probably won't suddenly increase on his 60th birthday. But it could. A genetic predisposition for late onset plus a sudden change in androgens, say. --some jerk on the Internet (talk) 14:42, 8 December 2014 (UTC)

The OP's question is about worrying about going bald. Worrying is not a productive activity, so one should never worry about it. HiLo48 (talk) 17:12, 8 December 2014 (UTC)

Indeed: At the first press conference for Star Trek: The Next Generation, someone asked Gene Roddenberry “Surely by the 24th century they would have found a cure for male pattern baldness?" Roddenberry replied, “No, by the 24th century no one will care.” I think that actually happened at the dawn of the 21st century. I've been (mostly) bald since my early 20's and I definitely vote "Don't worry". Having poorer eyesight and less acute hearing bother me much more than lack of hair. SteveBaker (talk) 21:37, 8 December 2014 (UTC)

Popular wisdom is: "if it's greying, it's staying". --catslash (talk) 00:13, 11 December 2014 (UTC)

Thanks. I had never heard that saying. That's interesting. Joseph A. Spadaro (talk) 15:20, 11 December 2014 (UTC)

Hm, my dad has noticeably less hair now than ~34 years ago when I first noticed some grey. —Tamfang (talk) 09:30, 11 December 2014 (UTC)

Yeah - but what's left is presumably all grey - hence the argument (which I'm somewhat doubting) that the dark hair fell out, leaving only grey hair remaining. SteveBaker (talk) 17:30, 11 December 2014 (UTC)

Thanks, all. Joseph A. Spadaro (talk) 15:16, 12 December 2014 (UTC)

Very begulling

• Excuse the pun. I went to the riverfront today in Windsor, Ontario, and took a couple pictures of a gull (full body; portrait). I was wondering if anyone could help identify the species, or at least the genus. — Crisco 1492 (talk) 04:20, 8 December 2014 (UTC)

begulling, beguiling. Watch out someone doesn't 'correct' your 'speeling'! 220 of ^Borg 05:58, 8 December 2014 (UTC)

• At least I don't have to deal with autocorrect! — Crisco 1492 (talk) 20:14, 8 December 2014 (UTC)

portrait

I guess this is the image that you meant to show. I am far from an expert but until the Kurt Shaped Box comes along I'll suggest it is an American herring gull, (Larus smithsonianus), On second thoughts I think it is a Greater black-backed gull, probably an immature bird from the colouration of the head. Richard Avery (talk) 07:53, 8 December 2014 (UTC)

• Didn't mean to "show" them, since I didn't want to overwhelm the other questions. I don't know, Windsor and the St. Lawrence River are a fair bit away from their range (indicated in the article at least). — Crisco 1492 (talk) 14:01, 8 December 2014 (UTC)

A photo of a juvenile in our American herring gull article (that Richard linked above) bears a striking resemblance, including similar, but lighter, beak markings. Alansplodge (talk) 14:34, 8 December 2014 (UTC)

Hi guys. I'm pretty sure that this is an adult ring-billed gull in its winter plumage. The amount of grey on their heads varies from individual to individual. This is the gull that people in North America will typically see loitering in parking lots. Seriously. That has for some reason become their thing - hundreds of them at once. Just hanging out. --Kurt Shaped Box (talk) 16:02, 8 December 2014 (UTC)

Good call. Shows what some local knowledge can do instead of trying to guess from the other side of the Atlantic (note to self). Alansplodge (talk) 19:20, 8 December 2014 (UTC)

There I told you he'd know. Wonder why it is called that? ;-) Richard Avery (talk) 19:38, 8 December 2014 (UTC)

• That looks about right, yeah. Thanks! (Maybe there is a male version of an Iron Maiden, and his name was Kurt?) — Crisco 1492 (talk) 20:14, 8 December 2014 (UTC)

FWIW, I'm on the other side of the pond too. I just read lots of stuff about gulls and watch gull videos. This one, for example, where we can see numerous examples of the ring-billed gull in its natural habitat (the parking lot). The ones with the pinkish beaks are the youngsters. --Kurt Shaped Box (talk) 21:56, 8 December 2014 (UTC)

Largest venomous/poisonous organisms

I've read before people claiming that the Komodo Dragon is the largest venomous animal in the world, but that doesn't seem to be true to me.
Maybe it's the most poisonous land animal (by weight and length/area/volume?), but the Lion's Mane Jellyfish is definitely larger in length/area/volume. But is it heavier or lighter than the Komodo?
And what is the largest venomous stingray? It should be longer and larger by area/volume than the Komodo, but I don't it they would be as heavy.

