Wikipedia:Reference desk/Archives/Science/2012 October 4

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October 4

Solar Panel Kits

I'm looking at different solar panels and I'm really confused. How much power would a 20 watt panel product? Is it enough to run lets say a fan? or a laptop or light bulb?

If I were to hook it up to a used car battery to store the electricity produced, what equipment would I need to lets say charge my phone with the car battery without damaging the phone [by giving it too much electricity, or for to long (overcharging)].

Any help and/or links would be greatly appreciated :-) — Preceding unsigned comment added by 76.87.48.246 (talk) 04:44, 4 October 2012 (UTC)

20 watts is very little. It could power a CFL bulb equivalent to a 75 watt incandescent light. It probably wouldn't be worth trying to store that little energy. And note that you will get less than 20 watts if it's at an angle to the sunlight, it's overcast, the panel is dusty, or it's old. StuRat (talk) 05:06, 4 October 2012 (UTC)

Do please confirm that 20 Watts is a rate and not an amount of energy. μηδείς (talk) 05:16, 4 October 2012 (UTC)

For the purposes of this discussion, the distinction is unimportant (it only becomes important when talking about storing the electricity generated by the panel, and that isn't practical with such a small panel). StuRat (talk) 05:20, 4 October 2012 (UTC)

The site says:

LiteFuzeLiteFuze 20W Mono-crystalline Solar Panel 20 Watt - High-Efficiency Maximum Series Fuse 2AbrCells 36 units 125x125 monocrystalline siliconbrNOCT 48 /-2 CbrOperating Temperature -40 C to 85 CbrMax. System Operating Voltage 1000V DCbrCE, CSA, DVE, IEC Certified So in other words, these portable and small panels are kind of useless except to maybe charge a cell phone?

— Preceding unsigned comment added by 76.87.48.246 (talk) 05:22, 4 October 2012 (UTC) 

That sounds like it's 20 watts per cell. 20 watts times 36 units is 720 watts, which is a more useful amount. Can you provide a link to the site, so I can confirm this ? StuRat (talk) 05:26, 4 October 2012 (UTC)

http://www.sears.com/shc/s/p_10153_12605_SPM7433169811P?sid=IDx20110310x00001i&srccode=cii_184425893&cpncode=30-74342331-2

http://www.amazon.com/LiteFuze%C2%AE-Mono-crystalline-Solar-Panel-Watt/dp/B0079OA7SK/ref=sr_1_1?ie=UTF8&qid=1349328481&sr=8-1&keywords=litefuze+20w — Preceding unsigned comment added by 76.87.48.246 (talk) 05:28, 4 October 2012 (UTC)

Unfortunately, that looks like it really is just one 20 watt panel. StuRat (talk) 05:34, 4 October 2012 (UTC)

Thanks for helping me out :-) — Preceding unsigned comment added by 76.87.48.246 (talk) 05:37, 4 October 2012 (UTC)

I know my biggest TV (42" plasma) can use 1Kw, my oven uses 2Kw, I've a 20 or so inch lcd monitor that uses up to 54 watts. It can be hard to figure out the wattage of an appliance because it is often written on the retail packaging, but not on the product itself. Maybe like 400 watt rated panels in top sunlight to run a laptop without batteres? Maybe 500, and even more if it is an extreme gaming rig. I am guaging that by what a desktop computer might use, 300 watts or more PSU, 50 watts or more monitor, speakers, router. It wouldn't use 400 watts all the time, but if it wants to run the dvd and hard drive at the same time for a second, it will need the full power available or it will fizzle out or at least not work. My kettle says underneath that it uses between 2520 and 3000 watts which makes it the most power hungry device here. ~ R.T.G 10:56, 4 October 2012 (UTC)

Laptops are easy to judge - just see what the power supply is rated for. Mine is 90W. I doubt there is anything outside of netbooks that can run off of a 20W panel. One of the Amazon reviews is from somebody using it to run a few small PC fans for greenhouse exhaust. I think that is probably the sort of application this is designed for - running a small load somewhere without easy power access. The greenhouse is perfect because the fans don't need to run as strong or at all when the greenhouse and panel aren't in full sun. 209.131.76.183 (talk) 13:25, 4 October 2012 (UTC)

Laptop power supply are meant to charge the battery at a reasonable rate (as fast as possible without causing to much heating of the battery. Looking at a random laptop (HP ProBook), it has a 55Wh battery for a maximum battery life of 8.5 hours. Taking a more realistic value of 5.5 hours, it would consume 10W average.

