Science desk
< December 6	<< Nov \| December \| Jan >>	December 8 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

December 7

Physics - battery questions.

What makes a rechargeable battery, a rechargeable battery, and a non-rechargeable battery a non-rechargeable battery? I'm not looking for a philosophy answer, which is "1 is where the reactions can go in the backwards direction." That's an answer a pure philosopher can say, I'm looking for more of a science answer, which I think is more than just different materials or elements. 67.175.224.138 (talk) 00:01, 7 December 2018 (UTC).[reply]

Notice that batteries considered non-rechargeable, like alkaline ones, can be recharged, but not at home simply by electrical means. Primary cell has many leads that can be followed to understand the difference. --Doroletho (talk) 01:06, 7 December 2018 (UTC)[reply]

(Sorry about the relative lack of references in what follows, but I do not know the English keywords to search for.) The chemistry-electricity conversion can be reverted for pretty much anything (see electrolysis). The problem is how to cause only the reaction you want to cause, even though applying a current does not really give you a choice. If there are multiple possible redox reactions caused by electrolysis, some might irreversibly damage the battery.

I had read somewhere that the electrode potentials you can have in a rechargeable battery are limited by that of the H20 -> H2 + 0.5O2 electrolysis, because water is always around in those technologies and you do not want to create hydrogen, and this explains why you cannot have large-voltage rechargeable batteries, but I cannot find a ref that shows it. Tigraan^{Click here to contact me} 17:59, 14 December 2018 (UTC)[reply]

Indo European languages: A Disease Hypothesis

Marija Gimbutas's theory for the widespread prevalence of Indoeuropean languages is, roughly, that the conquering power and range of mounted Indo european horse warriors made the language spread rapidly and widely. Colin Renfrew's theory might, roughly, be that the original indoeuropeans spread rapidly and widely because of the new farming techniques they introduced when they migrated and when the new kind of farming was accepted by the people they met, the indoeuropean language tended to be accepted or prevail. What I'm wondering is, if instead, the Indo Europeans probably innocently carried some kind of terrible disease, such as plague, that they were resistant to, and the peoples in the places the Indo Europeans migrated to were then wiped out by the disease. The reason I'm thinking this is I read part of the article in the Atlantic that just appeared about the plague killing people in Sweden 4900 years ago. The events discussed might be entirely unrelated to an IndoEuropean diaspora, but gave me the idea, which I bet isn't original to me. So if there is information available about this or if you can give reasons why the idea is good or bad, i'd appreciate it. Rich 144.35.45.56 (talk) 02:45, 7 December 2018 (UTC)[reply]

The genetics of people are different to the history of the language. The ancestry of the speakers gives a different story to the language grouping, so it appears that people living in an area adopted the language. Also it appears that the Indoeuropean languages spread in the Bronze Age, and not with the introduction of farming (Neolithic). Graeme Bartlett (talk) 04:49, 7 December 2018 (UTC)[reply]

Not following your reasoning144.35.45.56 (talk) 05:58, 7 December 2018 (UTC)[reply]

You seem to assume that the Indoeuropean languages spread because their speakers largely replaced the previous inhabitants speaking other languages. If that were the case, than the phylogenetic tree of the Indoeuropean people would look very similar to the phylogenetic tree of the Indoeuropean languages. But if we look at the actual relationships, it seems as if the languages spread primarily by being adopted by the existing population, not by a replacement of populations. Indoeuropean speakers did not replace the others, the others became Indoeuropean speakers by learning the language. --Stephan Schulz (talk) 08:22, 7 December 2018 (UTC)[reply]

In the Portuguese and English speaking countries in the New World, speakers of Indo-European languages certainly replaced the local population. I'd say by germs and steel. In the Spanish speaking countries there, partially too. --Doroletho (talk) 14:22, 7 December 2018 (UTC)[reply]

That it happens in one place, doesn't mean it happens in all places, all the time. The way in which a language moves into a specific geographic area, and sometimes it is because one population displaces another, sometimes it is because the population stays where it is, and the language changes. --Jayron 32 14:55, 7 December 2018 (UTC)[reply]

Sure, according to Indo-European migrations the expansion wasn't always violent. the colonization of the Americas was just the last chapter of the whole story. But with a population of 1 billion, the continent is a significant share of all speakers of Indo-European languages.--Doroletho (talk) 18:07, 7 December 2018 (UTC)[reply]

Perhaps you are thinking of this? Abductive (reasoning) 05:03, 7 December 2018 (UTC)[reply]

