What software would you use to model something spreading in water (river, lake, sea)? <small class="autosigned">— Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/31.4.152.13|31.4.152.13]] ([[User talk:31.4.152.13|talk]]) 23:45, 16 January 2015 (UTC)</small><!-- Template:Unsigned IP --> <!--Autosigned by SineBot-->
What software would you use to model something spreading in water (river, lake, sea)? <small class="autosigned">— Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/31.4.152.13|31.4.152.13]] ([[User talk:31.4.152.13|talk]]) 23:45, 16 January 2015 (UTC)</small><!-- Template:Unsigned IP --> <!--Autosigned by SineBot-->
:The look of it? Maybe Blender. The actual physics? Maybe Simulink. [[Special:Contributions/75.75.42.89|75.75.42.89]] ([[User talk:75.75.42.89|talk]]) 00:38, 17 January 2015 (UTC)
Revision as of 00:38, 17 January 2015
Welcome to the science section of the Wikipedia reference desk.
The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
I have heard that Poly oxalate is applied after placing the foam spray in a structure, I want to know what properties does this chemical has? and how is this applied.120.28.45.234 (talk) 05:38, 12 January 2015 (UTC)Garry from Philippines.[reply]
different units used in blood pressure measurement
My doctor measured my blood pressure and told me the result was 18. As he is French and I am English, that meant nothing.Could someone please tell me what that is in pounds,shillings and pence and whether he had reason to be anxious. I am 66, Thank you. — Preceding unsigned comment added by 109.12.62.210 (talk) 12:17, 12 January 2015 (UTC)[reply]
My first reaction was to comment that you are unlikely to read this reply, but perhaps it depends on where the pressure was measured and in what units. The usual units are millimetres of mercury, but perhaps French doctors use different units (centibars? but 18 would be a bit high). Alternatively, perhaps the measurement was for systolic pressure measured in the pulmonary artery or right ventricle, then 18 might be normal, but this measurement is an invasive procedure done in a hospital. Dbfirs 12:31, 12 January 2015 (UTC)[reply]
You might call them centibars, yes, but the usual term is kilopascal (kPa). There's an online converter here. - Lindert (talk) 12:36, 12 January 2015 (UTC)[reply]
The following discussion has been closed. Please do not modify it.
Oh yes, I should have checked that. You should have been told two figures. I assume that the 18 is systolic, and equivalent to 135 mm Hg which would be classed as Prehypertension in the USA or just on the high side of normal in the UK (but not serious). We can't give medical advice, of course, so you should go back to your doctor if you are worried. Dbfirs 12:50, 12 January 2015 (UTC)[reply]
I'm hiding ("hatting") this paragraph because it makes an unwarranted assumption with dangerous medical implications if the assumption is wrong. RomanSpa (talk) 13:12, 12 January 2015 (UTC)[reply]
In France blood pressure is measured in kiloPascals, while in the UK blood pressure is measured in "millimetres of mercury", which is almost exactly the same as another unit called the torr. There are technical differences in the way these different units are defined, and you can read about them here, here and here, but the main thing you need to know is simply the conversion factor, which is 7.5. That is, when your doctor said the result was "18" he meant "18 kPa", so to convert this into the measure you are used to you just multiply by 7.5. So 18kPa = (18 times 7.5)mmHg = 135mmHg. So his "18" is your "135".
As you know, Wikipedia is not able to give medical advice, but you will see from our article on blood pressure that doctors usually provide two measures of blood pressure, "systolic" and "diastolic". You can compare your reading with a standard table here, and should clarify with him whether your result was for systolic or diastolic blood pressure. In any case of illness or uncertainty, you should always contact your doctor. RomanSpa (talk) 12:56, 12 January 2015 (UTC)[reply]
One worrisome thing in this question is that you didn't ask the doctor. If you aren't even comfortable asking him what units your BP reading is in, and whether that's the diastolic or systolic reading, then I doubt if you are asking him any questions at all. Many studies have shown that such a lack of communication with your doctor is quite bad for your medical outcome. In the US, we even have a series of PSAs encouraging patients to ask their doctors questions. StuRat (talk) 16:01, 12 January 2015 (UTC)[reply]
Thank you to the kind people who answered my question. With regard to asking a doctor questions - there speaks someone who is used to just one language and one system. I have been in France over 2 decades and speak such good French I even write poems in it. Of course I asked questions but, in all honesty, the doctor did not know the answers. He only knows his own system. (To add to the confusion, 18 might have been one word or 10 and 8, which is how the French say 18. So he might have been quoting me one number or two. The latter result would have converted me from hyper to hypo.) This has happened before when, presented with printouts of blood tests or even Xrays taken abroad, the doctor has refused to look at them and insisted all be done again because, in reality, he did not understand them. You might remember that if ever you need the services of any professional not trained in US. — Preceding unsigned comment added by 109.12.62.210 (talk) 09:55, 13 January 2015 (UTC)[reply]
Well, the doctor certainly knew the answer to whether he was saying one number or two, so you should have at least asked that. It's possible he didn't know the units he was using, but a quick look at the readout on the sphygmomanometer should answer that Q. StuRat (talk) 15:00, 13 January 2015 (UTC)[reply]
Why do electric guitars have tunable bridges but acoustic guitar fixed ones
I'm not sure if this is the right forum for this, but I wonder why electric guitars have tunable bridges but acoustic guitars have fixed bridges and saddles. The tunable bridge allows the length of individual strings to be changed. I know that some acoustic guitars have compensated saddles, which come with different lengths set from the factory, but this is just a set and forget.
Also am I right in thinking that even for an electric guitar this won't ever change as long as the strings are uniform in thickness and weight along the length? -- ????
The general consensus here is that tunable bridges have too much mass for an acoustic and kill the tone. Also, tunable bridges have moving parts and, because an acoustic works by resonance through the body of the guitar, the moving parts will tend to vibrate against each other and rattle. This doesn't matter with an electric guitar as they have pickups that convert the vibrations of the strings directly above them into an electrical signal, but not vibrations from elsewhere in the guitar body. Richerman(talk) 14:25, 12 January 2015 (UTC)[reply]
That makes sense. The weight at the saddle is dead weight at the point where the string needs to vibrate the resonator. The moving parts bit also makes sense. In electric guitars the bridge can be fixed solid to avoid vibration, as the string is the only thing that needs to vibrate -- Q Chris (talk) 16:26, 12 January 2015 (UTC)[reply]
TTL IC L293D
I was playing with the TTL IC L293D when something interesting happends.
The motor keeps running while the pin Enable 1, 2 is not connected.
It's alive! It's alive!
I thought the motor must be stopped. What was wrong with this? -- Toytoy (talk) 14:22, 12 January 2015 (UTC)[reply]
Why do presume "not connected" means "low"? Unless otherwise specified, I would usually assume that a pin not tied one way or another will float to wherever it wants. That why God invented pull-down resistors. --jpgordon::==( o ) 17:03, 12 January 2015 (UTC)[reply]
Indeed. Looking at the TI datasheet (page 7), the enable inputs have an internal pull-up resistor, so they need to be connected to ground to disable the output. With no connection, they'll be high and the output will be active. Tevildo (talk) 21:19, 12 January 2015 (UTC)[reply]
genetics
thx. I know it is basic, but I seem to have missed this lecture.72.183.121.78 (talk) 22:46, 12 January 2015 (UTC)
my question is about the transcription of chromosomes in humans. for example, are all genes on both the maternal chromosome 1 and the paternal chromosome 1 transcribed? Or is either the maternal or paternal chromosome 1 shut down and only the other completely transcribed? or is there partial transcription of both? how does this happen? thx much.72.183.121.78 (talk) 16:32, 12 January 2015 (UTC)[reply]
The nature of recessive genes tells us that both parent's chromosomes can be used. Once the two haploids come together to make a diploid of genetic material, there is just "the two chromosomes" with zero differentiation between which one came from which parent (with the exception of a male offspring's Y obviously coming from the father). DMacks (talk) 17:25, 12 January 2015 (UTC)[reply]
thanks. so at that point are all of the genes of both chromosomes transcribed? if not, then why are some genes transcribed and some not?72.183.121.78 (talk) 17:44, 12 January 2015 (UTC)[reply]
You get half your genes from each parent (not counting mitochondrial genes, which come exclusively from the mother). So, there is a 50% chance you will inherit a gene from that parent, and a 50% chance you won't get that gene from that parent (although you might still get the same gene from the other parent). However, not all genes you inherit are activated. Many remain dormant. In some cases, you must inherit 2 copies of a gene (one from each parent) for it to be activated (or fully activate, at least). For example, the gene that causes sickle cell anemia is only a serious problem when 2 copies are present. Also, mutations can occur, in which case the gene you inherit isn't quite the same as the original in the parent. StuRat (talk) 17:51, 12 January 2015 (UTC)[reply]
Transvection (genetics) is one of several interesting aspects of the nature of the non-independent nature of the two different chromosomes' copies of some genes. The ABO blood group system is a case where both alleles are transcribed. I don't know much about the general idea of gene silencing in specific relationship to the presence of two copies. DMacks (talk) 18:01, 12 January 2015 (UTC)[reply]
thanks. that helps. I am interested in the autosomes.72.183.121.78 (talk) 18:14, 12 January 2015 (UTC)[reply]
I was confused, I read that as one single chromosome, rather than the first of 23 chromosomes, sorry. μηδείς (talk) 19:12, 12 January 2015 (UTC)[reply]
Remember, the gene is just the location of the information, the allele is the version or type of information that is carried. For a certain gene X, every human has that gene, insofar as we all have some information in that location of our DNA. However, many of us will have different alleles at that location. It is very common to confuse the two concepts, but we should be clear about the distinction on the reference desk. SemanticMantis (talk) 19:57, 12 January 2015 (UTC)[reply]
Our article says "locus" is the name of the location. As I understand it, the "gene" would then be something like "eye color", and the "allele" something like "blue eyes". StuRat (talk) 20:07, 12 January 2015 (UTC)[reply]
The difference is that a locus can be any region, e.g. a gene, a sequence, a portion of a chromosome, etc. Many people prefer to not use the word 'gene' at all, and instead use locus and allele for the separate concepts. This helps to avoid the nonsense of using 'gene' to mean both the region and the information stored at that region (which is what our askers and respondents usually do here on the ref desk). Still, the definition we use for 'gene' in our article makes it clear that it is ultimately a location or region:
“
"a locatable region of genomic sequence, corresponding to a unit of inheritance
”
(emphasis mine) The gene is not the "what" of inheritance, it is the "where." I just think we should make it a habit to use the right words for concepts on the ref desk, instead of perpetuating a common-but-incorrect usage. But your example is basically right (though there are many genes that control eye color) - everyone has genes for eye color, you get one allele from each parent. This also illustrates why it is technically incorrect to say "I got this gene from my father" - you would still have genes for eye color no matter who your father was, but a different father can lead to different alleles. I may seem picky here, but this is basic stuff, and is usually stressed in any intro bio course that covers DNA and inheritance. SemanticMantis (talk) 20:49, 12 January 2015 (UTC)[reply]
To quibble slightly, you can be missing genes. For example, a woman is simply missing SRY, has no place to put it, like anything on the Y chromosome. It's also possible that someone is missing both copies of some nonessential gene through deletion mutations, though far less likely. Where this gets tricky is that a fair number of characteristics, even common ones, are caused by null mutations in which the gene is functionally disrupted; it's as if it isn't even there, for many practical uses. But since often there is no actual deletion, just a frameshift mutation or a particularly bad point mutation, disrupted enhancer element, etc., the gene still recombines, so it's not really right to say that someone is "missing the gene"; just that what they have isn't active or effective. Wnt (talk) 02:56, 13 January 2015 (UTC)[reply]
@Wnt: Thanks for the clarification. I was pretty sure truly missing genes were possible as a rare event, but I didn't know the right names. Basically I've noticed that ~95% of the uses of "gene" on ref desk should really be "allele", and decided to start my own mini awareness campaign. I can tolerate the sloppy/incorrect usage on TV or in the bar, but I think we should hold ourselves to a higher standard here ;) SemanticMantis (talk) 15:39, 13 January 2015 (UTC)[reply]
thx for above. I realize that I am going to seem really stupid with this question, but I actually have made some effort to find an answer outside of this forum. in a somatic human cell, concerning the conventionally labeled autosome pair number 1, is one of the pair totally from the mother and one totally from the father? thx. — Preceding unsigned comment added by 72.183.121.78 (talk) 16:14, 14 January 2015 (UTC)[reply]
Concerning your original question, you may want to read about lyonization. Maproom (talk) 19:08, 15 January 2015 (UTC)[reply]
thx. will do. what about my second question about autosomes?72.183.121.78 (talk) 20:29, 15 January 2015 (UTC)
I read the article. I guess that means that in the autosome pairs also, one is totally from the mother and the other is totally from the father. I guess I just wish you would confirm that. thx much.72.183.121.78 (talk) 13:07, 16 January 2015 (UTC)[reply]
Effective Lifetime of Hydrogen Peroxide Solution
If I have a sink filled with 10 gallons of a 4% hydrogen peroxide solution how long will it last? How would I calculate it? The temperature should be "cold" tap water. This would be indoors, but there would probably be some light. I basically want to figure how long it can be used to effectively kill yeast on produce before needing to mix a new batch. Thank you. Any other additional information that you think I should be aware of would be greatly appreciated. David Bradley I (talk) 20:09, 12 January 2015 (UTC)[reply]
I believe nucleation sites are critical to the formation of oxygen bubbles from hydrogen peroxide, meaning it there are many nucleation sites it won't last nearly as long. Note that washing food with it will "use it up", as well.
One rather simple way to test it would be to put a sample in a bottle and shake it. If it foams up (many tiny bubbles), it's still good. If it reacts like normal water (few, large bubbles), replace it. After doing this test several times you can get an idea for how long it tends to last, under your conditions. StuRat (talk) 20:15, 12 January 2015 (UTC)[reply]
Thanks for the tip. Is there a way of estimating how long it should last? I only need it to work for a couple hours. Also, I'll ask another question in another section which is related. David Bradley I (talk) 20:19, 12 January 2015 (UTC)[reply]
I don't think you could get a good estimate without testing it under your conditions. For example, if you wash produce with lots of surface area, it won't last as long. Under some conditions, I don't think it would last 2 hours.
BTW, in case you don't already know, you should wear gloves and safety glasses when using it. It will hurt a bit on any cuts or hangnails on your hands, and really hurt if it splashes in your eyes. StuRat (talk) 20:21, 12 January 2015 (UTC)[reply]
Even if it is active, it might not have the desired concentration. It is a conundrum for me. David Bradley I (talk) 20:25, 12 January 2015 (UTC)[reply]
Maybe I'll buy a cheap bottle of medical hydrogen peroxide and do some tests at home to see how long it lasts. Maybe that would be a good way of estimating how much we'll need. David Bradley I (talk) 20:46, 12 January 2015 (UTC)[reply]
Have you considered not putting it in a tub, but just pouring it over the produce ? If you keep it in a dark, sealed container, between uses, it will last longer. However, soaking in a tub will get more of it into contact with the produce (the hidden folds, etc.). What kind of produce is it, anyway ? StuRat (talk) 20:34, 12 January 2015 (UTC)[reply]
I think for our setup we couldn't just pour it over. I'm not sure how long the produce should soak in a 4% solution, but I was thinking 10 minutes. Is that too long? It might be possible to cover the sink to keep it fairly dark, but it wouldn't be sealed. David Bradley I (talk) 20:36, 12 January 2015 (UTC)[reply]
I think 10 mins is good. You might consider portable containers, where you can seal each batch of produce in and let it soak in hydrogen peroxide, then discard it when done. Ideally you should be able to cram the container full of produce, and invert it or shake it so it all gets wet. StuRat (talk) 20:38, 12 January 2015 (UTC)[reply]
We're basically talking about a couple hundred of pounds of produce over a period of two hours. The intent is to reuse the solution as much as possible. If we had to discard the solution after each soak then it wouldn't be an economical way of getting rid of the yeast. David Bradley I (talk) 20:55, 12 January 2015 (UTC)[reply]
I was thinking you could pack it in tightly, to limit the amount of solution used. You probably can't pack it in as tightly in an unsealed container, since some produce will float. You need the lid to push it down into the solution. StuRat (talk) 21:03, 12 January 2015 (UTC)[reply]
Another idea: Use some type of rotating wheel to move the produce in and out of the hydrogen peroxide. The same items would be dipped multiple times. This would have the advantage that the last batch would not encounter a much weaker solution. This rotating shoe rack might work (it would have to be rotated manually): Wikipedia:Reference_desk/Archives/Miscellaneous/2014_December_20#What_is_this_cylindrical_device.3F. StuRat (talk) 21:07, 12 January 2015 (UTC)[reply]
Also, if you can "recharge" the solution with a higher concentration of hydrogen peroxide, rather than discarding it, that might be less expensive. There's the cost of the water, but more importantly the remaining potency of the stale batch can be reused then, and you only need to add enough H2O2 to bring it back up to 4%. StuRat (talk) 21:21, 12 January 2015 (UTC)[reply]
Yes, this is ideal, but I have no idea how to figure out if a solution is 4% after I mix it and it decays. If it is too strong then it might bleach the produce, harm the sink, pipes or workers. If it is too weak then it wouldn't be effective. Acetic acid might be a better solution if only for the fact that I can use litmus paper to test it at various times. It is difficult to find out which substances are effective at killing yeast, while being safe for food and workers. Washing with a food-safe artificial fungicide for the yeast would be fine. We just can't use such ingredients in the product itself. David Bradley I (talk) 18:27, 13 January 2015 (UTC)[reply]
Erm, given your phrasing and the scale you're talking about here and the question below, it comes across to me as that you're running some kind of commercial operation. If this is the case, I very much doubt you should be seeking advice about your production process from random strangers on the internet. If this is the case, I would strongly advise you to check the relevant legislation. Waste management for starters, if you're talking about hydrogen peroxide. If my assumption is wrong, please ignore! Fgf10 (talk) 22:43, 12 January 2015 (UTC)[reply]
That's the great thing about hydrogen peroxide, it breaks down into just water and oxygen, so no toxic waste barrels needed. StuRat (talk) 23:37, 12 January 2015 (UTC)[reply]
What are the most economical ways of removing or killing yeast on the surface of produce?
