Wikipedia:Reference desk/Archives/Science/2015 August 4

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August 4

Huge southwest French spider?

This is as vague as it gets, but as far as I can tell from Googling around, everyone in France seems to think their spiders are small and relatively harmless. I was staying in a country house in the Gers department (southwest France, north of Pyrenees) and came upon an old well that had been hidden by overgrowth of vines and trees. Looking for (cautious) adventure, I dove into the jungly leaves and found the well to be sealed up by a wooden "house" structure on top of it, which had a wooden frame door. I opened this door up slowly with the intention of looking down and clinging to the inside of that door was the largest spider I've ever seen in my life, and I live in the western US (wolf spider is otherwise the largest I've seen, about the size of the palm of my hand). This spider looked like a massive orb spider, with legs spread to the size of a tight fist, the dark bulbous thorax being nastily large as well, completely brown, very heavy looking, and it was probably wondering what just happened to its glorious, dark domain. Any ideas what spider this may be? Really scary fella, not "small" by any means. Reflectionsinglass (talk) 09:43, 4 August 2015 (UTC)

I doubt that we have enough information for a positive ID, but does Lycosa narbonensis look familiar? It's found in that area. Deor (talk) 11:54, 4 August 2015 (UTC)

Ooh, nasty! I did take a photo of the spider but it's not a good one and currently stored away on some ex. drive. I will take your suggestion and compare it when I can. I seem to recall the spider being thinner (but just as bulbous in the back), and more evil looking, like something from a children's halloween book, but this is a great starting point. Thank you! Will return with more info when I can. Reflectionsinglass (talk) 17:56, 4 August 2015 (UTC)

Another possibility is Hogna radiata, also found in the south of France. Deor (talk) 20:41, 4 August 2015 (UTC)

Keep in mind, many animals can be found far from places they "are found". It's not often you open a crate from Parts Unknown and find a rhinoceros. But small spiders are common stowaways, even giant ones (did you see a clearly evil huntsman spider?). Many are never seen at all on arrival, let alone make the news. Just crawl away. If they're unique enough and single enough, their New World experience ends when they die. But if they're pregnant or close enough to another apparently different species, it becomes a land of opportunity.

Sorry to widen things up instead of narrow them down. I know that can be frustrating. I met a decidedly alien-looking yellow centipede the other week, and have no solid clues, despite the Internet. I think it comes in peace. InedibleHulk (talk) 15:32, 9 August 2015 (UTC)

Contemporary Technologies and the Brain

Assuming I'm concentrated in some word, can contemporary technologies identify this word? What's the probability to identify it correctly? Does it limited to some small and closed vocabulary that contemporary technologies can identify, or they can identify any word? 5.29.9.245 (talk) 13:10, 4 August 2015 (UTC)

No. A thought is a very complicated... ummm... thing. See also Brain–computer_interface. 196.213.35.146 (talk) 13:26, 4 August 2015 (UTC)

You may find this interesting: http://www.dailymail.co.uk/sciencetech/article-2814896/The-mindreading-machine-listen-voices-head-let-paralysed-speak-again.html 196.213.35.146 (talk) 13:38, 4 August 2015 (UTC)

Does winter gasoline have higher specific energy?

In the US, winter gasoline and summer gasoline have different compositions [1]. Does this difference in composition lead to a non-negligible difference in specific energy? The article already means winter gas being cheaper, so if its specific energy is higher too then that would be a double whammy. My other car is a cadr (talk) 13:18, 4 August 2015 (UTC)

According to our gasoline article, "gasoline blends differ, and therefore actual energy content varies according to the season and producer by up to 4% more or less than the average, according to the US EPA." So yes, there might be a difference, but probably not enough to matter very much. Looie496 (talk) 13:35, 4 August 2015 (UTC)

I think I understand what specific energy is, but I'm not sure; hopefully the rest of my response answers your question. When living in Indiana 2010-2014, I noticed that I typically needed to fill my gas tank after about 400 miles of highway driving in the summer and after about 320 miles of highway driving in the winter, even though I was driving in the same manner on the same roads. I got the same results all over Indiana and surrounding states, and any time I've discussed this with other Americans (regardless of the state), they've observed the same thing: winter gas doesn't have as much energy as summer gas. Nyttend (talk) 15:06, 4 August 2015 (UTC)

Additional reading suggests that there is more butane in winter gasoline than summer gasoline (see [2] [3]). That said, there are other factors that might affect gas mileage maybe? (heat vs. AC, road conditions that affect average speed?) shoy (reactions) 18:35, 4 August 2015 (UTC)

