Wikipedia:Reference desk/Archives/Science/2007 April 16

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[edit] April 16

[edit] Total number of people

What is the total number of people to have ever lived and how many people die and are born each year? 71.100.175.14 04:01, 16 April 2007 (UTC)

I don't know off the top of my head, but I just typed "total number of people to have ever lived" into Google, and the first lotsa hits look relevant... —Steve Summit (talk) 04:03, 16 April 2007 (UTC)
The first question has been asked several times recently. Estimates vary of course, but somewhere in the region of 100 billion, as I recall. Clarityfiend 04:31, 16 April 2007 (UTC)
No need to recall or guess. It's all here, in our very own Wikipedia. JackofOz 04:45, 16 April 2007 (UTC)


See
Wikipedia reference desk Science Archive September 2006
How many humans have ever lived.
http://en.wikipedia.org/wiki/Wikipedia:Reference_desk_archive/Science/2006_September_27

202.168.50.40 05:15, 16 April 2007 (UTC)

Reason for asking:

From the above and according to Ramsey at the Department of Mathematics at the University of Hawaii so long as the total number of people that have ever lived (have been born) is less than 781,250,000,000 only Seven Degrees of Separation are required to link every single human who ever lived assuming that each person still knows at least 50 other people. Drop that number to 5 contacts and the Degrees of Separation only jumps to 16. 71.100.175.14 06:51, 16 April 2007 (UTC)

There must be additional assumptions. I believe that figure would only be true if those fifty people are essentially distributed at random around the world. Take an extreme case: an isolated island with 51 people, where everyone knows everyone else, but has never met anyone not from the island. Each one of those islanders knows fifty people, yet you could trace through as many degrees as you would like and they would never be connected to you, for instance. In reality, contacts tend to be clustered around geographic connections (and to a lesser extent, cultural, professional, and so on). — Knowledge Seeker দ 08:52, 16 April 2007 (UTC)
Aren't you forgetting something? Those people had to have come from somewhere and it is the link with the people from which they came that links them to everyone else when you include previous living persons. 71.100.175.14 22:01, 16 April 2007 (UTC)
Of course, that's a gross oversimplification; the seven degrees of separation calculation is not – I'm sure – meant to be taken literally. If we take the maximum human lifetime to be of the order of 120 years, with seven degrees of separation there's no way to be linked to anyone from more than 840 years ago.... TenOfAllTrades(talk) 12:55, 16 April 2007 (UTC)
Did you actually do the math? The estimated total number of humans ever born going back a million years based on only an average 25 year life span falls well within Seven Degrees of Separation with 50 contacts per degree. 71.100.175.14 21:42, 16 April 2007 (UTC)
Er, how do you have a contact with someone who died before you were born? TenOfAllTrades(talk) 22:18, 16 April 2007 (UTC)
By simply specifying that your application of DoS is not limited to the living but also included the dead just as you can specify that you have a hereditary relationship with your great, great, great, great, great grandmother who I am assuming is no longer living. 71.100.175.14 22:43, 16 April 2007 (UTC)
By that token, any living creature can be connected to any other living creature with only two degrees of separation, via the universal common ancestor... SamSim 19:52, 19 April 2007 (UTC)

The total number of people who have ever existed is probably between 70000000000 and 100000000000. There are estimated to be around 4 deaths and 6 births each second, whch is about 125000000 and 190000000 each year. But of course these are all estimates, especially since people disagree on how long humans have existed for.

[edit] Do certain squirrel species commit suicide? (or for that reason any species, other than the human species?