I've been looking into using a hydrogen peroxide soak, but perhaps someone else knows a better way of doing it. I'm basically trying to prevent fermentation, but I can't use any unnatural preservatives in the final product so I'm trying to get rid of the yeast on the produce prior to it being processsed. I'm unaware of any natural preservatives that would prevent fermentation. Thank you. David Bradley I (talk) 20:23, 12 January 2015 (UTC)[reply]
The other method that comes to mind is a UV light, but you would need to rotate the produce so all sides are exposed, and it wouldn't get into hidden folds. With that in mind, your hydrogen peroxide method sounds better, to me. I am of course assuming that cooking or using ionizing radiation (like gamma rays or X-rays) are both out. (The radiation method is inexpensive only on a large scale, and many people won't buy food treated with it.) StuRat (talk) 20:27, 12 January 2015 (UTC)[reply]
Cooking is out, but if hot tap water could kill the yeast then that might be an option. I know it also grows better in a more acidic environment. Does that mean a basic environment could kill it? It might just inhibit growth which wouldn't work at all, but if it could kill yeast then I'm sure there is an economical and safe way of turning large quantifies of water into a mild base. David Bradley I (talk) 20:33, 12 January 2015 (UTC)[reply]
Well, yea, I'm sure bleach would kill it, but that's much worse to work with than hydrogen peroxide. StuRat (talk) 20:35, 12 January 2015 (UTC)[reply]
How about if you plunge the produce into boiling water and then remove it immediately ? StuRat (talk) 20:37, 12 January 2015 (UTC)[reply]
I think that would work, but the people I work for say the labor cost on that would be too high. I've read that sulfur dioxide kills yeast, but I think it might not be legal to wash produce with a solution of it. Potassium sorbate works, but we aren't allowed to use that preservative. David Bradley I (talk) 20:43, 12 January 2015 (UTC)[reply]
That wouldn't be economical either, as you'd need breathing masks for your employees and/or a sealed system with an exhaust fan. StuRat (talk) 20:49, 12 January 2015 (UTC)[reply]
Oh, and don't forget the value of pre-washing it, as that will remove much of the yeast mechanically. The rest will be easier to kill with hydrogen peroxide or some other method. And if it's some type of produce where you can just discard the outer layers, like an onion, even better. StuRat (talk) 20:40, 12 January 2015 (UTC)[reply]
The pre-washing hasn't removed it or removed enough of it. Skinning this produce would be far too labor intensive and thus not economical. David Bradley I (talk) 20:43, 12 January 2015 (UTC)[reply]
David Bradley I, here's a reference: [1] is a detailed discussion of how to sanitize produce. It's published by the US government. A number of different solutions are discussed, including hydrogen peroxide (which is apparently one of the least used commercially, which might be why it's hard to find a source that answers your earlier question about how long it lasts.). Scroll down for a chart comparing the various methods and below that for references to the original studies.Taknaran (talk) 21:20, 12 January 2015 (UTC)[reply]
Yes, I think the issue is that he wants to do it "organically", and many chemicals don't qualify. StuRat (talk) 21:23, 12 January 2015 (UTC)[reply]
Non-organically is fine for the cleaning process. "Natural" preservatives may be okay for the final product. I just haven't found any acceptable ones yet. I have actually looked at that link. Most of the methods aren't approved, don't work well, or don't have much info with regards to killing yeast. One of the reasons I went with hydrogen peroxide was because it was my understanding that Lactobacillus acidophilus killed yeast with hydrogen peroxide. I did notice, in that link, that the waxy coating may actually trap the pathogens in it. Would hydrogen peroxide be able to remove it then? Or is this all in vain? David Bradley I (talk) 18:38, 13 January 2015 (UTC)[reply]
Vinegar (acetic acid) might also work, but I'm thinking that might be more expensive than hydrogen peroxide. StuRat (talk) 21:28, 12 January 2015 (UTC)[reply]
The way that sulfur dioxide is used to kill yeast is to use a solution of potassium metabisulfite. Home winemakers and brewers use it to sterilize their equipment before use. You would need an extraction system of some sort to draw away the sulfur dioxide that's produced but that would probably be the case with most sterilizing agents. I think the main question would be whether any sulfite would be left on the produce after the washing process. There is some information about the use of sulfites here. Richerman(talk) 22:36, 12 January 2015 (UTC)[reply]
Actually that will probably make the problem worse. Yeast grows better in a more acidic environment. Killing it with a wash is most probable with a basic environment. David Bradley I (talk) 18:39, 13 January 2015 (UTC)[reply]
January 13
Can dogs survive in the wild?
I'm trying to convince my idiot friend that evolution is true, and dogs proves it. I tell him to look at all the different kinds of dogs there are, and since these animals were made by humans via artificial selection, that proves that evolution is a fact. But he's dumb, and says that god made them all. So I want to counter that by saying that god couldn't have possible made them because dogs can't survive without humans taking care of them. I'm fairly certain that dogs, even large ones like Great Danes and what not can't survive in the woods without humans taking care of them, but I just want to make sure. Keep in mind, I'm not talking about animals like the dingo which used to be domesticated, but evolved to revert back to their feral state. 69.121.131.137 (talk) 03:09, 13 January 2015 (UTC)[reply]
Unfortunately, they can survive on their own. Many third world cities (without dog catchers) have large stray dog populations. StuRat (talk) 03:30, 13 January 2015 (UTC)[reply]
Artificial selection does not prove that "evolution is true". Whether "God made them" or not depends on how you define "God". ←Baseball BugsWhat's up, Doc?carrots→ 03:31, 13 January 2015 (UTC)[reply]
More importantly, it depends on how you define "made". Evolution and God are not mutually exclusive concepts. --Jayron32 01:26, 14 January 2015 (UTC)[reply]
For a casual proof of evolution, you might point out that the human spine causes all sorts of problems because, in evolutionary terms, we very recently began walking upright, and the spine design has not yet caught up. Specifically, I'd say the spinal chord should not be inside the spine, which leads to pinched nerves. Instead there should be a tough, rubbery cartilage there, and the spinal chord should be more like a notochord. Unfortunately, there's no evolutionary path to lead there, since a spinal chord half inside and half outside the spine is worst of all. If God designed us, he would have presumably done a better job of it. StuRat (talk) 03:34, 13 January 2015 (UTC)[reply]
It isn't worth arguing with someone who doesn't think that human selective breeding is responsible for various breeds of dogs or of livestock. That is agreed even by most creationists. Whether dogs can survive in the wild, as mentioned, depends on the breed. Some can survive in the wild. The original poster is trying the impossible, which is to persuade someone whose mind is made up. It is fortunate that the characterizations made by the OP apply off-wiki, because calling another editor "dumb" or an "idiot" on Wikipedia would be personal attacks. I suggest that the OP, first, tone down his or her rhetoric about someone who isn't here, and, second, stop wasting time trying to reason to someone who isn't listening to reason. Also, creating an account has advantages. Robert McClenon (talk) 03:38, 13 January 2015 (UTC)[reply]
StuRat meant to say they have large populations of stray dogs, not populations of large stray dogs. And no, evil breeds, like the chihuahua, and monsters like the Great Dane cannot survive as such breeds in the wild. Only those dogs that maintain a form close to what God made (the Dingo, the German Shepherd) can survive without human sinfulness. μηδείς (talk) 03:41, 13 January 2015 (UTC)[reply]
It's not going to work. You can show them all the scientific evidence there is. Denialists by the very definition, choose to disregard all evidence that opposes their personal views. If you truly want your friend to seriously consider the viability surrendering their willful ignorance, you'll have to debate the matter on their field of choice - you'll have to make a well thought-out theologically based argument. As an aside, it will be much more difficult to persuade them while you're insulting them, directly or by implication.
Dogs have a good chance of surviving in the wild, since their instinctive ability to hunt and scavenge is genetically hardwired into them. I'm afraid you haven't quite got that one right. Plasmic Physics (talk) 03:46, 13 January 2015 (UTC)[reply]
Your friend is only an "idiot" if he thinks that dog breeds have always been around and is in denial of artificial selection. But even if he knows what artificial selection is, "God" (i.e. natural biological processes) made those breeds. And either way, it doesn't prove anything about evolution. ←Baseball BugsWhat's up, Doc?carrots→ 03:50, 13 January 2015 (UTC)[reply]
I think you're barking up the wrong tree (pun intended) here. If God created all the different breeds of dog, then surely there shouldn't be any more new breeds being recognised? Well guess what: on 1st January, the American Kennel Club recognised 4 new breeds of dog. Did God just wave his hand and say "I guess I'll just create a new dog breed"? Or did some breeders develop a breed over many years? You need to get in touch with the AKC and investigate the history of the new dog breeds, find who their (human) originators are, and get a statement from them. Your friend is not dumb for his blind faith in Creationism, he is dumb because he is wilfully ignorant of real life. --TammyMoet (talk) 09:57, 13 January 2015 (UTC)[reply]
I'm with the above answers but I'll leave an additional note that whatever your friend may have said, I think you'll find creationists more commonly claim that artificial breedingdoesn't produce new species, the claimed microevolution vs macroevolution distinction [2], (all wrong in many ways, as explained in our articiles), and that artificial breeding is simply "destroying information" [3] so it isn't surprising if some dogs would have poor survival were it not for humans. To be clear, these are poor arguments with many holes, I mean creationists come up with silly things like the alleged perfection of the banana (which I think even the inventor acknowledges was a dumb argument), but the point is you aren't likely to get anywhere by arguing whether or not dogs can survive in the wild (which isn't to say you'd get anywhere by pointing our more substanial flaws). Nil Einne (talk) 11:22, 13 January 2015 (UTC)[reply]
BTW, I would add even if your friend wants to suggest all the different dog breeds were made by god, their likely argument in response to any of your claims that they can't survive in the wild would simply be that that's how god created them intentionally because they were intended to be companions to humans, and they weren't intended to survive in the wild, similar to the banana argument, or many other things like that. Of course, as mentioned by others, it seems difficult to sustain the idea that all breeds were created by god, since we're creating new ones, so ultimately it seems likely your friend will have to accept that some breeds were basically created by humans, even if they're then likely to fall back on to other arguments like those I highlighted. (You can also get in to arguments about why god created dogs breeds primarily intended to attack other animals or even humans, when god didn't want any of that but that's not an argument unique to dogs. And in any case, it's likely creationists will suggest that these dog breeds were only created by god after the downfall of Eden or he created them because he knew it was going to happen even if he didn't want to or even simply they weren't like that before Eden despite having the teeth, build etc suited to that purpose and it's not god's fault it all changed after Eden despite him designing them in such a way they seemed well suited to change when humans broke Eden [4].) Nil Einne (talk) 17:22, 13 January 2015 (UTC)[reply]
To begin with, artificial selection isn't really quite the same thing as natural selection after all. The problem is that the human breeder eagerly picks out genes of large effect that have many pleiotropic consequences, which won't actually be used for evolution in the wild. (This effect is stronger in a lab setting, e.g. mutating fruit flies with radiation, where huge deletions of the genome may be brought about that practically never happen in normal evolution; some of the confusion over this ties into the "hopeful monster" concept) The result is that the human-made breeds tend to be more sickly in ways that a slow, sane pace of natural selection wouldn't have caused. Now to be sure the dogs, if released to the wild, should still survive; eventually they will ditch the worst large-effect mutations and, if they still need the trait the breeder selected for, find small effect mutations that affect it more precisely.
Now as to your argument, presumably your friend recognizes that there are breeds of dogs that exist now that never existed in the past; yet he says God created them. That means that he recognizes that something created by God doesn't have to date back to Noah's ark; God is allowed to have a plan for something to appear. Now if that is so, then you and he are arguing over very little, because no scientist will argue that something will evolve unless it is physically possible and indeed is a pretty good solution to the ecological problems of its niche. In religious terms, unless God planned it. Wnt (talk) 14:49, 13 January 2015 (UTC)[reply]
I don't think your argument about dogs is a good one. Evolution requires three things: One is that living things inherit characteristics from their parents - another is that natural selection favors plants and animals that are better able to reproduce than others, the third thing is that the process of inheritance makes mistakes (albeit rather rarely). The situation with dogs shows that dogs inherit characteristics from their parents - a poodle plus another poodle results in a whole lot of poodles. But it doesn't demonstrate that dogs that are better suited to their environment reproduce better - to the contrary. It's unlikely that a highly specialized pedigree dog will have fewer defects than a 'mutt'. Inbreeding has caused all sorts of defects to develop in pedigree dogs - and the very "best" of them are far more likely to have a hard time reproducing than a dog that's some random mix of many breeds. Also, the "selection" process isn't "natural selection" - it's clearly human intervention...which is almost like an "intelligent designer" at work.
So what you need is a much better example. There are two examples that I think are compelling - but they both take a bit of investigation. If your friend is simply dismissive of your ideas, then you're unlikely to get him/her to sit still long enough to be convinced.
Peppered moth evolution is a classic. These moths were colored white with little black speckles to match the lichen and tree bark in rural England. Up until around 1811, there had been no examples of these moths in any other patterns. But gradually, butterfly collectors noticed an increasing number of black peppered moths showing up. It turns out that the smoke and pollution from industry in the areas where the moths lived was coating the trees with dark soot. Within a decade or two, almost all of the moths were black...then, when the Clean Air laws were passed and the amount of smoke in the air decreased spectacularly, the black moths became rarer and rarer until today, you can't find a single one. Clearly the moths were evolving to be better camoflaged against the trees - and then evolved back again when lighter colors worked better.
The Recurrent laryngeal nerve in mammals - and especially in the giraffe is a fascinating demonstration. It seems that the vocal chords (the larynx) evolved from a greatly distorted gill from each side of some primordial fish. The nerves going to each of the two gills on that original fish had to bypass the arteries going to the heart - the right one went over the artery, the left one, under...and modern fish of all species are just like that. No big deal if you're a fish. But as the two gills moved closer together over millions of years of evolution - one nerve was forced to loop past the heart. So in a giraffe (or a human, or almost any other animal) - the nerves controlling the right side of the larynx go directly from brain, down the neck for a short distance to the larynx...but the left side nerve goes from the brain, all the way down to the heart, around that artery, then all the way back UP the neck to the larynx. In humans, this is no big deal - but in a giraffe, it means that one nerve is about 15 feet longer than the other. Since electrical signals from the brain have to travel 15 feet further to get to the left of the larynx than to the right, this makes it almost impossible for the poor giraffe to coordinate the muscles in the larynx. This is why giraffes are almost the only mammals that don't make vocalizations. Now, your friend needs to explain why god decided that all animals have to have this nerve looped around that artery...it makes no sense whatever. If "God" designed the giraffe, he was not the "intelligent designer" but rather the "bloody stupid idiotic designer". Sure, you might argue, he may have decided that giraffes don't need to make a noise - but then why bother having a larynx - let alone bothering to connect up a nerve in such a totally crazy way? Why would ALL air-breathing animals from dinosaurs, to humans and giraffes have such an unbelievably stupid design? Any rational design would have both nerves going the short way to the larynx...and if they did, then the spectacular song of the male giraffe during gentle courtship of his mate would grace the plains of Africa as testimony to God's Greatness...but no. If hard-pressed, a giraffe can make a sound that's been described as a cross between a bleat and a cough. God did not make the giraffe...it's just not credible...it evolved from a fish - and when you look at the evidence with an open mind, there is really no other conclusion.
These are great examples...there are many, many more. Why do some people have lactose intolerance? Why do some people inherit sickle cell anemia? Why do bacteria develop immunity to drugs in hospitals? Why do rats in New York have genetic immunity to Warfarin? Why do rabbits in Australia have genetic immunity to mixamatosis? All of these things are clear demonstrations of evolution happening on human timescales. There are several long-running experiments where bacteria are forced to evolve by changing their living conditions - and they change over time, in exactly the way that evolution predicts.
