Wikipedia:Reference desk/Archives/Science/2015 March 19

= March 19 =

Hydrogen peroxide and oxygen
How can I tell the difference between hydrogen peroxide and water without any materials or scientific tools? — Preceding unsigned comment added by 67.83.184.207 (talk) 00:29, 19 March 2015 (UTC)


 * Catalase. It's an enzyme in your skin that will break down 2 H2O2 -> 2 H2O + O2.  So if you touch H2O2 to your skin, it will bubble, but water won't.  Caveat: I'm speaking of over-the-counter hydrogen peroxide solution certified for use on human skin - you would not like the outcome of the experiment with the pure compound! Wnt (talk) 00:57, 19 March 2015 (UTC)


 * Taste it. If its strenght is something like  40 volumes you should dilute it down first – read the label.--Aspro (talk) 01:18, 19 March 2015 (UTC)

How about if I can't taste or touch it because it's too strong? — Preceding unsigned comment added by 67.83.184.207 (talk) 02:01, 19 March 2015 (UTC)


 * What can you do? If all you have is a glass of (by eye) clear, colorless liquid and you can't use any other items or devices, and you can't taste or touch it, seems like all you have are smell, hearing, and sight. Strong peroxide does have a smell compared to water (smells "clean" but not quite "chlorine-like cleaner", maybe reminds me of doctor's office disinfection or other disinfectants originally, but I've used it enough I just recognize it). Are you allowed to use and touch it with anything at all (i.e., colored paper/fabric, a rusty nail, mix it with actual water)? DMacks (talk) 02:36, 19 March 2015 (UTC)


 * Hydrogen peroxide will bubble a bit on it's own, but adding nucleation sites, like some sugar crystals, should get it going faster. Or you could just shake it. StuRat (talk) 05:14, 19 March 2015 (UTC)


 * Pure hydrogen peroxide's density is 1.450 g/cm3 and water's is 1 g/cm3. Get an equivalent quantity of water in an equivalent container and compare the two. Even of the hydrogen peroxide is diluted it will weigh more. I suppose the problem is a scale might be considered a scientific tool, so you would have to come up with weighing tricks like floating them in a tub of water and see which one goes deeper into the water or sealing them and seeing which one sinks faster in a tub of water. Of course, if it is a large enough amount, you could just feel the difference, especially if it is a high concentration. Richard-of-Earth (talk) 08:31, 19 March 2015 (UTC)
 * Darn, I just re-read the question and getting an equivalent amount of water would be using materials. Stu's last answer is best. Richard-of-Earth (talk) 08:41, 19 March 2015 (UTC)


 * If you're afraid to touch the unknown solution of hydrogen peroxide you could leak some blood into it by some means or other, with results as such. I don't know if releasing your own blood counts as "materials".  On a second look spit works also: .  I think every cell has to have catalase to withstand the oxygen in Earth's atmosphere, but a biological fluid with relatively few cells wouldn't necessarily need to have it, I don't think, so I'll leave some of the more prurient experiments in your capable hands. :) Wnt (talk) 14:18, 23 March 2015 (UTC)

Schrodinger's cat video
I was having a debate with a friend recently, who argued that he had good reason to believe (based on scientific principles) that our reality is caused by conscious observation. He then showed me this video, concerning the Schrodinger's cat thought experiment. The video explains that, according to quantum mechanics, a cat in a bunker with gunpowder (or, a box with a vile of poison) can be thought of as both alive and dead until one observes the cat; "the act of looking forces nature's decision."

