Wikipedia:Reference desk/Archives/Science/2015 March 8

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March 8

Vinegar and breathalyser 2

Follow up question was hijacked and taken on tangent: what would vinegar do to a breathalyser test result? There is no legal advice being sought. There is a specific chemical process taking place and the question is what would happen if there was significant vinegar consumption 3 big pickles prior to test? Thanks 66.87.80.255 (talk) 02:39, 8 March 2015 (UTC)

It would do nothing. Breathalyzers work by oxidizing ethanol to acetic acid, which is the main ingredient in vinegar. A breathalyzer is basically a pocket galvanic cell that generates a small voltage by a redox reaction. When the ethanol --> acetic acid oxidation causes a reduction of oxygen --> water. Since acetic acid is basically already oxidized ethanol, it can't be further oxidized, and the vinegar on your breath has no effect. --Jayron32 04:57, 8 March 2015 (UTC)

• The question really is how much alcohol is there in vinegar. True diluted acetic acid is generally sold as "imitation vinegar"; the rest is basically spoiled wine or apparently in some cases spoiled beer, etc. There's one site being quoted [1] where the guy claims to have found some paper that found brands of balsamic vinegar with up to 2% alcohol, but I have no idea if that's legit or not; in any case that's an outlier. A lot of it is subjective - when do you open a bottle of wine and say "pee-you, that's vinegar"? The regulatory requirement is vinegar being 4% acetic acid, and to work well for some applications apparently it has to be 5%, which it almost always is; this limits the amount of alcohol present to some degree. Note though that drinking even spoiled wine and failing a breathalyzer might not be a reliable defense! Wnt (talk) 12:59, 8 March 2015 (UTC)

Cosmological distance

When cosmologists are recording distances of certain objects which have been determined are in fact moving away from us due to expansion, can they factor exactly how far the object is at present? If yes, which distance is actually used for the record? Or does it depend on what is being researched?66.87.80.255 (talk) 03:46, 8 March 2015 (UTC)

I don't think so. For one thing, there is no universal "present" time. When they say that it is a certain distance from us, that is based on the light reaching us now. Bubba73 ^{You talkin' to me?} 04:10, 8 March 2015 (UTC)

but one of the few facts we know about that object is that it is not now where we are seeing it. So shouldn't we say we know it's specifically not there for the record?66.87.80.255 (talk) 04:23, 8 March 2015 (UTC)

Bubba73 is wrong—distances reported in the popular press are usually comoving distances, which are distances extrapolated to the current cosmological time, assuming current cosmological models are correct. "Official" distances are normally given as redshifts, since that's what's actually measured. See Distance measures (cosmology). -- BenRG (talk) 04:36, 8 March 2015 (UTC)

Thank you for correcting that. Bubba73 ^{You talkin' to me?} 04:52, 8 March 2015 (UTC)

Most of the time it is most useful to specify where an object appears to be, since that is the information of greatest utility to people with telescopes. We do however have numerous concepts for kinds of astronomical distances. See for example distance measures (cosmology). The main ones are proper distance, comoving distance, and light travel distance. These are related and generally calculable from one another provided basic information is available, though the main examples all tend to deal with the apparent properties of the object. The implied future of the object is generally of less interest. Given velocity and position one can roughly predict where an object X light years away would presumably be X years in its future, but since we can't observe that future or test those predictions (except for very small time durations), such predictions generally aren't of much direct interest. However, astronomers do know very well that what they observe today reflects the universe as it was rather than as it is. Dragons flight (talk) 04:45, 8 March 2015 (UTC)

so is there an instance where the object is moving toward us faster than others or counteracting the expansion where it would be in that same spot "at present"?66.87.80.255 (talk) 05:00, 8 March 2015 (UTC)

The Andromeda Galaxy is moving towards us. --TammyMoet (talk) 09:53, 8 March 2015 (UTC)

what I meant was 2 objects that are the same current distance away that are moving away due to expansion but are moving away at different speeds.66.87.80.255 (talk) 14:12, 8 March 2015 (UTC)

Different speeds compared with what? The speed that other objects are receding? That's the case all over the place. As I recall, the farther away objects are receding faster than the closer objects (or to put it another way, we are receding faster from those farther objects). ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:50, 8 March 2015 (UTC)

yes but you misread the question i said the same current distance but different speeds.66.87.82.116 (talk) 23:01, 8 March 2015 (UTC)