The article on Gasoline talks about energy per volume and energy per mass as if they are always proportional, but they are not. Gasoline is said to have a thermal expansion coefficient such that its volume decreases .00095 for a 1 C temperature drop. So if the winter temp is 55 C lower than the summer temp, as might occur in the midwestern USA, then the volume of say 20 gallons of gas would be smaller by .00095*55 or about 5%. Butif the same number of moles and the same mass of fuel is there, It would have the same "specific energy," or energy per mass, but a greater "energy density," or energy per volume, if you had the same chemical mixture of hydrocarbons but at a lower temperature. Edison (talk) 19:37, 4 August 2015 (UTC)

I've always thought of the idea that the "specific energy" of gasoline changes a lot based on temperature (eg, the idea that you should buy gas early in the morning because it's colder, and therefore you get more for your money) as somewhat of a myth. Do substances change density based on temperature? Sure. But you're buying gasoline that's been sitting in tanks underground, where the temperature is pretty constant. Also I don't know if you got your Fs and Cs confused above, but there's definitely not a 55 C difference between summer and winter temperatures (that would be 131 F). shoy (reactions) 17:56, 5 August 2015 (UTC)

There are several reasons as to why mileage would be lower in winter than summer, here and here for example. I've noticed that some people forget how long they let the vehicle idle to warm it up in cold temperatures, in this case anything below −20 °C (−4 °F). CambridgeBayWeather, Uqaqtuq (talk), Sunasuttuq 00:40, 6 August 2015 (UTC)

Grumman LLV

The Grumman LLV gets 10 miles per gallon in normal use, and going by the standards typically applied to US road vehicles, it gets 18 miles per gallon if, for some bizarre reason, it gets driven on the highway. Why is the fuel efficiency so low? My old Chrysler Cirrus LXI got up to 30 on the highway, and my little Hyundai Accent can get up to 45 on the highway, even though the Cirrus was bigger than the LLV and the Accent's vaguely the same size. Nyttend (talk) 15:04, 4 August 2015 (UTC)

The rated EPA city mileage is actually 16 mpg; the actual in-service average of 10 mpg is the result of mail-truck driving conditions being substantially less fuel-friendly than the EPA test cycle. (Mail delivery necessitates carrying lots of cargo, with very frequent stops and starts above and beyond the usual city stop-and-go.) The three-speed automatic transmission won't help fuel economy or acceleration, either, and likely isn't geared for efficient highway cruising. And everything is built on a thirty-year-old framework optimized for lifespan rather than performance.

In contrast, the Hyundai Accent is about 600 pounds lighter (2100 lbs versus 2700 lbs for the LLV)—before you add in a quarter ton of parcels and mail sacks. It has a four-speed transmission (five if you get the manual gearbox) which probably includes at least one overdrive gear for better highway mileage. And the Accent is aerodynamically superior, what with actually having curved surfaces. The LLV is about as streamlined as a lunchbox. TenOfAllTrades(talk) 16:27, 4 August 2015 (UTC)

Stanene's room temperature super ? conductivity

I saw a recent news article [4] citing theoretical work on stanene ( [5] ) that says that the material might be "able to conduct electricity without generating any waste heat" because "electrons should be able to travel along the edges of the mesh without colliding with other electrons and atoms as they do in most materials." Specifically, "Stanene is predicted to be an example of a topological insulator, in which charge carriers (such as electrons) cannot travel through a material’s centre but can move freely along its edge, with their direction of travel dependent on whether their spin — a quantum property — points ‘up’ or ‘down’. Electric current is not dissipated because most impurities do not affect the spin and cannot slow the electrons..."

This is one of those cases where I might have a better chance with both hands and a flashlight.

• How does being a topological insulator lead to loss-free conduction?

• What is spin-orbital coupling or spin-momentum locking and why does it happen?

• Is there some relationship or analogy between the separated bands in this material and the Cooper pairs in a superconductor?

• Is this thing in any sense a superconductor, or are there things that don't have resistance that aren't superconductors?

• Why doesn't the magnetic field of the separated currents disrupt the predicted band structure? Or does it, with some kind of current limit appearing as in superconductors?

• Any other explication you can think of! Is this as cool as they say, if the predictions bear out?

