Wikipedia:Reference desk/Archives/Science/2009 April 21

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April 21[edit]

Bacteria passed on at birth: what about cloning?[edit]

I guess this question is equally valid for many species probably to be cloned in the near future, but it most directly concerns the Spanish Ibex previously "cloned" into a goat, and the Woolly Mammoth. I'm aware that the human body is host to a great deal more bacteria than there are cells in our body, and without most of those we wouldn't be able to survive, we may not even be able to call ourselves "human". Now I assume a lot of these are transmitted through the atmosphere, or possibly what we consume, but I can only assume that a lot of the more essential bacteria are passed on through the mother in the early stages of growth. When human cloning is concerned I don't see a problem as long as there is a surrogate mother, but with the Ibex and the Mammoth supposedly best cloned into some sort of a goat and an elephant, doesn't that cause major problems? I'm assuming that cultured bacteria are very different between species, but is that too much of an assumption? Also, even if it is possible in the future to clone and nurture to size an animal without some sort of surrogate, will the fact that they don't have access to native bacteria cause problems? Thanks! (talk) 01:54, 21 April 2009 (UTC)

Or, alternatively, could it be so easy as to manually insert the speficic bacteria into the growing fetus? (talk) 01:55, 21 April 2009 (UTC)
I seriously doubt that's a problem. For one thing, I believe your assumption that bacteria pass from mother to baby while the baby is still a fetus is incorrect. Most bacteria probabily colonise the baby after s/he's born. Besides the bacteria are different from person to person and that doesn't cause a problem, so I don't see how that's a problem. Dauto (talk) 02:44, 21 April 2009 (UTC)
I see. I guess I was under the mistaken assumption that there were bacteria essential (to the human digestive system), but apparently that's not the case, and we can live in sterile environments. (Now that I think of it, actually... that's pretty obvious!) According to gut flora though, some bacteria probably do pass from the mother to the baby during birth, but they are all incidental, and they will colonise the baby within the next few years anyway. Alright, thanks for the quick answer! (talk) 03:05, 21 April 2009 (UTC)
See also fecal bacteriotherapy. --Arcadian (talk) 05:41, 21 April 2009 (UTC)
I think bacteria in the gut are essential to the human digestive system (if you take lots of antibiotics you can get horrible stomach cramps due to the bacteria being killed off), but newborn babies only digest milk and aren't capable of digesting anything else - perhaps bacteria aren't required for digesting milk. There is plenty of time for bacteria to colonise the baby before they start eating solid food. --Tango (talk) 13:04, 21 April 2009 (UTC)

Columbus's New World "nightingale"[edit]

Christopher Columbus thought he heard the song of a nightingale not long after he landed in the Americas, where there are no nightingales. What kind of bird might he have mistaken for one? (talk) 02:05, 21 April 2009 (UTC)

maybe the long-bellied swallow —Preceding unsigned comment added by (talk) 03:06, 21 April 2009 (UTC)

Possibly Catharus sp., not sure. In fact, I am not even sure the story is true. The version I know is Columbus saying "the only thing missing is a nightingale song", meaning he's confident the land is close. The two stories are not necessarily contradictory, though. Sorry. I wish I could help more. All the best, --Dr Dima (talk) 04:45, 21 April 2009 (UTC)

Gut flora[edit]

My wife and I were having a conversation today about gut flora, so I decided to read the article here. One bit in particular confused me a bit and I'd appreciate an explanation if you could...

The article states:

Immediately after vaginal delivery, babies have bacterial strains in the upper gastrointestinal tract derived from the mothers’ feces.

Since I don't have any kids, I'm a little unclear on how bacteria from the mother's feces could get into the baby. I thought that expectant mothers were given a laxative to flush the bowels so that they don't eliminate during the birth. I also thought that the vaginal area in general, including the anus, would be cleaned before delivery. So, could someone clear up my confusion? (I realize that birthing procedures are different around the world due to varying sanitary conditions and such but I'm guessing that the reference (which I can't read from where I am) for this sentence deals with babies born in modern hospitals.) Thanks, Dismas|(talk) 05:31, 21 April 2009 (UTC)

And having just read up from my question, I didn't realize that we had another, though different, gut flora question here today. Dismas|(talk) 05:33, 21 April 2009 (UTC)
Don't look at me! You're the one talking about gut flora with your wife *cough* But yeah, I agree. That statement confused me as well! (talk) 06:29, 21 April 2009 (UTC)
It was in relation to our new puppy and his diarrhea. When you have as many animals as we do, you get into some interesting conversations.  :-P Dismas|(talk) 08:42, 21 April 2009 (UTC)
I think that there will be some (probably very few) faecel bacteria in the birth canal. I remember hearing that children born by caesarean have a higher occurence of allergies which is possibly associated with the lack of bacteria during delivery. Smartse (talk) 12:49, 21 April 2009 (UTC)
I Agree with Smartse, Because birth canal has normal micro flora, that will not be easily washed out, except by use of board spectrum antibiotics, and yes there is a correlation of increased asthma prevalence and c-section you can see that here Asthma, and other studies correlated micro flora with decreasing risk of allergies here --Maen. K. A. (talk) 18:02, 21 April 2009 (UTC)
Actually, there are three parts to this: the existance of the gut bacterias, the transferring into the baby and the cleaning away of them that you describe. Naturally, some gut bacteria is present on the skin of the mother. There are so many zillion bacteria, that getting every single one off after a normal visit to the toilet is impossible with just wiping. These are in or close enough to the birth canal to be transferred to the baby either directly when the face passes or inderectly via hands, towels etc. In "modern" hospitals you say, mothers are cleaned. As a matter of fact, with the knowledge that bacteria is indeed most often healthy in these circumstances, Swedish hospitals have stopped sterilizing the mother with alcohol ahead of delivery. If some feces are pressed out during delivery (laxative is optional), it is simply wiped off. For the same reason, the baby is not cleaned after delivery, but just wiped off to keep the natural fat, bacteria and mucus on the skin - and nipples should not be sterilized either. -Mummy —Preceding unsigned comment added by (talk) 12:11, 22 April 2009 (UTC)

diatom isolation[edit]

hello there can anyone lend me a loophole proof protocol for isolation of diatoms from a mixed sample of phytoplanktons please —Preceding unsigned comment added by (talk) 06:32, 21 April 2009 (UTC)


respected Sir what is a base helix angle on a gear drawing

Regards chin —Preceding unsigned comment added by (talk) 10:13, 21 April 2009 (UTC)

I think it is zero for Spur gear and it could be anything less than 90 degrees for helical gears, although for practical purposes it is never even close to 90 degrees. It is the angle which the helix of the gear makes with the plane perpendicular to the longitudinal axis of the gear. Correct me if I am wrong. - DSachan (talk) 19:04, 21 April 2009 (UTC)

DIN & VDI[edit]

Hi is there is any differences in between DIN & VDI stndard class or it is same class. —Preceding unsigned comment added by (talk) 10:36, 21 April 2009 (UTC)

A quick Google check says that these are German standards. You'd probably have to be lucky to find anybody here who knows about them. Looie496 (talk) 21:09, 21 April 2009 (UTC)
There are heaps of DIN standards in many fields, can you be more specific as to your interest? As to VDI do you mean Verein Deutscher Ingenieure? Graeme Bartlett (talk) 21:39, 21 April 2009 (UTC)

Ethernet 1000BASE-SX physical limitations[edit]

What factors impose the ~550 m limit on the length of a 1000BASE-SX link? Is it modal dispersion, attenuation? What is the influence of chromatic dispersion in this kind of transmission? What is the bandwidth of a 1000BASE-SX signal? What are the alternatives? I've already read the Gigabit Ethernet article. Thanks in advance for your answers. (talk) 11:07, 21 April 2009 (UTC)

Normally the range is limited by modal dispersion in multimode fibre. The range can be down to as low as 300m. Different paths of light in the fibre results in a bit being smeared out in time, and running over following bits. You can get increased range by using OM3 fibre rather than OM2. Or you slow down to 100meg and get 2km range. If you go single mode, by using single mode laser GBICs and single mode fibre, you can get much longer range, 10 km at 1310nm or further at 1550nm wavelengths. Graeme Bartlett (talk) 21:21, 21 April 2009 (UTC)
The encoding uses 8b/10b encoding which expands data rate to 1250 Mbps. The Nyquist theorem says that the minum bandwidth is half this. Just imagine a 1 and a 0 in a square wave making up one cycle of a wave. So that is 625MHz bandwidth. In practice it is a square wave and there will be odd harmonics as well. Graeme Bartlett (talk) 03:24, 22 April 2009 (UTC)

solvent information missing from free radical addition[edit]

Which makes it a bit more difficult to cram for my orgo final ... I'm trying to keep track on when you would have to use aqueous solvents and what polar aprotic solvents to use, especially when you're using hydrogen halide gases. Would methylene chloride be suitable here? But you're adding peroxide, which I imagine may want aqueous solution, or would methylene chloride be suitable for distributing the peroxide too?

