Wikipedia:Reference desk/Archives/Science/2015 December 1

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December 1

How plate tectonic works

1) Because I were told in college different place on the indicated plate (ie Africa plate) is moving in different direction, part of African plate is moving to ENE, part of it is du-east, it has NE and north-northeast, and it has northwest movements too. Is individual plates like Africa also moving to different speed too? Anywhere between 1 and 3 CM per year?

2) Australia is the same part of it is moving to the NW part of it is NE part of it is 4 CM per year, 7 CM per year. Do plates like Africa and Australia move in just one direction or one speed for entire place or different place on the plates is moving different direction and different speed.

3) Because [1] and Ron Blakey's website and Pangaea Ultima, Chris Scoteses website or article about Amasia. Which subfields are more detailed about plate tectonics? Geophysics or paleogeography?

4) Does recent date like 1999, 2009, 2013 also matter how accurate is the information about plate tectonics?

5) And also when scientist references Africa to be stationary plate and everything else rotates in respect with Africa, can scientist use other plates like North America or Antarctica to be stationery plate and everything else rotates with the respect of these plates?--107.202.105.233 (talk) 04:11, 1 December 2015 (UTC)

I added numbers to make answering easier:

1 & 2) Plates are composed of subplates, which move with respect to each other. Also, each plate is somewhat plastic, and they can be compressed or stretched to some degree. Compression causes mountain building, as in the Himalayas, while being stretched can eventually cause a rift and split a plate in two.

5) Yes, since no plate is attached to the core, you can use any plate as your fixed reference point. StuRat (talk) 04:18, 1 December 2015 (UTC)

Maybe a little pedantic, but the Himalayas are not being formed by the action of one plate compressing, but we are quite certain by the collision of 2 plates.Vespine (talk) 05:37, 1 December 2015 (UTC)

Yes, it's the collision of the two plates that causes them to be compressed, and build mountains. StuRat (talk) 17:45, 1 December 2015 (UTC)

• File:Global_plate_motion_2008-04-17.jpg is a good place to start. You'll note that several thing Stu and Vespine note above are shown in that map. Notably 1) Plates do not necessarily move in linear ways. Many plates turn or twist. The North American plate, for example, is very clearly turning around an axis located somewhere near the Gulf of Mexico. 2) Plates themselves are subject to stresses and strains based on how they interact with other plates, so for example, a plate edge will often be being shoved in a different direction than a location at the plate middle. This can be seen on that map where the Nazca plate is meeting the South American plate; the South American plate is generally moving N/NW, but along the edge where the Nazca plate is subducting under it, you see it is being shoved east. This shoving is in large measure responsible for the buckling of the South American plate, creating the Andes mountains. Just some more things to think about here. --Jayron32 13:11, 1 December 2015 (UTC)

To expand on that: a plate isn't a horizontal plane, it is a segment of a sphere. A segment of a sphere sliding about on a sphere is essentially rotating about a point, which means some parts will be moving faster than others. (Note: the axis of rotation need not be on the plate itself). Imagine for example that there were only two plates, with boundaries at the 0 and 180 degree meridians. If one moves east and the other west (e.g. spreading away from 180 degrees and forming a new mountain range along 0 degrees), they will be moving faster at the equator than at the poles. Iapetus (talk) 12:59, 4 December 2015 (UTC)

Where can I print or download the computer models which are currently accepted by the scientific community which prove climate change incontrovertible?

I met with my physics professor at a major american university which is about 1 tier below ivy league and we had a long chat that went way off topic into global warming and how the american physical society has unequivocally vouched for the strongest possible language in utmost support of the conclusions of climate scientists. (which is risky because Physicists as a group are tying their reputation and credibility to something which 33% of its members openly do not support)

This professor has done tons of current and recent research into quantum theory and collaborated with the LHC guys and helped advise on the design and setup of at least 3-4 particular experiments which the LHC ran for the benefit of quantum theory physicists. He was on the quantum theory "committee" which decided which atoms to smash at what velocity and what type of detection models to implement for the experiments.

He used a term "regressing on past data" which I'm sure makes sense to you guys. Basically his criticism is that climate change is so slow that the models are unfalsifiable in anyone's foreseeable lifetime because of 2 reasons: a) the definitive tracking of climate change is very problematic because climate itself has other variables which must be accounted for such as "negative feedback loops" in weather patterns and whole bunch of crazy stuff that happens in top layers of earth's atmosphere & b) the short term variance in weather patterns is allowed to contradict the long-term trend (i.e. it is perfectly acceptable to have a 15 year "cooling trend" within an overall 400 year "warming trend")

Long story short, I'm not asking for general information about climate change or anthopogenic global warming. I will outlive my physics professor and I just want a permanent copy which I can print or download that is the most currently accepted theoretical model which the current scientific consensus believes is the best model as of Dec 1 2015 (or if there is a 2-way or 3-way tie, I'm happy with that too) as long as I can either print it or save it onto my computer as a filetype which can be opened or read by a software program that is free or costs less than $100 for a personal/student license.

