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.
Supernova confusion, and the fate of nearby/bright stars
Hi. The article on Supernovae states that type Ia supernovae are the result of star-dwarf interactions, type Ib and Ic are the result of truly massive stars, possibly Wolf-Rayets, and that type II supernovae have a mass of at least 9 solar masses. However, this causes a contradiction. The article on the Chandrasekhar limit states that stars with masses greater than 1.4 solar masses will collapse into a neutron star rather than a white dwarf, therefore initiating a supernova. Or, is this defined by the mass of the star in the late phase of its life, when it has burned the hydrogen and helium and begins to swell, thereby losing some of its mass? I see that most stars visible in the night sky do have masses greater than 1.4 Sol. Why are there not more supernova explosions in our own galaxy, then? Is it possible for stars to gain significant mass during their lifetime, other than by ingesting material from a companion? The article on black holes does not mention this, but I read somewhere that a star having a mass over 6 Sol is a good indication it may collapse into a black hole (assuming that any core remnant is not destroyed). Also, when two medium-mass stars with similar masses in a very close binary system collide (due to gravity in the system shrinking their orbits, not a by-chance collision), is the result a supernova or a hypernova? The article on supernovae does not mention this category, and apparently hypernovae refer only to hypergiants collapsing.
If the limit for a star to end as a supernova is indeed 1.4 Sol, then looking at the top ten brightest stars in the sky, it looks like that Arcturus and Vega will explode as supernovae; Sirius and Procyon will also explode as supernovae, but interactions with their companion dwarf star could initiate a type Ia instead; Canopus and Achenar will explode as supernovae, and are just massive enough to perhaps end as black holes, Rigel and Betelguese will be especially energetic supernovae resulting in black holes; Rigil Kentarus will have one star swell to red giant first, probably star A, then shed its outer layers, and if the explosion doesn't significantly disrupt the second star, then possibly its remaining material will migrate towards the remnant of star A; Capella appears to be a binary system of two stars massive enough to generate supernovae, perhaps the explosion of one will disrupt the other, or else we could have stellar matter being drawn towards a neutron star. Most of these stars will probably be well away from Earth, though, by the time the explosion occurs, because a positive radial velocity would cause the star to be farther away, and a negative one probably means the star will have long receded by the time the explosion occurs. Or, is there something I'm missing here? Would this mean that supernova explosions are likely to be common near Earth, and would they significantly affect our atmosphere?
Also, what exactly are the evolutionary phases of higher-mass stars (those heavier than 1.4 Sol, specificly)? Does a blue giant evolve to a red supergiant, does a blue supergiant evolve any farther before exploding, what about white and yellowish-white stars in this category, are they still the young versions of red giants or red supergiants? Also, in the case of supergiant-black hole interactions, such as with Cygnus X1, what is expected to occur when the supergiant itself goes through the end of its life cycle? Thanks. ~AH1(TCU)01:29, 20 March 2009 (UTC)[reply]
Wow, so many questions... I won't tackle all of them. The gist of most of what you are asking seem to boil down to "what happens to stars that are heavier than chadrasekar's limit but are lighter than 9 solar masses? Some of them will end their lifes as Planetary nebula. This page has a nice explanation. Dauto (talk) 03:18, 20 March 2009 (UTC)[reply]
My point was that after shedding the outer layers on a planetary nebula the 5 sol star isn't a 5 sol star no more. So that's the end of the 5 sol star. Dauto (talk) 13:38, 20 March 2009 (UTC)[reply]
Hi. OK, so it appears middle-weight stars usually end up with a much lower mass. What happens, however, with binary systems like Sirius and Procyon, does the white dwarf absorb the extra material and end up as a type Ia supernova? Also, is it possible to predict whether a star such as this will lose most of its mass or not? Thanks. ~AH1(TCU)17:14, 20 March 2009 (UTC)[reply]
hair tests again
thanks for the aswers.
but i'm confused...if ur hair takes in drugs....does that mean almost any chemical put in our bodys go in the hair? or is God just getting back at stoners? —Preceding unsigned comment added by 76.14.124.175 (talk) 02:03, 20 March 2009 (UTC)[reply]
Asking my wife again. It's not that everything you take in ends up in your hair, but most drugs have chemically very similar chemical compositions, and those compounds do tend to accumulate in the hair. After all, the basic idea of drugs is that they mimic chemicals in your brain, and those chemicals also tend to accumulate in certain places like hair and fingernails. It isn't that ONLY drugs do, its that drugs are one of the things that do accumulate there. There are many other things that do, like heavy metals and arsenic, and hair tests can be used to show that a person has been poisoned over a period of time. The deal with hair is not that it magically absorbs drugs; its that it lasts a LONG time, so it carries a record of things you have taken in over a long time. And, ethnicity does effect hair type; your ethnicity can be positively identified by microscopic analysis of your hair... however no person or ethnicity is immune from these hair tests. Again, your only option is to shave your head; however if you shave it after being told that you need to give a hair sample for a drug test, then they will likely know exactly why you did so. Your options are a) don't do drugs or b) don't apply for jobs where it matters... --Jayron32.talk.contribs02:46, 20 March 2009 (UTC)[reply]
I don't believe shaving your head will do the trick. We don't have hair only in our head. There are also other ways of testing for drugs - read drug test for more, but they don't have a long detection period like hair test.--80.58.205.37 (talk) 12:54, 20 March 2009 (UTC)[reply]
Are humans the fastest long distance runners?
When it comes to the fastest on land, everyone bows down to the sprint of the cheetah. But beyond the sprint, what is the fastest land animal over a substantial distance, let's say 50 miles or so? I've recently heard an assertion that we, as a species, were very successful in our infancy because we evolved to be the best at tracking herds over very long distances. Sappysap (talk) 02:37, 20 March 2009 (UTC)[reply]
I've heard that said, many times. It may be true...but I don't think so. Marathon runners can do 26 miles without a break. However, in the Man versus Horse Marathon - the race was won by horses in the first seven years although a human did win on the eighth event - but on a bicycle (which, IMHO, is cheating). The race was run for 25 years before the first human won on foot. In 28 years of running the event, only two humans have ever won on foot. For some reason that's only a 22 mile race, but it's cross-country - which may give the horse an unfair advantage. But then consider that they horses are HEAVILY handicapped by having to run with a human rider on their backs! If the runners had to carry a 40lb backpack - I think it would slow them down too!
So it's abundantly clear that 22 miles isn't enough to give the human a winning advantage. I had a neighbour in England who was a big time long-distance runner. He did the London-to-Brighton foot race (which I think is 50 miles or so) - also several double-marathons (52 miles) and the South-Downs-Way run (I believe 70 miles) and the Isle-of-Wight race which is also some crazy long distance. But I don't think an average human can do that - even with training.
Yes, true. But may be the 'Man versus Horse Marathon' isn't the best way to test the hypothesis. Horses, after all, are pretty good long distance runners themselves. May be we would do better against animals more adept of short bursts of very fast sprints like impalas? Dauto (talk) 03:54, 20 March 2009 (UTC)[reply]
But here is my hypothesis in a nutshell: We know that most people (my wife, for example) can more or less run 26 miles - with a bit of training (she's never run a race over any distance in her entire life - she trained over two months - and finished the London Marathon in a hair over 5 hours - although she did walk some of the way). It's not unreasonable to suppose that pre-soft-living-modern-civilisation-humans could all run at least 26 miles if they had to. But we also know from the Man-vs-Horse thing that AT LEAST the one species we've seriously tried this against can beat us easily over 22 miles WITH A HUGE LOAD ON THEIR BACKS. So I'm betting that horses without riders would have no problem whatever in whipping our asses out to at least a few miles beyond the regular marathon distance. However, we have these ultramarathon loonies who run 50 mile races. It's perfectly possible that the horse gives up at about 30 miles...and that SOME humans can make it out to 50 miles. But if we're taking about maybe 1000 people in the world who run ultramarathons - that's the top 0.00001% of humans. I'm pretty sure we couldn't all do that - even with training. And what if we picked the very best long-distance horse out of all the horses in the world - and trained the heck out of it. Gave it really nice Nike running horseshoes and a digital heart-rate monitor with integrated pace timer - no rider, no saddle - and made sure it had specially formulated 'rehydration' stations every few miles...wouldn't the best horse manage equal amounts of improvement over the general population of horses? I don't think there is any evidence whatever that a 'typical' human could out-run a 'typical' horse over any significant distance...and I don't believe that the top 0.0001% of humans with the best training and support facilities could beat the top 0.0001% of horses if they were given fair training and support (and no riders!). And that's just horses. What about all of the other long-legged runners of the world? I think this one is busted...unless there is some solid evidence to the contrary. SteveBaker (talk) 14:22, 20 March 2009 (UTC)[reply]
Wait, that's not a fair comparison at all! Horses have been bred for centuries for speed, endurance, carrying capacity, etc. How would a horse's pre-domestication ancestors fair in a human-vs-Equus ferus marathon? APL (talk) 01:09, 21 March 2009 (UTC)[reply]
How is that fair either thought? Prehistoric humans were probably quite fit but I doubt they compared to modern professional marathon runners at running such long distances. Nil Einne (talk) 14:05, 22 March 2009 (UTC)[reply]
Let's play devil's advocate for a bit... Okay, so an average horse could beat an average human in a single race of 50 miles. How soon until it can go another 50? I imagine it would take a lot longer to refuel a horse than a human; in fact, if the human slowed to a walk here and there, it could refuel on the run to some degree, or at least take in some water. Quadrupeds can't do that. The horse is going to need enough energy to haul its 1,000 lb carcass across the plain, while the human only needs to haul its ~150 lb carcass, and gets to take in higher calorie foods to boot (including, er, horse, but that's a bit rude to your opponent...). Sooner or later the issue of fuel quality and fuel consumption are going to overwhelm any short-term equine superiority. Maybe. Matt Deres (talk) 20:14, 20 March 2009 (UTC)[reply]
Interesting point - I hadn't thought about it that way. However, horses are capable of eating grass, which is generally more readily available in large quantities than food suitable for humans. --Tango (talk) 20:34, 20 March 2009 (UTC)[reply]
See Persistence hunting. Wolves quite probably could beat humans as they also do something similar, I don't know. It would only need a good fit person to run down a horse without a rider though, they wouldn't need to be Olympic standard or anything like that. And by the way I've run longer than that 50 miles of those 'ultramarathon loonies' ;-) Dmcq (talk) 22:40, 20 March 2009 (UTC)[reply]
Why do you say that? As SB has mentioned given the conditions the horse with a rider is subject to, it seems resonable a horse without a rider would be capable of being faster. The question is would it ever actually run that fast if there isn't a rider edging it on? Well it's difficult to say IMHO. As I've mentioned below, in general we can expect most animals wouldn't. But if you are chasing a horse as a prey and the horse realises you are a predator it seems to me easily possible the horse will actually run that fast Nil Einne (talk) 14:33, 22 March 2009 (UTC)[reply]
I just had a good read of the Nature article referenced at the end of the wiki article on the evolution of endurance running in humans and it says some dogs and horses that have been bred for endurance would probably beat humans. The wolves article says they normally give up chasing after a fairly short distance but one was observed hunting a moose for 35km. Another animal that possibly would beat humans is the kangaroo. Dmcq (talk) 17:46, 21 March 2009 (UTC)[reply]
The refueling thing is an interesting point. It's worth remembering many (not all obviously) marathons don't involved the runners bringing their own water. Nil Einne (talk) 14:07, 22 March 2009 (UTC)[reply]
IMHO one issue we're not addressing is the difference between what can be done, and what is done. Personally, it wouldn't surprise me if a number of animals can beat humans in general. However many of them are never going to do it in practice. Similarly while humans may have evolved endurance for long hunts, what sort of distance are we talking about here? Did humans really chase animals by running after them non stop for 50 miles? Nil Einne (talk) 14:11, 22 March 2009 (UTC)[reply]
Without having read the article that Sappysap is referring to, I wonder if it's solely referring to our endurance or it may also refer to our intelligence etc. I presume one advantage humans have is that they have endurance and also intelligence. Let's say you are chasing something. Perhaps it's about the same speed as you so you don't really catch up to it and it doesn't escape. Eventually you tire and slow down (or perhaps you could go on but decide the current run is pointless). It 'escapes' and then slows down itself. Trouble for it is you may rest and 'refuel' and then go on. You can see it's tracks so you can easily still go after it. It doesn't know this so it's not necessarily running away from you any more. Eventually you may get close and it sees you and runs away again. Perhaps you repeat the same thing. It's easily possible you will ultimately win because you are chasing it in a direct line and wearing it down successful. It's not necessarily the case you have more endurance then it, you have good endurance sure but you are also smarter. Nil Einne (talk) 14:33, 22 March 2009 (UTC)[reply]
Plenty of animals are far better trackers than humans. Humans may have an advantage in a race to a pre-determined finish line because we can pace ourselves. I'm not sure any other animal would understand the concept of a long distance race well enough to do that. In a chase, though, pacing yourself doesn't really help unless you know how fast you and your opponent can run and for how long at various speeds and can work out a strategy to win, which would be rather difficult (an maybe impossible, depending on the respective abilities of the predator and prey). --Tango (talk) 14:40, 22 March 2009 (UTC)[reply]
You'd have to watch the episode in David Attenborough's series 'The Life of Mammals' where a Bushman runs a kudu to death to really appreciate what can be done. They typically have to run 25 or 35 kilometers which is nothing to a trained long distance runner. Dmcq (talk) 00:06, 23 March 2009 (UTC)[reply]
What is your point? So humans are better long distance runners than kudu, that doesn't answer the question. We knew humans weren't the worst, we're asking if they're the best. --Tango (talk) 00:12, 23 March 2009 (UTC)[reply]
You seemed to think it required special pacing. It doesn't. To win against other humans does. As to the best long distance runner I don't know but my best guess would be the kangaroo, I'd be surprised if humans actually are the best but they're very good rather than not the worst. I haven't a citation but I believe people in America in the past have run down wild horses rather than doing the sensible thing and creeping up and lassoing them. Dmcq (talk) 14:49, 23 March 2009 (UTC)[reply]
When the sun becomes a red giant...
About how long will it take for it to expand from its current size to red giant size (following the collapse of its core once the hydrogen there is used up)? 69.224.37.48 (talk) 03:09, 20 March 2009 (UTC)[reply]
its the biggest question ever ... what's the beginning , what's the source of evry thing .. if i said god is the source, atheistes will be angry.but if i said it's avery powerfull elian had created the earth ... i think they will buy that.
i just need to know whats wrong with god theory ... it might be right . but i think that humans dont like the idea of being a lower cretures ... we are so pride to be god slaves,we need so much to belive that there's no destiny ,so we can make our own.
human evolved from monky...monky evolved from (whay ever)...all the way to the creation of the universe ... from where did the universe came from ... from where that gas came from ... what is the first thing ... what is ground zero.
and if there is no god , and all this religion thing is just acrap,then i think the best thing that happened to the earth is hetler...we must let the smartest,the strongest , the healthiest ones to survive .who cares about moral standards ,we invinte these standards,and we can change them ,i think it's inmorale to leave the weak alife so they can multiply and reduce the chances of our survive,we should eliminate them.
and why do we evolve to have this huge power of thinking ... were we to needy to find answers for the question we had before we have the mind to ask.whats the need driven us to evolve to have this huge brain ... food ..???
There are two (implied) questions you are asking, even if you don't realize it. They have different answers. Question 1 is "What is the process by which the universe was created" or "what went on when the universe came into being". Its a procedural question. The answer, as far as we can tell, is that some form of the Big Bang brought it about, somewhere in the neighborhood of 13-14 billion years ago. Now, while this satisfactorily answers your first implied question, it does not answer your second which is "What is the cause of the Universe coming into being" or "What is the purpose for which the universe was created". The answers to THOSE questions are ultimately unanswerable via direct observation or by inferences from those direct observation. Assigning meaning and purpose to creation isn't really the realm of observational study, so one must derive their own personal answer to the question. Did God make it so? Is it all random? Any answer you arrive at must be arrived at via faith, even if your answer is "The universe has no purpose at all". You may be interested in looking into the field of Cosmogony which discusses the philosophical (as opposed to the procedural) questions of the creation of the universe. --Jayron32.talk.contribs04:28, 20 March 2009 (UTC)[reply]
Let me point out one thing you said that reveals you haven't thought about that long enough.
You said "i just need to know whats wrong with god theory ... it might be right . but i think that humans dont like the idea of being a lower cretures ..." If that was true, most people wouldn't believe in God. We know that that's not the case.
Now, if we skip all the senselessness about eliminating week people (not a very moral thing to say), we get to the only thing in your rant that actually sounds like a science question:
You asked "why do we evolve to have this huge power of thinking?"
Oh, someone who concludes that if there is no God, Hitler is awesome because without God there's no morality! Why, sir, you have unintentionally created an argument for belief in God! What an amazing coincidence! -- Captain Disdain (talk) 10:53, 20 March 2009 (UTC)[reply]
As far as I understand it, evolution doesn't say that humans evolved from monkeys. Instead, it says that humans and monkeys evolved from a common ancestor. This common ancestor no longer exists (i.e. it is extinct). 12:59, 20 March 2009 (UTC) —Preceding unsigned comment added by A Quest For Knowledge (talk • contribs)
Well, yes, that's true. It's accurate to say we evolved from apes, but monkeys are a separate class of primate - it wouldn't be accurate to describe the most recent common ancestor of modern monkeys and humans as a monkey. (The most recent common ancestor of humans and non-human apes was an ape, though.) --Tango (talk) 13:12, 20 March 2009 (UTC)[reply]
Here we go again...
its the biggest question ever - maybe - but I think I have bigger ones. Abiogenesis is one. Is there intelligent life throughout the universe is another. Are there parallel universes is a third. But this is right up there.
... what's the beginning , what's the source of evry thing - that's an easy one - the Big Bang. We're really very sure about that now. We know pretty much exactly what happened from about the first millisecond of existance. We still need to fill in some details about dark-matter and dark-energy - but we're definitely getting there.
.. if i said god is the source, atheistes will be angry. - No, not angry. Saddened perhaps. Exhausted maybe.
but if i said it's avery powerfull elian had created the earth ... i think they will buy that. - No, we wouldn't. That's really not what the science says and it wouldn't explain how the moon was formed from a collision between early earth and another Mars-sized planet. We don't need 'aliens with godlike powers' as a substitute for 'god' - we have strong evidence for a relatively mundane explanation that centers around stellar remnants, gravitation, that kind of thing.
i just need to know whats wrong with god theory ... - it's "Unfalsifiable". That means that there is no conceivable experiment that could be done to either prove or disprove the theory. The "god theory" is (scientifically) no more and no less probable or provable or credible than that I made the earth and have been keeping quiet about it all these years. There are literally an infinite number of unprovable ("wild-assed") claims you could make - they all have equal status with the "god theory" - and we can't go around believing in an infinite number of random things. On the other hand - we have an exceedingly good 'conventional' theory that works perfectly well without hypothesising supernatural causes. God simply isn't necessary for our explanation of the universe. You might like to read about Occam's Razor.
it might be right. - well, it might but so might be the theory that the Invisible Pink Unicorn (mhhbb) did it...or that roaming gangs of green furry fish did it. I can keep coming up with these stupid suggestions from now until doomesday - they are all just as valid as the "god theory" - there is the same amount of evidence that they are true (ie NONE) and just as easy to prove or disprove (ie IMPOSSIBLE). So why should we give the "god theory" a moment's more attention than the IPU (Invisible Pink Unicorn - mhhbb) theory - at least the incomprehensible but undeniable existence of pineapple and ham pizza provides at least a shade of evidence for the IPU? (I'm kidding - OK?)
but i think that humans dont like the idea of being a lower cretures ... - that's true. When I was a kid - the text books said "Humans are superior to the animals because we have language and use tools." - but then we discovered that bees have a language (involving dancing and wiggling their butts) - and lots of animals use tools (watch a starling breaking open a snail shell by hitting it with a pebble). So the next generation of textbooks said "Humans are unique because we MAKE and use tools."...but then we found that chimpanzees strip the leaves off of thin branches to make tools for getting ants out of termite mounds...and there is a fish that cuts and shapes leaves to make a disguise that it holds over it's body so that birds can't see it swimming by. We are clearly at the 'top of the heap' - but reality keeps reminding us that we're really not that much more superior to the "lower" creatures.
we are so pride to be god slaves,we need so much to belive that there's no destiny ,so we can make our own. - I certainly don't want to be a "god slave". I couldn't imagine what it would be like to believe in all that stuff. To have to continually bow down to an infinitely superior being? Urgh! We have not made up all this stuff we've found out about the universes. We've investigated what the universe has to tell us. We know the Big Bang is true because (in a sense) we sent up a spaceship to take a photo of it! The cosmic microwave background is the clearest proof that the Big Bang really happened. If you take the time to understand the science behind it - you'll be convinced too!
human evolved from monky...monky evolved from (whay ever)...all the way to the creation of the universe ... from where did the universe came from ... from where that gas came from ... what is the first thing ... what is ground zero. - Ground Zero is the Big Bang. We're pretty solidly clear on everything that happened from then to now. What we don't know - and what (if you must) you could attribute to a "God" is what actually caused the Big Bang in the first picosecond of the life of the universe. I don't think we need a supernatural explanation for that - but if you must, you could imagine a god who decides to make the universe and after about a picosecond - steps back and lets it all roll out without touching anything after that. This makes a sort of sense I suppose. It's a "God of the gaps" argument. Wherever we don't yet have a scientific explanation - you can stick God in there. Sadly, those gaps are getting smaller every year. Science is making huge leaps in figuring this stuff out - and every time we plug a hole, there is less need for a god to make a workable explanation. Give it ten years and the role of god will have shrunk from a picosecond to an attosecond. But this raises a bigger question for me. You aren't prepared to accept that the "Big Bang" came from nowhere (despite good evidence pointing that way) - yet you are entirely happy to accept that God "just is" - nobody asks "what is the origin of god?"...but if we were (as scientists) to accept the god-theory, that would have to be the first and biggest new question. "Where did God come from?" When I ask that question, I get some vague hand-wavey thing about him always having been there - or "He's outside of time and space". But when I say that time actually started with the big bang - and that it's meaningless to ask what came "before" - you get all huffy about it and start demanding why I don't have an explanation. Your theory is certainly no better than mine - and Occam's razor says it's a lot worse because it involves a whole extra step that my explanation doesn't need.
and if there is no god , and all this religion thing is just acrap,then i think the best thing that happened to the earth is hetler...we must let the smartest,the strongest , the healthiest ones to survive - but that's not true. Hitler's actions were not acceptable to the majority of humanity - or even to his own people when they finally realised what was happening. So Hitler was attacked from all sides - Europe, Russia, the US...and driven to extinction. He died because the majority of humans could not accept his behavior. That's because we've evolved a mental capacity to reflect the feelings of others - that capacity means that we can put ourselves into the positions of the poor people in those death camps - and we become outraged and belligerent - and we fix the problem. That's an evolutionary response to a failed genotype. Religion had very little to do with that. Plenty of atheists fought against Germany.
who cares about moral standards ,we invinte these standards,and we can change them - some we can - others are so inbred into our genetics that we can't. You can't just decide to do something that's morally repugnant to you. I could no more kill my son than I could kill myself. That's not a matter of logic - it's a matter of what my brain chemistry has made me be. We are like we are because of the genetics of being a "pack animal".
i think it's inmorale to leave the weak alife so they can multiply and reduce the chances of our survive,we should eliminate them. - you say that, but I doubt very much that you'd be able to carry it through. I have no god commanding me not to do that - and I certainly give money to help the needy - I volunteer to help out underprivilaged kids - I donate my time free to answer people's questions here on the Wikipedia reference desks. Without a god - your claim is that I should have no reason to do those things...yet I do! Gladly. For the betterment of mankind - for the survival of the species - for the survival of my genes into future generations. This is a moral standpoint for sure...but one that does not in any way rely on religion to prop it up. I actually agree with most of the more important of the Ten Commandments (although one or two of them are a tad nutty). "Thou shalt not kill" works very well for me! In fact, I'd prefer to avoid the weasel-words added to that that say "oh...unless it's a war or something...or maybe murderers could have the death penalty...and in Texas it's OK to shoot burgulars". No - for me, "Thou Shalt Not Kill" actually means what that bloody stupid book says it does. Not because there is some old white guy up in the clouds somewhere telling me to...it's because my brain tells me that killing (in general) is not a good thing. I have moral principles...pretty strong ones actually. They just don't derive from religion.
and why do we evolve to have this huge power of thinking ... - it helped early humans to be smart. The smartest ones didn't get eaten by the sabre-toothed tigers - so they had more kids - who inherited their parent's smarts - and gradually, via the relentless force of evolution we evolved to what we are now. It's not in any way a mystery.
were we to needy to find answers for the question we had before we have the mind to ask.whats the need driven us to evolve to have this huge brain ... food ..??? - Sex, actually. But food also.
will .. after all evry thing could be true , just leave the door open. - No. It's ridiculous. I don't have the time to go around believing in green furry fish that MIGHT have created the universe - I don't have time to believe that there MIGHT be a teapot orbiting Mars right now. I don't have time for any of the hundred or so wildly different supernatural claims for a "god" or "gods" either. It's unnecessary and (frankly) ridiculous.