You have to ask why people would bother speaking a language like Indo-European. If people start out speaking a language with a very rich grammatical structure where there is a massive redundancy in each sentence, then over a just a few generations that language will be end up being simplified, redundancies will be eliminated, grammatical constructions that are not needed will go out of the window. So, the idea that local people had spoken Indo-European amongst themselves is not so credible, they certainly would not have adopted that language in the sense of stop speaking their own language and decide to speak Indo-European. What happened was that Indo-European was their version of today's English or the Latin on previous centuries, i.e. a language needed to communicate with people living elsewhere who speak a different language. Then over time Indo-European would have influenced local languages, just like English has had an influence on many languages. This could then have led to the local language being end up replaced by Indo-European on the longer term, but at the end of any such replacement process a severely bastardized form of Indo-European would be spoken. Count Iblis (talk) 18:31, 7 December 2018 (UTC)[reply]

What type of spider is this?

PseudoSkull (talk) 04:26, 7 December 2018 (UTC)[reply]

Orb-weaver spider. Abductive (reasoning) 05:01, 7 December 2018 (UTC)[reply]

Too much hygiene

Has there been research done / is there a medical consensus on whether there can be such a thing as too much hygiene, whether at some point being extra meticulous about it doesn't decrease or even increases a person's chance of getting sick in the future? A while ago I read about a study that found that people drinking 2 units of alcohol per day had fewer colds than those who didn't drink at all. Assuming that this isn't due to famed beneficial effects of alcohol, it would indicate that people who drink a lot have a lifestyle that has them experience less colds (despite that I expect these people are less careful about their hygiene, not to mention that they suffer from alcohol's known deleterious effects). Are there more studies suggesting similar conclusions? 93.136.49.90 (talk) 04:49, 7 December 2018 (UTC)[reply]

See Hygiene hypothesis and Alcohol and health. Graeme Bartlett (talk) 04:51, 7 December 2018 (UTC)[reply]

Anything specifically about the effects of adult lifestyle? Hygiene hypothesis seems to be only about how childhood hygiene affects later life. As in, for example, do people who have a high degree OCD about cleaning get sick less often than, say, the person with 80th percentile hygiene? 93.136.49.90 (talk) 05:58, 7 December 2018 (UTC)[reply]

Most recently I've heard it's best to not avoid everyday bacteria, since exposure to them keeps your immune system and microbiome in shape. So they stopped selling (or at least recommending) antibacterial soaps.[1] If you're OCD about cleaning (so you're not exposed to anything) but then you slip up, you can supposedly get infected more easily than someone with stronger immunities. This was interesting. 173.228.123.166 (talk) 07:28, 7 December 2018 (UTC)[reply]

For clarity, the recommendation against antibacterial soaps is not simply because of concerns they may interfere with the normal microbiome (and other possible negative effects), but also because we don't really know that they even reduce bacterial load on the skin. Just because something has an antibacterial effect and is useful in some situations doesn't mean it's going to be the same in all situations. See e.g. [2] and also [3] and [4]. This is not to disagree that there's increasing recognition disruption the normal microbiome can actually make things worse. E.g. our Human microbiota article links to this somewhat old (and popular science) source [5] Nil Einne (talk) 07:45, 8 December 2018 (UTC)[reply]

Another relevant item, but still relating to childhood, is the history of poliomyelitis. It was only in the 20th century that polio began to afflict people in large numbers, and this is believed to be the result of impoved sanitation stopping people from getting it during early childhood when it is less dangerous. --76.69.46.228 (talk) 07:37, 7 December 2018 (UTC)[reply]

Thus getting cholera instead of polio. ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:30, 7 December 2018 (UTC)[reply]

Most of our modern lifestyle habits we stick to have never been subject to rigorous scientific tests. If we now get suspicious that some aspects of our modern lifestyles are not so healthy, then we'll investigate but we'll do so giving our current habits the benefit of the doubt. So, the null hypothesis will be that whatever we're dong now is good, and we require a statistically significant result for an alternative hypothesis. This means that we'll keep up with a lot of put very unhealthy habits as we're not going to be able to do all the research necessary to debunk all of our habits that we've adopted throughout history without a shred of evidence. Count Iblis (talk) 17:50, 7 December 2018 (UTC)[reply]

Theoretically speaking, is it possible to reverse plastination?

I have heard about plastination being an alternative to cryonics. Obviously we don't have any way to reverse plastination right now, but I was wondering if reversing plastination is theoretically possible. In other words, I was wondering if it was possible to make a plastinated brain living once again.

Basically, if a brain is plastinated, it's possible that we might eventually be able to scan its contents onto a computer or something, but that would simply create a copy of your brain instead of actually bringing your brain back to life.