Lastly, I was a ref-desk sci regular for 5 years back in the mid & late 2000's when the "gang" was Stevebaker, tenofalltrades, jayron32, sturat, kainaw, the guy with fancy blue & white box username, and 5-6 others whose names have escaped me. It's good to see some familiar names from the good old days. (-: Adwctam (talk) 05:45, 1 December 2015 (UTC)

There is no such thing as "the most currently accepted theoretical model which the current scientific consensus believes is the best model". The point is that a range of models, with varying assumptions and varying levels of detail, show increasing CO2 levels producing an increase in temperature. If you identify a particular study, there is a good chance that the authors will give you access to the source code it used, but the thing you are asking for here does not exist. Looie496 (talk) 12:34, 1 December 2015 (UTC)

No computer model is incontrovertible. A model is only an attempt to generate hypotheses and check existing theory; it needs observation to say if it's true or not. The incontrovertible part has more to do with the Instrumental temperature record. This year will probably be the warmest year ever worldwide, as may next year... we'll see about the year after that (El Nino might end for now) but it won't be long until that record too is broken. Wnt (talk) 14:20, 1 December 2015 (UTC)

Well, even if it isn't the warmest ever, it wouldn't disprove climate change. Climate is about averages and trends, not about any specific event. Over time, the earth is trending warmer, but that doesn't mean that every minute is warmer than the last, or even that every year is warmer than the last. It's that, if you plot worldwide average temperatures over a long period of time, it is clearly trending upwards. --Jayron32 15:17, 1 December 2015 (UTC)

For those interested in the background of the incontrovertible kerfuffle, see American Physical Society#Statement on global warming. Note that the "incontrovertible" wording is not in the APS 2015 Statement on Earth's Changing Climate. -- ToE 15:22, 1 December 2015 (UTC)

(EC)The previous responses are good and relevant, but IMO missing some of the spirit of your question. I think you're mostly looking for references and access on the latest climate models. That's what I'll provide, but let's digest the above first: there is no one perfect/best model, and models don't prove things about the real world, and even given empirical records don't technically prove anything in the strong sense. But all of these help us muster evidence. (I'm talking about the nature of possible experiments, falsifiability, science is not math, etc. Please ask if you'd like more clarification of what I mean here).

But there are lots of cool models, and they can help us learn a lot! Part of the problem is that even though we can identify a few of the leading current models, there are several different types or classes of model that work completely differently. I do research in an adjacent field and there is a whole menagerie and ontology of model frameworks, assumptions, techniques, user-bases, governmental support, private support, and other issues, leading to a tangled mess of "models that we use to study climate change" The point is that a general circulation model is very different than the Upper-atmospheric_models. Some do dynamic radiative forcing, some do oceans separately, some do soil processes, some even model tree growth! Things like net primary productivity and ecosystem respiration are actually very important for regulating feedbacks to the carbon cycle, but no one model can currently handle everything.

For an overview of the current and best modeling systems that we use to research causes and consequences of climate change, you'll do well to read the publications associated with the Atmospheric_Model_Intercomparison_Project. One of the leading model products today is the Community_Climate_System_Model developed by NCAR. That's mostly for atmosphere only, when oceans are dynamically integrated the model would instead participate in the Coupled_model_intercomparison_project. The CCSM itself is not even a single monolithic model, but modular affair with lots of different submodels that can be swapped out. You can technically get the code and run it but--fair warning--it is going to be very hard work to get it up and running from scratch.

For additional bibliography, see the documentation for CMIP5/6 at WCRP's website [[2]], that has both technical specs for model-intercomparison, and also lists publications that review model performance. If there's any one specific model or group you'd like to know about, let me know and I can find more specific references. SemanticMantis (talk) 15:44, 1 December 2015 (UTC)

Oh, I'll also add that it's a little unclear whether you want the actual models (code, inputs, runtime environment, quality control, gap filling methods, etc. etc.) or perhaps just the output? Because you'd never want to print out everything that goes into something like the CCSM. I'm not even sure there's enough paper on Earth, depending on the grid size and sampling frequency of input data... Anyway, the output is much easier to come by, and you can get data dumps from the electronic supplementary material in e.g. most of the CMIP publications. SemanticMantis (talk) 15:53, 1 December 2015 (UTC)

Great answers all around. Also thanks again for treating my question as legitimate (as it was) since I know there's a lot of tension (and sometimes outright hostility) when discussing this topic for fear of pov-pushing and the random spark which can escalate a civil discussion into a hostile battleground and inevitably the Godwin's Law of internet debates comes to fruition!

I think it's safe enough for me to drop the next phase of my question probably this weekend because I literally had a 45-minute chat with a random physics professor at a very good school and the stuff he shared with me was very "off the cuff" and he just dropped all political correctness and told me explosive bombshells which were his opinions that I'm absolutely amazed by and it has motivated me (even though next week is finals week) to want to research the information he has said because the things he told me are not easily forgotten. Also, maybe some of you understand the curse of curioisity -- that if you don't follow up and investigate, you'll spend hours thinking back to it during times in your life which you should be focused on school or work or enjoying a family picnic but there you are -- unable to become fully immersed in said activity because the minute your mind is unstimulated, it will gravitate towards thinking about the target of your curiosity.