Yes, that's right, although we have little or no idea what was going on just before that expansion started (or even immeadiately after it - there is a fraction of a second at the beginning during which our physics breaks down). --Tango (talk) 17:46, 20 March 2009 (UTC)[reply]
'mhhbb' stands, I believe, for 'may Her Hooves be blessed' and is a standard phrase when referring to Her. 'bbhhh' ('blessed be Her holy Hooves) and 'mhhnbs' ('may Her Hooves never be shod') are also in use. 'mtasnro' is a new coining standing for 'may Their ant supply never run out' and is a phrase used to propitiate the pink aardvarks who run the universe. Algebraist19:02, 20 March 2009 (UTC)[reply]
Thanks much for the info, faithfully recorded in my notebook! After Steve's analysis on the chances of being killed in a meteorite strike a while ago, I'm taking no chances on suddenly being called to the "undiscovr'd country from whose bourn no traveller returns". 'Scuse me now, I have to run out and find a goat, a virgin, a 100-foot tall flammable man-like structure and some chicken bones before nightfall. Oh yes, a box of ants too. :)
And to get even more sidetrack-ey, what's the name for when you find only one instance of a Google search term? Of course, when you report it, it then shows up twice. You were oh-so-close there! :) Franamax (talk) 22:43, 20 March 2009 (UTC)[reply]
I get the feeling a lot more evolving of this power of thinking is needed. Or perhaps by then we'll all have evolved so the muslim faith or whatever is bred into our genes. Then nobody will have to ask - we'll all 'know' without any evidence just like the OP. Wouldn't that be a grand fate for our descendants. Dmcq (talk) 15:30, 23 March 2009 (UTC)[reply]
the iron content in steel wool lab queries
for an important lab we're doing titled "percentage of iron in steel wool", a sample of steel wool is placed in excess dilute sulfuric acid, and this supposedly converts the iron present in the steel wool into Fe2+ ions......then, the Fe2+ ions in the solution are titrated against a standard permanganate solution, and thus are further oxidised to Fe3+ ions, while the permanganate ions are reduced to Mn2+ ions..
do you have any idea of the kind of questions that are likely to be asked of me in this lab? also, i'm assuming my teacher will give a 'manufacturer's value of the % Fe'. do you know the equation to figure out the % difference between your value and the manufacturer's claim?
Percent difference? That's a pretty technical article, but the essence is in the "Percent error" formula and the intro: it's a ratio of the difference between the values to the values themselves. You might take one value as "correct" and thus compare to it, or you might just take them both as "someone's data" and consider the average of them to be the value to compare. I would ask a student to write the net ionic equations for the redox reactions involved in this experiment. DMacks (talk) 04:56, 20 March 2009 (UTC)[reply]
You're likely to do stoichiometry calculations somewhere to figure out the mass of iron in your original sample. This can be done any number of ways, but since Fe3+ ions are colored, you could use a spectrophotometer, a series of standardized Fe+3 solutions, and Beer's law to calculate the concentration of Fe+3 ions in your unknown solution. Then, knowing that concentration and volume, you can find moles of Fe3+, which should ALL have come from the steel. You could also do the same via titration with a standardized KMnO4 solution; if you know the volume and concentration of the KMnO4, and have a balanced chemical reaction for the Fe+2/Fe+3//Mn+7/Mn+2 redox reaction, you can also quantitatively find the moles of iron in your unknown, and then its the same calculation as above. --Jayron32.talk.contribs05:03, 20 March 2009 (UTC)[reply]
potential energy
I was watching TV where i saw a man working in a high way project , this man was trying to crack a big rock , he kept hitting the rock with a hummer until and suddenly it just split into half , i asked about it and get some opinions like a potential energy is being stored in the mass until its enough to crack the mass,
but i think that the hummer is producing a hairy cracks at aspecified plan until its reach that critical edge where it to weak to resist that hit energy , so it jut crack down,what did you think....? —Preceding unsigned comment added by Mjaafreh2008 (talk • contribs) 10:24, 20 March 2009 (UTC)[reply]
The rock is certainly not storing significant energy from the hammer blows. It's much more likely that each blow (or even only some of the blows) create and propagate cracks and fissures, gradually weakening the rock. At one point the rock is weak enough that the last blow splits it. --Stephan Schulz (talk)11:12, 20 March 2009 (UTC)[reply]
As a professional rock splitter, I concur with that. When trying to break up a rock down to a size that you can take back as a specimen you generally concentrate your hammering on any obvious existing weakness such as a crack or a weathered zone. Normally you can see, feel (from the change in the response of the hammer handle) or hear (a change in the sound of the blow) when you've started to propagate a crack just before it finally splits. Mikenorton (talk) 11:24, 20 March 2009 (UTC)[reply]
You could argue that a rock with cracks in it has higher energy that one that doesn't (in the same way that two separate atoms have higher energy than when they are bonded together), but there is no way easy way to get that energy back so I'm not sure I'd call it "potential energy". --Tango (talk) 12:17, 20 March 2009 (UTC)[reply]
I'd bet that you're actually releasing energy in the rock by breaking bonds - but the biggest part of what your hammer blows are doing ends up as heat or sound energy (which in turn is going to be heat energy pretty soon). When you hit the rock - you are causing it to vibrate or accelerate (briefly) - and that's getting turned into heat by friction. So to the extent that the rock gets a bit warmer (and most certainly the hammer does - you can feel it!) you are storing energy in the rock - but not usefully. SteveBaker (talk) 13:14, 20 March 2009 (UTC)[reply]
During the recent gasoline price spikes, I imagine quite a few people "kept hitting a rock with their Hummer until suddenly it just split in half". I'm not sure if the junkyard would take half a Hummer, though. :-) StuRat (talk) 04:13, 22 March 2009 (UTC)[reply]
Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. SteveBaker (talk) 13:08, 20 March 2009 (UTC)[reply]
Transcription (genetics), Translation (genetics) look promising and weren't that hard to find. (Click on words in blue in a text on wikipedia and it will get you to the relevant page.) If the assigned textbook for your class doesn't give you good enough answers it might be useful to check if you have a well stocked library in the area. 76.97.245.5 (talk) 14:32, 20 March 2009 (UTC)[reply]
Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. SteveBaker (talk) 13:08, 20 March 2009 (UTC)[reply]
Yes, wikipedia knows. Here's how you can find out what: copy your word into the white box underneath where it says "search" in the left hand sidebar near the top of this page. Then click on "search". If you can't find a relevant page or have trouble understanding some of the content, please feel free to come back with a specific question. 76.97.245.5 (talk) 14:23, 20 March 2009 (UTC)[reply]
Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. SteveBaker (talk) 13:09, 20 March 2009 (UTC)[reply]
Yes, wikipedia can help. Here's how: copy your word into the white box underneath where it says "search" in the left hand sidebar near the top of this page. Then click on "search". If you can't find a relevant page or have trouble understanding some of the content, please feel free to come back with a specific question. 76.97.245.5 (talk) 14:19, 20 March 2009 (UTC)[reply]
If you put solar panels on windmills, could they help increase the energy given to the town or city or whatever the windmill's powering? What would you connect the solar panels to? <(^_^)> Pokegeek42 (talk) 17:38, 20 March 2009 (UTC)[reply]
I think putting the panels on the ground would be the best way to use the same space for solar and wind power. The alternative is putting them on top of the turbines (thus avoiding shadows being cast on them), but I suspect that would mess with the aerodynamics of the turbines and make them less efficient (whereas the shadows should be a mini\mal concern - turbines are pretty thin). --Tango (talk) 17:44, 20 March 2009 (UTC)[reply]
In terms of an individual windmill, its probably not all that efficient, but in terms of a national energy policy; diversifying one's energy sources is a sound idea. Generally, solar power is most productive at times and places quite different from the times and places where wind power is productive. Thus, they tend to complement each other as a source of power, but mostly so on a national rather than individual scale. In general, one windmill or a single solar panel running a single house, or even one of each, is a fantastically wasteful and inefficient way to do things. It would be far more efficient use of resources to provide power via Wind farms and Photovoltaic power stations. --Jayron32.talk.contribs17:54, 20 March 2009 (UTC)[reply]
What an impressive generalisation, but it just squeaks through as accurate but very misleading. In general a small number of solar panels in a house is a pretty efficient way to provide thermal water heating as a top up to other energy sources. Solar for the summer and a wood chip boiler in winter is fine for all year domestic heating. Plenty of people use wind and wood for heating too (but not city ants). Local solar panels are also very efficient to provide local summer heating for things like domestic swimming pools. Only if you convert solar or wood to electricity (at massive inefficiency) does it look very uneconomic at home and equally it looks uneconomic for most climates as Photovoltaic power stations. The trade off between economic of scale and transport cost and loss depends on many things and is not obviously one way or another. --BozMotalk18:37, 20 March 2009 (UTC)[reply]
When you consider transmission losses, local generation starts to look much better. But one windmill, even a utility scale one does not provide much area for the very inefficient photovoltaic power panels. You might get enough panel on the nacelle to get power one home. Rmhermen (talk) 19:25, 20 March 2009 (UTC)[reply]
However, covering the ground at a wind farm with solar panels might work quite well - wind farms are generally quite spread out and the area is often not used for anything else, as far as I know. --Tango (talk) 19:49, 20 March 2009 (UTC)[reply]
The windmill farms I've seen in the desert are not used for much, but the ones I've seen in the plains are used for cattle. Replacing their grazing land with solar panels will mean that the cattle need to graze elsewhere. Also, windmills require a lot of maintenance. It will be hard to work on one if you have to move a lot of solar panels out of the way first. -- kainaw™20:46, 20 March 2009 (UTC)[reply]
In Denmark, on-land wind turbines are quite commonly located on rural land and farming happens right up to the footprint of the turbine foundation itself which I believe is between 12 and 20 feet square. (And obviously the pathway needed to bring the maintenance equipment in counts as footprint too, but farmers need laneways for tractors anyway).
More desolate land, esp. deserts are good candidates for solar and mountains for wind - but yes, transmission losses, construction expense and bio-effects for the transmission lines come into play. There is a lot to be said for generation near to consumption, not least of which is grid stablization. If clouds pass over a remote solar plant or the wind calms at a wind-farm, everything in between supply and demand will see voltage effects, possibly quite severe. Franamax (talk) 22:54, 20 March 2009 (UTC)[reply]
The problem is that this idea is solving a non-problem. The problem with solar panels isn't in finding land to put them on. In all the places with the largest amount of sunshine, land is cheap. Deserts and prairie is easy to get for a couple of hundred bucks an acre. Compared to the cost of an acre of solar panels, the cost of the land is quite utterly negligable. So there is no need to make special considerations for putting them near windmills. To the contrary - you place windmills where the wind is good - you place solar panels where the sun is good - going out of your way to put one in the same place as the other is unlikely to be optimal. SteveBaker (talk) 23:35, 20 March 2009 (UTC)[reply]
The solar panels on windmills idea would be more of a benefit to home windmills, where space might be limited and trees and the house may cause shadows to fall on panels placed on the ground. If the windmill is on a tall mast, solar panels near the top would get more sunlight (the additional weight and wind-load might require a stronger mast, though). They could also be placed on the blades. In this case, the electricity could be transmitted from the moving blades to the rotating mast via brushes or some other method. StuRat (talk) 04:06, 22 March 2009 (UTC)[reply]
But that's a dumb idea...the windmill has to face into the wind - and the solar panels have to face towards the sun. Since there is little correlation between the two - you'd expect that either your windmill or your solar panels would be pointing the wrong way at least half of the time! Again, the limiting factor with solar panels isn't available area. Almost all houses have FAR more available roof area than the owner can afford to populate with panels. Going to all that grief to put a handful of solar cells onto the blades of the windmill (making them heavier - and therefore harder to get spinning in a light wind - requiring brushes to extract the power - which will inevitably add to the frictional forces - worse still - you are incurring all of those penalties during the night when the solar panels aren't paying for those additional costs!)...and all for what? About another three square feet of panels that's hardly ever pointing optimally? When did you last see a roof so packed with solar panels that another 3 square feet of them would be so urgently needed?! This is a STUPID idea....period. SteveBaker (talk) 19:39, 22 March 2009 (UTC)[reply]
Then there's the problem that the house roof may be in shade in areas with tall trees (like my house), so not at all suitable for solar panels. Also, there may be a minimum amount of electricity required for a house, and any beyond that may be wasted (if there's no way to sell it back to the power companies in that location). In such a case, pointing the blades either at the wind or Sun may be enough. When there's no sunlight, point it into the wind. When there's no wind, point it into the sunlight. When there's neither, you're out of luck. StuRat (talk) 03:43, 23 March 2009 (UTC)[reply]
You've still greatly added to the complexity of a device that already is unlikely to pay for itself. If your solar panels need to be up on a pole, it'd probably be better to put them on their own pole.
You probably could think up some contrived hypothetical situation where a solar windmill would make sense, but you'd really just be searching for a problem to your solution. APL (talk) 12:52, 23 March 2009 (UTC)[reply]
Russell Watson Brian Tumor
Hi
Do you know the name of the surgeon who performed Russell Watson's brain tumor operation at the Alexadra Hospital in Cheadle (Greater Manchester) in 2007? Many thanksCarlchester (talk) 18:34, 20 March 2009 (UTC)[reply]
Assuming of course that the surgeon has not moved on in the meantime and / or that the list is otherwise up to date - I note that a surgeon who operated on me is still listed on the hospital (I went to) pages, despite being suspended from the GMC :( 78.151.212.201 (talk) 21:59, 21 March 2009 (UTC)[reply]
Should I add this to an article? Electrolyzed water applications
This Reuters article caught my eye because I was just reading about other uses for Electrolyzed water. (Just ignore the snake-oil bits, I'm talking about mainstream uses like hospital disinfectants)
The Reuters article talks about using "electrolysis and ultra-low frequency waves" to raise sea water pH to 10 then spraying it in a scrubber stack to knock down soot, SoX, NoX and CO2 in ship exhaust. I wonder if it would also knock down heavy metal emissions, bunker oil being about the dirtiest thing in the world. The method described sounds very much like the process for producing electrolyzed water in commercial applications. (Again, I'm not talking about bottling it and scamming people into drinking it)
My request here is for some sage observers to look at the Reuters and wiki articles and tell me if it would be appropriate to add some verbiage and source to our wiki article to describe this use. And/or feel free to add it yourself!
I can't figure out the ultra low frequency wave bit. About the only thing I can think of is an ultrasonic cleaning effect, but the frequencies used for ultrasonic cleaners are far from "ultra low." (unless they're comparing sound frequency to light frequency but that doesn't make much sense). If the correspondent doesn't have a strong background in science (I have no clue about this guy), another possibility is that he could have messed up somewhere in the terms or facts so ultra low frequency waves refer to something else. Without putting too much thought into this, the alkaline electrolyzed sea water is basically a bleach solution. Perhaps the concept is to oxidize the NO2, N2O, and NO to NO3- and the SO2 to SO4-2? The CO2 I suppose would be removed when it dissolves in the alkaline water to form Na2CO3. I'm a little surprised because the calcium present in sea water would produce CaCO3 which would build up as scale over time which wouldn't seem good for a ship. I am not sure about heavy metals. If they dissolved into the alkaline bleach water it would need to be treated to remove the metals before dumping it back into the ocean. Sifakatalk23:15, 20 March 2009 (UTC)[reply]
There is some more verbiage on the website of Ecospec, the company that is marketing this thing. It sounds suspiciously like those gadgets that you attach to the fuel line in your car, that are claimed to improve your fuel efficiency, and has a familiar lack of any numbers or measurements. Caveat emptor. --Heron (talk) 12:30, 21 March 2009 (UTC)[reply]
March 21
Olaflur
What exactly is olaflur and how effective is it compared with the other forms of fluoride for teeth? Any disadvantages (human toxicity, environmental, etc)? —Preceding unsigned comment added by 79.107.234.164 (talk) 01:25, 21 March 2009 (UTC)[reply]
Our article olaflur will tell you exactly what it is (it is N,N,N'-tris(2-hydroxyethyl)-N'-octadecylpropane-1,3-diaminium difluoride) but will not, alas, answer your other questions. Algebraist01:33, 21 March 2009 (UTC)[reply]
Thank you Algebraist, I have read that, as I have searched in many different sites all of which have the excactly same info as in the article you mentioned. I am particularly interested in the advantages/disadvantages that it has, how it compares with the othe fluoride forms for dental use, it's hazard-toxicological profile and any concerns/other issues about its use. Thanks again though! —Preceding unsigned comment added by 79.107.234.164 (talk) 01:41, 21 March 2009 (UTC)[reply]
Is there a scale that measures how sweet something tastes, similar to how the Scoville scale measures heat? The closest thing I found is the Brix scale, but that doesn't seem to directly measure sweetness. --Ixfd64 (talk) 02:11, 21 March 2009 (UTC)[reply]
For the sweetness scale see e.g. this. I don't think the scale is named after anyone, though; or at least I am not aware of such a name. --Dr Dima (talk) 09:20, 21 March 2009 (UTC)[reply]
Balling, Brix, Oechsle scales all measure specific gravity, and do not measure sweetness directly. In other words, they only indicate concentration of the sugar (sucrose) in the solution, and do not indicate how sweet other substances are compared to sucrose --Dr Dima (talk) 06:46, 22 March 2009 (UTC)[reply]
cacti
Can anyone identify these cacti? Scale is that they are about 2.5" across, and the flowering one is 3.5" tall. Also, would these do ok with only office florecent lights, or do they need actual sunlight?
A Mammillaria sp. perhaps? If I remember correctly the species in this genus can sometimes be tricky to identify. One website suggests partial shade (Filtered sunlight or direct sun for only a few hours) and watering it weekly. Sifakatalk06:04, 21 March 2009 (UTC)[reply]
Why does the depth of field depend on aperture diameter of a lens? I am a bit confused. Aperture is to control the amount of light entering the lens. If I make my aperture smaller, the less light should enter, but focal length is still the same, so how does it affect the depth of field? Thanks. - DSachan (talk) 16:27, 21 March 2009 (UTC)[reply]
It's because aperture appears in the formula for Hyperfocal distance. I have no idea why that is, though! (Our article doesn't seem to explain the formula much.) Hopefully someone more knowledgeable will come along soon... --Tango (talk) 16:40, 21 March 2009 (UTC)[reply]
Actually, after thinking about it, I think I have it - the circle of confusion is going to depend on aperture (in fact, I suspect it is proportional to it), since that confusion is caused by light passing through different parts of the lens ending up at different points on the screen. How far apart those points are is going to depend on how far apart the bits of lens in question are, and a bigger lens allows for greater distances between parts of the lens and so greater confusion. --Tango (talk) 16:44, 21 March 2009 (UTC)[reply]
The diameter of the circle of confusion is proportional to the aperture diameter, and there's an easy way to see that. Assuming an ideal lens, all light rays emitted from a point in the focal plane and passing through the aperture will be focused onto a single point of the detector. Any light emitted elsewhere along the path of that ray, in the same direction, will end up at the same point. So that point on the film will show features lying within a double cone whose base is the aperture and whose apex is the point in the focal plane. A flat object at a certain distance from the focal plane will be blurred by convolution with the aperture scaled by (distance from object to focal plane / distance from aperture to focal plane). This also shows that the "circle" of confusion is really an image of the aperture, and is only circular if the aperture is. -- BenRG (talk) 18:10, 21 March 2009 (UTC)[reply]
With a pin-hole camera - which is a lot easier to think about that the ones with lenses and mirrors and stuff - the smaller you make the pinhole, the better the depth-of-field (but the less light you get in - so the longer the exposure times you need). In the limit - if you imagine a pin-hole camera with an infinitely small hole then every ray of light from everywhere in the world would have to pass through that infinitely small hole in order to hit the film. But only ONE path for that ray is possible. Light (basically) travels in straight lines - but you can only draw one line that goes from some point in the world, through that infinitesimal hole and onto the film. So a perfect pinhole camera has perfect focus from zero to infinity for an infinite depth-of-field. But now imagine a pinhole camera with a 1cm "pinhole" (more like an "ice-pick-hole camera!") - now, the light from a particular point in space can go through the extreme left side of the hole, the extreme right, the top, the bottom, through the middle - or anywhere inbetween. Each of those rays hits the film at a different place - so you get a fuzzy image. If the film is very close to the hole - then a 1cm hole will produce a roughly 1cm blur around a point-sized object in the world. If the film is further away from the hole, then the blurry region will be even bigger. But a perfect pinhole camera has perfect depth of field and everything is always in focus...it just takes you an infinite amount of time to capture the image because you have an infinitely small hole for the light to pass through!—Preceding unsigned comment added by SteveBaker (talk • contribs) 14:14, 21 March 2009
Now you know about that blow your mind out trying to understand Qinitiq's system desribed in [[4]] which can keep the information from different distances sharp. Dmcq (talk) 23:47, 21 March 2009 (UTC)[reply]
No, a metal halide light does not need a high voltage pulse to ignite it, but may need a transformer to convert to the correct voltage. Metal halide lamps may work off the full mains voltage. Graeme Bartlett (talk) 21:20, 21 March 2009 (UTC)[reply]
That is not correct, Graeme. All HID lamps require a ballast, including HPS and MH/CMH lamps, and all require a high-voltage pulse to strike (initiate) the arc. They do not operate directly off mains voltage. Different ballasts are generally required for MH vs. HPS, because of the different run-up and operating voltage requirements; mixing and matching makes problems ranging from the costly and inconvenient (early failure of lamp and/or ballast) to the extremely dangerous (catastrophic lamp failure). However, there are now on the market various "smart" ballasts compatible with more than one type of lamp, usually HPS and CMH. They detect the current draw characteristics of the lamp during run-up, and since these characteristics are peculiar to the different lamp types, the ballast is thus able to "know" what the lamp wants to see in steady-state operation. We presently have two relevant articles, High-intensity discharge lamp and Gas-discharge lamp, though a merger has been proposed. —ScheinwerfermannT·C22:07, 21 March 2009 (UTC)[reply]
Is this Munchausen, or...?
