Wikipedia:Reference desk/Archives/Science/2009 February 11

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February 11

Magnetic perpetual machine

This is an idea for a perpetual machine, and it sounds theoretically plausible. Have two giant magnets placed high above the ground, with opposite poles pointing a common center. The magnets are fastened to the ground so they don't attract each other. In the gap between the magnets, have a horizontal magnetic rod. It's supported in such a way that it can rotate due to repelling/attracting interaction with the surrounding magnets. I would think the rod's rotation could go on forever...199.76.164.202 (talk) 03:58, 11 February 2009 (UTC)

The rotating rod will eventually slow down and stop due to friction and air resistance. - Eron^Talk 04:04, 11 February 2009 (UTC)

You are confusing different concepts. Lets say you do your experiment inside a vacuum chamber to eliminate friction. Lets say you succede and your rod keeps on spining for ever. It still wouldn't be a perpetual machine just as the Earth spinning around itself in space isn't a perpetual machine. —Preceding unsigned comment added by Dauto (talk • contribs) 04:15, 11 February 2009 (UTC)

I assume the arrangement is as follows, based on your explanation:

N           S
N           S
N           S
N 1rodXrod2 S
N           S
N           S
N           S

where N and S are the two suspended magnets' north and south poles respectively, and the rod (with ends labeled 1 and 2) pivots about X. Let's say the rod is pointing at the two magnets as in the diagram: you propose that one magnet will pull the "far end" towards it (N magnet pulls rod end 2), but doing so involves pulling that end away from the magnet it's near (S magnet). Magnetism weakens with distance, so you're requiring that a further (and therefore weaker) field will pull that end away from the closer (and therefore stronger) one. Nope. Okay, let's say the rod is parallel to the two magnet faces (rotated 90° about X in the diagram). Now each end of the rod is equally attracted to each magnet, so it just sits there motionless. Let's say the rod is actually a magnet, with end 1 North and end 2 South. That will quickly rotate away from the above diagram and stick with the rod rotated 180° (rod end 1 North pointing at South magnet, etc) and stay there.

What you really need is a way to change the magnetic properties of the external field and/or the rod (as a magnet) over time. If you can get the rod ends to continually reverse their N/S identities, or have a constant rod magnet and keep swapping the external poles, you will get rotation. The rod will move to make its poles as attracted to the external magnets, but then either the rod or the external magnets change identies, which makes the rod swing back the other way. And so on. Unfortunately, that takes some energy (either physically moving some permanent magnets around or alternating an electric current in some electromagnets, but it's doable. Not quite perpetual motion though, but fun to experiment with. You can buy "electric motors" in many hobby stores. DMacks (talk) 04:18, 11 February 2009 (UTC)

The question makes no sense. Having two magnets "fixed to the ground" with opposite poles facing each other in no way lessens the attraction of the poles. Their height from the ground is likewise irrelevant. Edison (talk) 06:10, 11 February 2009 (UTC)

Er, I think the point is that the two magnets do not physically move towards each other. Axl ¤ [Talk] 10:26, 11 February 2009 (UTC)

Unless you can extract usable energy from it, it isn't a perpetual motion machine. Any machine will keep moving if there is nothing to stop it (that's one of Newton's laws). --Tango (talk) 13:51, 11 February 2009 (UTC)

To explain what Tango just aluded to, the problem is not creating "perpetual motion" (i.e. movement that will happen forever), its creating a "perpetual motion machine", that is something that will do useful work forever. There are any number of ways to set something in motion essentially forever. However, in order to be an effective machine, you would need a way to use that motion to power something else. Any attempt at extracting energy for another application from your perpetual motion device will either slow it down, or require you to add energy to it to keep it going, thus negating its perpetual motion. --Jayron32.talk.contribs 20:18, 11 February 2009 (UTC)

Thanks for the answers everyone. 128.163.80.152 (talk) 18:13, 12 February 2009 (UTC)

how to make a magnet

hey people- im in the 6th grade and in the science fair anyone know how to make a magnet???? i am gonna try making a magnet then proving points of the north and south poles of it. any help???? —Preceding unsigned comment added by 76.112.80.95 (talk) 23:28, 10 February 2009 (UTC) Copied from Talk:Magnet - Eldereft (cont.) 05:06, 11 February 2009 (UTC)

No homework or science fair questions, but I'll give you a hint: dry cell + iron rod + wires = Electromagnet. B00P (talk) 05:48, 11 February 2009 (UTC)

Bleh, it's trivial to find directions for making a magnet and the 6th grader would still need to make it, so I see no problem in explaining how. Dragons flight (talk) 05:52, 11 February 2009 (UTC)

You can make an electromagnet by winding a wire around a piece of iron many, many times and connecting it to a battery. When I was a kid we used to do this with iron nail(s), speaker wire, and a 9v lantern battery, all things available for cheap at any hardware store. Take a thick nail (or nails) wrap in wire from end to end several layers thick and connect the battery. Do it right and you'll be able to lift paper clips and other small objects. Make sure the nails are iron though, aluminum nails would be worthless for this. Dragons flight (talk) 05:52, 11 February 2009 (UTC)

Some ways to make a permanent magnet: 1) Take a piece of steel, like a needle or other iron/steel object and stroke it several times with a strong magnet. 2) make a solenoid with a great many turns of insulated wire. Place a piece of steel in it. Pass a large DC current (like from a 6 volt lantern battery) through it. 3) Do 1 or 2, but use a compound such as Alnico or Neodymium which makes a powerful magnet. 3) Align a piece of iron or steel with the Earth's magnetic field. This field varies with longitude and latitude, in both the horizontal and vertical dimensions.A dipping needle and magnetic compass can be used to determine the best orientation. Tap the piece of ferrous (iron) material hard and it will become magnetzed. Note that there is a health hazard with powerful magnets: If someone swallows two powerful magnets, they may trap a section of gut leading to Peritonitis and death (Who would swallow one, let alone two magnets?) Edison (talk) 06:01, 11 February 2009 (UTC)

Edison, we don't give medical advice here. ;-) Axl ¤ [Talk] 10:29, 11 February 2009 (UTC)

The magnet article doesn't have as much as it should about this. The easiest way to magnetize a long straight piece of iron, like a nail, is to repeatedly stroke it along the pole of another magnet. The strokes should always be in the same direction. The end of the bar that last leaves the magnet during a stroke should develop the opposite pole as the magnet pole.

This can only create a rather weak magnet. To create a stronger magnet, a bar of iron can be heated, placed between the poles of a magnet, allowed to cool in that position, and hammered as it cools. It works best to heat the iron to its Curie temperature of 1418° F (770° C), which is red hot, but lower heats also work The end of the bar toward the magnet's North pole will become a South pole, and the end of the bar near the magnet's South pole will become a North pole.

The strong permanent magnets you can buy are made of special types of metal alloys such as alnico, ferrite, or neodymium and are made by melting the metal and allowing it to harden between the poles of a strong magnet, and while it is still soft stretching it or rolling it like bread dough in the direction of the magnet's poles. Good luck with your project. --Chetvorno^TALK 07:12, 11 February 2009 (UTC)

Be careful with making electromagnets. If you don't make enough windings of the wire around the metal core, you'll effectively be short-circuiting the battery. You need really fine, insulated wire and you should be thinking of hundreds of times wrapped around the core - not (say) a dozen or so. If you do short it out - then depending on the type of battery that can heat it up enough that the contents boil and then explode. If you hook up your electromagnet and feel that the battery is starting to get warm - disconnect it immediately. By far the simplest way for a 6th grader to make a magnet is to take something SMALL like a pin or a needle and just stroke it from one end to the other (don't rub it back and forth - start at (say) the eye of the needle - stroke the magnet down to the pointy tip - then lift the magnet away from the needle and start the next stroke next to the 'eye'. It shouldn't take many strokes to make a magnet strong enough to use as a compass needle. The best way to do that is to stick the needle through a 1/2" slice of a wine-bottle cork and float it in a small amount of water. SteveBaker (talk) 21:44, 11 February 2009 (UTC)

Doesn't the magnetization take place pretty quickly? I would expect that once the current reaches its maximum you are about done. It should not be necessary to leave the current flowing long enough for the wire and battery to heat up, in order to magnetize a piece of steel (as opposed to making a piece of iron into an electromagnet). I agree with Steve that in winding an electromagnet it takes LOTS of turns (hundreds) to get enough wire in the circuit that it has resistance enough not to look like a short circuit to the battery. Edison (talk) 00:04, 12 February 2009 (UTC)

A medical emergency that could lead to a diagnosis of anemia

I am writing a story in which a character collapses and loses consciousness, and as a result of underlying conditions becomes diagnosed with, and is treated for, anemia. Having had some experience with medical jargon but not actually knowing very much about medicine (I'm an ESRD patient with anemia), I want to come up with something that is plausible and passes the acid test, so to speak. I don't know any doctors; I've spoken to a few people with medical knowledge and they've suggested things like severe tachycardia or some other heart emergency, but I'm not sure if anemia can actually cause any of these things. A little help? JuJube (talk) 05:15, 11 February 2009 (UTC)

Did you try your own link to anaemia, it seems to contain all the info you're asking for. Richard Avery (talk) 08:40, 11 February 2009 (UTC)

Here's 41 potential candidates. There's a few exotic oddities on there if you want a "House MD" type story. Fribbler (talk) 09:32, 11 February 2009 (UTC)

Except lupus...it's NEVER lupus. SteveBaker (talk) 20:12, 11 February 2009 (UTC)

And since it's never lupus, it's ok to use your lupus textbook as a place to stash drugs. Except one time it actually was lupus... -Pete5x5 (talk) 05:40, 12 February 2009 (UTC)

