Wikipedia:Reference desk/Archives/Science/2012 April 14

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April 14

Difference B IntraCrin & AutoCrin?

Any exists?. 79.179.157.36 (talk) 02:41, 14 April 2012 (UTC)

This kind of sounds like a homework question, so I'm hesitant to answer it directly, but the intracrine article contains the answer. You may also find the autocrine article useful. Red Act (talk) 05:17, 14 April 2012 (UTC)

Health effects of too much magnesium intake

Too much sodium causes high blood pressure, but what happens if your diet contains too much magnesium. I know that my diet contains too much magnesium, about 1 gram per day, while the RDA is 300 mg (it's mostly from potatoes, bread or rice). Above about 600 mg/day, this is considered "too much", but I can't find anything about potentially negative health effects of this. Count Iblis (talk) 03:31, 14 April 2012 (UTC)

See Magnesium#Biological role which explains that if your only source of magnesium is food, it is hard to overdose; i.e. unless you are taking suplements high in magnesium, you're likely fine. Wikipedia does have articles titled Magnesium in biology and Hypermagnesemia, which shouldn't occur if you are only getting dietary sources of magnesium. I should note that, if you are concerned, you should contact a health professional. --Jayron32 03:40, 14 April 2012 (UTC)

Yes, the RDA is a recommended minimum, not intended to be any sort of maximum. Your considered "too much" sounds like a comment from a renal specialist who should be consulted for advice about intake for anyone whose kidneys are not eliminating excess magnesium. Dbfirs 08:09, 15 April 2012 (UTC)

Also, don't forget that potassium is quite unlike magnesium in this respect: potassium can have harmful effects if you take too much. – b_jonas 09:06, 15 April 2012 (UTC)

Atoms in a current

I really don't understand something about current electricity. So, I learned in chemistry that atoms cannot exist if they don't have electrons (i.e, they need electrons as well as a nucleus). But when it comes to current electricity, I learned that a circuit works because electrons leave the atoms and go in a path. But if that's the case, that means that little to no electrons would actually be in the atoms of the wire completing the circuit. But as far as I know this can't exist. So what's really going on the subatomic "world" in the electric wires? Am I misunderstanding something? Can someone help me out? Thanks. 64.229.204.143 (talk) 03:59, 14 April 2012 (UTC)

Electrical conduction is best understood in what is called the "sea of electrons" model of metallic bonding. To put it simply as I can, if you picture a metal as nucleii floating in a "sea of electrons", that's because those electrons, in metals, are very weakly bonded to the nucleus. Electric current covers some of this, and theirs a good quote in the first paragraph of the section titled "Metals" that explains it very well. --Jayron32 04:07, 14 April 2012 (UTC)

Note that only the valence electrons are free to migrate. An atom can gain, lose or share a few electrons (up to 4 in carbon, for example) and still be an atom. Specifically, if it gains or loses a few electrons, it becomes an ion. StuRat (talk) 04:10, 14 April 2012 (UTC)

Indeed, for most metals this amounts to 1 or 2 electrons which get donated to the "sea". --Jayron32 04:11, 14 April 2012 (UTC)

The answers above are correct, but also sort of miss the point. In an electric current electrons are moving, but most of the time the total number of electrons stays the same. If you imagine a wire oriented left-to-right, then you can think of a current such that electrons enter at the left and exit at the right. However, as the electrons flow past the nuclei, the total number of electrons in the vicinity of each nucleus nonetheless will stay approximately constant. Further, the total number of electrons is usually such that the wire has no net charge. In other words the number of electrons in the vicinity of each atom is the same as you expect for neutral atoms. As Jayron says, the nuclei exist in a "sea" of electrons, but more generally each atom has enough electrons flowing past it to remain electrically neutral and chemically well-behaved. To extend the "sea" analogy, it is like noticing that each atom stays "wet" with electrons even though the individual electrons doing the "wetting" are migrating from one atom to the next in a general flow through the wire. Dragons flight (talk) 04:51, 14 April 2012 (UTC)