Okay, so if a person knowingly fakes/exaggerates illness/distress, they would be described as having Munchausen disorder; if they create or fabricate illness/distress in a dependent, Munchausen by proxy; do either over the internet, Munchausen by internet. But if a person who engages in all three of the above also mimics real diseases/distresses of their dependents, does that also fall under Munchausen? What if they are a parent who is chronically negligent to an extent that their child(ren) encounter numerous, potentially life-threatening accidents, yet makes no attempt to be less negligent and revels in the attention that results from the child(ren)'s accidents? And what would you call it if said parent, in a fit of new-found religion, demanded that medical personnel announce a miraculous recovery (in the same manner that a standard Munchausener might demand medical treatment), which resulted in the continuation of an injury of the patient that would have otherwise been corrected or at least improved, as a way to self-confirm their religious ideas (note, this would not be in absence of the Munchausen/by proxy/by internet, but rather alongside it...and the treatment avoided by the "miraculous recovery" ultimately causes the injured party permanent disability)?
Munchausen's, and related diagnoses, are extremely controversial - it's not at all clear what (if anything) distinguishes between someone who abuses themselves or others in a medical context and someone who has Munchhausen's. (In other words, couldn't a diagnosis of "Bank Robber Syndrome" be assigned to anyone who robs banks). There are certainly those who claim that Munchausen's simply does not exist, and others that it is greatly overdiagnosed. At best we can say that empirical diagnostic tools for making even a tentative diagnosis are pretty dismal, so parsing the more complex examples you cite seems beyond current analysis. 87.114.29.204 (talk) 20:20, 21 March 2009 (UTC)[reply]
The bible of mental disorders (the DSM-IV) doesn't even list Munchausen - let alone all of these complicated variations. I agree with '87 - this is controversial at best. SteveBaker (talk) 00:36, 22 March 2009 (UTC)[reply]
Thanks Steve, do you think the refusal of medical treatment in order to force confirmation of religious beliefs would also fall under that category, though? bcatt (talk) 05:50, 22 March 2009 (UTC)[reply]
No! The diagnostic criteria is that the person with the disorder wishes to be treated as if they were sick - or in the "by proxy" version wishes someone they care for be treated as if sick. Refusing treatment to someone who actually IS sick (for whatever reason) doesn't sound to me like the same kind of thing at all. I agree with the subsequent posters - sometimes a jerk is just a jerk. SteveBaker (talk) 19:31, 22 March 2009 (UTC)[reply]
Basically we're talking about where you draw the line between a "bad person" and a "mentally ill person that does bad things". I've never really known how that is supposed to work... --Tango (talk) 01:12, 22 March 2009 (UTC)[reply]
People who are rich enough to afford doctors who can make a diagnosis are mentally ill. Everyone else are just healthy people who make bad choices. --Jayron32.talk.contribs02:22, 22 March 2009 (UTC)[reply]
That would seem to suggest that everyone who behaves badly in countries with "free" medical care is mentally ill, and there are no healthy people who have made bad choices in such places. One might conclude then that socialized medicine causes mental illmess, or even that it cures choosing badly. // BL \\ (talk) 04:45, 22 March 2009 (UTC)[reply]
I am personally in Canada, and we have universal health care. I can assure you that many mentally unstable people access the free health care here. Doctors make money from the pharmaceutical companies every time someone fills a prescription, so it's really not that hard to find a doctor who will play along with a mentally unhealthy person's imaginary problems. Also, BL makes a very good point. And to Tango, I would think that all "bad people" have some sort of mental disorder, no? I don't understand the distinction you're trying to make. bcatt (talk) 05:50, 22 March 2009 (UTC)[reply]
When people are mentally ill we don't punish them for their actions or put them in secure mental facilities. When people are just bad we throw them in prison. (That's an oversimplification, obviously, but you get the point.) I'm not the one making the distinction. I agree with you that such a distinction doesn't make much sense - that was the point I was trying to make. --Tango (talk) 13:14, 22 March 2009 (UTC)[reply]
Of course, my response above was somewhat of an oversimplification, but it comes from a basic problem with the mental health industry, indeed one which Tango has aluded to. The deal with most mental illness is that there is a lack of mechanistic explanation for it. If I have diabetes, its because my pancrease doesn't work right. If I have AIDS, I have a virus in my system which is causing it. If I have ADHD, it means I display a set of behaviors, but what is the underlying physical cause of this?!? See, there's the crux of the problem. Diseases have causes which can be identified. Mental diseases, mostly, are about a set of causeless symptoms; so what sepereates a person who chooses to behave badly from one with a mental illness is simply the existance of a doctor willing to provide the diagnosis. Now, don't get me wrong, there are real mental illnesses. I understand this; however there are also a vast number of people who are overdiagnosed with them, because there is no way to distinguish between people who make bad choices and people who are incapable of making good ones. It;s a shame, because it swamps the system with people who don't need treatment, and reduces the quality of treatment to people who really need it. So people with access to the doctors to make the diagnoses get labeled "unable to make good choices" and those people without get labeled "people who make bad choices". It is unclear what is wrong inside of their bodies that distinguishes one group from the other... --Jayron32.talk.contribs01:07, 23 March 2009 (UTC)[reply]
Ok, I have a lot easier time agreeing with you on these points. Coincidentally (or not), ADD/ADHD appears to be one of the favourite diagnoses of the type of parent that I've described, as well as of every damn teacher out there who expects a child to engage in the completely abnormal behaviour of sitting at a desk for 7 hours 5 days a week...it's simply unnatural. bcatt (talk) 16:19, 23 March 2009 (UTC)[reply]
March 22
Pick on somebody your own size...
Why is it that the largest animals, both on land (elephants) and in water (whales), don't have any natural predators (other than man, that is). I'm talking about adult animals here. So, why isn't there a predator (or group of predators) large enough to take on an adult elephant or adult blue whale ? Somehow the upper size limit for predators seems to be lower than for other animals, but why exactly is this ? StuRat (talk) 04:23, 22 March 2009 (UTC)[reply]
If the largest animals in the world were predators, they would quickly outstrip their food source, and then ensure their own demise. The situation is not unique to modern times, Tyrannosaurus, one of the largest predators ever, was still dwarfed by contemporaneous herbivorous dinosaurs; probably on a scale similar to the size difference between the largest predators and herbivorous animals today. Incidentally, Blue Whales are technically meat-eaters; they subsist on Krill, which is definately not a plant. --Jayron32.talk.contribs04:41, 22 March 2009 (UTC)[reply]
Why couldn't there just be fewer in the predator species than their prey species ? I believe this is the normal situation in any predator-prey relationship. StuRat (talk) 04:47, 22 March 2009 (UTC)[reply]
Well, we could invent any situation we want to; except that time and time again, over history, the same patterns have emerged. We can justify these repeating patterns, by offering explanations as I have done, but offering counterexplanations (like "we SHOULD have really huge predators") doesn't make much sense, since it just appears to not work that way. Except that, as I noted above, the largest animal ever to have lived, IS A PREDATOR. Blue Whales eat other animals, live, which seems to me to be what a predator does... Even if you don't want to include that as a predator, you must admit that predators just AREN'T the largest critters in any environment and at any time, so explanations that attempt to say they should be must be flawed from the start, no? --Jayron32.talk.contribs05:09, 22 March 2009 (UTC)[reply]
Keep in mind that the larger the animal, the longer it takes to grow a replacement. In general, anyway. Preditors can eat rabbits all day long and the population will rebound quickly. If a theoretical uber-hunter ate all the elephants within its range in could be decades before they replenished. It seems like that would leave a very low margin of error for the predator-prey balance.
Incidentally, while adult elephants have no natural predators other then humans, juveniles are general vunerable to big cats although the social herd nature helps to protect them.. The same appears to be the case for mammoths and saber-toothed cats and one common believe is the demise of the mammoths may have played a role in their extinction, take a read of Homotherium and Smilodon for example. Homotherium in particular says
Friesenhahn cave in Texas contained the remains of over 30 H. serum individuals, which were discovered along with the remains of between 300 and 400 juvenile Columbian Mammoths (Mammuthus columbii).[6] Besides mammoth, very few other potential prey species were found in the cave - it is therefore unlikely that Homotherium carried scavenged carcasses of already dead animals to the cave. Such specialization on prey of a particular species and age structure is not covenant with a scavenging lifestyle. For the same reason it is also unlikely that the dire wolves carried the mammoths into the cave.
Wow, they are 1/25th the mass, so that would seem rather ambitious. That's worse than a house cat hunting an adult human. StuRat (talk) 17:22, 22 March 2009 (UTC)[reply]
I think that they only go for the calves and they do hunt in packs, so maybe not so ambitious, although such attacks are said to be rare in our article. Mikenorton (talk) 17:37, 22 March 2009 (UTC)[reply]
Still, there have been cases where a dog of a similar size to a housecat has managed to kill an adult human. I'm not entirely certain - but I think that killer whales are much faster and more manoeuvrable than blue whales, and they are (obviously) much more aggressive. Blue whales are huge, yes - but I'd imagine that taking a chunk the size of a killer whale's mouth out of the body of one would cause it to die. --Kurt Shaped Box (talk) 22:33, 22 March 2009 (UTC)[reply]
There are plenty of ecosystems where the dominant predator is also the largest animal. The Killer Whale eats penguins and seals - and is easily the biggest animal that lives (continuously) in those areas. I doubt that in regions where the Great White Shark lives has any animals that are any larger. Ditto Polar Bears, ditto Grizzly Bears. I think there are plenty of ecosystems where the predator is the biggest creature around - and plenty of others where it isn't - it seems fairly random to me. As for the evolutionary pressures - I agree with the earlier respondant - if an easier living can be had hunting rabbits - why go after elephant? If the only herbivore was the elephant - then probably the carnivores would evolve to take it down. But generally a pack of animals is better at doing that...and for that, size isn't everything. SteveBaker (talk) 19:26, 22 March 2009 (UTC)[reply]
Are you sure no whales live in those oceans ? And how about large land herbivores, such as elk and moose ? They seem like they might be too big to be prey for bears, at least the adult males. As for your "if an easier living can be had hunting rabbits - why go after elephants ?", the point is that the rabbit-hunting niche is already filled by well-adapted predators, while the whale- and elephant-hunting niches are wide open. StuRat (talk) 03:34, 23 March 2009 (UTC)[reply]
Healthy adult sauropods (of the 'giant' type), I'd guess not. I'll bet that there were plenty of predatory dinos that could and would take a young one, or finish off a sick one, though. Predators don't generally attempt to take on prey animals that look as though they might have a good chance of defeating them in combat unless they're really desperate for food. --Kurt Shaped Box (talk) 23:58, 23 March 2009 (UTC)[reply]
I have sprayed a Kaffir Lime tree with a pyrethrin product to eliminate a heavy infestation of red spider mites. Since I use the leaves in cooking, IS IT SAFE to eat the food cooked using these pyrethrin-sprayed leaves? Is there a period of time after spraying not to use them, and then it is OK?
Pyrethrins are amongst the safest pesticides available. Having said that I'm loath to pronounce anything completely safe. You should judge for yourself from the published information about them, here are a couple of links that discuss both direct exposure [6](i.e. during application) and safety as residue in food [7]. The conclusions seem to be that there are few definite health implications but the possibility of carcinogenesis has not been ruled out. Mikenorton (talk) 12:43, 22 March 2009 (UTC)[reply]
Next time spray the Kaffir Lime with plain water more frequently, two or three times a day if possible. Red spider mites hate moist conditions and will find it hard to survive let alone flourish. Richard Avery (talk) 08:30, 23 March 2009 (UTC)[reply]
In the instruction manual of your pesticide (or on the bottle) there is probably some direction about the use on food crops (which probably includes directions on long you have to wait). If not, at the very least there should be a telephone number for the manufacturer. I highly recommend calling them and asking their recommendation on the matter - especially with potentially hazardous things such as pesticides, I find that most manufacturers are happy to discuss how to use their product safely. -- 76.204.102.79 (talk) 03:19, 25 March 2009 (UTC)[reply]
Metal spoon in microwave
Hi. Sometimes we leave a metal spoon in our food when we put it in the microwave, and nothing happens, and the spoon is barely hot afterwards. Of course, the food must be full, solid, and in a bowl, and most of the spoon is immersed in the food so the microwave isn't heating *just* the spoon. Are there any risks that are unforseen with this practice, such as radiation being emitted outside of the microwave, or the spoon or the food storing excess radiation or an electric current, etc? Thanks. ~AH1(TCU)14:56, 22 March 2009 (UTC)[reply]
It does however say "Microwaving food containing an individual smooth metal object without pointed ends (for example, a spoon) usually does not produce sparking". There is a risk of shorting if the handle gets too close to the side of the oven. I can't see how any excess radiation or electric current could be stored. Mikenorton (talk) 15:25, 22 March 2009 (UTC)[reply]
Well, there are certainly situations when this practice is "A Bad Thing" - sharp metal objects concentrate the charge at their tips and can arc - that produces all sorts of nasty, toxic gasses that you really don't want in your food - also, metal objects positioned "just so" with respect to the microwaves resonant cavity can concentrate the heat in small areas resulting in food that's cool in some areas and dangerously hot in others - that can result in small explosions when heating liquids - it can also "short out" the magnetron to some degree which will shorten it's life and might even outright destroy it. However, there are other times when none of these terrible things can happen. However, the precise reason you get one outcome versus another depends critically on exact placement of the metal, its exact shape and the precise nature of the food (if any) around it. Since we mere mortals have ZERO 'gut-feel' for what's right and what's not when it comes to invisible & intangiable things like microwaves - putting metal that was not designed specifically to be there into your microwave - is just a dumb thing to do. It says that right there in the instruction book for your oven - and there is probably another sticker someplace on the door frame that says it again...they don't do that without a reason...so just don't do it - OK? SteveBaker (talk) 19:17, 22 March 2009 (UTC)[reply]
Let me reword the OP's question a bit to understand it a bit better... "See, this one time, I crossed a busy street wearing a blindfold and blasting my I-pod. I could see nothing, I could hear nothing, and there were like 100 cars crossing the street in front of me. And yet, I didn't get hit. Doesn't this mean that all the things I read about looking where I am walking and only crossing with the light are bullshit? Like, if I managed to cross the street with a blindfold and nothing bad happened, why is there all this fuss?!?". Seriously, putting metal in a microwave is ALWAYS contraindicated, even if occasionally nothing bad happens, it is NOT a habit you want to get into... --Jayron32.talk.contribs00:49, 23 March 2009 (UTC)[reply]
When I was a little kid, I saw a wildcat (Bobcat) in a cage at a roadside zoo. I stuck my finger through the chickenwire of the cage to tease the cat, and suffered no ill effects. Around the same time, I stuck my finger in a live electric socket, and suffered only momentary pain.Around this same time, while walking in high weeds in the southern U.S, I stepped on a snake (of unknown species) which thrashed around dramatically. Can we conclude from these anecdotal reports that these actions were a good idea? Edison (talk) 02:25, 23 March 2009 (UTC)[reply]
, still a spoon is a heck of a lot safer then a fork, so maybe the ipod was not on full blast and the blindfold let you get a glimpse of shadow vs light.65.121.141.34 (talk) 14:03, 23 March 2009 (UTC)[reply]
ATTN Steve Baker - do we really have complete dinosaur dna like in Jurassic Park?
Dear Steve Baker,
My question is: have we really got complete dinosaur dna like in Jurassic Park? Eventually, does it look like there is any reason we couldn't really hatch little dinos?
I'm not sure why you are specifically asking Steve, he wasn't a palaeogeneticist (is that a word?) last time I checked. I'm pretty sure we don't have a complete genome for any dinosaurs - they didn't even have one in Jurassic Park, they had to fill in the blanks with frog DNA (why they didn't use bird DNA, I don't know... probably because the plot wouldn't have worked!), or something, which is what caused all the problems. Our article, Dinosaur#Soft tissue and DNA, suggests we haven't even got a reliable partial genome from any dinosaurs (a couple of unreliable ones, though!). --Tango (talk) 15:33, 22 March 2009 (UTC)[reply]
I'm asking Steve Baker because he's the smartest and best-informed paleogeneticist in existence -- paleogeniticists might not exist as a profession, yet Steve Baker would be the best qualified of them all (if not best-credentialled). Thank you for the link. However, with the above points in mind, I will wait for Steve Baker's verdict. Thank you! 94.27.132.205 (talk) 15:46, 22 March 2009 (UTC)[reply]
Steve is very well read and an excellent researcher, but what gives you the idea he's a well qualified palaeogeneticist? --Tango (talk) 16:20, 22 March 2009 (UTC)[reply]
(edit conflict)Even with an animal as geologically recent as a mammoth, paleogeneticists (6660 ghits BTW) have only assembled part of the genome and in this BBC article [8] Dr Gilbert of Copenhagen's Center for Ancient Genetics says that even if we had the whole genome "technology does not currently exist to turn that biochemical information into a live animal". Mikenorton (talk) 15:50, 22 March 2009 (UTC)[reply]
If you really are only interested in answers from Steve Baker, then you should ask this Q on his talk page, not here. If you want answers from everyone, then post here, but don't address those Q's to any particular person. StuRat (talk) 16:02, 22 March 2009 (UTC)[reply]
We barely have a complete human genome, and there's no shortage of fresh, brand new, human blood. Only very tiny, and (obviously) very old samples of dinosaur blood and soft tissue have been recovered. It's not clear if it's even theoretically possible to extract a complete dinosaur genome from these samples (It's possible that the information we'd need simply doesn't exist anymore.), but even if it is, we'd need technology much more advanced than we've got now. APL (talk) 17:10, 22 March 2009 (UTC)[reply]
I certainly feel like Moses and maybe shouldn't be asking back, but although I understand #1, could you explain the reasoning for #2? I mean, "eventually" is a long time, even if we had to combine 100,000 bits of DNA, there ARE that many in total waiting to be unearthed, no? Couldn't they be combined? If all you have is a very poor (less than VGA) webcam and want a super-super high-resolution scan of something -- couldn't you get it through 100,000 passes? Or in this case, you would have 100,000 deteorated photographs, coudln't you come up with the original based on all that? —Preceding unsigned comment added by 94.27.132.205 (talk) 19:16, 22 March 2009 (UTC)[reply]
Maybe. The problem with DNA is that, while you may have all the bits necessary, you wouldn't have any way to know what order to put them together in. Your photograph analogy doesn't quite work - a better analogy would be a puzzle for which we don't know the image we are supposed to be putting together. --Tango (talk) 19:45, 22 March 2009 (UTC)[reply]
I mean the image of the DNA. We are far from being able to backwards engineer DNA from observations of fossilised bones. --Tango (talk) 20:22, 22 March 2009 (UTC)[reply]
The problems with making a creature from scratch goes a long way beyond just assembling a viable DNA strand. You've also got to implant it in a suitable cell (ie one that has the right chemical environment, etc) - that has to be provoked into replicating by the right chemical setup in the mother - in the case of Dinosaurs, something has to create a huge egg - and lay it and hatch it. The way we clone animals right now is to take the egg from a closely related animal, wipe out its DNA and replace it with the new DNA. Then you implant the cell back into the female of the closely related species and wait for nature to take its course. However, we don't have any extant animals that are anything remotely like a Dinosaur. So we have no egg to implant the DNA into - and no mother dinosaur to implant the egg into. Worse still, it's very likely that all of the food that a baby dinosaur would be able to eat has long gone extinct - so you have a problem feeding it. Because we have no live dinosaurs to study - we don't even have a way to know what nutrients they need. Also, the world has changed quite a bit - different amounts of oxygen in the air - that kind of thing. Most animals get resistance to disease from their mother's antibodies - no chance of that happening here. The obstacles are spectacular...even if you could get an intact DNA strand - which isn't looking very possible from the amounts we've been able to extract. Remember that you can't just collect random DNA snippets from 500 different species spread over 160 million years and expect to be able to stitch them all back together! You need DNA from a single species...perhaps even a single sex of a single species...and over a few thousand years or so. That's asking a lot! SteveBaker (talk) 19:56, 22 March 2009 (UTC)[reply]
It doesn't need to be a huge egg, there were plenty of small species of dinosaur we could try and bring back. We don't have the technology now, but I don't see any theoretical reason why a synthetic egg wouldn't be possible to construct eventually. I think the DNA is the biggest problem, the rest can be overcome with effort but if the DNA doesn't exist, then it doesn't exist. --Tango (talk) 20:22, 22 March 2009 (UTC)[reply]
I'm no SteveBaker, but here's my take.
1.) Not yet, but theoretically possible given a well-preserved specimen. There has been some progress in sequencing the Neanderthal genome but there are still considerable gaps. Another concern is that even if you could piece together a "complete" genome for a given dino species it would almost certainly be a patch-work of pieces from different individual specimens and would utterly fail to capture the degree of genetic variation that would have existed within a population of that particular species. This would lead to considerable trouble with part 2 and any future breeding of your little dinos (which would all be genetically identical to each other -- not good for the health of the species).
2.) Without extraordinary advances in molecular biology, NO. One reason is that even if you knew the complete DNA sequence based on sequencing fragmented pieces of dino DNA, you'd still have problems assembling it into the proper chromosomes that would enable the putative dino cells to replicate. The way the sequencing of the human genome was done, large fragments of DNA contained in bacterial artificial chromosomes were sequenced and mapped to their proper chromosomes, then overlapping fragments were pieced together to generate a computational "assembly" of the genome that is now an advanced draft stage (there are still bits that haven't been sequenced due to their complexity or repetitiveness). We know the structure of human (and mouse, and fly, and dog, etc.) chromsomes because of cytogenetics, fluorescence in situ hybridization, and other such techniques -- which require intact cells and in some cases cell culture. Mapping the fragments of dino DNA to their proper locations within the dino chromosomes would essentially be impossible because of the inability to perform cytogenetic techniques. Furthermore, even if you knew where each piece was supposed to go, we don't currently have the ability to stitch together an entire chromosome "de novo" and somehow get it to assemble into its proper macromolecular structure, complete with histones and all the other DNA binding proteins that endow the DNA with the ability to be replicated in a living cell. Now, it is theoretically possible that you could get enough of the dino DNA to make a "complete" sequence and somehow "splice" it into existing chromosomes from a modern-day species (as was the plot in Jurassic Park) but this would be extraordinarily challenging (dare I say "impossible"?) for today's molecular biology. --- Medical geneticist (talk) 20:25, 22 March 2009 (UTC)[reply]
What about this iterative proposal: put the large species in a small species so that it's cramped and deformed, but alive, at birth. Then put the DNA straight back into the new girl once she's an adult (no CHANGE in the dna). It might still be cramped because of the deformity but basically should be normal. A final few generations the same way will result in a perfectly fit dino -- raised in as good a womb as you get (or whatever cold-blooded lizards have instead of wombs). What do you think of this proposal? 94.27.132.205 (talk) 20:40, 22 March 2009 (UTC)[reply]
See ALL of my objections above. You might maybe be able to get around needing a big egg that way - but you still have no cell to put the DNA into, no parent animal to implant the egg into, no food for the hatchling, no knowledge of how young dinosaurs have to be treated by their mothers - whether the temperature of the egg has to be varied during development (this turns out to be a CRUCIAL factor in the development of Turtles and Crocodiles...so it's probably critical in Dinosaurs too)...there are a million things we don't know (and arguably, cannot know) about raising a dinosaur. When you consider how many species have proven impossible to breed in zoo's - and that's with full knowledge of diet, parenting, etc, etc...this is so far from being possible. Heck, your first step would have to be in assembling lots and lots of plant DNA from species of that era and figuring out how to grow that BEFORE you even start on the actual Dinosaur. SteveBaker (talk) 21:02, 22 March 2009 (UTC)[reply]
I, for one, am very comfortable leaving it to Steve to determine whether paleogeneticists have access to complete dino DNA at this point. Edison (talk) 02:20, 23 March 2009 (UTC)[reply]
Birds are considered the modern descendants of dinosaurs so just hatch an egg and you've got yourself your own little baby dinosaur. It may be possible to get something like a dinosaur by seeing what's common between birds and crocodiles say and then cutting out a selection of those changes which are specifically for bird like features like beaks and putting in some of the more dinosaur like things that have their remnants in the junk dna and occur in crocodiles.