The most dramatic disease which causes the symptoms you describe, is Paroxysmal cold hemoglobinuria. It is a rare disease, which most often affects children, but young adults may also be affected. It is an autoimmune disease, which is triggered usually by a trivial viral infection. In the classical case, the auto-antibody reacts with the P antigen (which is present in at least 99% of the population). In a severe case, within a few hours, a large percentage of the patient's red blood cells may be lysed. This is of course a medical emergency, the patient will be severely ill, his serum will be brown due to free haemoglobin, and he will be febrile and possibly mentally affected (reduced consciousness, confusion, collapse). The disease may be fatal, but the autoimmune reaction itself is usually self-limiting, and the auto-antibodies tend to disappear within a couple of weeks. Regrettably, by that time the massive hemolysis may have permanently damaged the kidneys, and caused kidney failure. --NorwegianBlue ^talk 21:37, 11 February 2009 (UTC)

How does an anaemic ESRD sufferer not know any doctors? Surely you'd come into contact with plenty managing your illness. If not, you probably should! Mattopaedia (talk) 00:58, 13 February 2009 (UTC)

I know doctors; I just don't understand the terms they use, usually. And I don't think ESRD would lead to a medical emergency involving collapse and unconsciousness. I've been in situations where I couldn't breathe due to pulmonary edema, but the lack of consciousness wasn't sudden. x_x JuJube (talk) 07:52, 13 February 2009 (UTC)

Engine silencer

OK I'm just throwing ideas around and I'm a little bit over my head when it comes to modern engine technology, but I was wondering how feasible it would be, and what might be possible when it comes to quietening engines/fans, such as are used on the Skycar or other hover/flight machines. I've googled some information and been reading up on engine noise suppression, and I've come to the conclusion that active noise control is unfeasible unless you can somehow control exactly what kind of sound the machine makes. Would something like a mixer (engine) be possible on a hovercraft-like machine? I'm actually thinking of something more like an Avrocar, more a craft capable of hovering with stability at relative hights than a jet or a water-skirting hovercraft.

There is some discussion here about the same problem, though it doesn't seem that there is a solution. Another thing is clear is that there are four possible sources for noise: the motor driving a fan (if there is a fan), the parts of the fan itself, the turbulence at intake, and the turbulence at exhaust. The intake noise isn't an issue if the fan is part of the outside chassis (as with the Avrocar), and the exhaust turbulence can't really be avoided (unless a mixer can be used, but I'm not really sure how it works). The fan I guess would have to be aerodynamically shaped with incredible precision so as to eliminate drag, though that leaves the actual moving hub. The engine seems to be the biggest problem so that's why I've tried to limit this to a question about silencing engines!

So is there anything I've missed here? And does anyone know of anything else that can be done, or possibly an alternate way in which such a machine can be designed in order to reduce noise, or allow noise-reduction techniques? Thanks. 219.102.220.90 (talk) 05:36, 11 February 2009 (UTC)

I thought of an easier way to ask this question. How might one go about silencing an X-Jet? I haven't been able to find any video clips of it with sound, though I'm quite sure it's noisy given that it is powered by a special Williams [Williams F112|[WR19-9]] turbofan. 210.254.117.186 (talk) 13:03, 11 February 2009 (UTC)

Missile range

Recent news reports discuss Iran's launching of a satellite into orbit. They also discuss fears that "it could lead to the development of longer-range ballistic missiles" (The Economist 07Feb).

How does this work? If you can put something into orbit, doesn't it mean you can already shoot it all the way around the earth? How much longer range can you get? Wouldn't you already be able to fire a heavier payload to a shorter distance? Franamax (talk) 05:42, 11 February 2009 (UTC)

I'm far from an expert on these sort of things but it's worth remembering that getting something into space into some sort of orbital distance isn't actually a great distance. According to [1] the satellite in question is only orbiting at 155 miles+ which is the range of the missile used to launch it (as we would somewhat expect). Obviously that's largely straight up and requires you to achieve escape velocity, and other things so somewhat different from simply shooting a missile to travel inside the atmosphere to hit a target but it depends how far you mean I presume. For example, according to Intercontinental ballistic missile "the apogee (halfway the midcourse phase) is at an altitude of approximately 1,200 km". Clearly quite a big difference from what Iran has achieved. Beyond that, I presume there's quite a lot of additional complications like making sure it doesn't break up upon reentry and accurately hitting a target as well as achieving the elliptic orbit necessary in the first place. In theory I guess, once you've gotten something into orbit you could in theory deorbit it and attempt to hit a target, but it's not much use if it's easily destroyed, liable to breakup by itself, be rather imprecise and will take too long to reach your intended target Nil Einne (talk) 07:57, 11 February 2009 (UTC)

Those are some of the things that "development of ballistic missiles" consists of: first you have a device that gets to orbit, the next step is to give it deorbit capability, harden it against re-entry, and develop an accurate targeting system. That's what a ballistic missile needs to do, after all. 88.112.63.253 (talk) 08:32, 11 February 2009 (UTC)

The preceding is wrong in several ways, as noted below. No "de-orbiting" is necessary. See Ballistic missile. Edison (talk) 23:48, 11 February 2009 (UTC)

Just reaching an apogee of 1200 km is less than what Iran achieved; if you steer the rocket used for the orbital launch straight up, you reach more than 6000 km. Besides what 88.112.63.253 said you also have to think about the payload of the rocket (if you have only a primitive nuclear weapon, it might be too heavy for your rocket) and how much time one needs to prepare a launch (the time is generally shorter for solid rockets, but they have usually lower specific impulse, requiring a larger rocket for the same payload and "dry" weight fraction). Icek (talk) 08:48, 11 February 2009 (UTC)

Yes - my understanding is that their rocket put a four pound object into orbit. That object (if it had suitable retro-rocket thrusters) could be brought down anywhere along it's orbital path - and they could probably use a polar orbit to hit any location in the world. But with only a 4lb payload (minus retro-thrusters, minus radio gear and computer stuff, minus battery/solar panel) - that's not really enough. However, if you look at the power of the rocket needed to get a 4lb object into orbit - and imagine that with a non-orbital ballistic trajectory and with a small nuke on board - then the range would as stated. The slightly worrysome part is that this was a multi-stage rocket. Mastering multi-stage rocketry allows for the possibility of using (say) four rockets firing together as a first stage - with the second and third stages being as now. THAT might be enough to get a nuke in orbit. SteveBaker (talk) 19:52, 11 February 2009 (UTC)

The orbital height attainable is not at all the same as the range of a missile. The V-2 had a range of 320 km but could not put anything in orbit at all. It takes a more powerful engine to obtain a given orbital height than to deliver a payload to a point the same distance away on the ground. A missile which could place an object in orbit could deliver the object to the opposite side of the world.Per Ballistic missile it is not at all necessary to place the object in orbit and then fire a retro rocket to de-orbit and hit the target. The warhead is accelerated in the boost phase, then it just coasts in a sub-orbital ballistic path until it encounters the atmosphere and reenters. So if they could orbit a four pound object, they should be able to get a heavier object to the re-entry location. Edison (talk) 23:50, 11 February 2009 (UTC)

During our propulsion system testing, it was a common joke that to get to orbit, all you had to do was "turn left at the top", but of course this was totally ignoring the physics and engineering considerations... Nimur (talk) 09:15, 12 February 2009 (UTC)

Degree of Relatedness

What is the degree of relatedness between two children of an incestuous relationship between a half-sister and half-brother, I feel like it's 0.75, but I'm not, any ideas? 169.229.75.128 (talk) 07:11, 11 February 2009 (UTC)

The half-siblings have a degree of relatedness of 0.25, so from the unrelated 0.75 of the siblings the children have degree of relatedness of 0.375 (as they have a degree of relatedness of 0.5 for unrelated parents) and add to that the 0.25 -> the degree of relatedness is 0.625. Icek (talk) 08:52, 11 February 2009 (UTC)

IceK, why should relatedness be additive ? And more general: how did you come to the 0.375, and about what children/siblings are you talking in which part of your answer ? I did also some reading into the matter, and I'm at the moment totally confused because every article and every paper uses his own definition of "relatedness" or "incestness" or whatever. There is a famous method called "path counting", but I have at the moment found two different methods for it which arrive at different numbers for the same relationship... What a mess. A little help of a statistician and/or mathematician could be needed, as I am really curious now to know the proper calculation. TheMaster17 (talk) 09:23, 11 February 2009 (UTC)

Coefficient of relationship might help.76.97.245.5 (talk) 10:07, 11 February 2009 (UTC)

No, it doesn't help. By the way, it's in a really bad shape, concerning style and form. It even adresses the reader personally. And as I said: the definitions of relatedness differ even in publications, and in a way that I cannot make sense out of it. So a short, unscientific, badly written wikipedia article doesn't help, no. TheMaster17 (talk) 12:29, 11 February 2009 (UTC)

It's 0.125. According to the table in Coefficient of relationship, half-siblings have a degree of relatedness of 0.25. Each received 1/2 of their alleles from the shared parent and for each gene there would be a 1/2 chance of the same allele being transmitted. 1/2 * 1/2 = 1/4. Full siblings share 1/2 of their alleles, so the children of the consanguineous couple would likewise share 1/2 of their parents' alleles. 1/4 * 1/2 = 1/8. Thus, two children born to a half-brother and half-sister would share on average 1/8 of the alleles transmitted from the shared grandparent. --- Medical geneticist (talk) 15:57, 11 February 2009 (UTC)

I still have trouble quiet grasping this. So there are three generations here, right? The first has a woman, call her A, who married a man B and a man C. A and B had a female child D, and A and C had a male child E. Second generation then is the half-siblings D and E. Their degree of relationship (r) is 0.25. Then they have two children F and G, the third generation. The Coefficient of relationship page points out it's "assuming no consanguinity" in its calculations of r. Yet it does get into the issue of half-siblings, saying they have an r_m of 0.5 and an r_p of 0, since there is no chance of receiving alleles from their different fathers. The 0.5 and 0 average out to 0.25. But in the example here, where the half-siblings have children, wouldn't you want to track the r_p of the two first generation men, rather than just making them zero in the second generation? Sure, the half-sibling D has r=0 with C, and E has r=0 with B, but the grandchildren F and G have some degree of r with A, B, and C, right? Unless I'm confused (which is likely!), User Medical geneticist calculated the degree of relationship between the grandchildren F and G as 0.125 based on the chance of sharing alleles with grandmother A (um, I think--maybe I understood). But wouldn't they also have a chance of sharing alleles with both grandfathers B and C, unlike the half-siblings? Wouldn't that make the degree of relationship something higher than 0.125? Most likely I just don't quite grasp the way these calculations are done. Pfly (talk) 17:10, 11 February 2009 (UTC)