So, what are the largest venomous animals by different categories? The different categories could be:
- land, aquatic, amphibious, flying, etc
- largest by length, body area/volume, weight/mass, etc
Also, what is the largest venomous plant?

Note that I'm not interested in the strength/toxicity of the venoms of the different animals here ("how poisonous they are"). That is, as long as they produce venom, they're considered venomous, and I'm interested in only their body measurements (size, weight, etc).

Thanks. 175.156.91.156 (talk) 08:58, 8 December 2014 (UTC)

The supposed venomousness of the Komodo dragon seems to be disputed. And as you suggest, it kind of depends on how you define "largest". ←Baseball Bugs ^{What's up, Doc?} carrots→ 09:02, 8 December 2014 (UTC)

Some documentaries say the Komodo is poisonous, although they do also mention its a combination of venom and germs in their mouths/saliva that kills animals.

https://www.youtube.com/watch?v=EHB_CM86rgk

http://www.discovery.com/tv-shows/life/videos/komodo-dragons-hunt-buffalo/ or https://www.youtube.com/watch?v=A-NxMONuJQA

https://www.youtube.com/watch?v=q7CQInAXoqY — Preceding unsigned comment added by 175.156.91.156 (talk) 11:50, 8 December 2014 (UTC)

I suspect this was just a word-substitution error on your part, since you used venom, poison, and toxin completely accurately in all other instances, but it's worth noting just for the sake of certainty that there is no such thing as a venomous plant; venoms are toxins which are injected as part of a defense mechanism by creatures with specialized organs adapted specifically for this task; poisons are toxins which were ingested or otherwise absorbed into the body which may either have evolved specifically to harm other creatures which predate on the organic source of those poisons or which merely do so incidentally. In this regard, the largest plant that qualifies as poisonous depends upon both the species ingesting/coming into contact with the plant and whether or not you mean to include only plants which evolved toxins as a specific chemical deterrent to predation. After-all, the vast majority of plants are harmful for a human to ingest signifcant quantities of, but we don't normally consider a sequoia poisonous, per-say. There is Sarracenia flava, a carnivorous plant which supplements its traps with coniine, but even then the prey still has to ingest it. Snow talk 10:08, 8 December 2014 (UTC)

Aren't plants such as nettles, giant hogweed, and poison ivy venomous, rather than contact-poison? CS Miller (talk) 10:53, 8 December 2014 (UTC)

Nettles (or rather, thistle) actually had occurred to me as well, though I neglected to mention them. The best term in that case is probably simply toxin, in that you are right that they may not qualify for poison as the toxin is not absorbed entirely passively while neither do they qualify as venom, which is typically reserved for those species of animalia that actively inject the toxin; if one had to choose between the two in the case if nettles, poison would definitely be the choice I would favour. As for Hogweed and poison ivy, they are absorbed in a more conventional manner consistent with the term poison. Snow talk 14:21, 8 December 2014 (UTC)

Or rather nettles - thistles are just damned prickly - Nemo me impune lacessit. Alansplodge (talk) 14:37, 8 December 2014 (UTC)

You know, I'm not sure if you were just seizing the opportunity for a little tongue-in-cheek comment or if you were honestly noting that thistle needles are not poisonous -- but if the latter, it looks like you were right. I remember being told once that certain species of starthistle had minorly-irritating toxins in their needles, but I can find no evidence of this in any reliable source now. It would seem maybe they are just jabby. The confusion would seem to arise from the fact that many species are poisonous from consumption and have been known to kill domestic species, horses in particular, in this fashion. Well, you unlearn something new every day. ;) Snow talk 06:44, 9 December 2014 (UTC)

Are any of the gigantic deep-sea squid venomous/poisonous? I know that some squid are. --Kurt Shaped Box (talk) 16:05, 8 December 2014 (UTC)

Komodo dragons were described as venomous early on. Then it was discovered that toxic shock from their oral flora was a likely killing factor. But it has been found that venoms of various strengths are common to many squamates. Nature: "Here we report the presence of venom toxins in two additional lizard lineages (Monitor Lizards and Iguania) and show that all lineages possessing toxin-secreting oral glands form a clade, demonstrating a single early origin of the venom system in lizards and snakes." μηδείς (talk) 01:39, 9 December 2014 (UTC)