However, based on what I know about quantum mechanics, this sounds a bit philosophical. The observer effect article states, "[the observer effect] is often the result of instruments that, by necessity, alter the state of what they measure in some manner." Certainly, when quantum physicists are doing experiments on a subatomic level, they cannot simply "look" at a particle and have its wave function collapse; they must be altering it in some way. So my question is, does the video have any basis in science? Does quantum physics account for the effect of "observation" on a macroscopic scale? Thanks for your input. 70.54.113.221 (talk) 16:40, 19 March 2015 (UTC)


 * Can you apply the scientific method to answer this question? Can you create a testable hypothesis and run controlled experiments to validate the hypothesis?  If not, this isn't science as practiced by scientists: it's metaphysics as described by lay-philosophers.
 * If you'd like to read what professional philosophers have written on this topic, the Plato Stanford Encyclopedia of Philosophy has a good review article: Measurement in Quantum Theory.
 * Nimur (talk) 17:11, 19 March 2015 (UTC)


 * Well, per quantum immortality, the cat always thinks it's alive... so you can wait a while... Wnt (talk) 17:12, 19 March 2015 (UTC)


 * Interpretations of quantum mechanics has a dozen or more answers to your question. Take your pick. Gandalf61 (talk) 17:28, 19 March 2015 (UTC)


 * Although I don't see an article on it, it seems to me your friend is talking about what's called a "reality construct." There is only one reality, but that doesn't mean we can know what it is or that we will necessarily agree on what it is. The statement "the act of looking forces nature's decision" is extraordinarily egotistical. Nature couldn't care less whether we're looking or not - and the cat will either be dead or alive, we just don't know which. The fact that we don't know has nothing to do with the actual condition of the cat. In short, it's an amusing but weak attempt to explain atomic-level behavior. ←Baseball Bugs What's up, Doc? carrots→ 19:01, 19 March 2015 (UTC)
 * sorry there more then one reality, there many worlds , and only when you satabilize , on dead or alive reality , it becume yours whis yours aye .thanks water nosfim.
 * A random Youtube video, even/especially one with 4 million views, is not a great authority, but since your friend cited it I suppose it's worth pointing out that it actually disagrees with his position: it says "we're just like the cat", implying that there's nothing special about our conscious experience.
 * The notion of a superposition of living and dead cat states has no operational meaning. The classical picture, that the cat is definitely alive or dead but we don't know which until we look, is consistent with every experiment that we could ever perform (if quantum mechanics is correct). The thought-experiment because famous because OMG DEAD CAT, not because it's intrinsically interesting. Even Schrödinger called it ganz burleske.
 * In situations where we can detect a measurement effect (by the vanishing of the interference pattern in a double-slit experiment, for example), consciousness plays no role. The interference pattern disappears when the particle's path is recorded by any device, whether or not a person ever learns the outcome of the measurement.
 * The measurement effect is a kind of interaction between the measurement device and the system, but it's definitely not an interaction in the conventional sense, involving contact forces or gravity or anything of that sort. This is most obvious in interaction-free measurement experiments. -- BenRG (talk) 19:59, 19 March 2015 (UTC)


 * If it is indeed the case that the cat is in an indeterminate state until the experimenter opens the box - then consider this extension to the original thought experiment: The laboratory containing the cat, the box and experimenter is also a closed system (to the extent that the box containing the cat and the poison gas contraption is also closed). It seems that the experimenter's wife happens to be the owner of the cat.  She is very concerned about whether it lived or died and intends to phone her husband to find out what happened 30 minutes after he is scheduled to open the box.


 * OK - so the experimenter opens the box and now, as far as he is concerned, the cat is now very definitely either alive or dead. But from his wife's perspective, the cat's situation along with that of her husband is now entangled too.  Until she observes the state of her husband, he is in a superposition of dreading her call because her cat is dead and a state of hoping she'll call soon so he can tell her the happy news.


 * There is no logical or physical basis to deny this - the quantum event that caused the cat to die (or not) used an intermediary system involving a particle detector and a poison gas cylinder - and that event didn't collapse until the experimenter opened the box. That same quantum event causes the experimenter to either regret performing the experiment or not - and his state of regret is just as entangled as that of the cat - and only collapses when the experimenters wife "opens the box ('lab')" by phoning him.  Before that phone call is made, you can't reasonably say that the state of the cat has collapsed from the perspective of the wife because the state of her husband is determined by precisely the same quantum event and it's consequences as the death (or not) of the cat.  But the state of the cat clearly did collapse from the perspective of the experimenter 30 minutes earlier when he opened the box - and the state of the poison gas contraption collapsed from the perspective of the cat some time even earlier than that.