The only problem is whether the battery charging circuity will accept a lower supply current than the 65W adapter it comes with. But when using an old car battery as storage, that doesn't matter, these can supply kilowatts and accept any charge rate. Problem with car batteries is that they aren't meant for deep discharging, they are designed specifically for high peak currents (driving the starter motor). That means they're made with many thin lead plates, and totally discharging them will damage those, resulting in high losses (self-discharge rate). When I left my lights on and didn't use the car for several days, I had to buy a new one, even fully charged it wouldn't start after one day.

The other problem using a car battery: say you have one of 240Ah; that's 120Ah*14V= 3.36kWh; discharge rates for them are 1% to 25% per month according to one website, take 20% as a guess for an old one, that's a loss of 0.74% per day (assuming constant discharge rate), or 25Wh per day, so you'll need more than an hour of maximum power your solar cells can provide just to keep the charge level. That's why a car battery would be too large for a 20W cell.

Also, it would take 168 hours (exactly a week) to fully charge it, or 3.5 days if you limit discharge to 50%. that's theoretical days of 24/24 maximum sunshine, not sure what a solar cell actually delivers per day, Photovoltaic system seems to suggest 5 hours of rated wattage (750W per day for 150W panel), meaning you have only 100Wh per day and the 3.5 days mentioned earlier would in fact be 3.5*24/5=16.8, say 17 days. All this assuming 100% efficiency of charging, real value would be less than 80% imo.

In any case, you'd be better of with lower capacity low loss rechargeable batteries. Low-self-discharge NiMH seems a good option, not the regular NiMH because these have a very high discharge rate (5%-20% first day, 0.5-4% /day after that). Ssscienccce (talk) 16:07, 5 October 2012 (UTC)

I'm disappointed by StuRat's dismissal of a 20W panel as not providing sufficient power to store; it's all about the applications. Sure, 20 watts isn't enough to drive major appliances, but it's a useful trickle if you're off the grid. Consider devices like this one: a portable 2.5 watt panel that can charge a couple of AA batteries – or a connected USB device – in a few hours of sun. It won't run a refrigerator, but it will give you a reading light, a charged ebook reader, a few minutes of cell-phone usage, a weather report on the radio, or a day of GPS reception when you're out in the wilderness. The usage pattern also matters; bigger batteries and smaller panels can be a reasonable combination if they're used at (for example) a remote cabin that is only used on the weekend: seven days of charging, and only two days of usage.

That said, what you can't do is directly hook a solar panel to a battery and expect good results. You'll need to build or (more likely) buy a charging controller: a device that regulates the voltage supplied to the battery for proper charging (and cuts off the power when the battery is full) and which prevents the slow discharge of the battery through the panel at night. (Some, but not all, panels are wired with a diode in line to prevent this type of discharging.) 12-volt chargers and tools can be connected to the car battery directly, but make sure that there is a suitable fuse or breaker in the line—a short circuit across a car battery can produce hellishly high currents. TenOfAllTrades(talk) 14:11, 4 October 2012 (UTC)

My point is the lack of return on investment. You are unlikely to be able to buy the solar panel, charging controller, and rechargeable batteries for less than disposable batteries would cost over the lifetime of those devices. The situation changes when the solar panels are scaled up. However, there are situations where such a small solar panel may be useful to directly use the energy produced, like the example given above of powering a ventilation fan (let's say on a shed without electricity service). StuRat (talk) 16:39, 4 October 2012 (UTC)

One would be wise not to neglect the situations where it's difficult to aquire fresh, charged batteries on a regular basis: hiking in the backwoods, staying in a remote rural cabin, living in a third-world country or war zone where deliveries are infrequent or unreliable. Sometimes it's nice to have the option of a solar charge just in case you forgot to pack batteries, or the power goes out unexpectedly.