Actually, that whole theory that Komodo dragon bites "poison" more via bacterial pathogenesis than venom has recently been reversed -- the more contemporary research has suggested the tissue damage is in fact more a result of their venom, which is substantially virulent in its own right, with the bacteria playing a secondary role. It's a very recent turn in the study of the creatures; I'll try to find the source again. Snow talk 02:05, 9 December 2014 (UTC)

Actually, the source I just gave mentions the blood pressure-lowering and anti-coagulant properties of monitor lizard venom. The Komodo is a monitor lizard. μηδείς (talk) 03:08, 9 December 2014 (UTC)

Ah, ok, yes -- very good. I must admit to having not read through the title of the link in detail. Thanks for saving me the effort of finding the secondary source, which probably was covering that exact research. Snow talk 06:36, 9 December 2014 (UTC)

So, does anyone have the answers to these initial questions?:
What are the largest venomous and/or poisonous animals by different categories? The different categories could be:
- land, aquatic, amphibious, flying, etc
- largest by length, body area/volume, weight/mass, etc
175.156.52.140 (talk) 15:19, 12 December 2014 (UTC)

Wooden chopping board on induction cooktop

Just to prove a point to someone, what would be the consequences of leaving a wooden chopping/cutting board (or anything wooden really) on an induction cooktop? Anything? 124.148.124.247 (talk) 09:58, 8 December 2014 (UTC)

If you want to prove a point to someone, do it yourself. Nothing proves the point like proving the point. Wikipedia does have an article titled Induction cooking which no one is stopping you (or them) from reading. --Jayron32 12:24, 8 December 2014 (UTC)

Only ferrous metals heat up via induction cooking - so absolutely nothing at all would happen to the wooden board. Justin15w (talk) 16:00, 8 December 2014 (UTC)

True, assuming that a ferrous pot isn't placed on top of the board, and that the cook-top itself isn't already hot. I've seen some seriously irresponsible ads for induction cook-tops where they put a piece of paper between the pot and cook-top, to show that it doesn't burn. Well, it doesn't burn immediately, but it will eventually burn, as heat from the pot will spread to the paper. So, people trying to repeat that experiment at home may very well start a fire.

Also, it's possible that what appears to be a solid wooden cutting board might have a ferrous metal frame inside. StuRat (talk) 16:21, 8 December 2014 (UTC)

Most pots contain boiling (sometimes flavoured) water. The pot will be the same temperature. That isn't a high enough temperature to set fire to paper. HiLo48 (talk) 17:06, 8 December 2014 (UTC)

Frying is lots hotter than that, no? Trivial to be cooking at 200°C or beyond. Assuming the questioner is talking about leaving it in place while cooking on top of it (per StuRat, i.e., not "just" the wood), you need to address the maximum expected temperature, not the most common or average ("all it takes is once to burn your house down"). But also, the energy transfer by electromagnetic induction from the rangetop to the pot decreases with distance, so the pot on top of the wood would not heat as well as if it were closer to the surface. DMacks (talk) 18:44, 8 December 2014 (UTC)

From my experience with induction cooktops, I don't think it's particularly likely they will heat up for very long if at at all if there's a solid woodchopping board on top. Even if the induction reaches the pot, the safety mechanism on the cooktop will shut it down.

I tried just now and was able to get the pot to work once through a very thing plastic chopping board (about 0.5cm) but couldn't get it to work again, not that I tried that hard. But I don't think many wooden chopping boards are that thin. On a 1 cm plastic chopping board, I couldn't get it to work. The only wodden chopping board I have is about 3 cm thick so I didn't bother to try it. Even lifting the pot about 1.5 cm off the element is enough to get it to shut down. Now while the precise cut off will vary from cooktop to cooktop (but I don't think mine is particularly fancy), I think it's going to be fairly unlikely you'll get one which will work through a solid wood chopping board.

In terms of putting it on after cooking, the glass may still be hot after use, but even if you've been deep frying with an high smoke point oil just below smoke point, I don't think it's particularly likely the glass will remain hot enough to even singe the wooden chopping board. May be if you put the hot pot on top of it, but I'm not sure even then.