 * You can extend this situation out further, to friends of these two people who live in remote cities...to aliens living 10 light years away. The collapse of the quantum state of that original particle ripples outwards into the universe - where it meets other entangled quantum events that may affect its consequences.  (Imagine if our experimenter brought home a copy of the cat experiment, complete with poison gas despenser and accidentally left it under his wife's favorite chair with the lid open...now that second quantum event causes another superposition of dead or not-dead wife that interacts with the dead or not-dead cat.  The universe in that locality now has a 4 way superposition.


 * Since quantum events of this nature must change reality in small ways all the time, the entire universe must be an insane superposition of an utterly ungodly number of states that have yet to collapse over the entire volume of space-time.


 * This brings you to the many-worlds hypothesis...and I think it's increasingly clear that this is the most reasonable explanation for all of this mess.


 * SteveBaker (talk) 21:03, 19 March 2015 (UTC)


 * The paradox of Schrodinger's cat is a crock, and is insulting to non-human animals. The idea that the cat is not resolved into alive or dead until a human observer opens the box is nonsense.  The state of the cat has already been observed by the cat.  Either the cat is alive, and knows that she is alive, or the cat is dead, and in that case the cat knew at least briefly that something was wrong.  I don't deny that interpretations of quantum mechanics are weird, but this particular weirdness is a crock.  I don't claim to have the answer to any question except that the paradox about the cat insults the cat.  Robert McClenon (talk) 21:37, 19 March 2015 (UTC)


 * The thought experiment is still completely valid if you use a human. In that case, she (the human) will know if she's alive, but to outside observers, she's in a superposition between alive and dead.  The OP's video makes this same point.  --Bowlhover (talk) 22:52, 19 March 2015 (UTC)


 * You all do realize that Schrodinger's cat was satire, right? Schrodinger totally thought it was insane and stupid, which is why he created the thought experiment, to show how insane and stupid some of the interpretations of quantum mechanics were.  -- Jayron 32 23:21, 19 March 2015 (UTC)


 * Schrodinger intended it as satire, but that doesn't mean he thought the species of the animal inside the box made a difference. It doesn't.  The thought experiment is equally valid or equally absurd whether the victim is a human or a cat.  (It doesn't help Schrodinger's case that the other interpretations of quantum mechanics are equally or even more absurd, such as positing that an infinite number of universes are created every second.)  --Bowlhover (talk) 00:04, 20 March 2015 (UTC)
 * The idea isn't that the universes are created - as in gazillions upon gazillions of tons of matter and energy just popping into existance. The idea is that this concept of quantum superposition - where a particle can be in multiple, quite different, states simultaneously - implies that the entire universe is in superposition of an almost infinite permutation and combination of superpositions.  As humans, our brains are only able to perceive one out of that near infinite number of states - which we understand as "reality".  We know that superposition exists - this is just an extension of that. SteveBaker (talk) 01:45, 20 March 2015 (UTC)


 * The concept here we are lacking is that of a sophist, someone who will teach you how to win either side of an argument. David Hume was a great modern example who ammased great prestige and fortune arguing that cause and effect was a dellusion and you could not be sure that an apple wouldn't turn into a blob of lava the very next second. He became famous off Descartes' dubito ergo sum. μηδείς (talk) 05:17, 20 March 2015 (UTC)


 * A very wise man once said "Shut up and calculate". We know quantum mechanics works.  The issue of how we perceive how and why it works is psychology, not physics.  That's why the endless debates over interpretations and meanings are fun, but ultimately fruitless.  -- Jayron 32 15:01, 20 March 2015 (UTC)


 * The fundamental issue is that time evolution is unitary which leads to superpositions and somehow you end up definite outcomes for measurements which seems to violate the unitary time evolution. The laws of physics offer no clue how you could get a non-unitary wavefuntion collapse, so we add that to postulates of quantum mechancis in an ad hoc way. This is the so-called measurement problem and it hasn't been resolved in the sense that there is a consensus in the physics community about that. But there are plenty of proposals on resolving this issue, so many physicists don't regard this as a problem personally, as they may support one of the proposed resolutions.


