Wikipedia:Reference desk/Archives/Science/2014 October 1

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October 1

Spacecraft Thermal Blankets

Voyager spacecraft diagram

Voyager spacecraft

This first illustration says: "Shown Without Thermal Blankets".

I guess the thermal blankets are the black things in the second picture.

You can see the optical equipments and the spacecraft's body panels are covered by some black fabrics.

The Voyager's 3.7 meter antenna must point to the Earth all the time to keep the connection alive.

Since it is far away from Earth, the sun must be roughly in the same direction.

Except for the antenna disc and some extended parts, almost everything else is in the antenna's shadow.

This means nearly the whole spacecraft is not lit by the sun, not to mention the spacecraft is very distant from the sun most of the time.

Then why did they put thermal blankets on it? Did they use it to dissipate the heat generated by the radioisotope thermoelectric generators and all these electric-powered equipments?-- Toytoy (talk) 03:13, 1 October 2014 (UTC)

Protects it from cold, I do believe. --jpgordon^{::==( o )} 04:57, 1 October 2014 (UTC)

See multi-layer insulation. DMacks (talk) 06:00, 1 October 2014 (UTC)

Then what is the actual color of the Voyager's MLI? Golden? -- Toytoy (talk) 04:55, 2 October 2014 (UTC)

According to this, "the thermal blankets are multi-layer insulation with several layers of meteoroid protection material and external surfaces which have a black conductive coating to prevent electrostatic charge buildup." --jpgordon^{::==( o )} 15:30, 2 October 2014 (UTC)

Photochromism

Are there any photochromic materials that can slowly change colour under the regular indoor lighting?85.141.225.141 (talk) 07:05, 1 October 2014 (UTC)

Silver nitrate is probably an option, but see the article for details and handling instructions. Matt Deres (talk) 13:26, 1 October 2014 (UTC)

Cigarette Filters

People that roll their own cigarettes often use a Cigarette filter; if someone cannot obtain more of these, how many times could they reuse the same filter in multiple rollies? 81.101.142.79 (talk) 15:15, 1 October 2014 (UTC)

I've done this once, it tastes horrible. After a few uses it starts to clog with tar. The clogging will be different with different tar-level cigarettes, and depending on how the person smokes and how much of a horrible taste they can endure. Zzubnik (talk) 15:50, 1 October 2014 (UTC)

In this situation, I usually use a Roach - although it doesn't act as a filter, it keeps the tobacco out of your teeth very effectively. Tevildo (talk) 16:30, 1 October 2014 (UTC)

As a former smoker, I can attest to there being nothing desirable about reusing a cigarette filter (either integrated in commercial cigarettes, or in hand rolled cigarettes). In smoking culture you may hear the term "halfsies" on occasion. This refers simply to cigarettes that have been put out after not being smoked entirely. I have even known people to relight unfinished cigarettes on more than one occasion. However the effect is one of diminishing return. As User: Zzubnik points out, these filters clog with each use and produce truly terrible tasting cigarettes.
An article explaining filters in general can be found here: http://science.howstuffworks.com/innovation/science-questions/question650.htm
As well as an article describing several different makes on filters here: http://www.nytimes.com/2012/07/08/magazine/who-made-that-cigarette-filter.html?_r=0
And finally, supposed "reusable" filters have a market in the industry as well: http://www.targard.com/cigarette-filters (although I've never actually used these to comment either way)
Jwo235 (talk) 16:54, 1 October 2014 (UTC)