Also, why are the reaction articles so poor on solvent information? John Riemann Soong (talk) 14:10, 21 April 2009 (UTC)

You are using Wikipedia articles to cram for your final exam? Man, you are in real trouble. A suggested order of preference for cramming for a course is a) your own notes b) the notes of someone else in your class c) the notes of anyone who has ever taken the course d) your textbook e) someone else's textbook f) any textbook on the same subject g) online lecture notes on the same subject h) Wikipedia i) X-men comics. DJ Clayworth (talk) 14:22, 21 April 2009 (UTC)
Protic solvent talks about some reaction solvent effects. It would be great if someone added info about solvent effects to the major orgoI/II-level reaction pages themselves. But here's the key: if you actually know a reaction mechanism (and there are only really like a half-dozen of them in all of organic chemistry!), it's easy to figure out what types of solvents are good or bad and you don't have to memorize these last-minute really is easier to learn along the way! I'm with DJC here...if you're cramming, getting a broader perspective, learning about related ideas, etc are totally not what you're looking for, You just need to get 70% (I assume) of the the bare minimum info required for this specific exam. You don't care about anything except what is exactly part of the course as taught, so anything other than "stuff that is part of the course" (textbooks, notes, etc.) is only going to have the info you do want scattered among stuff you don't, and might not have the minute details or some special case that your prof has chosen as important for your course. DMacks (talk) 15:02, 21 April 2009 (UTC)

DNA sequencing[edit]

Hi all I am having trouble trying to understand the process of DNA sequencing. I've read the article on DNA sequencing but I am still a little confused so I hope that someone can help explain a few things to me. I understand that at the beginning there is a single strand of DNA and a primer joins on. The primer tells DNA polymerase where to begin transcription. The growth of the chain which begins with the primer is halted due to a dideoxynucleotide being incorporated into the sequence. Thats about all I do understand. Is there just one strand of single stranded DNA or lots of little single strands at the start? How does using radioactive or fluorescent nucleotides result in being able to tell the sequence of bases? If someone could give a brief explain DNA sequencing or tell me about any websites which may be of use that would be great. Thanks. —Preceding unsigned comment added by (talk) 15:06, 21 April 2009 (UTC)

There are numerous primers and single strands in the mix at the beginning of the reaction. It proceeds essentially like PCR. Due to the presence of the terminating nucleotide, every conceivable length of polynucleotide based on size will be produced in the reaction. Because there are different color fluorescence probes for each nucleotide, an analyzer can read the bands on a gel. Each band represents a different size length. The machine simply reads from smallest to largest using the colors for the nucleotide. Wisdom89 (T / C) 15:11, 21 April 2009 (UTC)
This is an excellent link [1]. Wisdom89 (T / C) 15:14, 21 April 2009 (UTC)
Imagine that you only want to know where all the Cs are. So you do the reaction with As, Cs, Ts and Gs, but you also add a bit of dideoxy Cs. Then you can separate the products on a really good gel. Then you see a band at size 5, 7, 11, and 23 nucleotides (for example). This tells you that your sequence is XXXXCXCXXXCXC.You could repeat in separate tubes, but the dyes are just a shortcut to do it all in 1 tube. Hope that helps. Hit me up on my talk page if you want any more help. Aaadddaaammm (talk) 19:17, 27 April 2009 (UTC)


Viruses don't exist in the fossil record. How long ago do scientists believe that they first appeared? (talk) 15:51, 21 April 2009 (UTC)

Virus#Origins says: "Viruses are found wherever there is life and have probably existed since living cells first evolved." --Tango (talk) 15:54, 21 April 2009 (UTC)
Just a comment (slightly offhand), but Viruses aren't really considered's the whole obligate intracelluar parasite definition. That may be a reason why they do not exist in the fossil record. Wisdom89 (T / C) 15:55, 21 April 2009 (UTC)
Well, the reason they don't exist in the geological record is because they are too small to form recognizable fossils and their molecular components can't survive for geological times, even in the rare Lagerstätte that preserve soft tissues. There are "genetic fossils" consisting of viral DNA that has been incorporated to the genomes of living organisms, but it's hard to see how that can be used to date viruses further back than 500 million years at the very most. Looie496 (talk) 16:13, 21 April 2009 (UTC)
Yup, excellent point - I was going to mention the small size, but my first instinct was "alive"? That seems to be the first thing people think of when viruses are mentioned. : ) Wisdom89 (T / C) 16:21, 21 April 2009 (UTC)
And classification is based on things such as the nucleic acid composition/sero markers/envelope etc.. and actual morphology - the latter only being successful with the advent of electron microscopy me thinks, and the former with molecular genetics. Wisdom89 (T / C) 16:37, 21 April 2009 (UTC)
If the furthest back that viruses can be dated is 500M years, where does the assertion that they probably existed as long as living cells come from? (talk) 18:23, 21 April 2009 (UTC)
There is no evidence of when the first viruses arrived, and only indirect evidence for viruses on any timescale that isn't virtually now. That said, viruses are so simple (evolutionarily speaking) that it seems logical to predict that they would have arisen not long after the evolution of the first cells. Dragons flight (talk) 18:58, 21 April 2009 (UTC)
For sure we're not likely to find direct evidence for them. To the degree that they inadvertently dump pieces of their DNA as 'junk' sequences into that of 'normal' lifeforms, we can look back and say things like "this exact sequence of base-pairs appears in horses, dogs, people, koala bears and elephants - so it must have been from a virus that was around before the common ancestor of all of these animals"...if (for example) we found the same "junk" viral snippet in all plants AND all animals AND all Fungi, Bacteria, etc - then we'd be in a position to strongly suspect that this virus was around at the very beginning of life. But that is rather indirect evidence. SteveBaker (talk) 19:26, 21 April 2009 (UTC)
Or alternately instead of a common ancestor, perhaps a virus infection has transferred the genes from one species to another. This would appear more likely if the gene was missing from most other organisms. This happens with bacteria transferring genes to unrelated bacteria. Graeme Bartlett (talk) 21:02, 21 April 2009 (UTC)
The best chance to trace back viruses would be by their pathogenesis. It is not uncommon to find signs of disease or trauma in the fossils. I am not aware of any fossils that exhibit clear effects of viral disease of any sort, but that certainly does not mean there aren't any. In any case, I am talking about plants and animals that actually leave fossils large enough to be studied for the signs of any pathology. Viruses probably evolved long before that. --Dr Dima (talk) 20:22, 21 April 2009 (UTC)
Your argument doesn't make sense. Not all DNA comes from viruses, so the DNA shared between those species could just have come from a common ancestor originally. If two species share a bit of DNA but another species known to be in the smallest clade containing the first two species, then that might be evidence that both species were infected by the same virus some time after all three species split. (It could also be explained by mutation in the 3rd species, of course, examining more species would be required to get a conclusive result.) --Tango (talk) 12:21, 22 April 2009 (UTC)
To me, the most compelling evidence is the tropism that different viruses have for certain organisms, suggesting a very long period of coexistence.
  • Bacteriophage only affects bacteria
  • Tobacco mosaic virus is an example of a virus that only affects plants
  • Mycoviruses only affect fungi
  • Mimivirus is a virus found in infect primitive unicellular organisms like amoeba
  • There are numerous examples of viruses that affect only animals (and sometimes very specific species)
One possible explanation for this finding is that viruses existed as early as the primitive cells that were the common ancestors of all major branches of the tree of life, and then evolved in parallel with a group of organisms, gradually becoming selective for the replicative machinery or cellular physiology of that specific group. An alternative explanation is that viruses popped into existence at some point when all the major taxonomic groups were established, and somehow then became specific for those distinct kingdoms and phyla. The first of these is the simplest explanation (which as scientists we tend to like the best) -- that viruses "have probably existed since living cells first evolved." The mimivirus article suggests that it may even predate cellular organisms. --- Medical geneticist (talk) 21:02, 21 April 2009 (UTC)
Are all viruses harmful? Because if they were, and viruses just popped into existence wouldn't they basically kill species too fast for them to develop an immunity to them? An immune system wouldn't even know what a virus was. So I think the spontaneous virus appearance could be discounted. (talk) 13:24, 22 April 2009 (UTC)
Right, this is my point -- there's a balance between the ability of the virus to enter the cell, replicate itself, and destroy the host cell (what you might consider being "harmful") with the ability of the organism to detect and destroy the virus before too much damage is done -- and this balance has been achieved over millenia of evolutionary "warfare" between viruses and their hosts. Often the viruses are so specific for the cell surface molecules expressed in their natural host species that they are completely incapable of gaining entry into cells from another species. However, consider what happens when a virus is able to move from its normal host into a host from a different species, usually the new host doesn't cope very well with the infection because the immune system has never "seen" anything like it (examples include bird flu and other zoonotic diseases). I only proposed the "alternative explanation" of viruses "popping into existence" to show how poorly this would explain the observed situation of host tropism. --- Medical geneticist (talk) 13:40, 22 April 2009 (UTC)
Things like viruses and bacteria that make a living by making other lifeforms sick have to be very careful not to kill off their hosts too rapidly or else they'll be unable to spread. I saw a study a few years ago about how "new" diseases are often extremely lethal for the first year or so - but then gradually lose their potency. That's because the disease organism is evolving. The bacteria/virusses that kill their hosts within hours have a very tough time spreading because the host doesn't have time to get close to enough others of it's kind to pass on the illness before it drops dead. Those bacteria/virusses have a hard time passing on their genes once the host dies - so the less virulent amongst them that allow their host to continue to live and (importantly) get close to others of it's kind - will be the survivors. So I don't think you can assume that all of life would be annihilated on the very first occasion it encountered a disease virus...evolution doesn't work like that. SteveBaker (talk) 19:49, 22 April 2009 (UTC)
I don't think anyone made the assumption that "all of life would be annihilated on the very first occasion it encountered a disease virus". But when viruses jump from their normal host (in which they've evolved to balance their ability to propagate versus the damage to the host, as you very correctly point out) into a new species (i.e. US), we often see horrible, horrible diseases like SARS, West Nile encephalitis, hemorrhagic fever, or Ebola. NOTE, however, that even in these terrible illnesses only a fraction of the infected individuals actually die, it's just that the fraction of people that DO die is much higher than other viral illnesses to which our immune systems have evolved to cope with. --- Medical geneticist (talk) 14:27, 23 April 2009 (UTC)
It is a common misconception that viruses are either inherently pathogenic or cytopathic. Viruses with those properties have been studied intensely for obvious reasons, and historically it was hard to discover and study viruses so efforts were focused on the ones that caused disease (pathogenic) or easy to identify (killed/injured cells in culture = cytopathic). More recently, it's become clear that we're awash in viruses that cause no apparent disease. Notable examples include GB virus C and TTV. These viruses don't appear to kill the cells they infect, and don't harm the people whom they infect (to our knowledge). In the past, we'd never have known about them, but with PCR it appears that most of us harbor TTV, for example. So, virus does not intrinsically equal disease or cell death. It seems likely to me that most viruses don't cause any disease - they just propogate quietly. --Scray (talk) 04:59, 23 April 2009 (UTC)
This is an excellent point, and it is another great piece of evidence that viruses (not to mention bacterial commensals) have been co-evolving with their hosts for millenia. --- Medical geneticist (talk) 14:27, 23 April 2009 (UTC)