I am researching on the subject of suicide. Currently wondering if there are other species (alive or extinct) that are capable of committing suicide. I've searched google, but instead landed up in blogs that describe how squirrels cross the road and get killed...or something like that. Are animals or insects as such capable of bringing an end to their own life?Arun T Jayapal 09:32, 16 April 2007 (UTC)

I don't know of any animals besides humans who commit suicide for the pure sake of ending their lives, but bees die when they sting something (sacrifice themselves to scare away what might threaten the hive), deer stare stupidly at headlights and get run over instead of stepping aside (what is that, fear? Confusion? I'm not sure actually). And, of course, there are always wonderful, cute, tiny, suicidal lemmings (mythically suicidal at least, they don't actually mean to kill themselves). But squirrels? I'm willing to be they're just dumb. I say don't worry if you run one over, do your part to help natural selection ;-) Someguy1221 10:07, 16 April 2007 (UTC)
I believe deer are exhibiting an inappropriate survival response to "freeze" so the "predator" (car) won't see them. Nothing in their evolution prepared them for dealing with cars, so they react to them like they would to a predator they know they can't outrun. If that was actually the case, freezing and hoping the predator doesn't detect them would indeed be their best chance at survival. StuRat 14:48, 16 April 2007 (UTC)
Possibly related to this is Learned helplessness, which shows that at least animals can learn some sense of futility. The basic experiment taught dogs (through conditioning) that the sound of a bell would be followed by an electric shock. Dogs that had a means of escape from the start would quickly learn to use it when the signal was given. Dogs that did not have this possibility of escape during learning would not not use it when it was introduced later on. In this way an animal could at least commit suicide through inaction, rather than action. A lot of behavior surrounding learned helplessness seems to correlate to human concepts like clinical depression and optimism, which suggests that animals can at least suffer suicidal emotions, even if they are unaware that death might stop the pain. risk 22:25, 16 April 2007 (UTC)
It's the same with hedgehogs and cars. They roll into a ball for protection when they see the headlights - which is not much use vs. a wheel. I think it's the same with armadillos - maybe one of the Americans here can confirm that they are regular roadkill victims (I think I read that). --Kurt Shaped Box 22:30, 16 April 2007 (UTC)
Hmm. Why do bees die after they sting?Arun T Jayapal 13:06, 16 April 2007 (UTC)
Bees die after they sting because the stinger is barbed in order to remain lodged in the skin of the victim when the bee flys away, and when the stinger pulls out, the venom glands come with it in order to continue pumping venom into the victim. This removal of the stinger / venom gland results in a mortal wound for the individual bee. This is a classic case of Altruism in the evolutionary sense. -Czmtzc 14:02, 16 April 2007 (UTC)
That definetly qualifies as a suicide.

—The preceding unsigned comment was added by 84.187.59.188 (talk) 23:08, 16 April 2007 (UTC).

If you mean do healthy animals commit suicide, I think the answer is no. But this would depend on if they knew their actions would result in death. Do animals have a sence of life and understand that they may die at some point - and if they do, do they click that they could end their own life sooner? But there are cases where sick animals will do things that cause them to die faster, like an indured whale beaching itself for exapmple. I think that somewhere along the line its happened, but don't know if you'll find much info on it. Think outside the box 11:29, 16 April 2007 (UTC)

My dog acctually commited suicide after its pups were born. we paid more attention to the puppys (but still kept spoiling him) but he wanted all the attention so one day he just looked at us then ran straight into the tires of a incomming car. now before you say anything this dog was smart he knew what cars did and he would never go near the road for this reason. this is why i belive that he committed suicide that day its the only explanation for his actions =( User:Maverick423 If It Looks Good Nuke It 13:50, 16 April 2007 (UTC)

I wonder if dogs ever suffer from post-partum depression ? StuRat 14:54, 16 April 2007 (UTC)

As for suicidal animals, there are many species that die after they have "served their purpose" (usually mating for males and giving birth/laying eggs for females), however, this is typically accomplished by some biological mechanism (not well understood) other than intentional suicide. Knowing whether you are a net help or hindrance to your relatives is complicated, so requires a fair amount of intelligence to determine. This may be why the decision of when or if to commit suicide isn't left up to less intelligent animals. I can think of one possible exception. I believe in many species a sick individual will leave the group and "go off to die". This death will then take place due to predation, starvation, dehydration, exposure, etc. StuRat 15:02, 16 April 2007 (UTC)

You know i acctually seen that in many documentrys of animals. when a preditor can nolonger hunt with its pack, it ussally goes off to die like StuRat said, i belive one of the documentries acctually stated that this is equivallent to committing suicide in the animal kingdom as the animal that leaves knows it has no chance or surviving on its own with out its pack. Perhaps a articl on Animal Suicide is in order? User:Maverick423 If It Looks Good Nuke It 15:28, 16 April 2007 (UTC)

male angler fish.