 * Often a provocative thought experiment like Schrödinger's cat is good at illustrating the rpoblem, but not so good at resolving the problem. Compare this to Maxwell's demon. There Maxwell could point to a problem with the laws of thermodynamics being universally valid given that matter consists of atoms and you are free to manipulate them. However, the original thought experiment could be resolved in the wrong way by arguing that a particular implementation was not going to work. The same problem arises with Schrödinger's cat. The wrong way to resolve this issue is by noting that decoherence sets in so fast that you will only deal with an object that behaves classically and that therefore there is no experiment that you can do that would have any scientific value, and that therefore this is just a nonsensical philosophical discussion.


 * The right way to resolve the problem would be to modify the thought experiment in a way that makes the tension of wavefunction collapse with unitary time evolution the only relevant factor. There are many ways you can do that, e.g. David Deutsch who is a big proponent of the Many Worlds Interpretation, has come up with a thought experiment were an observer is able to undo a measurement result and uncollapse the wavefunction (the observer then forgets what the result of the measurement was, but not the fact that a measurement was performed). This is based on rigorous arguments, and it shows that the Many Worlds Interpretation is actually not a mere interpretation, it actually makes different predictions compared to the Copenhagen interpretation when you contemplate observers that are able to remain in quantum coherence. Count Iblis (talk) 16:24, 21 March 2015 (UTC)


 * Theoretically I suppose a Schroedinger's cat video might be in a different state before you watch it than after. :) Wnt (talk) 14:20, 23 March 2015 (UTC)

Plant question
Can a single leaf cell taken from a plant be placed into plant rooting hormones and grown into a full sized specimen of the donor plant? Would the resulting plant reproduce as normal or be sterile? My Little Question Can&#39;t be This Interesting (talk) 21:29, 19 March 2015 (UTC)
 * I doubt it, the cell would have been "established" i.e. it is not a stem cell- as a "leaf cell", unable to produce roots on its own, although, if it was placed into another plant, then that was dipped into hormone powder?, but this would not be the clone of the original cell, it would be a plant with one cell introduced into itself. The concept you are alluding to I think is very similar to a "cutting" but in the case of a leaf cutting, the original leaf attachment is able to sprout roots, the leaf attachment seems to have the capability of becoming rooted-this is a very good question. This is again, just my limited knowledge of cuttings and plant propagation with cuttings, in this case we need a plant scientist/botanist to give us the correct answer. Read-write-services (talk) 22:39, 19 March 2015 (UTC)
 * I think you have mostly the right reasoning, but I think the correct answer will depend on what we call a "leaf cell" and what type of plant. For instance, I'm pretty sure the apical meristem of oxypetalum is pluripotent - they can shoot out stems, leaves, and roots anywhere on the plant that seems like a good place to them, and the meristem is just the tip of the stem, which is poorly differentiated from the leaf. So I think it's reasonable that with careful laboratory-controlled conditions somebody could clone one of them from one stem cell. It would probably involve very careful manipulation of light, nutrients, and substrate. Rooting hormone would probably help, but might not even be strictly necessary, as plants make that themselves to varying degrees. I can't dig into the scientific literature now, but I probably will over the weekend if nobody else does :) SemanticMantis (talk) 23:12, 19 March 2015 (UTC)