Doesn't Pertain To Question Phoenixia1177 (talk) 09:54, 2 October 2014 (UTC)
The following discussion has been closed. Please do not modify it.
No matter how fresh or stale a cigarette may be, the smoke is still noxious to innocent bystanders. ←Baseball Bugs What's up, Doc? carrots→ 17:39, 1 October 2014 (UTC) Thankyou for your input but the question does not pertain to bystanders.81.101.142.79 (talk) 18:36, 1 October 2014 (UTC) The point being, can you explain how anything so noxious can "taste good" under any circumstances? I'd like to know. ←Baseball Bugs What's up, Doc? carrots→ 19:10, 1 October 2014 (UTC) Man, if you have to ask the question... DuncanHill (talk) 19:14, 1 October 2014 (UTC) So it must be one of those "blue sky" things. ←Baseball Bugs What's up, Doc? carrots→ 19:23, 1 October 2014 (UTC) "If you can't understand it without an explanation, you can't understand it with an explanation." [1]. The same could be said for many so-called acquired tastes. SemanticMantis (talk) 20:44, 1 October 2014 (UTC) Addiction doesn't require the drug to "taste good". Stabbing oneself with a needle, for example, is obviously never going to be attractive in isolation. HiLo48 (talk) 23:06, 1 October 2014 (UTC) I like lutefisk, and many don't, but I at least can explain why. And although no one has directly answered my question about "taste", I'm getting some insights here. But before cigarette ads were banned from TV, "taste" was a frequent topic. "Winston Tastes good like a cigarette should." "It should be as a cigarette should." "What do you want, good grammar or good taste?" For example. ←Baseball Bugs What's up, Doc? carrots→ 03:46, 2 October 2014 (UTC) Why do you like lutefisk? Please do be specific. I don't smoke now. I haven't for nearly 10 years. When I did, certain brands tasted better than others. American cigarettes didn't taste stale like the ones I bought in Mexico. If you have no clue what you're talking about, why derail the topic? --Onorem (talk) 03:52, 2 October 2014 (UTC) But fags do taste good. DuncanHill (talk) 23:25, 1 October 2014 (UTC) Not to everyone, especially passive smokers in a country where smoking has become quite rare in many circles. HiLo48 (talk) 23:31, 1 October 2014 (UTC) Or in places where that means the other thing (unless you're into that). I've smoked since I was twelve, and never really cared for the taste, exactly. Isn't terrible, but nothing special, even with the store brands. The draw for me (no pun intended) is another "refreshing" sensation I get in my trachea, and a mild head buzz. That feeling's a bit stronger with a relight that's been sitting for at least ten minutes. I think it has to do with tar caught in the tobacco, not the nominal filter. InedibleHulk (talk) 23:46, 1 October 2014 (UTC) The smell of tomatoes makes me nauseous, and eating them makes me ill. So I don't eat them and I don't get too close to people preparing them. The OP asked a perfectly proper question, he didn't ask for the same tired old holier-than-thou crap from anyone. You don't like the taste or the smell of tobacco smoke? The don't smoke tobacco, and don't hang around people who are smoking. It's a big old world. DuncanHill (talk) 23:45, 1 October 2014 (UTC) The difference is, you can usually tell when someone's about to slice a tomato, and you can give them a wide berth. It can be harder to give a wide berth to some idiot who lights up a couple of feet away and there's no time or place to escape. Or the ones who aren't allowed to smoke in the store they work in, so they stand just outside the door, purposely and spitefully polluting the air for everyone who's coming and going. Don't give me that tired old "tired old holier than thou" holier than thou argument. I don't care if someone smokes. I just want to be about a football field's length away from them if possible. Which can be hard to do if you really, really need to go to that store. Why should I be forced to wait an hour for the smoke to clear? And why should I be subjected to the cloud of smoke still surrounding that smoker after he's returned to his job as store clerk? ←Baseball Bugs What's up, Doc? carrots→ 03:34, 2 October 2014 (UTC) Oh, and not to trivialize your issues with tomatoes. They can be highly acidic (especially the red ones, as opposed to the yellow ones) and some folks are seriously allergic to them. But, again, you can avoid them without being terribly inconvenienced. Not so easy with smokers. ←Baseball Bugs What's up, Doc? carrots→ 03:37, 2 October 2014 (UTC) You'd both hate Tomacco. InedibleHulk (talk) 02:50, 2 October 2014 (UTC)

Instant and Land cameras

What is the difference between an instant camera and a Land camera?85.141.225.141 (talk) 17:14, 1 October 2014 (UTC)

Land cameras were a specific brand of instant camera that were sold in the middle part of the last century. Nimur (talk) 17:20, 1 October 2014 (UTC)

Named after inventor Edwin H. Land.  —71.20.250.51 (talk) 17:32, 1 October 2014 (UTC)

And here I thought they weren't to be used while SCUBA diving. :-) StuRat (talk) 21:36, 1 October 2014 (UTC)

For that you'd need a Leica C.  —71.20.250.51 (talk) 22:15, 1 October 2014 (UTC)