As well, I am curious about how you calculated the return on investment in this situation. To do a back-of-the-envelope estimate, the Powerfilm device I mentioned above is selling on Amazon for $72.50 ([1]), including free shipping to the U.S. That charges two NiMH rechargeable batteries (buy four in case of cloudy spells, call that $8 all told) in four hours of sunlight. A quick survey of Amazon puts the cost of name-brand disposable alkaline AA cells at about $0.30 apiece (you'll pay more if you buy them in smaller packages at a bricks and mortar retailer, though). Assuming an average of just four hours sunlight per day, the solar charger saves $0.60 in disposable batteries per day. It pays for its entire $80 purchase price in about four months of continuous usage, or three years of summer weekends. TenOfAllTrades(talk) 20:22, 4 October 2012 (UTC)

1) That's not the device the OP asked about, which would require the additional purchase of a charging unit.

2) You listed the sale price, so let me compare with the sale price I get on disposable AA batteries, which is 8 for $1, or 12.5 cents each.

3) I don't believe rechargeable batteries hold as much of a charge as disposable batteries, especially after many discharge/recharge cycles.

4) I believe they also tend to discharge faster when sitting on the shelf.

5) The unit you linked to looks rather fragile, with folding electrical connections and such. I'd only use that in a window, which means I wouldn't get full sunlight on it most of the day (moving it from window to window might help). If you left that outside to charge for 4 hours a day for 4 months straight, I'd be very skeptical of it lasting. Also, any wind might blow it over.

6) They didn't mention angling it towards the sunlight. That doesn't look very easy to do with this device.

7) Applications which burn through 2 AA batteries a day, every day, are uncommon. Any application which does this clearly needs larger batteries. StuRat (talk) 04:54, 5 October 2012 (UTC)

Actually a decent rechargable NiMH cell, especially a LSD one, can provide more charge then disposable cell, with high drain usage patterns or when compared with zinc carbon primary cells both of which I presume is the case here given the mentioned usage patterns and prices. Cell life depends on the type, but again a decent LSD should get at least a few hundred cycles. Even LSDs do discharge faster compared to primary cells, but it isn't that fast and this seems irrelevent if we are talking about using and charging them regularly as seems to be the case here. Nil Einne (talk) 05:13, 5 October 2012 (UTC)

The batteries I use in my mouse and my camera are rechargeable AA both Duracell and Energiser. As I recall they were touted to last for 1,000 charges at least. That's like 100 bucks each battery at 12c and imagine all the chemical crap that gets flushed out when you are recycling 1,000 batteries... Anyway my batteries were like ten euros or more each for pk of 4 and I'd guesstimate I charge a pair every two days or so. I work that out to last me 8,000 days, or as they say in China, twenty odd years. I think they will be corroded into uselessness by the air before they mechanically pack in. I charge them with a Uniross charger which I believe was cheap and has been used for like 7 or 8 years and couldnt have cost more than 20 euro I think. So around 50 euros+ electricity to replace 8,000 disposeables and even if they are only half as good that's 4,000 which at 12c is about 360 euro. I doubt they'll run €300 in electricity charging and I only have to dispose of them once before starting again. 8,000 AA batteries would measure about 100cm x 30cm x 30cm which is like half a full size wheelie bin and where I live, if you only put bins out every few month's, that will cost you about half of €80 which almost covers the hardware costs to begin with. So, if it is only the electricty I am paying for vs disposeables at about 12c or 8c euro, I'd have to run 250 watts for one hour during the day to be charged 8c. The charger doesn't give wattage rating but I sincerely doubt it runs 250 watts an hour charging all four slots. In fact I know it doesn't because you can get a feel for the wattage of an appliance by the heat it gives out and I estimate a maximum 50 to 100 watts so I'd make an uneducated but careful guess that the rechargeable AAs are more like a fifth or quarter of the cost of the disposeables while the rechargeables are top brands and the disposeables are pound shop (cheapest imports, plastic toys, etc.) But you can't beat a good pound shop all the same. ~ R.T.G 13:59, 5 October 2012 (UTC)