A wire carrying current often has quite a high "net charge" relative to either terminal of the seat of EMF (generator, battery, or transformer winding.) Isn't that what your voltmeter detects if one terminal is placed on a current-carrying wire and the other on one of the terminals of the battery/generator/transformer/Leyden jar/Van de Graff generator?Edison (talk) 00:47, 15 April 2012 (UTC)

Voltage is different to charge. 203.27.72.5 (talk) 04:15, 15 April 2012 (UTC)

As just a note, if you hit atoms with enough energy, you can split off electrons at will (see ionization) and with a lot of energy, you can strip them off altogether, leaving bare nuclei in a gas-like state (plasma). This is offered just to complicate the "atoms all need electrons all the time" view that you seem to have understood. You're right, of course, that if you stripped all of the electrons off of a wire, it wouldn't really be wire anymore — it'd lose all structural stability and would become gas-like ("vaporized"). --Mr.98 (talk) 12:22, 14 April 2012 (UTC)

I take it in the first sentence you meant to say "off" and in the last sentence "electrons" ? StuRat (talk) 15:00, 14 April 2012 (UTC)

Indeed; I have corrected it. --Mr.98 (talk) 22:11, 14 April 2012 (UTC)

I'll mention another detail that complicates things. When you study atoms in basic physics and chemistry, you learn mostly about how they behave when "unperturbed" - in other words, no external fields applied. However, in a wire carrying an electric current, we have an electromagnetic wave, coupled to the motion of the electrons. The wave and the electrons interact, but they are not the same thing; they don't even move at the same speed. Electromagnetic waves are propagating disturbances of electric fields and magnetic fields. As you probably already know, electrons are affected by both types of field: and both types of field are affected by electron motion. So what we have is a tightly coupled system of interacting microscopic particles, plus two invisible fields that vary in time and space, and all the extra interactions between electrons and atomic nuclei. This gets really hard to analyze, which is why electrical engineers sort of gloss over the details of the atomic physics. As an aggregate, all of these effects contribute to the electrical resistance of the wire. We also use impedance, which is a lot like resistance, but also includes time- and frequency-related effects. If we want to drill all the way down into the root causes of a wire's impedance, we have to carefully solve all the detailed interactions between free electrons, atomically-bound electrons, atomic nuclei, and the electromagnetic field. For macroscopic cases, the statistical averages are good enough. But some semiconductor designers do still need to account for these sorts of atomic-physics interactions, especially as engineers start building smaller and smaller circuits. Modern transistors use just a handful of atoms - so macroscopic empirical rules don't work very well. Nimur (talk) 15:24, 14 April 2012 (UTC)

Nimur got it 100% right until he mentioned impedance in a confusing way. The reactive part of Impedance has nothing to do with, and is not determined by interactions between the electromagnetic field and the electrons. The reactive part of impedance is determined by the bulk dimensions of the conductor and its position with respect to other conductors. Keit121.221.230.170 (talk) 16:51, 14 April 2012 (UTC)

No, Nimur's explanation was quite concise, actually (and is well supported by Wikipedia's article on impedance, as well). Care to elaborate a bit more on your argument (with citations, preferably)? Sebastian Garth (talk) 01:22, 15 April 2012 (UTC)

Nimur said that impedance includes time and frequency related effects. So it does. But frequency related effects include skin effect, and proximity effects. Both of these effects mean that not all conduction elements (valence electrons, free electrons, ions, holes) are equally affected by the electromagnetic field interaction that Nimur mentioned. To calculate these two effects, you can use formalae, derived from first principles, that involve only the bulk dimensions of the conductor of interest and nearby conductors and the spacing. Skin and proximity effects are not reactive effects and thus by definition do not describe an impedance - they merely make the resistance increase with frequency, above the DC value.

Impedance in this context is the vector sum of resistance, capacitive reactance, and inductive reactance. Capacitance has no meaning except with respect to another nearby conductor or portion of the conductor. While (DC) resistance is dependent on the effective mass (the field interaction that Nimur mentioned) of the conduction elements (valence electrons, ions, etc) and is thus dependent on the conductor material (very low for metals, ie valence electrons, high in semiconductors (ie excess electrons and holes), zero for electron streams in vacuum, capacitance is only dependent on the bulk dimensions of the conductors and their spacing, and the permitivity of the space. It is independent of the conduction elements. See any edition of Grounding & Shielding Techniques by Ralf Morrsion for a good easy to read treatment.