Another issue that arose in my calculations: The questions sounds to me as if the "base generation" of the calculation should be the cosanguine parents. As "normal" (so, not cosanguine) parents produce children with a relatedness of 0.5, I am sure that cosanguine parents must have children with a higher relatedness. But I'm unable to calculate this properly, and nothing I have read specifically mentions this problem and, more general, the problem of "shifting the base generation". And what is also puzzling me with the answer that Medical geneticist gave: He arrives at a relatedness of 1/8 for grandparents to grandchildren, while the article coefficient of relatedness gives 1/4 for non-cosanguine grandparents-grandchildren... How can a cosanguine line of descent have grandchildren which are less related ? Something must be wrong here. 132.252.149.100 (talk) 17:22, 11 February 2009 (UTC)

I looked through this page, which does the "path counting" thing. If I understood right, the grandchildren would each have four direct paths of descent. The grandmother having two paths through the two half-siblings. The linked page above says in calculating collateral relationship (the grandchildren to each other), "No individual must occur in the same path more than once." So, if I have it right, that would leave three descent paths, A->D->F, B->D->F, and C->E->F (using my letters above, and the same for grandchild G). The calculation is supposed to be the sum of (1/2)ⁿ, with n equal to the number of steps in the paths, in this case 2. So, each of the three paths would be (1/2)² = 1/4. And 1/4 + 1/4 + 1/4 = 3/4. So the degree of relationship between the grandchildren is 0.75? Again I am likely misunderstanding all this. Pfly (talk) 18:01, 11 February 2009 (UTC)

I also stumbled upon that "path-counting" thing, but wasn't able to do it properly. But for the value of 0.75: At least it's bigger than 0.5, which would be the relatedness of non-cosanguine sibblings, according to our article and some web pages. But I think as long as nobody shows up here who has experience with this kind of calculation (or we find a very neat page with understandable examples for cosanguines), we are not going to sort this out for ourselves, because we cannot distinguish which of the numbers is the "right" one. Any population geneticist who's good with numbers here ? TheMaster17 (talk) 19:21, 11 February 2009 (UTC)

Doh! The dangers of quick "back of the napkin" calculations... In my initial response I was trying to assess the proportion of alleles shared by the siblings. I took the 0.25 number from the table and multiplied by 1/2 to get 1/8, but this doesn't seem right. Others seem to be using a quite different calculation (the "path counting" thing) so we must be talking about very different things. Back to the drawing board! --- Medical geneticist (talk) 22:26, 11 February 2009 (UTC)

I agree with Icek's answer of 0.625. StuRat (talk) 22:32, 11 February 2009 (UTC)

Icek calculation is right (good explanation too). the answer is r=5/8=0.625. Medical geneticist also had correct reasoning but he forgot to add 1/2 (tha any regular brothers have in common) to the 1/8 that he calculated. 1/2+1/8=5/8. Dauto (talk) 02:23, 12 February 2009 (UTC)

This question was cross posted at the mathematics help desk, where I posted my answer of 9/16. As I seem to be in the minority in my opinion of the answer, I'll go ahead and explain my reasoning. The following is a sort of "brute force" approach to the problem... it is easier with a diagram (but I'm too lazy to scan it in).

Suppose you have grandparents A, B, C. A and B have child D, A and C have child E, and D and E have children F and G. Given a gene in F, we want the probability of that gene being present in G.

Half of D's genes come from B. 1/4 of D's genes come from A and are not present in E. 1/4 of D's genes come from A and are present in E.

Half of E's genes come from C. 1/4 of E's genes come from A are are not present in D. 1/4 of E's genes come from A and are present in D.

In F, we find: 1/4 of genes come from B then D (which I will denote: B->D). 1/8 from A->D are not present in E. 1/8 from A->D are present in E. 1/4 from C->E. 1/8 from A->E are not present in D. 1/8 from A->E are present in D.

So if we choose a random gene in F, then:

• 1/4 chance B->D, in which case 1/2 chance of being present in G.
• 1/4 chance C->E, in which case 1/2 chance of being present in G.
• 1/8 chance A->D, not present in E, in which case 1/2 chance of being present in G.
• 1/8 chance A->E, not present in D, in which case 1/2 chance of being present in G.
• 1/4 chance being present in both D and E, in which case 3/4 chance of being present in G.

Adding up the results, we find 9/16 chance of being present in G.

Eric. 06:48, 12 February 2009 (UTC) —Preceding unsigned comment added by 131.215.158.184 (talk)

Thank you Eric, this way I understand the answer and also the way you arrived at it. And even the question as you formulated it seems better to me: What is the chance of finding the same gene in both sibblings? Sometimes it's only a matter of getting the question clear. :-) "Degree of relatedness" is too abstract to have a clear meaning outside of context. I hope the OP is satisfied with this, but I really doubt he is still following, looking at the time it took for a result. TheMaster17 (talk) 10:41, 12 February 2009 (UTC)

The only problem with Erics explanation is the fact that it is wrong because it fails to take into consideration the increased homozigoteness of F and G (being the offspring of a partially incestuos couple). The degree of relatedness is intended of as a measurement of the likely homozigoteness of a possible offspring between two persons (neglecting gender and age barries that could make an offspring unlikely or impossible). From that point of view, two people with a higher then average homozigoteness (F and G) will have a higher degree of relatedness then they would have had we chosen to define relatednes simply as the likelyhood of sharing a randomly chosen gene (as Eric did). To be more specific, lets say that A,B,C, and D are different alleles for a gene. If two individuals share all their genes (identical twins), they could have for instance alleles (AB) and (AB) with only 50% chance of homozigoteness for a hypotetical offspring (forget about the fact that an offspring would be impossible). Homozigote twins would have alleles (AA) and (AA) and would be even more related to each other then normal twins. Unrelated individuals could have alleles (AB) and (CD) with 0% chance of homozigoteness of the offspring. Using a somewhat arbitrary normalization which assumes that unrelated individuos share no genes at all and are completely heterozigotes for simplicity, we get the following values for relatedness between all possible combinations: (AB)+(CD)->r=0, (AB)+(AC)->r=1/2, (AB)+(AB)->r=1, (AA)+(BC)->r=0, but also (and that's where Eric went wrong) (AA)+(AB)->r=1, (AA)+(BB)->r=0, and (AA)+(AA)->r=2. Take that into consideration and repeat Erics reasoning and you will get the slightly higher value of r=10/16=5/8 in average, which is the correct result originally obtained by Icek through much simpler methods. Dauto (talk) 19:16, 12 February 2009 (UTC)

I see. Now that I've read the article on coefficient of relationship I understand the definition of relatedness you describe. Under this definition the "3/4" in my table above should be changed to a "1", giving 5/8 as the answer. I won't hesitate to add that this definition is a bit counterintuitive, as the degree of relatedness of an individual with itself could be anywhere from 1 to 2, depending on the homozygoity of its genome; and in particular we must make assumptions about the homozygoity of the grandparents A, B, C before we can draw conclusions about the relatedness of F and G. But I can hardly complain if this is the accepted definition used in literature. (And I agree that it is easier to calculate than the definition I was using.) Eric. 131.215.158.184 (talk) 22:27, 12 February 2009 (UTC)

I agree that the definition as I used leads to degrees of relatedness larger then one. But that's the best (only?) way to take into consideration the possibility of homozygoity. Your other point about having to make assumptions about the grandparents is true, but we will always have to make assumptions (that they are not related for instance) about the grandparents, no matter what definition we chose for relatedness. —Preceding unsigned comment added by Dauto (talk • contribs) 00:45, 13 February 2009 (UTC)

It's not the greater-than-one I don't like (a number is a number whichever way), it's the variability from one individual to another: perhaps I am more closely related to myself than you are closely related to yourself. There is also the fact that the definition uses the (somewhat complicated) notion of alleles at a locus, and that the result of the calculation depends upon the diploidity of the genomes in question, and so will not hold in a species with slightly different inheritance rules. And although with either definition, we must assume that A, B, and C are unrelated to each other, with this definition we must additionally assume that A, B, and C have degree 1 relatedness to themselves -- an assumption that is not necessarily true and not easy to test for. But this is merely the mathematician within me being whiny about elegance (this is what happens when people leak over from the math reference desk): what really matters is which definition is more useful in real-life biology, and frankly the standard Sewall Wright's definition is more useful than the incorrect definition I was using. So oh well. Eric. 131.215.158.184 (talk) 04:22, 13 February 2009 (UTC)

(unindent) Eric, I would not generally assume that "the Sewall Wright's definition is more useful" in real biology. From my viewpoint as a human geneticist, I would say it rather clouds the real relationships. It's a neat tool to bring the concept of relatedness to students, but when you want to do real science, the topic gets more complicated than that. You have to account for exactly the things you mention and test for things like allele-sharing between "unrelated" people. Just imagine that for most loci, there is a rather small number of alleles in the wild, so even by picking say 10 strangers from a crowd, you would probably have very many loci with the same allele in the majority, but you would never call those people "related" in any common sense. This was what bothered me from the start: The numbers that the page coefficient of relationship gives are very hard to interpret. What do numbers of 0.5 and 1.0 really mean ? What does "double as related" mean ? What implicit definitions are put into the calculation ? So your stochastical approach was somewhat more "scientific", even when in reality one would have to consider other factors, too. But it would be possible to fit them all in your calculation scheme. TheMaster17 (talk) 11:08, 16 February 2009 (UTC)

Will Ultraviolet A or B rays kill the vibrio cholerae bacteria?

If you expose the cholerae bacteria to ultraviolet light (A and B)

- will it kill the baceteria? Thus will you be able to clean water for drinking purposes if you can expose it to these two electromagnetic rays.

- which one of the two will be more effective?

- what intensity of lightrays and for how long must the water be exposed to it for the bacteria to be killed?