Surly we can say that the immune systems of life on the planet come from being atk by virus amongst other things now if we apply that to a Crocadile then it goes to say that they date back to the oldest animals living on the planet.....

10:02, 18 August 2010 (UTC)ChaufriChaufri (talk) ::: I believe viruses didnt arise much way back. The climatic scenario would have been unbearable for viruses of the old times. For me viruses evovled in the present day scenario (reffering to present day land dwellers). Viruses are broken DNA/ pieces from dying cells, pieces of DNA/RNA that were responsible for multiplication (contained genes for multiplication), when exposed to external environment of that dying cell, somehow adapted to it, collected a protein capsid.... Became A ViRuS.

 Thus those viruses could only duplicate themselves in their respective MOTHER CELL from where they originated...... 

i.e. Bacteriophafes only attack bacteria... etc etc  ;)

Increase in rolling resistance on a wet road?[edit]

This question has been bugging me for a while, and I'm unable to find any figures on the net about this. When a car travels along a wet road, the tyre acts as a "pump" to move water away from the contact patch of the tyre. This uses some of the kinetic energy of the car, although some presumably is recovered as the water flows back in to the space behind the tyre, pushing it a little. Also, presumably, the majority of this energy is used in the process of moving this water out of the way of the tyre, heating the water, atomizing it into a spray and producing the characteristic noise associated with cars on wet roads. Not to mention the "stickyness" of water causing extra friction.

Does anyone have any figures for how much energy this process takes? For example, what kind of economy penalty can I expect in an average car at a given speed?

I'm aware that "contaminated" runways incur a performance penalty in aircraft, can we apply the same formula to cars? (talk) —Preceding undated comment added 19:41, 21 April 2009 (UTC).

Certainly it's very noticable how a car slows down faster if you put it into neutral on a wet road than on a dry one - and if you run through a deep puddle in a small car, you can really feel it slowing you down. So there is certainly an effect - and for water in maybe the quarter-inch-or-deeper range, it's gotta be pretty significant. As for quantifying it...I've never seen anything like that out there and a Google search on likely terms didn't turn up anythink of use. The figures for aircraft tyres may not be comparable. Aircraft tyres are optimised for going in a straight line and not imposing too much drag on takeoff - where car tyres have to cope with the much more tricky business of cornering. If you look at an aircraft tyre, you'll see it has a simple circumpherential tread pattern with none of the fancy zig-zag or diagonal grooves you see in the tread patterns of cars - and that suggests to me that pumping water out from under the tyre isn't so important to them. So I don't have a good numerical answer for you - beyond that it must be reasonably large because of the degree of deceleration you feel when you coast through even a half-inch-deep puddle and that you can't use the aircraft figures. SteveBaker (talk) 20:07, 21 April 2009 (UTC)
Another difference between cars and planes which may be relevant is that the wheels of a car are its means of propulsion, they aren't on a plane. (Which is why, as we all know by now, planes can takeoff on a treadmill running backwards at takeoff speed.) --Tango (talk) 23:34, 21 April 2009 (UTC)
Just one data point.. I've noticed a decrease in highway mileage, often significant, in rain. Say, down to 28mpg from a more normal 32. Friday (talk) 20:09, 21 April 2009 (UTC)
Yes - although some of that would be increased drag due to the raindrops effectively increasing the density of the air...also, you're running your wipers and (hopefully) your headlights - although that won't make a lot of difference to your mpg numbers. SteveBaker (talk) 01:16, 22 April 2009 (UTC)
Tire treads have aggressive cross-cuts or grooves to provide a place for the surface water to go so that "the rubber meets the road" and provides traction. Does this cause the tire to do work by lifting water from the pavement and presumably throwing it out sideways to make room for the water in the next rotation? If so, then the tire is acting as a pump, and the car engion or the kinetic energy of the car is the source of the energy, causing the car to slow down or requiring greater fuel per distance driven. Edison (talk) 14:10, 22 April 2009 (UTC)
Yes - that's exactly the mechanism - but it's hard to estimate the magnitude of it in order to answer the OP's question. Knowing the depth of the water and the speed of the car and the width of the tyres - we can figure out the amount of water that's being "pumped" away by the tyres - but we don't know how much kinetic energy that water leaves with - so we can't really figure out how much energy the car loses in doing that. We certainly know it's bigger than zero...but beyond that??? SteveBaker (talk) 19:42, 22 April 2009 (UTC)

The Beauty of the Universe[edit]

I might have the wrong section, please direct me to the right area if I do.

I was looking at photos of the Universe, specifically of Saturn's moon and rings, and I was completely awe-struck by it. You know, a deep down feeling that something is incredibly beautiful. I was not alone. The website's commentators made many similar remarks. They too don't seem to be alone. In general, it seems like most people find "beauty" in outer space. Here's my question, and it deals with the anthropology side of evolution. If humans evolved beauty in response to let's say conditions that promoted life (ex. a lake provides water ... landscape of a lake looks beautiful), why is it that things beyond our world, things that can't provide any form of subsistence strike such a note inside of many humans? —Preceding unsigned comment added by (talk) 20:52, 21 April 2009 (UTC)

Is it beauty you are perceiving or awe? You use the term "awe-struck", which is how I would describe myself when, for example, I first saw the moon through a telescope. I think there is a difference between awe and beauty. Beauty (in this context) is a purely visual thing, but I think in order to be awe-struck by celestial objects you need a certain amount of understanding of what they are. You have, however vague and imprecise, a sense of the size and distance of the thing you are looking at - I think that is an important factor. I'm not sure what the evoluntionary benefit of awe is, though, so I can't really answer your question, just ask a slightly different one! --Tango (talk) 21:56, 21 April 2009 (UTC)
The question is pertinent in matters closer to home, I think. When did a person first look at a range of snow-capped mountains and find it beautiful, rather than simply forbidding? What was up with that?

I once read an account of a troop of chimpanzees, working their way through a jungle. They emerged into a sudden clearing, and beheld a humongous waterfall with water cascading great distances over rocks. Very dangerous. They started shouting, and jumping, and looking at it, and reacting with... what was that? Is it somewhere on the continuum towards an aesthetic sense? Impossible to say, I'm sure. -GTBacchus(talk) 22:02, 21 April 2009 (UTC)

I believe I came across something a while ago that said the Romans and Greeks normally regarded forests and nature generally as threatening rather than beautiful, and the modern thing in the West of seeing nature as beautiful started quite recently with Romanticism in the 18th century. Dmcq (talk) 22:40, 21 April 2009 (UTC)
Exploration is a major driving force for today's humanity, especially as our resources and avilable useful landspace becomes more and more scarce. Perhaps your subconscious is telling you that Saturn actually has vast quantitiies of useful supplies that we could utilise. —Preceding unsigned comment added by Vimescarrot (talkcontribs) 23:03, 21 April 2009 (UTC)
You respect and fear the enemy's strength; fearing big dangers is obviously advantageous. It turns to beauty and awe when you fear and admire your alpha male or chief, and promote the most fearsome warriors to high position. Being fearsome becomes favored (aesthetically pleasing)... so huge objects convey might and you hold them in awe. (talk) 23:18, 21 April 2009 (UTC)


Well, to rain on the parade a bit, there are vast numbers of things in space that are utterly boring. You don't generally see pictures of them. And even for the things you do see pictures of, the colors are often greatly enhanced. Looie496 (talk) 00:15, 22 April 2009 (UTC)

To me, there was no danger in viewing the object. I understand my own feelings of danger or vulnerability. I've seen photos of astronauts in space juxtaposed to the looming Earth. There a simple sense of vulnerability and empathy for that man consumed my thoughts. Rather, when I saw the picture of Saturn's moon, with its craters and pale white color, without any coaxing, I felt that it was beautiful and like I said I was awe-struck. The image was viewed upon a 17 inch monitor, consuming maybe 1/2 of the screen. I don't think I feared its size, nor felt in anyway that it resembled a human that I might fear.