I will post the followup question here again on the reference desk in a few days because I'll have time to read the links and do all the followup research over Christmas break. Until then, I'll post at the bottom of my talk page if anyone is interested in knowing the scope of my next question. I always in the past made sure to properly use the ref desk and I fully understand that the contributors here could easily be watching cute cat videos on youtube or turning their brains to slush on reddit; so, I wanted to thank you guys for choosing the dopamine pathway in your brain that gives you a feeling of reward (productivity) for choosing to spend your valuable time here instead. Thanks-in-advance everyone! Adwctam (talk) 05:54, 2 December 2015 (UTC)

Q-carbon

This newly discovered phase of carbon is said to be ferromagnetic, harder than diamond, and can be made at room temperature and pressure with a common type of laser. It was said to have been published Nov 30, 2015 in Journal of Applied Physics] with citation Narayan, Jagdish; Bhaumik, Anagh (November 30, 2015), "Novel Phase of Carbon, Ferromagnetism and Conversion into Diamond", Journal of Applied Physics, doi:10.1063/1.4936595, but the DOI does not lead to the article, so editors at the Wikipedia article have claimed it is not a valid finding. Could someone confirm the publication exists? Edison (talk) 16:37, 1 December 2015 (UTC)

I cannot find the article at the website of the journal, but I am not able to login to the site, so maybe it is hidden from nonsubscribers. Does someone have access? It seems unlikely a college would issue a press release about a nonexistent publication: https://news.ncsu.edu/2015/11/narayan-q-carbon-2015/ Edison (talk) 16:48, 1 December 2015 (UTC)

(EC)Something's a bit fishy. Google scholar doesn't know the title. The Scholar profiles for the authors don't have it listed [3] [4]. JAP published an issue on Nov. 28 [5]. I have full institutional access to JAP and can't find the paper with their search box. The earlier 2015 paper by N&B, "Research Update: Direct conversion of amorphous carbon into diamond at ambient pressures and temperatures in air" has not been cited yet, according to Google [6] and APL Materials [7]. It would be very odd for these two authors to publish another article on the topic and not cite the Reasearch Update paper. My best guesses: the work is actually a conference proceeding, and not yet indexed, and may never be, depending on the conference. 2)The work is actually in press or in review at JAP (or even some other journal!), and so it isn't all-the-way fully published yet. I'd be very surprised if there was any outright malicious intent, both NCSU researchers are obviously legit and well-cited in their field, and have published many related articles in well-known journals. So I'm fairly confident that this work is not a complete fiction. As a final resort, I'd recommend contacting the senior Naryayan [8] or the junior PhD student Bhaumik [9] directly to help resolve the issue. SemanticMantis (talk) 17:20, 1 December 2015 (UTC)

Now that I see the press release: the release is dated Nov 30, and also claims the article will come out on that same day!. I bet the paper has been accepted and just won't come out online for a few weeks. Even in the digital age, papers can wait around a long time "in press" before they are really available to all. Note that JAP [10] has their current latest stuff online listed as Dec 7! So I think this is just a matter of the university press office playing a bit too fast and loose, and someone really shouldn't have let the DOI out until it was really and truly assigned to an actual published paper. SemanticMantis (talk) 17:20, 1 December 2015 (UTC)

• The typical process is that a news release is distributed before a paper is published, but "embargoed" so that it can't be reported on until the publication appears. However sometimes the process goes astray and the journal doesn't manage to get the paper out before the embargo expires. That's very likely what happened here. Chances are the paper will show up on the web site any time now. There is no way to confirm that the publication exists before it appears other than contacting the publisher. But there is nothing fishy here; I have seen this happen before. Looie496 (talk) 17:23, 1 December 2015 (UTC)

(Just because it happens doesn't mean it isn't fishy :) Call me old fashioned, but I think press release offices from major research universities shouldn't release incorrect "information". They could have just omitted the date of publication and the DOI and then everything would be fine. Maybe you've had better luck than I have but after some limited experience I'm surprised that press offices can tie their collective shoes... SemanticMantis (talk) 17:33, 1 December 2015 (UTC) )

The grant number pulls out related work, [11] for example. The release says he filed patents, and searching "Jagdish+Narayan" comes up with patents, but I don't see these (not sure they'd show up though). For a DOI from a timely press release to work is a rare exception - hell, for any DOI to work is a happy surprise! This apparently isn't it, though it sure sounds similar. Unfortunately, the guy does not seem to publish in ArXiv, which is the only journal that really matters. Wnt (talk) 03:49, 2 December 2015 (UTC)

• Hey (Edison—Wnt—Looie496) in case you hadn't noticed and want to check it out, the original DOI link now works, and the paper is now available (and I think freely accessible). Thanks Edison for pointing out this interesting work! SemanticMantis (talk) 19:28, 2 December 2015 (UTC)

• There's an article about it in the NYT today: "New Substance Is Harder Than Diamond, Scientists Say". —Steve Summit (talk) 18:43, 3 December 2015 (UTC)

Medication allowed by a blood donation

There are some exceptions, but it is allowed to donate blood while medicated. The exceptions are aspirin, anti-coagulants, and some other less common medications. Allowed are not only homeopathic medications, herbal remedies, and nutritional supplements (they are useless, so why not?), but almost all the others. Do they process the blood, or dilute it (and give recipients blood slightly tainted with medication they don't need)? --Scicurious (talk) 18:28, 1 December 2015 (UTC)