Have you actually had any rechargeable batteries last 20 years ? I tried them, and they seemed to hold so little charge after a year or so as to be useless. That 1000 charge cycle might just mean it will hold some charge up to then, not enough to be useful. Also, time alone may make them go bad, regardless of charge cycles. StuRat (talk) 23:40, 9 October 2012 (UTC)

Tool to remove fuel filler cap?

i have bad wrist atrophy from a injury i cant get the gas cap off my car is there any tools that will help me?--Wrk678 (talk) 05:36, 4 October 2012 (UTC)

Try a large channel lock wrench: [2], or perhaps this type of jar opener: [3]. Also, if the other wrist is OK, why not use that hand ? StuRat (talk) 06:16, 4 October 2012 (UTC)

Or ask someone to help you. Astronaut (talk) 16:41, 4 October 2012 (UTC)

You might also want to replace that gas cap with one which is easier to remove. StuRat (talk) 16:44, 4 October 2012 (UTC)

Would something like one of these help you? - Karenjc 19:22, 4 October 2012 (UTC)

do they make fuels caps that are easier to open for a honda accord ?--Wrk678 (talk) 11:10, 5 October 2012 (UTC)

If you have an auto parts store such as a NAPA or Autozone nearby I recommend talking to someone there. They should have replacement gas caps, and you can see if there are any options that should be easier for you. Looking at Amazon, I don't see anything designed to be easy-open, but there several different styles, one of which may be better than the others for you. 209.131.76.183 (talk) 11:42, 5 October 2012 (UTC)

A gas cap turner, you can order them online, here for example, $15.95. quote: Many of us, especially those with Arthritis or hand injuries, will appreciate this great new tool uses leverage to twist your gas cap open easily and to tighten as well. A tip that may not help with a gas cap (or a bad wrist): when I have trouble with plastic screw caps on bottles, I wrap some double-sided sticky tape around it; gives so much grip you don't have to squeeze, only turn. Ssscienccce (talk) 11:12, 6 October 2012 (UTC)

A good idea, but I'm not sure it will fit all gas caps, and the lever arm looks too short to help much. StuRat (talk) 00:16, 7 October 2012 (UTC)

Tastes of the alkali metal halides

NaCl tastes salty. What do the other alkali metal halides (especially the chlorides) taste like? (Obviously, please ignore the more poisonous ones.) Double sharp (talk) 07:31, 4 October 2012 (UTC)

Look at http://nsrdec.natick.army.mil/LIBRARY/80-89/R81-77.pdf. The predominant taste is salty especially for higher concentrations, but higher molecular weight salts are also more bitter than salty. LiI tastes sour and bitter. Graeme Bartlett (talk) 09:29, 4 October 2012 (UTC)

Thank you Double sharp (talk) 11:07, 4 October 2012 (UTC)

Necessary properties for an element to be a halogen

What properties (if any) would element 117 have to display for it to be counted as a halogen? Please give sources, if possible, as I need this information for the ununseptium article. Double sharp (talk) 07:33, 4 October 2012 (UTC)

Well the name suggests that it should form salts. So with an alkali metal you would get a salt. A Uus^- ion should be possible. I would also expect 7 electrons in the outer shell. But if the nucleus is too short lived to have that many electrons or react to form compounds, then it is not really a halogen! Graeme Bartlett (talk) 11:08, 4 October 2012 (UTC)