I think it's mostly observer bias. If you are an astronomer - in any given year, maybe you'll take hundreds of thousands of photos that are basically white dots scattered at random on a black background - and a couple of gaseous nebulae with unusual dust formations, etc. Which ones get nice names like "The Horsehead nebula" and go on your web site...and which ones get some six digit serial number with the date on the end and are kept in your large collection of other similar pictures that nobody ever sees?
Also, they have a lot of control over the look of the things. Most scientific data is collected in regions of the electromagnetic spectrum that humans can't see - so the "photos" aren't really photos at all - they are the result of running a bunch of computer programs on a string of numbers. You can make the colors come out any way you want - you can enhance the 'pretty' bits and tone down the 'ugly' bits. While you probably won't do that for the purpose of extracting scientific information - when you are preparing an image to put on your web site or the cover of your next book - you're very likely to set the software up with some pretty pastel colors and tweak them until it does look beautiful. There is no "right" or "wrong" when it comes to using "false color" techniques. So what you are seeing isn't that all of space is somehow beautiful - you're seeing just the bits that someone who stares at these things all day long finds beautiful...tweaked to make them look even more beautiful. It's no surprise that the results are usually pleasing. SteveBaker (talk) 01:12, 22 April 2009 (UTC)
Erm. I'm 100% sure these weren't enhanced by the computer. I was looking at a picture of Saturn's moon. It might have been cropped for dramatic effect, but it still doesn't change the emotional response I observed. —Preceding unsigned comment added by (talk) 01:34, 22 April 2009 (UTC)
I'd be VERY surprised if the image you're thinking of was taken in Red/Green/Blue light at normal intensities and displayed with nothing more than cropping - they simply don't put that kind of instrument onto deep space probes because RGB photographs simply don't contain much that's of scientific benefit. The image was probably taken in IR or UV or with a monochrome camera using some combination of polarizing filters or something. If you're "100% sure" - tell us (in detail) how come you're so sure - because I'm REALLY sure you're 100% wrong! SteveBaker (talk) 04:02, 22 April 2009 (UTC)
Care to tell us what image you're talking about? To me, most pictures of Saturn's moons look like relatively boring lumps of rock. Sometimes lumps of rocks with an equally boring gray line behind them. (Except the one that looks like the Deathstar.)
One things that moon and asteroid pictures usually do have going for them is that they typically have pretty dramatic lighting. I'm not sure if that makes them "beautiful", but it certainly makes them striking. APL (talk) 03:35, 22 April 2009 (UTC)
Oh, actually, there's a very dramatic image of Mimas (The deathstar look-alike) that's just as you described, right on the Mimas page. It is a great image. It's aspect ratio will make it a good background image for my tablet PC. However, be aware that this is not a natural color image. Instead of Red/Green/Blue, it was taken in IR/Green/UV. The colors had to be adjusted to look approximately correct. (Here's a similar image in true color.]) APL (talk) 03:51, 22 April 2009 (UTC)
Yeah - there is no way an image like that has not been processed in some way. As our caption says - it was photographed in IR, Green and UV light - not Red, Green, Blue - and the interpretation of those three frequencies into light that we can see is largely an artistic matter. SteveBaker (talk) 04:02, 22 April 2009 (UTC)
Cassini's "red, green and blue" filters
I've been curious for a while about how true NASA's true-color images really are, so I went and tracked down the actual spectral response curves for Cassini's filters. They're available here. The description of "Nature's Canvas" (which APL linked above) says that it's a true color image made using red, green and blue filters. The source images are [2] [3] and [4], which were taken through the RED+CL2, CL1+GRN, and BL1+CL2 filter pairs respectively. (CL1 and CL2 are clear filters.) On the right is a plot of the camera's frequency response curve with those filter pairs in place. The horizontal scale is wavelength in nanometers. I'm not sure what the vertical units are but I think they're CCD electrons per incoming photon. The vertical scale is linear and the maximum is around 0.23.
One interesting thing about these filters is that, compared to the human eye, they have very little ability to distinguish monochromatic colors. For example, they can't tell the difference between blue and violet—they both show up as a nonzero value in the BL1 channel and zero in the other two channels. There might be a little bit of variation in the brightness of the BL1 channel, but that doesn't help because there's no way to tell the difference between a change of wavelength and an actual change of brightness. There's also no frequency discrimination in the 500–570 nm and 640–730 nm ranges, and very little in the red-yellow range where the RED and GRN filters overlap. If the value in the BL1 channel is zero and the values in the GRN and RED channels are nonzero and roughly equal, the spectrum might have a single peak somewhere in the red-yellow range (which a human would perceive as red/orange/yellow) or it might have a peak in the infrared and another in the 500–570 nm range (which a human would perceive as green or cyan). There's no way to be sure. So you can't, strictly speaking, produce a true-color image from these filters.
On the other hand, real-world spectra are pretty predictable—they don't vary much across the visible range. If you can come up with a model with only three adjustable parameters that approximates the spectra you actually expect to find in the scene, then the values from the BL1, GRN, and RED channels together fix the parameters of the model, and from that you can work out sRGB coordinates. A simple example would be to model the spectrum (in units of photons/m²/s/nm) as a quadratic function of the wavelength. I actually tried doing this and got
(where I've applied an overall normalization to the matrix so that the largest entry is 1). So in this simplistic model you can pretty much plonk the BL1 data into the blue channel, but the red and green channels are more complicated. There's also the fact that I don't know how the CCD electron counts are related to the pixel brightness in the raw JPG/TIFF images, and this calculation gives you linear sRGB values which need to be gamma corrected, and my model isn't very good, and I probably made a mistake in the calculation. But anyway this gives the general idea of what you have to do to compose the raw images into something that might (if you used the right model) resemble true color. Note that you can get better color accuracy by using more than three filters, even though there are only three output channels, because with more inputs you can fit more parameters. The only exceptions are if your model is perfect already or you have three filters that are independent linear combinations of the human cone responses (in which case the model is irrelevant). You could produce a true color image from IR/Green/UV channels by this technique if you had a good enough model. I have no idea whether the official NASA images are really produced this way, though. I get the impression they do a lot of retouching to get the colors right, though in that case I don't understand why they use three source images—if they know the right colors beforehand, couldn't they just colorize a single one?
Incidentally, if you look at the three source images you'll notice that Mimas moves significantly against the background rings, so there was a fair amount of non-color-related Photoshopping required here too. Even more so with the sources for "Mimas blues" ([5] [6] [7]). Not that there's anything wrong with that, it's just interesting. -- BenRG (talk) 00:48, 23 April 2009 (UTC)
One reason why we think some astronomical objects are pretty is symmetry. Saturn's rings are rather symmetrical, as are the arms of a spiral galaxy. A planet or moon in a pic that shows no detail looks pretty, too. When you get to a resolution that shows the pockmarked craters and such, they don't look quite so pretty any more. So, then, why do we have this preference for symmetry ? Since many biological systems use symmetry, a symmetrical plant, animal, or person is more likely to be healthy, so a better choice to eat, own, and/or mate with. StuRat (talk) 15:40, 22 April 2009 (UTC)

how much biological output is produced (by either weight or volume) daily by all of the world's population combined?[edit]

I've tried not to be too direct, but you can skip this question if you are having dinner or something. My question is: how much biological output is produced daily by all the people of the world combined, per "type". Either by weight or by volume.

This is surprisingly hard to find, I tried googling both total, and average production for both types using several phrases but could not find any numbers at all. Any ideas? (talk) 21:28, 21 April 2009 (UTC)

By "biological output", do you mean feces and urine? And by "world's population" do you mean human population? If so, according to urine: "In adult humans the average production is about 1 - 2 L per day." Since there are about 6.8 billion people in the world, that comes to a total of about 7-14 litres/kgs of urine per day (actually, it's probably a little less since children presumably produce less than adults). I can't seem to find the appropriate numbers for feces, though... --Tango (talk) 21:46, 21 April 2009 (UTC)
I think you missed a rather important "billion" in your answer :) In terms of faeces a roundabout figure would be 500g/person/day which gives about 3.5 million tonnes per day... NICE! Smartse (talk) 21:16, 22 April 2009 (UTC)
Do exhaled (and other end) gases count? What about evaporated water, and shedding of hairs/skin flakes? ~AH1(TCU) 21:49, 21 April 2009 (UTC)
The OP said "both types", so we're looking for just two types. Feces and urine seem to be the most obvious two. --Tango (talk) 21:52, 21 April 2009 (UTC)
Food statistics might be easier to find (and nicer to contemplate) than waste statistics. I would assume that the total mass excreted as feces is less than the total mass ingested as food. If you assume that my daily poo weighs... one half as much as my daily bread? You'd probably be accurate within an order of magnitude, and this kind of calculation isn't going to be much more precise than that anyway, right?