Wnt (talk) 15:29, 4 August 2015 (UTC)

We do have a spin-orbit coupling article. DMacks (talk) 19:47, 4 August 2015 (UTC)

• The theoretical difference between a perfect conductor and a superconductor is that a superconductor is a separate state of matter, and is produced by quantum physical effects (electrons can be bound together into Cooper pairs through interactions with phonons). Perfect conductors and superconductors have in common the fact that if you expose them to a magnetic field, the currents this produces in the material exactly cancel out the magnetic field. However, if you expose a theoretical perfect conductor (i.e. one that obeys Maxwell's laws but doesn't have any weird quantum additions) to a magnetic field while creating it, you could "trap" the field inside it - the currents inside the material keep turning forever and sustain the field. Superconductors on the other hand under go a state transition which causes something called the "Meissner effect" – the expulsion of all fields inside the material - which can't be explained by Maxwell's equations alone. Superconductors aren't totally understood, but the model that describes them is BCS theory. I don't know whether stanene would display the Meissner effect or not, but its behavior is certainly due to quantum effects. Smurrayinchester 12:49, 5 August 2015 (UTC)

Maybe Nikola Tesla wasn't crazy after all ?

Tesla famously had the idea of broadcasting power rather than running wires. That failed to take off because so much of the energy is wasted and there's no way to (financially) charge those who receive it. There would also be a fair amount of danger from that much electricity broadcast through the air, in that anything which acts as an antenna might burst into flames.

However, did he ever consider narrow-beam transmissions of power ? Some possible applications:

1) Vacuum cleaner. The broadcast unit could be at the nearest outlet, and receiver on the vacuum cleaner. I picture parabolic antennae on both that track each other.

2) Lawn mower. The broadcast unit could be wired underground to the middle of the yard. Again, they would track each other. Advantages over gas lawn mower include being quieter and not polluting the air. Advantages over corded electric lawn mowers include no risk of cutting the cord. Advantages over battery-powered lawn mower include no batteries to recharge and replace when they won't hold a charge any more, and no time limit on each usage.

So, is this practical ? Would it be dangerous ? Has it been attempted ? Do we have an article ? StuRat (talk) 17:01, 4 August 2015 (UTC)

There are two questions that are only vaguely related. The first is whether Nikola Tesla was crazy. The second is whether his idea about wireless power was crazy. Just being crazy doesn't mean that your ideas are wrong. Just being sane doesn't mean that your ideas are right. Nikola Tesla was never diagnosed as psychotic, but it is clear that he had some sort of mental illness that some think may have been paranoid schizophrenia. John Forbes Nash was diagnosed as paranoid schizophrenic, but Nash equilibrium is accepted by the scholarly community. Thomas Edison was sane, and a shrewd businessman. However, Tesla was right about the feasibility of alternating current, and Edison was wrong about the advantages of direct current. See Current wars. Whether Tesla was right about wireless power has nothing to do with whether he was crazy. The question is which of his ideas about wireless power were sane and which were crazy. Robert McClenon (talk) 16:55, 5 August 2015 (UTC)

Wireless power gives a fair outline. Anything else you need to know after reading it?--86.144.255.14 (talk) 18:38, 4 August 2015 (UTC)

I see that Wireless_power#Far-field_or_radiative_techniques talks about point-to-point transmission, but they seem to be talking about much higher power levels and greater distances. StuRat (talk) 03:42, 5 August 2015 (UTC)

Broadcasting power requires either that you send little packets of electricity out (like sparks off a van de Graaf generator) or that you make use of a varying magnetic and electric field i.e. electromagnetic radiation. I think an issue with wireless power today is that anything powerful enough to run a lawnmower is going to be very hard to keep from interfering with your cell phone! Nonetheless, reading that article points out that you have applications like cell phone chargers. Powering something by a laser-to-solar-cell is also technically power radiation, and with ever more spy-y technology about, seems more believeable nowadays. Extremely low frequency is another option, though one that has some people very worried about potential health effects that remain controversial. And of course, you can always hold up a fluorescent bulb under a power line and see how much power radiation occurs inadvertently. But demanding the kind of power be beamed that can run a lawnmower? By definition, that has to be enough power to hurt - enough to run a blade you don't want going over your foot. However you move that energy, whether by super laser, microwave oven horn or some radio transmitter from hell, you do not want to get in the way of it as EM any more than you want to get in the way of the blade. Wnt (talk) 18:37, 4 August 2015 (UTC)

Is this a hoax, fraud or genuine revolution for hair loss treatment ?