Whole_blood#Processing covers a bit of this. --Jayron32 19:16, 1 December 2015 (UTC)

Donated whole blood is fractionated into its components, as discussed in the above article. The answer really is that if a medication is problematic in donated blood, then you can't donate. If it isn't, then you can. Public health bodies determine what medications are problematic. The amount of blood you can take from a single donor is obviously limited. There just isn't that much of most drugs contained in that amount of blood. Also blood transfusions are only given when necessary, so there's a risk-vs.-reward calculation: the likely effects of the scant quantities of most drugs found in transfused blood are outweighed by the consequences of not receiving a transfusion. Actually you can donate whole blood if taking aspirin, but not platelets alone. This is because aspirin deactivates platelets. This is obviously a problem if you receive platelets from a single donor on aspirin, but for whole blood, the platelets are separated out, and many donors' platelets are combined to create a suitable dose, so it's not an issue. --71.119.131.184 (talk) 20:42, 1 December 2015 (UTC)

There are many exceptions, and rules differ in different countries. The considerations that blood bank staff have to make are:

1. Is the medication taken to treat a disease that the donor has forgotten to mention, or considered too trivial to mention? If so, is the disease compatible with blood donation? A major concern is whether blood donation is safe for the donor. Some of the drugs used to treat hypertension increase the likelihood of the donor fainting, something which may happen when the donor is about to leave the blood bank, or afterwards. Fainting may result in serious head injuries and other complications. If the donor is taking antibiotics, he or she will usually not be allowed to donate, both due to concern over whether donation may be harmful to the donor, and over whether the blood may be bacterially contaminated. Medication taken for a number of chronic diseases (systemic autoimmune disease, cancer, heart disease, and many others) will be considered incompatible with blood donation, not necessarily because the drugs are likely to hurt the patient, but because the donor's disease is incompatible with blood donation.
2. A small number of drugs may be harmful to the patient, or to the patient's fetus if she is pregnant. Some medications that have been used for treating psoriasis and severe cases of acne are teratogenic in minute doses, and may stay in the body at harmful levels (to the fetus) years after the donor has stopped taking the medication (Etretinate). --NorwegianBlue ^talk 23:04, 1 December 2015 (UTC)

The issues with donor conditions are a good point that I didn't address. You're right that some questions about medications are more about possible conditions the donor has rather than effects of the medication on transfusion recipients. I'm in the U.S. and I donate blood regularly so I'm familiar with the process. Here they're required by law to keep you around for 15 minutes after donation in case you faint shortly afterward. I don't recall ever being asked about antihypertensive medications, although they do take your blood pressure every time before donation. --71.119.131.184 (talk) 23:36, 1 December 2015 (UTC)

There has been a trend towards acceptance of many antihypertensives, and more so (I believe, though I dont have a good source) in the U.S. than in many European countries. The main problem is probably beta-blockers, which limit your ability to adjust blood pressure when posture changes. Here (PMID 7147333) is a fairly old paper, which found most antihypertensives safe, but omitted beta-blockers from the study. --NorwegianBlue ^talk 07:27, 2 December 2015 (UTC)

Living things consisting physical forms

List of living things that don’t move/grow/evolve? -- Space Ghost (talk) 18:55, 1 December 2015 (UTC)

Some viruses might qualify, if you consider them to be alive. Some of them do nothing more than wait for a cell to copy them, much like a chain letter. StuRat (talk) 19:10, 1 December 2015 (UTC)

As Stu aludes to, there's a fundamental problem in that there isn't a good, universally agreed upon version of the definition of life. As noted in that article "The criteria can at times be ambiguous and may or may not define viruses, viroids or potential artificial life as living." If things like viruses and prions are living things, then they qualify because they neither have their own mobility nor do they grow on their own. If however, you include in your definition of a "living thing" the ability to grow and move on one's own (which some definitions DO), then you've automatically excluded all things which don't, and that also answers your question. --Jayron32 19:14, 1 December 2015 (UTC)

I agree - the common definitions of life require movement/growth/reproduction or other things that imply that. Viruses that just sit there and do nothing are really not "alive" in any meaningful sense - they are just small-ish chunks of DNA wrapped in some kind of coating. Aside from that, you need to grow in order to reproduce - and if you can't reproduce then sooner or later you die. If that kind of life existed then sooner or later they'd go extinct. Viruses manage to survive because other living things handle the reproduction for them - so they would be the exception, if we considered them to be alive. SteveBaker (talk) 16:52, 2 December 2015 (UTC)

I understand what you guys are saying, but I'm not happy to rest thoughts on movement, self/non-self growth, mixing/not mixing with other in order to grow, reproduction or evolution. Its a 'living thing', regardless of whether it possesses a soul/spirit. There must be something that can certify the 'existence'. Space Ghost (talk) 20:30, 2 December 2015 (UTC)

Would you consider parts of plants or animals as living? It depends on your definition. When they are detached from their host they may be living for a while. Eventually it will die, and will not grow or reproduce. For example the wood inside a tree, an egg shell, or an amputated finger could be considered alive yet not move or grow. Graeme Bartlett (talk) 20:46, 2 December 2015 (UTC)

