Wikipedia:Reference desk/Archives/Science/2014 January 3

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January 3

How much did the metre become shorter over time?

When I learned about the metre when I was small, I've always seen it as about 3.33 or 3.34 ft and I've held that belief for my entire life, nowadays it seems to be shortened to 3.281 ft., which now makes my metric-to-imperial estimate that I've always used an overestimate (30 m equals about 100 ft). Has it always been getting shorter over time, as the distance light travels over a specific time becomes more exact? If so, how much over the years? The measurement data provided in the metre page was a bit too complicated for me to understand. If possible, I would like a simple list, showing in metre-to-any other unit of measure, how it changed from it's conception up to the present time. — Preceding unsigned comment added by 72.235.228.21 (talk) 01:46, 3 January 2014 (UTC)

The definition of the meter has changed over time, but unless you are very old indeed, certainly not that much in your lifetime. Scanning the metre article, it looks like the first reasonably precise definition differed from the current one by about 1 part in 5000. --Trovatore (talk) 02:01, 3 January 2014 (UTC)

Given that you should stick with one unit type when doing measurements to avoid error, the rough equivalents seem not to have changed a whole lot. You examples give 1.5 cm of change, or about an inch. This isn't very meaningful on large scales, and again, if you need precision you probably shouldn't use conversions at all and stick with one measurement system. Mingmingla (talk) 02:08, 3 January 2014 (UTC)

An inch is defined as 2.54cm. 1.5cm is 0.6 inch, or about 19/32". CS Miller (talk) 12:01, 3 January 2014 (UTC)

I don't know how I screwed that one up... I guess I was think km to miles. (1.6) I'll stick with my metric system. Mingmingla (talk) 15:36, 3 January 2014 (UTC)

The problem isn't so much the precision of meter as of feet and other units. Foot (unit)#Historical units called the foot in different countries shows some of the old mess. You didn't say when or where you were small but based on your IP address I guess it was in USA. United States customary units#Units of length says: "The system for measuring length in the United States customary system is based on the inch, foot, yard, and mile, which are the only four customary length measurements in everyday use. Since July 1, 1959, these have been defined on the basis of 1 yard = 0.9144 meters except for some applications in surveying." A yard is by definition 3 feet so that makes 1 foot = 0.3048 m by definition. The meter to foot ratio becomes 3.280839895... which does indeed round to 3.281. PrimeHunter (talk) 02:17, 3 January 2014 (UTC)

Well, the foot hasn't changed much either, in the lifetime of almost anyone still alive. The article says that the 1959 redefinition changed the length of the US foot by 2 parts per million from what it had been since the Mendenhall Order of 1893. That's certainly less than the change from the meter being defined as 1/10,000,000 of the distance from the North Pole to the Equator (though that definition was longer ago). --Trovatore (talk) 02:36, 3 January 2014 (UTC)

A meter is between 3'3.3" and 3'3.4". Maybe you remembered the digits right but misremembered the units, turning those into 3.33' and 3.34'? Red Act (talk) 04:46, 3 January 2014 (UTC)

This is exactly why you should not have foot and inches because people confuse 3 foot 3.4 inches with 3.34 feet!!! As a counter example, try and confuse 3 metres 34 cm with 3.34 metres. 220.239.51.150 (talk) 06:46, 3 January 2014 (UTC)

I learnt that the metre was 3 foot 3 and three-eighths inches, but that was in the days when feet, inches and eighths were commonly understood. Dbfirs 08:57, 3 January 2014 (UTC)

We were taught that a meter is 39.37 inches, which is pretty close to the actual conversion. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:17, 3 January 2014 (UTC)