We do not answer requests for medical or legal advice. See https://en.wikipedia.org/w/index.php?title=Wikipedia:Administrators%27_noticeboard/Incidents&diff=prev&oldid=645065201 by Doc James according to the Wikipedia:General_disclaimer and the guidelines at the top of this page. μηδείς (talk) 01:13, 5 August 2015 (UTC)

Does anyone know the use of this compass?

I found this compass in an old house and it has Chinese symbols on the compass part. I can't really find anything similar on the internet. I'm assuming this is a maritime compass but there a few odd things i can't figure out the use for. There's an opaque disk inside what looks like a telescope viewfinder on the bottom. And there is a screw on the top in the back which seems aligned with everything else, but i wonder why they would have that there unless you opened it up to let light in or something. It seems really well made and very heavy, the springs and mechanism on the base are all brass and very cool.

Pretty curious to learn more about this. If anyone has any ideas or knows where i can look for more information about ( what i assume is an old) compasses let me know.

http://imgur.com/a/W1EHl#x7gfBXJ

70.210.72.171 (talk) 17:56, 4 August 2015 (UTC)

Not much of an expert but I found this Japanese aircraft compass which is graduated in a similar way to your compass, although instead of "E" for east, yours appears to have the Japanese character for east. I also found Compass - Remote Reading, Japanese, circa 1945 which is in a similar type of binnacle to yours. I imagine it is easier to have the compass is another part of the aircraft to the cockpit so as not to have magnetic disruption from all the other instruments. Presumably there would have been some sort of optical sighting tube to allow the navigator to see it, perhaps the telescope-like attachment that you have. A lot of this is guesswork, so if anybody knows better, please feel free to correct me. Alansplodge (talk) 18:25, 4 August 2015 (UTC)

It sounds like the sighting scope is so they could identify the direction of a target.StuRat (talk) 22:48, 4 August 2015 (UTC)

wow very interesting, thanks for figuring that out, I guess I'll try searching information on Japanese world war 2 aviation compasses now. The sighting scope still seems weird to me I can't see how that would be useful since you'd have to hold it up in the air or something. 70.210.71.56 (talk) 00:39, 5 August 2015 (UTC)

If you remove the screw in the back, does that allow you to use the sighting scope by looking through that hole ? If so, there might have been another part to the scope to be attached in place of that screw. Also, is the whole upper part on a ball joint ? (It might be frozen up.) If so, it may be possible to use the sighting scope while the apparatus is bolted down. Presumably the compass does not move when the upper part, including the sighting scope, is moved. StuRat (talk) 03:57, 5 August 2015 (UTC)

The hole on the back (with a screw cap) was for filling the compass with liquid. You'd have to periodically drain/clean/refill it. 75.139.70.50 (talk) 12:52, 5 August 2015 (UTC)

Why was it filled with liquid and what liquid was it ? StuRat (talk) 15:55, 5 August 2015 (UTC)

The compass floats. It allows the compass to stay steady when mounted to an unsteady surface. I suppose it could use just about any liquid. The cheap one on my boat uses distilled water. 199.15.144.250 (talk) 19:04, 5 August 2015 (UTC)

(edit conflict) My father used to be a navigational instrument maker for both ships and aircraft, and he told me it was alcohol similar to surgical spirit. This article says purified kerosene is most common, but isopropyl alcohol is sometimes used (which seems to be the same thing as surgical spirit). The purpose is to dampen the movement of the needle; if you have a cheap compass without liquid, the needle jiggles about like a demented thing and is very difficult to read accurately. Alansplodge (talk) 19:07, 5 August 2015 (UTC)

Maybe the "sighting scope" is for attaching a small lamp and socket? is the opaque disc completely opaque?—eric 01:13, 6 August 2015 (UTC)

The sighting scope is not completely opaque, you can see if there is light behind it or not but that is about it. It seems weird that it should be filled with liquid since it works perfect without it. Should i fill it up with rubbing alcohol to preserve it? 70.210.76.110 (talk) 01:33, 6 August 2015 (UTC)

Now that's a request for advice, which according to the guidelines people on the Refdesk aren't supposed to give because we aren't experts and, so far, it sounds like nobody here has touched one of these before. Wikipedia disclaims all responsibility, so if you ruin a valuable antique based on what you read here there's no redress. Wnt (talk) 13:55, 6 August 2015 (UTC)

Pure alcohol might tend to preserve it, by killing microorganisms growing on it, but the "alcohol" commonly available to consumers is mostly water, and that would promote rusting. StuRat (talk) 14:01, 6 August 2015 (UTC)

Pure alcohol, being less hydrophilic might dissolve things that rubbing alcohol cannot - depending on what it dissolves, I don't know if that is a good or a bad thing. For example, I have no idea what kind of ink is used, what kinds of sealant was used, etc. Wnt (talk) 14:00, 8 August 2015 (UTC)

• The "sight" is indeed most likely for illumination only. Here is a Japanese version with the same configuration and here the almost exact same compass (Japanese again). That might help to narrow your search.--TMCk (talk) 14:54, 8 August 2015 (UTC)

Do we gain/lose self-awareness as we grow older?

