Wikipedia:Reference desk/Archives/Science/2021 June 7

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June 7

Cell phone chargers, can they be plugged in wall if you're not charging?

I don't know how to ask this question in the right way that arrogant people won't take offense to it. Is it true if you're done charging your cell phone, you should unplug it from the wall, so no bad things can happen to it (the charger), or the possibility of? My next question, if there is any, will depend on the outcome of the 1st question. 67.165.185.178 (talk) 04:05, 7 June 2021 (UTC).

I hear a high-pitched tone from some of my chargers whether they are charging a phone or not, suggesting that they are electrically active. I recall reading that there is a concern that chargers represent a fire hazard, and that to mitigate this hazard, one should use a power strip and make sure that the charger is not positioned in a way that would allow flames to spread to curtains and other flammable items. Now, if you are trying to maximize the lifespan of the charger, I think it's a wash between leaving it plugged in all the time, and manhandling it by unplugging and plugging it back in twice a day. Abductive (reasoning) 04:50, 7 June 2021 (UTC)

Lifespan of the charger? Weird, people usually say lifespan of the battery. And to answer Nil Einne's question, is there a distinction between leaving the phone connected to the charger, when the charger is not connected to the wall outlet?? 67.165.185.178 (talk) 10:41, 7 June 2021 (UTC).

You asked if bad things could happen to the charger. Abductive (reasoning) 12:45, 7 June 2021 (UTC)

Yea as in fire or electrical hazards, not whether it reduces the ability for the charger to work. But if that is true too, I am curious about that. 67.165.185.178 (talk) 13:26, 7 June 2021 (UTC).

I've had a charger die, but it suddenly stopped working for no obvious reason. Presumably they are designed to fail without bursting into flames. Abductive (reasoning) 15:00, 7 June 2021 (UTC)

(EC) Unless you're talking about some extremely crappy charger violating all safety standards (e.g. something bought off AliExpress or eBay coming directly from China but not with a phone and not an authentic charger from a reputable brand), there is no real harm from leaving it plugged in. However some would suggest unplugging it to reduce vampire power usage although I don't believe standby power usage on mobile phone chargers has ever been that bad (especially after the move to switched-mode power supply), and standards have improved in recent years. So it's likely vampire power should be low and probably not a significant concern, especially if it's a charger that came with the phone and was sold in the EU or part of the US. Note your question is fairly unclear if you mean you're simply leaving the charger plugged in or the phone plugged in to the charger. If you mean the latter, bear in mind that leaving lithium ion batteries at high states of charge all the time tends to shorten their lifespan. However because consumers expect their phones to be 100% or close to it when they disconnect them from the charger if it's been long enough, most phones will try to keep their battery topped up when plugged in. So disconnecting your phone after charging tends to be better for its lifespan especially if you otherwise tend to leave it plugged in for ages and you don't mind it only being 80-90% or whatever when you might take it with you. In other words, while there is no harm to the charger there is sort of harm to the battery. (But not normally dangerous harm.) Some phones allow you to reduce the maximum state of charge, doing this even with leaving it plugged in may actually improve lifespan compared to letting it go to 4.2V (or whatever end point) and then disconnecting it quickly although I don't have any data on that. Nil Einne (talk) 04:53, 7 June 2021 (UTC)

floating in water and gravity

My gut tells me yes but I have no idea how to explain it. I saw a picture of a swimming pool between two buildings (several stories up) with people in it. Clearly, the builder figured out how to ensure that the pool would not collapse from the weight of the water (plus other things such as movement of the buildings, etc.). My question is: does a person floating in the water add weight to the pool. If the pool was empty, I can easily understand the added weight because the person is not floating; if the person was floating in the air, they would not add weight. I know the body will displace water but I don't know how it adds weight if the person is floating. 70.26.17.168 (talk) 04:14, 7 June 2021 (UTC)

If the pool has an overflow drain and is kept full of water right up to the overflow drain, then when a person gets into the water they will displace an equal mass of water, which goes down the drain, and the total weight to be supported does not change. If it doesn't have such a drain or it isn't kept full right up to the drain (and that would be my guess), then the person in the water does add to the weight that must be supported. --184.145.50.201 (talk) 04:39, 7 June 2021 (UTC)