Or breed parrots? A lot of baby parrots look like mini 'raptors for the first few weeks after hatching. Probably sound a lot like them when they're begging for food too. --Kurt Shaped Box (talk) 21:41, 23 March 2009 (UTC)[reply]
Re:User:Medical geneticist's concern about the inability to perform cytogenetic techniques. I completely understand why jumping right to the Cambrian would be impossible, but couldn't we just step it back slowly? Map the Dodo genome, then something from the Neogene, then a few evolutionary steps from the Paleogene, and before you know it we're right into the Cretaceous. By figuring out the genomes of a creature's ancestors we could step backwards through evolution, using the later species as a guide for arraigning the genome of the previous ones. Make the evolutionary steps small enough, and the changes from one genome to the next could be so small as to be manageable. PlasticupT/C19:09, 27 March 2009 (UTC)[reply]
Falling
I was watching videos of cats falling and being okay--but some of the heights impressed me! If I fell from the same height, I'd be seriously hurt, how do they do it?!24.91.161.116 (talk) 15:48, 22 March 2009 (UTC)[reply]
The lighter the animal the farther it can fall without injury. With a small enough animal, like an insect, it could fall from an airplane and survive, as it's terminal velocity is too low to be, well, terminal. StuRat (talk) 15:56, 22 March 2009 (UTC)[reply]
I don't think it's just mass that's a factor, it's the ratio of mass to the area of animal projected onto a plane. Since mass is roughly proportional to volume (different animal have similar densities), which is proportional to the cube of linear size, whereas area is proportional to the square, smaller animals have an advantage over larger ones. With cats there is more to it, though, since they can self-right so their legs hit the ground first, allowing them to absorb the impact better. --Tango (talk) 18:25, 22 March 2009 (UTC)[reply]
If I drink something with 2 straws in my mouth does it take more or less sucking power to get the same amount of liquid as with 1 straw. How about with 15? I'm looking to find out the most effective number of straws, where I exert the least amount of energy for the most amount of liquid pay-off.24.91.161.116 (talk) 15:51, 22 March 2009 (UTC)[reply]
I'd say one straw is best. Two would at first seem to be the same, but there is likely to be an air gap between the straws which allows some of the suction to be wasted by sucking in air. The more straws, the more likely you will have air gaps. StuRat (talk) 15:58, 22 March 2009 (UTC)[reply]
I wonder what the efficiency of sucking through a straw is... if it's very efficient to start with (and I have a feeling it might be) then adding more straws won't be able to help. The only losses I can see would be from an imperfect seal around the straw (which is probably negligible with one straw) and the usual losses associated with any muscle usage (in this case, the diaphragm). --Tango (talk) 16:40, 22 March 2009 (UTC)[reply]
It's a simple matter of conservation of energy. The liquid is raised to some height - so it gains gravitational potential energy in proportion to (mass x :height) - that's the amount of energy it costs you to lift it through that height. So, neglecting friction and such - there is no difference in the energy required. That's certainly a reasonable assumption for drinking (say) water - but milkshakes are non-Newtonian fluids and their viscosity doesn't behave in a simple way. But in any case - assuming the two straws could be said to be independent - moving X amount of liquid through one straw ought to take the same amount of energy as X amount through two. So this is really a question of efficiency - can your mouth muscles (or rib muscles or diaphragm) produce that energy more efficiently in short-high-power sucks or better in slower, low-power sucks. Think of how your car uses more gasoline if you drive around all day with the tachometer pegged at 6,000 rpm instead of 2,500 rpm. Sadly, the human body is ridiculously complicated - and so that's an insanely difficult question - so probably you need to do a series of serious (albeit delicious) experiments to figure it out. SteveBaker (talk) 18:47, 22 March 2009 (UTC)[reply]
I believe that the viscosity of a milkshake is the main factor limiting flow rate, not the potential energy between the top and bottom of the straw due to gravity. The flow should be approximately proportional to the pressure differential created by sucking (atmospheric pressure minus intra oral pressure) divided by the resistance to flow through the straw, analogous to Ohm's law for linear electrical resistances. The lips, being flexible in the normal person, can seal around two straws as well as around one, especially if they are a short distance apart so there is not a failure to seal between them. Two straws=twice the milkshake per second, with the same suction created by the mouth. Two straws is like a larger straw (but wall effects may prevent a simple relation to the area of the straw opening). The failure to linearly keep increasing the flow with more and more straws would be due to the inability of the mouth to maintain the same high suction when a high flow rate enters, as well as leakage between adjacent straws. Edison (talk) 19:06, 22 March 2009 (UTC)[reply]
WP:OR: (I couldn't help it) with 8 oz of low viscosity liquid (water) and there is a learning curve:
Since there is, as you say, a learning curve, we need to know what order you did the trials in in order to interpret the data. --Tango (talk) 00:02, 23 March 2009 (UTC)[reply]
I have altered the table above to provide clarity as to the trial counting:
You can tell I am not a scientist. From the layout by itself, I assumed Trial 1 was first one straw and then two straws; Trial 2 was one straw and then two straws. You are right that it doesn't say that, though. // BL \\ (talk) 00:39, 23 March 2009 (UTC)[reply]
I recruited an independent referee to do the timing with a one second resolution timer. My challenge was to empty a measuring cup filled with 8 ounces of water with either one or two drinking straws by sucking the water into my mouth and then spitting it out into the adjacent sink in the fastest time. We then practiced a few times withan empty cup to be sure of the cues.
Show time: When she started the timer and said "go" I did the best I could to empty the cup as fast as possible and then declare "stop" while putting the cup down onto the counter (where it started) and then she stopped the timer. I then recorded the elapsed time. The testing trials alternated between between using one and two straws starting with one straw and finally ending with two straws (eight trials in all). The "spitting out" time seemed to go much faster than the "sucking" time that I attribute much of the "learning curve" to the "sucking" part. The apparatus consisted of a 12 ounce graduated clear glass measuring cup with a handle and "squash-proof" plastic drinking straws 7.75 inches long by 0.25 inches diameter. The water was about 48ºF. The referee thought I was nuts! -hydnjo (talk) 01:07, 23 March 2009 (UTC)[reply]
I've replaced the other responses to this question that you removed and moved your latest reply to the bottom - you managed to completely mess up the section!! (We've all done it, don't worry!)
So the conclusion we should draw from this extremely scientific and reliable experiment is that there is no significant difference between one straw and two for drinking water. Thank you for sacrificing your reputation for sanity for the sake of science - I salute you! --Tango (talk) 01:16, 23 March 2009 (UTC)[reply]
USE A MILK SHAKE! Don't spit it out, to avoid lots of wasted time. SWALLOW IT! Water is very low viscosity, so the limiting factor is likely the ability of the tongue and jaws to pump liquid, rather than the rate of flow of a viscous liquid through one or two tubes at constant pressure. Edison (talk) 02:14, 23 March 2009 (UTC)[reply]
Whilst generally in favor of the scientific method - I can't help thinking that our most dedicated test subjects may have trouble maintaining a uniform performance after consuming approximately 8 milkshakes...and that's before we begin to concern ourselves with control groups for the influence of extra chocolate on the viscosity. SteveBaker (talk) 12:36, 23 March 2009 (UTC)[reply]
The low flow rate with a thick shake might allow consumption of a small amount per trial. 3 ounces, maybe? There would probably be lots of volunteer experimental subjects outside a malt shop/McDonalds on a nice day. Edison (talk) 18:41, 23 March 2009 (UTC)[reply]
A useful experiment might measure the flow rate of a viscous liquid through one versus two or more straws, placed such as to allow the lips to seal around them. Weigh the source vessel containing the milk shake, have the experimental subject suck on 1 or 2 straws for a short period such that mechanics of swallowing or spitting out are not a factor, and weigh the source vessel to see how much was consumed in, say 2 seconds, such that the mouth can maintain approximately constant suction. Edison (talk) 03:11, 24 March 2009 (UTC)[reply]
Hi all I am researching injuries that can cause memory loss. By this I mean memory loss that occurs as a result of an accident, most likely a head injury in this case, as opposed to the likes of Alzheimer's or Parkinson's disease causing memory loss. I have read about the likes of chronic traumatic encephalopathy (punch drunk syndrome), subarachnoid haemorrhage, skull fractures and concussion causing memory loss. (Only temporary with regard to concussion). My question does anyone know if I have missed out any injuries which can result in memory loss? If so could they give me some pointers as to where I can find out more information on them? Many thanks. —Preceding unsigned comment added by 139.222.240.10 (talk) 20:45, 22 March 2009 (UTC)[reply]
Apologies, I know you guys must get stupid questions like this alot, but I cant get a straight answer anywhere else.
From this quote "A potentially promising area for research is the fact that if particles become more energetic as they are heated or accelerated their gravitational field increases. Changes in gravity can perhaps be attributed to a change in a spherical zpf energy density gradient surrounding an accelerated or decelerated massive particle." It seems to suggust that the zero point field can effect gravity, and the casimir effect moves objects, would it be possible , If we had better tech than we do now, to make a device that can manipulate zero point energy to move objects like the gravity gun if halflife 2 for example. I know this is stupid question but i cant get a strait answer from anyone about this, if not thats fine , if so thats fine too, if opinions are devided who current has the strongest case scientifically.
The Casimir effect is a fairly weak force equivalent to van der Waals bond. It's potential energy must be very low and contribute very little to a measured mass. Its effect will be the greatest on the smallest scales, such as between nucleons. However this mass would already be measured when the mass of nuclei is determined, so there should not be lots of spare energy there for the taking. This force is what gives grease its strength. Graeme Bartlett (talk) 04:24, 23 March 2009 (UTC)[reply]
protonation of the alcohol group in 2-methylcyclohexanol
In order to protonate the OH group with phosphoric acid to weaken the C-(H)OH bond so a dehydration elimination reaction can occur to yield 1-methylcyclohexene, does this mixture need to be subjected to heat? At what stage of the mechanism for the elimination reaction is heat needed? John Riemann Soong (talk) 01:42, 23 March 2009 (UTC)[reply]
Heat probably doesn't affect the extent of protonation much. However, heat probably does promote loss of water because that is a fragmentation reaction, and increasing temperature makes this change in entropy an increasingly important part of the overall energy of the reaction. Heat also makes all reactions faster, so you'll be able to get out of lab in time for the next class:) DMacks (talk) 01:49, 23 March 2009 (UTC)[reply]
Well, I'm a bit confused by my lab manual. It seems to imply that the thermodynamic stability difference between 1-methylcyclohexene and 3-methycyclohexene is greater than the stability difference between 1-methylcyclohexene and 1-methylcyclohexanol. If I look at it a certain way, it almost seems that the 1-methylcyclohexene product is lower in energy than the alkane product! I'm wondering at what point the heat input is critical for what must be an endothermic reaction (reversal of saturation/addition of an alkane). And the protonation of the OH group appears to require the greatest activation energy in the reaction. I know heat aids in reactivity, but surely it can't be just that (as well as yes, the steam distillation of my product?) According to the energy diagram, the loss of the water molecule after the alcohol has been protonated is exothermic so heat would only appear to aid in speed of the fragmentation step. John Riemann Soong (talk) 02:15, 23 March 2009 (UTC)[reply]
If you have the actual energy diagram, then you know exactly where energy needs to be added to make the reaction go:) I assume that it is ΔG, so steps where ΔS changes are generally the ones that are the most affectable by T. You always need energy to get over the activation barrier, but once you have "at least that much", the equilibrium will always be establishable. And no matter what the role of heat may be in the chemistry or where each equilibrium lies, "removing the product as soon as it's formed" is going to drive an even fairly unfavorable (by product stability) reaction, thanks to Le Chatelier. Once you're steam-distilling the product out, that's all that really matters for accomplishing this reaction in practice. DMacks (talk) 02:29, 23 March 2009 (UTC)[reply]
I'm not sure if the diagram is being held at constant temperature though. Fragmentation generally would be exergonic yes? It wouldn't be that elevated temperature between the protonation and fragmentation steps allows fragmentation to proceed, e.g. s*dT exceeds a positive dH? I'm confused about energy flow -- e.g. whether the diagram includes the phosphoric acid in the system or not. The lab manual says the phosphoric acid "catalyses" the reaction so would it be that the H+ is what injects free energy into the system before the mixture is heated? Removing the product sounds really promising as a "drive" for the reaction, except I think the methylcyclohexanol is being distilled too (along with the aqueous components). Is this where volatility and vapor pressure would start to be important as well? I'm trying to finalise my understanding of this process. Thanks for all the help anyway! John Riemann Soong (talk) 05:19, 23 March 2009 (UTC)[reply]
Also, I note interestingly that methylcyclohexanol has a boiling point of 165-168 degrees Celsius. It's miscible with water, so it would probably form some kind of azeotrope and I'm correct to assume it wouldn't boil at significant amounts at 96 degrees Celsius compared with the methylcyclohexenes (bp 104-110)? John Riemann Soong (talk) 05:19, 23 March 2009 (UTC)[reply]
Folic acid
I'm currently working on a spoken version of folic acid. However, as I was going through it for a quick copyedit, I ran into a problem; the equation at the end of the section Biochemistry of DNA base and amino acid production seems, to me, to be nonsensical. I'm having difficulty determining what it's actually supposed to be. Is it wrong, or is it just my sight beginning to blur from too much editing? If someone could take a look at it, I would be much obliged. Thanks! Sophus Bie(talk)10:00, 23 March 2009 (UTC)[reply]
For my science class on a project, we have to draw a scaled drawing showing improvements we made to a windmill. How would I show that I made the turbines out of carbon fiber? <(^_^)> Pokegeek42 (talk) 13:13, 23 March 2009 (UTC)[reply]
By writing "carbon fibre" next to them. Technical drawings are often annotated to include information on construction materials and lots of other stuff. --Tango (talk) 13:23, 23 March 2009 (UTC)[reply]
Maybe you could copy (as in make a similar drawing not photocopy) a micrograph or show how the fiber reinforces the material [9]. Then compare to other materials and say why carbon fiber is better. or do s.th. like Crystal structure. You could also do a drawing of the windmill shaded with areas showing high strain and how your carbon fiber would be an improvement there. S.th. like this would be over the top. [10]. Just get some colored pencils and shade in a turbine image.76.97.245.5 (talk) 13:51, 23 March 2009 (UTC)[reply]
Tango's absolutely right. Use any method that makes your intention clear. I've recently been involved in a rather large construction project and, besides the sheer volume of drawings required, which is staggering, I've also noticed that formality tends to go out the window if there's a more clear way of expressing what you need to. Matt Deres (talk) 19:56, 23 March 2009 (UTC)[reply]
Given that this is a school project the prime target is to impress the teacher, not necessarily communicate with the reader. So something that shows a little effort will help. 76.97.245.5 (talk) 12:42, 24 March 2009 (UTC)[reply]
Probably "purging of toxins". In this case, no, not to any significant degree. Also, it's a mistake to believe that we are all suffering from mysterious unnamed "toxins" in the first place. This is just a marketing scam. StuRat (talk) 15:53, 23 March 2009 (UTC)[reply]
Another possible interpretation is that they are asking if microdermabrasion can cause vomiting. I sure hope not. If so, I'd never do that again. StuRat (talk) 15:55, 23 March 2009 (UTC)[reply]
There is certainly a lot of crap out there about these 'toxins' and things you need to get rid of or deal with. Our bodies pretty much maintain themselves - there are very few things we need to do to it to allow it to keep functioning efficiently. The skin sheds cells very effectively without dermabrasion. Our kidneys filter out most kinds of routine toxins and flush them out when we pee. None of these silly treatments are needed for a normally functioning person. We'd never have survived all of those hundreds of thousands of years without these things if our bodies were really that pathetic. So eat sensibly - exercise moderately - bathe periodically - and you're doing about the best you can. SteveBaker (talk) 11:27, 24 March 2009 (UTC)[reply]
Part of this toxins scam is the claim that they are all a recent occurrence; chemicals created as part of our modern industrial world. In some parts of the world with dismal environment practices, this may actually be true. However, in the West, most of us don't absorb this level of toxins (except for smokers, perhaps). And, in any case, all of these "cures" that promise to remove the toxins are unable to remove a significant portion. StuRat (talk) 14:44, 24 March 2009 (UTC)[reply]
Monophyly of amphibians
Nowadays, the consensus is that amphibians form a monophiletic group. Nonetheless, in the past there was much debate over whether they were paraphyletic (i.e., amniotes descend from them). I have looked in Amphibian articles on Wikipedia and I have done google searches, but I haven't found much; does anybody know some place where I might find an in-depth discussion of the taxonomy of amphibans over the last few decades? Thank you. –Leptictidium (mt) 19:43, 23 March 2009 (UTC)[reply]
I doubt this is part of your problem but monophyletic is the correct spelling. Some of the references in this article may help. The American Museum of Natural History seemed to have overhauled its taxonomy system and googling this may lead to relevant information. This paper, THE AMPHIBIAN TREE OF LIFE, by the American Museum of Natural History seems to go over the various DNA tests, the reasoning for classification, and what changes they suggest in taxonomy. I would raid the sources and check out other works by the authors to look for more material on the topic. I found that paper by googling "Amphibian taxonomic philosophy" without the quotes. Sifakatalk17:18, 24 March 2009 (UTC)[reply]
Expansion of Space
I have a hard time understanding what we mean when we say our universe is expanding. What exactly is expanding? Is it the distances between all cosmological objects? (Are these objects themselves expanding?) If it is, where is it expanding to? Where does this extra space come from? If I get it right, it is the space itself which is expanding. If it is so, is it expanding into its own dimension? I mean in 3 dimensions or something else is going on here. If we assume a hypothetical picture of seeing the universe from 4th dimension, we will see its edge. is this edge moving outside? If yes, what is this outside and what is this outside composed of? Please clarify. - DSachan (talk) 20:11, 23 March 2009 (UTC)[reply]
"What exactly is expanding?" pace itself is stretching
"Are these objects themselves expanding?" Objects that are gravitationally bound like galaxies and solar systems are not expanding. Larger objects like galaxy super clusters may still have some residual expansion but could possibly complete their gravitational 'colapse' in the future and become bound, after which the space within them would have stopped expanding (Only at a very large scale the universe can be considered to have a uniforme rate of expansion).
"If we assume a hypothetical picture of seeing the universe from 4th dimension, we will see its edge. is this edge moving outside?" There is no evidence that the universe has an 'edge'. Dauto (talk) 21:07, 23 March 2009 (UTC)[reply]
If you were to embed the universe in some 4D space, then there would be an edge - well, the whole thing would be edge, but it would still make sense to talk about it expanding into something that is outside it. General Relativity does not involve any higher dimensional space that the universe is contained in, but there are version of String Theory that do (see Brane cosmology). --Tango (talk) 22:15, 23 March 2009 (UTC)[reply]
Tango, it's not clear to me how would someone embed the universe in a 4D space when the universe itself is already 4D. Still, even if you embed the universe in a higher dimensional space it is istill improper to talk about the edge of the universe. Dauto (talk) 22:25, 23 March 2009 (UTC)[reply]
Ok, a 3+1 universe embedded in a 4+1 space. The OP was talking about just space, not spacetime, so I followed the same convention. --Tango (talk) 23:47, 23 March 2009 (UTC)[reply]
Those who claim to understand this concept often claim that the distance between objects in space expands, such as interstellar or interplanetary distance, but smaller distances, such as my meter stick, or some other measuring device, do not expand at all. This leads to the absurdity that two objects in space linked by a gossamer thread of great length would remain unaffected in their separation by the cosmic expansion, while two similar objects not linked by a gossamer thread would move apart, the hypothetical gossamer thread having a specified length but negligible tensile strength. This makes cosmic expansion a form of magic. Edison (talk) 03:07, 24 March 2009 (UTC)[reply]
It is important to understand that the cosmic expansion is governed through the Einstein GR equations that relate the behaviour of the space-time metric to the density and flux of energy and momentum. The universe has a uniforme distribution of matter on a very large scale and on that scale the expansion of the universe is uniform. But if you look closer, you will see that the universe has clumps of matter (Superclusters, Clusters, Galaxies, etc...). On those smaller scales, the space expansion is not uniforme. In fact, locally you might even have some shrinking. Inside a clump of matter that has virialised (achived an equilibrium) like galaxies, for instance, there is no space expansion (or shrinking) at all. So, the interplanetary and interstellar distances are not expanding, but the intergalactic distances are. A yardstick wouldn't expand even if it were on intergalactic space because it is an object bound by interatomic forces which govern it's size. The gossamer seems to be simple nonsense. Dauto (talk) 04:26, 24 March 2009 (UTC)[reply]
If I am in free fall orbiting the Earth, and I place two grains of sand 1 meter apart, will the space between those grains expand? I gather no because locally space does not expand? If I take more grains of sand, and place each one meter from the previous one, forming a line all the way to a distant galaxy with measurable redshift, will some of those grains move away from their previous neighbor? Such as those far away from significant concentrations of mass. Is it specifically the mass of galaxies which prevents expansion? 88.112.62.225 (talk) 06:12, 24 March 2009 (UTC)[reply]
Yes, that's correct. Within galaxy clusters the expansion has been halted by the gravitational effect of the mass within the cluster.The placement of the grains should be at rest with respect to the comoving coordinates. Dauto (talk) 01:05, 25 March 2009 (UTC)[reply]
So is there a "local space" where space does not expand, and when I go outwards, one meter a time (or even one nanometer at a time), suddenly one of those meters is outside the "local space" and that meter does expand? A sudden jump from zero expansion to non-zero expansion? I'm a bit startled by such non-linearities... 88.112.62.225 (talk) 20:51, 25 March 2009 (UTC)[reply]
So, there's a mated pair of Carlina Wrens that frequent my backyard, foraging together. They're quite cute. Now, I read in our article that: "They eat insects, found in leaf litter or on tree trunks; they may also eat small lizards or tree frogs. In winter, they occasionally eat seeds, berries, and other small fruits." This doesn't quite agree with my observation.
Both of them come to my feeder, in which I've got a variety of seeds and nuts, and also a container of delicious mealworms on top. The smaller member of the pair eats only mealworms, never nuts, and the larger eats only seeds and nuts, never mealworms. Sometimes the larger one will bring the smaller one a bite of peanut, and pass it between their beaks, but it just ends up getting passed back, and the smaller wren goes back for more yummy beetle larvae.