Building Mars on Earth

During the video embedded in this article, there seems to be a woman who is standing next to a Mars rover on what appears to be a Martian landscape. Have researchers at JPL, or anywhere else, been modeling the Martian landscape at a 1:1 scale? Dismas|^(talk) 06:38, 8 March 2015 (UTC)

It's probably easier to use Earth deserts that already resemble the Mars landscape. (Sometimes the only way you can tell the difference is if the sky is blue or red.) StuRat (talk) 14:18, 8 March 2015 (UTC)

The atacama desert resembles mars the most. — Preceding unsigned comment added by Joey13952 alternate account (talk • contribs) 17:38, 8 March 2015 (UTC)

Nah, the Atacama is just very very dry. Appearance wise there's this island in Northern Canada, I think that is closest in appearance to Mars and the folks at NASA use it from time to time. Sir William Matthew Flinders Petrie | ^{Say Shalom!} 17 Adar 5775 17:43, 8 March 2015 (UTC)

You are presumably referring to the Mars Society's Flashline Mars Arctic Research Station on Devon Island, though as Wnt points out, Dismas was asking about a different kind of modeling. -- ToE 23:46, 8 March 2015 (UTC)

That's the one! Sir William Matthew Flinders Petrie | ^{Say Shalom!} 18 Adar 5775 00:17, 9 March 2015 (UTC)

Acchcch, come on people, at least clicka the link before you answer! The link shows a believable simulation of the Martian surface generated by computer, and gives the strong impression they used real rover images to make it. The simulation may be intrinsically no different than any computer game in 3D, but to get the positions for all the rock faces I don't know if they used parallax between many images at known displacements of the camera or had some kind of nifty laser rangefinding or something available (someone could quickly look that up, I'm just being lazy; I doubt it). I don't know how accurate they're trying to make the simulation either, but again, guessing, I'd guess "pretty damn". Anyway, consider yourselves trouted. Wnt (talk) 21:40, 8 March 2015 (UTC)

So the quick shot of the woman standing next to the rover at roughly 28 seconds in is just green screening or some similar special effect? The shot is too short for me to really tell if there is green screening going on or if she's at some real/physical test location. Dismas|^(talk) 00:10, 9 March 2015 (UTC)

Nope, that appears to be a mock-up they built in Pasadena. I was going to mention it last night (and answer your question in doing so) after watching the vid but was either too drunk or too tired to post. Probably both. Sir William Matthew Flinders Petrie | ^{Say Shalom!} 18 Adar 5775 00:17, 9 March 2015 (UTC)

It's clearly a real location; I don't know where it is, but I know that there are artificial lunar/martian landscapes used for rover testing, such as the "roverscape" at Ames Research Center. -- BenRG (talk) 00:32, 9 March 2015 (UTC)

It says Jet Propulsion Laboratory, Pasadena, CA between 0:12 and 0:14 in the vIdeo. I didn't notice the JPL bit the first go around, but that's where it is, whatever it's called. Sir William Matthew Flinders Petrie | ^{Say Shalom!} 18 Adar 5775 00:42, 9 March 2015 (UTC)

It's the JPL MarsYard III (Google Maps, video panorama). -- BenRG (talk) 05:23, 9 March 2015 (UTC)

Sorry, I missed the shot at :28 because, well, it doesn't really look much like Mars. I mean, I've never seen photos of boulders sitting on top of a smooth surface like that; it just looked like a rover test course to me. Wnt (talk) 12:32, 9 March 2015 (UTC)

The Curiosity rover has a pair of "mast cameras" placed to generate stereo pairs, just like human binocular vision. From those, it's fairly trivial to extract reasonably accurate distance information to everything in the field of view - and as the rover moves around, you can assemble three-dimensional models for everything it's ever seen (and transmitted back to earth) through those cameras. The 3D models would be partial because the back sides of the rocks would never have been seen by the camera - I'd expect NASA to 'fill in' those details with similar-looking synthetic detail - which they probably mark somehow so that the users of the system know what's "ground truth" and what's merely in-fill. Once you have a 3D model, with color, texture, and lighting information, it's not difficult to write software to display that in a head-mounted display - it would be MUCH easier than writing a video-game. This is something that any competent graphics engineer could put together in a month...truly not "rocket science"...and these days, hardly an engineering challenge at all. SteveBaker (talk) 18:40, 9 March 2015 (UTC)