Tangential debate
The following discussion has been closed. Please do not modify it.
The core problem with the metric system is its supposed strength - namely, powers of 10. Basically, the meter is too long, and the centimeter is too short. Inches, feet and yards are more "human" measurements. The metric system is fine for scientists but an annoyance for the average citizen. ←Baseball Bugs What's up, Doc? carrots→ 13:17, 3 January 2014 (UTC) That's a very common comment about the metric system - but why anyone would say such a bizarre thing escapes me. I grew up with both metric and imperial systems and I don't find metric units any more or less "human". The meter is only "too long" if you're used to thinking in yards. The centimeter is only too short because you're thinking in inches (and probably, half-inches). What things are there that can't conveniently be measured in metric? I could argue for units where the average height of a human was the longer measure - would that be yet more "human" than imperial units? I guarantee that picking a range of things that people commonly measure, there are just as many that are close to a meter (or close to a centimeter) as there are close to a yard or an inch. The only problematic issue is that the metric intermediate measure between a meter and a centimeter. However, in countries where the metric system is the norm, people could use the decimeter as that measure - but they don't, because it's not necessary. I'd like to see a source for your beliefs. I call bullshit. It's just another pathetic excuse for people who have not been immersed in the metric system not to switch. SteveBaker (talk) 14:22, 3 January 2014 (UTC) I agree, ...but you'll never convince me that F isn't handier than C for casual discussion of the weather. APL (talk) 17:11, 3 January 2014 (UTC)

There haven't been any significant changes in the length of the meter (that you would notice outside a measurement laboratory, or in some of the situations described at State Plane Coordinate System in the US) nor in the conversion between US customary lengths and meters, since the US legalized the metric system in 1860. Jc3s5h (talk) 14:42, 3 January 2014 (UTC)

Winding thread evenly onto a spool

When winding thread from a spool onto a bobbin using a sewing machine, the thread goes up and down, filling the bobbin evenly. How does this happen? I'd like to transfer thread from a large cone onto a smaller spool, preferably without having to constantly guide the thread up and down as it is wound and would therefore like to mimic whatever conditions allow the thread to wind evenly onto a bobbin. --78.148.110.243 (talk) 10:34, 3 January 2014 (UTC)

As long as the thread is smooth and even, and the spool and bobbin are in good condition and correctly aligned (with a reasonable distance between the spool and the bobbin to reduce any side forces) it should naturally fill up evenly (as long as it starts at one edge). Because the thread will follow the path of least resistance, the winding should only change direction when forced to do so by the inside edge of the bobbin.--Shantavira|^{feed me} 16:03, 3 January 2014 (UTC)

Hmm ... It "should" work like that, but there are lots of caveats above so it is difficult to guarantee an even wind in practice. An alternative to the up and down thread guide would be to tilt the bobbin from side to side. If you are able to monitor the winding, then manual adjustments are easy to make, but a fully automatic smooth wind needs some careful planning. Just try it and see how smooth the wind turns out. Dbfirs 16:45, 3 January 2014 (UTC)

This is a problem closely related to that faced by production electric and electronic engineers regarding winding wire onto coil and transformer bobbins, and getting it right means more profit, so we are very interested. Getting a smooth wind is not easy with normal enamelled wire but is easy with "litz" wire which is far more flexible. The right tension (not too much and not too little) helps. A wire or cotton diameter very small compared to bobin diameter promotes smooth winding, as does a very low bobbin width to wire or cotton "fly" ratio, and a low bobbin width to diameter ratio. By "fly" I mean the length of wire cotton that is "flying" free in air between the last position controlled feed point (eg pully or supply spool) and the take up bobbin.

As Shantavira has siad, the wire/cotton tries to take up a path of least resitance. This means it seeks the lowest wire/cotton tension. If the lowest tension comes from neatly going alongside the previous turn, it will go neatly. If the lowest tension comes from jumping over a previous turn, which will be the case if the fly angle deviates too far from 90 degrees wrt bobbin axis, or the wire/cotton diameter is too large, it will rise up over the previous turn and a non-neat wind will result.

Conclusion: Choose (a) A spool that is not too long compared to its diameter; (b) make the fly distance long, perhaps 100X the bobbin width. Increasing the fly distance allows an increased spool width. Your winding system should have an adjustable brake that sets the cotton tension sensibly independent of winding speed. The other factors I mentioned need not be considered in winding cotton. Profesional wire winders usually have the wire passing over a pulley, and a mechanism of gears or cams moves the pully side to side so as to keep the fly at just under 90 degrees wrt the bobbin axis. A fly angle of exactly 90 degrees promotes turns not hard up against each other, leading to turns in the next later dropping through, leading to a non-neat winding in subsequent layers.