Does anyone know what's going on there? I wonder if the smaller one is the female, loading up on bugs to feed to some chicks back at home? Why is the other one (male?) an apparent vegetarian? -GTBacchus(talk) 20:51, 23 March 2009 (UTC)
They are not nearly as "nice as 1 might think. Besides monopoloizing as many nest cavities as possible (let's not even go into monogamy and cuckoldry in small birds)They also have been known to pierce the eggs of thier nieghbouring insect eaters just before thier own hatch! As an aside, just look at the bill of any bird and it will tell a great deal about how it makes a living. The Ojib word for wren translates as "little bignose", just right for probing to find protein rich insects, not so good for seeds tho? As to what your pair are upto with thier diet choice, I suspect the below to be correct but I can't know for sure. I'm not a wren, i'm a FROG. 67.193.179.241 (talk) 12:38, 24 March 2009 (UTC) Rana sylvatica.[reply]
Could the female be preggers ? And does that alter their diets like in human women (to provide nutrients needed to grow the offspring) ? StuRat (talk) 21:19, 23 March 2009 (UTC)[reply]
Given the season, that makes a bit of sense. I'm not actually sure which one is female, or whether peanuts or bugs make better food for pregnant wrens. -GTBacchus(talk)21:26, 23 March 2009 (UTC)[reply]
It could just be that your feeder is the easiest food source and the wrens are taking advantage of it. If your feeder contained lizards and insects, it would be spot on! Livewireo (talk) 15:38, 24 March 2009 (UTC)[reply]
Wolves, dogs and foxes
Wolves, dogs and foxes are all of the same family (canine) and give birth to cubs, pups and kits (respectively). Lions and bears also have cubs (but are not of the same family as the aforementioned canines nor of each other - not to mention that the latter adults are boars and sows but not related to pigs). Seals have pups (but are not related to canines). Where is the logic in how offspring are named? —Preceding unsigned comment added by 69.77.185.91 (talk) 21:51, 23 March 2009 (UTC)[reply]
As far as I am aware, there is no logic to it whatsoever. Even less logical are the names for groups of a certain animal. --Tango (talk) 22:07, 23 March 2009 (UTC)[reply]
For a 300 foot high windmill, how big would the turbines be? I need to know how much carbon fiber material would be needed to make them. <(^_^)> Pokegeek42 (talk) 22:18, 23 March 2009 (UTC)[reply]
I think you need to try other research methods for this project than asking us everything... I'm sure the rough technical specs for some wind turbines are available online - try Google. --Tango (talk) 22:21, 23 March 2009 (UTC)[reply]
My search engines suck-all they give me is porn. My group members don't help either, they just claim their computers had a "virus" and nothing worked. I have no life anyway-this is the only human interaction I get. Mostly I ask you because I'm lonely. Seriously, do you think a total nerd has many friends? I read manga in japanese, for crying out loud. Cut me a break. I need some social time. When I'm not playing video games or reading manga or watching anime...actually, I don't do anything besides that. God, I need a life. <(^_^)> Pokegeek42 (talk) 22:29, 23 March 2009 (UTC)[reply]
Try googling for "wind turbine specs", I don't you'll just much porn from that (give or take Rule 34!). I'm sorry to hear that you are lonely - there are plenty of people that share your manga and anime obsession, why don't you see if you can find a local anime society where you can meet up with people and watch anime together? (Such societies certainly exist at most universities, I expect you can find them in the real world as well - although I warn you, the kind of people that are members are often pretty... um... intense.) --Tango (talk) 23:44, 23 March 2009 (UTC)[reply]
I'm always surprised at Wikipedia meetups by how normal everyone is. I've never heard anyone describe an AnimeSoc member as "normal"! --Tango (talk) 00:37, 24 March 2009 (UTC)[reply]
I wish I could join something like that, but I'm too "young" in my mom's opinion. I haven't finished sixth grade yet. If I joined something like that, my parents would think I'm like, totally emo and trying to commit suicide. Can you say "paranoid"? Thanks for the help, anyway. <(^_^)> Pokegeek42 (talk) 19:16, 24 March 2009 (UTC)[reply]
Perhaps you could find an anime fan, a little older than you, that is (or, at least, does a good impression of being!) pretty normal. Your parents may then be more inclined to allow you to go to anime meetings with that person. (There are normal anime fans out there if you look for them!) --Tango (talk) 20:21, 25 March 2009 (UTC)[reply]
The good news is that considering your age, you will probably not be expected to provide an in depth stress analysis using finite-element methods. 65.121.141.34 (talk) 20:39, 24 March 2009 (UTC)[reply]
The anon is saying you won't be expected to do advanced engineering with your 6th grade project. (Too advanced for me, anyway - I have no idea what a finite-element method is!) --Tango (talk) 20:21, 25 March 2009 (UTC)[reply]
Once you dissolved the resultant gases in water, you would regenerate the ammonium and nitrate ions, which would just give you a solution of ammonium nitrate back again. What you would need to do is to have some way to seperate the nitrogen oxides from the ammonia gas in the gas phase before dissolving them into water individually. --Jayron32.talk.contribs00:36, 24 March 2009 (UTC)[reply]
I can't find any information on dystonia affecting the lower back. Does it not exist? Is it extremely rare?
Also, are there any muscles in the lower back which, upon contraction or spasm, cause the body to hunch forward? From what I've been able to find out, bending forward is caused by contraction of the abdominal muscles only and the back muscles maintain an upright posture or arch the back.
I have no answer to the first part of your post. Our page for dystonia is not very clear and repetitive in parts (two times "general dystonia" for example). For the second part: It is impossible for muscles in the lower back to cause a forward movement of the body. Muscles are always long when relaxed and "shorten" when they tense. So back muscles work to shorten the back and abdominal muscles contract the abdomen. So both muscle groups work together (called antagonistic muscles) to determine body posture and to perform controlled movements. TheMaster17 (talk) 10:41, 24 March 2009 (UTC)[reply]
Thanks for confirming the info about the back muscles, that's what I thought. I would guess then, that IF dystonia of the lower back does exist, the sufferer would NEVER hunch forward at the time of a spasm? (edit: what is causing me some confusion on this is that I recall, several years ago, pulling a muscle in my neck which caused my head to stay stuck tilted and twisted to one side. I was told that it was the muscle on the opposite side (the elongated one) that was injured, not the one on the side to which my head was sticking. So, while it definitely makes more sense to me that dystonia of the back could not cause a forward bending posture, my experience with my neck reminds me that the body doesn't always seem to work in the most immediately logical way. Or maybe the doc who told me that about my neck was wrong and it was the muscle on the shortened side of my neck that was strained?) bcatt (talk) 16:03, 24 March 2009 (UTC)[reply]
Fingerprints
Why is it widely believed that everyone has different fingerprints? It's not beyond the realms of possibility that two people who are distant and unknown to each other could have the same prints. JCI (talk) 02:12, 24 March 2009 (UTC)[reply]
Francis Galton showed back in the 19th-century that statistically the odds of two people having identical prints is pretty much impossible. This is part of what made fingerprints acceptable evidence to courts. I'm fairly sure you are more likely to have 17 matching snippets of DNA (or whatever the standard matching SNP number is) than a full set of identical prints. --98.217.14.211 (talk) 02:47, 24 March 2009 (UTC)[reply]
But, of course, the problem comes in when comparing fingerprints (especially partials) to a database containing millions. With that many to choose from, you're sure to find several fairly close matches. But, when used properly, say by comparing bloody fingerprints at the scene with the prime suspect's, then the chances of getting a false match are extremely low. StuRat (talk) 05:21, 24 March 2009 (UTC)[reply]
What Galton calculated (the calculation was not a proof in the mathematical sense, more an informed estimate like the Drake equation) was the probability of two different prints matching in all their minutiae (Finger Prints, 1892, Ch. VII). There are tens of thousands of minutiae in one print. Fingerprint analysts, however, do not compare all of them. In fact, the number of minutiae legally required for a match is in the low tens, typically (Criminalistics, James Girard, p149). So Galton's huge probabilities, even if they are correct, tell us absolutely nothing about the reliability of modern practice. --Heron (talk) 23:35, 24 March 2009 (UTC)[reply]
It depends on what you mean by "identical" - if you take two objects that are intended to be identical (two pennies for example) - they aren't REALLY identical, each has little nicks and scratches that distinguish it from the other. You can't imagine making any pair of physical objects that were utterly identical in every way. In that regard, I would maintain there are NO pairs of objects of any kind (at the 'macro-scale' at least) that are identical. Sure, you can talk about two Hydrogen atoms being identical - but not anything of any size.
So this oft-repeated claim that no two fingerprints are identical is OBVIOUSLY true at some scale of examination. There are something like 1020 atoms in your finger - it's clearly impossible that all of the atoms in someone else's finger are arranged precisely the same way. But it's not a particularly interesting or useful claim since no two of ANYTHING are utterly the same.
However, there aren't that many patterns of loops and whorls out there - there simply can't be. So at some other scale of description (perhaps a layman who knows nothing of fingerprint analysis using nothing but naked-eye examination) there are clearly pairs of fingerprints that are so similar that we'd need an expert to tell them apart. So I regard this whole thing with a deal of skepticism. Francis Galton's "calculations" cannot possibly be correct - there is simply not a solid point at which you can say "sufficiently identical to count" without very carefully defining you means of measurement and the errors inherent in making those measurements. Remember that your fingertips get cut and damaged - they grow callused if you work with certain tools - they are continually renewed and regrown. They change over time as our fingers grow from little baby fingers into adulthood. They get wrinkled up when you get them wet...so my fingerprint today is not the same as it was yesterday - at some level of examination.
The measure that I think is worth examining is whether your fingerprint at (say) age 5 years is more similar to your fingerprint at (say) age 75 years than to any one else's fingerprint in the world. I think that's a much harder standard to meet and I'd be very surprised if that were true.
It's on, Steve Baker!! You say "However, there aren't that many patterns of loops and whorls out there - there simply can't be". how much informatino entropy does a fingerprint OBSERVATION (for comparison with other fingerprints) contain? answer THAT question. 79.122.44.240 User ID added by Sifaka
What exactly do you mean by "information entropy"? Steve is right in saying that there are relatively common patterns in fingerprints, see Fingerprint#Classifying fingerprints to see what I mean. According to this paper there are more errors when comparing two fingerprints from the same finger but decades apart than two fingerprints from the same finger taken recently using a minutiae based recognition approach. A quote from the aforementioned article:
"From a theoretical point of view it is common sense that aging may not impact the characteristics of fingerprints [l]. However for practical purposes, scaling effects of minutiae based matching algorithms may render older templates useless... In most cases, the ageing process does not change the structure of the fingerprint image. The ridges in the epidermis (dead dry skin) always show the same pattern since the information thereof is stored in the lower layer of the finger (dermis - live skin). If an injury of only the upper skin is sustained, after a certain time the same ridges are formed as before. Even the ageing process cannot change the paths of the ridges. The fingerprint may be a little larger, the ridges may be lower (if they were worn due to working), and the finger may show some wounds. However, the pattern always remains the same. Therefore, it should not be difficult, for the different verification algorithms, to identify fingerprints of the same finger, which only differ in the date of their acquisition, as being identical."Sifakatalk18:28, 24 March 2009 (UTC)[reply]
The reason I addressed Steve Baker is that he is the only one here who knows what information entropy (Shannon entropy) is and can apply it to fingerprint observations!! But hes too squeemish to do so apparently...
You can't apply that fundamental information-theoretical approach when the terms involved are so vague. Let's read what our article says:
In the Henry system of classification, there are three basic fingerprint patterns: Arch, Loop and Whorl.[8] There are also more complex classification systems that further break down patterns to plain arches or tented arches.[7] Loops may be radial or ulnar, depending on the side of the hand the tail points towards. Whorls also have sub-group classifications including plain whorls, accidental whorls, double loop whorls, peacock's eye, accidental, composite, and central pocket loop whorls
So if I take that at first sight: There are three kinds (Arch,Loop,Whorl) - but there are really two kinds of arch, two kinds of loop, seven kinds of whorl...so there are eleven kinds of fingerprint. The probability of two fingerprints being identical is one in eleven and certainly there are billions of people with "identical" prints. Well - no. The print can be bent and twisted or closer to the fingertip or off to one side. Suppose we use the distance between the skin fold at the joint to the center of the arch/loop/whorl - well, if we measure that distance accurate to the nearest millimeter - then perhaps there is between 1 and 20 millimeters between 'fold' and 'feature' - so now there are 20 different kinds of eleven different features - so we have 220 different fingerprints in the world...but suppose we measure accurately to half a millimeter - now there are 440 different prints - but if we only measure accurately to 2mm - then there are only 110 different prints. If you alter the precision and complexity of what you measure - you can make the answer come out to anything you want. If I want it to come out that all 7 billion people in the world have "different" prints - I can just measure enough subtle parameters to enough precision and claim that statistically, it must be so. But it's meaningless. If I measure to less precision - there are fewer "unique" prints...if I just look at the gross 'shape' then there only 11 unique prints. You just can't attach a number to that. All we can say is that fingerprints are more unique than (say) pennies - but less unique than (maybe) snowflakes. But that's just a gut-feel thing - it's not science. In scientific terms - the print you have now - is different from the one you had when you started reading this sentence because a few skin cells have fallen off in the meantime. This is truly a bullshit thing...it's politics on behalf of crime-fighters and generally the stuff of urban legends. They say nobody ever got mis-identified because of their prints - but how would we know? If there were then they were misidentified for chrissakes! SteveBaker (talk) 00:49, 26 March 2009 (UTC)[reply]
tsk tsk Steve Baker, you're not thinking hard enough. You can give a range of entropies, depending on how good of an expert you pick, but the fact is, there are going to be an n number of fingerprints for which a given expert will say they are that of a different person, and the 2-based logarithm of n will give you the number of bits of entropy in the coding of that observer. You follow? If you want you can say the number of bits of entropy "range from" and then go 6-whatever, because the worst "expert" actually makes observations according to criteria by which fingerprints fall evenly into one of 64 possible groups (where he would say that two fingerprints in that group are "of the same person", according to his observation [=his observational criteria]!). The best expert might make observations by criteria according to which fingerprints fall evenly into about a million possible groups. In this case it would have 20 bits of entropy. So you could say "fingerprint observations for comparison purposes have 6-20 bits of entropy depending on the expert making the observations" -- you would make this statement if in your estimation the worst experts WOULD, for a given print, answer "yes it is the same person" for the prints of every 64th discrete person whose prints you could ask them to compare to the one in front of them, and the BEST experts would answer "yes it is the same person" for every every millionth discrete person whose fingerprints you could ask them to compare it with. For the first, the expert compares the prints by 6 bits of observational entropy, for the second, by 20 bits. However I am just making these bit numbers up!!! I am calling you out, Steve Baker, to propose an informational theoretical number of bits of entropy in actual, real, honest-to-goodness, expert fingerprint observational criteria for comparison purposes!! And the reason I'm calling you out is because you're the only one here who can possibly comprehend what I'm even talking about.Ball's in your court, Steve Baker.79.122.75.197 (talk) 17:41, 26 March 2009 (UTC)[reply]
Your conduct is bordering on the disruptive. You are being argumentative. We don't call out individual editors here. Cut it out. - EronTalk17:49, 26 March 2009 (UTC)[reply]
For people other than Steve Baker: although it may look like I am being argumentatitve with Steve Baker, in fact he (unlike anyone else here) knows exactly what I'm talking about and will answer with a better attempt soon enough. I'm only "calling him out" in that 1) he is one to respond to a good-natured challenge, and 2) he's the only one here who can possibly answer the question addressed to him. However I will give others a chance to see the record, which will be Steve Baker's correct result given shortly. That's why I'm doing it here, so everyone can see the answer.79.122.75.197 (talk) 18:03, 26 March 2009 (UTC)[reply]
This isn't your private chatroom with SteveBaker, or any other editor for that matter. And I'd suggest that most editors here don't much like being told that they can't possibly comprehend you. - EronTalk18:31, 26 March 2009 (UTC)[reply]
While obviously, not being Steve Baker, my poor little mind cannot comprehend what you say, I will note that your capitalised 'would' seems rather odd, dismissing the whole probabilistic/expected value thing. After all, if people are giving the wrong answer at regular intervals, that's easy to correct for :P Or is the weird detached thing below written by you and supposed to fit into the above paragraph? 79.66.127.79 (talk) 20:23, 26 March 2009 (UTC)[reply]
attn steve baker: don't read the rest of this paragraph! -- No, the "weird detached thing" is for people like you, not to bug me about it. Steve Baker can understand information (shannon) entropy, which is about uncertainty and hence automatically includes...uncertainty. But why am I wasting your breath, you are re not Steve Baker -- so look, there's the weird detached thing written below, just for you! 79.122.75.197 (talk) 20:35, 26 March 2009 (UTC)[reply]
Was merely pointing out that you seem to think you are discussing this in a very deep, arcane sense, but appear to be addressing the problem in a very simple manner with the addition of a few well-known mathematical concepts. And while doing so, you appear to be skipping some basic and important ideas. But I'll leave this for Steve, if he feels like addressing it in your terms. 79.66.127.79 (talk) 20:46, 26 March 2009 (UTC)[reply]
observer would, in with 99% likelihood (with a 1% false negative) say are DIFFERENT. What is the 2-based logarithm of N? That is the number of bits of entropy
Fingerprint evidence has been used in countless court cases. But there never seems to has been two persons found to have identical prints - not even for one finger, let alone all 10 fingers. If matching prints had ever been found, the occurrence would have received a lot of publicity. Also, from then on every defense lawyer would have fingerprint evidence thrown out. Even identical twins do not have matching prints, although their DNA is identical. Of course, matching prints of different people would have to be stumbled on by chance - fingerprint classification and searching is far from perfect. But with all the criminal cases that have used prints, two persons with the same fingerprint would surely have been found by chance. The problem with prints is that there is no known way to digitize the pattern. If there was, a computer could easily find identical prints. (Threshold scoring with a computer is useful when comparing two known fingerprints, but that is not a random search.) Illustrating this, a friend of mine had his place burgled and the burglar cut himself on the glass of the window he broke to get in, and he left a bloody fingerprint. The police said they could not try to match the print unless my friend could name 10 persons whose prints (if on file) could be checked for a match. That shows there is no way to make a full search of all fingerprints. (The FBI has a database of over 51 million prints.) Even when a match for the same person is found by other means, it is occasionally wrong due to police sloppiness (wrong name on the fingerprint card, etc.). See "Criticism" and "Errors in identification or processing" in the Wikepedia article Fingerprint.– GlowWorm.