Afterthought: That pool is only partly on the bridge between the buildings. Even if there is an overflow drain such as I described, when water is displaced only part of it is water that would have been on the bridge. Therefore some of the person's weight must be added to the load on the bridge. --184.145.50.201 (talk) 04:59, 7 June 2021 (UTC)

No, that afterthought is wrong. Any floating body is displacing exactly its weight, as per Archimedes' principle. The weight on the bridge remains the same, as long as that volume of water is removed from the pool. Now if that person is actively swimming, and thus raises its center of gravity above the natural position, then it would indeed add additional force to the bridge. --Stephan Schulz (talk) 06:36, 7 June 2021 (UTC)

The weight on the bridge remains the same as long as that weight of water is removed from the bridge, but some of it will be removed (in my hypothetical case) from the other part of the pool. --184.145.50.201 (talk) 07:04, 7 June 2021 (UTC)

That does no matter, as long as the different parts of the pool are in communication. You can do various thought experiments. E.g. let the person swim from one end of the pool to the other. Does this change the weight distribution? (No, it does not). Or consider a big raft covering nearly all of the pool, with people moving around on it. Does this change the weight distribution? (No, it does not, if we abstract from second-order effects like temporary waves). Or consider that same raft, with people initially distributed in two equal groups at the ends (i.e. not over the bridge portion) and then coming together in the middle). Again, not change in weight distribution. Also not, if they then jump from the raft directly into the water... --Stephan Schulz (talk) 10:17, 7 June 2021 (UTC)

After further consideration, I withdraw the claim. Thanks for the correction. --184.145.50.201 (talk)

But if a person swims underwater, they displace their volume rather than their mass (probably not much difference for most people). Alansplodge (talk) 11:24, 7 June 2021 (UTC)

An interesting related concept is the Falkirk Wheel and other caisson-style boat lifts, where a tub with constant-depth water has the same mass whether or not a boat is in it. DMacks (talk) 07:58, 7 June 2021 (UTC)

Ah, I saw a video version of it, on Facebook, and it was in London, England. And ~11 stories high. 67.165.185.178 (talk) 11:02, 7 June 2021 (UTC).

Sky Pool: World's first 'floating' pool between tower blocks. Alansplodge (talk) 11:21, 7 June 2021 (UTC)

When a person jumps into the swimming pool, the weight of that person is added to the weight of the pool and therefore the weight that must be supported by the building. When the person enters the water, the surface of the water is raised by a tiny amount (equal to the weight mass of the person divided by area of the surface of the water in the pool, all divided by the density of water). Because the surface of the water has been raised by a tiny amount, the water in the pool is a tiny bit deeper than it was before the person entered. The water is a tiny bit deeper so the pressure on the floor of the pool is increased by a tiny amount; and this increased pressure acting over the floor of the swimming pool means the force acting on the building is a tiny bit greater. In fact, the small increase in force is exactly equal to the weight of the person! Dolphin (t) 12:44, 7 June 2021 (UTC)

if the person was floating in the air, they would not add weight. I'm not sure exactly what you mean by a person "floating in the air", but if, for example, the person were flying similarly to a bird, by applying downward pressure to the air, they would indeed add weight to what was below them. This is similar to the Birds in a truck riddle. The download pressure that the birds transmit to the air is in turn transmitted to what is below them. If the person were a helium balloon or some other object floating by buoyancy, then they would indeed not add weight to what is below them, I think. CodeTalker (talk) 19:12, 7 June 2021 (UTC)

Thanks everyone. I now have a better understanding of how this works. My reference to "floating in the air" was as in levitating (impossible, I know) so the bird analogy did not fit for what I was thinking . . . but a helium balloon does fit. 70.26.17.168 (talk) 04:29, 9 June 2021 (UTC)

Piltdown Man

After it was established, once and for all, that the Piltdown Man skull had been faked, what was done with it? Just curious. --184.145.50.201 (talk) 06:54, 7 June 2021 (UTC)

It was put on display at the Natural History Museum, London for the 50th anniversary of its debunking, so it is safe to assume it is in their collections. Abductive (reasoning) 08:16, 7 June 2021 (UTC)

Makes sense; thanks. --184.145.50.201 (talk) 10:40, 7 June 2021 (UTC)

Technicium and Promethium - link to "Why?" article.