It's actually very hard to imagine how evolution might NOT occur. If the shape and nature of an animal or plant derives from it's DNA (which is hard to deny) - and if DNA is replicated from parent to offspring (also, hard to deny) - and there are occasional errors in that copying process (again, hard to deny) - then occasionally, a small variation will occur in a plant or animal. If that variation makes it reproduce a little more efficiently than the others of it's species, then its genes will (inevitably) be copied into more of the next generation than the original genes - and gradually, more an more of the members of that species will carry that gene. Eventually, every plant or animal in that species will have the new and improved gene. Evolution has happened. Do that enough times and you get human beings from fish.
We can even see evolution happening in systems that are not biological in nature. If a song or a TV show or a movie becomes successful through some clever innovation, other makers will tend to copy that idea. Making a movie is expensive - and going with some crazy new idea is dangerous - so most of the time, they make variations on what worked before. Movies that embody themes that fit the times make more money than those that don't - and that allows their makers to make more of them. Hence you get huge waves of movie genres (cowboy films, film noire, disaster movies, etc) that come and go as the environment favors one or the other. All of the essentials of evolution are there...movies that 'work' tend to produce 'offspring' that are broadly similar. Movies that do well in the box-office earn more money and therefore inspire more copy-cats. Movies that do badly are dropped and produce no copy-cats. Over time, movies adapt to fit the viewer preferences. You can see the same things happening in a huge range of fields. Whenever there is copying with variations and pressure for things to do well or do badly, for reasons that the makers don't really understand - then evolution occurs. Why is it that almost all cars come in silver or black - but almost none in purple? I'm pretty sure it's evolution.
If you absolutely MUST stick with the dog thing. Point to the Labradoodle. A Labradoodle is a cross between a labrador and a poodle. There are breeders all around the world that 'make' labradoodles by crossing parent dogs of those two breeds. But, you can also take two labradoodle and mate them - and you get another labradoodle. Clearly, god didn't make the labradoodle. There was no 'labradoodle' breed before 1955...although presumably an occasional accidental mating of a labradore and a poodle would have happened, we didn't have a 'breed' of these animals that you can point to and say "Oh - look! A labradoodle". At this point, your friend either has to admit that god didn't design the labradoodle - we humans can make a labradoodle where there was no labradoodle before. We can do it anytime we want. Labradoodles are a stable, well-recognized breed. Of course your friend is at liberty to claim that labradoodles aren't a "real" breed...so they don't count. But then we have to look at other kinds of dog that he does claim are breeds that were made by god. Maybe God made the Labrador? Sadly, no. We know that all labradors are descended from two very specific dogs...and, remarkably, we even know their names! "Avon" and "Ned". These dogs (which were known to be good gun dogs - but which were definitely not "labradors") were given by the Earl of Malmesbury to assist the Duke of Buccleuch's breeding program in the 1880s. Before that, there were no Labradors...so we know for sure that labradors are "the work of man" - just like labradoodles. If you go through all of the Wikipedia pages for various dog breeds, you'll find some (like the Labradoodle and the Labrador) who's origins are very well known and documented - and others (like the poodle) where we know only that the first known examples were around on some particular date.
So I suppose that your friend (if a rational, thinking person) would be forced to admit that Labradoodles were definitely NOT created by God, and more surprisingly, neither were Labradors. Of course (s)he may cling to the view that poodles are a divine creation...but at least one is forced to segment the world of dogs into the originally-created-by-God set - and the set that were created by man. Now you have to ask whether some of the dogs in the "made by god" set really belong in the "made by humans" pile? In the end, the only thing we really can deduce from human history is that the wolf was not created by man...but most dog breeds were.
Sadly, this doesn't get you any closer to an argument about evolution. It does demonstrate that mankind is capable of producing new kinds of dogs - which I suppose breaks the doctrine that 100% of all species were made by God in the Garden of Eden. There were no labradoodles in Eden. SteveBaker (talk) 17:19, 13 January 2015 (UTC)[reply]
The dangers of messing with labradoodles.
Actually, if you cross a Lab and a Poodle you will get a Labradoodle. But if you cross a Labradoodle and a Labradoodle you can get everything from a Lab to a Poodle to a Dabraloodle to a Poobradaddle, to a Cobrababble, to an Oprahbubble, to an Oobracadoobra. From there it's just one small misstep to a Scooby Doo or a Deborah Messing. See dihybrid cross. μηδείς (talk) 19:00, 13 January 2015 (UTC)[reply]
My wife and I went to a breeder with the idea to get one for a pet, they said that they used labradoodles to parent their puppies. This is confirmed in Labradoodle#Types. (In the end, we decided that labradoodles are not such great animals after all). SteveBaker (talk) 19:45, 13 January 2015 (UTC)[reply]
Yes, if he's paying close attention, culling (i.e., selling) the less true-to-form puppies, and only breeding the ones with traits he wants, he'll eventually start getting mostly passable labradoodles. But they won't breed true unless it turns out that all the desirable and defining traits are homozygous. μηδείς (talk) 20:10, 13 January 2015 (UTC)[reply]
SInce people have been breeding labradoodles for close to 60 years, and aggressively so for 20 years - at maybe 2 to 3 years per generation, they're likely to have eliminated almost all risk of throwbacks. But they certainly don't yet have the complete uniformity of more established breeds - and already they're getting the inevitable genetic diseases starting to pop up. However, the original point remains - we have labradoodles, they (mostly) breed true - and god didn't create them in the Garden of Eden. Either humans created this breed or we have no free will. Pick either one! QED. SteveBaker (talk) 20:25, 13 January 2015 (UTC)[reply]
We're really getting into philosophy more than science here. A pointier version of this argument came up in the U.S. a year or so ago when Richard Mourdock was lambasted for saying that pregnancies following rape were part of God's plan.[5] Now I'm normally all for roasting a Republican, but this struck me as unfair, because the alternative position is to single out the kid in the class who was produced by a rape, point your finger at him and say "you are not part of God's plan". We should think a bit more about what God's plan actually means first! I think a good analogy is with the putatively endless set of contigency plans come up with by military organizations like the U.S. Army. One kind of assumes that if Belgium ever decides to invade Virginia Beach, they have a plan for it. My understanding is that theologians try to accept both that there is a divine plan for everything, even after all the weird events that have happened in history, and that there is free will, which makes for some creative logic, but so long as they believe God is omniscient and all-powerful it is nothing they can't handle. The bottom line though is that there should be no litmus test for religion set up at a security counter at the classroom door - everyone is capable of learning what evolution predicts in terms of what we measure by natural means, regardless of what they think the theology behind it is; they should be able to recognize it is practically useful without having to believe any religious assertion that our lives are unplanned, random, meaningless, or insignificant. Wnt (talk) 18:27, 13 January 2015 (UTC)[reply]
The problem being that if you accept that all things that happen are a part of god's plan then you wave goodbye to free will because you're saying that the rapist didn't have a free choice to rape or not - he was merely being constrained to follow god's plan in the creation of this child whom you're claiming is indeed a part of the plan. That's a logical possibility, obviously - but the absence of free will is definitely contrary to most religious thinking - and would cause severe upset in society if it were true. If the rapist is able to make a totally free choice - then one of those options has to be to veer away from any "plan" - and now you're forced to point to the kid in class and tell him that he's not a part of the plan. Neither of those options are particularly appealing!
Furthermore, if everything that happens is a part of the plan - then god's plan boils down to the universe slavishly following the laws of physics - and if that happens then you don't need the existence of a god to explain things that happen because the laws of physics do a perfectly fine job of doing that. Then the existence of god boils down to a gross violation of Occams Razor...which is fine if you like that kind of thing...but is what ultimately leads me to scrap the entire silly idea. SteveBaker (talk) 20:03, 13 January 2015 (UTC)[reply]
Well, ever see a Choose Your Own Adventure book? You have many choices to make, yet every one brings you to some page written by the author of the book. I'm not saying that's way it is - there's a huge variety of philosophy possible here - but this illustrates how things can be neither random nor predetermined, and besides, if mankind is created in the Creator's image, it's always in our creative works that we'll find the most useful metaphors for understanding. Nobody is denying that, so far as we can observe, the laws of physics seem to be valid. But they always proceed from some starting point. Is it really Occam's Razor-able that that starting point was some simple set of starting conditions "at" the Big Bang, even though it seems like the complexity of the events in the universe expands without limit the closer you look back toward it, and we know nothing about it? Even though we then turn around and use the anthropic principle - itself more or less a form of creationism! - to say that somehow the "right" starting conditions were picked? What if the starting conditions aren't set at infinity in an uncaring way for the random development of interesting life someday, but right here, right now, by some God who actually sees and cares about us? It's all very mysterious, but beware of taking some (atheistic) religious assumption, dressing it up in sciencey garb and hiding it in the part of the theory of the cosmos that we don't actually know anything about. Wnt (talk) 20:24, 13 January 2015 (UTC)[reply]
Well, yes - let's take your analogy of the 'choose your own adventure' book. You're trying to tell the kid in the classroom that he's a part of the plan - but it's inconceivable that any other path than the rape of his mother would result in him being there. In order to be who he is on that day with that specific birthday, it pretty much had to be the free will of the rapist that caused him to be there, on that day, with that eye and hair color and that birthday with a mother who was 15 years old when he was born, etc, etc. There just aren't too many other routes through the 'choose your own adventure' book that would lead to that. 99.999999% of the other ways that free will could have directed us through the book would result in him not existing. Let's face it, a free-will decision by Attilla the Hun would have resulted in a large fraction of the population of the world not existing...and Og-the-caveman could have picked a different wife and NONE of us would exist. So this is a REALLY large book - and hardly any of the pages have you or I on them.
So what you have to imagine is that this one particular path through the book included this kid - but that there were many other paths ("plans of God") that would have resulted in him never existing...yet you're still going to tell him that he's a part of god's plan...although technically, you're saying "You're a part of plan number 153920423 of 1032534070734095738087230498 plans that god made but which didn't play out." Taken to a very reasonable extreme, the location of the pencil on my desk right now is also a part of God's Plan - and my putting it there as an act of free will was just a page in this adventure book-style plan that included me deciding to put the pencil someplace else - 1/100th of a millimeter to the left, or to toss it in the trash, eat it...whatever. This means that this plan book, ultimately resembles the "many worlds hypothesis" - where every possible bifurcation of reality at the quantum level results in another whole section of the "choose your own adventure" book. That's fine - but again, we've arrived at a place where the laws of physics suffice to explain all of this - and your belief in god once again rests on denying free will, or denying Occam's Razor. That's a very slippery path because then I have to ask why you'd choose this particular unlikely (but possible) denial of the razor rather than the near infinity of others...such as that SpongeBob SquarePants actually created the universe. SteveBaker (talk) 20:52, 13 January 2015 (UTC)[reply]
I can't really say that idea is right (it is chosen more as a counterexample, after all) but when one considers the total number of 'plans' that could exist, not merely in infinity, but in an infinity of cosmoi, it doesn't matter how many numbered plans exist; each is still a truly unique inspiration. But bear in mind two things -- first, that since the laws of physics are time-reversible, each moment can have multiple pasts as well as multiple futures; and also, that they are nondeterministic, which means that it is possible that our fate might be nudged this way and that rather than proceeding along a random vector. I think it is worth considering that our consciousness might exist with at least two dimensions of time - one in which the normal laws of physics operate, and one reflecting the progressive work by which God steadily revises and perfects the universe. In keeping with accounts that "every tear will be wiped away", perhaps people pass into parallel worlds, keeping the virtues that they have attained by resisting evil, yet seeing all that evil pass from mind, and indeed, never even having been real at all, in some sense. So while I mentioned one fixed 'initial condition' in the present above, actually I mean that there may be multiple initial conditions, with the time between them interpolated to fit using non-deterministic physics, so that it is possible for the author of the universe, with our input, to steadily revise the entire plot - past, present, and future - within his own dimension of time rather than the time frame that flows within the context of the story.
Now we've really gotten far off the point with this, but for this question: it's possible that God had in mind the form of a certain kind of poodle from a previous revision of the cosmos, or from some Eden (next door to "the" number line, and the place where the six regular polytopes that can exist in four dimensions might be found) or from some other sort of plan. It might not be without significance; it might not be random; we know it's not truly all our choice because we can't just breed up anything at all. And the same is true of the species we share the planet with. Of course, it will be so much easier to see if ever mankind were to visualize a foreign planet with its own kind of life, because I have little doubt that that world will have its own trees, which we may even be tempted to give familiar names, and its own fish, and countless other organisms we recognize, as well of course as a few residents of Eden who have not yet been spotted on Earth (but give our biologists time...) Wnt (talk) 22:18, 13 January 2015 (UTC)[reply]
@SteveBaker: It doesn't look like your notion of a mute giraffe checks out. Apparently they communicate largely in infrasound, which is inaudible to many people.[6][7] Even those people distinguish a variety of vocalizations though, including "alarm snort", "bleating or mewing" (calves), "roaring bellow" (females seeking young), "raucous cough" (males courting), "moaning, snoring, hissing, and flutelike sounds". [8] And after all... if that long, long recurrent nerve didn't work, why wouldn't it have degenerated into some vestige? Wnt (talk) 16:16, 14 January 2015 (UTC)[reply]
I generally recommend that you actually read the references that you post. If you had, you'd know that giraffes make infrasound noises only by physically moving their necks around to force air through their nostrils - which is where that sound actually comes from. The fact that they have to go to all the trouble to throw their necks around to make noises is evidence that they can't use their vocal cords. Kinda proves what I'm saying. Other animals such as elephants and okapi that use infrasound for long distance communications still use conventional vocalization for short range work...but the giraffe doesn't do that. The nerve hasn't degenerated because the necessary genetic changes to make it degenerate would have to have some measurable impact on reproductive capability. Evolution isn't a perfect mechanism - it doesn't always get rid of unnecessary things. But regardless of whether or what noises a giraffe makes - why would an intelligent designer route one of the two nerves by such an insanely circuitous path? That would not be an "intelligent designer" that would be a "bloody stupid designer". SteveBaker (talk) 18:29, 14 January 2015 (UTC)[reply]
From what I'm reading the infrasound does come from the vocal cords. And the use of infrasound is shared with the okapi, with a short neck, as a way to avoid predators. [9] (Which is sort of curious because what on the savannah will mess with an adult giraffe? But I guess once evolved there was no reason to lose it) My purpose here is not to doubt that giraffes evolved, nor to deny that there is a clear evolutionary reason for the strange structure; but only to quibble on whether giraffes can vocalize and to mention that it seems silly to harp on it being such a "stupid" plan when really there's not much obviously wrong with it. Wnt (talk) 19:01, 14 January 2015 (UTC)[reply]
What is the difference between analgesic and sedation?
Trying to explain would be relatively painless, but might put you to sleep, so read analgesic and sedative and decide for yourself. StuRat (talk) 05:12, 13 January 2015 (UTC)[reply]
Briefly, analgesics are intended for use as painkillers. Sedatives are to reduce anxiety, irritability - generally to calm the user. In many cases, analgesics are also sedatives and vice-versa - so there is considerable overlap. A mild sedative might not directly act to reduce pain, but may reduce the anxiety and stress caused by the pain and thereby make it more bearable. SteveBaker (talk) 16:04, 13 January 2015 (UTC)[reply]
It's easier to get the pain-relieving effects of a sedative without drugs than it is to mimic an analgesic. There's a section on "natural" inhibition of cyclooxygenase, but those are still chemicals you need to ingest. The key to relaxation is already in our head. Certain things just help (or aim to help) us reach it easily. InedibleHulk(talk) 01:39, January 14, 2015 (UTC)
Professional laptops
Why do many gamers and professionals, such as graphics designers or engineers, seem to use big, bulky, heavy laptops in this day of thin and portable devices? 194.66.246.5 (talk) 14:43, 13 January 2015 (UTC)[reply]
There's really no substitute for a large screen, which allows you to see details you just can't make out on a tiny screen, even at the same resolution. Similarly, a full-sized keyboard allows for faster entry than a compact keyboard. And what are the advantages of being small ? It won't fit in your pocket, in any case, so then it's just a question of whether the weight fatigues you as you carry it. Most people can carry several pounds indefinitely without becoming fatigued. StuRat (talk) 14:48, 13 January 2015 (UTC)[reply]
Some of the laptops I see people using don't look portable though. It looks silly for example opening it up in a coffee shop due to its size. 194.66.246.5 (talk) 15:03, 13 January 2015 (UTC)[reply]
Well, obviously they are portable, if they were carried into a coffee shop. The more general question for any device is "How small is too small ?". Traditionally, technology limited how small we could make things, but now we are getting to the point where the technology allows us to make something that is so small as to be unusable for other reasons. Larger cell phones (especially flip phones), for example, allow a microphone by the mouth and a speaker by the ear, which makes for much better communication. Here the upper limit is probably that it needs to fit in a pocket, but there's not much point in making it much smaller. You also want to be able to hit all the buttons by hand, not have to use a stylus, and with a full QWERTY keyboard there are a lot of buttons, so the space adds up. And people want a longer battery life for any device, which requires bigger batteries. StuRat (talk) 15:21, 13 January 2015 (UTC)[reply]
I don't know exactly what models you're thinking of, but people doing graphics-intensive work are surely going to want a large display. They may also want more options for what can be attached or inserted, such as an Ethernet connection, USB, and a Blu-ray disc. Jc3s5h (talk) 14:51, 13 January 2015 (UTC)[reply]
So are all these portable laptops these days which manufacturers claim are ultra thin and light made at the expense of performance? 194.66.246.5 (talk) 15:00, 13 January 2015 (UTC)[reply]
In some respects, yes. Certainly you can pack twice as much into a laptop twice the size. But eventually we will hit a point where you can pack more than enough memory, storage space, battery etc., into as small of a space as you would want. Then we hit those ergonomics limits. There are some possible workarounds, like a roll-up keyboard and screen, to make it more portable without being unusably small. StuRat (talk) 15:31, 13 January 2015 (UTC)[reply]
I'm one of those people - I write C++ realtime 3D graphics code for a living (I'm currently doing "augmented reality" stuff). I don't often haul any of my laptops around with me (I have 4 of them!) - but when I do, it's because I need the power of a decent computer - otherwise I'd use a tablet or even just my phone with a folding bluetooth keyboard. Those little folding keyboards are surprisingly comfortable to type on. So the need for a really good laptop is a combination of wanting a full-performance GPU, a good sized screen with really good back-lighting, a high-horsepower CPU and a ton of memory + disk space. The super-thin computers tend to have poorer everything.