 * For the second question: if this could be done, it would be a simple clone, and would be able to reproduce normally, both through vegetative reproduction and sexual reproduction - what you are suggesting isn't that different from the types of plant propagation that people do all the time - growing clones from cuttings (rhizomes, stolons, stems, etc.), air layering and a few other related techniques. This is just humans tinkering with and assisting what plants already do. If the parent was a sterile hybrid, then the "daughter" or clone would be too. Incidentally, all the named apple varieties that you can buy at the grocery store have been propagated exclusively via grafting - apples don't breed true, and if you plant an apple seed, the fruit of that tree will certainly be different than the parent, and likely not very good. So there is an original Honeycrisp apple tree, an original Granny smith, etc, and every apple we eat is a first generation offspring of the original. SemanticMantis (talk) 23:12, 19 March 2015 (UTC)


 * See plant tissue culture and micropropagation. This doesn't always refer to using a single cell but as our article mentions, it sometimes does. See also  . Note that a single cell will generally be used for the production of genetically modified plants, whether transgenic or cisgenic. Totipotency rather than simply pluripotency is normally what's needed. SemanticMantis is right in that it does depend on cell type and plant, although there is research in to how totipotency can be induced see  . I would clarify one thing SM said. The plant will be able to reproduce normally, but won't necessarily be able to reproduce via sexual reproduction easily. One of the reasons why these techniques may be used is because some plants have difficult reproducing sexually at all (rather than simply not breeding true). E.g. most edible bananas are parthenocarpic, a number including those most commonly exported because they are triploid. While these can be reproduced via more normal vegetative means, plant tissue culture enables you to store a lot of different samples in plant tissue banks more easily (somewhat comparable to seedbanks). Of course these probably don't involve a single cell, although I think you may sometimes start with a single cell particularly if your trying to eliminate some disease. Producing disease free offspring is another reason plant tissue culture and microculture micropropagation may generally be used. Actually you may sometimes be able to produce seeds which would otherwise be very difficult to do. To be clear, this doesn't mean that there's something unique about the plant you produce via cell culture techniques, but rather that reproducing normally for that plant may not include sexual reproduction. (If you're doing genetic work, you may intentionally induce sexual sterility for a variety of reasons, but in that case your offspring plant is obviously intentionally not the same as the plant the parent cell came from.)  Nil Einne (talk) 00:01, 20 March 2015 (UTC)
 * Edit, I should clarify that while you may not always only use a single cell, the point edit: AFAIK isn't that the cells are different. Rather for convenience, safety, the difficulty obtaining a single cell, etc you may have tissue rather than a single cell. If you are able to propagate from plant tissue which would be of a single type, there's AFAIK no reason why a single cell wouldn't work. Nil Einne (talk) 00:24, 20 March 2015 (UTC)
 * Final clarification, while the distinction between pluripotency and totipotency is important, I'm not aware that it's actually that significant in plants. By which I mean I'm not sure that it's common that cells are pluripotent but not totipotent. See for example  and also the earlier links. Nil Einne (talk) 04:10, 20 March 2015 (UTC)


 * This is a rather common phenomenon. Opuntia the prickly pear cactus sprouts from "leaves" but they are technically stems, the spines being the leaves. The wandering Jew bears baby plants on stalks, and there are plants from which a new plant will develop out of the middle of a leaf, but I can't remember a species off the top of my head. μηδείς (talk) 05:05, 20 March 2015 (UTC)
 * There are 9 plants called Wandering Jew, which one did you mean μηδείς ? 62.56.48.4 (talk) 10:18, 20 March 2015 (UTC)
 * Presumably the one who won't die until The Second Coming? (BTW, I skipped over the word cell in the OP's question, to which the answer is yes, in a lab, they do it all the time as a way of propagating valuable clones that won't breed true.)  The plant I am thinking of looks like a bromeliad (I've never seen it flower) with striped white and green leaves, but is sends out runners, it doesn't bud from its leaves.  There are indeed dicot plants that will send out roots and a stem form the middle of a leaf, but like I said, I can't think of any names right now, sorry. μηδείς (talk) 16:11, 20 March 2015 (UTC)