Neither Technicium and Promethium have links to the "Why" they are radioactive. I believe it has to do with the even/even , even/odd, odd/even,odd/odd stabilities for N/Z, but I can't find it. Can someone point me to the right article (so I can link it somehow to the articles of the two elements?) or show me where it is linked.Naraht (talk) 15:38, 7 June 2021 (UTC)

Why is Technetium radioactive?, Why is Promethium the only radioactive Lanthanide?. --Jayron32 15:41, 7 June 2021 (UTC)

Jayron32 I thought that there was a wikipedia article that went into this.Naraht (talk) 19:31, 7 June 2021 (UTC)

Something related to Magic number (physics)? DMacks (talk) 02:12, 8 June 2021 (UTC)

Perhaps the Mattauch isobar rule. Pinguinn 🐧 01:36, 11 June 2021 (UTC)

Ecological Term

I'm trying to find the term for when a community of species has evolved together in one place. It is mostly used in the context of range shifts — Preceding unsigned comment added by 2607:FEA8:FEC0:7B38:201F:EFBC:264F:76ED (talk) 17:08, 7 June 2021 (UTC)

The article on Coevolution talks about Mosaic coevolution. Is that the term you want? If not, those articles may suggest other words. Mike Turnbull (talk) 17:15, 7 June 2021 (UTC)

Alabama A&M notable graduate

Why is Dr. Hadiyah-Nicole Green not listed as a notable graduate of the university in the area of science even through wikipedia has her bio listed? == 2600:1700:E5E1:76F0:2967:6101:8EA2:938A

Maybe because you haven't added it yet? ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:37, 7 June 2021 (UTC)

Evolution and the wheel?

Why didn't the evolution of animals produce something like the wheel?--178.7.180.108 (talk) 21:47, 7 June 2021 (UTC)

You'd have to ask God that question. But ask yourself this: How good are wheeled vehicles at climbing rocks and trees, compared with how good arms and legs are? ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:49, 7 June 2021 (UTC)

Probably for a similar reason to why our heads eventually cannot keep swiveling in the same direction. Wheels need the ability to continually rotate, but on a large tissue scale, the need for connectivity for nutrient flow and nerve signaling limits the ability to rotate continuously. --OuroborosCobra (talk) 22:14, 7 June 2021 (UTC)

I'm fairly certain this question has come up before, possibly multiple times. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:27, 7 June 2021 (UTC)

Cecil Adams covers the topic nicely here : The Straight Dope : Why has no animal species ever evolved wheels?

ApLundell (talk) 22:44, 7 June 2021 (UTC)

I don't think any animals have invented something and continued to teach how to invent that something. That generally needs language. And I don't think any animals have a language. 67.165.185.178 (talk) 01:03, 8 June 2021 (UTC).

That's not entirely true. Regardless, the OP was asking about evolution, not invention. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:56, 8 June 2021 (UTC)

Yes, invention through evolution. 67.165.185.178 (talk) 02:37, 8 June 2021 (UTC).

Meaning what? ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:52, 8 June 2021 (UTC)

Things learned through instinct vs. things that aren't. For example, have humans ever brought some sticks and taught monkeys how to make a fire? Then the monkeys can teach other monkeys, and their kids, and decades later, the grandkids know how to make fires? Probably not. I do know kittens are quick to learn things from observing their mother for man-made things that they don't as quickly learn from observing other cats, such as a man-made sliding cat-door. 67.165.185.178 (talk) 04:56, 8 June 2021 (UTC).

The OP asked about evolution. Evolution is a natural process. Invention is an artificial process. ←Baseball Bugs ^{What's up, Doc?} carrots→ 10:00, 8 June 2021 (UTC)

Yes, and I made the claim there are no examples. 67.165.185.178 (talk) 13:31, 8 June 2021 (UTC).