If the wooden chopping board has a sheet of metal thorough it, it may be possible it will be heated up. If it's just a metal frame on the outside, I don't think it's that likely. I suspect again, the safety will shut down the element even with one like this [1].

I'm not saying you can never cause visible edit: or worse damage to a wooden chopping board via an induction cooktop, I'm sure you can come up with some way, just that it's not particularly likely.

Nil Einne (talk) 12:18, 9 December 2014 (UTC)

Universe's radius and the Big Bang's start point

Two questions have just flashed recently:

1 is it possible to roughly estimate the Universe's radius by collating the Universe's expansion speed backwards based on its age? The metric expansion of space says the speed hasn't been always constant, but if it's not possible to factor in those changes (don't know whether it's possible or not), let's assume the speed of light for the sake of a very rough calculation (i.e., light speed multiplied by the age of the universe in seconds).

2 is it possible to roughy pinpoint somehow the direction in which the Bag Bang started, that is its initial place (the constellation, for instance, or even more precisely)? Brandmeister^talk 10:10, 8 December 2014 (UTC)

I think that question was raised recently (possibly by me), and it's not so simple. For one thing, the premise assumes that space is infinite in the Euclidean sense and that the Big Bang occurred at the (0,0,0) point, continually expanding outward. But it's not at all certain that space has the properties found in the axioms of geometry. ←Baseball Bugs ^{What's up, Doc?} carrots→ 10:49, 8 December 2014 (UTC)

It does, but just not in the three-dimensional Euclidean space you are used to. See Minkowski space, which is a geometry under which the theories of relativity accurately model reality. There's also string theory, which uses other geometries, some with dozens of dimensions instead of the 3 in Euclidean (or 4 in Minkowski) that we're used to. As far as the "initial place" the Big Bang started, the answer is "you're in it". We are all in the initial place of the big bang. The classic "euclidean" heuristic used to explain the big bang is to imagine a balloon with a bunch of dots on it. If you blow up the balloon, every dot on the surface sees every other dot moving away from it; and yet NONE of the dots is, itself, the center of expansion. If you had a infinitesimally thin skin on the balloon, and could suck ALL of the air out of the balloon so it collapsed to a single point, EVERY dot would be located at the same place. Now, run the simulation forward again. Every dot on the balloon is moving away from every other dot, but NONE of the dots is currently at the center of expansion, but they all WERE the center of expansion when it started. The universe is sort of a 4-D version of this 2-D simulation. --Jayron32 15:20, 8 December 2014 (UTC)

Yes, we can calculate / measure the expansion rate backward through time. That's exactly the process used to estimate that the radius of observable universe is 46.6 billion light years. The same set of calculations (and other supporting evidence) tells us the universe is 13.8 billion years old. The fact that the outer edge of the universe is farther in light years than the universe is old is a consequence of those regions having been closer to us at the time they emitted the last light that we can see today, i.e. a consequence of expansion during the intervening time since the earliest light was produced.

Your second question relies on a faulty assumption. The Big Bang did not start anywhere within the universe. Rather, from our point of view, it started everywhere. The cosmic microwave background may be understood as a remnant of the fires of the Big Bang. Look far enough in any direction, and you will see that fire burning everywhere. All the space we can see participated in the Big Bang, so it is reasonable to say that the Big Bang was everywhere. Another important point to realize is that the expansion that has occurred since the Big Bang also looks essentially the same everywhere. Consider the following illustration:

A--B--C--D--E--F--G

A----B----C----D----E----F----G

If you are at point D, you would say that the distance to point C doubled between row one and row two (2 dashes become 4 dashes). Similarly the distance to point B from D also doubled (4 dashes become 8 dashes). But what happens if you are at C or B or F, etc? If you start at any of these, it also appears that all of the distances double between row one and two. Space is expanding everywhere, but everyone sees it grow at the same rate and hence there is no particular location within the universe that looks like the origin.