The FBI has recently made false positive identification of an innocent person, Brandon Mayfield, as a terrorist bomber. Duplicate fingerprints or malfeasance? The proof of validity of fingerprint identification is generally lacking and is based mainly on hand-waving and unverified statistical assertions. Any forensic technique's validity should hold regardless of whether the government is out to get the individual. Edison (talk) 04:45, 25 March 2009 (UTC)[reply]
Yeah - exactly. It's observer bias: "Nobody ever gets misconvicted because of fingerprint evidence"...except perhaps for the people who were indeed misconvicted! If you could say "Everybody who was ever convicted of a crime on the basis of fingerprint evidence subsequently made a full confession" - then maybe. But I'm 100% sure that plenty of people who were convicted on this basis have screamed and kicked and protested their innocence all the way to jail. How do you KNOW you didn't misconvict one of two of them because their prints happened to be identical to the real criminal? SteveBaker (talk) 00:49, 26 March 2009 (UTC)[reply]
Renal Medullary Carcinoma (we don't have an article on this yet -- Done!) is a rare type of cancer that affects the kidney. It tends to be aggressive, difficult to treat, and is often metastatic at the time of diagnosis. It is not the same thing as sickle cell disease but the references in PubMed suggest that most individuals with this type of cancer have sickle cell trait or sometimes sickle cell disease -- meaning that the sickle cell trait may be a risk factor for this type of cancer (although it is still incredibly rare in people who carry the trait). See this for one of the first reports. There are also reviews available (here and here). I hope this helps. Clearly, anyone who has potential concerns about this disorder should see their physician as soon as possible. --- Medical geneticist (talk) 04:48, 24 March 2009 (UTC)[reply]
If humans manage, through war, climate change or any other mechanism, to cause our own extinction, then is it likely that some other sentient creature (not necessarily of a currently existing species, not necessarily originating on Earth, and potentially including the Creator if one exists who isn't already omniscient) will study our mistakes and learn from them? If so, does our capacity to serve as an example in this way increase with our peak population? NeonMerlin10:17, 24 March 2009 (UTC)[reply]
Given the openness of the scenario - yes clearly if some creature capable of study came about after the end of humanity then provided they can uncover a history of our demise they could use it as an aid to preventing their own demise. Of course knowing what causes something and avoiding that occuring are two different things. I don't see how a larger population makes it more obvious - apart from perhaps an increased chance of their being 'evidence' of our existence perhaps...but then i'd say a small population of technologically advanced citizens are more likely to be 'findable' than a mass-population without technological advancement. 194.221.133.226 (talk) 10:25, 24 March 2009 (UTC)[reply]
Well, given the difficulty of interplanetary travel - it's unlikely that aliens would come here. Doubly so if there were no intelligent lifeforms left here. So I think that's really highly unlikely. Another possibility might be that without humans, some other species that could survive whatever we screw up might evolve to eventually reach our levels of intelligence, curiosity and creativity. They might well be able to use archeological approaches to discover who we were and how we screwed up. Sadly, the most enduring things we'll have left behind are things like non-biodegradable plastic waste in landfills and nuclear waste bunkers - which won't speak well of our good sides. What's sad is that it's unlikely that our crowning achievements will survive - art, music, Wikipedia, architecture - all of that will have crumbled to nothing within half a million years...and it would probably take at least that for a race of intelligent cockroach-descendents to take over. I would hope that whatever fate befalls us - we'd have time to consider our legacy and build something so enduring that future species would be able to understand us. SteveBaker (talk) 11:00, 24 March 2009 (UTC)[reply]
NB: My reason for asking these questions is that if the answer is yes, then they add a positive component (which I've heretofore neglected) to, respectively, the total utilitarian value of humanity and the marginal utilitarian value of each new human born. Possibly even enough to shift the sign of these quantities from negative to positive. NeonMerlin11:06, 24 March 2009 (UTC)[reply]
That entirely depends on what you are measuring. This "utilitarian value" thing is nebulous at best and downright nonsense at worst! In order to define a "value" you have to know what you are measuring and why it's important? The universe doesn't give a damn what happens to us or what we do. This is merely a matter of philosophy - and this is the Science desk - not the standing-around-making-specious-arguments-while-being-a-waste-of-quarks desk. SteveBaker (talk) 11:32, 24 March 2009 (UTC)[reply]
In numerous science fiction works, humans have found ancient alien civilizations somewhere in the universe which had flaws leading to their own destruction. Us learning from their mistakes was a plot element, but was never a very convincing one. See also the poem Ozymandias. It would seem to be within our present technology to leave behind a better archive than the crumbling statue of Ozymandias, or some nonbiodegradable plastic bottles in a landfill and some nuclear waste casks. Take some durable substrate and archive a copy of Wikipedia, various great books, copies of world-class art and music, and park it on a space probe at the L3 point or on the moon, where it will be out of harms way for a few million years. Something like that was done on the Voyager space probe, by means of the Voyager Golden Record. Edison (talk) 13:49, 24 March 2009 (UTC)[reply]
We might ourselves be able to go pick up Voyager in a few years when faster space travel is possible. However, a new species which would evolve millions (if from chimps) or billions of years later would have a lot farther to go, since it's headed out into space, and wouldn't know where to look. If there are plastics that last forever, why can't we use them to record Wikipedia, etc. ? If no inks last that long, we could burn letters into plastic pages. Perhaps we could also make something like a DVD out of it, although that would be inherently more difficult for a future species to read, requiring that they create a DVD player. StuRat (talk) 14:22, 24 March 2009 (UTC)[reply]
If we kill ourselves through climate change and leave proof of it, than any new species that comes along will have proof that anthropic climate change can kill you, so they won't cause it. If we kill ourselves through nuclear war, it will a) give proof that nuclear war will kill you, which we know and thus must not prevent us from causing it, and b) tell them how to make nuclear bombs. By the way, this reminds me of a demotivator. — DanielLC15:07, 24 March 2009 (UTC)[reply]
(EC) Your question is very broad and has 2 very different main components. Aliens visiting our planet by definition have made it off their own dust ball. If our demise was due to the fact that we failed to establish a sustainable population elsewhere, they'd not be likely to make that mistake. (Said aliens presumable visiting our now empty world for that very purpose.) Local species would need time to evolve. Animals that are closest to us in the "use of tools" and "problem solving" department (e.g. chimpanzee, parrots) have only small populations left and it is doubtful that they will be able to multiply fast enough to become a dominant species. Animals with large populations (e.g. cockroaches, rats) will need time to evolve. By the time they get to a point of evaluating past events, there is likely to be very little left. They might dig up our "religious temple to energy" and start a traveling exhibit with our nuclear waste. Warning signs tend to be ignored, because risk taking is part of the process of developing s.th. new. (For example: Warnings on the walls of the pyramids were not paid much attention to.) Plastic will get crumbly after about 50 years, give or take. [11] It may make it for a couple of centuries under ideal conditions. Archiving Wikipedia in a durable manner would either require a consecutive population to produce backups on emerging technology or some advancement in data storage. Just consider what you'd do if you found a modern computer and a stack of punch cards, some magnetic tapes or a stack of floppy disks? ...and that would have been from within just a couple of decades. The magnetic storage will probably be unreadable anyway. CDs will merely last for about 5 years. Inscribing data in a crystal is still only a neat trick in the lab. History tells us that a) even things designed for the ages aren't necessarilyintelligible to others and b) very few blunders get avoided the second time around. (aka. History is repeating itself.) Taking what is left behind for a following civilization as the only measure for an individual's worth is a pretty measly standard. Usually his/her contribution to the species while it's still around and to it's future existence and well being might be better gauge. ("If you are going downhill, at least enjoy the ride." :-) 76.97.245.5 (talk) 16:20, 24 March 2009 (UTC)[reply]
Increasing population takes almost no time at all, when compared to the millions or billions of years it takes for new species to evolve. If a population can double every generation, which isn't that difficult in ideal conditions, that would mean it would increase 1000-fold in 10 generations, a million-fold in 20, and a billion-fold in 30. Given a 20 year time frame for each generation, that would only take 600 years. StuRat (talk) 17:33, 24 March 2009 (UTC)[reply]
600 years would indeed be under ideal conditions. It took humans considerably longer to make it from caveman to computers. Tool use and problem solving abilities help to reduce some population pressures, but by no means all. Natural selection is a lot more complex and messy than the simplified "survival of the fittest." Sometimes the fittest get their heads bashed in by the second fittest or they just can't get a prom date :-). One lowly pathogen can wipe out populations in entire areas, so simple mathematical progression doesn't quite apply. 76.97.245.5 (talk) 22:31, 24 March 2009 (UTC)[reply]
Modern humans (Homo sapiens sapiens) are only 200,000 years old, so our population increased from almost nothing to several billion in that time. While much longer than 600 years, that's still nothing compared to how long it would take another species to evolve on Earth to the same level of intelligence as we currently have. Even starting from chimps, which are 98% of the way there, it would still take millions of years. StuRat (talk) 23:57, 24 March 2009 (UTC)[reply]
So given the timescale for another species to evolve to replace us - and assuming it's not chimps or dolphins because they'll probably die right along with us when whatever befalls us comes - we'd probably have to find a way to preserve our Wikipedia backup for a billion years. Sadly, it's not just a matter of finding a good material to write it on. We couldn't count on avoiding vulcanism, earthquakes, continental subduction, rising sea levels, rock deposition, being ground to dust by a kilometer of ice in an ice age...one of those could bury our best efforts beyond the ability of any advanced race to find it. Putting it somewhere more quiet like the moon or one of the Lagrange points would make sense - but remember: that time-capsule that the super-intelligent race of dinosaurs left for us it still sitting in a crater somewhere and the backup copies at the two lagrange points are still there. So even at our level of development - there is no certainty that we'd find these information sources. If you are a pessimist - you might successfully argue that the time it takes a new species to find a carefully preserved archive could easily exceed the typical lifetime of a civilisation. SteveBaker (talk) 01:27, 25 March 2009 (UTC)[reply]
There's another good reason to leave that stuff at the Lagrange points, because when we get there we may find them cluttered with time capsules from all the previous civilizations. :-) StuRat (talk) 05:19, 25 March 2009 (UTC)[reply]
In my attic are boxes of punchcards, reels of magnetic tape,and floppy discs. There is also punched paper tape with a Fortran 2 program for a PDP-8. I have no doubt that all would be readable. Edison (talk) 04:42, 25 March 2009 (UTC)[reply]
How long do CDs last? I have some that are nearly 15 years old that work well, so I know its more then 5 years, but would they last centuries in a place like a bank vault? 65.121.141.34 (talk) 20:34, 24 March 2009 (UTC)[reply]
Plastics degrade rapidly when exposed to UV light, but I imagine they'd last far longer if buried. You'd probably also want to keep ground water away from them and bury them below the frost/freeze line. Hermetically sealed, under ideal conditions, I'd guess centuries, at least. StuRat (talk) 20:41, 24 March 2009 (UTC)[reply]
It depends very much on the specifics. In general, commercially stamped CDs last longer than writable media. But some early batches used an unsuitable glue, with CDs deteriorating after a few years only. --Stephan Schulz (talk) 20:47, 24 March 2009 (UTC)[reply]
I bought three CD's from the Philips Research Labs staff shop - about 2 months before the first CD players went on sale to the general public. All three still play just fine (In case you care - they are: Dire Straits: Brothers in Arms, Some Bach Fugues and a recording of Glenn Miller taken from the original pre-magnetic tape wire-recordings and remastered especially for CD). Those must be close to being the oldest mass-produced CD's in existence. There have been a few snafu's with disk manufacturers over the years - so some disks have behaved badly - but on the whole, they do pretty good. There is certainly no obvious fixed lifespan that you could point to. They don't all die after X number of years. (Mind you - I bet they are all three on about their tenth replacement jewel cases!) SteveBaker (talk) 01:08, 25 March 2009 (UTC)[reply]
There was a court case somewhere (EU?). The industry representatives were unwilling to guarantee their CDs for more than 5 years. So that's how long they think they'll last. That is for ones subjected to ordinary use, though. Under some carefully managed storage conditions they might last as long as the plastic stays intact. 76.97.245.5 (talk) 02:42, 25 March 2009 (UTC)[reply]
I have CD's from 1982, reel-to reel tapes from the 1960's, LPs from 1950, 78's from 1909, and cylinders from the 1890's which still play fine. It is a matter of preservation. Edison (talk) 04:37, 25 March 2009 (UTC)[reply]
There was one period where the formulation of the aluminium that's evaporated onto the disk to make the mirror-surface wasn't quite right - and CD's from many manufacturers over a period of several years had a tendency to develop tiny pin-holes in the aluminium layer - and (weirdly) an effect similar to surface tension in liquids was making the holes grow slowly over time - eventually ruining the disks. But once the problem was known, it was fairly quickly rectified - a lot of the bad press that CD's have had over the years can be attributed to that incident. SteveBaker (talk) 05:26, 25 March 2009 (UTC)[reply]
Fungus can also be a problem for CDs in some tropical countries, I've experience it personally and there are widrespread reports on the internet. It seems to eat the aluminium layer. See [12] as an example image. Nil Einne (talk) 11:17, 25 March 2009 (UTC)[reply]
As noted above, the commercially stamped media is generally far more durable than user writable CDs. The same chemistry the makes most writable CDs able to be encoded by laser heating also makes them degrade over time. I remember seeing a report that most writable CDs developed significant errors in under 5 years. This was even true of the CDs that had never been burned, they also became unusable after only a few years of shelf-life. That said, there are also some companies now that will sell you "archival quality" writable CDs. I have no idea if they really do the job, but I have heard of one company that even offers a 100 year guarantee which at least says they are serious. Of course, their product is also like $5 / disk as opposed to $0.25 for the cheap stuff that dies after a few years. Dragons flight (talk) 06:13, 25 March 2009 (UTC)[reply]
Certainly writable CD's have a short life - and indeed, their shelf-life is problematic even before they've been written to. I worked on the project that produced the first CD-ROM ever - we had to press the disks in a CD factory because the projected life of the early experimental writable CD technology was so short that it would be tough to get them out of the factory and into our hands before they stopped working! The 100 year guarantee is only for the value of the blank media - it's really no comfort at all when 20 years from now you find you've lost all of your data and all they give you is a couple of bucks to buy a new blank disk. SteveBaker (talk) 22:18, 25 March 2009 (UTC)[reply]
The only place that fingernail growth occurs is at the base. The entire hard part of the 'nail' is non-living; the nail extends as new material is deposited by the nail matrix: living soft tissue that sits under the nail. The visible portion of the nail matrix is the lunula, that whitish semicircular bit at the base of the nail. (The lunula may not be visible on all your fingers and toes, and it is often most conspicuous at the base of the thumbnail.) TenOfAllTrades(talk) 15:58, 24 March 2009 (UTC)[reply]
What's the hottest a human can stand for more than a few seconds?
the question on actually experiencing boiling water weeks back brough to my mind a story - don't recall where, but my money's on it being James Bond - where the bad guy locks the protagonist in a sauna or somesuch and knobs it up to about 165 degrees or so.
My question is, how much can the human body stand for more than a few seconds? I imagine the writer did some research on how high to have that turned up (why would one have the option to have it dangeruosly high, anyway?), but ISTR someone saying a really hot sauna can get up to 212 F, which is boiling? Is that really doable?
It makes me wonder about people near a blast furnace, too, where I imagine as you get real close it can be what, several hundred degrees? Or just what firefighters face, ignoring the problem of smoke.172.130.27.46 (talk) 15:44, 24 March 2009 (UTC)[reply]
This depends heavily on what the hot thing in question is. Hot metal, hot water and hot air of the same temperature will have different effects, due to differing thermal conductivity and heat capacity. A human can easily stand hot air at well above boiling temperature (try sticking your hand in an oven sometime), but boiling water is another matter. Algebraist15:50, 24 March 2009 (UTC)[reply]
Real Finland style saunas routinely go up to 100℃, and sometimes reach 110℃, significantly above the boiling point of water. People can stand this with low humidity for several to many minutes - the body manages to regulate its temperature fairly well for short periods of time. On the other hand, long-term exposure to 45℃ is very unhealthy, as is, of course, exposure to hot water quite a bit below boiling point. --Stephan Schulz (talk) 15:54, 24 March 2009 (UTC)[reply]
The key factor is humidity. In low humidity (such as the saunas Stephan mentions), the human body can cool itself very effectively through sweat even at temperatures significantly above the boiling point of water. In high humidity, sweat doesn't work, and you get into trouble at temperatures well below the boiling point of water - 50℃ will have you suffering severe heat stroke pretty quickly in tropical humidities if you aren't careful (and probably even if you are careful - without access to some form of refrigeration, at least an cool box full of ice, I can't see what you could do to survive more than a couple of hours, if that). --Tango (talk) 18:49, 24 March 2009 (UTC)[reply]
I remember reading in the Guinness Book of Records in the 1980s that humans had experienced temperatures of over 500 deg C in US Army trials and survived! Unfortunately the GBWR website is not at all search-friendly so I can't instantly confirm this. --TammyMoet (talk) 19:04, 24 March 2009 (UTC)[reply]
The melting point of Aluminium is 660.32°C, so not far off. I agree that 500°F is far more likely (that's 260°C - still rather toasty!). --Tango (talk) 20:45, 24 March 2009 (UTC)[reply]
Thanks; yeah, I thought of looking at Guinness, but yeah, their site isn't too easy to move around in? Wow, 500 degrees F is still amazing. the stuff on how much of a different humidity makes is really helpful, too. I'd have thought something that high would do something really bad to the blood or skin or somethingg even after a couple seconds; just like I've read putting one's hand in liquid nitrogen (or is that oxygen) freezes it instantly. (Then again, that's a liquid, but at that low a temperature, I think you'd get frostbite anyway.).209.244.187.155 (talk) 21:42, 24 March 2009 (UTC)[reply]
So my recollection is a little different. The way I remember it, they were NASA experiments rather than Army. The numbers I recall were that you could tolerate 400 F unclothed or 500 F if bundled up (at those temperatures a heavy jacket keeps you cool, relatively speaking). I don't know what the time frame was; I can't believe it was a really long time but presumably it was long enough to accomplish some task, or maybe make it through re-entry and have the ship pick up a living person rather than some barbecue. --Trovatore (talk) 21:59, 24 March 2009 (UTC)[reply]
There is a big difference between liquid nitrogen and air - liquid nitrogen conducts heat far better than air. If your skin ever got to 100 degrees, you would be in serious trouble within a fraction of a second, but heat doesn't go from air to skin very quickly so the body's cooling methods can prevent the skin ever getting hot enough to burn even when in direct contact with 200 degree air. --Tango (talk) 22:17, 24 March 2009 (UTC)[reply]
Putting your hand in liquid nitrogen doesn't freeze it instantly, anyway. It's perfectly possible to dip your hand in for a brief period without taking any harm (be very careful if doing this at home!). Algebraist00:38, 25 March 2009 (UTC)[reply]
Having had my face briefly immersed in a large propane flame (probably around 1000°F), walking through a turbocharged diesel exhaust plume from a military vehicle (about 400°F), and having inadvertantly swallowed drops of splashing liquid nitrogen, I can attest personally that you neither burn nor freeze instantly. My eybrows and eyelashes got singed, but otherwise I was unharmed. With the nitrogen, I was also unharmed. Frostbite can happen after a few seconds of liquid nitrogen exposure but for the most part it evaporates so fast it never directly contacts the skin (swallowing a drop results in belching out a white cloud of vapor a few seconds later). I highly recommend not trying any of this yourself. In my case, they were accidents. ~Amatulić (talk) 01:07, 25 March 2009 (UTC)[reply]
I've heard stories from friends of "liquid nitrogen fights" (similar to water fights). They splash it on each other, apparently with no ill-effects. While the thermal conductivity is pretty high, the thermal capacity of a small drop can't be much - there probably just isn't enough "cold" there to harm you. --Tango (talk) 20:25, 25 March 2009 (UTC)[reply]
Kind of continued from this thread. Do we know whether space is expanding all over the universe (i.e. all space around us is stretching) or whether it's just the outermost sections of our universe expanding? I mean is the space around us now, Earth, the Moon, expanding with the rest of space around the universe? I'm not even sure if this is testable or not, because if all space around us was expanding at the same rate as everything else, then it wouldn't be detectable. —Cyclonenim (talk · contribs · email) 18:41, 24 March 2009 (UTC)[reply]
The expansion of space on a local scale would be detectable (at least theoretically). We measure the distance to the moon, for example, by bouncing laser beams off mirrors left by Apollo astronauts and timing how long it takes for them to get back. The speed of light isn't changed by metric expansion, so we would notice the time taken increasing (actually, the moon is moving away from the Earth due to tidal forces, but that's irrelevant!). Gravitationally bound systems (anything on the scale of galaxy clusters or smaller) aren't expanding. That doesn't mean it is just "outermost" sections of the universe expanding (whatever that means - there is no centre to be far away from) - expansion happens on large scales, but not small scales. Any two objects a large enough distance apart will be moving away from each other, regardless of where they are in the universe. --Tango (talk) 18:57, 24 March 2009 (UTC)[reply]
It sure seems like there's an influx of "expansion of space" questions lately. Anyway, this is answered in the lede of the metric expansion of space article linked in the first answer of the above question: no, small-scale gravitationally-bound systems (including the Earth-Moon system and the solar system, but also including the Milky Way as a whole and yet larger systems) do not expand within themselves. As for detectability, the "measuring distance in a metric space" subsection addresses this.
However, along a related line, it's possible that all space (and other related constants) expand at a particular rate, shared equally, and that it's therefore completely undetectable. Of course, it's also completely irrelevant -- if everything continues to function in such fashion as if there were no inexplicable immeasurable force, then we might as well assume that there is not. — Lomn18:59, 24 March 2009 (UTC)[reply]
How would you define such an expansion? Our definition of "distance" depends on various constants, and the units we express those constants in depends on our definition of distance. I can't see how you could define things in a way that makes the kind of expansion you describe make any sense. --Tango (talk) 20:35, 24 March 2009 (UTC)[reply]
I don't know how it would work, either -- I'm just noting that while such a philosophical concept could be bantered about, it's not a meaningful discussion. I've seen a few thought experiments before along the lines of "what if everything is expanding, all means of reference included?" and thought it worth addressing why they're not really interesting. — Lomn20:54, 24 March 2009 (UTC)[reply]
People have already kind of said this, but anyway: your questions would make sense if space were more like a substance (a liquid or a gas or a loaf of bread), but it isn't. Space does have some properties of its own (like curvature), but it doesn't satisfy a continuity equation—it isn't "conserved". If you have a liquid-filled region that's getting larger, it makes sense to ask whether it's because the existing liquid is expanding or because more liquid is being added at the edges. You can distinguish those two cases because you can trace the motion of the liquid over time—you can draw worldlines in spacetime showing what happens to individual bits of liquid. If the liquid region is getting larger then either the lines must be diverging from each other or someone must be adding new lines at the edge. When you're talking about expanding space you still have the spacetime but not the lines in it, so that distinction disappears. Galactic superclusters have worldlines and they're generally diverging, so the gas of superclusters is expanding (and it really is very much like a gas, strange as that may sound). Smaller objects within the superclusters have their own worldlines and those are not generally diverging (within a single supercluster), so individual superclusters are not expanding. -- BenRG (talk) 19:11, 25 March 2009 (UTC)[reply]
Hmm... as I understand it, a simple answer to your question doesn't exist: there is no universal "rate of expansion". We suspect that much of the universe is, due to expansion, now beyond our light horizon. As such, it is unknowable to us (save that it has receded at a rate greater than c). Within the observable universe, the rate of recession varies object to object; however, scientists currently believe the general trend (the deceleration parameter) is that those rates are increasing. — Lomn19:21, 24 March 2009 (UTC)[reply]
Locally, things can't travel faster than the speed of light, but on cosmological scales it doesn't quite work like that - you can think of it as the galaxies staying still and space being created inbetween them (BenRG will tell us this isn't the case, but I'm still not convinced!). --Tango (talk) 00:30, 25 March 2009 (UTC)[reply]
Well, it isn't the case but it isn't not the case either. It's just meaningless to ask whether space is being created as far as the theory is concerned. What worries me is saying that space is being created in some cases (the supercluster motion) but not other cases (other relative motion), since that distinction doesn't exist in the theory. -- BenRG (talk) 19:22, 25 March 2009 (UTC)[reply]
I realize, but space is, at least locally, homogenous, so shouldn't the observed values be the same everywhere in our observable universe? I know that most scientists believe that the rates are increasing; I am looking for the exparimentally measured redshifts that back this up. *Max* (talk) 20:12, 24 March 2009 (UTC)[reply]
There is a universal rate of expansion (or large enough scales), it's just proportional to separation. See Hubble's law. It is theorised that Hubble's Constant varies over time (increasing due to dark energy, decreasing due to gravity - observations suggest more of the former than the latter, so a net increase). I can't find any estimates of its value at other times than now, though, sorry. --Tango (talk) 20:30, 24 March 2009 (UTC)[reply]
According to the ΛCDM model, the value of the Hubble parameter at different times is given roughly by , where t is the "time since the big bang" (see Age of the universe#Explanation for what that means) and k ≈ 1 / (11 billion years). The image on the right is a graph of the coth function which I found on Commons. The x < 0 part isn't physically meaningful. The present day (14 billion years after the big bang) is in the vicinity of x = 1.2. The horizontal asymptote (y = 1) corresponds to a Hubble parameter of around 60 km/sec/megaparsec. Three caveats: (1) I didn't find this in a textbook, I derived it from the Friedmann equations and I may have made a mistake; (2) it's only valid for t > a few thousand years, before that other physics comes into play; (3) it's only valid in the future if the ΛCDM model is correct, and there's not enough data yet to be sure of that. -- BenRG (talk) 13:43, 25 March 2009 (UTC)[reply]
I used the first Friedmann equation in the form given at the bottom of Friedmann equations#The density parameter. I took (consistent with the evidence) and (close enough for t > a few thousand years) and plugged the rest into a CAS, which found the solution . (I've been basing Ref Desk answers on that formula for ages, so I hope it's right.) Then H = a'/a. The factor of 2/3 comes from the exponent. It's canceled by the 3/2 from inside the sinh, but I absorbed that factor into my k. -- BenRG (talk) 19:23, 26 March 2009 (UTC)[reply]
Looking at earth from near another star, how bright would it seem? Brighter than the sun? One of the brightest things in the sky? I would like to ignore the time delay caused by the speed of light and assume that the radio brightness in 2009 is what is observed. 78.146.178.204 (talk) 23:01, 24 March 2009 (UTC)[reply]
The only terrestrial signals likely to be detectable from another star are those intentionally sent into space - either specific attempts at signalling to aliens, or from studies of planets and asteroids using radar. Those could only be detected if they were pointed directly at the star in question. So, from virtually all stars, the Earth would not be visible in the radio spectrum. If one of these radar signals happened to go to the star, I'm not sure how bright it would be - it would, obviously, depend on how far away it was, but I'm not even sure how it would compare to the Sun... --Tango (talk) 23:32, 24 March 2009 (UTC)[reply]
Using our current technology, detecting an Earth-sized planet with a level of technology similar to ours (i.e. looking at "earth from another star") would be impossible on any level, and at any frequency, visible or radio or any other. Earth is just too small. Nearly every extrasolar planet we have found has been basically a Jupiter-sized planet orbiting at rediculously close distances; such planets cause their parent stars to "wobble" and also "dim" as they pass in front of it. From a distance of a few light-years or more (remember the closest star to us is about 4 light years away) Earth would be entirely undetectable. Looking for the Earth would be like trying to resolve a specific grain of sand on a beach if viewing the beach from the moon. We are REALLY small, and we just don't give off enough general radiation to be detectable, and we don't reflect enough light, block enough of the sun's light, or gravitationally effect the sun enough to be seen. MAYBE an outside-of-the-solar-system viewer could detect Jupiter, but not earth. Possibly, if we were beaming a tight, high energy radio signal directly at another star, it could be detected, but otherwise we would be invisible. --Jayron32.talk.contribs01:41, 25 March 2009 (UTC)[reply]
I seem to recall that there have been at least two signals intentionally sent into space from radio telescopes which would have made the Earth far brighter than the sun. I strongly question the wisdom of such efforts to call attention to us. Edison (talk) 04:28, 25 March 2009 (UTC)[reply]
I'm picturing a tentacled, drooling alien creature noticing the radio emissions from Earth, then heading our way as he straps on a bib... :-)
Well - if he's that hungry, he may be in a lot of trouble because getting here is (in all likelyhood) going to take a couple of centuries. SteveBaker (talk) 05:20, 25 March 2009 (UTC)[reply]
Yes - that's true - the actual amount of power in those transmissions isn't really that great - but being sent from a radio telescope means that the beam is highly directional...I forget which stars they were aimed at - but only beings orbiting around those stars would have any chance of seeing the signal. For the rest of the universe, the earth would still have been pretty much invisible. There are other people claiming to do this though - there used to be (and maybe still is) a company on the web someplace that'll beam any short ASCII message you care to give them out in some direction or other for just a few bucks. Aleksandr Leonidovich Zaitsev[13] has been sending all sorts of things out on a really powerful narrow-beam transmitter. So this does happen...but the odds of anyone out there picking it up are really slim. SteveBaker (talk) 05:20, 25 March 2009 (UTC)[reply]
If you add up the power of all the radio, tv, and other radio-wave type emmissions (including those from power lines or electrical wiring, even thunderstorms) it must be a lot. Either it gets absorbed, or it leaks into space. I'm wondering how this would compare with the power of similar wavelengths from the sun - if these emmissions from modern technology would be a beacon in some wavelengths. 89.243.177.130 (talk) 11:39, 25 March 2009 (UTC)[reply]
You have to remember that numbers that may be enormous by human view-point, can be miniscule by astronomical standards. Some order-of magnitude comparisons:
So even if you assume that all energy generated/consumed by man is radiated out into space, it would be much smaller than the reflected solar radiation, and about 0.000000000001×total solar radiation. This should give you some idea of the difference in magnitudes we are talking about!