Nuuskierig (talk) 11:15, 11 February 2009 (UTC)

This is obviously a homework question. I expect the answer is within a textbook in which your syllabus is based on. Please read up on ultraviolet germicidal irradiation for question 1. There is a useful table at Ultraviolet#Subtypes which should help in answering question 2. Question 3, I don't know. --Mark PEA (talk) 19:19, 11 February 2009 (UTC)

See Ultraviolet#Disinfecting drinking water. You may also find Ultraviolet#subtypes and Water absorption useful. For question 3 you can probably get some idea by looking up the operating parameters of commercially available ultraviolet water sterilizers. 152.16.144.213 (talk) 01:58, 12 February 2009 (UTC)

Was William Harvey realy the first person to describe blood circulation?

The entire Ayurvedic medicine is based on the foundation of blood circulation and I note that circulatory system is quite well described in Caraka samhita.(Ramanathan)

Other physicians, notably Ibn al-Nafis and Michael Servetus, had suggested the idea of the circulation of the blood before William Harvey. Harvey's contribution was to put the idea on a firm scientific footing, through experiment, vivisection and quantitative observations. Our article on Ayurveda talks about the role of "channels" - "tubes that exist within the body and transport fluids from one point to another" - but that seems a long way from an unequivocal description of a circulatory system. It seems equally consistent with the Galenic view (commonly held in Europe before Harvey) in which "venous blood was thought to originate in the liver and arterial blood in the heart; the blood flowed from those organs to all parts of the body where it was consumed". If you can point to a clear description of the circulatory system in the Charaka Samhita then please give more details, but remember that it is important not to let our interpretation of ancient texts be filtered and coloured by our modern scientific knowledge. Gandalf61 (talk) 13:05, 11 February 2009 (UTC)

The last bit about using modern interpretations filter our understanding is crucial here. The concept of circulation is not just that blood flows through the veins. That's pretty obvious if you've had a serious cut. Circulation discusses the role of the heart in distributing blood and managing its oxygenation in two closed loops (see systemic circulation and pulmonary circulation). That's a pretty specific claim about how the fluids move functionally and what their physiological significance is—not some vague notion of circulating blood (which, again, is obvious).

People often go very wrong in finding "precursors" first by misunderstanding what the key element of the "discovery" is (either through ignorance or because it has been overly simplified in modern discussions of it) or by reading into vague and poetic texts a specific scientific meaning that is only apparent if you already know what the final outcome is meant to be. (Similarly, vague notions of transmutation of species are not the same thing as a systematic discussion of how biological evolution works, and vague notions of inherited properties are not a systematic discussion of the mechanisms of genetics.) --98.217.14.211 (talk) 13:38, 11 February 2009 (UTC)

CIVIL ENGINEERING

I HAVE HEARD THAT THERE ARE CHEMICALS AVAILABLE WHICH CAN MAKE A LEAKING CEILING (MADE UP OF CEMENT AND CONCRETE) ABSOLUTELY WATER PROOF WHEN APPLIED FROM THE BOTTOM SIDE.

IS THIS SO?

IF YES, THAN WANT TO KNOW THE COMMERCIAL NAME.

ANY OTHER WAY TO PREVENT THE SAME PROBLEM? —Preceding unsigned comment added by Saurabh85 (talk • contribs) 12:36, 11 February 2009 (UTC)

That doesn't sound like a good idea, because the water will still be there, and it will accumulate within the ceiling. You have to figure out where the water is coming from and seal it off. --Milkbreath (talk) 12:54, 11 February 2009 (UTC)

Also consider:

• Water is 1 tonne per cubic metre.
• Damp / moist concrete will effect affect the thermal insulation properties.
• When the reinforcement rods have lost strength due to rust, the ceiling will just crash down.
• If the stuff freezes the entire structure is likely to disintegrate.
• Dampness will spread to the walls (supporting or not). --Cookatoo.ergo.ZooM (talk) 14:16, 11 February 2009 (UTC)

What you may have heard about was a primer like Kilz [2] or a waterproof paint like Perma-White [3]. Neither of these will counteract a leak. They are for treating the after effects of a leak i.e. water stains and mold/mildew. You'll have to fix the leak first. Then you can treat the ceiling from the bottom to prevent the damage from showing through. If it's the ceiling of a rental apartment and you are the tenant inform the apartment manager that it needs fixing. In a condo contact the owner above you. If it's your own house check your water, drain and heating pipes for leaks. (Plumber) If it's under a bathroom check the tiles and caulk around the tub or shower. See if your chimney may be sweating. Check your roof for leaks, particularly around plumbing vents, chimneys and skylights. Use a hose and see if you can re-create the leak on a dry day. (Better and safer: Get a roofer to do that. Make sure you use adequate safety measures when you do it yourself.) See if your gutters or downspouts have cracks or leaks. Check and seal places where wires enter your house. The water might be creeping in along those. Other possible causes: missing air gap in a brick wall above, faulty siding, improperly installed insulation, condensation. If you can't find and stop the leak, there are companies that specialize in leak detection and remedy. They cost a pretty penny, but beat having your ceiling cave in on you. Good luck. 76.97.245.5 (talk) 15:17, 11 February 2009 (UTC)

Depending on the thermal insulation (or the lack thereof) this may also be condensation. Poorly insulated concrete as you may find in garages and utility buildings may act as a "bridge" as the heat is dissipated to the outside.. The concrete slab may become quite cold and cause water vapour to condense on the surface. A pellet pallet of styrofoam panels may be all you need. --Cookatoo.ergo.ZooM (talk) 18:28, 11 February 2009 (UTC)

what happens in the fractioning column (in the lab) as ethanol-water mixture boils?

While carrying out fractional distillation, apparently. I'm reading something about a "ring of condensate" but I am unsure what this exactly looks like. What happens in the column when the ethanol-enriched vapor is boiling versus just the pure water? Or perhaps just at the inflection point? 199.111.188.130 (talk) 13:14, 11 February 2009 (UTC)

Not an answer to your question, but there was a thread here a while ago which may be of interest. See Phase diagrams for mixtures of ethanol and water.. --NorwegianBlue ^talk 21:48, 11 February 2009 (UTC)

Wireless invention;Bose or Marconi!

Does teh popular belief in India that it was Jagadis Chander Bose and not Marconi who should be credited with wireless invention carry currency with teh wiki community?(Ramanathan) —Preceding unsigned comment added by 212.247.70.129 (talk) 14:05, 11 February 2009 (UTC)

We have an article Invention of radio which discusses the contributions of Bose, Marconi and others. Algebraist 14:11, 11 February 2009 (UTC)

Our article List of persons considered father or mother of a field notes that Alexander Stepanovich Popov, Lee De Forest, Guglielmo Marconi, Jagdish Chandra Bose, and Nikola Tesla have all been credited as the inventor. Algebraist 14:14, 11 February 2009 (UTC)

De Forest as "inventor of radio" is absurd, since radio predated his work. Popov as "inventor of radio" is absurd since detecting lightning storms is far from "radio." Marconi took the inventions of others and used them to send signals effectively, so is plausible. Note that Thomas Edison demonstrated high frequency electromagnetic wave transmission and detection in 1875. He called it Etheric force and published his results. Scientists erroneously dismissed it as induction. David Hughes sent Morse code signals by electromagnetic waves in 1879, but his results were erroneously dismissed at the time as induction. Invention is usually an incremental process. Edison (talk) 23:38, 11 February 2009 (UTC)

"...Invention is usually an incremental process," ... and to ascribe credit to a single individual is always going to be based on a subjective evaluation of which innovation(s) were the crucial ones. Nimur (talk) 09:19, 12 February 2009 (UTC)

Migraines and Auras

Please note: I am not after medical advice, I know precisely what they are I am just shooting the breeze with some biologically-educated peoples on here

If one suffers from a Migraine with an Aura attached, is it feasible that one can intentionally recreate the mental sensations and visual hallucinations in ones mind from memory and thus re-trigger the aura and even the migraine?

Well, I know its feasible cause I can do it, but does anyone want to hypothesise with me as to how the biological side of it works? Again, this isn't medical advice, pure curiosity, I know the policy :)

Regards, SGGH ^ping! 15:18, 11 February 2009 (UTC)

Does aura (symptom) have any useful info about this ? My own thoughts are that, just as an epilepsy attack can be triggered by flashing lights of a certain frequency, which then send signals to the parts of the brain which cause the epilepsy malfunction, certain stimuli, either external or internal (thoughts), can also send signals into the parts of the brain which causes the migraine malfunction. I wonder if this could lead to a biofeedback-like way to prevent migraines, by not thinking of the things which trigger a migraine. Unfortunately, trying not to think of something often has the exact opposite effect. Perhaps there is something safer to think about (like the old relaxing brook). This would be consistent with typical advice for migraine sufferers to avoid stress. StuRat (talk) 15:32, 11 February 2009 (UTC)

The aura article unfortunately doesn't have too much on self-trigger. Interestingly enough, the trigger for one I had last night was the thought of someone taking 9/something in a cricket match!!! Weird. Sometimes I wish I could work out where these things come from, many of the hallucinations seem as if they are memories or something. It's odd to describe. SGGH ^ping! 15:43, 11 February 2009 (UTC)

Here's someone who could trigger his migraines by playing sports. Not quite the method you were thinking of. [4] Yet another Discover article. My memory seems to have a separate department for those:-) 76.97.245.5 (talk) 16:40, 11 February 2009 (UTC)

It seems someone who can trigger an aura by thought might be of value to a catscanner somewhere! SGGH ^ping! 20:16, 11 February 2009 (UTC)

You're not the only one to get a migraine at the thought of cricket: [5] Gwinva (talk) 00:12, 12 February 2009 (UTC)

Eyeglass prescription

I've just had an eye test and my prescription has a weird squiggle for the left spherical component. It looks like an infinity symbol, or possibly "cs" (written very quickly). From context, I would guess it means zero (it's certainly a fairly small number), but according to our article zero is usually written either "0.00" or "Pl". It almost looks like it says "05", but it certainly isn't 5 and some of the other values are a half and they are written very clearly as "0.50". Any ideas what it means? --Tango (talk) 15:45, 11 February 2009 (UTC)