There are a wide range of cysts, tests, endospores, tardigrade tuns, and such that seem to just sit there for ten years but still are alive when put to the test. But they're not very interesting when not doing the things you say. Wnt (talk) 15:45, 3 December 2015 (UTC)

Yes - but all of those things do move and grow - they just don't do it continually. I presume there are endless possibilities for organisms that shut down for a while - an hibernating bear spends a lot of time without moving - and they aren't growing...but I doubt that a bear would fit our OP's criteria. SteveBaker (talk) 17:34, 3 December 2015 (UTC)

Do you know of any living things that don’t move/grow/evolve? I can't think of any (let alone a list). Not least because (as others have said) most definitions of life require it to be able to move, grow, and reproduce (with the latter being in turn necessary for evolution). Iapetus (talk) 13:02, 4 December 2015 (UTC)

Robots only;in some ways. -- Space Ghost (talk) 18:31, 4 December 2015 (UTC)

Most definitions of life require the ability to reproduce. So far, we have no self-reproducing robots. But if we did, they'd surely have to either move or grow in order to do so. SteveBaker (talk) 03:57, 5 December 2015 (UTC)

Okay, I understand... Thank you. -- Space Ghost (talk) 19:45, 5 December 2015 (UTC)

Jayron, Graeme Bartlett: Sorry for the delay, I had to review my docs. My defination is similar to what Graeme stated. -- Space Ghost (talk) 18:31, 4 December 2015 (UTC)

Abiogenisis

1. Did it occur simultaneously on earth in different places or occurred just in one place then divergence occurred over millions and millions of years?
2. Do we have any article that indicates all the divergences? A hierarchy or something?

Space Ghost (talk) 18:55, 1 December 2015 (UTC)

1) we don't know, so

2) See 1

For an overview of the origin of life on earth, see the Wikipedia article titled Abiogenesis. For the answers to your question, the article notes several proposed hypotheses for when and how life first developed, and we understand things in broad strokes, but we do not know exactly how it happened. --Jayron32 19:05, 1 December 2015 (UTC)

I recommend Stuart Kauffman's book At Home in the Universe [12] [13] for a very interesting and accessible perspective on abiogenesis. You also might want to read a bit about panspermia. Really, we don't know for sure that life did originate on Earth, it may have just shown up here after developing elsewhere. But then abiogenesis still had to happen somewhere at least once. SemanticMantis (talk) 19:59, 1 December 2015 (UTC)

As discussed, we don't know whether there was one abiogenesis event or multiple. However we don't need to know this to trace the evolutionary history of life back to a last universal common ancestor. --71.119.131.184 (talk) 20:47, 1 December 2015 (UTC)

I thin RNA world is a good article here. Vespine (talk) 23:44, 1 December 2015 (UTC)

We don't yet know whether abiogenesis was a simple and inevitable property of the early Earth - or whether this is an event that's so astronomically unlikely that it failed to happen in millions of other places and times in the universe - and we only exist by the slimmest of possible statistical flooks. If the latter, then for sure we're looking at just one event...if the former, then it would be surprising that only one event lead to everything that we see.

There is some suggestion that the surprising degree of Homochirality in all known living things would suggest a single (or very, very small number) abiogenesis event. Most chemicals in living things can theoretically exist in either a left-handed or right-handed form and the two forms are incompatible with each other - but equally efficient at doing the job. But it turns out that 100% of all living things "agree" on which form to use. This kinda suggests they all came from the same single source. If there were a large number of abiogenesis events, then we'd imagine that half of them would come out with clockwise-spiralling DNA (for example) and the other half with counter-clockwise spirals. That said, it might be that by luck, one handedness of very early life out-competed the other...but that's a tough sell.

It's not by any means a definite answer though - there are hints that life may have arrived on Earth via cometary or meteor debris from space - and there is an argument about the polarization of light in space offering a benefit to one form over the other.

It goes further than that - the biochemistry of all living things is fairly similar. The mechanism by which DNA and RNA work, for example, is essentially identical everywhere. The "genetic code" (which combinations of A's, C's, G's and T's code for what operations in the cell) is pretty an arbitrary pattern - but it's fairly consistent across all of life. There is no reason why other base-pairs shouldn't exist - they've been produced in the lab and artificially inserted into bacteria and grown...and in principle, different sets of those base-pairs could stand for operations like "STOP MAKING THIS PROTEIN" and such like.

So you'd expect that if life emerged independently in multiple places, that different letters would have been chosen - and would do different things...but we don't really see that.

So, again, like the Homochirality argument - it's hard to imagine that life as we currently see it could have emerged independently. That doesn't mean that life didn't spring up in (say) a couple of places - but one version consistently out-performed or out-evolved the other, resulting in one entire group vanishing sometime before we can see it in the fossil record.

So "we don't know" is still the right answer - but informed speculation suggests maybe just one abiogenesis event - or that only one event produced all of the life we see right now - while the descendants of all of the other events were somehow wiped out.