Don't the rest of the pack actively drive the 'no longer useful' animal away, instead of it choosing to leave of its own accord? I've certainly read anecdotal accounts of this amongst gulls (if one bird is sick or injured, the rest will attack it until it either leaves or is killed) - the sickly flock member presumably being a liability to the rest. Apparently, albino gulls are subject to a lot of 'social pressure' too (this was actually cited in a scientific paper I read, though I cannot recall the details now)... --Kurt Shaped Box 22:25, 16 April 2007 (UTC)
I'd like to see that cite. I don't doubt you, but it sounds counter-intuitive to me. Part of the benefit of living in a herd/ flock/ school is that you reduce your individual risk of predation because there are so many others around. If I was an antelope in the Serengeti, I'd be quite in favour of there being a few lame animals in the herd for when the cats start hunting; if there are easier targets sround, I might be left alone. Matt Deres 20:32, 17 April 2007 (UTC)
In some cases female Black Widow spiders and Praying Mantis' devour the male after copulating. I guess you could say that the male commits suicide by doing that. SteveBaker 23:08, 16 April 2007 (UTC)
Infected ants sometimes leave the colony and subsequently die.Polypipe Wrangler 06:22, 17 April 2007 (UTC)

[edit] Quantifying article

In article Center pivot irrigation there are no factual data given. Does someone know some data that quantify such an irrigation system? E.g. typical, average, even record length of array (yards or meters). Speed of rotation. Quantity of water pumped. Etc. etc. VanBurenen 14:27, 16 April 2007 (UTC)

[edit] A tree named Sag

According to our article about Purandhar as well as this page, "Some parts of Purandhar are covered with forest, which is composed mostly of Sag, Teak, Oak, and Mango trees." I've never heard of a type of tree called "Sag", however. Nor does Wikipedia have an article on such a type of tree. The closest I could find was Amaranthus dubius, a weed which is sometimes referred to as "Khada sag". Anyone have any clues as to what this "Sag" is referring to? Kaldari 16:36, 16 April 2007 (UTC)

Looks like it may just be another name for Teak actually. Kaldari 16:43, 16 April 2007 (UTC)
Maybe a misprint of Sal?—eric 17:31, 16 April 2007 (UTC)

[edit] Emphysema death breakdown

What is the breakdown of emphysema death causes? [Mαc Δαvιs] ❖ 16:54, 16 April 2007 (UTC)

By far the leading cause of emphysema is cigarette smoking [1]. Air pollution and occupational exposure to airborne toxins round out the bulk of the remaining cases. About 2% of cases a attributable to A1AD, a genetic disorder. Have you Googled for numbers? TenOfAllTrades(talk) 02:51, 17 April 2007 (UTC)

[edit] I don't know jack about the beanstalk

Would the cable of the space elevator rise perfectly vertically or would it bend? If the latter, roughly how much? Clarityfiend 16:57, 16 April 2007 (UTC)

Speaking generally and ideally, the cable remains taut and vertical. From a practical engineering standpoint, a completely rigid structure is a bad idea and so some flex would certainly be allowed for and expected. Also note the article subsection on cable lean. — Lomn 17:28, 16 April 2007 (UTC)
If anchored at the equator, An ideal beanstalk will be vertical. If not anchored at the equator, it will not, but I'm not sure what will happen instead. -Arch dude 20:40, 16 April 2007 (UTC)
Yet another reason it hasn't been built yet : ) Nimur 20:43, 16 April 2007 (UTC)
I believe that one of the reasons why ship-born earth-side designs are looking good because it would be possible for the ship to move out of the way of major storm systems to avoid damage to the cable. It seems unlikely that the space-side end would be able to keep up - so I deduce that the cable is indeed allowed to lean somewhat. But since the cable would be considerably more than 35,000km long, the base would have to move an awful long way before there was any significant angular shift in the cable! You have to have a mental image of a cable that's three or four times the diameter of the earth! From that, perspective, a bend of a few kilometers - or even maybe a hundred kilometers is pretty negligable when distributed along the entire length. The tricky matter is whether very low frequency oscillations might be induced by wind shifts happening at close to the cables resonant frequency. Our article suggests that a one-degree lean might occur due to the coriolis effect on the 'climber' as it ascends the cable. SteveBaker 23:00, 16 April 2007 (UTC)