Thank you, all, for your responses! Dismas|^(talk) 14:11, 12 March 2015 (UTC)

The limits of mind

Did been a limit of the possibilities of mind?--85.140.136.25 (talk) 10:49, 8 March 2015 (UTC)

If the human mind is always been Goodness, so is it an absolute the mind of Lord God?--83.237.216.191 (talk) 11:53, 8 March 2015 (UTC)

please ask scientific questions, and in English. --OuroborosCobra (talk) 12:21, 8 March 2015 (UTC)

The natural nature of mind is it been absolute?--83.237.216.191 (talk) 13:11, 8 March 2015 (UTC)

You appear to be talking through google translate. It is not possible for people to understand what you are asking exactly. Beyond the rather basic fact that the human brain must have limits on its cognitive capacity, maybe you are trying to see if there are limits to what we understand. This may also be asked based on a confusion between limits on a person's own cognition and limits on the body of knowledge in general (the former not limiting the latter because of the nature of specialisation). If you try to read that through google translate, it will not be possible to follow what I am saying. Second Quantization (talk)

Google translate doesn't capitalize the word "Goodness" in the middle of a sentence. Nor is there any term in Russian that would translate as "did is been?" μηδείς (talk) 21:35, 9 March 2015 (UTC)

Is it in applied sense the (physiological) properties of the (neurons) neural net, as also as (physiological) properties of the neuron been absolute?--83.237.204.27 (talk) 14:20, 8 March 2015 (UTC)

For what the atomic (molecular) particle is the mostly similar been neuron?--83.237.204.27 (talk) 14:39, 8 March 2015 (UTC)

I suggest you post here in your native language and then one of us who speaks it can post a more meaningful translation. --TammyMoet (talk) 19:52, 8 March 2015 (UTC)

The storage capacity of the human brain has been estimated in a bunch of different ways - with wildly differing answers given - but there is, undoubtedly, a limit. In our Orders_of_magnitude_(data) article, the number 1.2 terabytes is offered...but this Scientific American article suggests 2.5 petabytes...which is a couple of thousand times greater. So the precise number isn't known. However, it's safe to say that nobody, no matter how smart could possibly memorize more than 7,500,000,000,000 digits of pi (for example). You can buy hard disk drives for your computer that are a couple of terabytes - so our memory capacity is between one and two thousand hard drives worth. So there is one hard limit.

Another hard limit is on processing speeds - we know that a neuron can't fire much faster than around 200 times per second - so even with all 100 billion of them working at once, we can't perform more than 20 trillion basic calculations per second. That's comparable to the graphics chip in a decent modern computer.

Another measure is this - in which they claim that the human brain can recognize an image in about 13 milliseconds - which is a little faster than a computer can (for example) recognize a face using the algorithms developed by FaceBook - but not much faster.

These are all theoretical maximums - the likely number of digits of pi that could be memorized (assuming you didn't memorize anything else!) will for sure be drastically smaller than that...so treat these as upper limits.

What these tell us is that the capacity, speed and general throughput of a human brain is very roughly comparable to a high-end desktop computer. That said, where we win is in the 'software' and general architecture of the brain. We store memories in a very compact way, storing concepts rather than pixels, or sound samples. We're able to dynamically reduce the precision with which old memories are stored and automatically erase the ones we don't need anymore. These are all things that computers can't do yet...and the consequences are that we can do things like rapidly recall all of the important details of a 100 year lifespan...a feat which seems to suggest vastly more storage than we really do have, mostly because we're exceedingly clever at how we store things and when (and how) we forget them. SteveBaker (talk) 18:29, 9 March 2015 (UTC)

So, in what is been the difference between a neuron from electron as an elementary physical-molecular particle?--83.237.217.95 (talk) 11:46, 12 March 2015 (UTC)

Do you actually understand the replies that are given to your questions? Your latest post suggests not, and I can see no point in responding if you are unable to demonstrate that your English comprehension skills are better than your writing. AndyTheGrump (talk) 11:52, 12 March 2015 (UTC)