I say, can you scan it for us to see, perhaps? It'd help a great lot. Cheers, Ouro (blah blah) 18:05, 11 February 2009 (UTC)

I might be able to tomorrow if necessary. --Tango (talk) 18:15, 11 February 2009 (UTC)

Well, I'm one who prefers to see what he needs to describe or elaborate upon rather than having to recreate it in thought, so it'd be better, but if someone helps you just based on your description then don't strain yourself, Tango. --Ouro (blah blah) 18:22, 11 February 2009 (UTC)

If no-one has answered by tomorrow afternoon (UTC), I should be able to go and scan it - there is a computer room with a scanner not too far away. --Tango (talk) 18:32, 11 February 2009 (UTC)

Until then, here is my attempt at tracing the symbol in MS Paint. It's not perfect, but it gives you a decent impression. File:Eyeprescription.JPG --Tango (talk) 18:37, 11 February 2009 (UTC)

Do you have a digital camera? If so, turn on the "Macro" setting and you should be able to get a decent photo of it. SteveBaker (talk) 19:30, 11 February 2009 (UTC)

Clever clogs... Alright, try this: --Tango (talk) 19:48, 11 February 2009 (UTC)

It absolutely looks like an infinity symbol to me, yeah. No idea if that means anything in opthalmology, but it seems fairly clear. ~ mazca ^t|c 20:15, 11 February 2009 (UTC)

If the ophthalmologist has diagnosed astigmatism this may refer to a lens with cylindrical chracteristics. --Cookatoo.ergo.ZooM (talk) 18:08, 11 February 2009 (UTC)

Yes, I have an astigmatism. There are three columns on the prescription, sphere, cylinder and axis (well, there's prism and base too, but they're blank). The symbol I'm talking about is in the sphere column. The cylindrical component is -0.50 with an axis of 180. I'm trying to work out what the spherical component is. --Tango (talk) 18:15, 11 February 2009 (UTC)

Call the doctor who wrote the prescription, and/or ask the optometrist who is going to make your eyeglasses (or sell you contact lenses). A bunch of invisible people on the internet are going to be less than helpful. --LarryMac | Talk 18:28, 11 February 2009 (UTC)

I have great faith in the ability of ref deskers to be helpful! If no-one has come up with an answer by the time my new glasses are ready to collect in a week or so, I'll ask while I'm there. --Tango (talk) 18:39, 11 February 2009 (UTC)

I guess we need some optical guru (which I am not). ∞ (and that is a capital ∞, for those who need spectacles!) dioptries on your left eye would mean a focal length of 0m, so I guess that your left eye does not require any correction by the spherical properties of the lens but is solely tweaked by the -0.50 dpt of the cylindrical focus. As the axis is given as 180deg, all the power is on the vertical axis and 0dpt are on the horizontal one. So the lens has to provide "distortion" in but one direction (as a cylinder does), which means that there is no "spherical property" required.

On the right eye, conversely, you have 175deg and require some correction on the horizontal axis, ergo a bit of "sphericity" of -0.25dpt is needed.

As stated above, somebody who knows more about optics than I should be able to give a better answer. --Cookatoo.ergo.ZooM (talk) 21:21, 11 February 2009 (UTC)

A focal length of 0m is not zero correction; it's infinite correction. Not physically realizable (at least in any way I can imagine) and would hardly be useful in eyeglasses anyway. But who knows; maybe for some reason optometrists write infinity when they mean zero (not necessarily totally irrational — maybe the infinity symbol is harder to misread, and of course it's not good for anything else anyway — obviously this is pure speculation on my part). --Trovatore (talk)

Yes, I was puzzled by that, too. As Trovatore, I assumed it to be some opthalmological standard. --Cookatoo.ergo.ZooM (talk) 22:12, 11 February 2009 (UTC)

These sites (and others) said it's used for "plano" or "flat" lenses [6] [7]. How you would get that to display the other two characteristics beats me, but I'm no optician either. 76.97.245.5 (talk) 23:42, 11 February 2009 (UTC)

Those sites describe a flat lens as having an infinite radius of curvature (which is true), but it seems odd that they would measure curved lenses in terms of power (in dioptres - metres^-1) and flat ones in terms of radius of curvature (a distance). Maybe opticians are just odd... --Tango (talk) 23:49, 11 February 2009 (UTC)

I found a UK commercial website, extreme-eyewear, that has a section explaining "your eyewear prescription". It says that "sphere can be one of three values" and that the first is "Zero (also written as 0.00, -, ‘left blank’, and the infinity sign: ∞)." To judge by that, each optometrist has his own way of expressing "no correction" for sphere, and one of them is the infinity sign that is obviously what's on your prescription there. A sphere of infinite radius has a plane suface, I guess, Euclid notwithstanding. --Milkbreath (talk) 00:33, 12 February 2009 (UTC)

Fantastic, well found! Thank you. --Tango (talk) 14:01, 12 February 2009 (UTC)

Checking that loading of wells in SDS PAGE is comparable or whatever

We want to do a western blot to check acetylation levels of histones in cell cultures treated differently. We want to find the percentage of acetylated histones relative to total histones. Thus our options inculde a) probe with antibody for acetylated histones, strip membrane of antibodoes and reprobe for all histones and b) pipette each sample into the gel twice, making a mirror image, cutting the resulting membrane in half and probing each half with the two different antibodies. I favour the stripping method but my supervisor favours the other method. I would like advise. Thanks in advance.

Your supervisor is probably right. Stripping is often hit-or-miss, and it's only something you want to get into if it can't be avoided. Incomplete stripping of the first primary antibody may give you an inappropriately weak signal when you reprobe. Overly-stringent stripping may lead to decreased overall signal or increased background. A side benefit of running parallel gels (or at least cutting the membrane in half) is that your total time from gel to results is shorter, since you can probe for both species at the same time.

One more thought — you and your supervisor may have already discussed this, but it's worth noting that the affinities of different antibodies can vary quite significantly. If you're trying to get actual percentage-acetylation numbers out of a (semi-)quantitative western, you're going to have to run a lot of standards in parallel with your experimental samples. The antibody for total histones may be more sensitive (for example) than the acetylated-histone antibody. In that case, even given 100% acetylation, the acetylated-histone signal would be weaker than the total-histone signal. If the acetylated-histone antibody works better, your raw data might well suggest a nonsensical greater-than-100% acetylation fraction. (Running two gels instead of one will also free up extra lanes so you can run concentration standards....) Hope that helps, TenOfAllTrades(talk) 23:32, 11 February 2009 (UTC)

mirror paint?

So I have this great, huge, antique mirror I just got for my teeny, tiny room. It really helps. However, the back is chipped in a few places, leading to ugly spots. Is there anything I coudl paint on the front that's "mirror paint" (ie looks like a mirror)? The other choice is to put a smaller mirror at a particular spot in front of it, but I think a small cosmetic solution as above would be better... —Preceding unsigned comment added by 82.120.236.246 (talk) 19:13, 11 February 2009 (UTC)

Nothing you could possibly do on the front of the mirror would ever look right. The reflective layer of the mirror is behind the glass - you'd have to get behind the mirror to fix up the bad spot. There are places that will re-silver a mirror - but the process is quite expensive and usually limited to antique mirrors. May I suggest a google search for "Resilver mirror"...the most promising hit I saw was [8] - but there were many more. The good news is that assuming there are no chips in the glass, this process will have your mirror looking like new. SteveBaker (talk) 19:27, 11 February 2009 (UTC)

You can´t possibly resilver a mirror yourself. Apart from the cost it is highly dangerous, as you work with mercury (?) and other nasty chemicals. You may not even be able to purchase the required chemicals without a relevant license.

The only inexpensive solution I can think of would be to purchase a sheet of acrylic mirror (you can use a very fine jigsaw to fit it to the frame) and insert the thin acrylic plate into the existing frame, maybe even on top of the existing glass. Bear in mind that acrylic is comparatively soft, so you need to take excessive care not to scratch the surface, when working it or when cleaning it. The original surfaces are typically protected by some stick-on foil which you peel off when the work is finished. When "sawing" acrylic sheeting work very slowly and gingerly, as hasty work inevitably leads to a crack in the sheet.

Of course, you can have it resilvered by a professional, but that will a costly option. It may be "cheaper" to have the glass plate replaced. --Cookatoo.ergo.ZooM (talk) 20:26, 11 February 2009 (UTC)

An old trick when an antique mirror has a bit of the silvering scratched off is to stick a little piece of aluminum foil behind the mirror, shiny side facing the room. Instead of a black spot you will then see a spot which blends in better with the rest of the mirror. A 2006 article said that the minimum charge for resilvering an old mirror was $20, and that the cost was about $15 per square foot. It advised that it was cheaper to just buy a replacement mirror unless it was odd shaped, antique, etc. In the 1830's mercury was used, but apparently modern methods use silver nitrate and other chemicals.If it is a really valuable antique, you might wish to get the advice of an expert as to whether the original appearance is more valuable than resilvered "like new" appearance. One company which resilvers mirrors says that one pint of each of the four chemicals they use costs a total of $120, and they even provide the website of their supplier. Edison (talk) 23:19, 11 February 2009 (UTC)

Little spots can easily be disguised with foil behind. For larger spots, you can attach a small mirror behind. (Find a handbag or make-up mirror slightly larger than the hole. Glue it to the back of your mirror, or for a less permanent measure fix with strong double-sided tape.) It adds a strange depth if you look closely, but with a standard glance it's fine, and much better than a large spot. (I've got an old mirror "fixed" in this way, as advised by a furniture restorer, who considered re-silvering too costly for most situations; it works well.) By the way, do you mean slightly antique (i.e. just old) or really antique? If it's valuable, seek the advice of an expert. Very old mirrors used actual silver backs (hence their dark appearance) and spotting is caused by deterioration of the silver, rather than the chipping or wearing away of the backing. Gwinva (talk) 23:45, 11 February 2009 (UTC)

If you are in Europe you can get sticky (um: "adhesive") foil that you can stick on the front. [9] I bet we also have something like that in the US. I would recommend not buying it here [10] because a price difference between Euro 8.29 and $150.00 has to include a golden parachute somewhere in the delivery chain :-o - 76.97.245.5 (talk) 00:03, 12 February 2009 (UTC)

Alternatively you could find a pattern or drawing you like and etch it into the back~, based on the holes you already have in the reflective layer. You could then paint over what has been removed in color or gold. 190.17.201.142 (talk) 00:33, 12 February 2009 (UTC)

If you stick a new mirror to the back of the damaged antique mirror where there are flaws, please consider using a front surface mirror, such as the ones available from Edmund Scientific or [American Science Center[. The silver on the front of the patch mirror reduces parallax. Edison (talk) 06:31, 12 February 2009 (UTC)

CO detector going off

This is not really a science question, but a health one. Here goes:

The CO detector in my apartment keeps going off. It's placed in the hallway between the kitchen, which is closer to the door as well as a window, and the bedrooms. I'm not sure air circulates well there, but I also don't see it as a sink of sorts either. But obviously CO gathers there after cooking, because a couple to a few hours after all the oven fires are turned off, the alarm often goes off.