People sometimes describe the Big Bang as inflating space like a balloon. That's a fairly apt metaphor. The rubber of the balloon stretches and all points on its surface get farther away from all other points. There is a center of the balloon, but it is a spot in the center of its volume. It is not a spot that the people living on the surface the balloon could ever visit or experience. Dragons flight (talk) 18:52, 8 December 2014 (UTC)

The problem I see with the balloon analogy is that it implies there's an "edge" to the universe, i.e. that if you magically transport yourself to anywhere you want to, you would eventually end up "outside" the universe (i.e. outside the collection of massive objects within it). But that's not what the current thinking is, is it? Isn't it theorized that "anywhere you go" in the universe you are surrounded by galaxies? Which suggests perhaps the universe kind of wraps around on itself, like a Klein bottle. The expression I've heard is "finite but unbounded". There's also in inference that if you were to head off in what you think is a straight line, you could eventually end up at the same place you started? ←Baseball Bugs ^{What's up, Doc?} carrots→ 10:49, 9 December 2014 (UTC)

No, it still works if you consider the skin of the balloon the entire universe. Just like you cannot write a dot just anywhere (it has to exist on the skin of the balloon; off the skin there's nothing to write on), the universe has nothing outside of itself to exist on. Also, there are several models of the universe that do exactly that, predict that traveling in one direction will lead you back to where you started (and also, FWIW, at the same time you left). The article Shape of the universe discusses the various possibilities and their implications. --Jayron32 13:32, 9 December 2014 (UTC)

The balloon analogy is a good one, but so is a flat sheet of expanding rubber (if you believe the universe to be approximately flat). One essential correction to both models is that galaxies are more like rigid blobs somehow anchored to the rubber sheet at their centre of mass, but free to rotate and expand or contract independently. They (and other gravitationlly bound structures) do not expand with the underlying metric expansion of space. Dbfirs 20:35, 9 December 2014 (UTC)

Antikythera mechanism questions

Two to consider:

1. I'm happy to assume that our article on this fascinating relic is correct and the device's tooling was sufficiently imprecise that errors would have swiftly accumulated. If the device and its gears had been made larger, assuming the same technical proficiency, would this have made the errors worse, better or roughly the same?
2. What useful information would the mechanism's creator have had access to, other than the dates of games in foreign countries, that he couldn't have gleaned from looking at the sky on a clear night? Was the real value in being able to predict what the heavens would show on future/past dates?

Thanks in advance for your erudition. --Dweller (talk) 10:36, 8 December 2014 (UTC)

There are at least two sources of error, one would be due to the wrong "model" being run by the machine (i.e. the implicit set of equations for predicting future events) and the other would be imprecision in the mechanism. The former would not change with a bigger system, but, if we assume that the tolerances of manufacture stay the same when the size of the gears increases, then a larger mechanism would have less error due to e.g. backlash_(engineering) and other problems that come about when gears don't fit exactly - basically a 1mm gap in a 1 cm gear toothing would be large in terms of e.g. percent rotation, but the same 1mm would cause a smaller error in a 1m gear. SemanticMantis (talk) 15:32, 8 December 2014 (UTC)

However, note that other sources of error will get worse with larger mechanisms, such as warping of the gears, perhaps due to deformation under their own weight. So, you end up with a certain ideal size where error will be minimized. StuRat (talk) 16:27, 8 December 2014 (UTC)

2) Note the convenience of not needing an astronomer to give you the info you want. Imagine if you had to go decipher the stars to figure out when Easter is this year, instead of just looking at a calendar. StuRat (talk) 16:31, 8 December 2014 (UTC)

I agree with StuRat here - but would also note that it's far from clear whether the Antikythera mechanism was ever intended to be used 'for real'. One common belief is that this was a custom-make piece built for the pleasure of some king or other - and maybe it only had to work sufficiently well to sit on a shelf someplace and look cool. As the plaything of a rich man, they may simply have piled on the cool functionality in the same way that stupidly useless features like the phase of the moon were put on pocket watches. That theory is somewhat backed up by the fact that we've never found another one like it - and it wasn't written about anyplace. That implies a couple of things - one being that it didn't have to work really well - and another that it may have been made with extraordinary care, so that the engineering tolerances were far better than would be expected of other devices of the period.

That suggests that the cost & difficulty of scaling it up might have been rather extreme.