The OP did not use the word "invent." Please do not troll the OP for a word they did not even use. --OuroborosCobra (talk) 12:01, 8 June 2021 (UTC)

Would the word produced, have been more coherent? 67.165.185.178 (talk) 13:31, 8 June 2021 (UTC).

If I'm reading this [1] correctly, 67.165.185.178 may be a sock of a banned user. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:51, 8 June 2021 (UTC)

Not anymore. They were under a 1-year WP:PBLOCK (issued to a different IP address) that expired on May 25, 2021. As the block expired on that date, they are free to participate productively, so long as they don't re-start the same behavior that got them blocked the first time. See here. --Jayron32 16:01, 8 June 2021 (UTC)

To be clear, I though the question was about animal's evolution via intelligence (like brain evolution) to invent the wheel, not having hands and feet as wheels. If animals had hands/feet as wheels, how would that mechanism work, it would need the ability to spin. 67.165.185.178 (talk) 16:15, 8 June 2021 (UTC).

Nothing in the question suggested or implied any sort of intelligence behind evolution. Please do not antagonize the OP for something they never said. --OuroborosCobra (talk) 18:37, 8 June 2021 (UTC)

The IP is flirting with the same kind of cyclic arguing that got him banned a year ago. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:23, 8 June 2021 (UTC)

I think it is generally agreed (at least, among scientists) that there is some sort of evolution behind intelligence; more precisely, that human intelligence is the result of an evolutionary process – not because the path is understood, but because that is the only reasonable working hypothesis. It seems to me that the IP is not assuming more than that, and merely reduced the question (having misunderstood it) to the interesting question, "why is Homo sapiens the only branch on the tree of life that has developed the kind of intelligence needed to invent the wheel?". I see no sign of cyclic reasoning, only some signs of repetitive defensive clarification.  --Lambiam 09:21, 10 June 2021 (UTC)

Yeah, neither part of that is true. See tool use by animals and animal language. --Khajidha (talk) 11:45, 8 June 2021 (UTC)

The main problem with the wheel is that it would require an axle and a bearing. A ball is much better, which is why we have hedgehogs, woodlice, and sea urchins.--Shantavira|^{feed me} 06:58, 8 June 2021 (UTC)

And BB-8. Gråbergs Gråa Sång (talk) 07:56, 8 June 2021 (UTC)

See also Rotating locomotion in living systems, and M. C. Escher's Pedalternorotandomovens centroculatus articulosus, which I think deserves a seat in the Pholidota order.  --Lambiam 09:00, 8 June 2021 (UTC)

Rotifer? DB1729 (talk) 13:54, 8 June 2021 (UTC)

No, rotifers don't rotate, despite their name. however, flagellum do allow rotation, at up to 17,000 rpm, apparently. So that answers the original question, although the structure isn't a wheel but more like an axle plus bearing. It is actually quite widespread, being found in bacteria including the familiar E. Coli. Mike Turnbull (talk) 17:29, 8 June 2021 (UTC)

Yikes, grammar peeve. "Flagellum" is singular; the plural is "flagella". --Trovatore (talk) 17:33, 8 June 2021 (UTC)

Punishable by flagellation. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:05, 8 June 2021 (UTC)

@Trovatore: Should the following be corrected/clarified? In the bdelloids, this plan is further modified, with the upper band splitting into two rotating wheels, raised up on a pedestal projecting from the upper surface of the head. — from the section Rotifer#Anatomy. DB1729 (talk) 18:11, 8 June 2021 (UTC)

@Michael D. Turnbull: ooops, pinged the wrong person. DB1729 (talk) 18:16, 8 June 2021 (UTC)

References

@DB1729: Yes, perhaps into two rotating wheels, should be "into two discs". If I were more confident in my biology or had access to the reference, I'd make that change. I do know that flagella is the plural of flagellum: my only excuse for using the singular is that I just used a direct link to the article name. Mike Turnbull (talk) 10:17, 9 June 2021 (UTC)

Ah. As it happens, flagella exists and is a redirect to flagellum, and there's nothing wrong with just using a redirect directly. This is often the case for such plurals. However, if it didn't exist, you could always write [[flagellum|flagella]], or else create the redirect yourself — I usually do the latter. --Trovatore (talk) 03:15, 10 June 2021 (UTC)