According to yourdictionary.com <http://www.yourdictionary.com/polaroid-land-camera> a land camera is a Polaroid camera. It is “a transparent material containing embedded crystals capable of polarizing light: used in optics, photography etc.” It says Polaroid is short for Polaroid Land Camera. The definition of an instant camera <via http://dictionary.reference.com/browse/instant+camera> is “a usually portable camera that produces a finished picture shortly after each exposure. They are one in the same. They are sometimes called Land cameras because they were developed by Edwin H. Land and have been marketed since 1948 <http://dictionary.reference.com/browse/polaroid>. JERE225 (talk) 01:55, 4 October 2014 (UTC)

Land cameras are what you would typically what you think of when you see an instant-developing film camera, such as a Polaroid. As noted here, the original name for the Polaroid was the Polaroid Land Camera. From what I understand of Instant Cameras, are the same thing of another name, as noted here. Many of the cameras listed on the Instant Camera page have the title of Land Camera attached to them. Most instant cameras seem to be more modern, such as the ones found here by Polaroid. Land cameras seem to be their initial name, and Instant was adopted later. Cyyris (talk) 02:39, 4 October 2014 (UTC)

Jasmine tea

Does jasmine tea have the same fat separating properties as oolong and puer? 82.132.230.244 (talk) 19:12, 1 October 2014 (UTC)

I take it you are asking about supposed benefits of these teas as an aid to weight loss? There are claims on the web that oolong tea blocks fat absorption but these are entirely unsupported by any scientific evidence. However, there is one scientific study I found about the weight loss benefits of oolong tea here which concludes: "It is clear that consumption of oolong tea stimulates both energy expenditure and fat oxidation in normal weight men. This raises the possibility that tea consumption could have some beneficial effect on an individual’s ability to maintain a lower body fat content. However, any beneficial effect would only be realized if the effect was sustained upon chronic consumption of tea and the individual did not compensate with greater food intake in response to tea consumption". I don't know if there are similar studies using other teas. Richerman (talk) 22:33, 1 October 2014 (UTC)

There is also information about the health benefits of teas here. Richerman (talk) 22:42, 1 October 2014 (UTC)

I didn't find any sources that directly linked jasmine tea to weight loss, but I found an article that sited a study on rats that were fed jasmine and were noted to have lowered cholesterol and improved circulation. Another study showed that jasmine lowered cholesterol in hamsters <http://green.healthfoodxdrinks.com/health-benefits-jasmine-tea/>. I found another source that concurs with the above post <http://www.teasetc.com/tea/article.asp?ID=1>.22:06, 4 October 2014 (UTC) — Preceding unsigned comment added by Acwatts1 (talk • contribs)

sorry, I left out a source from sentence 1 <https://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Science#Jasmine_tea>Acwatts1 (talk) 22:23, 4 October 2014 (UTC)acwatts1

Triangulation accuracy via GPS versus WiFi

Is there any reason to think that triangulation of the location of a phone within a building (e.g. under a cushion) would be more accurate using WiFi than GPS? --78.148.106.72 (talk) 20:08, 1 October 2014 (UTC)

For most phones I'm aware of, it becomes a comparison of using GPS information only, compared to using GPS and WiFi. Google and Apple both have databases of locations of wifi hotspots that they use to increase location accuracy. See Hybrid_positioning_system and Assisted_GPS. I also found this very similar question being asked on Stackexchange: [2]. So, I think it is fair to say a phone will have better location accuracy if wifi is turned on, compared to if wifi is turned off. If you manage to turn off everything except wifi, and compare that to turning everything off except GPS, then the issue becomes more complicated. But I don't think that's the common use case. SemanticMantis (talk) 20:40, 1 October 2014 (UTC)

Since the source of the signal is much closer with WiFi, it should be more accurate (if we assume the error is a percentage of the distance from the sources). StuRat (talk) 21:33, 1 October 2014 (UTC)

.. unless, of course, your possible wi-fi locations are miles apart and not registered in any databases, and your 2-G phone signal transmitter covers many miles . My phone doesn't know where it is if I turn GPS off. In the centre of a city, where GPS reception is poor, I agree with the analyses above, especially in a building under a cushion where a GPS signal is often not available. Dbfirs 08:01, 2 October 2014 (UTC)

Predicting and preventing seasickness

Two questions, closely related:

On a ship, is it possible to guess how many people will get seriously sick from the motion of the ship? The formula would probably also include ages, genders, days at sea already, etc. I'm asking because I noticed on a cruiseship that even during medium swell the dining room was half empty. Shipping companies (hopefully) must have a way to predict how much food would go to waste if they prepared it as if the ship was in a harbour.