SteveBaker (talk) 19:54, 8 December 2014 (UTC)

I don't quite get the argument that not being mass produced means it wasn't functional. There are many custom-built one-off items which are functional and similarly many mass produced items which are merely decorative. The close tolerances, on the other hand, would suggest it was made to be functional, as a toy doesn't really have to be accurate. StuRat (talk) 00:19, 11 December 2014 (UTC)

I wasn't trying to say that it wasn't functional - but it may not have to have been super-reliable, they may not have been concerned about wear on the gears or having the thing jam up if handled roughly. There's a lot of difference between making an item that can be reproduced in large numbers (with presumed reduction in manufacturing quality) than a one-off craftsman's piece. There is also lot of difference between something that could have been used to impress a king sufficiently to have him sponsor you - versus (say) making one for a ship's captain to use day in and day out in rough conditions that could be expected to remain working for decades with sufficient reliability that people could risk their lives by using it to aid navigation or something. I suspect it's the latter - in which case they may have had to push the envelope on fabrication care & precision, just to wind up with a piece that, despite all that effort, might be a fragile, temperamental and inaccurate instrument, destined to collect dust on a shelf someplace. The fact that we've never found another like it suggests the latter. The fact that nobody wrote about this remarkable instrument suggests that the ship that was carrying it sank before the object ever reached the hands of the person it was designed to impress. But we really can't know for sure. SteveBaker (talk) 17:28, 11 December 2014 (UTC)

Thanks, guys. --Dweller (talk) 20:02, 8 December 2014 (UTC)

Minimum air speed for traversing time zones faster than sun

A documentary about Tu-144 I watched implied that only supersonic aircraft is capable to "outfly" the sun and, departing from, say, Moscow, land in New York or Montreal earlier that day. What's the minimum speed value to achieve that? Although I never heard of any subsonic speed that allows that, I'm not sure whether 2 Mach is mandatory. I'm not good at such math. Brandmeister^talk 19:32, 8 December 2014 (UTC)

If you stand 100 feet from the North or South pole, you can easily walk faster than the sun. So the answer is dependent on your latitude. The highest minimum speed would be near the equator...with some hand-waving about axial tilt and the seasons. SteveBaker (talk) 19:36, 8 December 2014 (UTC)

At the equator, the circumference of the Earth is 40075.017 km, and you'd have to cover that distance in 24 hours. That's 1,670 kph, which is 1037.69mph. The "mach" number depends on altitude - at sea level, in 'normal' conditions, the speed of sound is 761.2 mph - so mach 1.36 would be sufficient. There are lots of aircraft that can fly that fast - but no so many that can sustain that speed over transatlantic distances without running out of fuel...I thought Concorde could do it...it could reach Mach 2....maybe it didn't have the range to get from Moscow to NewYork or something? SteveBaker (talk) 19:45, 8 December 2014 (UTC)

Steve is of course right about the poles, but that doesn't really have much to do with the spirit of the question. Longitude tells us that a degree of longitude is ~110 km at the equator. Let's call that an even 100km for simplicity. Time zone tells us that a time zone is usually about 15 degrees wide (with lots of exceptions for governmental convenience. Now, let's assume that the it takes the sun one hour to cross a time zone (not literally true, but pretty close). Then, to travel faster than solar time, a plane would have to fly faster than 15 degrees/hour, which, at the equator, is about 1500 km/hr. If you want to calculate the speed for a given latitude, you can use the formula with \phi=lat in the Longitude article. The ~1500 km/hr is just a rough estimate that is likely a little too slow. That is indeed faster than the speed of sound in dry air, but well shy of mach 2. In case anyone is interested, this rocket car is claimed to travel 1500 km/hr [2]. SemanticMantis (talk) 19:46, 8 December 2014 (UTC)

Thanks. Is Mach 1.36 sufficient for equator only or for both hemispheres as well? How much time ahead such subsonic speeds roughly give? Brandmeister^talk 20:20, 8 December 2014 (UTC)

Mach 1.36 is sufficient EVERYWHERE. There must be a latitude beyond which subsonic flight would be fast enough...my gut feel is that it would be up within the arctic/antarctic circles...but I haven't calculated it out. As for how far ahead...at Mach 1.36 at the equator, you're *just* keeping up with the sun...as if time had stood still. If you went (say) 10% faster, then instead of taking 24 hours to fly around the earth, you'd only need 21.6 hours - so if you chased the sun at that speed for 21.6 hours, and did a complete circumnaviagtion of the globe, you'd be 2.4 hours ahead of the sun. But if you only flew halfway around the world, in 10.8 hours, you'd only be 1.2 hour ahead, and if you flew just a quarter of the way around, you'd be 0.54 hours ahead. The answer is complicated because it depends on how far you go, how far from the equator you are, what the definition of "Mach x.x" is at the altitude you're flying, what the time zones are of the countries you start and end at, whether you cross the international date line or not...and probably other stuff I haven't though of. SteveBaker (talk) 21:46, 8 December 2014 (UTC)