More direct information about volume of waste might be available by considering a city and how much waste is treated daily - something else you could probably look up. -GTBacchus(talk) 21:54, 21 April 2009 (UTC)

The total excreted as feces and urine will be less than the total consumed as food and drink, I'm not sure you can simply separate the two, though. Feces is mostly water, whether that is water that comes from the food, or whatever that comes from drink is difficult to determine (or even define). The waste processed by a city will be mixed up with lots of other stuff (mostly water from the mains supply and rain), so I doubt you'll get useful figures from that. --Tango (talk) 22:14, 21 April 2009 (UTC)
We do have an article that provides some per-person estimates, i.e. about 1600 mL/day (feces + urine). You could do some VERY rough estimation using this info. --Scray (talk) 02:30, 22 April 2009 (UTC)

What about handling the question as if it were asked like How much inorganic matter is turned into organic matter by the Earth's biosphere daily? —Preceding unsigned comment added by (talk) 00:27, 23 April 2009 (UTC)

That would be a question about plant life, which is not usually meant by the word 'population'. —Tamfang (talk) 21:44, 10 May 2009 (UTC)


Obviously, everything that exists in this world consists of specific elements, thus giving us it's molecular, or empirical formula. Now if we look at anything along with it's molecular/empirical formula, that certain thing consists of a "geometrical chemical shape." So, if everything has it's own shape, everything can be cured with some form of conversive, contradicted, form of that matter, which is what we call medicine. -- So, TO MY QUESTION, does cancer have a molecular, or empirical formula? and if so, can you lead me to a site with it's geometrical shape?

Thanks (talk) 22:03, 21 April 2009 (UTC)

No. Cancer is made up of cells, just like any other living tissue. The difference between cancer cells and other cells is just that cancer cells reproduce out of control. The difficulty with curing cancer is that the cancer cells are very similar to the non-cancer cells and you have to come up with a way to kill the cancer without killing the patient, which is very hard to do. --Tango (talk) 22:11, 21 April 2009 (UTC)
You have a basic idea, which is correct, that every substance is composed of specific elements which form molecules. However, the point you appear to be missing is that cells are made up from billions and billions of these molecules. Cancer is a process which affects cells as a whole, and cannot be treated by a lock-and-key mechanism which you appear to be describing. Instead, cancer must be treated by either limiting damaged, uncontrollable cells replication, or by killing off those cells which are damaged. I recommend you read up on cell (biology) which should give you an insight to what cells are composed of. If you have further questions, feel free to come back. Regards, --—Cyclonenim | Chat  22:44, 21 April 2009 (UTC)
Okay, but even if cancer is made up of cells, don't these cells contain specific elements? And just like other viruses or bacteria, can medicine not be produced to react with these compounds that would cause the inactive cells in cancer to "undo" their inactiveness, and make them re-active, or turn them into another type of matter that would be helpful and plentiful to the body? If we could find the molecular formula, could we not change these cells into matter that would nuture the body instead of destroying it? (i.e. Some type of protein, sugar, hormone, etc...I'm not definite on the subject, it is just interesting, so I'm only throwing out some creative ideas!)
Thanks for the responses!
ThePreventor (talk) 00:04, 22 April 2009 (UTC)
P.S. I made an account. ^ ^ ^ —Preceding unsigned comment added by ThePreventor (talkcontribs) 00:05, 22 April 2009 (UTC)
The problem is that the cancer cells are made up of exactly the same elements as the non-cancer cells. The differences are really tiny - a couple of protein molecules in a slightly different place, that sort of thing. We can do all kinds of things to cells, but we need to find ways of doing them to just cancer cells, which is hard. We do have ways of combating cancer and are inventing new ways all the time, but it is a really difficult problem to solve so we haven't got any perfect solutions yet. --Tango (talk) 00:17, 22 April 2009 (UTC)
All biological tissue is made almost entirely from carbon, hydrogen, oxygen and nitrogen - with a few bits and pieces of other elements. But the amounts and ratios of those things are very similar between (say) a lung cancer cell and a healthy lung cell. In fact, they might have utterly identical amounts of those elements - the only difference being something very subtle about the arrangement of them...and even then, the mis-arrangement is just in the DNA and that's a microscopically tiny fraction of all of the chemicals in the cell - just a few misplaced atoms in just the wrong place is enough. Worse still - a healthy muscle cell is way different to a healthy lung cell - but a cancerous lung cell is much more similar to a healthy one than the muscle cell is. These difficulties probably explain why we have not yet evolved a way for our bodies to cure themselves of cancer just as we can cure ourselves of the common cold. Most of the treatments for Cancer depend on targetting the way they behave. So when they go nuts and start reproducing like crazy, they don't build things like the blood vessels they need to get there are tricks like treating the patient with drugs that slow the development of new blood vessels that'll starve out the cancer cells and hopefully reduce their numbers. Sadly, doing that also prevents new blood vessels that you actually NEED from forming - hence the treatment can make you even sicker than the cancer did. SteveBaker (talk) 00:54, 22 April 2009 (UTC)
Steve, in fact our bodies have evolved ways to cure themselves of cancer. But it doesn't always work. Read killer cells. Dauto (talk) 01:20, 22 April 2009 (UTC)
As others pointed out, the difficulty lies on the fact that cancer cells are so similar to normal cells. They are descendant from normal cells after all. But there are subtle methabolic differences that can be used to attack them. The lock and key idea is actually a good one and our own body makes use of some of those sublte methabolic differences to find the cancer cells and kill them. But there are no magic silver bullets and sometimes things get off hand. Dauto (talk) 01:03, 22 April 2009 (UTC)
Is it not possible through research that we could identify these microscopic, subtle changes in the inactive, harmful cancer cells to reverse the process by means of injecting some sort of "medicine" into the general area of the cancer? Or, is this what all the research for cancer is searching for? Since the alterations in the DNA sequences are microscopic, does this mean that the "lock and key" idea would not work because it would be impossible to specifically locate infected, maladaptive atoms (molecules) inside of the DNA sequences?
ThePreventor (talk) 02:04, 22 April 2009 (UTC)
Indeed cancer research is directed toward finding shared characteristics of cancers that might represent therapeutic targets. There is no single simple DNA sequence change that is shared by cancers, not even for a single type of cancer. Sometimes there are themes that are shared, like suppression or mutation of tumor suppressor genes like P53, or over-expression of a protooncogene like myc, but these are neither uniform nor easy targets - they are "normal" genes being expressed at the wrong level for a particular cell type. Extremely bright and highly motivated people, many of whom have friends or family affected by cancer, are heavily engaged in this work. --Scray (talk) 02:21, 22 April 2009 (UTC)
All cancer treatments are dependent on exploiting the effects on the cell that the changes in its DNA has on it. The entire concept of chemotherapy is to develop toxins that kill cancer cells faster than normal cells. The problem with what you want is that the immutable differences between cancer and normal tissue (the changes in the DNA code) cannot be targetted by any developed method. This paper describes a fascinating (and theoretical) way of doing it, but at the moment, we're stuck with toxins, radiation, and cutting it out. Someguy1221 (talk) 02:15, 22 April 2009 (UTC)
And immunotherapy applications. Wisdom89 (T / C) 04:53, 22 April 2009 (UTC)
I would hope that, at some point in the future (decades perhaps), a cure for all cancers could be developed which would work like this:
1) Take a sample of cancer from the affected individual, and also a sample of the same tissue without cancer from that individual (the "control").
2) Run both samples (with thousands of cells in each sample) through a computer which will analyze the genetic code and find the difference in the cancerous cells.
3) Program a virus to search for those cells which contain the cancerous genetic code. When it finds them, it can repair them, kill them, or mark them in some way so other agents (the person's own immune system or chemotherapy drugs) can then kill them. It would also be a good idea to make this virus incapable of reproduction once introduced to the patient's body, so the rate at which it works could be controlled. The virus could also be programmed to self-destruct once it finds a cancerous cell and does it's thing. If this control isn't present, so much cancerous tissue could be killed all at once that this would cause a new problem, a mass of decomposing tissue too large for the patient's body to clean it up quickly.
If the cancer has metastasized (spread to other organs/systems), then it may be necessary to repeat this process for each organ/system. StuRat (talk) 15:23, 22 April 2009 (UTC)
Good idea StuRat. That's pretty much what my idea was, which I titled "the lock and key." If we could track the genetic variations inside of the DNA samples, then we could find the "key" that would fit into the "lock" that would then reverse the process of the cancer, either [like you said] killing it, healing it, and/or making it beneficial to the body.
ThePreventor (talk) 01:28, 23 April 2009 (UTC)
Lock-and-key isn't really a new idea, it's used in regards to enzymes and their substrates too. This method for curing cancer, however, it a pretty futuristic idea since at the moment we do not have a way to repair individual cells. The idea that they could be killed, perhaps by nanorobots when they are developed, is an interesting one that may be possible in the very long term future. That said, I prefer the idea marking cells with chemical markers so that the immune system can destroy them. That sounds the most plausible in time scale terms, but it's still a long way off. Regards, --—Cyclonenim | Chat  07:04, 23 April 2009 (UTC)
StuRat makes an interesting point, but the idea of programming a virus to detect "the cancerous genetic code" is a bit far-fetched. The approach that seems to have people excited right now is to try to detect a gene expression profile that can uniquely identify a cancer cell; or even better a cell surface protein that is only expressed on cancer cells, and use drugs that can either target a key pathway that's abnormal in cancer cells or take advantage of the cancer cell surface marker to kill cancer cells more directly (rather than using systemic cell poisons). See Gleevec and Herceptin for current approaches that are based on these ideas. --- Medical geneticist (talk) 14:35, 23 April 2009 (UTC)
Detecting the cancerous genetic code is a bit far fetched, but it's one that (for some cancers) the science might exist now to make feasible. Check my post somewhere above on a PNAS paper on doing just that. The idea is to create a lethal vector that is inactivated by non-mutated DNA. Although I believe the author of that paper himself once said he hoped it would be a reality by 100 years from now, so that gives you sense of what he's even sure of. Someguy1221 (talk) 08:02, 24 April 2009 (UTC)
The only problem with that approach is that it may miss dormant cancer cells which currently don't exhibit any expression of the cancer. StuRat (talk) 07:57, 24 April 2009 (UTC)
Nanorobots is a pretty crazy, futuristic idea that would be great, but as you said, it is very far off. I've never heard of Gleevec and Herceptin though, but that's pretty cool. I'm not sure how you would trace and mark inactive cancer cells though, how would you? Wouldn't the tracer have to be the "key" to the cancer "lock" to be able to find the inactive cell in the mutated DNA?
ThePreventor (talk) 02:01, 24 April 2009 (UTC)
The virus that identifies a cancer cell could then produce a chemical marker that would migrate to the cell wall. This could then be detected by other agents and/or could grant them access to the cell interior. StuRat (talk) 07:54, 24 April 2009 (UTC)
The virus wouldn't necessarily have to produce a marker. There are plenty of extremely lethal protein toxins, like translational inhibitors, the virus could make on its own to kill the cells pretty effectively. Someguy1221 (talk) 08:02, 24 April 2009 (UTC)
Right, but how would a virus know WHICH CELL is the cancer cell compared to normal cells? This is what I was saying, wouldn't the virus cell almost be like the "key" to the cancerous "lock" cell?
ThePreventor (talk) 01:24, 25 April 2009 (UTC)
A synthetic enhancer of gene expression could be developed that only activates when a specific mutated DNA sequence is present (or a synthetic inhibitor could be developed that only activates when the normal DNA sequence is present). This would cause the remaining viral genes (that make lethal proteins) only activate in the cancerous cells (or only deactivate in the normal cells). This would require a knowledge of the complete DNA sequence of a patient's cancer, as well as their normal DNA. Additionally, there's the problem that not all cancer cells in a given cancer are identical (that's how resistance arises to chemo), so ideally the "lock" would have to be one of the earliest mutations to occur in the cancerous cell line. That said, there's also the problem that any protein designed to activate on binding a particular DNA sequence will have some degree of response to very similar sequences. That makes large deletions of DNA the safest mutations to target. In the paper I linked to previously ([8]), they describe doing exactly that. The actual key to their idea is a theoretical pair of restriction enzymes that only activate when they bind the normal DNA sequence that was deleted from the cancer cells. This restriction enzyme then destroys the lethal gene that was introduced along the restriction enzymes. So, precisely what you wanted, except backwards. There's a virus floating around the body that will try to kill any cell it enters. It has a self-destruct mechanism with a lock on it (the restriction enyzmes). The key to activate the virus' self destruct mechanism is normal DNA that is absent from the cancer. So all the cancer cells die, and the normal cells never know they were visited. Someguy1221 (talk) 01:55, 25 April 2009 (UTC)
So, once a restriction enyzme cuts the DNA down the two backbones, what happens to it? If the DNA notices the cancer cells and "self destructs" them, what happens to them?
ThePreventor (talk) 21:29, 25 April 2009 (UTC)
An example of how it could work would be that the virus carries a lethal gene that codes for a toxin that blocks all protein synthesis, eventually killing whatever cell it entered. The restriction enyzmes are the self destruct mechanism, and they can only be activated by detecting the normal DNA. Once the DNA is cut, it slowly dissolves into individual nucleotides from normal cellular processes. So the cells that have normal DNA cause the virus to destroy itself before enough toxin is produed to kill the normal cell. Someguy1221 (talk) 07:32, 26 April 2009 (UTC)
If the DNA splits into multiple nucleotides, do those eventually come back together to form a new strand of DNA?
ThePreventor (talk) 15:59, 26 April 2009 (UTC)
A large piece of DNA (one of the chromosomes) can be repaired by non-homologous end joining or homologous recombination, but the small viral DNA will be completely consumed by DNAses in the nucleus. Once it's dissolved into individual nucleotides, all of its information is permanently lost. Someguy1221 (talk) 16:11, 26 April 2009 (UTC)

