Wikipedia:Reference desk/Archives/Science/2020 August 12

= August 12 =

Spider colors
What are the least obscure colors that make this true?: "no known spider is mostly [color]" Sagittarian Milky Way (talk) 14:42, 12 August 2020 (UTC)
 * Here's a searchable list of spiders by color. Oddly, tan is listed as lowest in number.    -- There actually are blue spiders and even purple ones : --2606:A000:1126:28D:A40B:6182:4554:2346 (talk) 18:43, 12 August 2020 (UTC)
 * I see "Tan (403)" listed as rank #3; "Purple (13)" is listed as lowest, rank #13. You can select multiple colours; when you tick a box the numbers change and the entries are accordingly rearranged. The feedback is suboptimal; you have to scroll the list to see your current selection. --Lambiam 07:16, 13 August 2020 (UTC)
 * We have a website for everything... Good find. Sagittarian Milky Way (talk) 21:08, 12 August 2020 (UTC)
 * What, no plaid? ←Baseball Bugs What's up, Doc? carrots→ 21:19, 12 August 2020 (UTC)
 * Plaid spider? --2606:A000:1126:28D:F9E7:DA6C:4ED6:68A1 (talk) 00:06, 13 August 2020 (UTC)
 * Wearing the tartan of the clan O'Rachnid. ←Baseball Bugs What's up, Doc? carrots→ 06:39, 13 August 2020 (UTC)
 * Scottish spider genetic engineeringcists intensify. Sagittarian Milky Way (talk) 21:27, 12 August 2020 (UTC)
 * What about ecru? Puce? Viridian? - Nunh-huh 21:42, 12 August 2020 (UTC)
 * Or, ... cerise, chartreuse and aqua? --2606:A000:1126:28D:F9E7:DA6C:4ED6:68A1 (talk) 23:45, 12 August 2020 (UTC)
 * What a great resource: I'm surprised we have never seen it here before (or to not have stumbled upon it myself in the past). Whoever designed the approach was quite clever to make colour (rather than more complex morphologies or phenotypical features) the main search criteria.  I'm seeing some taxons here I was previously unfamiliar with: check out Poecilotheria metallica! Snow let's rap 17:57, 14 August 2020 (UTC)

Where does the energy go?
Why do old cellular telephonic batteries not get hot from apparently short circuiting half their power in less than 1 second? Sagittarian Milky Way (talk) 21:24, 12 August 2020 (UTC)
 * Too much internal resistance maybe? Earl of Arundel (talk) 02:21, 13 August 2020 (UTC)
 * They are not, usually, "short circuiting half their power". For batteries, capacity is usually estimated based on the remaining voltage (with a suitable voltage/charge model). In the case of LiO-Batteries, for older batteries, voltage does not drop significantly until they are nearly empty. If you have a simple model, it appears as if they are still fairly charged, even though the usable charge is very small. If a LiO-battery really short-circuits internally, you get very hot batteries indeed. --Stephan Schulz (talk) 07:18, 13 August 2020 (UTC)


 * Electrochemical cells (batteries) obey something called the Nernst equation, which basically says that voltage is proportional to concentration. The deal with solid state batteries is that in solids, concentration does not vary significantly with amount, so voltage remains basically at the maximum voltage until right before the battery "dies", at which point it goes from "full voltage" to "zero voltage" essentially instantly (in an ideal world, spherical cow, standard disclaimers, etc. etc.)  In other cells, like a lead acid battery, which is a solution-based battery, you'll see a slow drop in voltage over time.  If you've ever been driving a car with a dead alternator, you'll be familiar with the effect of slowly losing systems like the radio and where the lights slowly dim over an extended period of time as the battery slowly loses power before it doesn't have enough power to run the car anymore.  -- Jayron 32 13:00, 13 August 2020 (UTC)
 * You're jumping to the conclusion that, because the reported battery charge changed dramatically, it means the battery shorted itself and discharged a lot of power. In most fairly-recent cell phones, the controller chip inside the lithium-ion battery reports an estimated charge level to the phone. Like many battery types, lithium-ion batteries slowly degrade with time regardless of whether they're used. If the phone hasn't been switched on in a while, the chip will likely need to recalibrate, which can take time. The high-capacity li-ion batteries used in higher-end electronics are quite sophisticated, and the controller can take individual cells of the battery "offline" if they fail. If this happens, it will affect the reported charge level. There are numerous failure modes, not all of which involve an internal short. Since li-ion batteries can store quite a bit of energy and have the potential for violently releasing it in the event of catastrophic failure, one job of the battery controller is to ensure safety, by capping charge levels or taking cells offline before things get out of hand. The infamous Note 7 battery failures mentioned above were caused by faulty separators which made the cells prone to shorting, which provides a good example of what can happen. --47.146.63.87 (talk) 23:57, 14 August 2020 (UTC)