Assuming Mach 1.36 at the equator, it's an easy calculation to determine the latitude above which a sun pacing flight is subsonic. The distance between two given lines of longitude varies with the cosine of the latitude, so the Mach 1 latitude is acos(1/1.36) = 42.7°. That's about Boston in the north. -- ToE 02:41, 9 December 2014 (UTC) Should use speed of sound at cruise altitude. See below. -- ToE 18:28, 9 December 2014 (UTC)

[ec] If it's sufficient at the equator, it's sufficient everywhere. Latitude is only relevant because the closer you get to the poles, the shorter is the distance around the world. The shorter the distance around the world, the slower the sun appears to move, and the slower the sun appears to move, the slower your minimum speed to keep up with it. That's why someone at the South Pole can easily do it, because walking "around the world" there, walking from 180°W/E to 0°W/E and back, can take just a few seconds on foot, while going from 180°W/E to 0°W/E and back at the equator would take several years at ordinary walking speed, even if you could walk over the ocean and through the various types of terrain on land. Nyttend (talk) 21:52, 8 December 2014 (UTC)

• The girth of the earth in miles at the equator is 24,901.55 miles, which is about 25 miles more than it would be were it a sphere. If we assume 25,000 miles in 24 hours we get 1,0416.6667mph. μηδείς (talk) 22:36, 8 December 2014 (UTC)

  Did I miss a zero? That would suggest that you need mach 13 to do this...I don't think the Tu-144 goes that fast...checking my numbers. SteveBaker (talk) 00:32, 9 December 2014 (UTC)

  Oh..no, you added a zero! 25,000/24 hours is 1041.6667...my numbers are OK (*phew*!) SteveBaker (talk) 00:35, 9 December 2014 (UTC)

I didn't notice that until you pointed it out, Steve, but it's a typo, not a miscalculation. I remembered it's about 1,000mph from elementary school. μηδείς (talk) 01:31, 9 December 2014 (UTC)

Remember also that you are trying to beat groundspeed while the speed of sound is relative to airspeed. Subsoniv aircraft can have groundspeeds that "exceed the speed of sound" if they have sufficient tail wind. --DHeyward (talk) 04:33, 9 December 2014 (UTC)

Yes, a westbound sun pacing flight could take advantage of any east winds, but the strong troposphere jetstreams flow from west to east. -- ToE 09:53, 9 December 2014 (UTC)

The speed of sound varies with temperature (pressure and density effects cancel each other out) and the 761.2 mph given by Steve above is for 15 °C. According to Speed of sound#Tables, at −57 °C (−70 °F), typical for commercial jet cruise altitudes, the speed of sound is only 660 mph (or 573 kts), meaning that Steve's Mach number was about 15% low. (The same airspeed at a colder temperature yields a higher Mach number.)

Steve managed to use both metric and imperial units in his calculation, so I will exercise my prerogative as a navigator to recompute it all in knots. One nautical mile is exactly 1,852 meters, the closest whole-meter value for the length of 1/60 of a degree of arc along a meridian, and it is thus within a fraction of a percent of the length of 1/60 of a degree (one minute) of longitude at the equator. (It is easily remembered that one minute of longitude is cos(latitude) nautical miles.) With 15° per timezone (360°/24), the sun pacing speed along the equator is 900 kts or about Mach 1.57 at cruise altitude. The latitude above which subsonic sun pacing speeds are possible is acos(1/1.57) = 50.5°, up around Regina, Kiev, or Plymouth.

The typical cruise speed of a Boeing 777 is Mach 0.84, so its sun pacing latitude would be acos(0.84/1.57) = 57.7°, near Göteborg in the north.

Moscow is at 55.75°N and New York is at 40.7°N, and the cruise altitude sun pacing speeds for those latitudes are cos(55.75°)⋅1.57 = Mach 0.88 and cos(40.7°)⋅1.57 = Mach 1.19 respectively.