Of course these calculations will change, if the radiation from Earth is very narrowly directed in terms of its frequency or direction, but barring that detecting Geo-radiation from another star is a long shot, if not completely hopeless. Abecedare (talk) 19:31, 25 March 2009 (UTC)[reply]
Frequency is the key consideration - the Sun emits enormous amounts in the visible part of the spectrum, but orders of magnitude less in the radio frequencies. A unidirectional radio transmission from the best technology we have would be detectable by the best technology we have from other stars (I'm not sure how distant those stars could be, though - the other side of the galaxy might be a challenge, but the time required for a signal to get there makes it irrelevant). If we sent a visible light laser beam to another star, I doubt they would notice. --Tango (talk) 20:30, 25 March 2009 (UTC)[reply]
March 25
Radioactive sickness?
I am writing a research report on radioactive sickness. But when I search on Google I also get radiation sickness in my resaults. Is radioactive sickness and radiation sickness the same thing? —Preceding unsigned comment added by 174.6.144.211 (talk) 00:59, 25 March 2009 (UTC)[reply]
I got a topic on Aleksandr Litvinenko's poisoning and was asked to write a report on radioactive poisoning, as this is what happened to him. But, as i mentioned before, i am not sure whether or not radioactive poisoning and radiation poisoning is the same thing, sine they both pop up when i search for radioactive poisoning. —Preceding unsigned comment added by 174.6.144.211 (talk) 01:12, 25 March 2009 (UTC)[reply]
Litvinenko died of radiation poisoning. I think whoever it was that said "radioactive poisoning" just make a mistake. --Tango (talk) 01:27, 25 March 2009 (UTC)[reply]
All these phrases are talking about the same thing, but "radiation sickness" is the proper name for it. It's not really a kind of poisoning, although people talk of it that way. (Poisons injure the body in different ways than radiation does.) --Anonymous, 01:32 UTC, March 25, 2009.
(after multiple edit conflicts) We have an article on this incident, Alexander Litvinenko poisoning. The name for what he died from is radiation poisoning. It is surmised that this was caused by the ingestion of a radioactive substance, rather than from exposure to an external source of radiation. One could call it "radioactive poisoning" in that he was poisoned by a radioactive substance as opposed to a toxic chemical such as cyanide or a neurotoxin of some sort. However, there is no real difference between what killed him and what killed the victims of the Chernobyl disaster; the only distinction is the means by which he was exposed to the lethal dose of ionizing radiation. - EronTalk01:34, 25 March 2009 (UTC)[reply]
Yes, it does. It doesn't matter where the radiation comes from or how it gets to your tissues, the effect is still called radiation poisoning/sickness. --Tango (talk) 01:55, 25 March 2009 (UTC)[reply]
Yes - my earlier response may have added some confusion here. I was speculating as to why someone might call what happened to Litvinenko "radioactive poisoning" - I didn't mean to infer any difference between internal and external sources of radiation. - EronTalk02:26, 25 March 2009 (UTC)[reply]
No. Radiation poisoning (not "radioactive poisoning" - that is not the proper name for it) is caused by exposure to high levels of ionizing radiation. There is no genetic component to it. - EronTalk02:28, 25 March 2009 (UTC)[reply]
Does nuclear warfare, nuclear reactors, radioactive materials and gamma rays cause radiation poisoning because they realease ionizing radiation? —Preceding unsigned comment added by 174.6.144.211 (talk) 02:36, 25 March 2009 (UTC)[reply]
I wrote a good chunk of the Alexander Litvinenko poisoning article - it's an amazing story, the closest thing to a classic Hollywood spy story you'll ever see in real life. But what was significant here is that Polonium-210 (which is the radioactive material that was mixed into Litvinenko's tea - and which eventually killed him) - is not normally particularly dangerous stuff. In fact, you can buy significant quantities of it in anti-static lens cleaning equipment from any decent camera store. It's radioactive - but only emits alpha radiation - which is stopped by a single sheet of paper. Even if you get Polonium-210 directly on your skin - the layer of dead skin cells that covers your body is quite enough to stop the radiation from harming you. What's dangerous is only if you eat (or in this case, drink) the stuff (or perhaps breathe it in as a fine dust in large enough quantities). That spreads it throughout your body and gives the alpha radiation a way to irradiate living tissue. I suspect that is the reason why everyone calls it a 'poisoning' - it's not at all like standing a foot away from a chunk of plutonium and getting irradiated. It only took a couple of days for Litvinenko to show symptoms bad enough to put him in hospital - but it was close to three weeks until he eventually died. For the majority of that time, it was thought that he had been poisoned with non-radioactive Thallium - because although his symptoms were classic symptoms of radiation sickness (nausea, hair falling out, that kind of thing) - there was no measurable radiation coming from his body. So they looked for more conventional poisons that produce that set of symptoms, and thallium popped up. But again - this is probably why the term "poisoning" was initially kicked around and kinda stuck - even after it was realised that this wasn't strictly a poison. The thing that's particularly chilling about this is that the murderer could have used any of a dozen - much easier to obtain - poisons in Litvinenko's tea. This one is so unique and trivially easy to trace (it has to be made in a nuclear reactor - and there are only two sources of it - one Russian and another American - but the isotope ratios make it abundantly clear that this is batch is Russian - and that it was made very soon before the poisoning took place (suggesting that the stuff hadn't been smuggled through long, complicated chains of black-market dealers). The Russians aren't stupid - they'd have known that this particular technique for killing him would be instantly traceable back to them. So it's clear that the point of the exercise was to send a message: "You aren't safe from us anywhere - and we don't care that anyone out there knows that we do this kind of thing."...that's real cold-war stuff! What we don't know is who, specifically, this rather gruesome message was intended for...whoever that is - is evidently keeping a much lower profile! Anyway - enjoy reading the article - and be sure to follow the links to the 150 or so references at the bottom - there is much more to be learned here! SteveBaker (talk) 05:03, 25 March 2009 (UTC)[reply]
(Nitpick: Plutonium is not that radioactive—a lot less so than Polonium-210. You won't get irradiated from standing a foot away from a chunk of it assuming the chunk is not a critical mass. As with Polonium, it is a radiological danger primarily as an alpha emitter that you might inhale. Eating it isn't even really a problem—it passes out of the system rather quickly—it is only a serious problem if it gets into your lungs or bones. Also I would dispute that Polonium-210 is not "normally dangerous stuff"—the amount in anti-static brushes is quite small. You don't need much of it, in terms of mass, to have a problem. It is far more toxic than uranium, for example. It is not as bad as a fission product. But it is still stuff to handle with care in any significant amount.) --140.247.240.69 (talk) 18:43, 25 March 2009 (UTC)[reply]
The claim that Polonium-210 is present in 'significant quantities' in antistatic brushes is somewhat misleading. The largest brush sold by these guys has about 500 microCuries of Polonium, which according to our article is about a tenth of a microgram. That's more than enough to kill you if you decide to eat it, but is nonetheless a pretty small amount. If you actually had a decent-sized chunk of it (a gram, say) on your skin, then your initial problem would be the way the intense heat was burning through your skin. Algebraist11:17, 26 March 2009 (UTC)[reply]
Did Litvinenko suffer from chronic radiation syndrome or acute radiation syndrome? and why?
In Flight Pitch Control / Dive or Stall
Can someone with knowledge of the principles of flight help me understand something? A UK company named Parajet is building a flying car of sorts called the SkyCar. At the link the above, they make the following statement about the SkyCar:
"It has no pitch control and therefore (is) impossible to stall or dive."
So what is it about having pitch control in fight that makes stalling or diving possible? Why would its absence prevent these situations? Appreciate any input. Wolfgangus (talk) 01:23, 25 March 2009 (UTC)[reply]
"Pitch control" means being able to control what angle the nose is at in a vertical direction. Obviously, that is required to dive - diving is pointing to nose steeply downwards. Stalling is caused by trying to climb too steeply (or not descending fast enough if you're going quite slowly). Presumably this flying car sets its own pitch, somehow, at a level somewhere below where it would stall. (I guess you then control altitude by varying speed - slow down to go down, speed up to go up. However, that would mean it must be possible to either stall, or dive - if you cut the engines, one of those two things has to happen.)--Tango (talk) 01:32, 25 March 2009 (UTC)[reply]
I imagine they just mean it is possible for you to cause a dive or stall by applying too much upward or downward pitch. --Anonymous, 21:35 UTC, March 25, 2009.
Actually, I take my last statement back - cutting the engines wouldn't be sufficient, you would probably need some way to actually brake to get slow enough for the only non-stalling configuration to be a dive. --Tango (talk) 01:36, 25 March 2009 (UTC)[reply]
What stalls a plane is when the pitch of the wing to the airflow is too steep. If you pitch the plane up and have plenty of engine power - the plane climbs and the airflow remaines pretty much parallel to the wing....but if you pitch the plane up without enough power applied - you get into a vicious circle where the wing loses lift - you start to fall downwards - which means that the airflow is now somewhat upwards - which further increases the angle of pitch to the airflow - which increases the drag - which slows you down - and the pitch angle to the airflow increases still further - until you're simply falling like a rock. What's suspicious about this claim is that even without pitch control - if you slow the motor down enough then the roughly 4 degrees of upward pitch (which you pretty much have to have built into the wing to make the plane fly) - is enough to cause a low-speed stall. The way you recover from such a stall is to push the nose down and (if you can) you apply power. Without pitch control - if your engine fails - you've got no means to recover from the stall and you're going to crash.
There is a means to fix this problem - and that's to have a 'canard' design - where the pitch control happens on surfaces in front of the main wing and with a slightly steeper pitch than the main wing. What happens then is that if your speed drops, the little 'canard' wings stall before the main wing can - when the front wings stall - they lose lift - the nose falls - and that automatically reduces the angle of attack - so they immediately un-stall without any input from the pilot. Of course if you lose the motor - the plane is going to nose down into the ground...but it won't stall - so you stand at least a chance of pulling out of the dive when you've built up enough speed.
The other odd thing about not having pitch control is that you can't fly faster or slower...if you add power without altering your pitch - you'll climb - and if you reduce power without changing pitch - you'll lose altitude. At a particular pitch there is only exactly one speed that'll keep you flying level! I find it hard to believe that this contraption really doesn't have some means to control pitch - I imagine that what they REALLY mean is that the pilot has no direct control over pitch - it's hard to believe that the flight computer can't control pitch.
I definitely agree with Steve here, the only reasonable explanation is that the pilot has no direct control over pitch. There must be a mechanism for pitch control for the airplane to be flyable. If there were no pitch control, a steady altitude could only be maintained at one speed, which would be a complex function of weight, center of gravity, and air density. It would even change during flight as fuel is consumed, or even if a passenger leans forward in their seat! In turbulent air natural stability would be the only way to maintain attitude (and therefore altitude). It's even possible that in turbulence near the ground, the aircraft could be put into an attitude where recovery with no pitch control is impossible. Finally, pitch control would be necessary to flare into the proper attitude for landing. So pitch control is basically required for any airplane, even if the pilot has no direct control. anonymous649403:43, 25 March 2009 (UTC)[reply]
Thanks so much for the solid feedback, and that's right- a powered parachute, although the term - the entire field actually - is new to me. There are clearly some pretty substantial differences between this vehicle and the Terrafugia Transition but I was assigned to write a feature about the SkyCar and was told it was a flying car plain and simple. Evidently that's not the case at all. Wolfgangus (talk) 06:57, 25 March 2009 (UTC)[reply]
The Parajet Sykcar doesn't look like it has no pitch control. It looks like a powered parachute, which I would think can be stalled given enough effort. I wonder if the statement was about the Moller Skycar M400, about which is said "the pilot's only inputs are speed and direction". It would certainly lack pitch control. DJ Clayworth (talk) 21:23, 25 March 2009 (UTC)[reply]
The Moller contraption certainly has pitch control inside the computer system - but the pilot has very little to do with flying the machine at all. Mostly he enters a destination and lets the computer do all of the flying. But the Moller gets most of it's lift from the half dozen thusters - it's not particularly aerodynamic...and it doesn't really work. Beyond a few hover tests, it hasn't done much flying. They sold the prototype under the condition that whoever bought it would not allow it to be flown again. SteveBaker (talk) 22:54, 25 March 2009 (UTC)[reply]
Mount st Helens
hi,
i think i heard somewhere that when mt st helens erupted in 1980 that it released more corbon dioxide into the atmosphere than humans have done to date. Is this at all true or not?
And the SO2 levels can be higher than those created by humans in the immediate surrounding area, but not when compared to all the sulfur dioxide created by humans worldwide. Also, volcanoes are an occasional thing, while human industry is relentless in adding pollution. So, you might want to evacuate the area around a volcano, during an eruption, because of all the pollution it puts out (among other reasons), but volcanoes are bit players on the world stage. There is, however, something quite rare called a supervolcano which is entirely different. StuRat (talk) 15:51, 25 March 2009 (UTC)[reply]
I site I looked at said the less than 1% of CO2 came from volcanoes - compared with SO2, about 1/3 of which (17 million tonnes) comes from volcanoes (that is a rough estimate on several counts). - Jarry1250(t, c)21:08, 26 March 2009 (UTC)[reply]
Just keep the bottle cold or: "Benzene can form in soft drinks containing vitamin C, also called ascorbic acid, and either sodium benzoate or potassium benzoate." That is more likely to cause cancer than sterility (Even for high doses our article says "not known".) Soft drink companies are scrambling to reformulate their beverages, so check the label. This is one of those things where the hype is bigger than the known study result. Should have known we have an articleBenzene in soft drinks. - 76.97.245.5 (talk) 14:20, 25 March 2009 (UTC)[reply]
A chapter in an article I'm reading is called: Endocrine stress system. It says: The basic components of the stress system include: - the locus ceruleus/noradrenergic sympathetic system; - the hypothalamic-pituitary-adrenal axis.
However, I wonder if the LC/NE sympathetic system is neural and not endocrine? Lova Falk (talk) 11:55, 25 March 2009 (UTC)[reply]
Thank you, but I'm just getting more and more confused. In the article on norepinephrine it says: "As a stress hormone, norepinephrine affects parts of the brain where attention and responding actions are controlled." As far as I understand, a hormone is released into the blood stream. So norepinephrine is released into the bloodstream, the blood travels to the brain and the brain gets more attentive. Is that really correct? I thought that norepinephrine affected the brain as a neurotransmitter.
The article also says: "It (norepinephrine) is released from the adrenal medulla into the blood as a hormone, and is also a neurotransmitter in the central nervous system and sympathetic nervous system where it is released from noradrenergic neurons." Isn't it more correct to say: "It is released from the adrenal medulla into the blood as a hormone, and it is released from the locus ceruleus as a neurotransmitter in the central nervous system and sympathetic nervous system." ??? Lova Falk (talk) 10:11, 26 March 2009 (UTC)[reply]
vegetable oil for fuel
pls i would want to know what properties of vegetable oils are compatible with that of fuel.i means what properties of vegetable oils makes it possible to be used for fuels —Preceding unsigned comment added by Peaceobioma (talk • contribs) 12:15, 25 March 2009 (UTC)[reply]
Note that it's not economical to use new vegetable oils for fuel, as they cost far more than other fuels. However, waste vegetable oils, such as those collected from the fryers in fast food restaurants, can be economical, after filtering, but only for a small segment of the fuel industry, as waste vegetable oils aren't produced in the quantities needed to supply all our fuel needs. One side benefit, the exhaust smells yummy (although that could be a negative if it makes you always hungry). :-) StuRat (talk) 15:37, 25 March 2009 (UTC)[reply]
The current price of Malaysian palm oil is about 500 USD per metric ton, which is comparable to a petrolum cost of about 65 USD per barrel. The current price of crude oil is a bit more than 50 USD per barrel ([15]). At those spot prices, a switch to biodiesel could be economical right now if supported by relatively minor government incentives.
That said, palm oil experienced a temporary price spike last year (up to just over 800 USD per ton) due to a combination of drought and intense interest in biodiesel; it's price over the last few years has also been lower than 300 USD per ton. Meanwhile, the price of crude oil has also rollercoastered over the last few years, running as low as 20 USD at the start of this decade, and spiking above 145 USD per barrel last summer. Neither type of oil has been a poster child for price stability of late.
So it's a bit of an overstatement to assert that non-waste vegetable oils are inherently uneconomic. While capacity to produce such oils certainly doesn't exist to replace all fuel uses of petroleum overnight, it is by no means a foregone conclusion that a gradual transition is impossible — nor is such a transition even unlikely. TenOfAllTrades(talk) 16:27, 25 March 2009 (UTC)[reply]
Using foodstuffs as fuel is an inherently bad idea, as the recent US experiment with using corn to produce ethanol shows. The price of corn skyrocketed, making ethanol cost more than gasoline, even at it's peak prices. Meanwhile, food prices went up dramatically as a result, since growing corn became more profitable than other crops, due to government subsidies. Also, there's the argument that it's immoral to burn food to run cars when people are starving. Finally, there's the infrastructure problem. Refineries and gas stations could be modified to provide biodiesel from palm oil, but that would be an enormous expense which would only be justified if this approach would be economical in the long run, and there's no sign that it would be. That leaves people to buy palm oil on their own and produce biodiesel, which ends up being far more expensive, unless you start with waste oil. StuRat (talk) 17:21, 25 March 2009 (UTC)[reply]
Using the wrong foodstuffs as fuel is an inherently bad idea, as is attempting to make the changeover too quickly. See ethanol fuel in Brazil for one case where it was done properly and successfully. The United States' example is simply a perfect demonstration of exactly the wrong way to manage the transition. Extracting ethanol from corn has a much lower energy output per cultivated acre of land – and indeed may be negative net output once the energy costs of harvesting, fermentation, and refining are factored in – compared to Brazil's sugar cane ethanol or tropical palm oil. The U.S. system of farm subsidies (for corn and other products) badly distorts the market, and probably encouraged even more farmers to make an ill-advised switch to corn. About the only thing the U.S. approach has going for it is that it has encouraged the development of infrastructure (from refineries and gas stations to individual flex-fuel motor vehicles) which can cope with ethanol and ethanol-blended fuel. That will pay off in spades if cellulosic ethanol (from switchgrass, most likely) or another technology matures sufficiently to provide large amounts of sustainable ethanol.
Replacement of diesel with biodiesel would require no changes for end users or distributors; they're equivalent products for virtually all uses. The same supertankers that carry crude oil from Alaska and the Middle East can carry biodiesel or unrefined palm oil from the tropics. The same gas pumps which deliver diesel can pump biodiesel. The same city bus that belches diesel soot will run happily on biodiesel.
Yes, different refining equipment would be required for biodiesel compared with conventional diesel, but that's not a problem. Refinery capacity can be built to keep pace with the supply of suitable oils — and minimal refining of edible oils is required compared to the refining required for most petroleum products. Biodiesel can be blended into the petroleum diesel supply chain at any point after the products are refined. If anything, you've missed the most significant infrastructure hurdle, which is that most private motor vehicles don't currently burn diesel. Still, that's a problem that can resolve itself over a period of many years, as the cost of biodiesel declines. TenOfAllTrades(talk) 18:37, 25 March 2009 (UTC)[reply]
In the US, at least, most fuel is gasoline, so the goal would be to replace that. Isn't biodiesel thicker than gasoline ? That would make me think new pumps would be needed. They also need to add biodiesel to the selection switch or add separate dedicated pumps for it. Also, unless they intend to no longer carry regular gasoline (which sounds like a foolish idea in the short term), gas stations will need to install new tanks for biodiesel storage, unless they just happen to have a spare tank already installed. For those stations which already have regular diesel, they could switch those pumps over to biodiesel rather easily, but that's only a small portion of stations (most of which which cater to truckers) in the US. And building new refineries is highly problematic in the US, as nobody wants one near them. StuRat (talk) 22:56, 25 March 2009 (UTC)[reply]
Picky, aren't you? Any filling station pump that can handle regular diesel can pump biodiesel. Any underground tank that is compatible with gasoline and diesel can quite comfortably accommodate biodiesel. If a facility already pumps diesel, there's no barrier to biodiesel at all — just start filling the tanks with biodiesel. Contrary to your claim that only a small portion of filling stations offer diesel, a 2005 study pegged the fraction at 42% in the United States: [16]. (That represents a sharp increase over the 30% which offered diesel in 2000; by now the fraction is probably over one half.)
Most filling stations in the United States dispense multiple grades of gasoline (typically one 'regular' unleaded and one or two 'premium' higher-octane options). If demand existed, a gas station owner could choose to drop one of the premium grades of gasoline and dispense (bio)diesel instead. All of the in-ground plumbing would remain the same. (The U.S. had a similar experience twenty or thirty years ago with the phase-out of leaded gasoline, and much of that multiple-fuel infrastructure is still in place.) Pumping equipment is repaired and replaced on a regular schedule; a switchover from gasoline to diesel is relatively straightforward.
