Wikipedia:Reference desk/Archives/Science/2018 July 20

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July 20

Photon as "information"

Sometimes I hear photons described or used synonymously with "information". Can anyone help me understand or point me to resources that explain this comparison?

As an example, in a youtube video on the Black_hole_information_paradox, at around 3:45, the speaker states that, "The black hole radiates particles, mostly photons - that contain no information. Eventually the black hole must completely evaporate into those particles leaving no clue as to what fell into it in the first place."

I understand the evaporation and paradox aspects of what is being said, but am unclear how "information" and "photon" relate. — Preceding unsigned comment added by 128.229.4.2 (talk) 14:56, 20 July 2018 (UTC)

A photon is not information; a photon can be used to carry information, if and only if some property of the photon can be controlled - like when it gets emitted, or what its frequency is, and so on. Formally, that would mean that we can express this "controllable" property using a causal relationship to some other property; then, if we took a measurement of the output property, it would have carried information about the causative property that we did not directly measure.

In the case of an engineered system like fiber-optic communication, individual photons don't actually carry the information: instead, information is encoded into the rate of arrival of groups of photons, treated as an ensemble. The arrival of any one specific individual photon is called shot noise. The arrival of a whole lot of photons within a specific interval, per the engineered specification of the system, carries information.

There is a fun mathematical conundrum of quantum mechanics here - how can one single event be noise, but if we put two otherwise identical events together, they constitute a non-noise signal? This is the property of coherence. In real engineered systems, we use more than two photons so that we can build reliable machinery; but in the realm of theoretical physics or in the study of natural systems, we might investigate the behavior of this single-particle information-carrying behavior using the mathematical and analytical tools of thermodynamics; and we might construct testable hypotheses using the methods of experimental physics; and then we might use those tools to draw conclusions that apply to the more difficult realm of black hole thermodynamics.

Ultimately, when you hear a pop-science publication talking about why black holes do (or do not) emit "information," they are using loose terminology to describe the incoherent emission of radiated energy. Whether those statements are accurate, or valid, depends on the quality and currency of the documentary you're watching!

Nimur (talk) 17:10, 20 July 2018 (UTC)

There is something out there about the concept of physicality of information. I haven't found a layman explanation of it (I tried googling). Apparently somehow information is as "real" and permanent as particles of matter? There are Conservation laws but that article does not contain the word "information". Black hole information paradox kind of hints at it but seems to lack an explanation why it is a paradox. Any help on this for us non-quantum-theorists? Or am I chasing a red herring, in which case can you explain why the black hole information paradox is a paradox? 85.76.73.51 (talk) 17:28, 20 July 2018 (UTC)

The "paradox" is a way to express a disagreement about whether a property's measured state is statistically certain, or absolutely certain. Some physicists believed these words described distinct concepts; and certain specific mathematical models of the black hole provided an example where we could differentiate between the two conditions. As of the time of this writing, the consensus seems to be − there is not any paradox, because there is no actual way to distinguish these two conditions apart. (One of the very last peer-reviewed publications by Stephen Hawking was Information loss in black holes, (2005), in Physical Review - if you can read and understand that paper, you can understand the paradox and Prof. Hawking's position regarding its resolution... and if you can't read and understand that paper... well... you're one of many).

I mean, it's a little bit of a disservice that this "paradox" has been brought to the forefront of the popular conception of modern physics. It's a minor debate about the minutia of the problem. To really understand it, you've got to invest a lot of up-front intellectual effort. And if you actually do that, you'll find many more interesting things to spend your intellectual efforts on! Nimur (talk) 17:41, 20 July 2018 (UTC)

Oh, I don't know Nimur, I find the epistemological questions here, including those involved with that particular question, endlessly fascinating. Anyway, here are the two most accessible/least technical sources I was able to find on the matter for the OP, one of which takes it's title and general thrust from exactly the question the OP has posited in their inquiry: Physical_information, [1]. There's a bevy of additional information out there, though, if you know the right search terms, so if these fail to address your questions, OP, let me know. Snow ^{let's rap} 06:08, 21 July 2018 (UTC)

Thanks Snow, the link to Physical_information was definitely helpful. 128.229.4.2 (talk) 14:29, 23 July 2018 (UTC)

Happy to be of assistance. :) Snow ^{let's rap} 18:32, 23 July 2018 (UTC)

That photons are not information, but carry information is a helpful clarification Nimur. Thank you.