SteveBaker (talk) 16:42, 2 December 2015 (UTC)

Thank you for your helpful summary. -- Space Ghost (talk) 20:33, 2 December 2015 (UTC)

RNA_world#Support_and_difficulties has some interesting statements about how biological homochirality could a natural consequence of certain abiotic reactions that can produce enantiopure substances, based on ref [45] there. SemanticMantis (talk) 16:53, 2 December 2015 (UTC)

There can't be one abiogenesis event because scientist can create life on mud and under water. I would've thought that population III stars made the first step but I guess chemical compounds were created around 10-17 millions years (something like that) after the 'primordial atom' explosion in the 'universe', so can't pin point whether it came from outer space or not.

Any idea When life started on 'water' and when life started on 'mud'?

Space Ghost (talk) 20:33, 2 December 2015 (UTC)

Thank you all for the help so far. Love you all! -- Space Ghost (talk) 18:29, 3 December 2015 (UTC)

Smallest thing in the Universe

What is the smallest? 'Subatomic particles' or 'microscopic objects'? Can both be on Earth and in Space? -- Space Ghost (talk) 18:55, 1 December 2015 (UTC)

String theory has strings being the smallest thing, I believe. They would exist everywhere, since everything is supposed to be composed of strings. StuRat (talk) 19:06, 1 December 2015 (UTC)

(edit conflict) The smallest known "things" are point particles which have no meaningful dimensions. All Elementary particle have no meaningful volume as far as we can measure, so they can be represented as true point particles with no meaningful deviation from observed behavior. If you mean smallest as in smallest mass rather than smallest volume, there are also Massless particles. So, regardless of whether you mean "smallest volume" or "smallest mass", the answer is "zero, or so close to zero as to make no difference" and we have several examples of both types of particles. --Jayron32 19:09, 1 December 2015 (UTC)

No one knows what the smallest thing is because no one knows the volume of small things like electrons. Think about it logically, how do you measure something that is smaller than the measuring device that you use to measure it? And where do you define where the electron starts and where it ends? If you cannot measure it's physical dimensions, how do you calculate its volume? Do not confused the wave function of an electron with the shape of the electron. The wave function only tells you where the individual elecgtron is likely to be (and says nothing about the shape of the physical electron). 175.45.116.61 (talk) 00:02, 2 December 2015 (UTC)

As others have said, an elementary particle has no volume and is a point as far as we know. A composite particle does have a meaningful size. For example, a meson has a diameter around 10^-15 m, a little smaller than a proton or neutron. This may be the smallest thing that has a nonzero size. In general, any kind of composite or elementary particle can exist either on Earth or in space. However, most kinds of particles are unstable and only exist for a short time when there's some process to create them. For example, mesons are created when cosmic rays hit the upper atmosphere. --Amble (talk) 00:11, 2 December 2015 (UTC)

Thank you. -- Space Ghost (talk) 18:30, 3 December 2015 (UTC)

Mathematically speaking, if something literally has zero size, no matter how many of them you stack up you still have zero size. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:16, 2 December 2015 (UTC)

Physically speaking too. That's how bosons work. You can have any arbitrary number of photons in the exact same location, literally. You can place a billion photons in the same spot in space, and then you can put more there. That's how Coherence works in the particle model of light. --Jayron32 02:56, 3 December 2015 (UTC)

I read science fiction long ago that said there's a finite maximum possible luminosity and anything more luminous than that would collapse into a black hole from the escape velocity of its own mass-energy. Was that BS? I think it might've 10^{50 something} units and was the energy density of the Big Bang at 1 Planck time. Sagittarian Milky Way (talk) 03:05, 3 December 2015 (UTC)

Your claim is wrong. See e.g. the real numbers. The unit interval is made up entirely of points that have no length, yet the interval has length one. A bit confusing isn't it? We have a whole field called measure theory that discusses these things. If you'd like to know more about it, feel free to ask a new question. SemanticMantis (talk) 19:23, 2 December 2015 (UTC)

No. A line or a line segment has length, and each point on it is a location. But you don't get a line by stacking up points. A point has 0 length. No matter how many items of 0 length you bunch together, you still have 0 length. Unless you're operating in a universe where 0 x N > 0. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:51, 2 December 2015 (UTC)

Hey Bugs, riddle me this: what is in the unit interval that is not a point? Are there any two points that don't have another point between them? The unit interval exists solely of points, and if you'd read the article, you'd know that. The unit interval is by definition a collection of real numbers. Sometimes, an infinite collection of points can have zero length, like the Cantor set. However, other times, and infinite collection of points can have positive length, like the unit interval. You can even have more exotic sets that are made up of points, contain no intervals, and still have positive length: one example is theFat Cantor set. Whatever, I don't really care if you don't understand concepts of math that are usually taught to upper-level undergraduates or graduate students, but I will continue to correct you when you post un-referenced opinions about things you clearly don't understand. Math is about proof and logical implication, not what you think makes sense. Cheers, SemanticMantis (talk) 20:22, 2 December 2015 (UTC)

Between any two points there is/are an infinite number of points. A point is a location on a line or line segment, and any segment has an infinite number of locations. My "source" is (advanced) seventh grade math. It's unfortunate that I don't have my seventh grade textbook handy. But it's important to keep in mind that lines and points are not physical objects, they are merely concepts. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:29, 2 December 2015 (UTC)