[edit] Viruses

I am writing a paper on viruse, and am a little confused!! Can viruses be destroyed by phagocytosis, or does this only apply to bacteria? Hope someone can help 81.101.49.156 19:40, 16 April 2007 (UTC) Chrissy

Virtually any foreign matter can be consumed by phagocytes, viruses included. And like bacteria, viruses can be attacked by free roaming antibodies. Viruses can also be eliminated by the additional method of Natural killer cells destroying infected cells, to prevent new viruses from forming from it. Someguy1221 21:00, 16 April 2007 (UTC)

Thankyou for clearing that up for me 'someguy', much appreciated 81.101.49.156 22:16, 16 April 2007 (UTC)Chrissy

[edit] Hydroponics and Tequila

I've been reading up on hydroponics, and I recall an episode of the Colbert Report where a guest (I think it was Neil Young) proudly declared to have smoked pot that was hydroponically grown in tequila. The more I read about hydroponics, the more this strikes me as impossible. As I understand it the nutrient solution for hydroponics needs to be carefully controlled in terms of acidity and mineral concentration, and chucking spirits in there seems like a sure fire way to kill the roots. Is this at all possible? And if it is, does it have any effect on the crops? I somehow doubt that this will lead to tequila flavoured strawberries, even if it does work. risk 22:11, 16 April 2007 (UTC)

Maybe he actually meant hydroponically grown in Tequila? Vespine 22:35, 16 April 2007 (UTC)

Or, I suppose, you could add one drop of the alcoholic drink of your choice to each gallon of water, which shouldn't kill the plants, but this certainly wouldn't affect the flavor of the plants which grow in it, either. StuRat 22:50, 16 April 2007 (UTC)

Or maybe he was joking? It would not be unexpected to hear a comidic exageration the Cobert Report. -Czmtzc 11:50, 17 April 2007 (UTC)
I don't think that was the case, but I may have missed it. In any case, it turns out that it was Toby Keith [2] and it was Willie Nelson's pot. Apparently Nelson got busted a week later, too. risk 12:51, 17 April 2007 (UTC)

[edit] What's the age record for herring gulls?

Today, I encountered a gull that must be at least 25 years old now. I remember first seeing him as an adult when I was a boy - he has *very* distinctive plumage (looks like he has some sort of pigment disorder - large areas of his wing plumage are snow white, instead of grey, in a very distinctive pattern). I hadn't seen him for three years or so (he used to nest around here regularly), so I just assumed that he was dead and gone - but today, I saw him sat up there on his favourite perch (well, rooftop), watching the world go by. I'm certain that it's the same bird. Has anyone ever heard of an older member of this species? --Kurt Shaped Box 22:44, 16 April 2007 (UTC)