121.221.87.183 (talk) 23:42, 3 January 2014 (UTC)

Food temperature

asked and answered
The following discussion has been closed. Please do not modify it.
Generally, all cultures prefer to eat foods that are served hot or chilled. I have the impression that it should be more natural, beneficial and tastier to eat food at room temperature. Our body mechanism also would work optimally, I presume at either room or body temperatures. What is your comment? — Preceding unsigned comment added by 161.139.102.6 (talk) 14:02, 3 January 2014 (UTC) 1) ) Didn't you just ask this ? 2) I think the answer given was that heating food kills germs and cooling it prevents them from growing, so food served hot or cold is less likely to cause food poisoning than food left out long enough to become room temperature. Thus, people who preferred hot or cold foods were more likely to survive and pass on those genes. StuRat (talk) 14:11, 3 January 2014 (UTC) The OP asked pretty much the same question on the 25th.[1] ←Baseball Bugs What's up, Doc? carrots→ 14:50, 3 January 2014 (UTC) Chilled food for the sake of chilled food is a very new invention. Only in the past three hundred years or so have people even had ice in their homes. Before that, the only chilled food you'd be likely to see would be with simple evaporative cooling mechanisms. (See Pot-in-pot refrigerator) Those only work well in hot dry climates, but you can see the value of keeping, say, a jug of milk cool in the desert. APL (talk) 17:05, 3 January 2014 (UTC) I can think of other mechanisms for cooling. There's the root cellar, which is particularly effective during summer in a place with permafrost. Also, if you have a nice cool stream, say glacial meltwater, you can use that to cool things down, even in summer. Additionally, there's was a time when huge quantities of ice were stored in insulated warehouses, right through summer. However, if you have the misfortune to find yourself living in a hot desert without electricity, then your options are rather limited to evaporative coolers (unless you also lack water). StuRat (talk) 15:22, 4 January 2014 (UTC) Ice harvesting I sort of mentioned. It's what I meant by the "three hundred years or so" comment. It goes back further in a few very limited areas of the world, but only for the wealthy. You're right that I'd forgotten about Root Cellars, though. APL (talk) 18:34, 4 January 2014 (UTC)

changes in biochemical parameters in urine in case of neurogenic and hypovolemic shock

WHAT WILL BE THE EFFECT ON URINARY URIC ACID,KETONE BODIES AND VMA LEVELS IN CHILDREN OF HYPOVOLEMIC AND NEUROGENIC SHOCK DUE TO TRAUMA ALTHOUGH URIC ACID LEVELS AND KETONE BODIES LEVELS INCREASE IN ANY CASE OF TRAUMA OR STRESS,BUT TO WHAT TO EXTENT DO THEY INCREASE IN ABOVE MENTIONED SHOCKS --122.163.230.26 (talk) 15:38, 3 January 2014 (UTC)ISHAAN VOHRA --122.163.230.26 (talk) 15:38, 3 January 2014 (UTC) 3/01/2014

I DON'T KNOW BUT TYPING LIKE THIS IS CONSIDERED RUDE BECAUSE IT FEELS LIKE YOU ARE SHOUTING AT US. Please avoid that in the future :) SemanticMantis (talk) 16:06, 3 January 2014 (UTC)

i am sorry if it sounded rude though it was unintended :),but still if you can help me out with this,it will be generous of you. --122.163.253.126 (talk) 12:46, 4 January 2014 (UTC)ishaan vohra --122.163.253.126 (talk) 12:46, 4 January 2014 (UTC)4/01/2014

It seems hard to locate such information, wouldn't it depend mainly on the severity, the degree of hypoperfusion? Urine output (volume) is monitored in such cases, but when trauma is the primary cause urinalysis may not be needed for diagnosis and treatment, except to check for signs of genitourinary trauma, and perhaps later to assess kidney damage. In any case, with less perfusion the kidney function will be impaired, urine volume will drop, concentration of uric acid, sodium and others will rise but the total amount excreted will be less (after all, in severe cases there's no urine production at all).