What can I do to fix this problem? Thanks in advance. Imagine Reason (talk) 20:11, 11 February 2009 (UTC)

Relocate your detector if possible, move something to allow the air flow, or get your oven checked because it could be going off because there is an actual problem? SGGH ^ping! 20:14, 11 February 2009 (UTC)

Yeah; a healthy oven really shouldn't be producing any appreciable levels of CO. It's very much worth getting it tested. ~ mazca ^t|c 21:17, 11 February 2009 (UTC)

Never assume it's a false alarm. CO is very difficult to detect so I doubt you have any way to be certain there isn't actually a problem. Air your house very thoroughly and call someone in to check the oven. --Tango (talk) 21:26, 11 February 2009 (UTC)

Carbon monoxide is odorless and colorless, so your detector is going off for a reason. A smoke detector, now those things are a pain in the ass if you do a lot of horrible cooking like I do. But your CO detector is very important and you should really get that checked. Livewireo (talk) 21:46, 11 February 2009 (UTC)

Our article "Carbon monoxide detector" points out that "CO detectors can be placed near the ceiling or near the floor as CO is very close to the same density as air." This means that CO is not "gathering" anywhere. If your detector is working right, an abnormally high level of CO exists in all the air in your house. You should be scared, and you should have your equipment checked. I would call my local fire department's non-emergency number, if it was me, to get advice about what to do next. --Milkbreath (talk) 23:24, 11 February 2009 (UTC)

Our article gives a wrong connotation about the uniformity distribution CO. CO produced by heating apparatus will rise with the warm air and will thus be "concentrated" although the low molecular weight will ensure it diffuses away effectively. My source is here. 152.16.144.213 (talk) 01:41, 12 February 2009 (UTC)

"Keeps going off"? Does that mean it stops? Check the battery in your monitor: some go off intermittently when the battery is low (to tell you to change it). If the battery is fine (or the monitor is mains operated) you should certainly have your appliances checked. If you have any doubts, get an expert in asap. Gwinva (talk) 23:32, 11 February 2009 (UTC)

Your CO detector likely has a test setting like a smoke detector does (probably a test button or switch) which you can press to see if its working. You should do that after making sure you have a fresh battery. If the test is successful and the battery is fresh, call the landlord and have them check out the oven sooner rather than later. A safety sheet from my workplace advises that smoke detectors' air intakes be vacuumed out annually. I don't know if it applies to CO detectors but it couldn't hurt. In the meantime, you can and should increase air circulation when you cook by using the vent and opening windows so the place is properly ventilated. When you cook, you should leave the cooking vent (and/or windows) on afterwards because quite a few ovens do those self-cleaning cycles (they can last a couple hours) which burns off any cooking residue by heating to a high temperature. Take a gander at Self-cleaning oven. I'm not familiar with the catalytics of ovens, but cleaning all the residue off of the sides of the oven and the especially the heating elements (Edit: the thing where the gas burns) may restore proper catalytic functioning to your oven (conversion of CO to CO₂) if that is the problem. (I'm just speculating). Definitely get the landlord for this, and if he/she doesn't fix the problem, report it to the proper local authorities.152.16.144.213 (talk) 01:41, 12 February 2009 (UTC)

Say what now? Heating elements? In a gas oven?

(If you're getting CO from an electric oven, something's really wrong...what are you doing in there, making charcoal?) Trovatore (talk) 02:08, 12 February 2009 (UTC)

I am/was definitely using the wrong term. By heating element I mean the part where the gas is burning and generating heat. On stove tops I call them burners, but I have no idea what the proper term is when they're in an oven. I don't mean the bars that you see on the top and bottom of electric ovens which turn orange when hot. And now I know that heating element is specific to electricity --> heat via resistance style heaters. Truthfully, I never noticed what the gas burning/heat generating bit in a gas oven looks like. I use an electric oven which does seem to make charcoal whenever I operate it... 152.16.144.213 (talk) 05:15, 12 February 2009 (UTC)

The detectors I've seen all come with a chart that relates concentration of CO to response time: if the concentration is just over the alarm threshold, it may take the detector as much as an hour to respond. On the other hand, if the CO level is acutely dangerous, the detector will respond within seconds. --Carnildo (talk) 23:39, 11 February 2009 (UTC)

I just wanted to add to Carnildo's info. CO is nasty because it can accumulate physiologically over hours time, so just by hanging around with the oven (assuming the oven is the problem) you have been accumulating CO in your own body. The delayed alarm Carnildo talks about is usually tuned to the physiological uptake. See here for what I mean. When the alarm goes off, it means that if you have stayed in the vicinity, you have potentially been inhaling and accumulating an unsafe level of CO. 152.16.144.213 (talk) 01:41, 12 February 2009 (UTC)

Here's something you could try. Use a lighter and see if you get a difference in the flame at different locations or at different times while/after operating your oven. OR That's what our heating/AC expert used to demonstrate we needed a new furnace in a hurry. (Our CO2 detector upstairs hadn't gone off, but the flame at the furnace was extinguished. Ooops!) 76.97.245.5 (talk) 01:09, 12 February 2009 (UTC)

Um, that seems strange. CO is flammable — I would more expect the lighter to ignite it than be put out by it (not that I'd actually expect either). Unless of course there was so much CO that it displaced the oxygen needed to keep the lighter going. But if there'd been that much I'd expect you to have been seriously injured or killed by it.

CO2 is quite another matter — it's not flammable, but it's much less toxic than CO. If there were enough CO2 to put out your lighter, I wouldn't expect it to kill you, but I'd expect you to notice the tingly sensation in your nostrils. --Trovatore (talk) 01:49, 12 February 2009 (UTC)

Oh wait, maybe I misread you. Are you saying the lighter went out when you held it next to the burner in the furnace? Or are you saying there was no flame in the furnace, but the gas was still being delivered? The latter situation is terribly dangerous, of course, because your house might blow up. But I wouldn't go looking for it with a lighter :-). --Trovatore (talk) 02:03, 12 February 2009 (UTC)

I have a CO detector that has an LED readout which shows parts-per-million of CO in the air. When the readout gets to 50 ppm, it sounds a horn. It's interesting to see the ppm number increase when I run a portable propane heater. The CO detector is 9-volt battery operated and looks like a smoke detector. It didn't cost an awful lot - about $30 I think. GlowWorm —Preceding unsigned comment added by 98.17.34.148 (talk) 01:48, 12 February 2009 (UTC)

You say you live in an apartment. Is it possible that you're picking up CO from someone living above, below or to the side of you. It wouldn't be at all surprising that they would be cooking with a gas stove at around the same time as you are cooking. If so, you should probably talk your neighbours into borrowing your CO detector for a few days to see if they are getting a stronger reading. CO is nasty stuff - so you really need to treat this seriously (that's why you bought the detector - right?). Failing that, you need to talk to a professional. Probably your local fire department could help you...give them a call. SteveBaker (talk) 02:20, 12 February 2009 (UTC)

I would recommend you contact your local fire department about conducting a more thorough CO test to find the actual source of the problem. CO is NOT something you want to mess around with. Also, if you live in an appartment, you should contact your landlord about the problem. If they are not helpful, or dismiss your complaint offhand, I would be VERY concerned; your landlord should fix these problems and if they don't they could find their tenants dropping dead from CO poisoning; which could be very bad for business indeed. So please, contact your landlord and the local fire department. This may be nothing, but its not worth making that assumption and being wrong! --Jayron32.talk.contribs 03:12, 12 February 2009 (UTC)

Just in case our OP needs to be scared into action - what CO does is to latch onto the haemoglobin in your red blood cells at the place where the oxygen normally hooks up. This doesn't kill the cell - but it does prevent it from absorbing oxygen. Hence, whenever you breath in CO, some of your blood pretty much stops working. It stays in your blood stream until the red blood cell eventually dies and is replaced with a nice new one. Since these cells live for about 4 months - continual exposure to even low levels of CO builds up over four months - cutting down your ability to absorb oxygen...it's extremely dangerous. SteveBaker (talk) 04:33, 12 February 2009 (UTC)

As others have mentioned, you need to find out what's causing this ASAP. Others have mentioned batteries but also, unless I'm mistaken (I'm pretty sure it was mentioned in an answer a long long while back) CO detectors have a limited life, like smoke alarms, make sure yours isn't too old Nil Einne (talk) 16:03, 12 February 2009 (UTC)

Metamorphosis

I know that evolution doesn't do anything for a reason. I get that.

That being said: i am totally mystified by metamorphosis. It seems like an incredibly costly method of living! Why would a creature outlast others with such a time-consuming/costly life?