The problem with these transuranic elements is that you have to make all sorts of relativistic corrections to the usual formulae. Having seven outer shell electrons is the key thing, as I understand it, but working out what the outer shell is is a little tricky - the usual patterns that make the periodic table work start to break down. --Tango (talk) 11:28, 4 October 2012 (UTC)

Would it have to be a nonmetal to be possibly a halogen? Would it have to show a −1 oxidation state (and must that be the most common oxidation state)? If a halogen must have the −1 state as its most common, Uus would probably not be able to be counted as a halogen, as it is predicted that the +1 and +3 states would be more common. (The inert pair effect would also practically reduce the octet rule to a sextet rule, as the 7s subshell is very stabilised by relativistic effects, so Uus probably can only use 5 electrons for bonding, but would still be one electron short of a full outer shell.) Double sharp (talk) 12:26, 4 October 2012 (UTC)

Concepts like "metal" and "nonmetal" also make little sense when dealing with large transuranium elements. As noted by several people above, the entire classification system we impose on the Periodic Table (for our own purposes as a heuristic means of understanding trends in properties) starts to break down with these larger elements. On a very simplistic sense, we would expect it to be "halogen-like", but less so than any other halogen; Astatine displays some quite non-Halogen properties, including observed elemental cationic oxidation states. How much less-halogen-like Uus would be is purely speculative as you'd need enough to empirically classify it, which we haven't got yet, and may never get. --Jayron32 13:38, 4 October 2012 (UTC)

Just to throw my one in there: I expect it to be a brittle, semi-conducting metalloid, with a melting point in the 500/600s, with poor halogenic properties. Plasmic Physics (talk) 21:21, 4 October 2012 (UTC)

So, what exactly are the halogenic properties? What properties are necessary for an element to be a halogen? Double sharp (talk) 07:44, 5 October 2012 (UTC)

I'd say a strong oxidant (ability to oxidise water and form an acidic solution), and a diamagnetic, singlet ground state, and of course have an affinity for the -1 state. Plasmic Physics (talk) 09:03, 5 October 2012 (UTC)

(unindent) "In the 500/600s"? I would think that with the rate of decay which Uus isotopes exhibit that it won't ever cool to a temperature range with significant chemistry (i.e. 100's or low 1000's of degrees). Not only will chemical properties break down with that many shells, but also at that high temperature.

- ¡Ouch! (^{hurt me} / _{more pain}) 14:58, 8 October 2012 (UTC)

iso	NA	half-life	DM	DE (MeV)	DP
286Uut	syn	19.6 s	α	282Rg
285Uut	syn	5.5 s	α	281Rg
284Uut	syn	0.49 s	α	280Rg
283Uut	syn	0.10 s	α	279Rg
282Uut	syn	73 ms	α	278Rg
278Uut	syn	0.34 ms	α	274Rg

Well, that's because we can't synthesise Uus isotopes with enough neutrons using present technology. There's a dramatic increase of half-life in the Uut isotopes when more neutrons are added. ²⁷⁸113 has a half-life of just 0.34 ms. But ²⁸⁶113 (with eight more neutrons) has a half-life of 19.6 s – 57600 times as long. (It looks like an exponential trend.) Double sharp (talk) 06:02, 9 October 2012 (UTC)

Using an NPN transistor as a switch - optimal circuit

Over the years, I've come across two circuits designed to use an NPN BJT transistor as a switch (i.e., the transistor is either off or saturated) and I'm curious as to whether or not one is superior (generally speaking).

The first type of circuit places the load and transistor in series; when the transistor is saturated, the load is connected to ground, providing a path for current and turning the load on. This circuit is ubiquitous on the internet; an example is on page 3 of this pdf.

The second type of circuit doesn't seem to be as common (at least on the internet); in its layout, the transistor and the load it controls are in parallel, so the load is off when the transistor is saturated (since, in this condition, the transistor provides a lower resistance path to ground than the load) and on when the transistor is off. An example of this type of circuit is on page 37 of this pdf.