I'm not a medic, so you may prefer to wait for someone whose answer is based on more than just google.... Ssscienccce (talk) 22:33, 4 January 2014 (UTC)

Autocatalytic set -- Formal definition

Autocatalytic set#Formal definition states:

Formally, cl(S) denotes the smallest subset Y of M that contains S such that for each reaction (A, B)

 A ⊆ S ∪ Y ⇒ B ⊆ Y

I read "... subset Y of M that contains S" to mean that S ⊆ Y ⊆ M, but in that case writing "S ∪ Y" in "A ⊆ S ∪ Y" is silly since S ∪ Y = Y. What am I reading wrong here?

Am I misreading "that" in the quoted text? Does "... subset Y of M that contains S" mean Y ⊆ M where S ⊆ M, that is, "... subset Y of M where M contains S"? -- ToE 16:23, 3 January 2014 (UTC)

My quick reading is that your interpretation is correct, and that the notation used in our article is a bit redundant/misleading. Perhaps the contributor that typed it out thought the redundancy would aid in understanding, but in that case maybe they should have written "A ⊆ S ⊆ Y", though that would probably require extra parentheses. Anyway, have a look at Box 1 here: [2], which gives a clearer notation and a more meaningful explanation of the terms. If anyone is feeling WP:BOLD they could easily paraphrase that box 1 into our article, and cite it as a reference (or Hordijk et al. (2012), (from which that box 1 derives), but the earlier article may not be as freely available. Make sense? SemanticMantis (talk) 17:28, 3 January 2014 (UTC)

Thanks for the reference SemanticMantis! If I grok it, I will try to improve the wording in our article. -- ToE 21:15, 3 January 2014 (UTC)

Spidersplosion

what is this all about? Is this some kind of spider orgy? — Preceding unsigned comment added by 92.14.16.139 (talk) 17:14, 3 January 2014 (UTC)

First, they are not spiders, they are Opiliones, a.k.a. "Harvestmen". (Some people call them "daddy long legs", but that common name can also be used to refer to a true spider (and even a crane fly!), so we shouldn't use that name ;) They huddle together as a defensive measure, and to retain warmth (they will die in the presence of a hard freeze). In addition to our articles above, here's a nice little write up about them, that also mentions the defensive huddle [3]. SemanticMantis (talk) 17:33, 3 January 2014 (UTC)

And just to back up my assertion, this (recent, peer-reviewed) paper agrees that "... gregarious behaviour in G. longipes [a cave Harvestman species] may be related with the choice of more suitable microconditions in the cave habitat and/or with group chemical defence." [4] -- so, the huddle helps them stay warm, the pulsating mob may deter some predators, and their chemical defenses are also much more effective when released by a large group. SemanticMantis (talk) 17:51, 3 January 2014 (UTC)

Is there a better link than the one provided? I gave up after 5 minutes. Also, given the sp. name longipes, why would one not call them Daddy longlegs? μηδείς (talk) 20:22, 3 January 2014 (UTC)

It's fine to call then "Daddy Longlegs" if that is the usual local name, but don't expect to be understood world-wide, as SM explained, because various long-legged insects get called that name, regardless of their Latin name. As far as I know, the term is used only for the crane fly in the UK. I haven't found a better link for your Harvestman. Dbfirs 21:14, 3 January 2014 (UTC)

Yes, just look at the coccinellidae page to see the battles that go on about whether they should be called ladybirds of ladybugs! Richerman (talk) 22:24, 3 January 2014 (UTC)

Harvestmen? Interesting, in dutch they're called haywagons (hooiwagens)... Ssscienccce (talk) 23:09, 4 January 2014 (UTC)

Thank you! — Preceding unsigned comment added by 92.14.16.139 (talk) 21:39, 3 January 2014 (UTC)

Some thoughts:

1) If they are trying to keep warm, you'd think they would have moved to the sunlit patch.

2) They sure don't act like they're cold. They move like they are nice and warm. So, however they manage it, they are keeping warm somehow. StuRat (talk) 15:13, 4 January 2014 (UTC)

I recall reading that clumping in this way is more about conserving moisture than heat. I'm having difficulty finding a ref for that, though (and our article on hibernation doesn't seem to cover insects), so take of it as you will. Searching for spider hibernation on Google doesn't yield much either. Time to do some science! Matt Deres (talk) 14:15, 5 January 2014 (UTC)

How Can They Save the Birds?