Mechanics question for personal interest[edit]

If the world record holder in the long jump decided to jump from the top of a mountain, how far would he be both horizontally and vertically from the point at which he jumped at the moment he started to fall vertically? (talk) 00:19, 27 April 2009 (UTC)

Hiding from thermographic camera view by covering oneself in thick mud from head to toe...[edit]

...malarkey or effective way? Yes, I'm a Predator fanboy.

That wouldn't actually work in Real Life, would it? Yep, I'm aware that the Predator's visual filter mask is alien technology and may not (in the story) *actually* be a thermographic camera, in the way that we think of one. --Kurt Shaped Box (talk) 23:17, 21 April 2009 (UTC)

You might be able to get it to work for a short amount of time, but if it worked over a long period it would kill you. The human body produces a significant amount of heat and if that heat isn't allowed to escape the body rapidly overheats. If the heat is escaping, then it is visible to a thermographic camera. A better option is heating the surroundings up to body temperature (uncomfortably hot, but not fatally so, at least if you keep the humidity low). I believe both these options were discussed in a Mission Impossible film, or similar (although they didn't use mud but a special foam suit) - for the reasons I've stated, they went with the heating up the room option. --Tango (talk) 23:28, 21 April 2009 (UTC)
(after edit conflict) Thinking about it, the movie is set in the jungles of Central America, so the ambient temperature is going to be pretty high anyway. Slap on some thick wet mud to bring down your own surface temperature and it might work for a time (as you say). The black ops guys in Predator 2 used insulated foil suits when attempting to capture the creature. IIRC, they were tethered by hose to some sort of central refrigeration unit. --Kurt Shaped Box (talk) 23:57, 21 April 2009 (UTC)
The Pierce Brosnan remake of the Thomas Crown Affair used exactly this method of increasing ambient air temperature to "blind" the thermal cameras in the art museum. :-) (talk) 23:51, 21 April 2009 (UTC)
Yeah - but that's fiction - so we may safely ignore it. OTOH - the Mythbusters tried a whole bunch of ways to get past thermal sensing alarms and found that a white bed-sheet held up in front of you was entirely effective (and a darned sight less messy!). Evidently, something that's highly reflective of IR energy allows your body heat to be reflected back away from the camera. SteveBaker (talk) 00:35, 22 April 2009 (UTC)
Sneakers used this trick as well. -- KathrynLybarger (talk) 04:16, 22 April 2009 (UTC)
Even if it is effective, what about Schwarzenegger's eyes? He doesn't put mud over his eyes (for obvious reasons), but shouldn't the preditor been able to detect the heat coming from his eyes? A Quest For Knowledge (talk) 00:44, 22 April 2009 (UTC)
Insufficient resolution on his HUD perhaps? I don't recall him being stood particularly close to Arnold in that scene. A lot of the Predators' gear seems to have technical limitations (e.g. a cloaking device that provides less than perfect invisibility when moving and malfunctions when wet, or an auto-tracking plasma cannon that struggles to acquire an accurate lock on a moving target). Or maybe he was looking for and expecting a human-sized heat source? Not finding one and dismissing the notion that a human could be smart enough to figure out the limitations of his thermal imaging (the mud thing was a lucky accident anyway), maybe he just figured that Dutch had somehow given him the slip and run off before he got there? --Kurt Shaped Box (talk) 01:23, 22 April 2009 (UTC)

Military anti-thermal-detection suit[edit]

This Q inspired me to ask one I've had on my mind. Is there a suit that could be designed to fool a thermal detection camera, over long time periods (many hours) ? I'm going to assume that heating up the environment to body temp isn't an option here, and neither is holding a sheet in front of yourself. Here's a couple of thoughts I had to overcome the build-up of heat problem:

1) Have the suit carry a coolant to fight the build-up of heat. This could be a very simple design, with inside pockets holding the coolant close to the body, and thermal insulation on the outside of the suit. No circulation system would be needed. When the solider returns to base, he could replace the warm coolant packs with cold ones. The trick would be a finding a light-weight coolant which has a high thermal capacity.

2) Have the suit heat some liquid, such as water, then inject it far enough underground to hide the thermal trace. A large downward pointing needle could be affixed to the calf of the soldier, which would periodically inject the hot water into the ground. This would only work on soft terrain. Alternatively, the soldier could dump warm water on the ground when he judges himself to be safe from thermal cameras. If a source of cold water is available (river or lake), then a tank of cooling water could be loaded up inside the suit and the warm water released into the river or lake periodically. Such a suit would require a circulation system, but it might be possible to install one-way valves such that normal body movements would circulate the fluid.