Is there a good reason I'm missing as to why it would benefit butterflies and friends to adapt sucha bizarre life?192.136.22.6 (talk) 23:02, 11 February 2009 (UTC)

I guess we'd have to ask "as opposed to what, remaining a caterpillar ? " StuRat (talk) 23:12, 11 February 2009 (UTC)

Flying is a very convenient way of finding a mate, yet butterfly wings are very fragile so they would be very vulnerable if they had them from the start. Metamorphosis means they can grow and eat while in a sturdy caterpillar form and then fly around and find a mate when the time is right. --Tango (talk) 23:27, 11 February 2009 (UTC)

I have no source for this but metamorphosis might also be a good way to minimize exploitation by parasites and predators by changing living habits and behavior. Predators of caterpillars like wasps would waste energy hunting down maneuverable butterflies. Parasites taking advantage of a caterpillar will have to endure a period of time the caterpillar spent as a pupae before they could exploit the butterfly.

Like Tango was talking about above, metamorphosis also allows an organism to have specialized forms for certain periods of its life rather than have one generalist form. All multicellular organisms must grow and mature before they are capable of breeding successfully. (I can't think of any exceptions...) Metamorphosis allows an organism to start off with one form (eg. larva) which is really good at acquiring nutrition. Breeding isn't an issue at this stage in its life, so why waste energy on reproductive structures and displays? Once it acquires enough energy stores, it can switch into an adult form (imago) which is good at finding a mate, breeding, rearing young, etc. It's evolutionarily "worth it" to have efficient specialized forms even though the organism must acquire a little more energy and spend time in a non-motile pupal form during the transition.

Sometimes metamorphosis isn't the best way to exploit a niche. Reptiles (I really mean Amniotes) bypassed the amphibian metamorphosis which necessitated an aquatic stage in exchange for a dry-land-only reproductive pathway. Reptiles could then exploit terrestrial lifestyles with minimal water contact which amphibians cannot. 152.16.144.213 (talk) 00:44, 12 February 2009 (UTC)

The axolotl agrees with you. --Milkbreath (talk) 01:27, 12 February 2009 (UTC)

The OP says it is a mystery - a mystery how evolution could have brought about insect metamorphosis. A caterpillar with many legs turns into an entirely different creature with 6 legs, a 3-segmented body, and wings. That sort of thing leads me to think that something more remains to be said about evolution - and it's something important. In a post a few days ago I said that it is impossible to see how evolution could have developed certain highly specialized organs that will not perform their function unless already perfected, or nearly perfected. In insect metamorphosis, the entire creature changes from one specialized form to an entirely different specialized form. How could such a change have taken place gradually by evolution? How could it have taken place suddenly? At present, the theory of evolution seems to be incomplete. I wonder what biologist will become famous by completing the theory. – GlowWorm. —Preceding unsigned comment added by 98.17.34.148 (talk) 02:33, 12 February 2009 (UTC)

Actually, evolution is not incomplete in the way you mean it to be. If by incomplete you mean "there are future discoveries which may someday alter or add to the theory of evolution" then that statement is moot, because every single scientific theory, from atomic theory to gravitational theory to anything else also meets that definition. Thus, it is no different in that way from ANY OTHER part of science. If you mean "evolutionary theory does not do a good job of explaining observations or producing good predictions" that is also patently false, it is one of the most productive theories in all of science, and has fantastically good and detailed predictive and explanitory power.

The above post makes some rather starkly poor assumptions. For example, caterpillers have only 6 legs. They may have some operative protuberances called Prolegs which appear either before or after their true legs. However, the same six legs in the caterpillar become those of the butterfly. The actual metamorphosis from caterpillar to butterfly is very well documented, and we pretty much know the entire mechanism inside and out. Secondly, don't be confused by "I find it hard to believe that evolution can explain these things" with "evolution cannot explain these things". Having a personal lack of understanding does not mean that the system itself is flawed. transitional forms of life between non-metamorphising life and highly-metamorphosizing life exist both in the fossil record and in the modern world quite readily. For example, some insects display Hemimetabolism to varying degrees, which is a less advanced form of metamorphosis and which can be shown to make a neat continuous line of evolution between non-metamorphosizing critters and ones like butterflies. Merely because we find it hard to believe that evolution could produce these changes does not mean that it doesn't. And the evidence is plentiful that it does. --Jayron32.talk.contribs 03:06, 12 February 2009 (UTC)

The idea that specialized organs could not have evolved incrementally is called the Irreducible complexity argument. Typically, creationists will pick an organ and claim it could not have evolved incrementally. Then evolutionists will explain how it could have evolved incrementally. Then the creationists pick a new organ, and the cycle continues. --Allen (talk) 03:29, 12 February 2009 (UTC)

Additionally, the idea of irreducable complexity generally rests upon a very small number of organs or processes which may have not yet had complete evolutionary explanations (or more likely, DO have complete evolutionary explanations, which creations conveniently leave out of their analysis). Their arguement is based on the assumption that evolutionary theory is rigid (and thus any small inconsistance disproves the whole theory) or instable (such that a single unexplained fact could bring the whole thing down like a house of cards). In the Kitzmiller v. Dover case, for example, they used the flagellum example ad nauseum. The problem with this was a) even if their single example was as yet poorly explained, it could not stand against the weight of the billions of other well explained parts of evolution and b) it turns out that the flagellum is NOT a good example of irreducable complexity, as there are examples of non-flaggelum organs with similar structures and alternate purposes. The IC arguement almost always falls apart in the face of actual data, and the small handful of cases where it doesn't yet fall apart, its just not enough to take down the entire theory of evolution. The concept of transitional forms are well established, and merely because one can find examples of where those forms have not been found does not mean they never existed... --Jayron32.talk.contribs 03:55, 12 February 2009 (UTC)

Yes - exactly. We are at a position now where 'irreducible complexity' - of which insect metamorphosis is supposedly an example - is busted. There are many MANY cases of impressive evolutionary results that seem impossible at first glance. In many cases, biologists have not yet investigated how they came about. HOWEVER, in every single case that they HAVE studied (the evolution of the eye, the 'motor' on flagellum bacteria are two classic examples), we've found perfectly reasonable proof that these complex organs did indeed evolve from simpler things. But evolution is no longer a hypothetical concept but a totally proven "theory" (in the scientific sense of "law") it's as true as the laws of thermodynamics - but more than that, it's logically impossible for it NOT to be true in any system that includes inheritance, mutation and selection.

Hence, rational debate should logically shift from "How can you justify evolution given this example of seeming irreducible complexity?" to "Given that evolution is known to be true - why is this example of seemingly irreducible complexity wrong?". We now KNOW for absolute sure that insects evolved their metamorphosis trick - we may not yet know why or how - but we know for sure that they did evolve it because we know for sure that evolution is true.

So if our OP is merely offering a straw man to argue against evolution...give it up. The argument (in scientific terms) is long over. If we're really asking how evolution did this rather than whether evolution did it - then this is an interesting (but perhaps as yet unanswered) question.

SteveBaker (talk) 04:23, 12 February 2009 (UTC)

Steve!!! No! I read your responses all the time, and they're so great, clever, and occasionally hilarious. I wasn't even SLIGHTLY posing a straw man argument to knock down evolution. I was genuinely curious as to how such metamorphosis could come about. Science rocks, and the more I learn the more i realize I have to learn. (i'm on a different computer, but i'm the OP if that wasn't clear)24.91.161.116 (talk) 05:48, 12 February 2009 (UTC)

It is fun to guess how these things came about. My favorite poser in regard to the mysteries of evolution is beauty, like reef fish and butterflies and birds of paradise. Their allure is not meant for us, but it might as well have been. (On a side note, if you haven't discovered them already, the Xanth books of Piers Anthony play quite entertainingly with this idea of extreme, inexplicable adaptation. Read them in order; they get weaker as he goes.) You are mystified by metamorphosis, and so am I. All development is a big mystery. The second-by-second interplay of chemistries makes it a puzzle too complex to ever be solved. But it is obvious that development must occur, from egg to adult. Just how it occurs in a particular species is an evolutionary crap shoot. I've always supposed that there are a practically infinite number of ways for living things to be, and we're seeing only a tiny fraction of them in practice. Mutation is a shot in the dark; not every viable mutation happens, and often one that's only barely good enough to start with takes root and flourishes and improves. That's how I explain the hyena to myself. Metamorphosis is nothing more than another way organisms develop. My guess is that the larval stage was originally very short, perhaps happening within the egg case, and proceeded directly to metamorphosis. A mutation extended the larval stage, and this gave some advanatge, like the ability to increase body mass before striking out on the search for a mate. --Milkbreath (talk) 13:44, 12 February 2009 (UTC)

I think the answer to your problem with 'beauty' is (as is commonly stated) that it is "in the eye of the beholder". Creatures didn't evolve beauty. Rather, we evolved to perceive these weird things as beautiful. Looked at that way, the things we find beautiful are generally things that suit or are useful to us. There have been many studies to show that (for example) humans find the most 'average' of faces to be the most beautiful. It is likely that we do this in order to weed out serious imperfections in potential mates by regarding 'average' or 'normal' people as desirable. Perhaps we also do this with plants and animals suitable for food - landscapes suitable for hunting in. Cloud formations that portend good hunting weather...who knows? Doubtless this could be a complicated matter - but it's a much easier explanation than that animals somehow strive to meet human standards of beauty. SteveBaker (talk) 05:54, 13 February 2009 (UTC)

One very new (i.e. likely to be largely untested) idea about metamorphis is that it's possible in some instances it's the result of crossbreeding between two species, see [11] if you're interested. I would emphasise that New Scientist is known for publishing controversial ideas that most experts in the field would say are unlikely or impossible without making this clear. Edit: Actually it's not that new it seems [12] [13] although it looks like it hasn't received much acceptance which makes me even more wary of it Nil Einne (talk) 15:48, 12 February 2009 (UTC)

Some of the criticisms made here of irreducible complexity seem to me to show an intolerance of non-destructive deviation from what is regarded as established truth. I think this results from an over-reaction to the complete denial of evolution that is made by some religious persons.

Also, people sometimes develop a non-rational (emotional) vested interest in a certain religious or nonreligious viewpoint. That leads to a closed mind. Any deviation from the viewpoint arouses a non-rational and somewhat vehement opposition. After all, the viewpoint is believed to be ultimate truth.