I was walking past a high school this morning and suddenly I was reliving being back in high school. I was wearing a flannel shirt tied around my waist by chance (why, no idea, it's boiling outside) and I used to wear flannels like this all the time back in the 90s, so everything sort of clicked and I recalled myself walking about high school being completely "aware" of myself, a bit self-conscious, shy, and all that good stuff. I felt almost exactly the same, and a strange thought occurred to me: I seem to be as self-aware as I was 20 years ago. So I guess that's a good thing.

I ask because sometimes, being an adult now, I notice myself reacting less to certain things. I don't laugh as hard or as silly as I would as a teenager. I'll nod and concede that I'm amused, for example. Or I'll do things with less flair and conscientiousness for others, sort of like a robot would; from checking into a hotel and just talking automatically rather than being actually engaging. I've noticed these little things recently and wondered to myself, am I losing my "self" to something? Not sure how else to ask this question. Thought I would pose it here in science rather than a more philosophical board; hope that's alright. Reflectionsinglass (talk) 18:02, 4 August 2015 (UTC)

Wikipedia has an article on the Aging brain which may lead you interesting places in your research to answer your question. --Jayron32 18:42, 4 August 2015 (UTC)

If your attitudes and awareness didn't change as you aged then presumably you would be an eternal teenager, which despite the opinions of teenagers, is not a great thing.Greglocock (talk) 23:49, 4 August 2015 (UTC)

NASA VTOL aircraft testing at Moffett Field in the 1950's

In the 1950's I had a chance to see a duel counter rotating prop driven fixed wing aircraft being tested at Moffett Field Ca. I would like to find out what model it was and some history on it. I think it was made by Bell, but I am not sure. My memory shows it tethered to a semi flatbed trailer in the vertical position. If anyone knows anything about an aircraft of this type I would appreciate any information you could give me.

THANKS

Richard — Preceding unsigned comment added by 184.12.238.208 (talk) 19:41, 4 August 2015 (UTC)

In the 1950s, the Convair XFY-1 Pogo and the Lockheed XFV-1 were the two U.S. experimental tail-sitters with counter-rotating props. If you look at the pictures in the two articles, you can presumably identify the one you saw. Deor (talk) 20:23, 4 August 2015 (UTC)

There was also the Hiller Helicopter Demonstration facility, located on the site of what is now Facebook headquarters building on Willow Road - which was, at the time, part of the city of Palo Alto. (Reference: Over Time: Palo Alto, 1947-1980 (General History: California), by Ben Hatfield and Barry Anderson). This facility was, as you know, not actually building helicopters or VTOL aircraft; it was in fact recently declassified, as scheduled; it was as published in Year 2006 part of the National Reconnaissance Office's Project CORONA. A variety of "unique" helicopters were demonstrated at Palo Alto and at Moffett Field (presumably these were to distract attention from the true nature of the NRO program). Among the interesting VTOL aircraft was the Hiller X-18 with counter-rotating propellers (which is sometimes considered a grandfather of the V-22 Osprey). Nimur (talk) 22:03, 4 August 2015 (UTC)

Some more great resources:

• Ames Rotorcraft webpage, including free books!
  • Autogyros, Helicopters And Other V/STOL Aircraft, Volume I and Volume II (free books!)
• The Hiller Museum, which is located a few minutes north (by aircraft) at San Carlos Airport
• SP-3300: Flight Research at Ames, 1940-1997, a full and very thorough book that covers almost every weird Government Airplane (or similar) that flew out of Moffett for the greater part of the 20th century. They have some nice photos of gyrocopters, tilt-rotors, "vertiplanes," and all sorts of other weird contraptions.

Nimur (talk) 00:17, 5 August 2015 (UTC)

THANKS!! I had seen the Convair XFY POGO also, but it was the X-13 Vertijet that I was trying to remember. I had the two confused.