I also came across another video that says "Light not only interacts with matter, it is also altered by it, and can be used to gather information about the world around it, with almost no delay...". This helps me understand. 128.229.4.2 (talk) 19:05, 20 July 2018 (UTC)

There has been quite a bit by Leonard Susskind equating quantum entanglement with wormholes. I am not fit to really recommend the best of it, but there may be a way to get at physicality of information that way (I don't know). Wnt (talk) 21:28, 21 July 2018 (UTC)

Balance and vision

Does the human brain use vision to establish balance? Does a blind or short sighted person have worse balance? Would closing your eyes make you have worse balance? Clover345 (talk) 19:08, 20 July 2018 (UTC)

Yes, vision plays a role. In most people, the semicircular canals are the most important factor, and vision only plays a minor assistive role, along with proprioception. However, people whose semicircular canals are non-functional (this happens in a substantial fraction of deaf people) may have to rely entirely on vision to balance. See our Balance disorder article for more information. Looie496 (talk) 20:02, 20 July 2018 (UTC)

A standard clinical test for vestibular function is to ask someone to stand, then ask them to close their eyes. The loss of visual information, in addition to a loss of vestibular cues, leads to them losing their balance. It needs to be done with someone available to support them as they sway. Klbrain (talk) 22:48, 22 July 2018 (UTC)

How germs get inside the body

I'm using "germs" as a collective term for viruses, parasites, fungi, and bacteria. They can all be called "microorganisms", but that name is a mouthful. So, I'm sticking with "germs" and "bugs". I am aware of the ways that germs get inside the body - by vapor, by food and water, by broken skin, and by intimate touching. What makes the inner lining of sexual body parts so defenseless against pathogens that some pathogens ONLY use this route to climb onto another individual? Perhaps, the vaginal walls, unlike skin, don't have layers and layers of protection. So, germs can easily pass through the cells or infect the cells. Take HIV, for example. There seems to be no reported cases of HIV being able to infect a person through contaminated food. So, HIV cannot survive in food or in the water supply or pollute the air. It can only spread by bodily fluids - using contaminated needles, breastfeeding, and having sexual intercourse. Also, unlike the digestive system, the vagina is not acidic enough to burn the bugs. And some bugs don't travel through air, because they can't. They can only travel by close contact, and sexual intercourse is a super-close contact. The man and woman during coitus are not next to each other. The man's penis is placed into the woman's vagina, and if sperm can travel up to the uterus, then so can bugs and germs, can it? That is literally inside an organ. This question is not about how a bug infects a cell, but how a bug - especially a bug that primarily relies on super-close contact - gets inside the body. SSS (talk) 19:11, 20 July 2018 (UTC)

Mucosa is a useful term here. Very few infectious organisms make it through unbroken skin. The usual routes are inhalation, cuts, the digestive tract (not all of them, as it's a permeable but hostile route) and also (as you copiously mention) sex. There's also an issue of transmission from an infected person - some diseases are hard to catch from someone, because they're not releasing it except by bodily fluids, and then some diseases (such as haemorrhagic fevers) are far more easily transmissible because they produce fluids, or more of them, than are normally present. Ebola is a sexually transmitted disease, but then so's everything. However STDs are those which are only transmissible (in significant numbers) by sex. Andy Dingley (talk) 21:09, 20 July 2018 (UTC)

A key concept here is cornification. Cornification leaves external skin covered by multiple layers of dead cells which are uninfectable and present a physical barrier over the cells that could be infected. Many internal surfaces also have stratified squamous epithelium, but it is not cornified, needs to be kept moist, and doesn't have the same degree of resistance. This is why "mucous membranes" are a target for colds and worse. Now "mucosal immunology" gets much more complicate than this - this paper is about HIV-infected T cells outside the body wandering around epithelium somehow sniffing for the epithelial cells right right over stromal macrophages - these T cells form an "immunological synapse" that delivers the virus to be transcytosed through the epithelial cell into the macrophage to infect it. This is obviously some very specific biology being hacked by the virus; it is almost like a single cell's version of an STD! Wnt (talk) 21:12, 20 July 2018 (UTC)