Second question: Why are the no simple swings on a cruiseships, with a serious amount of balast? Instead of burdening the vestibular system with movements in every different direction, it should (I guess) feel as being in an elevator with only up and downward accelerations. A luxury version would be an elevator on a swing which would undo that movement as well. I've seen people who'd pay a lot more for that than a special treatment in the spa :)

Joepnl (talk) 21:50, 1 October 2014 (UTC)

There are physiological models to predict seasickness and there are survey methods, neither of which are prefect. I don't doubt that cruise ship companies tabulate sea conditions, sickbay and dining room numbers to develop empirical statistical models and predict food preparation and medical staff needed. --Mark viking (talk) 22:13, 1 October 2014 (UTC)

When it comes to spelling, nobody is prefect. :-) StuRat (talk) 17:00, 3 October 2014 (UTC)

From your first, very interesting, link: "A historically common index of motion sickness severity is the Motion Sickness Incidence (MSI), which is the percentage of people who vomit when exposed to a nauseogenic environment." Cool metric :) Joepnl (talk) 22:38, 1 October 2014 (UTC)

A friend was forced to cross Port Phillip Heads on a ferry as part of an event in which we were both participating. He was so frightened of becoming seasick that he showed major symptoms long before we actually boarded the ferry. I'd love to see the metric that factored that in. (Although my friend is, admittedly, unlikely to ever take a cruise.) HiLo48 (talk) 23:39, 1 October 2014 (UTC)

Some points:

1) I recall seeing a ship fitted with a table set up like that, with the idea being to keep food from spilling as the ship rolls. However, the seats were just attached to the boat, meaning the food sitting on the table was moving relative to those trying to eat it. So, it was of limited value.

2) The more of the ship was set up like this, the more motion the rest of the ship would need to undergo to compensate.

3) Nausea also has a significant visual component. One bit of advice is often to concentrate on a far away point which isn't moving much. Blindfolds aren't particularly helpful, though, as seeing a wave approaching and bracing for the motion seems more helpful than having that motion hit an unprepared person.

4) There are meds that help with seasickness. Hopefully, if they are only taken for the duration of the trip, the side effects will be minimal.

5) Larger ships, with a lower center of gravity, seem to roll less, and at a lower frequency. Unfortunately, the modern trend in cruise ships is to build them with a higher and higher center of gravity. This not only causes more roll, it also makes capsizing more likely. The ability of cruise ships to register is whatever country will let them get away with unsafe practices is the problem here. If a uniform set of standards could be agreed to by all nations, that might work, but of course small nations that get a substantial amount of money from cruise ships registering there won't be likely to worry about safety. Unfortunately, this looks like a case of tombstone mentality, to me. This means nothing will be done about it until thousands die on a cruise ship. Then there will be temporary changes, until the public stops paying attention, and the cruise lines go back to business as usual. StuRat (talk) 17:08, 3 October 2014 (UTC)

I'm thinking ginger, but do cruise ships really rock back and forth? Mostly I can't figure out what makes people decide to go on one -- it seems like common sense that the novelty value of a ship is proportional to its area:volume ratio, so the best ones come with oars or a paddle. Wnt (talk) 21:25, 4 October 2014 (UTC)

My thought as well. The larger a vehicle is, be it land, water or air, the less affected it is by wind and waves. In any case, isn't there medication that's supposed to suppress the symptoms of motion sickness? ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:15, 4 October 2014 (UTC)

Fermented fish and meat

A number of sauces are made from fermented fish, and some dishes are made of fermented meat. How is this possible?

I thought that only foods with a lot of sugar or other carbs can be fermented. Aren't fish and meat made of mostly protein and fat? How do they ferment?