It would be different if I was some kind of executive who needs to be able to do email and display powerpoints in airport lounges...and not much else. When you need your laptop to compile a million lines of C++ code - or to debug subtle graphics glitches - you really need something with some 'oomph'. All of that horsepower also makes the laptop consume a ton of energy - so you need chunkier batteries and active cooling - all of which adds considerably to the weight and thickness. The large screen and decent backlight makes that even worse. But since I'm only using it when I absolutely need that much power (and when I absolutely can't do it at home or in my office) - then that's the best option.
In addition to my big Dell laptop, I do actually have an HP "Chromebook" - which essentially runs a browser and nothing else, has very little local storage and doesn't even have a hard drive, and an old "netbook" - which I like because it's physically tiny - but which has been supplanted by the Chromebook. The battery life on the chromebook is incredible and it's very lightweight. That's great for taking on vacation and leaving in the car for occasional use. It's better than a phone or tablet - but useless as a general purpose computer. My big-assed Dell laptop is good for heavy-duty work - but I wouldn't want to lug it around with me everywhere. My day job bought me an Apple laptop - it's like a piece of jewelry - pretty to look at, pleasant to the touch, fancy magnetic power cord (why?!) - but falls between the Dell laptop and the Chromebook for all practical purposes. When I need horsepower, it's inadequate, when I just need to surf the web, it's over-kill. There never seems to be a time when I actually need it. So it collects dust until I need to test something on it (and 99% of the time when I do the battery in that super-sexxy Apple mouse needs to be replaced!).
So for me, it's a matter of picking the right tool for the job. Most of the time, I use a deskside computer with three large monitors and a really good ergonomic keyboard. My one less-than-ergonomic peripheral is my MINI Cooper-shaped mouse (it has brake lights that light up when you stop moving the mouse!)...it's actually much more sensitive than most mice and I love the subtle detents in the scroll wheel.
As a counterpoint, I did all the computations an simulations for my PhD. dissertation on a tiny 13" Powerbook laptop. As you know, actual computational complexity isn't always closely related to the complexity of the work. So, while that computer would have choked up a bit on large compile jobs, it was more than enough for my scientific computing needs at the time. The take-home point for the OP is that people have different use cases, and for the foreseeable future computational power will trade off with weight and battery life. Also not all users act rationally, and I suspect many area coffee shop workers like to show off their big, heavy, high powered laptops, even if another machine could suffice :) SemanticMantis (talk) 16:09, 13 January 2015 (UTC)[reply]
What about engineers? Don't they often require both portability and high powered computers? Since they use specialist software but also travel a lot to make presentations etc. So do they have a portable laptop and a high power one? 194.66.246.5 (talk) 16:20, 13 January 2015 (UTC)[reply]
Engineers are a very diverse group, so I don't think we can talk about all of them at once. Some do a lot of presentations, some never do. Some engineers need computational power, some don't. For example, my brother in law uses a normal modern (thin-ish, light-ish) 15" Dell laptop for his job as an on-site industrial engineer - he runs in-house software but has never mentioned performance issues. But a mechanical engineer using finite element methods to model complex material deformation via partial differential equations might need more computational power. That's the point I was trying to make above - in the modern era, even rather sophisticated modeling and computation can sometimes be relatively computationally inexpensive. Even a very sleek and small modern Macbook Air can do computations in minutes that would have taken days on older desktops. So don't confuse "complicated, hard to understand work" with "work that requires very high performance computers by modern standards"
Going the other way, it's really computationally hard to factor large numbers into primes, but conceptually it's very easy. On the other hand, the fast fourier transform requires a lot of mathematical background to understand, but runs very quickly and is used in many engineering applications. SemanticMantis (talk) 16:37, 13 January 2015 (UTC)[reply]
I typically run 3 or 4 solvers in parallel (they are single threaded) on my vehicle dynamics simulations, but I have found the actual speed of execution of a given job is only vaguely related to the headline numbers of a given computer, things like drive I/O speeds are often as important. I use a laptop for most of my data crunching because I occasionally need to use it in cars and meetings. For a given thread it is slightly faster than my engineering workstation, but that can handle 8 threads at a time, the laptop only 4, and it has much more storage. Greglocock (talk) 19:53, 13 January 2015 (UTC)[reply]
I'm not sure exactly which laptops you don't think are "portable". Even the big ones are really not that heavy. Unless you have physical challenges or are planning on going hiking with it, I'm not sure what the problem is. Cowboy up.
I did get a smaller laptop for my last trip to Europe; it is more convenient to carry than my older 17'' model (which however is much nicer to look at pictures on). So sure, there's a tradeoff, but it's not really "portability". They're all portable. --Trovatore (talk) 16:45, 13 January 2015 (UTC)[reply]
From Portable computer, these images depict computers that are technically portable but many of us would not wish to carry around :) SemanticMantis (talk) 19:33, 13 January 2015 (UTC)[reply]
There is certainly no "one-size-fits-all" rule here.
These days, presentations are often uploaded to the Internet - so when I turn up at some customer's site to do a presentation, I just tell them the URL and have them bring it up on their conference room display screen. So the need to use a computer of any kind is kinda limited. If I'm concerned that my host might not have an internet-connected TV, I also carry a "chromecast" gizmo - which is no bigger than a memory stick and can be plugged into any TV with an HDMI port...I can use my phone to instruct it to grab video off the Internet and display it. Using a laptop to do this is definitely overkill.
However, if I'm called upon to do a demo of some piece of software, something that can't be done with video, still images and text - then I'll very often have to figure out how to connect my laptop to whatever in-house video system is present - and this is *ALWAYS* a nightmare!
Mostly, my computer usage splits into stuff that's on the web (for which my phone or tablet (plus bluetooth keyboard) may just barely suffice - but the HP Chromebook is perfect) and stuff that's heavy programming/documenting work. For the latter, I get massive productivity benefits from having multiple high-resolution screens, so a desktop computer is the only answer. My large laptop is only useful for those super-rare circumstances where I have a lot of heavy work to do, yet somehow can't be at my desk either at home or in the office...and even then, I increasingly remote-login to a server someplace to do heavy computational stuff.
I used to one of the people with a power laptop to manage complex scientific codes. However, my code outgrew what any laptop can offer, so now I either run on uber workstations (16 cores, 256 GB of RAM) or on computer clusters. As a result of that transition, I now do most work via remote login, so I no longer need a big laptop. Hence, a light-weight laptop plus a fast internet connection is now fine. It really is about the use cases and how much power you need with you to do your work. Some people want (or need) very powerful laptops and other people have found ways to get things done with less and hence may opt for light-weight, less powerful configurations. Dragons flight (talk) 19:49, 13 January 2015 (UTC)[reply]
For me, the nicest thing about large laptops is precisely that they're large. The keyboard is easier to type on; the display is easier to view. Whether that's worth the extra weight depends on how heavily you're using it, and how far you're planning to walk.
Of course at home, I use an external keyboard, mouse, and monitor, so the form factor of the laptop itself doesn't matter much. --Trovatore (talk) 19:54, 13 January 2015 (UTC)[reply]
Apollo mission photos left on the moon.
I was reading today that it's more or less certain that all of the US flags that were left on the moon by the Apollo landing crews will have been bleached white by the sun. (Evidently the flags were a last-minute addition to the mission and were bought at a local branch of Sears without consideration of dye stability in intense sunlight!)...I find this kinda ironic...but that's another matter.
Anyway - this made me wonder. Most of the astronauts brought photos of their families or dead friends, etc to leave on the moon as a perpetual memorial to them. It seems likely to me that those too may have been bleached white.
How do the materials in photographs from the 1960's and 70's survive in that kind of intense UV light? At least a couple of the photos seem to be color pictures...and I know that color photos I have from the 1960's have faded quite a bit - despite being kept mostly in the dark. It doesn't look like the pictures were in any way special...like not special dyes used to make them or anything.
Did all of those treasured pictures wind up as white cardboard squares?
I'd think yes, they would be bleached white if left exposed to the Sun. But perhaps they buried them under a layer of Moon dust, or even if not intentionally done, the dust generated when the lander took off might have coated them with a thick enough layer to block UV. StuRat (talk) 15:34, 13 January 2015 (UTC)[reply]
Ignoring launch events "It would take 1,000 years for a layer of moon dust about a millimeter (0.04 inches) thick to accumulate" [10]. I'm not sure how much the launch would have generated, but unless that was enough by itself the natural dusting process wouldn't provide enough protection. SemanticMantis (talk) 15:50, 13 January 2015 (UTC)[reply]
Have you done any research on the insolation of the moon across the spectrum? It might be useful to be able to express irradiation on the moon in terms of how much more or less light hits the surface at each wavelength, compared to the Earth. The other thing would be to narrow down what type of printing technology was likely to have been used. E.g. a polaroid may well fade much more quickly than a Kodachrome print. Also they may have put them in protective sleeves, as mentioned at Photograph#Polyester_enclosures. The article mentions atmospheric protection, but also "Polyester contains a benzene ring that absorbs UV light" (https://en.wikipedia.org/wiki/Sun_protective_clothing) For Earth-bound photos, much of the degradation is due to reactions with the atmosphere (e.g. humidity), in addition to light. Obviously the moon has less humidity fluctuation so that might help to counteract any increase in UV exposure. SemanticMantis (talk) 15:50, 13 January 2015 (UTC)[reply]
Oops, thanks! I wanted to link to a WP article about the various methods of making prints from film but all I can see at present is the large List_of_photographic_processes. SemanticMantis (talk) 16:13, 13 January 2015 (UTC)[reply]
Images on Voyager Golden Record
What is the image format used to encode the black-and-white and color images on the Voyager Golden Record? 20.137.2.50 (talk) 17:12, 13 January 2015 (UTC)[reply]
It's not really an "image format" in the sense of "JPEG" or something. It's a monochrome raster image (such as would be transmitted to a TV set back in the days of black and white analog television) - but for some reason they scaned the images vertically instead of horizontally. So the horizontal resolution of the images are 512 lines but the vertical resolution is determined only by the quality of the recording and playback equipment - but probably less than 512 "pixels" per scanline because that explains why they'd use vertical scanning to improve the overall resolution of non-square images. The amplitude of the wiggles in the grooves of the record are the brightness of the image. It's about as simple as it could possibly be, given the (essentially analog) standards of the day. They even included a stylus with the record to allow the disk to be read more easily. Color images are encoded with three consecutive images in red, green and blue. SteveBaker (talk) 19:17, 13 January 2015 (UTC)[reply]
Dumb questions? Science at school never explained certain stuff to me.
1) Why do we count seconds and minutes up 60. Why not have 100 seconds in a minute. And 100 minutes in an hour. It would make time math so much more simple. 2400 minutes in a day.
2) And also, why do helicopters keep their relative position whilst hovering. Since the earth is spinning, shouldn't the ground be moving underneath it. Likewise, what if you were travelling in a plane at the speed of earths rotation. Shouldn't this enable you to hover and remain in once place.
3) And also, what if I was travelling 1mph below the speed of sound and a threw myself forward 2 mph. Would that cause a sonic boom, would I be technically travelling faster than the speed of sound. Again likewise, isn't that cute, sexy cabin stewardess pushing that trolley up the aisle moving faster than the plane she's travelling on. Wow. — Preceding unsigned comment added by 82.19.76.217 (talk) 17:26, 13 January 2015 (UTC)[reply]
So, this is what happens to the youth of a country when they don't have college football championships? See hour, minute, second, flight in air versus orbit in vacuum, and relativity and sonic boom in light of relativity. μηδείς (talk) 18:37, 13 January 2015 (UTC)[reply]
(I added numbers):
1) The base 60 system is left over, I believe, from Babylonian times. They wanted a number that's divisible by a lot of integers, and 60 is divisible by every integer up to 6, while 100 isn't even divisible by 3. This was before fractions or decimals were much used, so they liked keeping things as integers, whenever possible. So, if you had 6 people taking shifts using pedals to drive a pottery wheel, each would have a 10 minute shift, nice and easy. During the French Revolution, they tried to introduce metric time, but it was just too different.
2) The helicopter and plane all move by displacing air, so their base speed is that of the air, and then they either add or subtract from that speed. See air speed and ground speed, which can vary dramatically, say if the plane is in a jet stream. The air moves with the Earth, ignoring wind, because the same forces which started the Earth spinning also did the same thing to the atmosphere, and friction with the ground ensures that the atmosphere moves more or less at the same speed as the rest of the Earth.
3) A sonic boom is caused by the relative velocity of two objects, not the absolute speed (if there is such a thing). So, you won't create a sonic boom on the plane, but I suppose if you were crazy enough to have an open window at that speed and yelled as you ran down the aisle, you might indeed create a very minor sonic boom to observers on the ground. Of course, you won't make nearly as much noise as jet engines, so they likely won't even hear it. StuRat (talk) 18:41, 13 January 2015 (UTC)[reply]
It is probably based on the Egyptian calendar actually since a year was 360 days (plus 5 extra days). Months were always 30 days and weeks were 10 days. I would think the helicopter question is mostly a matter of inertia. When a helicopter takes off it retains its inertia that it had while grounded. It moves by changes its inertia relative to the planet. Otherwise its natural state should be to move in the same direction as the planet (i.e. hover). Taking off doesn't reset its inertia to zero and cause the planet to rotate away from it.David Bradley I (talk) 19:06, 13 January 2015 (UTC)[reply]
We have 60 seconds to a minute, 60 minutes to an hour, and 24 hours to a day because we inherit these measures from older civilisations. Many, in particular the Babylonian civilisation, divided things into 60 because it is a particularly easy number to divide into smaller parts. Thus, 60/2 is 30, 60/3 is 20, 60/4 is 15, 60/5 is 12, and 60/6 is 10. Also, 60/12 is 5. 60 is the smallest number that when divided by 2, 3, 4, 5, 6, 10 and 12 gives a whole number answer. This is very useful if you don't have a calculator to help with your arithmetic. We have 24 hours in a day because originally the day and the night were each divided into 12 hours (24=12+12). 12 also has lots of divisors (2, 3, 4, 6, 12), and so is again a helpful number when you're doing arithmetic without a calculator, particularly when you're doing business that has to be equally split between 2, 3 or 4 people.
So our measures for time are really the result of people in history choosing numbers that made it easy for them to do their sums. If we were going to design a new time measurement system today, we might well choose something different. RomanSpa (talk) 18:55, 13 January 2015 (UTC)[reply]
(ec)
Why 60's? The EgyptiansBabylonians liked to use numbers that are effectively in base 60 - and from then we get 60 minutes in an hour, 60 seconds in a minute, 60 degrees in an equilateral triangle and so forth. 60 is actually a nice number to choose because it divides evenly by 2,3,4,5,6,10,12,15,20 and 30. 100 isn't so nice: 2,4,5,10,20,25 and 50.
The air more or less follows the rotation of the earth because of friction between it and the ground - helicopters remain stationary compared to the air (not really the ground).
Yes, if you could do that outside the airplane, that would cause a sonic boom. Yes, you would be travelling faster than sound. However, the speed of sound is (just like the helicopter) measured relative to the speed of the air. So inside the plane, the air is moving at the same speed as you are and the speed of the trolley is only a couple of mph faster than the air...so the speed of sound isn't broken. If you put the cart on the wing of a plane that's flying 1mph below the speed of sound and pushed it forwards at 2mph - it would break the sound barrier...boom...etc.