Upside down glasses

I'm looking for the article about the glasses/experiment where they put those on people to make the whole world upside down. First, they fell about. Then, after a day or so, they got used to it. Then, when they took them off, they fell about again. Do we have coverage of that at Wikipedia? Anna Frodesiak (talk) 20:08, 20 July 2018 (UTC)

See George M. Stratton. Mikenorton (talk) 20:11, 20 July 2018 (UTC)

Thank you, Mikenorton. I think we need a bunch of redirects to it. Anna Frodesiak (talk) 20:14, 20 July 2018 (UTC)

Actually, I just found Neural adaptation#History with similar content. What should be done? Anna Frodesiak (talk) 20:15, 20 July 2018 (UTC)

That image of a "Modern version of inverting mirrors with harness" sure doesn't look very up to date to me. Martinevans123 (talk) 20:47, 20 July 2018 (UTC)

Looks like a skateboard helmet and medical tape. Anna Frodesiak (talk) 20:49, 20 July 2018 (UTC)

Yes, after a trip to A&E on a bad night? Probably even more effective than beer goggles. Martinevans123 (talk) 21:12, 20 July 2018 (UTC)

As a start I've changed "Perceptual adaptation" in the "see also" section of the Stratton article to "Neural adaptation" so at least there is a clear link between the articles. Apart from that, I'm not sure what should be changed as the content is not identical. Mikenorton (talk) 20:31, 20 July 2018 (UTC)

Sounds good. What about redirects? I think these glasses have a different names. Search engines say reversing goggles, prism glasses, and we could make up a couple that we guess visitors would type into the search box, like upside down glasses. Target? Anna Frodesiak (talk) 20:40, 20 July 2018 (UTC)

I can find inverting glasses, inverting spectacles, inversion goggles, inverted vision glasses and upside down glasses as well, so lots of options. As to the target, currently the section in the Stratton article looks like the best bet. Mikenorton (talk) 21:03, 20 July 2018 (UTC)

Okay, created several redirects based on what you wrote above, example here. Many thanks, Mikenorton. Anna Frodesiak (talk) 02:32, 21 July 2018 (UTC)

Rubbing alcohol

If you sterilize your hands with it, can it go into your body and make you dead? Anna Frodesiak (talk) 20:41, 20 July 2018 (UTC)

Rubbing alcohol is typically used for disinfection on skin. SSS (talk) 20:50, 20 July 2018 (UTC)

(edit conflict) WP:NOMEDICAL and all, but that sounds highly unlikely given that it's a common ingredient in many hand sanitizers and our article on it notes that it's "used primarily as a topical antiseptic". Drinking it would be a very bad idea, though. Ian.thomson (talk) 20:52, 20 July 2018 (UTC)

Thank you. That's what I thought. Anna Frodesiak (talk) 20:56, 20 July 2018 (UTC)

(EC) Our article states "Poisoning can occur from ingestion, inhalation, absorption, or consumption of rubbing alcohol", so assuming that you're not intending to drink it and you're not going to eat something with your hands still covered in it, the main thing is probably to use it in a well ventilated area - for absorption, short exposure should be fine " Dermal exposure to the liquid and vapour. There is little absorption through intact skin, but significant delayed absorption over 4 hours postulated (Martinez, 1986). Note risk of inhalation after prolonged skin exposure (sponging, etc.)" from here. Mikenorton (talk) 20:58, 20 July 2018 (UTC)

• Yes. But it's no big deal. We can metabolise a lot of alcohol, no problem. I use a lot of them in my workshop and I'm getting fussier as to which. Alcohols are OK, acetone is OK, I've replaced my hexane with heptane because of the hepatotoxicity risks, and I avoid benzene or carbon disulphide or chlorinated solvents.

I use a lot of methylated spirits, such that I've nearly run out and I'm facing a hard task to replace it. The "standard" stuff is bright purple, stinks of pyridine and is mostly cheap methanol with some ethanol in it. Don't drink it - methanol is bad for you (standard antidote is vodka, as a clean source of ethanol). But if you're a summer woodworker, you really want to avoid both the purple dye and the stench. It's very hard to buy the industrial grade without them though.