Is there another less arduous method to collect focus group discussion data without having to transcribe the entire discussion word for word?
Can the researcher only take notes of the high-points of the discussion instead of transcribing every words uttered by the participants? — Preceding unsigned comment added by Rja2015 (talk • contribs) 23:07, 19 March 2015 (UTC)


 * You can do whatever you want, surely? Why not record the session? Vespine (talk) 23:17, 19 March 2015 (UTC)


 * I disagree - the researcher might very well exhibit either conscious or unconscious bias in the words they choose to write down and those they choose to ignore. Without access to the ultimate source data - you have no idea whether you're just getting the opinions and biasses of a single researcher. 01:54, 20 March 2015 (UTC)


 * How about voice recognition software ? Certainly not perfect, but I doubt if it will choose to only transcribe positive reviews, for example, as a researcher might. StuRat (talk) 04:13, 20 March 2015 (UTC)


 * For a time, back when we paid for cable, rather than stealing everything off the internet, we watched Special Report with Brit Hume (they replaced him with a badger whose name I can't remember). In any case, they used those boxes you turn all the way to the right if you feel positive and all the way to thef left if you fell negative about what is being said.  There was a line for conservatives, liberals, and independents, and it would fluctuate as people spoke.


 * The problem for the viewer was it was a distraction (one wanted to pay attention to the speaker, not what people though of the speaker) and there was a significant time lag, about 10-15 seconds, so you had to factor in that the response was to what the prior speaker had said 50 words ago. This is a less arduous means of gathering data, but a very imprecise one, since you mostly measure emotion, not thought, and there is only one dimension, when you know that people like myself would want at least three to feel comfortable. μηδείς (talk) 04:54, 20 March 2015 (UTC)


 * You seem to be thinking of some form of audience response measurement. For live TV, the result is commonly called "the worm" and is still sometimes used for election debates   although often with only a single worm (albeit I believe the data often does include different political groupings). Nil Einne (talk) 05:44, 20 March 2015 (UTC)


 * For clarity, are you asking about transcribing recordings? I.E. You will always have recordings of the sessions, you just want to know whether you need to transcribe the whole recording, or can take notes. If you aren't I agree with Vespire, the obvious question is why you can't record the sessions. If you are referring to transcribing recrods, I would suggest the answer depends significantly on what the purpose of the focus group is and how you plan to deal with the data. For example, if you're doing this for commercial purposes, and your client may want a transcription, then the answer is surely that you can't. If this is for academic research, and you're the only one likely to be analysing the data, and you won't actually be doing anything with transcriptions even if you make them, then perhaps it isn't necessary. (Usually you'd be expected to make the raw data available on resonable request, in such cases you can probably provide the recording.) There is perhaps some risk you'd more easily miss things, since reviewing audio recordings is probably going to be more difficult than reviewing transcriptions, so you'd need to take that in to account. Nil Einne (talk) 05:53, 20 March 2015 (UTC)


 * According to Qualitative Data Analysis from Start to Finish (pp.49-52) by Jamie Harding recording the video/audio of a focus group and later transcribing the proceedings is the standard practice. See the text for more details, exceptions, and recommendations; or, this short tutorial video on focus group data analysis, for why recording/transcription really seems unavoidable (as far as I can see). Now it is possible, that you have some other kind of focus group in mind than the one discussed by Harding (for example, along the lines μηδείς discussed; see also wikipedia article on focus groups), in which case you'll have to give us more specific details in order for us to be helpful. Abecedare (talk) 06:10, 20 March 2015 (UTC)


 * There is software used by stenographers for transcribing recordings e.g. depositions. Since it's used for something important, I assume it works a lot better than what YouTube uses for its hilarious machine-generated subtitles. Look into it and perhaps invest in a copy if you have the budget for it. I've transcribed (a small part of) a recording once--it was painful. I had to re-listen many parts multiple times to make sure that I heard every syllable right. It helps to an extent if you use a player that allows you to control the playback speed easily, so that you can re-play specific difficult parts at a lower speed. --173.49.16.112 (talk) 11:45, 20 March 2015 (UTC)