Isn't a sonic boom caused by the velocity of the source measured relative to the observer, not the air ? StuRat (talk) 19:14, 13 January 2015 (UTC)[reply]
DF has the correct answer and refs below. But perhaps you got confused with the doppler effect? Interestingly enough the common illustrations like those used in our article are vaguely similar to the illustrations for sonic booms. SemanticMantis (talk) 19:59, 13 January 2015 (UTC)[reply]
Aren't they basically the same thing ? That is, the Doppler effect describes waves being compressed in time or stretch out, due to the relative speeds of the source and observer. If they are compressed to a single wave, that's a sonic boom. StuRat (talk) 05:55, 14 January 2015 (UTC)[reply]
@StuRat: No, a shock is a very different sort of wave - it's mathematically modeled as a discontinuity, and they have special rules for propagation, energy dissipation, etc. In contrast, the doppler effect is simply the interaction of relative motion with classical sound waves. The doppler effect is dependent on the relative velocities of the emitter and the receiver, while the shock wave only depends on the speed of sound in the medium. Now, in the real life case of listening to airplanes, one will hear a doppler effect for subsonic planes, this is pretty obvious if you've ever stood still while a crop duster flies low over head. In the case of a supersonic plane, you don't hear anything until the shock reaches you, but then (I think) you will hear the pitch shifted down as the plane recedes (compared to someone moving in the same direction as the plane). SemanticMantis (talk) 15:59, 14 January 2015 (UTC)[reply]
Hmmm....I don't see how. The sonic boom has to travel from A to B (eg from a Concorde airliner to a car window down on the ground that shatters from the sonic boom)...the intervening air can't "know" how fast the car is moving - either the energy is transmitted or it isn't - and when that energy arrives at the observer, it still needs to be dissipated by shattering the window. If what you say were true then aircraft travelling at supersonic speeds would be suffering sonic booms from buildings on the ground...and how would the air near to the buildings 'know' to transmit the energy up to an aircraft that may or may not be above them? I think you must be incorrect.
Buildings don't make much sound to cause a sonic boom. I'd expect that if they did, passing airplanes at mach 1 would indeed hear sonic booms. StuRat (talk) 05:51, 14 January 2015 (UTC)[reply]
No no no, not at all. The only way you'd get sonic booms from a building is if the wind hit Mach 1. (And at that point you don't have buildings anymore.) --Trovatore (talk) 17:11, 14 January 2015 (UTC)[reply]
OK, I think I see the difference. The sound from the stationary object would only hit the fast moving object all at once if it was moving infinitely fast toward the source. It would get louder, though, if approached at high speed, including the speed of sound. Since a sonic boom never has exactly all the sound compressed into an instant, I wonder how the energy of the two compare, at different speeds. StuRat (talk) 18:11, 14 January 2015 (UTC)[reply]
The "sound from the object" is not the point. See the longish explanation below. --Trovatore (talk) 19:53, 14 January 2015 (UTC)[reply]
I think I see where Stu is going wrong here, and while it's definitely not my field, I think I know enough to clear this up in general terms. Here's my effort.
Stu seems to think that sonic booms come from the noise made by the booming object, Doppler-shifted past infinity. That is not exactly right.
Suppose you're flying along at a modest airspeed, say 100 mph or so. Consider a chunk of air just a little in front of your wing's leading edge. By the time the wing gets to where that chunk is, the chunk will have to have moved out of the way, right? Some goes over the wing, some goes under, complicated stuff happens to other parts of it, but in any case it's not where it was.
But how did it know the wing was coming? That's because the wing set up a compression wave propagating forward, which moved the chunk of air out of the way. That wave moves at the speed of sound.
Now suppose your plane is supersonic, and consider the same chunk of air just forward of the wing. Now the compression wave can't get there in time! The wing is just at the chunk of air, with no "warning", as it were. The piece of air has to just suddenly split in two. That's where you get your discontinuity, your shockwave, your sonic boom.
As I say, not my field, and I don't claim this exposition to be exact, but I think this is roughly the idea. --Trovatore (talk) 18:06, 14 January 2015 (UTC)[reply]
Note: The structure of responses might be disrupted by my outdent above — for future reference, I think Dragons flight is responding to SteveBaker. --Trovatore (talk) 18:08, 14 January 2015 (UTC) [reply]
No, a sonic boom occurs when an object is traveling through a medium (e.g. air) faster than the speed of sound in the medium. The only things that matter are the relative velocity of the object to the media and the local speed of sound. Observers don't enter into it. Either a shockwave forms, or it doesn't. It doesn't matter if someone is there to hear it. Dragons flight (talk) 19:54, 13 January 2015 (UTC)[reply]
Right, but Steve said it's the speed of the source relative to the speed of the medium, which isn't quite the same as it being the speed of the source relative to the speed of sound in that medium. StuRat (talk) 05:51, 14 January 2015 (UTC)[reply]
Regarding the divisions of time, we have a whole article about the Sexagesimal system. DMacks (talk) 19:16, 13 January 2015 (UTC)[reply]
The air more or less follows the rotation of the earth because of friction between it and the ground .. Actually I do not believe that is correct. Sturat AND stevebaker both said this, I'm a little surprised.. Is this a common misconception or are they just over simplifying things? This makes it sound like the earth is or was spinning faster than the atmosphere, or that the atmosphere somehow "lags" behind the earth for some reason. The fact is, the atmosphere has mass, just like the earth. The earth is rotating freely, there is no extra force keeping the earth spinning that has to somehow transfer to the atmosphere. In the earth's rotational frame of reference, the atmosphere is perfectly stationary, just like the water, just like a ball you put on a flat surface and just like us. I do not believe friction plays any part in it. Vespine (talk) 22:00, 13 January 2015 (UTC)[reply]
That would be true if there was no north/south airflow - but coriolis forces mean that there is lateral flow due to the rotation of the earth and that velocity has to be removed somehow. SteveBaker (talk) 03:15, 14 January 2015 (UTC)[reply]
And I did say they started out with the same rotation, but if not for friction, the atmosphere wouldn't necessarily maintain the same rotation speed as the Earth indefinitely. Look at the Sun, which rotates at different speeds at the equator and the poles, due to low friction relative to the other forces at play. StuRat (talk) 05:06, 14 January 2015 (UTC)[reply]
Curious, instead of admitting your mistake, you are both attempting to rationalize it. Either of you care to provide a citation for your claims? I believe you are both incorrect. Friction does NOT play any significant part in the atmosphere rotating along with the earth. It's newtons 1st law. What force is the friction counteracting? Coriolis effect is a frame of reference effect, textbook models assume no friction (search our article for "friction"). And sturat, we're not looking at the sun, we're looking at the earth, the sun requires plasma thermodynamics to explain, the earth doesn't. The atmosphere spins with the earth because it has mass just like the earth does and no additional force is acting on it to slow it down which "friction" would have to overcome. Surely if the earth was exerting ANY frictional force on the atmosphere, the atmosphere close to the earth would be "spinning" slower than the atmosphere at the top, which I do not believe is the case. Vespine (talk) 23:12, 14 January 2015 (UTC)[reply]
No, I think Steve and Stu are correct here. If there were no friction between the Earth and the atmosphere, their relative angular speed would drift over time, as the atmosphere was perturbed by various external torques. --Trovatore (talk) 01:40, 15 January 2015 (UTC)[reply]
If you don't like the Sun, look at Jupiter, where the friction is rather minimal, relative to other forces. There you get bands of atmosphere moving over 100 m/s, constantly. And the atmosphere of Earth does move more slowly close to the surface than it does aloft. Ever hear of jet streams ? StuRat (talk) 02:55, 15 January 2015 (UTC)[reply]
Now come on, stop trying to weasel out of it, citations please? Perturbations? We’re talking about general principles, please provide ANY citation that shows that friction from the earth has an effect on the movement on the atmosphere caused by the rotation of the planet. And NO Saturn is NOT good enough either, it is a gas giant, a completely different kind of planet than the earth. It is in effect a giant ball of gas spinning, not a giant ball of rock covered with a tiny film of an atmosphere. And while we’re at it sturat, which way do jet streams travel? And which way does the earth rotate? Oh snap, if the earth WAS causing friction, you'd expect them to be opposite wouldn't you? Friction has nothing do with the formation of jet streams, please feel free to read the cause section, which even includes a word on OTHER PLANETS where planetary rotation or surface friction is STILL not mentioned as a cause or even a factor in the formation of jet streams. The question was: why does the atmosphere not move in relation to the earth, the answer is because the atmosphere has mass and just as much relative momentum as the earth, as there are no external forces speeding it up or slowing it down (over sub geologic timescales), it will keep rotating at the same rate, friction plays no appreciable part in this. Vespine (talk) 04:43, 15 January 2015 (UTC)[reply]
I don't have a citation handy, but I haven't noticed you throwing them around either. Vespine, I think you're understanding "friction" to mean "the atmosphere would naturally stand still if it weren't for the Earth dragging it along".
But that isn't the argument. Sure, the atmosphere set in (rotational) motion will tend to remain in motion. But even if it's at some point synched to the Earth, why do you expect it to stay that way? There are always external forces. There's radiation pressure. There's solar wind. There are tidal forces.
The rotational acceleration that any one of these imparts to the atmosphere is probably small. They're probably reasonably random and tend to balance out, more or less. And to the extent that the net effect is in one direction in January, it may well be in the opposite direction in July.
But do you really expect them to balance out exactly? That would need explanation, I think. And if they don't balance out exactly, well then, over time, the effect is going to build up.
So how come we don't see a secular increase in wind speed over time, if it's not for friction? --Trovatore (talk) 05:24, 15 January 2015 (UTC)[reply]
No, jet streams aren't caused by friction with the ground, they are what happens to the atmosphere far from the frictional effect of the surface. It does it's own thing. And the whole reason the atmosphere of gas giants and stars behaves differently is because friction is negligible. We should probably discuss how the atmosphere of Earth would behave differently, were there no friction with the ground. Look at how one atmospheric phenomenon, hurricanes, behave now. They follow the prevailing wind direction, until they hit a continent. Then they either are deflected back out to sea, or they die. If there were no continents to stop them, they would likely continue in bands parallel to the equator for 6 months at a time, until the season changed. If the Earth wasn't tilted relative to the ecliptic, you might even get permanent hurricanes, like the gas giants have. StuRat (talk) 05:15, 15 January 2015 (UTC)[reply]
Here's a map of prevailing wind directions in January: [11]. As you can see, they set up in bands parallel to the equator, just like on Jupiter, until they hit a continent, then the bands are messed up. StuRat (talk) 05:22, 15 January 2015 (UTC)[reply]
I have provided several references, please feel free to point out where any of them mention friction as a force that plays a part in keeping the atmosphere in place. Let me put it this way, back to first principles: say you are standing in a train carriage moving at a constant velocity, what force stops you moving to the front or the back of the carriage? It's not friction, the answer is that no force is required to keep you from moving to the front or the back of the train. You could be on a frictionless surface, like a skateboard and unless the train accelerates you would remain in place. It's exactly the same question, it's about general principles. When you stand on a skateboard parallel to the equator on earth, is it friction stopping you from accelerating in a east west direction? That's nonsense. Vespine (talk) 06:51, 15 January 2015 (UTC)[reply]
You haven't provided anything remotely close to a reference for the claim that friction is not involved.
Again, you're misunderstanding the point. No one in this discussion has ever said that friction what keeps the atmosphere from standing still while the Earth rotates (which is what you seem to be implying with the "skateboard" example). I don't see any evidence that Steve or Stu ever thought that.
As for the "train" example, in practice, it absolutely 100% is friction that keeps you in place in your train seat. If there were not friction, you would respond to external forces and start to drift. There are always external forces; you can ignore them in the same sense you can assume a spherical cow. --Trovatore (talk) 07:13, 15 January 2015 (UTC)[reply]
MY source showing prevailing wind directions is excellent evidence for the effect of friction (with the ground) on the motion of the atmosphere. Perhaps you are having trouble with the word "friction". This includes things like running into mountains, which saps the wind of it's energy and/or redirects it in a new direction. Trees also have an effect. Flat, smooth ground (like obsidian) would have the least effect, even less than the oceans. StuRat (talk) 17:54, 15 January 2015 (UTC)[reply]
Babylonian mathematics
The use of base 60 is not Egyptian. The Egyptians used a non-place-value system of numerals, similar to Roman numerals, as did many ancient peoples. The Babylonians did use the sexagesimal system, which was a place-value system. It had great computational power, as do Arabic numerals, but its use required memorizing an extremely large addition table and an extremely large multiplication table. It, like base-ten Arabic numerals, did allow fractional computation to any desired amount of accuracy, by just computing the multiplication or division to the required number of sexagesimal (or decimal) places. In classical antiquity Babylonian arithmetic was used for astronomy and astrology, and not for other purposes, because it was difficult (but precise). Why the Babylonians used base 60, rather than base 10 or base 20, is a historical mystery. Robert McClenon (talk) 21:24, 13 January 2015 (UTC)[reply]
My error - I'm sorry...corrected, above. SteveBaker (talk) 03:15, 14 January 2015 (UTC)[reply]
Robert says that the reason for adoption of sexagesimal is a mystery, however the Wikipedia article implies it is due to the ability to count using one hand and the various finger bones. This is what I had recently read also, do the sources in the article support this? 203.109.158.201 (talk) 23:37, 15 January 2015 (UTC)[reply]
Helicopter question
The helicopter obeys Newton's first law of motion "When viewed in an inertial reference frame, an object either remains at rest or continues to move at a constant velocity, unless acted upon by an external force". If that wasn't the case if you jumped off the ground at the equator the Earth would move under you at 465 meters/second and you would end up a long way from where you started. So because you are already moving at a velocity of 465 meters/second when you jump, and there is no "external force" to slow you down, you carry on at the same velocity as the Earth and land in the same spot. But don't worry, you're not dumb. It took a genius like Isaac Newton to work all this out. Richerman(talk) 22:00, 13 January 2015 (UTC)[reply]
Well, once you ignore Newton's laws, anything could happen, but there's no reason to assume he'd hover above the ground pushing air out of the way at orbital speed, why not have him fly off to space in a slowly expanding spiral, staying above the launch point, and moving upward at his original launch velocity? μηδείς (talk) 22:54, 13 January 2015 (UTC)[reply]
Because the person who asked the question appears to be asking "why is it that when something leaves the ground that the spinning Earth doesn't move beneath it?". The fact that they used a helicopter as an example is not really relevant to what they are asking and I've tried to keep the answer as simple as possible. Richerman(talk) 23:38, 13 January 2015 (UTC)[reply]
I was looking at it the other way. The air, etc., doesn't move along independently of the Earth's surface either; i.e., get left behind. So maybe everything is either pushed by the wind, or inherently stays in its "place" which would either imply the air is keeping you stuck to the ground due to its pressure the Casimir Effect on the bottom of your feet, and that if you lose contact you will fly upward, not so fast, but in an ever widening spiral. There's a Latin phrase for the fact that assuming any contradiction implies all contradictions, so if we accept that one law of nature can be violated, we can accept the violation of all of them. μηδείς (talk) 02:14, 14 January 2015 (UTC)[reply]
We don't need Latin phrases or the Casimir effect to account for something that Newton's first law already explains perfectly well. AndyTheGrump (talk) 03:11, 14 January 2015 (UTC)[reply]
No, we don't. No one said we did. μηδείς (talk) 18:17, 14 January 2015 (UTC)[reply]
This kind of question is a rephrasing of the old joke about a truck full of birds and how they have to keep them flying in order to keep the truck's weight down. ←Baseball BugsWhat's up, Doc?carrots→ 20:13, 14 January 2015 (UTC)[reply]
Is it safe to add lactobacillus acidophilus to gazpacho and would it prevent or slow fermentation?
I guess this all comes down to how well it could compete against yeast and would the sugars available in gazpacho (mostly tomatoes) be adequate for feeding it? An ancillary question is how active is lactobacillus acidophilus in producing gases? The main problem with the fermentation is the gas produced and so it would make little sense to replace one gas-producing organism with another. — Preceding unsigned comment added by David Bradley I (talk • contribs) 18:48, 13 January 2015 (UTC)[reply]
As far as I know lactobacillus acidophilus do not produce gas, they produce lactic acid. They do not compete with yeast, they actually work well together, see: SCOBY. Ariel. (talk) 11:21, 14 January 2015 (UTC)[reply]
@David Bradley I: SCOBY is a fermenting agent. Kombucha, ginger beer, vinegar, all of these can be produced via fermentation with SCOBY. So I don't see how you would think it inhibits fermentation. Perhaps you mean that SCOBY might ferment sugars more slowly than a pure yeast? SemanticMantis (talk) 21:28, 14 January 2015 (UTC)[reply]
I thought it inhibited fermentation because that's what the study I linked to seems to indicate. Perhaps it depends on the environment. David Bradley I (talk) 23:17, 14 January 2015 (UTC)[reply]
How much Phytoestrogens, on average, we have on 100g of cooked soybeans?