Science should be open minded. No scientific fact, principle, or law, should be regarded as ultimate truth. Scientific facts sometimes evolve.

One comment made here was that biological evolution had been proved. Well, Newton proved that gravitation is universal by predicting the paths of planets. However, Einstein showed that Newton didn't get everything quite right. But it may be that Einstein, in turn, didn't get everything quite right either. There is some evidence that there is a fifth fundamental force in the universe instead of the four that Einstein had postulated.

In another example, ohm's Law (R= E/I) doesn't get it quite right either. When a current passes through a resistor, the resistor becomes warmer. That changes its resistance, and the amount of heating depends on the amount of current. Thus, ohm's Law is only an approximation – though the approximation is close enough for most practical uses.

I still maintain that the theory of evolution doesn't get it quite right either. I have read an explanation of how the eye, an IC organ, is supposed to have evolved. I was not convinced. No mention was made of the focusable lens, the expanding/contracting iris opening in response to light intensity, the muscles that move the eye ball in its socket, the development of an optic nerve to the brain, or the ability of the brain to comprehend the nerve impulses received. It seemed that the writer had set out to "prove" a preconceived notion.

I think the advocates of creationism and intelligent design also set out to "prove" preconceived notions. However, I believe their ideas about Irreducible Complexity, in some cases, have validity – they cannot be explained by the theory of evolution in its present form.

The comments here included some internet leads and Wiki references. I am looking into them. Thanks for the references. – GlowWorm —Preceding unsigned comment added by 98.17.32.201 (talk) 20:16, 12 February 2009 (UTC)

I liked the theory that the butterfly was a parasite of the caterpillar, which may be a variation of the theory of the merging of two species, mentioned above. But the evidence is really not there for it. Graeme Bartlett (talk) 20:42, 12 February 2009 (UTC)

Broad-mindedness has to be tempered with skepticism. There also comes a point where assuming that seriously busted theories MIGHT still be true is counter-productive. We are well beyond that point with irreducible complexity. We have NEVER found a case of irreducible complexity that we tried-and-failed to reproduce. The intelligent design nut-jobs keep throwing up new cases - and it does take a while for science to knock them down - but every single one we've actually looked into has been impressively and comprehensively 'busted'. The fact that GloWorm doesn't believe it - is entirely due to failure to read enough about the subject. I have read several books on the evolution of the eye and they are VERY convincing - explaining every teeny-tiny intermediate step - and what evolutionary pressure lead to that change. The eye is FAR from irreducible. You should not allow ignorance to drive belief. Do what I did - hit the books.

You disparage ohms law by calling it an 'approximation'. Nothing could be further from the truth - it's another law that is 100% true. It's true that the resistance of a resistor may change over time for any number of reasons - but at any given instant ohm's law applies perfectly. Ohm's law doesn't say that the resistance of a given object is a constant - and it doesn't predict the voltage, current or resistance at some time in the future. All it says is what happens right now - at a single instant of time...and it's correct. So you can drop that nonsense. (I'm pretty sure I've read the same bullshit anti-science crap you've obviously read because it has the exact same mistakes!)

The idea that Newton was "wrong" and therefore Einstein could still be "wrong" is a gross over-simplification. Newton was essentially correct within the slow-speed realms he was able to explore. Einstein is also susceptible to being wrong (or at least only an approximation) outside of the realms we've explored. However, Einstein predicts an ultimate limit to speed - and we've confirmed his theory all the way up to very VERY close to that speed...and there is no sign of an error. So if someone were to overturn Einstein, he'd have to do it in some realm of speed, gravity, mass, time...that we've NEVER explored. We might (conceivably) find that dark-matter doesn't follow Einstein for example...but we're not going to find a way to breach it in 'normal' ranges such as is occupied by stars, black holes, planets, humans and so forth. So any radical new theory really has to plug one of the teeny-tiny 'gaps' which we have not yet explored...and any change it made would only be important in those same teeny-tiny areas of existence. Just as we can treat Newton's laws as true for cars and yo-yo's - we can treat Einstein as true for particles moving at 99.999% of the speed of light - for stars and galaxies and so forth.

It's the same with evolution. You might find some other planet - upon which Lamarkianism is the means for creatures to change. In that case, evolution might not apply. We might find a planet full of self-reproducing robots and then we'd have to search for the "intelligent designer". But for all of the areas we've ever explored, there is absolutely ZERO experimental evidence to disprove it. So on all of earth that we've explored (and CERTAINLY for humans) - intelligent design isn't even worth the effort to disprove it because we have a theory that fits all of the facts and makes predictions that we can test.

I was just watching the Nova program about the Intelligent Design trial at the Dover School Board. There was a GREAT example of science in action there. Humans appear to be related to the great apes - but we have one less chromosome than they do?!? The prediction one would have to make for that to be the case is that at some time in the past, two ape chromosomes got somehow joined together. Well, all genes of all animals have a specific DNA sequence called a "telomere" on either end of each chromosome and a region called a "centromere" in the middle. If evolution is correct then we should be able to find a chromosome with two centromeres and telomeres in the MIDDLE of the chromosome as well as at both ends. Well, this is a testable hypothesis - and indeed, when we look for that, we do indeed find that one of our longer chromosomes has telomeres in the middle and two centromeres. So a prediction made by evolution theory was shown to be correct. Something that's such a long-shot as that is REALLY tough to attribute to ID. Why on earth would an intelligent designer do such a crazy thing? On the other hand, it's PRECISELY the kind of thing that we expect to happen as a result of evolution. Just how much proof do you need to say that ID is crap?

SteveBaker (talk) 06:25, 13 February 2009 (UTC)

Steve says the theories of Incontrovertible Complexity have been seriously busted. Well, an intelligent person can produce a plausible refutation of almost anything he wants to. But I don't think the busting of IC theories has undergone the ultra-, ultra-rigorous examination and re-examination that the theory of evolution itself has undergone. The never-ending opposition to evolution has made its supporters over-zealous. They will not brook even a suggestion that the theory of evolution, while fundamentally true, is incomplete.

Steve says he has read several books about the evolutionary development of the eye. He also tells me to "hit the books". OK Steve, name the books about development of the eye so I can read them too. (I don't think several books have been written about that one thing. I think he means he read about it IN several books that covered other material as well. All right, I won't take cheap advantage of this. In the quick responses of a post a person does not always express himself precisely.)

As for Ohm's Law, I did not "disparage" it. It is true that it is precise at any given instant. But Ohm's Law is virtually never used in that sense. In any practical use it is an approximation.

I did not say Newton was wrong. I said he didn't have it quite right. And I didn't say Einstein could be wrong because Newton was wrong. I said that perhaps Einstein didn't have it quite right either. That twisting of words is not something that is done inadvertently in a quick reply. It is done deliberately.

I said nothing about Lamarkianism. Don't tar me with that brush.

I do not support creationism or intelligent design, as Steve intimated. I made that quite clear.

All in all, Steve's remarks in his post 06:25, 13 February 2009 (UTC) show the over-zealousness I refered to. It leads to overstepping the bounds of accuracy and to the discourtesy that occurred several times in the post. – GlowWorm.

Reverting to the original question about metamorphosis, I have just (yesterday) finished reading On the Origin of Species by one C. Darwin, and was struck by his take on the matter. In the penultimate Chapter XIII, under the sub-head "Embryology", he writes:

"It has already been casually remarked that certain organs in the individual, which when mature become widely different and serve for different purposes, are in the embryo exactly alike. The embryos, also, of distinct animals within the same class are often strikingly similar: a better proof of this cannot be given, than a circumstance mentioned by Agassiz, namely, that having forgotten to ticket the embryo of some vertibrate animal, he cannot now tell whether it be that of a mammal, bird or reptile. The vermiform larvae of moths, flies, beetles, &c, resemble each other much more closely than do the mature insects; but in the case of larvae, the embryos are active, and have been adapted for special lines of life . . . ."

"The points of structure, in which the embryos of widely different animals of the same class resemble each other, often have no direct relation to their conditions of existence. We cannot, for example, suppose that in the embryos of the vertebrata the peculiar loop-like course of the arteries near the branchial slits are related to similar conditions, - in the young mammal which is nourished in the womb of its mother, in the egg of the bird which is hatched in the nest, in the spawn of a frog under water.

The case, however, is different when an animal during any part of its embryonic career is active and has to provide for itself The period of activity may come on earlier or later in life; but whenever it comes on, the adaptation of the larva to its conditions of life is just as perfect and as beautiful as in the adult animal."

Elsewhere he refers to both some non-insectoid metamorphoses such as those of barnacles (about which he knew more than a little) which involve even more drastic morphological changes than the familiar caterpillar->chrysalis->butterfly, and to some insect growth patterns such as those of aphids in which successive stages display increases in size but little change in form (which, I suggest, we might suppose to be more representative of the earliest examples of life).

In (my) summary: various organisms pass through several stages in their growth; insect larvae are a form of active embryo (i.e. an early stage); adaptive pressures more peculiar to a particular stage of growth can cause modification through natural selection on that particular stage; and, just as evolution can by increments drastically change the morphology of a line of organisms hugely over (sufficient) time, so can successive life stages become greatly dissimilar.

I thoroughly recommend (re-)reading "Origins". Although Darwin's 150-year-old discursive literary style takes a some adjusting to, it is invariably lucid and logical, and while in the earlier chapters he beats about the bush a little, the lattter half of the book is wonderfully concentrated . One is repeatedly struck by his prescient suggestions of possible corroborative discoveries that have, indeed, since been made. 87.81.230.195 (talk) 06:55, 14 February 2009 (UTC)

I find it impossible to read any text that is at all complex. When I was a kid the schoolbooks seemed easy and I could get good grades by just skimming through them. I was never given anything challenging in reading or homework. My parents were poorly educated and took no interest in my schooling - they left it all up to the school. Now I can do only light reading. A few days ago I started Darwin's autobiography (it's available from Gutenberg.org), and it is an easy and interesting read. – GlowWorm. —Preceding unsigned comment added by 98.17.32.201 (talk) 18:55, 14 February 2009 (UTC)