I was reading the article Fermentation in food processing, but I don't feel it is explained.--24.228.94.244 (talk) 23:56, 1 October 2014 (UTC)

I think it may be a semantic thing. Easier to serve something made from "fermented" ingredients than rotted ones. Though there is a bit of sugar in meat, it's not near the same as fruit. InedibleHulk (talk) 00:04, 2 October 2014 (UTC)

But there's this at the top of Google. Apparently a fine line between rotting and fermenting. InedibleHulk (talk) 00:05, 2 October 2014 (UTC)

Fermentation of a protein would be Hydrolysis, which includes breaking up the protein into amino acids and peptides. Individual amino acids taste pretty good (MSG). Ariel. (talk) 02:03, 2 October 2014 (UTC)

Fermentation strictly is the processing of sugars, but more broadly refers to any action of microscopic cultures on food (especially as people who deal with food are not always strictly aware of the subtle differences in the chemistry involved. Wikipedia does have an article on Fermented fish for example. The difference between rotten and fermented is fuzzy, but amounts to "does this make me sick when I eat it?" versus "does this taste good to me?" We eat LOTS of foods in EVERY culture that is flavored by some process of "controlled rotting". Cheese, bread, wine and beer are all familiar to the Western palette, and all require the action of microorganisms to breakdown a food product. Most people in Western cultures wouldn't think twice about eating a piece of cheese, and yet if we called it "mold-infested milk solids" they may not realize that's exactly what cheese is. The line is often individual and cultural: some people enjoy the flavors of fermented fish and meats, while others find them repulsive, often subjective to the cultural norms of the individual person. --Jayron32 02:17, 2 October 2014 (UTC)

Mmm...mold-infested milk solids on hardened yeast, topped with scraps of charred corpse and doused in a viscuous organic fluid. Hold the anchovies, dude! InedibleHulk (talk) 02:46, 2 October 2014 (UTC)

Also, to expand a bit and more directly answer the OP's question: the product of sugar (and carbohydrate) fermentation is some combination of carbon dioxide, ethyl alcohol, acetic acid, and/or lactic acid: which makes sense as carbohydrates are merely carbon-hydrogen-oxygen compounds, and those products are basically smaller compounds made of the same three elements. The deal with fermentation of proteins is the introduction of nitrogen into the mix. Proteins contain a sizable amount of nitrogen, and the products of protein fermentation can include such tasty treats as ammonia, hydrazine, purines, pyridines, and other fun chemicals, notable ones named things like cadaverine and putrescine. I can attest (having worked with a few of these), and you will find many references out there, that confirm that these chemicals smell like anything from "piss" to "old fish" to "rotten meat". You'll see in the fermented fish article that the tastes of MANY of the dishes so described frequently mention ammonia-like smells and tastes, which confirms the presence of these numerous nitrogenous fermentation products. Strictly speaking, these are all poisonous (but then again, strictly speaking ethanol is poisonous, and we deliberately create that through fermentation and consume it...) but people still do eat, and enjoy, these foods in many cultures. --Jayron32 02:49, 2 October 2014 (UTC)

On the topic that we commonly ingest toxic substances: both onion and garlic contain toxic compounds [3] [4], but many of us still eat them frequently with no ill effects (I can find LD 50 values for pets, but not for humans...) Actually, we eat them in part because they are toxic-- the same compounds that keep the plant storage organs from being eaten by other things also help preserved them in our cellars and give them interesting flavor. So there's another similarity with fermented fish- controlling the conditions and microbial growth actually prevents the 'bad' types of microbes from taking hold, and as a result the fermented product can be stored longer. With these vegetables, as well as fermented fish, we should always remember The_dose_makes_the_poison.' SemanticMantis (talk) 14:23, 2 October 2014 (UTC)

I agree - and would go further: Any living (or once-living) tissue contains an incredible mix of chemical compounds - it would be astounding if none of those were toxic in sufficient quantities. So it's not just onions and garlic. If we wished to avoid all toxic chemicals completely, we'd have to give up on eating all plant and animal-derived foods and pretty much synthesize everything from scratch. But something as synthetic as Soylent contains much that is derived from plant material - and which undoubtedly contains much that would be toxic in sufficient quantities. Even good old Vitamin E is toxic in sufficient quantities - yet we can't do without it. So we're left with a bunch of substances that are toxic in large quantities yet which we must consume in order to stay alive...so dosage is absolutely the most important thing. SteveBaker (talk) 14:01, 3 October 2014 (UTC)

Actually, as our article on spices mentions, spices were chosen not just to preserve themselves but as preservatives to add to other foods. Wnt (talk) 16:16, 4 October 2014 (UTC)