So, are any of these plans feasible ? How long could they last between recharges ? StuRat (talk) 15:04, 22 April 2009 (UTC)

There are a few tricky bits to get around. How to cover the face and hands without limiting maneuverability or limiting vision comes to mind. Also, The suit could not limit hearing or be noisy to use (crinkly aluminum sheets for example). Weight of course could be an issue. The more coolant you can carry, the more weight, but the longer the suit can go before a recharge. I don't think the needle idea would work because it would probably get broken while moving around, or else it might make you trip. Maybe it could be retracted or something. It is really going to depend on what you are doing while wearing the suit. If you are just standing in 1 place, it should be fairly easy. If you are in a special ops unit of the military, then it would be a lot harder to design. (talk) 15:19, 22 April 2009 (UTC)
Yes, the idea is that the needle would retract alongside the calf when not in use. StuRat (talk) 19:31, 22 April 2009 (UTC)
You're want to make sure that you didn't show up as a mysterious cool spot. The Predator would figure that out pretty quickly. APL (talk) 15:59, 22 April 2009 (UTC)
Yes, that's why insulation would be needed outside the coolant packs. StuRat (talk) 19:31, 22 April 2009 (UTC)
For military use - it's a lot harder. To fool a sensor, you only have to fool the kinda crappy image processing system that's hooked up to a cheap camera and saying something like: "If you see heat above 80 degF covering more than 10% of your pixels - ring the alarm". To fool human eyes (albeit looking through an infra-red camera or night vision goggles) is vastly harder. Having cool-packs isn't enough - you'd have to spread the body heat out uniformly - but you're still blocking the heat from whatever is behind you. When you look through night vision goggles, you see all the details of the trees and the grass and the road and vehicles, etc - and a human-shaped blob of any temperature whatever will look like a guy in a suit trying not to be notice! It's the EXACT same problem as trying to be invisible in daylight - you can't just be black or grey or the exact same AVERAGE color/temperature as the rest of your environment - you actually have to be an exact match for your environment - as seen from the point of view of the observer. Having said that, there are people who are trying to figure out how to make invisibility 'cloaks' - and if they ever succeed, then whatever they do will probably work perfectly well for IR imaging too...and of course you could merely seek to 'break up the shape' using camoflage techniques (but in the IR domain) and have some improvement. But as far as I know, this isn't a serious issue for the military right now. Most of the people that 'modern' armies are fighting are using techniques from 50 years ago - and they don't typically have night vision so going to a lot of trouble to hide from night vision devices isn't a huge deal right now. SteveBaker (talk) 19:37, 22 April 2009 (UTC)
Well, you'd still expect the special ops soldiers to keep hidden behind trees, in ditches, etc. However, if they are glowing brightly in infrared, that won't be enough. But, using an IR-suppression suit, in combination with standard stealth techniques, they should be able to avoid detection. As for "the enemy" not having IR scopes, they are cheap enough now that the military should consider them to be available to the terrorists. StuRat (talk) 03:15, 23 April 2009 (UTC)
You could try something like a thermocouple, which would cool the body by using the heat difference between it and the outside world to generate electricity which could then by used to power your equipment, or just dissipated in some invisible way. Done correctly, this could give you a suit that allows you to control the temperature at different points on the outside allowing you to create an IR version of the standard camouflage pattern. You would probably want something that can be adjusted depending on the time of day, ambient temperature, terrain etc. (you might have some of the suit the temperature of the sky and some the temperature of the trees, for example). --Tango (talk) 19:48, 22 April 2009 (UTC)
You could restrict your operations to times when the ambient temperature is close to human body temperature. Another option would be to breed a race of reptillian soldiers who radiate very little heat when at rest. A much cheaper option would be to cover your whole body with some very absorbent clothing, and continually douse yourself with water at ambient temperature, to keep yourself sopping wet. The surface of the clothing should equilibrate to something close to the dew point temperature, and if everything around you was similarly wet, you might not stand out. If you were in a very dry environment, such that the dew point temperature was well below the ambient temperature, this might not work well because you might appear as being too cool. Incidentally, Russian snipers in WWII in winter would put snow in their mouths so they would not give away their positions by exhaling vapor clouds. You may remember seeing that in Enemy at the Gates. --Teratornis (talk) 23:46, 24 April 2009 (UTC)

Gaussian random motion[edit]

What is a Gaussian random motion? The term appears as a description of a type of stimulus in oculomotor research130.194.208.63 (talk) 01:06, 22 April 2009 (UTC)

Perhaps a Wiener process? The increments of that are Gaussian. Algebraist 01:10, 22 April 2009 (UTC)
Gaussian random motion occurs when the probability distribution of the displacement between now and any later time is Gaussian. It basically means completely random motion: if you take an object that in every time increment moves a random amount in a randomly chosen direction, as long as the time increments are short enough the motion closely approximates a Gaussian random motion. It is, for example, a useful model of the movement of molecules in a gas. Looie496 (talk) 04:08, 22 April 2009 (UTC)
And yes, it is the same things as a Wiener process, but that article can probably only be understood by mathematicians. Looie496 (talk) 04:12, 22 April 2009 (UTC)

Lewis dot and cross diagrams[edit]

How do dot diagrams with little crosses or x's in place of some of the dots work? I see this in some diagrams and I'm not entirely sure what it means. (talk) 04:32, 22 April 2009 (UTC)

Are you referring to Lewis structures? Wisdom89 (T / C) 04:49, 22 April 2009 (UTC)

I am, yes. I can't find anything on that page, but I've seen where some of the dots are replaced with crosses. What does this mean? —Preceding unsigned comment added by (talk) 04:56, 22 April 2009 (UTC)

Do you mean all of the dots are replaced by crosses/plus signs, or a mixture? If it's the former, that's just stylistic - if not, the only time I've seen + signs is in relation to the valence of an ion. Wisdom89 (T / C) 05:01, 22 April 2009 (UTC)
Also, I think sometimes people write one element with dots, and the other with x's Wisdom89 (T / C) 05:05, 22 April 2009 (UTC)
You might want to try these links [9] and [10]. Wisdom89 (T / C) 05:09, 22 April 2009 (UTC)
The dot-and-cross diagram is a variation on the Lewis diagram that shows the electrons shared within each covalent bond. Dots and crosses are used to distinguish electrons donated by one atom from those donated by the other atom in the bond - electrons in the outer shell of one atom are shown by crosses, electrons in the outer shell of the other atom are shown by dots. In a normal covalent there will be one electron from each atom, so this is represented by a dot and a cross. In a dative covalent bond both electrons come from the same atom, so this is represented by two dots (or two crosses). You can see some examples of dot-and-cross diagrams on this BBC Bitesize page. Gandalf61 (talk) 10:52, 22 April 2009 (UTC)

Bruce Lee martial arts glowing light energy field[edit]

Perhaps more pseudo-science than science, but the science page is where are the smart geeky people are, is my question... There is a(n apocryphal) tale that Bruce Lee had attained such an advanced level in his Martial Arts practice that at certain times he emitted a (green) glowing aura / energy field around his body. Does anyone know what this field is purportedly called or has anyone heard this story? I already looked at Tummo. Merci d'avance, Saudade7 04:50, 22 April 2009 (UTC)

Oddly enough, people who believe in this call it an aura: see aura (paranormal). --Anonymous, 05:00 UTC, April 22, 2009.
Yes, but this is something else...people who believe in Auras believe that everyone has one. But this is a special field of glowing energy that only envelopes certain high-level martial arts practitioners when they are in the zone / at the top of their game / about to kick ass. Apparently Bruce Lee had it. I found the name on the Internet 10 years or so ago, (I feel like it was a Chinese-sounding word) but now everything I Google turns up yoga stuff. I feel like BL's field was said to be green. Thanks Saudade7 06:12, 22 April 2009 (UTC)
Well, there was a movie called The Last Dragon in which the main character was inspired by Bruce Lee to attain an ability called "The Glow" which is essentially what you're describing, but this is fiction of course, no one in their right mind would believe it was based on something Bruce Lee could actually do. Truthforitsownsake (talk) 12:35, 22 April 2009 (UTC)
It's all just fantasy of course, but for some related fantasy you can look at Kirlian photography. Looie496 (talk) 18:44, 22 April 2009 (UTC)
Are you talking about qi (ki in Japanese)? It looks like this. Those fighting-game energy blasts are made of concentrated ki. -- BenRG (talk) 21:23, 22 April 2009 (UTC)
There is an awful lot of bullshit pseudo-science relating to auras. However, no properly designed experiment has ever shown that they exist - and since a ton of laws of physics would have to be overturned if they really DID exist, we have to employ Occam's Razor and say that since extraordinary claims (which aura's are) require extraordinary evidence (and we have ZERO evidence) - then we should simply say that they are bullshit and move on. Which is what I'm going to do now. SteveBaker (talk) 19:25, 22 April 2009 (UTC)
Additionally, there's also an awful lot of bullshit pseudo-science relating to martial arts. I have, among other things, had a conversation with someone who seriously insisted that the Five Point Palm Exploding Heart Technique from Kill Bill -- with which you can make someone's heart explode by poking them five times in just the right spots -- was a real thing. Like a lot of superstition and many urban legends in general, the fact that there are no credible demonstrations of incredible abilities like this doesn't seem to slow the people who believe in this crap down at all. (I have been told, on different occasions, that it's a secret, because the great martial arts masters don't want the governments to find out about these powers, or that the government doesn't want people to learn about their tools of control, or that only a very few enlightened people attain this knowledge -- which presumably explains why every other semi-literate martial arts fanatic on the internet knows these things for a fact....) -- Captain Disdain (talk) 22:42, 23 April 2009 (UTC)
Hi everyone, Thanks for all your help. I guess I am going to run with BenRG's suggestion of Qi and Truthforitsownsake's reference for "The Glow" ! I'm really sorry if the question made the skeptical community angry. Notice that I prefaced the whole question with the word "Pseudoscience" and used "apocryphal" and "purported" and "said to be" throughout ! I was clearly trying to mark it as specious. I think the skeptics on Wikipedia are a bit too reactionary sometimes - like that woman on "The Skeptics Guide to the Universe" who seems always to be in attack mode. I wonder if the question, "What's that (more cryptozoological that zoological) animal called that is a horse with a horn?" would have gotten an angry rant about people that believe in non-existent animals rather than just the word "Unicorn". Just because some things don't exist in the world as empirical, sensible, material, testable, verifiable things does not mean they do not exist as conventionally agreed upon abstract concepts and entities in the cultural field. Sometimes these abstract concepts are said to be objects in the realm of science - like auras and kryptonite and warp drives. Know your audience! Hell, I gave Stevebaker a barnstar once! Thanks again! Saudade7 18:08, 25 April 2009 (UTC)
Well, I wasn't really directly speaking to you; I was just making a general observation about the topic at hand. I should perhaps have added a disclaimer. -- Captain Disdain (talk) 21:01, 25 April 2009 (UTC)


I would like to add if i may that i do not have a great understanding or math and mistakenly as was pointed out asked if there was an equation that fits the model...Equation is the wrong word please ignore that but i would like a good solid answer.