This source says 40mg per 1/2 cup of soy beans, 165mg per 3.5 oz of roasted soy beans [12]. It appears to be a fairly reliable source but it does not itself cite sources, so better-cited sources will still be helpful. SemanticMantis (talk) 22:16, 13 January 2015 (UTC)[reply]
Fixed... Cooked... ! Ben-Natan (talk) 09:25, 14 January 2015 (UTC)[reply]
Female ejaculate
So I read over here that female ejaculate is actually just urine. However from what I read from other people and what I've seen in pornos, it looks more clear than normal urine and doesn't have the same offensive odor. I also heard that when it dries up it leaves behind a whitish residue as opposed to a yellow residue. My question is, is female ejaculate safe to consume unlike normal urine? Mind you, this is not a medical question, I'm just curious. 69.121.131.137 (talk) 22:51, 13 January 2015 (UTC)[reply]
Although I don't speak from personal experience, your suggestion that normal urine is not "safe to consume" seems to be false, at least if it's from a healthy person, as you can see from our article on urophagia (the consumption of urine). RomanSpa (talk) 00:54, 14 January 2015 (UTC)[reply]
That would explain why Aussies and Kiwis are always "taking the piss". :-) StuRat (talk) 04:59, 14 January 2015 (UTC) [reply]
Bear in mind as our article sort of says, what's shown in porn may not be particularly similar to what most people experience in real life, unless they're trying to emulate porn. Or to put it a different way, even though there could be female ejaculation that is distinct from urination, it doesn't mean that all, or even a majority of that shown in porn as "female ejaculation" is not simply urination or even simply some fluid held in the vagina and released at the right time [13][14]. Also, in both females and males (I presume you have partially experienced this yourself), the colour of urine can vary significantly depending on how much water has recently been drunk (and whether the water has been lost via other means like sweating). So "more clear than normal urine" is pretty meaningless, as urine can be fairly clear when dilute (see e.g. [15]). As that indicates, you can also get some weird colours due to certain foods and other dietary products, but I don't know if this is particularly useful for most porn purposes (in particular, I'm not sure if it's easy to get a milky colour without a bladder infection). Similarly, unless you are referring to Smell-O-Vision porn or are you a performer, camera operator, directory or someone else on porn sets, I presume you have no idea how the stuff on porn sets smells. (And realisticly even if you did have some sort of scent simulator and porn made for that purpose, they're not going to give the unpleasant smells unless it's for a specific market that wants that.) The smell can also be strongly influenced by diet, e.g. garlic, onion, asparagus and petai are foods fairly known for influencing the smell of urine (and often other bodily odours). I'm not sure that people find the smell of diet urine in general that offensive although they probably don't find it pleasant and can probably recognise the odour if they smell carefully enough in a suitable environment. People's perceptions of stuff is also often influenced by sexual activity. Nil Einne (talk) 04:50, 14 January 2015 (UTC)[reply]
I cannot help but be amazed at the range of themes this OP is curious about. Richard Avery (talk) 07:57, 14 January 2015 (UTC)[reply]
How do household appliance water tanks work?
I've had a few small humidifiers and they have all had a similar water delivery system. A removable water tank with a sealable opening (used to refill the tank with water from a faucet) and an opening at the bottom to allow the water to empty from the tank into the humidifier itself. It appears that the opening at the bottom has a spring such that when the spring is compressed, water will exit and when the spring is unaltered, the water tank is sealed closed. Somehow, the humidifier must be able to let in an appropriate amount of water from the tank into the humidifier via this spring opening. However, if it lets in too much water, the humidifier will leak, and too little water will interfere with humidifying a room. I've never seen any apparatus or anything that appears to somehow press the water tanks spring in some sort of regulated fashion.
While I know this description is not perfect, I'm wondering if it is enough for anyone to explain or find references that explain how the humidifier is able to let in the appropriate amount of water into the tank, especially given the absence of any noticeable mechanism on the humidifier that performs this job. — Preceding unsigned comment added by 68.10.236.226 (talk) 22:55, 13 January 2015 (UTC)[reply]
The ones I've seen, the humidifier body has a prong that pushes up against the spring-loaded valve on the bottom of the tank, letting water into a pool in the humidifier body. As the pool fills, air bubbles up from the valve (like dumping a bottle upside down rather than pouring it out in an even flow). Eventually the water-level of the pool reaches and covers the valve, so no more air can bubble back up into the tank, so no more water can pour out (it creates a partial vacuum in the air-space in the tank). It's the same principle as a barometer. You can do the same thing if you put the mouth of a bottle you are dumping out into a glass or other container that already contains a high water-level. As the humidifier uses up its pool, the water-level there drops, allowing more air to bubble up into the tank, allowing more water to drain into the pool, until the level again rises to cover the valve. DMacks (talk) 23:24, 13 January 2015 (UTC)[reply]
Thanks! I learned something new today! 68.10.236.226 (talk) 22:12, 14 January 2015 (UTC)[reply]
Resolved
Lorentz Contraction at near light and faster than light speeds
I am having some trouble visualizing this concept, so I will start my question with an example. For the sake of clarity, the descriptions I provide throughout this question will contain, perhaps, more detail than necessary. Let's say there are only two objects in the universe: the Earth, and a spaceship beside the Earth traveling in a line perpendicular to the radius. Let's also say for the moment that there is no warping of spacetime due to the Earth's gravity.
For relativistic speeds, the ship would need to be traveling at, say 0.925c. 1) At this speed, Lorentz Contraction dictates that Earth would contract along the y-axis and appear more like a watermelon lying on its side, correct? 2) Is this because traveling closer to c means that more horizontal beams of light (from the Earth to the ship, along the x-axis) hit your eye than normal? 3) Wouldn't this also make the squashed Earth appear brighter since the eye is receiving more light-per-second than normal?
This is all I am writing for now, though I do have more questions. To those who respond, please be sure to sign your replies. Thanks, Loonybin0 (talk) 23:02, 13 January 2015 (UTC)[reply]
A spherical object will appear circular to anyone traveling at any speed, though surface features like continents will be distorted within the bounding circle. It will also appear closer to your direction of motion than it would if you were stationary (relativistic aberration) and it will be smaller and blueshifted and brighter (if ahead) or larger and redshifted and dimmer (if behind). Can You See the Lorentz–Fitzgerald Contraction? from the Usenet Physics FAQ has some more information. -- BenRG (talk) 00:10, 14 January 2015 (UTC)[reply]
This video shows these effects pretty well. Starting at 5:08 they show rapid travel around the Earth (but with Doppler and brightness effects "turned off" so only the aberration is seen). -- BenRG (talk) 00:21, 14 January 2015 (UTC)[reply]
I don't understand this answer, for you say spherical objects "will appear circular" in all frames but I'm not so sure why that would be the case. [Appearances can be deceiving though.] Consider the counter-example of ions. From our referenced article on length contraction: "Heavy ions that are spherical when at rest should assume the form of "pancakes" or flat disks when traveling nearly at the speed of light. And in fact, the results obtained from particle collisions can only be explained when the increased nucleon density due to length contraction is considered." Also consider that a very vast spherical shell of relatively stationary stars is a spacial geometrical object that becomes measurably contracted in the direction of travel of the star-ship and thus less spherical. To be consistent, because the spacial scale of objects does not matter when plugging away at the Lorentz transforms, for we can talk about electron shells, planets or star systems, the Earth would also have to be measurably contracted as a thinner spheroidal object. This is what I understand to be predicted although the all important scientific measurement of large scale frame-dependent differences of length contraction has not yet been measured. -Modocc (talk) 03:15, 14 January 2015 (UTC)[reply]
Length contraction is a real thing. It's closely analogous geometrically to the fact that a diagonal slice through a cylinder (or a dowel, to be more concrete) is an ellipse rather than a circle. A moving object is length contracted at a particular time because "at a particular time" means the intersection of its worldline with a plane of simultaneity, and if that plane is slanted relative to the worldline (i.e. if the object is moving) then the slice is not a circle. That's a true statement about abstract spacetime geometry, but it's not as important as many people think, because planes of simultaneity almost never have any physical significance. For starters, they don't tell you what you see. What you see is the intersection of the worldline with your past light cone, not with a plane.
One way of understanding why you always see spheres as circles is that the effect of relativistic aberration turns out to be a Möbius transformation, and Möbius transformations take circles to circles. In fact there's a natural one-to-one correspondence between Möbius transformations and Lorentz transformations that's given by the aberration behavior (see Lorentz group#Relation to the Möbius group and the next section, "Appearance of the night sky"). I don't really understand geometrically why Lorentz transformations should behave that way, though.. -- BenRG (talk) 08:09, 14 January 2015 (UTC)[reply]
You didn't include the Sun so it will be quite dark. :-) But the light received at right angles will be blueshifted because of the transverse Doppler effect. Also, if the light from the surface is radiating in all directions, its intensity at any point is then inversely proportional to the distance squared. The Earth is supposed to be contracted like a watermelon too, but as BenRG points out above, optically, it will appear not to be. -Modocc (talk) 07:22, 14 January 2015 (UTC)[reply]
January 14
How sure is Moore's law?
I read a lot about how Moore's law may stop at some point in the next few decades. Is it likely to still be a thing in 2100 or might our computer power stop doubling as early as 2025?--79.97.222.210 (talk) 20:53, 14 January 2015 (UTC)[reply]
Moore's Law isn't really a law in any of the usual scientific senses, just a rule of thumb. At some point, and in my opinion, probably sooner rather than later, computer power will stop doubling because it will run into quantum limitations. That is my opinion. If it has still continued through 2100, and we didn't notice anything, it might be a case of having passed the singularity and no one noticing it, or something. Robert McClenon (talk) 21:15, 14 January 2015 (UTC)[reply]
Mathematically, it just isn't possible for something to double every 2 years, indefinitely. At that rate you will eventually use up all the available resources. To put some numbers on it, that would mean an increase of over a thousand times in 20 years, a million times in 40 years, a billion times in 60 years, a trillion times in 80 years, and a quadrillion times in 100 years. StuRat (talk) 21:22, 14 January 2015 (UTC)[reply]
OP here again. The article about Moore's law says the bekenstein bound, the ultimate limit from information theory, won't be reached for 600 years of continuous Moore's law, when it has a 100% chance of stopping. However, there are many reasons why it might stop before then, non of which are 100% certain. Will it stop before then is my question?--79.97.222.210 (talk) 21:36, 14 January 2015 (UTC)[reply]
For the entire time Moore's law has existed it's been about the size of silicon transistors, and I don't get the impression anyone believes that can continue past ~5nm because of quantum effects; see this article for example. That would put the end around 2020. As that article mentions, transistor switching speeds and clock rates already hit a wall a decade ago, so Moore's law as a measure of "power" is arguably already dead, though it depends on how you interpret "power" and that was never correctly attributed to Moore in the first place. Conceivably some other technology could take over, but nothing seems poised to. The Bekenstein bound is a useless upper bound; it's like saying that you definitely won't live longer than the lifetime of the universe. -- BenRG (talk) 21:48, 14 January 2015 (UTC)[reply]
One of my professors, who was an expert in digital circuit design, gave an excellent publication on Moore's Law that has since been republished by the IEEE: Future Directions in Mixed-Signal IC Design (2010). Moore's Law is a "gigantic (economic) feedback control system." Companies are controlling the "gain" so that they can achieve a fixed growth (speed and performance improvement) with respect to time. To control the rate of performance-change, they can tune the amount of input resource - talent and money. The diagram of the feedback control system in that presentation is great! Nimur (talk) 00:57, 15 January 2015 (UTC)[reply]
One of the reasons that Moore's law has so accurately tracked progress is that manufacturers plan their product to follow the law. So the likes of Intel and AMD set up their longer term product development with the goal of tracking the law. Even if they could progress faster, they don't. For sure it'll end sooner or later - and I think there are definite signs of that happening. But 5nm features aren't the end of the line - Moore's law says that the number of transistors on a chip will double every couple of years - but it doesn't comment on how big the chip is allowed to be. So even if we hit a limit at 5nm, there is no reason (in principle) why process improvements can't allow larger dies to be made economically. Another aspect of this is power consumption. If power consumption can be reduced sufficiently, then removing the heat from circuits is less of a problem and we can start to use the third dimension to pack more components into a reasonable amount of space. If you consider that a chip could comfortably be a centimeter thick - then with 5nm components, if you could manage the heat, you could theoretically make chips that were millions of layers deep...millions of times more dense than we have now. That would certainly add a LOT of years to the ultimate day when we can go no further.
There are also ways to get more horsepower without more complexity. Computers seem to go through cycles from the super-simple to the super-complex. RISC architectures were a big improvement over CISC - and nowadays, the RISC computers are getting pretty darned complex again. We can also explore tricks like moving the computational power into the memory devices...right now, getting stuff into and out of memory causes horrendous complexity with multi-level caching, instruction look-ahead, branch prediction and so forth. But if you had tiny super-simple computers embedded into the RAM array, you could eliminate all of that. We don't do it because the technology for making very dense RAM arrays is different from the tech for making fast computational engines - but it's not impossible.
This is all highly speculative stuff - but there is plenty of room for something wild and crazy-seeming to beat out present day architectures. SteveBaker (talk) 05:03, 15 January 2015 (UTC)[reply]
I also think we can do a lot more with parallel processing, so a PC might have 256 CPUs, each controlling a separate process. Each CPU can be relatively inexpensive, with the heat problem reduced by spreading them out a bit and allowing air gaps for fans to cool them efficiently. StuRat (talk) 05:34, 15 January 2015 (UTC)[reply]
The difficulty with that is RAM speed. On a modern CPU, it takes around 400 clock cycles to access a byte of RAM that's not in cache and just a couple of cycles to do whatever complex arithmetic/logic is needed to process it. With 256 CPU's competing for the same RAM bus, any cache misses would be exceedingly costly because you'd be waiting for 400 clock cycles times the number of CPU's that need to read memory! So your cluster would work well in algorithms where everything fits in cache - but perform disasterously in applications that require a ton of memory.
That leads you to put more and more per-CPU memory in place - and have less and less communications between them. This results in a situation where you more or less have a network of 256 separate computers...which, is pretty much a cloud-compute server....which is how all the massive super-computers of the world already operate. Those machines are shrinking in size and cost (or growing in capability at fixed size and cost), right along with Moore's Law...but it not exactly a new paradigm that'll change what sits on your desk.
Worse still, not many people have need to run 256 active processes. The computer I'm running on right now claims to be running 194 processes - but all but three of them are consuming 0% of the CPU time. Taking one process and splitting it over multiple processors generally falls afoul of Amdahl's law. There are exceptions...one is graphics. Our present generation GPU's already have in excess of 256 processors - the one I'm using right now has 512. They manage to avoid the problems of Amdahl's law because there is more than enough parallelism in the algorithm to consume a million processors if it were needed - and each tiny processor only needs a tiny amount of RAM to contain the entire data set - so memory contention is minimised. But this kind of improvement is more or less only useful for graphics.
That said, we have programming environments such as OpenCL that allow one to run more-or-less conventional software on those hundreds of processors. So, if your algorithm is sufficiently parallizable, your vision of there being 256 separate CPU's probably already exists inside the computer that you're typing on right now. It doesn't get used all that much outside of very specialised applications because it's just not possible to split "normal" software applications up into that many threads - and that's why Ahmdals law means that we're not likely to see massively multi-core CPU's solving the End-of-Moore's-Law crisis that's looming before us.