If you work in healthcare, the the vast use of alcohol hand sanitisers these days is a problem. They degrease the skin, and skin oils are an emollient to soften the skin and stop it cracking, also to make the skin less permeable. So degreased, cracked, heavily sanitised skin becomes more of a risk for infection. If you're doing this twice every half hour, then it's also important to moisturise. Andy Dingley (talk) 21:20, 20 July 2018 (UTC)

I also highly recommend against gargling with it. It burns much worse than 80 proof ethanol. Sagittarian Milky Way (talk) 23:47, 20 July 2018 (UTC)

Thank you all! Anna Frodesiak (talk) 01:35, 21 July 2018 (UTC)

Andy, is there anything you do not know? :) You must be very handy about the house. So, are you saying hospitals have no use for good ol' rubbing alcohol without the extras? When they give you an injection, what do they use on the little cotton ball? Anna Frodesiak (talk) 01:35, 21 July 2018 (UTC)

There's a difference between what you rub on the patient (once or twice) and what you rub on the staff (fifty times a day). As we've increased the sanitisation of staff so much in recent years, we're now seeing chronic issues that were unexpected - such as the skin degreasing effect. Andy Dingley (talk) 08:53, 21 July 2018 (UTC)

Ah, okay. And yes, →we've gone overboard with this germ killing thing. A bit of Cussons Imperial Leather is fine with me. And nobody gets food poisoning here much. I guess we all get a bit of this and that, so we're immune. I know geckos run on our clean dishes before use. We never got sick. Anna Frodesiak (talk) 08:57, 21 July 2018 (UTC)

There aren't many reptilian diseases which are transmissible to humans. Mice would be quite another matter. Flies are a problem, not because we catch fly diseases, but because of their unclean habits with other human waste. Andy Dingley (talk) 19:07, 21 July 2018 (UTC)

Hi Andy. That's good to hear because Haikou has no mice and very few flies. Anna Frodesiak (talk) 20:21, 21 July 2018 (UTC)

I'm going to call a major on the claim "we've gone overboard with this germ killing thing" in response to the topic of discussion namely hand sanitisation in healthcare settings and especially hospitals. (To be clear, I'm not saying Andy Dingley was making that claim, it seems to originate from Anna Frodesiak.)

It's well recognised that Hospital-acquired infections are a major problem worldwide causing many deaths and other negative consequences. With the increasing prevelance of antiobiotic resistance, colonisation [2] is also a major problem in itself even when it doesn't lead to an infection at the time. (Increasing antibiotic resistance is also one reason why just throwing antibiotics at the problem when it occurs, even ignoring that it doesn't always work even without resistance, is clearly not a solution.) </p

By no means do these all come from staff hands but hand hygeine, staff, patient and visitor is generally considered an important factor in reducing infections and colonisations. Our article albeit unsourced says Handwashing frequently is called the single most important measure to reduce the risks of transmitting skin microorganisms from one person to another or from one site to another on the same patient. This says something similar [3]. More generally, there are many studies demonstrating the benefits of good hand hygeine in reducing HAI including I think colonisation.

About the soap vs. hand sanitiser issue, AFAIK the big factors tend to be time and facilities. Proper hand washing generally takes IIRC 45 seconds or so. Drying then adds more time. I'm not sure how much worse improper handwashing performs, although insufficient drying definitely can definitely be a significant problem [4]. While hand sanitiser misuse likely also negatively affects performance, the main requirement tends to be ensuring it covers the entire surface of both hands and rubbing over the hands until dry [5] so is somewhat easier to follow. Also as AD mentioned, for staff, we're talking about something which is often supposed to be performed every 30 minutes or less, and maybe also after every contact with a patient. For visitors and patients, especially those with limited mobility, the number who will or able to visit a sink to wash and dry their hands compared to those who will use the sanitiser at the bed or door is likely to be fairly different.