Oh yes, I'm talking math only here. I don't know much physics at all, but I do know lots of math, and I know that the unit interval consists solely of points, and that it has positive length. And I know that your claim that I objected to is wrong. Please just admit that you're wrong, it will be good for you! You don't have to be right about everything, especially measure theory, which I suspect you've never studied. Don't feel bad, several great minds struggled with this stuff for hundreds of years! Even Newton didn't fully understand the continuum! Current students in the modern age spend months to years just to understand the basics of measure theory, and that's after people like Lebesgue did the hard work for us. So while I know that you understand 7th grade math, maybe you could acknowledge that the Cantor set and measure theory (speficically Lebesgue measure) are a little more advanced, and you are out of your element. I could ask you to trust me because I have a Ph.D. in math, but that's not how we work here. Instead, I ask you to trust the referenced information in our articles that I have cited above. Or just continue to argue with me about it - you might find that fun but I promise that it will just make you look bad. SemanticMantis (talk) 20:36, 2 December 2015 (UTC)

I'm just waiting for someone to explain it in a way that makes sense to my feeble brain. So far, I haven't seen it. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:00, 2 December 2015 (UTC)

No matter how little above zero the size of something is an infinite number of them stacked together equals infinite length. No matter how many things of zero length are stacked up they're still zero length. It's like the unstoppable force meets the immovable object, except here there is something in between (finite and non-zero) and good God the length of any line segment is in fact in that in between area. There's always more points between any two points, no matter how close they are to each other, you'll never run out of points, so the line is made completely out of points. In the real universe points are all 1 Planck length in size but that's just because the universe sucks. If it were better then there wouldn't be a smallest possible amount of space. So infinite points of infinite smallness can be the distance between one and zero on the number line (or pi and 5 or infinity and negative infinity). Sagittarian Milky Way (talk) 02:47, 3 December 2015 (UTC)

I won't insult you Bugs, but I will try to explain it this way. Elementary particles don't have dimensions, but when two elementary particles interact with each other, they interact over a space between them, governed by principles like the inverse square law, Pauli exclusion principle, and a whole host of other physics concepts. So, while the individual particles (elementary particles) have no defined volume, the fact that two particles separated by space and interacting between each other define a space; that's why composite particles have a volume where elementary particles do not: the volume is defined by the space between the particles governed by the interaction between the particles. Particles which do interact with each other in this way, and thus must be kept at some distance, and thus create composite particles that have a volume are called fermions. Particles that don't interact with each other that way, whose interaction is not restricted by physical laws are called bosons and can occupy the same space. Here's an example. A quark is an elementary particle with no dimensions. If you have a quark, it has no volume. If I take three quarks of the correct type, they will interact with each other by exchanging gluons with each other. Those gluons operate to keep the three quarks at a defined distance from each other. That defined distance between the three quarks, all swapping gluons, is what something like a proton its size: even though none of the individual particles (quarks and gluons) themselves have any volume, the complex dance between all the quarks and gluons occurs with some distance between all the particles, and THIS distance (the distance of interaction) is what gives the proton its volume. So, you CAN have some situations where volumeless particles interact to produce a composite particle that has volume. But you can also have situations where multiple volumeless particles can occupy the same space and thus "pile up" on each other more-or-less infinitely. The difference between "those point particles that need to interact at a distance" and "those point particles that can occupy the same space" is basically the two main classes of subatomic particles, fermions and bosons. --Jayron32 03:08, 3 December 2015 (UTC)

That's a nice explanation of how point particles can assemble to take up space in physics, but I don't know if that's what Bugs was even talking about, since the statement I objected to was about math. I'd encourage Bugs to ask a new question at the math desk if he wants to learn about the mathematics of how stacking up many zero-dimensional points with no length can result in a line segment with positive length. I've tried to give an explanation and references reflecting this fact above, but perhaps others can give a more clear explanation than I can. I wasn't trying to insult Bugs, and I meant everything I said above in good faith - the structure of the continuum is hard and confusing stuff, and lots of people have trouble with it, even e.g. Newton. SemanticMantis (talk) 13:40, 3 December 2015 (UTC)

• Many physicists think the smallest thing is a quantum of space, known as a Planck length. But the Planck length is so small (1.62×10⁻³⁵ meters) that we are many orders of magnitude from being able to observe it. It is so small that the ratio of a Planck length to the size of a hydrogen atom is similar to the ratio of a hydrogen atom to the solar system. Looie496 (talk) 13:50, 2 December 2015 (UTC)
  • Very small, but still > 0. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:53, 2 December 2015 (UTC)

Does this help? If you place a brick on the floor, each end of the brick represents a point. If you butt another brick against one end of the first, the end of the line of bricks shifts to a new point. If you keep on adding more bricks, you can say that the length from start point to end point is n bricks or whatever distance unit you want to use, but you cannot pull out all the points and bunch the bricks closer together, nor can you add all those points to one of the end faces to set a new point. That is because the points have zero length. They only demarcate the positions of the ends of the bricks. So a line cannot be formed from a set of points. There must be some item, or items, of finite length to assemble the line. Akld guy (talk) 22:50, 2 December 2015 (UTC)