Anyway, any thoughts on this? Futurist110 (talk) 06:26, 7 December 2018 (UTC)[reply]

If you are going to guess what method will allow revival (right now the answer is "none of them") and want to roll the dice on something besides freezing (I can see the appeal -- the idea of someone keeping that freezer repaired and running for hundreds of years without a single thaw seems really risky) why not go with Freeze-drying, followed by storage in a well-sealed container containing an oxygen free atmosphere (See Oxygen scavenger)? --Guy Macon (talk) 08:02, 7 December 2018 (UTC)[reply]

AIUI, very clearly not.

Plastination is a process of impregnating tissue with a polymer resin, such that it is well-preserved long-term and may be studied by looking at it with the naked eye. However it's not a process suitable for preserving microscopic detail. Structures such as cell walls are deliberately breached, so that the preserving resin gets inside them. There are similar issues in woodworking, and the manufacture of MDF boards. The simpler processes place resin around the wood fibres, but a weatherproof board such as Tricoya also requires these fibres to be made permeable or otherwise opened up, so that the resin gets inside.

As the sort of material you're presumably interested in retrieving would be at very small scales, this cell damage would be a serious problem for it.

Cryonics has the same problem. When you freeze a body largely composed of water, ice crystals form and these burst the cells. A technical problem for cryonics is in replacing the water before freezing, so that they avoid this crystal damage. Some criticisms of cryonics dispute that this is achieved long-term.

There's also the need to reverse the plastination. If there's any sort of polymerisation involved, then that would need to be reversed to make the resin non-rigid. Reversing polymerisation needs a solvent, and it's often difficult to find such a solvent which doesn't cause its own damage to other materials, such as the cells. Andy Dingley (talk) 11:49, 8 December 2018 (UTC)[reply]

Plastination can be considered a form of embalming. I have never heard about reversing it. Ruslik_Zero 20:11, 8 December 2018 (UTC)[reply]

I think your idea of scanning the contents and making a computer copy is the best chance. Why anyone would bother I don't know, would we want to revive ancient Egyptians? What would be the point? Even with the scanning it would be just to get the answers to some questions then switch them off again rather than bringing them back to life and get them to be part of society. Dmcq (talk) 21:26, 8 December 2018 (UTC)[reply]

See here:

"However, the challenge is a complex one, as the human brain contains 86 billion brain cells (known as neurons) each with an average of 7,000 connections to other neurons (known as synapses). Current computer power is insufficient to model a entire human brain at this level of interconnectedness."

And here:

"The large-scale neuromorphic machines are based on two complementary principles. The many-core SpiNNaker machine located in Manchester (UK) connects 500,000 ARM processors with a packet-based network optimized for the exchange of neural action potentials (spikes). The BrainScaleS physical model machine located in Heidelberg (Germany) implements analogue electronic models of 4 Million neurons and 1 Billion synapses on 20 silicon wafers. Both machines are integrated into the HBP collaboratory and offer full software support for their configuration, operation and data analysis." Count Iblis (talk) 03:04, 10 December 2018 (UTC)[reply]

Senses and intelligence

Is there any "established" way of measuring the amount of sensory information that a brain receives? If so, how do different animals compare?
Is there any known link between the development of an animal's senses and its intelligence? E.g. do animals with "better" vision tend to be more intelligent.
Are there any measures by which humans have particularly advanced or capable senses?

I'm aware that these question suggest that certain attributes are better defined than they are. I know that measurement of animal (and human) intelligence is controversial, and whilst certain aspect of vision may be measurable, there is no straight answer to the question "which animal has the best eyesight?". However, I am curious if, in as much as there is agreement/have been studies, what is known/suggested.--Leon (talk) 20:55, 7 December 2018 (UTC)[reply]

Some but not all animal camouflage seem to be not good enough for humans. Predatory birds can have astoundingly good day vision though, maybe they're better at this than humans. Sagittarian Milky Way (talk) 21:19, 7 December 2018 (UTC)[reply]

In response to your third question, see petrichor and geosmin ("The human nose is extremely sensitive to geosmin and is able to detect it at concentrations as low as 5 parts per trillion"). PaleCloudedWhite (talk) 21:35, 7 December 2018 (UTC)[reply]

Ever since Gestalt, many psychologists have suggested it's not very useful to try and separate sensory input from the neurological mechanisms which are needed to use it. Aspects of the human sense of touch, for example, may not be as well developed as those in some insects, but how many other animals can read braille? Here's a 2009 comparative psychology paper entitled "In search of a unifying theory of complex brain evolution" by Leah Kubitzer, at the Center for Neuroscience and Department of Psychology, University of California, Davis, CA, which you might find interesting: [6]. Martinevans123 (talk) 21:56, 7 December 2018 (UTC)[reply]