My parents live in the US NE and are suffering a cold snap with lows at or below zero Fahrenheit. My father noticed five birds (Juncos and Chickadees) huddled in a bush outside his window where one would normally ever see at most one bird. Is there anything he can do to assist the birds through this unusual cold snap, especially over night? (There is a bird feeder just put out, which the birds are using.) μηδείς (talk) 19:54, 3 January 2014 (UTC)

See http://www.birds.cornell.edu/Page.aspx?pid=1098.

—Wavelength (talk) 20:25, 3 January 2014 (UTC)

A dozen birds in one birdhouse? Now I will be tempted to go peek in with a flashlight this weekend! μηδείς (talk) 20:35, 3 January 2014 (UTC)

High energy food and a regular supply of fresh water are probably the most practical thing you can do at short notice. You can put a metal container of water on bricks with a candle in a can underneath to stop it from freezing as long as it's not too windy. The slightly more hi-tech way would be to use an electric heater of the type used to keep a fish pond from freezing over completely. Funny thing is we're having unusually severe storms and flooding in the UK at the moment and, according to the weatherman today, it's because the large mass of cold air over the US is changing the path of the jet stream. So, if I could persuade you to put lots of candles out...... Richerman (talk) 22:03, 3 January 2014 (UTC)

Unfortunately the winds will be 25mph with 35 mph gusts. And there's snow on the ground, so the birds will really only be lacking for heat. I thought of having peanut butter put out, but at the high today of 20F it will be rock hard. I'll have to assume the birds are aware of the birdhouses my mom has out, and the feeder she got for Christmas has already attracted the Juncos and Chickadees, as well as Cardinals and Nuthatches. μηδείς (talk) 22:18, 3 January 2014 (UTC)

Are you assuming the birds can eat snow for water? If the snow isn't melting into pools they can drink, I doubt they are getting fresh water. When we had deep snow for days, a couple of winters ago, we put out a tray of water refreshed a couple of times a day, on the advice of the RSPB who said it was more important than putting out food. The birds certainly appreciated it, and seemed to come from all over to drink from it when it wasn't frozen. Once the snow started to melt into pools they could drink, the number of birds we got dropped. 86.139.158.44 (talk) 09:00, 5 January 2014 (UTC)

Maybe you can try sunflower seeds instead of peanut butter? They are also a high-energy food that many birds like, and they shouldn't be frozen solid at this temperature. 2601:9:3200:467:FC6F:C03E:D43E:753 (talk) 00:36, 4 January 2014 (UTC)

They've got a pound of hemp seeds hanging in the feeder. I had sillily thought peanut butter mixed with seeds would be even better, but they won't be feeding on that at night, and I think they get plenty during the day. I was wondering if leaving the lights on would help, but they've nowhere to perch near enough for heat. I thought of a cardboard box for shelter, but there are a few bird houses still out, so I am going to assume they will find shelter there. I advised my mother to light the three-wicked candle in the bathroom and leave the windows open and the shower running. She figured out pretty quickly that was a joke on my part. The link Wavelength gave is pretty comforting. μηδείς (talk) 00:44, 4 January 2014 (UTC)

When my mother was a girl they used to heat bricks in the oven, wrap them in newspaper and put them at the bottom of the bed. Maybe some hot bricks under the bush - or perhaps they could run to a patio heater? The hemp seeds should give them a warm rosy glow anyway. Richerman (talk) 01:17, 4 January 2014 (UTC)

To address that as if it were entirely serious, I think the problem is that any last minute accommodations are probably going to go unnoticed by the birds. There's also no way my parents are going to put up with an open flame or running electricity. Tomorrow I may cut down a branch from a densely foliated evergreen on the north side of the house and wedge it in the bush they were hovering in on the south side. This should provide extra warm cover during the day, and at night if they haven't been using the bird houses. μηδείς (talk) 01:40, 4 January 2014 (UTC)

If you're concerned about keeping water and/or food warm without flames or electricity, then maybe you could use a flameless ration heater or tommy cooker for this purpose? (CAUTION: If using one, make sure it doesn't get TOO hot.) FWiW 2601:9:3200:467:6109:95AD:B0F7:600D (talk) 23:08, 4 January 2014 (UTC)

What is that grub like thing that burrows out of a chipmunk when it dies?