You're right, a line cannot be formed by stacking points up. A line is what it is. A point is a location on the line. A line has an infinite number of locations. But you don't build a line from points. The line already exists (as a concept) and locations on it are points. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:58, 2 December 2015 (UTC)

No, sorry, that's also incorrect. People can believe whatever they want but that description is incompatible with the mainstream mathematics we teach to (some) college undergraduates. Finite collections of points can have no length in total. But infinite collections of points can. One example, which I'll link again, is the Fat Cantor set. Strange things happen when we look carefully at infinite collections, and they often behave in unintuitive ways. A simpler example is that the unit interval consists of uncountably many real numbers. Each real number has no length, but the interval has a length of one. SemanticMantis (talk) 14:32, 3 December 2015 (UTC)

Infinity and its relationship to finite measurements are fun (and often useful) intellectual exercises. The Koch snowflake is actually an elegantly simple example of how infinity and finiteness can be related in interesting ways. The Koch snowflake has an infinite perimeter, but a finite area. If one extrapolates the elegant and simple Koch snowflake to more complex problems, you get all sorts of wide ranging applications, from the coastline paradox to possible solutions to the Shape of the universe which can be infinite in some ways and finite in others. --Jayron32 04:04, 4 December 2015 (UTC)

I get the idea somewhow/someway. I'll read the articles when I get the time... Thank you all. Regards. -- Space Ghost (talk) 20:43, 2 December 2015 (UTC)

I'm smart too. -- Space Ghost (talk) 18:30, 3 December 2015 (UTC)

Psychology of phobia of needles

Why is it that despite all the needle technology that's developed resulting in quick and painless injections/blood draws, there are still many people who faint or feel light headed after such procedures? Is it more psychological? Or to do with the thought of a foreign object entering them as opposed to the pain? 2A02:C7D:B901:CC00:48FD:38FA:EDCD:5A40 (talk) 20:53, 1 December 2015 (UTC)

It's never painless. And I don't have a phobia about it, but I don't like it, either. You've raised various explanations, any of which could be true for a given peron. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:14, 1 December 2015 (UTC)

Especially Evita and Juan. Clarityfiend (talk) 08:27, 2 December 2015 (UTC)

We have an article on Fear of needles that contains some possible explanations. --LarryMac | Talk 21:30, 1 December 2015 (UTC)

I've had over 1000 injections of insulin, about 300 allergy shots, test my blood sugar from 1-3 times daily, and spent 6 months on an IV drip that had to be changed 3 to 4 times daily. Many of the insulin and allergy shots were entirely painless. I have fainted a handful of times when I have had blood drawn (out of over 100 times during my life) even though the pain was not an issue, and I was used to it. (Having the IV changed was the most painful by far, and blood sugar testing always hurts.) Strangely enough, having seen people shoot up in NYC, and having found a guy dead in the stairwell with a needle in his arm, I asked my doctor to prescribe an insulin pen, rather than a vial with syringes. She diagnosed me as needle phobic! In any case, the fainting when you have blood drawn is due to the drop in blood pressure: vaso-vagal syncope. μηδείς (talk) 22:53, 1 December 2015 (UTC)

Just how little blood was in you to begin with ? Reminds me of Mr Burns: "Try drawing blood from this arm, I saw some in there just the other day !". StuRat (talk) 02:16, 3 December 2015 (UTC)

Ehxcellent. μηδείς (talk) 01:51, 4 December 2015 (UTC)

I go along with user: μηδείς regarding the vasovagal response. It is not the loss of blood volume (in case readers misunderstood what μηδείς stated) as a syringe full of that rich red claret in itself causes less drop in blood pressure than from going from a seated position to standing up. It is more of a result that our blood vessels and nerves cross talk. [14] . Sitting calmly in a surgery one is unlikely to feel anxious (or have adrenaline coursing through our veins) (like our ancestors would have whilst chasing mammoths and spilling a lot of blood on the way). Adrenaline is a vaso restrictor so helps to maintain blood pressure and thus an antagonist against the vasovagal response. This brings me to asking a question. Here in the UK we get a cup of tea and biscuits (cookies) after donating blood. The people that pass-out are inevitably those that haven't eaten for hours beforehand – so why not provide the tea and biscuits first? If they wish to give us something afterwards, a nice thick rare steak (to replace all that lost iron) would be my idea of a nice cup of tea. Moral of this story is this: if one is going to receive a puncture wound in a relaxed environment – eat before hand or be afraid, very afraid or both. So as user: μηδείς points out – it can not be , no way, a phobia -because phobic don't tend to faint if they don't faint at the first sight of the that little silver tube with a very sharp tip.--Aspro (talk) 21:01, 4 December 2015 (UTC)

One reasonable reason to have a fear of injections is that it bypasses your body's natural defenses, allowing potentially lethal microorganisms and chemicals into your body. The idea of fear is that it should motivate you to be careful in a dangerous situation, where caution is indicated. So, just as you would hopefully be careful if you needed to cross a canyon on a rope bridge, hopefully you will also be careful before you allow anyone to inject you, say by checking the label on the vial to make sure it is what it's supposed to be, and at the proper concentration. StuRat (talk) 02:16, 3 December 2015 (UTC)