I was bored sitting in work and a colleauge said look up Schrödinger's cat.... While reading it...... it seemed as if the only way to explain Quantum mechanics is "the end product of any situation is allready predetermined"; applying this to the riddle, as far as i see it would explain the answer to the Schrödinger's cat experiment...the cat is either pre destined to be dead or alive this was pre determined right back to the big bang hence all future things are all ready predestined....(god knows what that makes to a time theory?) For example we know the Sun will burn out but it hasnt happened yet' its fule will be used up it will swell then cool ECT....this is all ready predetermined.So my question is if the universe surrounding us is all ready played out and the end states are known (but not by the human race) is there an equation that would fit this model? Ok i dont want you to look at this and think this guy is a nutter 'which i am sure you will' but it makes sense to me....we just need to be able to see the future is all :) Adrian O'Brien —Preceding unsigned comment added by (talk) 12:29, 21 April 2009 (UTC) I'm not sure but I think there is. Even if there is, the equation has to be really complicated. Also, I recommend you on posting this question on the science reference desk instead. Superwj5 (talk) 13:18, 21 April 2009 (UTC) It is nice that you are interested in this - I suggest you read the article Quantum mechanics. Especially, it is recommended that you read the "overview" section and the beginning of the introduction. Just read what you understand and ignore what you don't. The other thing I wish to comment upon is your belief that mathematics is described by "equations". This is false. Group theory does indeed apply in quantam mechanics as well as probability theory, and the deep purpose of either subject has nothing to do with equations. Just let me stress that mathematics is not equations. If you are referring to the uncertainty principle, then:

Also, I recommend that you read Introduction to quantum mechanics first as this is (apparently) more accessible. I do not wish to discourage you from asking questions but I just wish to stress the mathematics that applies to theoretical physics is much deeper than you think (for example the application of knot theory (a branch of mathematics) to string theory (a branch of physics)). --Point-set topologist (talk) 14:14, 21 April 2009 (UTC) All equations including mistaken ones fit the OP's notion of predetermination. It made me post this. Cuddlyable3 (talk) 14:25, 21 April 2009 (UTC) I was under the impression that it was classical mechanics that deals with a deterministic world, while quantum mechanics deals with a probabilistic one. What I mean to say is that if the position and momentum of every particle in the world were known at one instant, the state of the universe at any future instant is easily obtained by applying Hamilton's (or Lagrange's) equations. However in quantum mechanics it is intrinsically impossible to know the position and momentum of even one particle to arbitrary precision, let alone all of them. I would disagree with the OP's statement that the end result of any situation is predetermined, as we can only state the probability of obtaining any particular end. mislih 23:08, 21 April 2009 (UTC) —Preceding unsigned comment added by (talk)

Please use the proper, above-outlined method to post things instead of adding on to other people's questions. Then there will be no conflict. Saudade7 06:12, 22 April 2009 (UTC)
Nope, there is no predetermination. See Bell's theorem and Bell test experiments. Unobserved measures truly don't exist yet. You see, the trick is to just dispell your classical notion that a particle must have a single unique position and velocity at any given time. In the real world, a particle simultaneously occupies many positions, with a probability of being found at any given one upon being observed (whatever "observed" means). Although, of course, the Schrodinger cat has any number of issues, which I'm sure further responders will nitpick. Someguy1221 (talk) 06:16, 22 April 2009 (UTC)

Ok Saudade7 this was my question from the maths portal i just pasted the same question on here so there is no conflict. The part of your answer if i may i struggle with is, we may not know what the predetermined out come is, or be able to see it but this does not mean it doesnt have one...push a rock off the cliff it will hit the floor this is predetermined even if it hasnt hit the floor yet...If the rock is in many diffrent places at the same time we still know at that place it will hit the floor. there can be many variables i.e. somebody catches the rock ect... but that could be a predetermination somebody was always going to catch the rock if you see what i mean? Please excuse my lack of knowledge of science and math but i am trying to understand:)As i see it probability rather than predetermination seems to fit but the particle/rock/cat is allready doing what it was predestined to do we just dont no it.... —Preceding unsigned comment added by (talk) 06:39, 22 April 2009 (UTC)

Your idea that everything is predetermined, was, indeed, believed by scientists hundreds of years. This comes from classical mechanics, or common sense, and nobody dared to question it. Then in the last hundred years or so, great reforms began to occur based on experiments and sheer brilliance, culminating in Quantum Mechanics. At the heart of Quantum Mechanics lies the uncertainty principle. According to this outrageous fact, we can NOT even measure things around us as we like. There is always an uncertainty in measurement, inherent in the system. This has nothing to do with the faults of our measuring apparatus. For example, it may be possible to measure the length of a block of wood with a scale say down to an error of 1 mm. If we have an even better scale( say a vernier caliper) we might be able to measure it more accurately, say to .01mm. In PRINCIPLE, it is possible to measure with as much accuracy as we want, though it may not be practical. But in the realm of Quanto, there are fundamental restrictions even in principle. What's more, you the the length of a block is say 1 meter, whether or not you measure it, ie it is deterministic - already determined. The whole idea of determinism is gone in Quanto. Before the act of measurement, everything is just in a confused superposed state. The act of measurement forces it to take a value, which is then approximately measured. This might need some rereading and might be outrageous at first sight, but that is the way nature behaves. So if we assume Quanto uncle to be right, then determinism is just chucked out the window.... Rkr1991 (talk) 07:34, 22 April 2009 (UTC) —Preceding unsigned comment added by Rkr1991 (talkcontribs) 07:30, 22 April 2009 (UTC)
I meant you should have begun the process of asking your question by clicking on the "ask a new question by clicking here" link at the top of the page, rather than coming down here to the bottom of the page, clicking on the edit, and adding your question. It is just a simple a courtesy to others, like myself, who might be posting in a situation with sketchy Internet connection (I was at a cafe and needed to pirate an intermittent open signal). I had to wait for a new signal to re-post because your post time conflicted with mine as a result of your method. So I was cranky. The math portal has nothing whatsoever to do with the conflict. Saudade7 07:53, 22 April

\2009 (UTC)

Ok thats great thanks for the answers makes a lot more sense now, ill come forward 100 years and try to catch up :) just like to add some great minds on here brilliant to see. Keep it up :) NP's Saud i was on my third coffee :)

It may be surprizing to some people to realize that quantum mechanics, despite the uncertaity principle, is actually just as deterministic as classical mechanics, except for the wave function collapse that happens when an observation is performed. This is somewhat contradictory and to this day there is still some debate about whether the colapse is a fundamental phenomenon or just an epiphenomenon of quantum decoherence. The latter is considered more self-consistent and leads to an entirely deterministic theory. Dauto (talk) 14:53, 22 April 2009 (UTC)
I am no expert in QM, but I do use it on a regular basis. I have attended seminars by people researching entanglement as related to quantum computing, and while I cannot recall the exact arguments used the idea was put forth that either locality or causality can be preserved but not both. Is this related to your comment Dauto? By this I mean can we formulate a quantum theory in which the results of experiments is predetermined by initial conditions if we are willing to sacrifice locality (and accept "spooky action at a distance")? mislih 00:00, 24 April 2009 (UTC)
Spooky action at a distance is unavoidable in quantum mechanics. EPR paradox and Bell's theorem are good articles to read about that. But that action at a distance cannot be used to send information faster than the speed of light and causality is safegarded. All that is true independently of wheather the colapse of the wavefunction is considered to be deterministic or not. Dauto (talk) 04:53, 24 April 2009 (UTC)

Ok; Just so i am clear A>B>C... Taken we do not no the action of something in Quatum Mechanics of say some type of particle but to say its path is not a predetermined path i feel is wrong. we can only say at are present understanding we do not know what that predetermination is or if it has one, we can theorise an answer so it fits with our understanding or our calculations but in the end we just dont know. It very well might be the case that all things have a predetermined path/outcome. which just dont have that ability of understanding YET. for example the world was thought to be flat at one point mathamaticians and scientist's would have provided evidence at the time to prove that; the best answer is the one that says at are PRESENT understanding it appears that there is no predetermination however that could be in-correct...Chromagnum (talk) 13:17, 27 April 2009 (UTC)