Sorry for my English. I’m interesting in such as, In what is been the physical difference between a neural impulses from the electronic impulses, and could according to the universal Law of conservation of energy a neural impulse was keeping safed in an electronic impulse?--83.237.217.95 (talk) 12:03, 12 March 2015 (UTC)

I’m thinking, that could been done the flash (neurons) neural memory card as a simple flash memory card (SIMM) of electrons.--83.237.217.95 (talk) 12:11, 12 March 2015 (UTC)

In any case, the total between the neuron and the electron is always been a fact that the neuron as the electron could keep safed an information, so the neuron as the electron was always had a physical memory.--83.237.212.25 (talk) 12:37, 12 March 2015 (UTC)

Of course, a biological processes and physical processes could be irreversible, so that the neurons can degrade or mutate, and electrons can also aging.--83.237.212.25 (talk) 13:00, 12 March 2015 (UTC)

The physical state of an elementary particle or biological cell is their physical memory.--83.237.197.231 (talk) 14:09, 12 March 2015 (UTC)

Why did been necrosis of the brain, is it been because the electrons get older?--83.237.223.29 (talk) 15:30, 12 March 2015 (UTC)

Superconductivity of neural system of the brain is always been formed (determined) by speed of the electrical streams (by the speed of electricity) of neural system.--83.237.206.31 (talk) 18:09, 12 March 2015 (UTC)

From my point of vision in this issue all concludes in the value of the electrical bonding (connecting) in biology, physiology, genetics, biochemistry, and so goes on.--83.237.206.31 (talk) 18:26, 12 March 2015 (UTC)

Biochemistry papers

Why do many biochem papers not show the chemical structure diagrams. Only the formula. — Preceding unsigned comment added by 82.132.214.244 (talk) 16:01, 8 March 2015 (UTC)

Which paper(s) or publications are you reading?

Biochemistry (journal), a publication of the American Chemical Society, provides author guidelines with instructions on how to submit chemical structure diagrams, and further stipulates that details for complicated biological macromolecules must be uploaded in digital form to computerized chemical databases operated by partner organizations of the publisher.

Other publications may have different guidelines suitable for a different reading audience.

Nimur (talk) 16:12, 8 March 2015 (UTC)

Biomaterials. — Preceding unsigned comment added by 82.132.214.244 (talk) 16:39, 8 March 2015 (UTC)

If you mean Biomaterials (journal), a publication of Elsevier, here are the author guidelines. There are no guidelines or rules respecting chemical structure diagrams, formulae, or digital database formats for molecular structure. There is, however, a handy buzzkeyword list provided to authors. I could insert a snide commentary about journal quality and the role that economics plays in consolidating scientific writing into the hands of a very small number of private-sector, non-science publishing houses... but I think the guidelines speak for themselves. My advice, though, is pretty simple, and it comes from several years as a professional editor of research publications: read papers that are good, not papers that are published in "respected" journals. After you read a lot of papers, you will learn which journals (and which editorial staffs) have earned your respect. Nimur (talk) 20:59, 8 March 2015 (UTC)

Apparently it's assumed that the reader will know the structure from just the chemical formula or be able to look it up easily. — Preceding unsigned comment added by 82.132.214.244 (talk) 17:00, 8 March 2015 (UTC)

IUPAC rules are supposed to make chemical formulae readily communicable in words. Formulae are often included for new (or newly isolated) compounds, however, because of the possibility of error or misunderstanding. Wnt (talk) 21:43, 8 March 2015 (UTC)

Wind

You are in a field and it is windy. You have two possibilities. 1st: stay in the open, 2nd, enter a tube, which is straight and not perpendicular to the wind. What would be warmer?--Llaanngg (talk) 20:01, 8 March 2015 (UTC)

Is it cloudy in this hypothetical scenario? What is the wind speed? What is the outside air temperature? Is it day or night?

In all seriousness, we don't have enough information to answer the question definitively. Temperatures - and heat loss, which is actually a distinct phenomenon - are affected by many parameters beyond linear airflow. Why do you want to know, and how technical do you wish your answer(s) to be? Nimur (talk) 20:11, 8 March 2015 (UTC)

Just curiosity, to understand it. We could use a wind speed of 5m/s, which is a common air speed in many places, and 15 degrees C, and 45 degrees angle, for the tube. And why does being cloudy/day or night affects the experiment? --Llaanngg (talk) 20:28, 8 March 2015 (UTC)

The sun is a source of heat! A tube will shade you from sunlight. Heat loss through radiation into space is non-negligible! On a clear night, the interior of the tube may lose less heat (to radiation) than an exposed area.