But the shortest distance between Moscow and New York is a great circle of 4067 nmi, requiring a speed of 547 kts or Mach 0.95 at cruise altitude to cover it in the same 7.44 hours the sun takes to traverse the 111.6° of longitude. This is for the same apparent solar time of arrival and departure, and it considers only cruise speed, without time for takeoff and landing. It also does not take timezones into account. New York is UTC-0500 in the winter and UCT-0400 in the summer. Moscow time is always UTC+0300, meaning clocks differ by 8 hours in the winter, requiring a speed of only 508 kt or Mach 0.89 at cruise altitude, but by 7 hours in the summer, requiring 581 kts or Mach 1.01 at cruise altitude.

This reminds me of last flight of the SR-71 back in 1990 when it flew from LA to DC in 64 minutes 20 seconds. I know that the overall flight time, including take off and landing, was much longer, but I can't seem to find the numbers. -- ToE

And if your heart is not set on the Big Apple, how about Moscow to Anchorage, great circle distance only 3788 nmi, but twelve hours apart during the winter, allowing a speed of 316 kts or Mach 0.55. A 777 at Mach 0.84 could do that in under 8 hours, leaving plenty of time for takeoff and landing. (But this is approaching Steve's original point about out racing the sun during a lazy stroll 100 ft from a pole.) -- ToE 19:04, 9 December 2014 (UTC)

Edit: All calculations done assuming sill air. As suggested above by DHeyward, a tailwind will allow lower airspeed and Mach numbers. A headwind will require higher airspeed and Mach numbers. -- ToE 11:21, 10 December 2014 (UTC)

Note, of course, that, assuming that the Earth is spherical, a great circle does not give you constant velocity relative to the position of the sun unless it happens to coincide with the equator. For any non-equatorial route, flying at a speed that will keep you paced with the sun on average will in fact cause you to either fall behind the sun initially and then catch it up later or vice versa, depending on the difference in latitude. GoldenRing (talk) 01:40, 10 December 2014 (UTC)

I think a lot of above responses are very thorough; but many have confused air speed with ground speed. When you are calculating distance traveled over the ground per unit of time, that is ground speed and it can be very different from speed through the air, which is air speed. For very fast, very high-altitude, very high performance aircraft, these numbers can be very divergent. Mach numbers are not used to describe ground speed. Nimur (talk) 02:31, 10 December 2014 (UTC)

Thank you. I was remiss not to mention that my calculations assumed still air. (Now added). By the very nature of the question, any answer will have to take both ground speed and airspeed into account. -- ToE 11:21, 10 December 2014 (UTC)

Medicinal Mushrooms Article Disappeared

It has been a few months since I searched for "Medicinal Mushrooms", and when I did, yesterday, the article appears to have been removed.

I remember that the previous "Medicinal Mushrooms" article that I was expecting to view was a diverse compilation of medicinal mushrooms which included a bounty of information and a long list of some of the worlds TOP medicinal mushrooms and their health benefits, links, AND photos.

Now, it appears to redirect to Medicinal Fungi?! Where is the long list of beneficial mushrooms, health benefits, and their photos?

Reishi Chaga Turkey Tail Shiitake and, so on...

WHAT HAPPENED?!

Did someone delete this page?

Please, bring it back!

If anything, I would expect more added to the Medicinal Mushroom page that I remember. Not the complete absence of such information.

Thank you for your time and attention.

EARTHLiNGS are ALiENS (talk) 20:28, 8 December 2014 (UTC)

See Medicinal fungi#Edible species with medically significant metabolites. I can find no evidence that we've ever had another article, though it may have been renamed and/or edited. AndyTheGrump (talk) 20:32, 8 December 2014 (UTC)

Looking into this further, a great deal of unreferenced and poorly referenced material has been removed in compliance with Wikipedia policy. AndyTheGrump (talk) 20:45, 8 December 2014 (UTC)

The article you wanted was formerly entitled Medicinal mushroom (note the singular), but its page history shows that a long discussion concluded with it being redirected to the medicinal fungi article a couple of months ago. Nyttend (talk) 21:43, 8 December 2014 (UTC)

Clicking here will show you the last existing version of that article. μηδείς (talk) 22:30, 8 December 2014 (UTC)

But I'll add the caveat for the OP that if the content was removed for being unverifiable it is wise to take the information you find within with a grain of salt, and it would probably behoove you to explore the objections that were raised to said claims On the articles talk page, which is still up. Snow talk 02:12, 9 December 2014 (UTC)