What is that grub like thing that burrows out of a chipmunk when it dies? When I lived in the Coast Range Mountains in Western Oregon, USA, my cat would kill chipmunks and present them to me. One grub like animal would burrow out of the dead chipmunks, usually out of their stomach, sometime out of the thigh area. Since it burrowed out of all chipmunks my cat brought me, I assume all chipmunks had one inside of them, maybe to help it digest whatever it ate??? What was it, what was its purpose, and why did it burrow out of the chipmunk immediately after it died?Willow cougar (talk) 23:20, 3 January 2014 (UTC)

I've seen a great many dead chipmunks in the US and never once saw a grub burrow out of one immediately after it died. In warm weather, blowflies lay eggs on the dead chipmunks, and maggots are seen after sufficient time. Mammals do not have grubs in them to help them digest their food, and our article Chipmunk refers to no grub, although they eat worms and insects. Animals sometimes have parasites in their digestive system or in their flesh. Edison (talk) 23:37, 3 January 2014 (UTC)

I'm not too up on the habit of cats in regard to how long after a kill dead prey can be to be presented as a gift to an owner, but the grubs have to be the maggots of either carrion flies or flesh flies or some similar fly that lays its eggs on dead animals. They hatch rather quickly after laying. The chances someone's cat is going to bring home chipmunks that actually were infected with some sort of grubs before they were killed is somewhere between zero and nil. μηδείς (talk) 01:50, 4 January 2014 (UTC)

I was once told that Liver flukes sometimes chew their way out of their host's corpse. I have no idea if that's actually true - I literally just remembered about it. --Kurt Shaped Box (talk) 02:05, 4 January 2014 (UTC)

Flukes don't have jaws, and their life cycle is dependent on either passing eggs or being consumed by a secondary host, depending on which stage they are in, so it would never benefit them to crawl out of a corpse, they wouldn't be able to reproduce or infect another host that way. They might conceivably be seen as the host decays, perhaps being mistaken for chewing their way out. μηδείς (talk) 02:28, 4 January 2014 (UTC)

A Goa'uld symbiote ? :-) StuRat (talk) 15:01, 4 January 2014 (UTC)

Could it be a botfly larva? This article shows some images that you could compare with what you've seen: tree squirrel botfly. You can find a lot more on Google image search if you have the desire (and stomach). You are well outside the range given for C. emasculator in this article (eastern US and Canada), but there are other Cuterebra species found throughout North America including Oregon: The Oestrid Flies. They infest various rodents including chipmunks. The larvae are also known as warbles, or wolves. --Amble (talk) 15:37, 4 January 2014 (UTC)

Yes, it could be a botfly, but they mostly affect much larger animals that can't avoid contact with the fly, and the chance of the OP's cat regularly bringing home chipmunks with recent botfly infections is quite low. The Goa'uld hypothesis is about as likely. μηδείς (talk) 18:39, 4 January 2014 (UTC)

Most of the time that a cat brings home a chipmunk as tribute, it probably doesn't have any botfly larvae. Occasionally, they do. But nobody comes to the reference desk to ask why their cat brought home a kill and nothing crawled out of it (see self-selection bias). From what I've read, botfly infestations of chipmunks are not uncommon and match the OP's description better than anything else that's been suggested. --Amble (talk) 19:22, 4 January 2014 (UTC)

Maybe the cat is doing the selection. When it bites into a chipmunk and finds a nasty worm, it gives it to you as a present, and keeps the good ones for itself. :) Wnt (talk) 18:55, 5 January 2014 (UTC)

A botfly that infects rodents would not infect large animals and vice versa, those are different species of botflies.

This study found a 51% infection rate in chipmunks shot between august 7 and october 12, in the years 1966 to 1969 (in Wayne county, NE Pennsylvania). They also noted that relatively few had signs of previous or recent infection, suggesting selective loss of infected animals from the population. Being easy prey for predators (like cats) could explain that... Ssscienccce (talk) 00:20, 5 January 2014 (UTC)

Wow, that's terrifying to learn. μηδείς (talk) 17:13, 5 January 2014 (UTC)