Generally, is one of these two circuit layouts better than the other? With the second circuit, it seems possible that a small current could enter the load when the transistor is on (although in practice I imagine the load impedance would have to be quite low for this to happen), so I suppose the first circuit is more controlled in this respect.

Any thoughts on this would be appreciated. 142.20.133.132 (talk) 14:51, 4 October 2012 (UTC)

Your second citation doesn't make much sense, as there is no page 37. If you meant what's on page 2-9 Calculation of a Saturated Transistor Circuit, you have misunderstood the intent of this section; Rc is a resistance representing the load, but in accordance with analysis convention, the voltage at the collector is measured with respect to earth.

However, your question about the relative merits of series and parallel switching can still be answered. The most common case is that you want full voltage on the load when on, and zero current when off. That naturally & obviously suggests a switch in series. In the vast majority of cases, the load does not see the full voltage, as the transistor saturates with around 0.3 V accross it, but if necessary (it usually isn't) you can compensate by making the supply volage a bit bigger. The transistor isn't perfect in the off state either - a leakage current still flows. But the leakage is generally negligible in its effect on the load. Very often, the load is inductiove - it's a relay coil, a motor, etc. This presents a problem, when you turn off the current in an inductance, the magnetic energy has nowhere to go, so it creates an inductive kick voltage (known as back EMF), which can easily destroy the transistor. This can be fixed by connecting a diode in parallel with the load, or (less commonly) a resistance or RC circuit, or even just specifying a transistor with a very high voltage rating, or some combination of these methods. Using the diode will slow down the relay release to some extent.

The advantage of using the transistor in parrallel is that the back EMF issue cannot occur, as the magnetic energy is "dumped" in the transistor when the transistor turns on. The voiltage across the transistor cannot exceed the supply voltage. Parallel operation has two major disadvantages: (1) there must be a current limiting resistance in series with the transistor/load combination, and this resistance must dissipate significant power, making the circuit energy inefficient. (2), because the inductance keeps current flowing in the transistor, the relay is very slow to release. However, by using a high supply voltage and a high resistance, the relay operate time can be reduced slightly without exceeding its coil power rating.

Typical times for small relays:-

Series connection - operate 20 mS; release 25 mS; if diode used release 50 to 300 mS;

Parallel connection - operate 15 to 20 mS; release 300 to 1000 mS

Other pros and cons centre around reliability. If the diode fails to open circuit, the circuit will continue to work until the transistor has had enough of the back emf. A technician may replace the faulty transistor but forget to replace the diode. That means the system will fail gain, perhaps within hours or weeks. Correctly designed, the parallel circuit is inherently more reliable, as high transient voltages cannot occur, and there is one less semiconductor. Sometimes, the application requires the system to fail safe or start safe. Failing safe or starting safe may require the load to be energised (or not energised) whenever the power is on, but the input signal to the trasistor is not present (as say a micro-controller chip hasn't booted up yet).

Keit124.182.43.236 (talk) 01:45, 5 October 2012 (UTC)

Thanks for the information; that's quite a few interesting factors. I've only ever connected transistors and their controlled loads in series, so it's good to know about the benefits and disadvantages of a parallel layout. (Also, next time I'll be sure to provide both the document page number and the PDF page number when the two differ!) 142.20.133.132 (talk) 15:06, 5 October 2012 (UTC)

What constitutes a bacterial species?

If species is defined by the ability of individuals in the population that are able to reproduce with each other or amongst themselves, and species evolve over time, then what constitutes a bacterial species? Will the bacterial species keep its name or change its name when it evolves? Can a bacterial species die out? If it dies out but its genes get integrated into a different species somehow, then has a new species evolved, or the living species have evolved and the dead species is dead? 140.254.226.206 (talk) 16:19, 4 October 2012 (UTC)

A certain measure of genetic difference would be one way to distinguish between species with asexual reproduction. So, after it evolves enough, yes, it becomes a new species and gets a new name. Such species can also die out completely. If a new species evolves as the old one dies out, that situation is no different than sexually reproducing species. StuRat (talk) 16:30, 4 October 2012 (UTC)