Now how did I know who asked this question as soon as I saw the title ? Isn't it possible that the pigment disorder is inherited and it's offspring has also inherited it's favorite perch ? StuRat 22:53, 16 April 2007 (UTC)
It's certainly possible Stu - it did appear that it was the same bird though. The particular pattern of white and grey on his wings was exactly as I remembered it. What are the chances of a pigment disorder manifesting itself identically, even if it is inherited? --Kurt Shaped Box 23:04, 16 April 2007 (UTC)
There could be some selective memory at work, your memories of that bird from 25 years ago may have been adjusted to match the current bird. Do you have any photos of the earlier bird to ensure that you recall it correctly ? StuRat 00:46, 17 April 2007 (UTC)
First, I will assume good faith, and that your memory is not faulty. According to this site Top ten bird lifespans of North America, the age records for the top ten range from 30 - 50 years. The birds in the list are all sea birds too. I personally do not think it is unreasonable that you may have a 26 year old bird. -Czmtzc 11:48, 17 April 2007 (UTC)
Thanks for that guys. I'm willing to accept that it may be selective memory on my part - but it would be nice to think that the big guy was still alive and kicking. I have fond memories of throwing food into the air for him to catch from back when I was a kid. Because he looked slightly different to the rest, I singled him out and made sure that I always threw food in his direction. That's all it takes to make a gull start hanging around near your house (for those that might want a gull hanging around near their house). --Kurt Shaped Box 18:45, 17 April 2007 (UTC)
Just in case you want them to "decorate" your car for you ? StuRat 07:03, 19 April 2007 (UTC)

[edit] Eris

From looking at Eris and the Definition of 'planet', how is Eris not a planet? Teak the Kiwi 23:21, 16 April 2007 (UTC)

The definition of planet is somewhat subjective; the IAU has sought to quantify it as follows:
See 2006 definition of planet for some details. In my opinion, these are vague enough to allow astronomers some argument-room. Nimur 00:09, 17 April 2007 (UTC)
I still don't understand, it looks close to a sphere, it is in orbit a round the sun, and from what I can figure out it has 'cleared it nieghborhood' (Its not like Ploto and Charon). If it is higher mathematics than Algebra I, just say so. Teak the Kiwi 03:07, 17 April 2007 (UTC)
Eris is classified as a dwarf planet - the difference between that definition and that of a true planet is thr third one (above) "cleared the neighborhood". Since Eris has been classified as a dwarf, it must be that it has not cleared it's neighbourhood. SteveBaker 03:43, 17 April 2007 (UTC)
That is indeed the case. It is clearly demonstrated at List of solar system objects by planetary discriminant. The discriminant is used as the measure of clearance. The lowest discriminant for the now-accepted planets is 24,000 (Neptune), whereas that for the minor planets is no higher than 0.33 (Ceres). Eris's discriminant is only 0.10. By this measure, Eris is nowhere near clearing its neighbourhood. JackofOz 03:59, 17 April 2007 (UTC)
The definition is horrible. It was an attempt to avoid having very many new planets and at the same time include no completely arbitrary size restriction. The whole story is an example of the Paradox of the heap, where an essentially fuzzy definition (being large) is made precise. Do you remember the old sience fiction stories about mirror earth? The existence of such an object (there is none, I know, thank you) would make earth a dwarf planet under this definition. A raindrop floating around in free space is a dwarf planet by this definition. It is really unspeakably horrible. —The preceding unsigned comment was added by 84.187.17.11 (talk) 13:06, 17 April 2007 (UTC).
I disagree. A raindrop floating in free space (part of it would vaporize and the rest would solidify pretty quickly, so it would rather be a hailstone) isn't round because of gravity but because of surface tension, therefore it wouldn't be a planet according to the definition. And with a mirror Earth Earth's orbit wouldn't be stable, and I would consider such a planetary system to be still in development - I think the chances are quite high that the two bodies collide within a few million years. Icek 17:31, 17 April 2007 (UTC)
Yeah - there is no way a raindrop can qualify because it can't hold a spherical shape under it's own gravity, it would be completely unable to clear it's neighbourhood. Sure - they become spherical due to surface tension - but that doesn't make them planets. The "spherical under own gravity" requirement effectively puts a minimum size on what qualifies as a planet - so there is an implied lower size limit. But this is all irrelevent in the grand scheme of things - labels like 'planet' are arbitary - there are bound to be corner cases that cause difficulties. We get this kind of issue come up here every day or two on the science desk and the answer is - in truth - "This has nothing whatever to do with science - it's a branch of linguistics." SteveBaker 00:46, 18 April 2007 (UTC)