Start by reading about heat conduction, convection, and heat radiation. These are the primary ways that heat flows. Wind is generally described best by convection (though there is thermal conduction by direct contact with the air mass, too). Ultimately, your tube experiment can be reduced to a more generic question: under what conditions does airflow cause so much more heat transfer that we can neglect all other forms of heat loss? The answer can be paraphrased: when the heat lost to flowing air is much greater than heat gained or lost by radiative or conductive transfer. Nimur (talk) 20:39, 8 March 2015 (UTC)

How big a tube? If I'm able to position myself to block much of its area and it's got a substantial length between me and the upwind end, I could probably prevent having much air move in front and behind me. But "much of" and "substantial" are pretty hard to model quantitatively without knowing a lot of specific details of the surfaces, etc. DMacks (talk) 20:37, 8 March 2015 (UTC)

And what is the tube made of? Is it nylon, cloth, concrete, metal, earthwork...? Is it in direct contact with the ground? Under ground? ... A half-buried concrete drainpipe and a metal drainpipe of equal size will transfer heat very differently. If both are exposed to the same conditions - say, a warm sunny day - a metal pipe can become scalding hot, while a concrete pipe can stay very cold. The air temperature in both tubes might be nearly the same.

Using more technical language: what is the thermal coefficient of the tube's material (how quickly does it transfer heat)? And what is its thermal mass (its heat capacity), or how much heat can it store? What is its albedo, or how efficiently does it reflect solar heat?

Nimur (talk) 20:43, 8 March 2015 (UTC)

The wind would be reduced if the pipe is at a 45 degree angle. However, a thick concrete pipe has a significant thermal lag, so that it will get hot later in the day than the air outside, and stay hotter as the air starts to cool. The color of the outside of the pipe also matters, as a black pipe will heat up a lot more than a white one, in sunlight. StuRat (talk) 05:41, 9 March 2015 (UTC)

Scarring

Why is it that most infections don't cause lasting damage and once fully recovered the person is just as healthy as before? Surely an infection anywhere, whether it's the stomach, lungs etc causes scarring and subsequently permanent damage. — Preceding unsigned comment added by 194.66.246.25 (talk) 22:14, 8 March 2015 (UTC)

Why would you think it would? You have evidence that it doesn't, based on all human history. There's little reason to suspect that it would. --Jayron32 00:09, 9 March 2015 (UTC)

Minor injuries, whether caused by injury or disease, can be repaired by replacing the damaged cells. This process happens all the time, when cells naturally die. It's only when too large of an area is damaged at once to use this method that scars are formed to quickly seal the damaged area. Unfortunately, we don't seem to have evolved a way to replace scar tissue with healthy cells later on.

To compare to a scratch on a car, if only the polish is damaged, then just repolishing it repairs it completely. But, if the damage was a tear in the sheet metal, then you might need to patch it with some Bondo, which is never quite as good as it was. StuRat (talk) 05:29, 9 March 2015 (UTC)

• The question is valid. Certain types of tissue, like epithelial tissue regenerate rapidly, while things like cartilage barely regenerate at all. Scarring is caused when the regenerative underlying layers of tissue themselves are damaged. But certain things like the skin and gut are designed to regenerate when not too badly damaged. Some minor scarring can fade over time. Cells are normally inhibited from reproduction when they bound upon other tissue (cancer occurs when this inhibition is lost). If the scar tissue slowly degrades, normal cells bordering it can reproduce and fill in the previously scarred area. That will depend on the age of the person and the size of the scar. μηδείς (talk) 16:14, 9 March 2015 (UTC)

Because evolution have left us with an immune system where most maladies are a trifle. Add to that, good wholesome chlorinated potable water, a balanced diet and a sanitation system to take all the wast products away, we are pretty well bullet proof. Rare (today) infections like Scarlet fever benefit from (our point of view, not the bacteria's ) antibiotic's because that can scare heart-valves and leave lasting psychological damage. --Aspro (talk) 02:00, 10 March 2015 (UTC)