The OP would do well to read the article titled Species problem. --Jayron32 20:20, 4 October 2012 (UTC)

It's probably mentioned in species problem, but I found ring species particularly fascinating when I learned about it. Vespine (talk) 00:41, 5 October 2012 (UTC)

The species problem article doesn't even discuss the most serious issue that arises with bacteria, which is that they can swap DNA with each other, including, on occasion, with types of bacteria that are quite dissimilar to them. Some biologists have argued, at least semi-seriously, that all bacteria ought to be considered as one single megaspecies. Looie496 (talk) 04:25, 5 October 2012 (UTC)

Horizontal gene transfer is not limited to bacteria. So unless you're going to take that argument all the way...Someguy1221 (talk) 04:32, 5 October 2012 (UTC)

As a rule of thumb, two bacteria are generally considered to be in the same species if their 16S rRNA are at least 99% identical. Two bacteria are often in the same genus if the 16S rRNA are at least 94% identical. An official declaration of a new species / genus requires more detail than that, and not all species / genera boundaries meet those criteria, but it is a rough guide that is easy to use because 16S rRNA is universal in bacteria, highly conserved, and frequently used as a means to identify particular bacteria. Dragons flight (talk) 01:22, 5 October 2012 (UTC)

SSC and Higgs

If the Superconducting Super Collider had been built, would it have been able to detect the Higgs particle? Bubba73 ^{You talkin' to me?} 18:21, 4 October 2012 (UTC)

Presumably, as the SSC's designed energy level was substantially higher than the LHC's (20 TeV to 7 TeV, for protons), and the gain in energy level over Tevatron was a primary reason that the LHC was able to gather its Higgs-related data. — Lomn 18:39, 4 October 2012 (UTC)

Resolved

Thanks. Bubba73 ^{You talkin' to me?} 19:09, 4 October 2012 (UTC)

We could have built that. Bubba73 ^{You talkin' to me?} 15:50, 5 October 2012 (UTC)

What are those spidery black things on Mars?

See this article. Is there a name for these objects, and what sources do we have on them? Thanks. μηδείς (talk) 18:35, 4 October 2012 (UTC)

The Spiders from Mars? :-) Bubba73 ^{You talkin' to me?} 19:10, 4 October 2012 (UTC)

I think they are usually just called dark dune spots (I don't really endorse the redirect to Martian geyser). There are plenty of people working on Martian dunes so you can find quite a lot of journal articles. Sean.hoyland - talk 19:18, 4 October 2012 (UTC)

If there are people working on the Martian dunes, that's a major news story. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:09, 5 October 2012 (UTC)

Great! μηδείς (talk) 21:54, 4 October 2012 (UTC)

Resolved

Segmented sleep and animals

Segmented sleep makes the case that before the Industrial Revolution, people would sleep in 2 phases, being awake in the middle of the night. Unfortunately, the amount of research is not overwhelming but some examples sound convincing. I'm wondering if the thesis is right. If so, I'd like to know if animals, in particular primates, also wake up during the night. Joepnl (talk) 21:39, 4 October 2012 (UTC)

A lot of animals are crepuscular, active in low light and inactive mid-day and mid-night. If I am not tired and go to bed early I sleep segmentedly. I am not a fan of it. I prefer a solid 8 hours. μηδείς (talk) 21:53, 4 October 2012 (UTC)

My gut reaction is that it is no accident that humans (and other primates) have rods that can make out the landscape by moonlight, and that in times past moonlight would have been expected to have a very direct and practical effect on behavior. I have a suspicion that things like "harvest moon" and "hunter's moon" are more than just poetic phrases, and the articles appear to support that. So I would expect people to be biologically adapted to making a fluid response to the changing lunar cycle. Doing a quick search for primates and moonlight I found [4], which looks like a useful starting point. Wnt (talk) 17:18, 5 October 2012 (UTC)