First is that Moore's Law is about transistor density, which doesn't necessarily imply computing performance. Following Intel's products, each technology node reduces linear size by about 0.7 (and area is 0.7x0.7=0.49). Intel generally takes a product and shrinks it to the next technology node which cuts it's size in half. Things to note are that some of the scaling that used to occur is no longer happening. Reticle sizes (die size limit) are pretty much stagnant. Wafer size was been at 12" for nearly 20 years (wafer size used to scale with Moores law). The place to look for Moore's law is in memory chips where density is the ultimate driver. Memory chips seem to have moved on to multiple die stacking as the driver for increasing density. --DHeyward (talk) 19:07, 15 January 2015 (UTC)[reply]
Archeology of dwarf planets
This year we have two of our last best chances to find evidence of prior intelligent life in the Solar System: the Dawn (spacecraft) visit to Ceres (dwarf planet) and New Horizons visit to Pluto. Supposing that some race of thinking beings existed roughly one billion years ago, under a cooler Sun prior to the resurfacing of Venus, and that they used either Ceres as a base for the exploitation of asteroids or Pluto as a base for exploitation of plutinos, how big a mark would they have had to make on either of these worlds in order for some trace of it to remain today, that would be recognizable with our probes? Wnt (talk) 23:03, 14 January 2015 (UTC)[reply]
I doubt if there's much erosion on either, particularly Pluto. However, over a billion years, I'd expect a significant amount of dust to accumulate from micrometeorites, so any evidence might be buried. This would leave either objects too large to be buried, or a probe capable of seeing beneath the surface. StuRat (talk) 00:14, 15 January 2015 (UTC)[reply]
Well, above someone gave a figure of 1 mm of moon dust for 1,000 years, which is a kilometer in a billion years. But... Ceres is only 0.0128 Moons of mass, according to the article. Less mass, less dust captured, and more easily bounced off into space... I think. Honestly I have no idea how the formula scales, but I'm suspicious it might be much less. Wnt (talk) 01:01, 15 January 2015 (UTC)[reply]
Pluto has an atmosphere therefore some erosion is certainly present on its surface. Ruslik_Zero 20:49, 15 January 2015 (UTC)[reply]
January 15
astronaut pulled because of gravity
If earth's gravitational attraction causes the moon to orbit around it, why are objects in the middle of them still floating? Say, will an astronaut floating in between the earth and the moon not be pulled into one of the two (after considering the Hill Spheres of each of them)? - anandh, chennai — Preceding unsigned comment added by 106.51.12.237 (talk) 01:44, 15 January 2015 (UTC)[reply]
I think you're confusing a few issues. 1) Objects in orbit around earth aren't "floating" because they are between the earth and moon. They are floating because they are in free fall. In order to feel weight, you need to exert a force against a surface. When you and your spaceship are both in the same free fall, then you exert no force against each other, so you feel no weight. You're both still under the effect of the earth's gravity, which is why you keep moving in circles around the earth rather than flying off at a tangent. The effect of the moon has absolutely nothing to do with it; any occupied vessel in orbit around the earth is so far from the moon such that the moon has an insignificant gravitational effect on it. It's about the same as what it is on Earth, which is basically nil. 2) Object located at the correct locations around the Earth and Moon do experience the effects of the Earth and Moon gravity exactly cancelling out. One of these locations is located between the Earth and Moon, but there are also several others; the set of them is known as the Lagrangian points, and they represent all the various locations in a two-body system where their gravity cancels exactly. --Jayron32 01:52, 15 January 2015 (UTC)[reply]
"..which is why you keep moving in circles around the earth rather than flying off at a tangent..." Thanks that answers...I didn't know object were just circling and not moving away. But if a gravitational pull can make an object circle around it, why not pull further? This is just a layman question, so pls bear if a fundamental science is missing while asking.. — Preceding unsigned comment added by 106.51.12.237 (talk) 02:29, 15 January 2015 (UTC)[reply]
Depending on the speed of the object in motion, it will have a stable orbit at a different distance from the Earth. The amazing part is, that the object naturally moves to that stable orbital distance all on it's own, because if it's too close, it flies outwards, and if it's too far, it falls inwards. StuRat (talk) 02:47, 15 January 2015 (UTC)[reply]
Maybe I'm misunderstanding you, but objects do not naturally move towards a stable orbit. If the object is not in orbit to begin with, it cannot achieve orbit unless it is accelerated during its motion by an additional force. That's why you can't shoot a bullet into orbit from the Earth's surface. Of course we call gravitational orbits stable because small disturbances to the object only change the orbit's shape and do not destroy it. - Lindert (talk) 10:18, 15 January 2015 (UTC)[reply]
You can't shoot a bullet into orbit because of air resistance from the atmosphere, which would cause it to burn up, if you shot it fast enough to achieve orbit after subtracting air resistance. I believe there's an old thought experiment where a cannon ball is fired, parallel to the ground, from a high mountain, in an atmosphere-free world, to achieve orbit. StuRat (talk) 17:38, 15 January 2015 (UTC)[reply]
Ok, you can indeed shoot a bullet into orbit if you shoot it parallel to the ground in a vacuum, but it will always return to its original height, so if fired at 5 miles above sea level, the orbit's periapsis will be 5 miles at most. I wasn't really talking about such low orbits, and effectively, the bullet is then fired above the planet's surface, not upwards from the ground. But you're right of course that low orbits are unstable inside an atmosphere. - Lindert (talk) 19:28, 15 January 2015 (UTC)[reply]
Orbital speed is an important factor. At any given distance from a planet, an orbit will be stable at a particular speed. That's why Mercury and Venus revolve around the sun faster than we do, while the outer planets travel ever more slowly, respectively. Low-earth orbits tend to take a given satellite around the earth multiple times a day. The higher above the earth, the slower a satellite moves. The moon, relatively far away, takes about 29 days to orbit the earth. Hence you can place a satellite at a point where its revolution exactly matches the spin of the earth. That's how we get geosynchronous orbits for television signal transmission and the like. ←Baseball BugsWhat's up, Doc?carrots→ 09:46, 15 January 2015 (UTC)[reply]
I agree with most of the above, but thought that a different response to "if a gravitational pull can make an object circle around it, why not pull further?" might make things clearer: If you think about an object orbiting the Earth, and ignore gravity from any other sources, the object will be following either a circular or an elliptical path about the Earth's center. If you pick any point in that object's travel, the velocity (speed and direction) of the object at that moment completely determines its entire path, which will be a closed ellipse or circle unless it hits something first. An object that is falling is in an elliptical orbit that is too narrow—its path intersects the surface of the Earth before it gets all the way around the elliptical path. (I have ignored escape trajectories and some other things, to keep this simple.) How narrow the ellipse is depends on how big the rotational component of the object's velocity is. If the object starts out with little rotational velocity about the Earth, it's elliptical path will be very narrow and it will fall almost straight down (but still on an elliptical path). More rotational velocity makes the object's path closer to a circle.--Srleffler (talk) 18:37, 15 January 2015 (UTC)[reply]
We say that an object in orbit is in "free fall" because a circular or elliptical orbit that keeps going around the Earth forever is really not any different from an elliptical orbit that happens to intersect the Earth's surface. It's an orbit either way—one just happens to have some rock and dirt in the way. Objects in a stable orbit are "falling", but keep missing the Earth.--Srleffler (talk) 18:41, 15 January 2015 (UTC)[reply]
hi, i don't understand how objects follow circular or elliptical path once you ignore the gravity acted upon it. Objects in space obey the laws of physics on earth right, that is they travel in a straight line unless acted by an external force.. They move in straight line, gravity pulls in, they move straight, gravity pulls, like a centrifugal force acted upon the object ultimately forming a circular or elliptical orbit. Doubt is that a moving body when exerted an external force (in this case gravity) should continue to move indefinitely in that direction. So once-straight-line moving objects should now come closer and closer towards the gravity pull. Where does it get the force to not come closer and continue to move in their path? - anandh — Preceding unsigned comment added by 106.51.18.198 (talk) 03:41, 16 January 2015 (UTC)[reply]
Objects near a large mass follow a curved path because of the gravity acting upon them. An object in orbit is constantly being pulled toward the primary; but, if its lateral velocity is great enough, the curving path misses the ground. —Tamfang (talk) 10:11, 16 January 2015 (UTC)[reply]
Antimatter
How do I calculate the brightness of sea-level air being instantly swapped for an equal volume of antimatter? (the air goes to another galaxy) This depends on mass and maybe on density if the density is low enough. Is it possible for the annihilation of just a thin skin of air with a solid object to blow away the air for long enough to affect the brightness or explosive yield? Maybe even have more than one cycle? Where the antimatter causes a new bubble of vacuum as the old one collapses and then touches the antimatter's surface? What if it's partially buried, how will it explode? Sagittarian Milky Way (talk) 12:00, 15 January 2015 (UTC)[reply]
I'd model it like a nuclear explosion, just with some 10K times more yield per mass. One difference, though, is that unlike a nuke, which can fizzle, sending unburnt fissile material out, anti-matter will always fully detonate, given an adequate supply of normal matter in the area. StuRat (talk) 17:33, 15 January 2015 (UTC)[reply]
I'd presume that the antimatter being gaseous would matter quite a bit too. As the anti-air annihilates against the normal-matter ground, a partial vacuum would form that would pull in more anti-air. So the reaction could easily run to completion. A nuclear weapon could (potentially) scatter it's fissile material away from the explosion and thereby prevent it from all going critical - but in an antimatter explosion, the dirt and dust that would be thrown into the air would just provide more fuel for an even more rapid mixing of matter and antimatter. SteveBaker (talk) 17:53, 15 January 2015 (UTC)[reply]
At about 105 K the radiation pressure would exceed atmospheric pressure. Once that temperature is reached, which seems likely, the force of the explosion would blow any additional material away from the surface. If we are replacing the entire atmosphere (the original post isn't so clear), then the potential energy available is about 5×1035 J, roughly 1000 times the gravitational binding energy of the Earth. So in principal, it could completely unmake the Earth. In practice though, I imagine that the initial detonation would blow a large fraction of the antimatter into space and leave a charred husk of Earth behind. At the same time, a layer of antimatter only about 8 microns thick covering the Earth would generate enough energy to make the Earth briefly more luminous than the sun. If Sagittarian Milky Way would prefer some other way of describing the amount of antimatter involved it would help to be more specific on the quantity and distribution. Dragons flight (talk) 19:13, 15 January 2015 (UTC)[reply]
I was not in fact thinking of globe-spanning antimatter but appreciate the calculations anyway. Okay, how about:
1. a sphere of anti-osmium, high enough to not have time to fall to the ground or 1000 meters, whichever is lower, and small enough to not have the power to expand the atmosphere much.
2. Same mass but a sphere of anti-air of the same pressure. I guess the answer above might happen.
and,
3. A very heavy skyscraper, say a third of a billion kilos. The Sun is 400 tons of mass annihilation per second so how many Sun's would that peak at? (visual brightness). Could you still extrapolate from hydrogen bomb megatons with that? Thanks everyone. Sagittarian Milky Way (talk) 01:54, 16 January 2015 (UTC)[reply]
What was the best Comet McNaught & Lovejoy (2011) looked like naked eye from 40°N?
(I never looked for it) Both covering the Sun area with an object and waiting till it gets low enough to not need that. Those comets moved so fast in a day so let's say longitudes near 74°W if UTC time of sunset matters.
2. How impressive were they after all naked eye twilight in cities with too much light pollution to easily see the Milky Way?
3. How long did each qualify to be a Great Comet for? (approximately). The article says they're Great (the only Great ones since 1997)
From the midlands of the UK (which isn't 40 deg N I know but still), I saw the multiple tails of Comet McNaught in the southern horizon while the sun was still up (about 5pm). It took me a little while to work out what I was looking at, but it was most certainly that comet. I never saw the head, however - that had already passed below the S horizon. --TammyMoet (talk) 19:35, 15 January 2015 (UTC)[reply]
It probably wasn't 5pm if it was before sunset in early January in England but that's pretty visible. It must've been great at a latitude where it's twilight or dark with the tail still up. I tried to see PANSTARRS extensively with binoculars and may have seen something. Maybe. (though they were 8x22s or something - built for daylight) Sagittarian Milky Way (talk) 20:01, 15 January 2015 (UTC)[reply]
My parents were able to see Hale-Bopp at their NJ shore from the Summer of 1996, through the holidays, and well even into the summer 1997, until they became curious that it had stopped moving, and realized they had been looking a street lamp through the woods for several months. It was quite visible to me over the Summer at their shore house due to the relative darkness and easily from anywhere that Winter. μηδείς (talk) 01:51, 16 January 2015 (UTC)[reply]
Yes that was a long one. I found a reference that Comet McNaught was first seen with the naked eye on January 1 (near invisible probably) yet I couldn't even find it's impressiveness circa 2 weeks later (lucky Southern Hemisphereans). Sagittarian Milky Way (talk) 02:14, 16 January 2015 (UTC)[reply]
Those two values differ by a factor of 1.6×1023, nowhere near the more than one hundred orders of magnitude which separate these numbers from the calculated zero-point energy (as described in vacuum catastrophe), but still a wide gulf. I assume that this is because the former, an upper bound, comes from not observing any discernible effect on the Voyager spacecraft, whereas the latter comes from estimations of the cosmological constant from astronomical observations.
Are there any other experimental measurements of the vacuum energy density? Have recent experiments with the Casimir effect give any numbers? -- ToE 14:37, 15 January 2015 (UTC)[reply]
1.6x1023 is suspiciously close to Avagadro's number...I wonder if there is a math slipup there someplace?
But Voyager is far from being in 'free space' - it's really close (in astronomical terms) to a bloody great star...so I'm not sure we're necessarily doing an apples-and-apples comparison. SteveBaker (talk) 18:00, 15 January 2015 (UTC)[reply]
This paper [16] (Anderson et al. 1995) gives an estimate based on Voyager and other spacecraft on the total mass of non-luminous matter in the solar system. If interpreted as an estimate on the density of dark matter + dark energy within the orbit of Neptune, then the value would be (-5.8 ± 5.2)×1012 GeV/m3. That's a 1 σ error bound, so it would probably be fair to say there is a high probability the density is < 2×1013 Gev/m3, which is close-ish to the 1×1014 Gev/m3 quoted above. Though it should be noted that the research I'm citing was done back at a time when dark energy was not yet a thing people worried about. Dragons flight (talk) 18:44, 15 January 2015 (UTC)[reply]
As Dragons flight said above, this value was an upper bound on dark matter in the solar system. The gravitational effect of dark energy is repulsive, so it doesn't even make sense to treat the Voyager estimate as bounding dark matter plus dark energy. The cited source (Dutra) also got this wrong. I removed him and the estimate from the article. (They've been there since the article's creation in 2009, which is more evidence that no one ever checks Wikipedia citations.)
The Casimir effect is unrelated to vacuum energy density, despite common belief (see hep-th/0503158). -- BenRG (talk) 19:06, 15 January 2015 (UTC)[reply]
Is the effect of dark energy repulsive on small scales? Cosmologically, dark energy has both a positive mass density and a negative effective pressure (believed to be roughly equal in magnitude to its mass density). In terms of the equation of state it is clear that ρ + 3p < 0 implies accelerating expansion. It is far less clear to me what effect dark energy is expected to have on gravitationally bound objects in a compact region of space. For example, if there is a density of dark energy ρ0 in our solar system, how much effective force does that apply to the orbits of planets? Assuming the net effective force is non-zero, then presumably the Anderson et al. results could still be interpreted as a limit on the combined dark energy + dark matter force regardless of the overall sign. Though, as noted, it is not a very useful limit since it is consistent with zero and orders of magnitude removed from what we expect on the basis of cosmology. Dragons flight (talk) 19:56, 15 January 2015 (UTC)[reply]
How far away from a well-lit city can you see the bazillion stars in the night sky?
How far away from a well-lit city do you have to live in order to be able to see the bazillion stars in the night sky, assuming you do not have access to electric lights? Is a fire's luminosity enough to obscure the stars? Do you have to live in a very isolated place in the middle of nowhere just to see the stars in the sky? 140.254.226.183 (talk) 15:34, 15 January 2015 (UTC)[reply]
There's no set distance, it depends on the size of the city, and the light pollution that is generated by it and the surrounding environs. For instance, I'm not entirely sure one can see the Milky way anywhere within 50 miles of NYC, but you can easily see the Milky way 20 miles from the edge of Las Vegas. In my experience, staring at a campfire will prevent you from easily seeing the Milky way, even in the desert (some info at night vision), but your eyes will adjust if you look at the sky and not the fire for a few minutes. We have a List of brightest stars. If you want to name a big city that you live near, we might be able to recommend a good place for stargazing (that article also has some good general info). SemanticMantis (talk) 15:45, 15 January 2015 (UTC)[reply]
Can light pollution be caused by a candlelight? What if there are hundreds and thousands of candles on the streets, at every shop in town, and inside every home? 140.254.136.154 (talk) 16:17, 15 January 2015 (UTC)[reply]
Sure, in concept. Whether you measure in lumens or lux or some other unit, it is basically the light intensity that causes light pollution. The source of the (white-ish*) light doesn't really matter: candles, fires, LED lights, incandescent bulbs, neon lights, fluorescent lights - all can cause light pollution that can interfere with seeing stars. *Keep in mind the Visible_spectrum of the light source does effect how much our night vision is degraded. This is why people use red lights to look at maps while night hiking (that is also described at night vision). SemanticMantis (talk)
Is the night vision degradation permanent or temporary? 140.254.136.154 (talk) 16:50, 15 January 2015 (UTC)[reply]
Usually temporary, see Adaptation_(eye)#Dark_adaptation. Usually your eyes will get as good at seeing in the dark as they ever will after about 30 minutes. There are probably ways to impair night vision for a longer amount of time but that would be the result of eye damage, not regular light pollution. SemanticMantis (talk) 16:56, 15 January 2015 (UTC)[reply]
What about Vitamin A deficiency? Can't Vitamin A deficiency cause night blindness too, or does it merely make night vision take much longer? Is the night blindness permanent or temporary then, once the individual is given sufficient Vitamin A? 140.254.136.154 (talk) 17:03, 15 January 2015 (UTC)[reply]
We have articles on Vitamin A deficiency and Night blindness that should answer those questions. Honestly I'm not that knowledgeable on this specific topic but you can get pretty far by using the search box to look for key terms. WP:WHAAOE is fairly true, and our articles are (usually) better written and better referenced than our replies here. SemanticMantis (talk) 17:11, 15 January 2015 (UTC)[reply]
Note that the quality of air makes a difference, too. If you have thin, low humidity, pollution free air, as you might get in a high desert area, then light tends to shine right out into space and not cause a problem, instead of reflecting back from the air and causing light pollution. StuRat (talk) 17:29, 15 January 2015 (UTC)[reply]
I recommend using http://darksitefinder.com which has a Google-Maps overlay showing where the skies are most and least light-polluted. Sometimes you can find dark spots that are not too far away to drive to - even if you live in a light-polluted city.