Yes, most personal motor vehicles in the United States use gasoline — but that would gradually change if biodiesel offered a consistently lower-priced, carbon-neutral alternative. (Slow, steady growth of the biodiesel market will also ease the economic dislocations that could result from a more rapid shift in demand. If cellulosic ethanol turns out to work in the meantime, that's great — we don't have to have all the eggs in one basket.) The distribution infrastructure works equally well for diesel or gasoline, so it's a matter of raw ingredient supply and refining capacity. Build the refineries in the tropics if you can't get the NIMBYists to let you build them in the States—diesel is much safer to transport than refined gasoline. TenOfAllTrades(talk) 03:18, 26 March 2009 (UTC)[reply]
The food vs fuel issue is a perpetual one and is not IMHO a simple matter. Firstly the causes of the 2007–2008 world food price crisis are in great dispute as the article testifies too. IMHO fuel demand was a factor but I personally doubt it was the primary factor rather it was a large combination of factors and blaming biofuels was a convient excuse for a large number of people with different purposes. Regardless though, as TOAT testifies, you can't lump all food crops together. For starters while palm oil is in widespread use, it's a controversial oil because of it's high saturated fat content. While there are obvious some cases when you would want that, in many other cases its use is controversial. Of course there is some demand from those who believe the health problems caused by saturated fats, particularly saturated fats from vegetable oils may be overrated (perhaps due to the influence of money from other oil producers who tend to be in the developed world on scientists) as well as from those who believe that when polyunsatured oils are used for cooking they produce transfats or free radicals in sufficient amounts that it is better to use saturated oils. Regardless though, whether palm oil will, or should have a role as a major food crop in the future is an area of much debate. More importantly, as the world food price crisis testifies to (for example, the price of rice and other food not used to make biofuels to any great extent were also greatly affect), just not using food crops doesn't actually help in itself. If the non food crops used to make biofuels takes over the land of food crops, as will happen if they fetch a better price, then that doesn't help it makes things worse. At least if you are using food crops you still have the food you just have to pay more for it. There is some suggestion that you can use things like jatropha which it is hoped will not compete for land with food crops but this remains an unproven suggestion. There's also the hope we will be able to use all the waste material from plants that currently goes to waste, but this will obviously include food crops such as palm oil. There's also the question of whether it's fair to refuse to use biofuels, if you aren't actually subsiding them solely for your desire to not raise food prices when effectively what your preventing is farmers (many in the developing world) from getting a fair market price for their goods as well as effectively discouraging people from farming. This gets into a whole raft of complicated issues like agricultural subisidies, globalisation, protectionism, food security and competiting interests in the developing world. Let's not forget that one of the reasons why corn was so cheap is because of US government subisidies and many people have argued the US government effectively outcompeted many developing countries leading to a great fall in their agricultural production which has had numerous ill effects. (The EU also of course has large subsidies and had been blamed for many of the same problems in different areas, e.g. sugar beet.) Of course one of the great concerns with palm oil is whether it's current development is sustainable, but again this gets in to a whole raft of complicated issues like whether it's fair to demand the countries in developing world keep their rainforests when they could be getting a better return by replacing them (particularly when many developed countries have cut down a significant portion of their natural forests), what length of time we're referring to as well as how any future Kyoto protocol will develop (I think there's great concern parts of it will be based on the level of forests at some set point of time which is not going to seem fair to those who have preserved their forests). Of course if we bring biofuel subsidies in to the mix, it gets a lot more complicated. N.B. I recall reading that Malaysia was planning to develop a processing plant for making biodiesel from pa
'Around 7' is about right. The density of crude oil ranges from about 0.8 to 0.9 grams per cubic centimeter [17]. A barrel of oil is 42 US gallons or about 160 liters; the weight of a barrel is therefore 130 to 145 kilograms (roughly). At an even 1000 kilograms per metric ton, that's about seven barrels to the ton. TenOfAllTrades(talk) 18:39, 25 March 2009 (UTC)[reply]
Note that comparing tonne to tonne or volume to volume is pointless in itself. We need to consider the energy density of the fuels. Our Energy density article gives a slightly higher energy density for crude oil compared to biodiesel but I'm not sure how palm oil which hasn't yet been processed in to biodiesel compares. On the other hand, palm oil can be used as a fuel with relatively little processing I believe Nil Einne (talk) 01:55, 26 March 2009 (UTC)[reply]
Red decoder screen reveals blue text?
Which exact shades of red and blue should somebody optimally use to make one of those decoder things? If I am not mistaken, it is often text or an image printed in blue ink, then hidden by red "noise". When you put a certain kind of red transparency over it, the red is filtered out and the text or image comes out clearly. Is there a certain shade of blue or red that work best for this? Pantone or otherwise? etc. Are the red screens usually made from a certain type of plastic or other material? --Sonjaaa (talk) 19:04, 25 March 2009 (UTC)[reply]
You want to ideally have a color to match the red noise. When something is red transparent, it appears red because it is reflecting the red portion of the white light in the room back at you. Being transparent, appart from this it is letting all other light through. So when you hold it up to the decoder you want it to reflect the red noise and let the blue noise through, so a color most similar to the one of the noise you want to filter out is best.
If you are trying to print your own, I'd make sure to use just ink from the red color cartrage and just ink from the blue color cartrage. What you want to avoid is having multiple frequencies of light mixed together. Generally a clear red plastic is easy and cheap to produce. Anythingapplied (talk) 20:56, 25 March 2009 (UTC)[reply]
That's a very complicated - and entirely wrong - explanation! It's nothing to do with the film reflecting light. Red film allows red light to pass through it - and blocks all of the other colors. So when you look at (say) blue writing on a white background - the blue light is blocked - so the writing looks black - the white paper looks red because all of the other colors are filtered out. Hence you see black writing on a red background. The choice of color for the 'blue' should be something as far from 'red' as possible - so a sky blue would probably be the best choice - it is on the opposite side of the 'color wheel' - the complement to red. Inkjet printers have magenta, cyan, yellow and black inks - none of which is a particularly good match for the red filter. But printing a red/cyan picture should work pretty well. SteveBaker (talk) 23:33, 25 March 2009 (UTC)[reply]
Optical inversion, but not reversal?
I just bought a projecting alarm clock. It has a projector which can be aimed to project the time onto the bedroom wall or ceiling. There is a switch to select the colour of the projected time: red, blue, or green. The projector, from my (external) investigation, consists of red, blue, and green LED emitters behind an LCD shadow mask, and a simple, manually-focusable lens at the front. The shadow mask is inverted from ordinary pocket calculator or wristwatch LCD operation; the background is black, and the digits — made up of standard 7-segment-bar display grids (the type that display "88:88" when all segments are active) — are transparent. Thus, the LED light shining through the transparent digits creates the projected time display. Now here's the mystery: if I peer into the operating projector, the time display appears inverted, but not reversed. That is, if the time is 1:08, peering into the projector reveals 1:08, not 80:1. If the time is 12:03, peering into the projector reveals 15:03, not E0:51 (please use your imagination to make these digits out of straight line segments; a "1" has no base and no hook, but is just a straight line, an upside-down "2" looks like "5" and vice-versa, a reversed "3" looks like "E", and so on). I am probably overthinking this, but how is it that the time is projected correctly on the opposite wall when it is apparently flopped only in the vertical, not in the horizontal? —ScheinwerfermannT·C22:13, 25 March 2009 (UTC)[reply]
Oops, I was underthinking: when I look at the projection on the opposite wall, I'm horizontally flopping myself. If I were to hold up a translucent screen in front of the projector and look in the direction of the projector, then the digits would appear horizontally flopped. I'm pretty sure that solves the mystery, yes? —ScheinwerfermannT·C23:50, 25 March 2009 (UTC)[reply]
'Shock' metamorphism is described as impact metamorphism in our article, a section that is a lot less than comprehensive (there's also impactite but that's only a stub). Basically it refers to the effects of very high strain-rate events such as you would get during a meteorite impact or a large volcanic explosion. This causes characteristic effects in some minerals, such as deformation lamellae (microfractures along which local melting has sometimes occurred) in quartz and locally wholesale melting of the rock, forming suevite [18], or local high slip-rate faulting causing melting of the fault walls forming pseudotachylite.Mikenorton (talk) 08:57, 26 March 2009 (UTC)[reply]
I've heard data saying that the Earth was cooling, not warming, despite global warming. If the Earth is showing symptoms of global warming, why is the planet cooling?--24.4.54.96 (talk) 23:40, 25 March 2009 (UTC)[reply]
It depends on your time scale, of course. We are considerably cooler than say the Jurassic Period, so if you used those two data points, you could say we are cooling off... Remember, it's all in how you organize your data... But, if you want to look in the recent past, say the last few hundred years, we are warming some... --Jayron32.talk.contribs01:38, 26 March 2009 (UTC)[reply]
Perhaps you should read the Global cooling article? I think the Global Cooling hypotheses recently were popular in the 1970s and 1980s, and there have been improvements in understanding of the climate, as well as better computer modeling simulations. -- JSBillings02:04, 26 March 2009 (UTC)[reply]
If the earth is cooling - it's doing it on geological time-scales. Our behavior is warming it up on human time-scales. So, it's possible that what we'll happen is heat the planet up by 10 degrees over the next 150 years - and half a million years later, global cooling will erase that gain. But it's too far off to really affect the answer. Although the world was warmer still at some times in the dim and distant past - and it might be cooler again in the distant future - but our problem is with NOW - the next generation of humans. We can clearly see a trend - it's upwards - and the consequences are serious indeed. It's not rocket science. Follow along with these calculations:
According to Earth#Hydrosphere, our oceans contain 1.4x109km3 of water.
According to Coefficient of thermal expansion, water expands in volume at a little over 200 parts per million for every degree centigrade that the temperature rises.
So - when the temperature goes up an average of 1 degree centigrade across the globe, we gain 200x10-6x1.4x109 cubic kilometers of water. That's 280,000 cubic kilometers of water.... 280,000,000,000,000 cubic meters.
According to Earth, our oceans cover about 360,000,000,000,000 square meters of the earth's surface.
Which mean that all of those zeroes cancel out and our oceans get 280/360 = 0.78 meters deeper every time we warm up the planet by just one degree.
According to Effects of global warming - we've already seen a 20cm rise in global ocean levels since the 1920's from a third of a degree global temperature rise. This fits perfectly with the numbers I've just calculated.
Now - take a look at the graph to the right here. It shows the best estimates of temperature rise from the eight leading climatological institutes. They certainly disagree - but you've gotta admit we're going to see a degree or two of rise in our lifetimes - two to five degrees in our kid's lifetimes. Note that the graphs aren't levelling out - in most of them, the curve is getting steeper and steeper.
So we should expect to see several meters of ocean level rise. Because most decent farmland is in low-lying river basins - we'll find that at least 150 million people will lose their livelyhood as a result of a ONE meter sea level rise. We're certainly going to get a lot more than that.
But this is forgetting melting ice and all of that stuff. The melting of ice in Greenland alone is responsible for 260 cubic kilometers of water being dumped into the oceans every year...factoring that in - we're getting oceans that are going to be several meters deeper in the immediate future - and between 7 and 20 meters deeper in 100 years. Imagine yourself at your favorite seaside resort - now imagine the water at high tide being SEVENTY FEET deeper than it is right now. Do the same thing at any place with a big river flowing through it. London, NewYork, LA - completely gone.
Denying what's happening right under our noses has gone beyond mere healthy skepticism. We're getting into the realms of obstructing the survival of modern civilisation.
Did you just make that up about rivers being similarly affected? I would imagine that inland rivers would get lower as their snow & ice sources get smaller. --Sean12:33, 26 March 2009 (UTC)[reply]
Well, eventually...but I'm not talking about mountain streams here - I'm talking about the close-to-sea-level river deltas. These were ideal places to start major cities - and they are also big-time sources of agricultural land...and when the ocean levels rise - they vanish. SteveBaker (talk) 19:55, 26 March 2009 (UTC)[reply]
"London, NewYork, LA" don't really have "inland" rivers. I'm going to go out on a limb and say that the rivers in those cities are probably very much affected by sea level. APL (talk) 12:46, 26 March 2009 (UTC)[reply]
At the risk of sounding like a denialist, do those temperature scales from 1900 to present account for the urban heat island effect? In other words, areas with thermometers that were rural in 1900 may now be urban today, and would gain heat as a result. 65.121.141.34 (talk) 13:25, 26 March 2009 (UTC
I think those are average temperatures over the entire world. The urban heat island effect doesn't do much to average temperatures, just the ones in urban areas. --Tango (talk) 15:59, 26 March 2009 (UTC)[reply]
I honestly think the climatologists would have thought of that! If just one of those institutes was claiming this kind of rise and the others were not - then we could wonder whether they had made such a major boo-boo. But this goes well beyond that. They ALL pretty much agree - and they aren't measuring this with thermometers hung out of their office windows...we're talking ice-cores in the antarctic, tree rings, satellite thermal imagery...this is a pretty seriously researched topic. SteveBaker (talk) 19:55, 26 March 2009 (UTC)[reply]
One other note on the expansion of water part. The math is wrong in that it assumes that the oceans will warm evenly. In fact, only the top layer will warm significantly. At 10,000 ft deep the water will still be about freezing. 65.121.141.34 (talk) 13:27, 26 March 2009 (UTC)[reply]
True. Most of the rise in sea levels is from melting polar ice. I think the accuracy of Steve's figures is a coincidence! --Tango (talk) 15:59, 26 March 2009 (UTC)[reply]
I believe those predictions are made assuming we continue pumping out CO2 at ever increasing rates as we've been doing previously. If we do cut back on emissions, we can significantly reduce (but certainly not eliminate) the risks. So far, that isn't happening, though - until China starts taking steps to reign in its increasing emissions, there isn't a great deal the rest of the world can do (every little helps, of course). --Tango (talk) 15:59, 26 March 2009 (UTC)[reply]
It's not absolute amounts, it's increases/reductions. China is increasing its emissions at a rate that more than cancels out everyone else's reductions (I think - it's been a while since I examined the numbers). Also, China hasn't picked all the low hanging fruit that everyone else has done, so could make significant reductions if they tried (or, at least, significantly slow down their increases - they couldn't actually reduce without dramatically slowing their economic growth, which they won't do and it's a bit much for other countries to ask them to). --Tango (talk) 22:23, 26 March 2009 (UTC)[reply]
The fact is, if the US and Europe don't take the lead, nobody will. In any case, per person the US's CO2 production is an order of magnitude more than the Chinese. If the US isn't willing to cut back, why would China? In other areas of strategic importance (say, nuclear weapons stockpiles), when the US (which has a lot more) refuses to make reasonable and appropriate reductions, nobody else (like China, Russia, etc.) has ever felt the need to do it instead. When the US does make such reductions, it gives it moral and political leverage (and leverage with other nations, which can apply additional weight to it) when it makes requests of others. The "China isn't doing it, so why should we?" is a pretty silly argument—one that guarantees that no one will reduce if everyone follows it. --140.247.249.53 (talk) 22:03, 26 March 2009 (UTC)[reply]
I never said others shouldn't do their bit anyway, I just said without China doing something it's not going to help much. --Tango (talk) 22:23, 26 March 2009 (UTC)[reply]
The calculation about the ocean water expanding if the global temperature rose makes the unsupported assumption that the water would have a constant quantity (or mass). Higher surface temperature would mean more evaporation, putting more water in the atmosphere. On the other hand, melting ice (at least the ice on land) would increase the mass of water in the ocean, but would slightly lower its density by diluting the salt. How would global precipitation be affected, and how would underground aquifers be affected, as people pump the water table down lower and lower? We have also seen the water level in lakes drop dramatically due to lower rain and higher usage in some regions. How about biomass: desert versus jungle/forest/cropland, where some water is bound up in plants and soil. There are several factors which would increase and several which would decrease the mass of water in the ocean. 19:09, 26 March 2009 (UTC)
You're kidding right? You think that a 1 degree temperature rise will evaporate a quarter of a million cubic kilometers of water - and that won't have a drastic effect? Let me point out a little something...water vapor is a MUCH nastier greenhouse gas than CO2. If anything remotely close to that much water made it into the atmosphere - it would be approximately like living on the surface of venus! But it's silly - even at 100% humidity - there wouldn't be "room" in the atmosphere for a quarter of a million cubic kilometers of liquid-water-turned-into-vapor. SteveBaker (talk) 19:50, 26 March 2009 (UTC)[reply]
Venus to earth atmosphere analogy is next to worthless because we are not going to get anywhere near 96.5% CO2. I believe right now we are at 0.035% CO2 give or take. And at levels above 8% you have 10 minutes to live anyways so temperature would not matter much. Plus there is a little thing called condensation and cloud formation, more prevalent with higher degrees of water vapor which would reflect more sunlight (a cooling effect I believe) right? 65.121.141.34 (talk) 20:10, 26 March 2009 (UTC)[reply]
You seem to be misunderstanding the gravitomagnetic effect; the gravitomagnetic effect is a (small) effect of general relativity which is governed by equations very similar to Maxwell's for electromagnetism. The gravitomagnetic effect can't be quantised as an approximation to general relativity as it is a direct consequence of relativity. The similarity of gravitomagnetism to electromagnetism is like the similarity of Newton's law of universal gravitation to Coulomb's law, the two forces use similar equations but you can't infer more about one by using the other... - ZephyrisTalk09:09, 26 March 2009 (UTC)[reply]
You're talking about the gravitational analogue of magnetism (which is what I think of too when I hear the word "gravitomagnetism"), but our article gravitomagnetism appears to be about a weak-field approximation to GR that looks like Maxwell's equations. I don't know whether that specifically can be quantized, but weak-field gravity can be—see gr-qc/9512024. -- BenRG (talk) 12:56, 26 March 2009 (UTC)[reply]
Is human food killing the seagulls?
Is it true that the seagulls living in urban areas that feed on discarded human junk food are starting to drop dead from heart disease or develop diabetes? I was told this today by a taxi driver and I don't know whether he was winding me up or not. It sounds slightly plausible to me, considering that some of these gulls seem to exist on chips, pizza, burgers, fried chicken and kebabs. --84.66.64.241 (talk) 01:57, 26 March 2009 (UTC)[reply]
Birds, like mammals, have a pancreas that produces insulin and glucagon. I suppose that anything with pancreas may develop diabetes under certain environmental and/or genetic conditions; I can't see why not. OTOH, I've never seen avian diabetes studied or even mentioned. Feeding sugar or HFCS to a seagull is an exceedingly bad idea, at any rate. They don't normally put sugar on their fish or crab :) . Fried foods, as you can imagine, are also not a part of their natural diet. Heart problems stemming from overeating and lack of exercise are expected, too. Finally, plastic and foil wrappers are potentially a serious problem. AFAIR, seagulls can dispose of the inadvertently swallowed pieces of mollusc or crab shells; but a swallowed piece of a nylon bag may well prove fatal. --Dr Dima (talk) 06:53, 26 March 2009 (UTC)[reply]
As with a lot of human diseases, animals tend not to suffer from them because they are so short-lived. It takes years of a terrible diet to develop these conditions - and seagulls simply don't live that long. SteveBaker (talk) 19:44, 26 March 2009 (UTC)[reply]
FWIW, the larger gull species tend to be up there amongst the most long-lived of birds. 25-plus-y.o. Herring/Lesser BB Gulls are not uncommon, as I understand it. They don't even start breeding until they're at least four. Here's a couple of slightly-related links I just found (see here and here) - they doesn't specifically answer the original question but seem to suggest that a diet high in fat and sugar is indeed having an effect of some kind on the gulls. --Kurt Shaped Box (talk) 22:17, 26 March 2009 (UTC)[reply]
Adverse drug reaction: Rabeprazole
Is their any evedience that long term use of rabeprazole like Proton pump inhibitor is associated with incease risk of gasric carcinoma or gynecomastia??? —Preceding unsigned comment added by Samir doc (talk • contribs) 08:35, 26 March 2009 (UTC)[reply]
I took this photo last summer of small (~10cm long) fish trapped in a rockpool on Holy Island in North Wales. Does anyone have any idea which species they are? - ZephyrisTalk08:58, 26 March 2009 (UTC)[reply]
It seems that lightning and other arcs are shown, sometimes unexpectedly, to produce electromagnetic radiation in virtually every part of the spectrum where detection attempts have been made: Radio and microwave [20], infrared [21], visible (hence visibility of lightning and sparks), ultraviolet [22], X-rays [23], and even gamma rays [24]. So why not terahertz? Since commonly discussed THz sources, even incoherent ones, are extremely expensive and high-tech it seems like something as obscenely low-tech and low-cost as source of high voltage electric arcs deserves some attention. Wouldn't it be easy to try shooting high voltage arcs through random gases at random pressures and observing in the THz region of the spectrum, just to see what happens? Wouldn't a THz arc-lamp/discharge-lamp be far cheaper than other sources?
I'm no expert - but isn't the problem to get enough power into those THz ranges to be useful? What you do by producing (essentially) Radio-spectrum white noise is to put power into the spectrum in roughly the inverse of the frequency (or maybe the inverse of the square of the frequency...I forget). At any rate, that means you've got to put an insane amount of energy into your arc to get enough THz stuff to be useful. Lightning can do it because it discharges an ungodly amount of energy in a very short space of time...you can't sustain that kind of power for very long. SteveBaker (talk) 19:42, 26 March 2009 (UTC)[reply]
If that were so then lightning and other arcs wouldn't be effective in radiating visible light. I emphasize that as far as I know there is no part of the electromagnetic spectrum that arcs and lightning are terribly bad or inefficient at radiating in, and it would be very strange if unlike all other parts of the spectrum one got so little in the THz region for a reasonable input power.
I think you're missing what I think is at least part of Steve's point: if they are indeed radiating in all parts of the spectrum, they can't also be highly efficient in radiating in an any/every arbitrarily-chosen narrow range. With a fixed amount of energy, you can either radiate all of it at one frequency or spread it out thinly. So if you have a huge amount of energy over a broad spectrum, you get a decent amount in your band of interest, but that's not efficient because so much of the energy is in other bands. DMacks (talk) 20:18, 26 March 2009 (UTC)[reply]
This has gone slightly in the wrong direction. The distrubtion of energy with respect to frequency is important, as nothing will emit radiation equally in all frequencies - the result would be infinite power radiation. That's why the notion of lightning radiating in "all other parts of the spectrum" is inherently flawed. This isn't even like blackbody radiation with a smooth curve on the power vs frequency distribution graph - the distribution of lightning's radiation is going to have peaks and valleys, corresponding to the different mechanisms that produce that radiation during the strike. For example, the visible light just under the 1,000 THz range is due to photons with an energy on the order of a few electron-volts, being generated by molecular-level reactions from the oxygen and nitrogen in the atmosphere being strongly ionized by the strike. This does not neccessarily imply that THz radiation will also be emitted strongly. There just happen to be various peaks associated with their respective generation criteria: just under 1,000 THz (or PHz) radiation, i.e. visible light, corresponds to electrons hopping around in orbits (flames, sparks, neon signs, etc) as well as blackbody radiation around a couple thousand kelvins (incandescent lightbulbs) - Ultraviolet, at a few PHz, typically comes from higher energy electron hopping (black light phosphors) and blackbody radiation of around 9000 kelvins (electric arcs) - X-rays up in the hundreds to thousands of PHz (10e5 to 10e6 THz or 10e18 Hz) typically come from high-energy electrons knocking into heavy atoms, either knocking out inner valence electrons (causing outer electrons to undergo a huge drop to fill the hole) or Bremsstrahlung from nearly hitting the nucleus - Gamma rays up in the 10e20 Hz range typically come from state changes of million of electron-volts, typically found in nuclear reactions - Infrared in the ten to hundred THz range is abundant, with the power decreasing with temperature, from simple blackbody radiation at various sane temperatures (like human body heat, a low power emitter of 30 THz radiation) - lower frequencies go from microwaves generated by ballistic electron motion within a small but macroscopic cavity, all the way down to radio waves that are easily generated with discrete electronics equipment. At around 10-20 kelvins, you can generate blackbody radiation with a peak in the THz range (interstellar dust does exactly this), but the power of this radiation is too low to be useful for anything. It's just a fact of life that there aren't any common mechanisms in nature that generate photons with the right wavlength (around a millimeter). That's why THz radiation is hard to generate. DeFaultRyan23:09, 26 March 2009 (UTC)[reply]
A quantum mechanical "proof" that any positive real number is zero
About a week ago, while browsing Wikipedia, I stumbled onto a (fallacious) proof that any positive real number is zero. It was quantum mechanical, basically "proved" that the Planck constant equals zero. The resolution had something to do with bra-ket notation not working on a sphere or hiding a functional analysis fact from the plain sight. It ended in words like: "Thus , an arbitrary positive real number, must be zero." The exact wording must have been different, as googling doesn't help. I really cannot remember anything else. Could anyone please point me to the Wiki article?—Pt(T)22:59, 26 March 2009 (UTC)[reply]
Please do your own homework.
most libationious of ways, maybe russians or something more viscous next. ;-) -hydnjo (talk) 02:38, 23 March 2009 (UTC)
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