At least for my local DHB, and also by that CDC ref to some extent, the general recommendation in healthcare settings is if the hands are visibily soiled e.g. with blood, urine, faecal matter to use soap and water, but otherwise hand sanitiser is sufficient. (I think handwashing is recommended after visiting the toilet without checking for visible soiling.) Regular moisturisation is also recommended (well for the DHB recommendations at least at least). However I don't think using soap instead of hand sanitiser is considered wrong provided proper steps are followed. Actually I wouldn't be surprised if it's better if really done as regularly.Although I'm not sure if bar soap is not going to work well in many healthcare settings. (They may be used for surgical hand scrubs although medicated ones seem to be the minimum recommended [6] [7].) Note that as the CDC ref also says, in many settings outside of healthcare, hand sanitisers are only recommended if water and soap are not available.

I'm not sure why you brought up food poisoning. AFAIK it's often only one, and probably a minor one at that, of the risks of infections in healthcare settings. Note that we should not conflate the problems and solutions in healthcare settings with those in other areas. For example, I'm fairly sure many proponents of the hygiene hypothesis and those who think there is excessive use of antiseptics (which includes the CDC and many other healthcare related organisations) and excessive concern about bacterial counts etc especially in homes who will say this has limited relevance to hygiene requirements in most healthcare settings where there is generally a congregation of patients with infections and patients with weaked immune systems. (And even within healthcare settings there are differences, e.g. surgical handscrubs vs normal hand hygeine.)

That said, while I don't know about the specifics of Haikou, I'm fairly sure food-borne illness are a significant problem in a lot of China as they are in pretty much all of the world with significant numbers of humans. If anyone is claiming otherwise, this isn't just a case but an extraordinary claims require extraordinary evidence case IMO since basically no one else has come even close. (So to be clear, this isn't an anti-China thing, it applies to pretty much everywhere.)

This Lancet world report article (which I presume means it's not peer reviewed) [8] mentions how although the number of reported deaths is very low, it's very likely this is in part because of the limitations in the monitoring systems there and mentions some of the challenges etc. The WHO estimates 125 million people falling ill a year in the Western Pacific region [9]. While they list individual countries at least there, my earlier point remains if the claim is made these are nearly all coming from Japan, Philippines, Viet Nam, South Korea, Malaysia etc [10]. (Actually I think you can exclude Japan, it looks like WPR B itself is around 120 million [11], probably also can be derived from [12] or [13].) Admittedly one of the biggest causes of death, liver cancer from aflatoxin, may not fall under the ordinary definition of food poisoning. And that, and parasites another major problem aren't really affected by hand hygeine. And to be clear again, I don't want this to be some sort of pro or anti China bitch fest. This [14] for example shows that China did very well in terms of meeting the target for the "Mortality rate attributed to exposure to unsafe water, sanitation and hygiene".

Nil Einne (talk) 13:56, 22 July 2018 (UTC)

NIST and WTC's dust

Is NIST conducted a research of WTC's dust as part of NIST's investigation of the collapse of WTC 1, 2 and 7? 37.142.4.56 (talk) 21:25, 20 July 2018 (UTC)

Wikipedia has a fairly extensive, well-referenced, and decently written article on this topic at Health effects arising from the September 11 attacks. You can use that as a starting point for your research. --Jayron32 21:29, 20 July 2018 (UTC)

Carcinogens often take several decades to cause cancer so you couldn't know the full effects now or even in 2030. Asbestos use tailed off very long ago and people contracted asbestosis from before then for quite a long time after. It'd be interesting to see if the 2031 cancer getting rate is higher for people who lived in Downtown Manhattan and Brooklyn then similar places like Midtown and Queens. I often looked to see which way the Ground Zero smoke string was pointing and never saw it get very far from the climatological average direction (westerlies). Minutes or hours after the collapses, the visible ash string stretched to the horizon or almost (Ground Zero is only 16 acres remember), it was at least c. 10 miles long for days and took weeks before you could only see smoke from less than 10 kilometers away from a low roof. If you stood on a street pointing to the heart of Ground Zero in mid-December you could still see smoke from smoldering underground fires from at least hundreds of yards away. Sagittarian Milky Way (talk) 23:45, 20 July 2018 (UTC)

So It's a yes or no? 37.142.4.56 (talk) 06:26, 21 July 2018 (UTC)

The objectives of the NIST investigation are listed here and the final reports themselves are linked here. I don't know the answer to your question, but with enough reading you could find it.--Wikimedes (talk) 07:11, 21 July 2018 (UTC)