The amount of light it takes to erase your night-vision is very critically dependent on how far away you are from it. The intensity of a light drops off as the square of the distance - so being ten times further away from a candle makes it 100 times dimmer. It doesn't make sense to say "a candle is (or isn't) going to destroy your night vision for another 30 minutes" without making some indication as to how close to it you're going to get.
Light pollution from a city is a different matter though - the light from the city causes Skyglow. In that case, the totality of light projected upwards from the city is scattered by dust, water droplets, etc back towards the ground - often so far away that the city itself is over the horizon from the observer's position. Since our eyes use contrast between adjacent patches of the retina to resolve small features, that additional light from the sky makes it much harder to pick out the stars - and the dimmer the star, the harder it is to resolve.
Pollution from the city makes matters worse by increasing the amount of particulate material in the sky - and therefore the percentage of the light that's reflected back to you. That's why cities with relatively little pollution may still have relatively dark skies nearby even though they put out a lot of light.
So even if you get a substantial mountain range between you and the city, that sky glow can still reduce your ability to see the less bright objects in the night sky...and that has very little to do with disruption of your dark-adapted eyes.
Keep in mind that the "bazillion" is really 'only' about 5,000-10,000 distinct objects (mostly nearby stars, and some galaxies) as the upper limit visible to the naked eye. (The Milky Way is a glow mostly of stars to dim to make out individually.) This has been discussed before and should be in the archives. Or you can pick among these sources at google. μηδείς (talk) 18:42, 15 January 2015 (UTC)[reply]
More like 4,000 at best. Check the tables in the bottom half of this article. --65.94.50.4 (talk) 19:34, 15 January 2015 (UTC)[reply]
My use of "bazillion" means "a lot" or "plentiful". If I were to see 4,000 stars, then my first impression would be: "OMG! Uncountable!" 140.254.136.154 (talk) 20:33, 15 January 2015 (UTC)[reply]
Though visual acuity says the average young eye that can manage to focus (I can almost reach eyeglass vision by squinting and I'm 20/60 so it's not hard) is ~20/14.
There are 3.03 times as many stars if you could see astronomical magnitude 7.5 instead of 6.5, 2x dimmer pixels for 20/10 vision, so you could see almost 10,000 stars in a few seconds of head-turning if you have vision like Chuck Yeager.
The answer to the original question is up to about 200 miles for Tokyo (40 million ppl), as shown in the link below. For
Responses to the above: Snow cover also worsens the sky, probably at least 2 times as most light points down at much less reflective surfaces.
The gas molecules cause light pollution too, but are a less important factor as most waste light isn't blue wavelengths. this map shows 2006 light pollution instead of the 2001 linked here (click right above for Google Earth overlays and other areas). There's no land in the US without light pollution unless it's west of the Rockies, too rain-less for farming, or really crappy (either really boggy looking, cold and mosquito infested or really remote and tiny islands without access by land) Actually Dry Tortugas is not that bad (nice and tropical) if you can manage to get there. The situation is similar in Europe and worse in Japan and Korea which don't have any mainland or near islands without light pollution.
And about the candlelight. Streetlights are about 20 feet high and 10 times the lumens of 100W light bulbs. A point is no more than about 4 times their height from the nearest light (per rule of thumb to help old eyes not be bothered by high contrast) To model today's lighting with the known 100W LB brightness the increased 100W bulb streetlight density would have to be realistic. So to have approximately equal lighting on the standard 64 foot wide New York city street (city property line to city property line) you could put them about every 128 feet of each sidewalk's edge. That doesn't seem unreasonable so let's go with it. A 100W (frosted) is about 1500-1600 lumens. A candlepower is 4pi lumens. Let's call it 1/125ths of a light bulb. The most light polluted downtown zeniths on Earth have light pollution about 34 times brighter than the natural sky. This would still make the sky light polluted if we replaced every bulb with a candle but per [http:cleardarksky.com/lp/NYCNYlp.html?Mn=lenses] and Bortle Scale it would probably be as polluted as a rural-suburban transition area of today, except less asymmetrical since you're the center of Tokyo. The headlights are dimmer than 100W light bulbs but there's some buffer in the result and you'd think headlights are a relatively minor contribution if you saw the '03 Blackout. However the biggest metro area in history which actually used candlelight can't possibly be more than 2 million. If it scales with population then it would be a Bortle Class 2 - still light polluted, and noticeable to the naked eye but fairly minor. The air pollution of pure-gaslight Industrial Revolution London might've been an equal or greater problem. (What counts as candlelight anyway? If you're thinking of the old days, hollow perforated wicks were invented in 1790 which increased brightness and even Ancient Rome (pop. 1+ million) probably had many fires which were worth 10-100 candles). Sagittarian Milky Way (talk) 01:31, 16 January 2015 (UTC)[reply]
Only 60 by 60 stars gives you 3,600. I have seen moderate fields of Canada Geese with over 32 X 32 geese... over a thousand. μηδείς (talk) 01:31, 16 January 2015 (UTC)[reply]
It still shocks some city dwellers. 6.5 or brighter stars average 4 Full Moons apart. Not too bad except for the extroverts (they might need a meteor storm) or something. Sagittarian Milky Way (talk) 02:22, 16 January 2015 (UTC)[reply]
For some reason it's more impressive than the stars per square degrees makes it seem. Sagittarian Milky Way (talk) 02:24, 16 January 2015 (UTC)[reply]
Great emphasis is properly placed on avoiding light pollution when observing the night sky. But elevation above sea level is very important as well. All other variables being equal, the night sky will be far more dramatic at an elevation above 10,000 feet or 3000 meters than near sea level. I was once camped with my wife and son on a moonless night at the Vogelsang High Sierra Camp at 10,300 feet in California's Yosemite National Park. While in our sleeping bags in our tent cabin, we heard exclamations of starry wonderment outside. We got out of bed, and went out to see a dramatic and spectacular display of the Milky Way splashed across the sky in an unforgettable way. Make the effort some time to get high and remote on a moonless night with your loved ones. Cullen328Let's discuss it 04:59, 16 January 2015 (UTC)[reply]
Another time, we camped in the Hoover Wilderness at 10,100 feet with both our sons, knowing that it would be a moonless night during the meteor shower known as the Perseids. My sons now understand meteor showers far better than most 21st century urbanites. Cullen328Let's discuss it 05:38, 16 January 2015 (UTC)[reply]
Is there sand, dust, air pollution or evergreen trees (turpentine-like chemicals) upwind of the low dark sites you're comparing this too? That could be the reason for the unexpectedly good improvement. Also, your low sites might just not be free from light pollution. Light pollution extends for up to 200 miles off the California coast and there surely are light sources closer to you than the coast. Sagittarian Milky Way (talk) 06:14, 16 January 2015 (UTC)[reply]
January 16
Questions about athlete's foot
There are many questions (including some wild ones) that remain unanswered by the article. Please stop by to see if you know how to answer any of them at Talk:Athlete's foot#Questions. The Transhumanist 01:17, 16 January 2015 (UTC)[reply]
Bigger, better, faster, Moore?
I got interested in this with the earlier question about Moore's law. For a long time I've noticed CPU speeds have been about constant in the 2-3 GHz range. Why do they not get faster? Here's just one example of a not-too-cheap laptop that only has 2.4 GHz. If Moore's law still applies, why is it about the same as my 5 year old laptop (2.1GHz)? I know the law is about number of processors, and the article says that this is not linearly related to speed, but it does say that "There are cases where a roughly 45% increase in processor transistors has translated to roughly 10–20% increase in processing power." That should still mean a lot of speed, so more processors = faster and better, one would think. What's been happening, and is a 2.4GHz machine today that much better than a 2.1GHz machine from 5 or 6 years ago? I'm asking on the science desk because the other question was posted here, but I also feel it's a more general science issue, and not just for techies (it is after all a consumer-type question). IBE (talk) 05:39, 16 January 2015 (UTC)[reply]
Moore's law is about transistor density. CPU speed is peaked for level-0 SRAM single cycle reads. Up until 8-10 years ago (90 nm), Vt (MOS threshold voltage) and operating voltage was scaling with process. Leakage, cell stability, transistor drive, and the bitline development rate all hit a tradeoff wall at about 1 volt and 2 GHz. Normally, when we used to compare frequency, architecture and pipelining were the drivers. When it became SRAM, all single cycle reads were limited by the same cell so that's why ARM and x86 and all the various other architectures seem to peak at the same frequency. The performance gained is that the SRAM still shrinks so SRAM size increases but it isn't getting much faster. Each technology node has Vt/leakage tradeoff but the current consumed is exponential. This causes power delivery and heat issues that are not as good a tradeoff as more SRAM or processors. --DHeyward (talk) 06:33, 16 January 2015 (UTC)[reply]
Heat is an issue, but it's less problematic than you might think. Heat is removable with sufficiently-giant heat sinks or liquid nitrogen coolant; if it were the real problem, you'd see at least certain performance-crazed segments of the market running 10 GHz CPUs with cryo-coolers attached. In reality, the limiting factors for the last decade or so has been signal integrity, not thermal load. If you want to really know why we don't build 5 GHz VLSI circuits with today's technology, here are two books you should read:
Planar Microwave Engineering: a practical guide to theory, measurements, and circuits. CPUs that run digital logic at 3 GHz are really operating their analog parts in the microwave regime. You need to know how the analog electronics actually behave when you build them on silicon with modern processes. At 3 GHz, with the parasitic capacitances that are inherent to real transistors that we can actually build, square-waves look pretty not-square, and ones look an awful lot like zeros. Things get worse when signals have to cross clock domains, or worse yet, leave the substrate across a wire bond.
Computer Architecture: A Quantitative Approach. No punches pulled, this book runs the numbers on practical and theoretical computer architectures, so that you can understand whether the performance limitations are due to pipeline depth, cache strategy, data hazards, and so on.
No, heat, power density and IR drop really becomes intractable (and a poorly scaled) problem at the die level. 1 volt @ 130 Watts is 130 amps. Put that into a square centimeter chip with IR drop and inductance and power delivery (and heat removal) become huge, expensive issues. These high-performance CPU's are all flip-chip and die size has to be large when power is high so they have enough power delivery bumps. Wire-bond is out of the question due to inductance and the di/dt requirements. Because frequency is a function of voltage and power is V^2, the resulting increase in power with the increased frequency is effectively a V^3 scaling. So linear increase in frequency comes with cubic increase in power. --DHeyward (talk) 09:19, 16 January 2015 (UTC)[reply]
The Core i7-4700MQ CPU in that laptop actually runs at up to 3.4 GHz, temperature permitting. It also has 4 cores supporting 8 logical threads, while your older laptop most likely has 1 or 2 cores supporting 1 or 2 threads. Each core has a sustained maximum throughput of 4 micro-ops per cycle versus earlier generations' 3, and the execution units support 256-bit SIMD registers (AVX) versus your laptop's 128-bit SIMD (SSE). There's probably substantially more on-die cache RAM, and Intel has made various incremental improvements to other aspects of the internal architecture. Putting all of that together, it could easily be twice as fast as your laptop or more on realistic computing tasks. That's not very impressive for 5 years by historical standards, but CPU performance hasn't completely flatlined. (Source for some of the above: Agner Fog's microarchitecture manual.) -- BenRG (talk) 09:44, 16 January 2015 (UTC)[reply]
should you mix water back into sour cream, or drain it?
If you open a package of sour cream and there's some water inside, should you drain it (since it's water) or mix it together (on the theory that it was supposed to all be together, that's how much water should have been inside anyway)? — Preceding unsigned comment added by 212.96.61.236 (talk) 07:38, 16 January 2015 (UTC)[reply]
I usually drain it, but it's just water. Won't hurt or help much. Can always replace it later if you want, but it'll go rancid before it ever dries out in a fridge. Emulsifiers make sure of that. InedibleHulk(talk) 08:08, January 16, 2015 (UTC)
I just realized my sour cream company also sells the ingredients. Yours might, too. I'd never thought of sour cream as something to repair instead of replace, but if you're feeling frugal, you might be able to save the mixture, well beyond the best before date. InedibleHulk(talk) 08:30, January 16, 2015 (UTC)
Under that first link under "Flavour" it says, hilariously, "Bland flavour with a hint of dairy." 212.96.61.236 (talk) 08:45, 16 January 2015 (UTC)[reply]
Subterranean rivers
Do subterranean rivers generally end up discharging into the sea like most other rivers? I always assumed so but the article doesn't say. If so, do we know where any of these "mouths" are?--Shantavira|feed me 12:37, 16 January 2015 (UTC)[reply]
The article names many of the mouths. The water has to go somewhere, after all. However, in some cases like the Mojave River that destination may be an inland delta on a salty lake, or even just to dry up as an intermittent river. Wnt (talk) 15:34, 16 January 2015 (UTC)[reply]
Surely it can't be just like above-ground rivers draining into above-ground seas because in that case, evaporation from the oceans forms clouds which causes the water to rain on hilltops and mountains to keep the rivers flowing and to stop the seas from eventually overflowing.
Below-ground, what is the mechanism to lift the water from subterranean lakes/seas back up to the source of the water for the subterranean rivers? I presume that some water makes it back to the surface from geysers and such - and water flows into the subterranean rivers from the surface to keep them flowing...but it's hard to believe that enough water is lifted to the surface to keep the levels of large underground aquifers from just filling up and causing the underground rivers to stop flowing.
Obviously, for shallow underground water, it can arrive back onto the surface from a spring - but that's not going to work for rivers that are further below ground than the lowest point in the local topography.
I can't say for all caves, but for one of the major ones, Mammoth Cave National Park, whose profile looks like this,[17] its underground river flows downhill at a shallow angle and then opens out into the Green River, a tributary of the Ohio. ←Baseball BugsWhat's up, Doc?carrots→ 17:22, 16 January 2015 (UTC)[reply]
Raspberry Ketone B.Half life
How could I know the Biological Half life of Raspberry ketones?, I wouldn't mind import it from a source you guys consider reliable, to the article. Thx, Ben-Natan (talk) 16:29, 16 January 2015 (UTC)[reply]
Kg to lunar lb
How much does 22kg weigh on the moon? Apollo_11#Lunar_ascent_and_return says that the astronauts lifted two sample boxes containing more than 22 kilograms (49 lb) of lunar surface material, but because of the moon's lesser gravity, 22kg weighs a lot less than 49lb. 65.210.65.16 (talk) 19:25, 16 January 2015 (UTC)[reply]
The Moon's gravity is 0.1654 of Earth's, so a mass of 49lb would "weigh" 49 times 0.1654 on the Moon. Note that the mass remains unchanged, so extra care has to be taken when the mass is moving because it has the same momentum as on Earth. Dbfirs 19:48, 16 January 2015 (UTC)[reply]
(ec) Both kg and lb are used here as units of mass. Although the Pound (mass) can be used as a unit of weight, this is also true of the kilogram. See Mass versus weight. Weight is not a very useful quantity when talking about the contents of a sample. However, if you used a spring-based or electronic scale, 22 kg on Earth weighs 0.1654 * 22 = 3.64 kg on the moon, which is equal to 8.02 lb. - Lindert (talk) 19:49, 16 January 2015 (UTC)[reply]
Actually Lb is always weight but in standard gravity, it's a constant relation to mass. The term for mass is Slug --DHeyward (talk) 21:22, 16 January 2015 (UTC)[reply]
That's not what I was taught! A slug is a rarely-used unit of mass, along with the Pound (mass). Dbfirs 21:27, 16 January 2015 (UTC)[reply]
The kilogram is a unit of mass. A mass of 22 kg will still have a mass of 22 kg if it is relocated from the Earth to the Moon. The force of gravity, at the surface of the Earth, is the mass times the acceleration due to gravity, 22 × 9.807 ≈ 215.8 newtons. On the moon the force on the object due to gravity is 22 × 1.622 ≈ 35.68 newtons.
It would be foolish to further contaminate the Moon with US customary units so I will not do so. Jc3s5h (talk) 21:51, 16 January 2015 (UTC)[reply]
If you're suggesting that the metric system is the realm of lunacy, I won't argue. Now, here's a poser: How many newtons does one fig newton weigh? ←Baseball BugsWhat's up, Doc?carrots→ 22:12, 16 January 2015 (UTC)[reply]
If ever I visit the Moon, I shall make a point of taking some Imperial units with me, especially a 100-year-old pound mass that I happen to own. Fortunately for Jc3s5h, I'm not likely to make that journey. Dbfirs 22:22, 16 January 2015 (UTC)[reply]
What software would you use to model something spreading in water (river, lake, sea)?
What software would you use to model something spreading in water (river, lake, sea)? — Preceding unsigned comment added by 31.4.152.13 (talk) 23:45, 16 January 2015 (UTC)[reply]
The look of it? Maybe Blender. The actual physics? Maybe Simulink. 75.75.42.89 (talk) 00:38, 17 January 2015 (UTC)[reply]
![[11]](http://www.climate-charts.com/images/vector-wind-january.png){kind=link}
Resolved![[17]](https://pubs.usgs.gov/sir/2008/5023/section8_files/image010.jpg){kind=link}