Inductive reactance is also properly defined only with respect to a nearby conductor (the return conductor) and is likewise totally independent of the conduction elements and is only dependent on the bulk dimensions of the conductors, their spacing, and the permability of the space. See Appendix D in Faulted Power Systems by Paul M Anderson for a derivation of the formula.

Permability, which describes the magnetic field behaviour of the space, and permitivity, which describes the electric field behavior of the space, is dependent of the atomic scale electromagnetic interactions of the atoms in the space. But the space between conductors is not the conductors, and so not the the conductive elements.

In summary, it could be argued that Nimur was not wrong, entirely, but he was confusing in his use of the term "impedance".

Keit120.145.195.178 (talk) 13:39, 15 April 2012 (UTC)

Well-said. In general, I agree with your analysis of bulk inductance and capacitance, and how they relate to first principles. "For any given concise statement about physics, there exists a longer statement that can clarify some details." This truism may not yet have a name, so I propose we call it "Nimur's Law." Nimur (talk) 16:24, 15 April 2012 (UTC)

Yes, I definitely agree with Nimur's Law and shall state it as such from now on. There's only one thing that is a concern. It is a case where a physicist and an Engineer agree on a definition. This is not normal. Keit120.145.195.178 (talk) 16:34, 15 April 2012 (UTC)

Since the short version is patronizingly called lies to children, perhaps the long version should be truths to adults ? StuRat (talk) 16:27, 15 April 2012 (UTC)

Actually, they just call the long-form "Science." Believe it or not, there are full-time professionals who dedicate their careers to correcting the minutia and errata of others' statements. Entire libraries are full of decades of monthly issues of letters between physicists, each correcting and clarifying the prior statements of the others. To prevent inaccuracies from propagating, and to preserve at least a superficial civility, such publications also employ "referees" whose job is primarily to keep the scientists from cursing at each other. Nimur (talk) 16:35, 15 April 2012 (UTC)

That def would exclude all of Newtonian physics from being "science", since it's just an approximation useful at conditions common here on Earth. The same would be true of most of the atomic models taught in chemistry classes. StuRat (talk) 16:45, 15 April 2012 (UTC)

A better way to understand is is that it is all models. Science does not explain perfect reality, science creates progressively more detailed and accurate models of reality, but no human-created explanation of reality can completely and perfectly match reality, just get arbitrarily close (i.e. close enough for whatever practical work you wish to do which needs that level of precision and accuracy). Even as an individual human, you don't actually experience reality. You experience reality as filtered through your brain, which itself creates models of the world that allow you to operate within the world and not kill yourself; i.e. the model of reality your brain creates is sufficient for your needs, but by no means all that accurate or complete. Science works in that way, just on a grander scale. That leads into what George E. P. Box meant when he said "all models are wrong, but some are useful". That is, no explanation of reality can capture the totality of reality, but insofar as a model is useful to us, we retain it and accept it. That's why chemists can maintain several different models of molecular bonding simultaneously (VSEPR, valence bond theory, hybridization theory, molecular orbital theory), none are completely wrong or completely correct, but each has a realm in which it is useful, and so is retained and taught and used. Scientists spend all that time debating and discussing that minutae to refine their models, but such refinements just get closer to (without actually reaching) actual reality. --Jayron32 03:17, 16 April 2012 (UTC)

Agreed. That's why I disagree with Nimur's take that any model which is not 100% correct isn't science. StuRat (talk) 17:26, 16 April 2012 (UTC)

Co-codamol

If one takes an excessive amount of Co-codamol ,what are the possible side effects and dangers ?Alanwright14 (talk) 09:12, 14 April 2012 (UTC) Carole Wright .

This is not medical advice, but this site contains lots of standard information about co-codamol side effects, overdose, dangers. Co-codamol is essentially a mix of codeine and paracetamol (Tylenol), both of which have significant side effects and very real acute and long-term dangers from overdosing (Codeine#Adverse_effects, Paracetamol toxicity). If you do suspect someone has taken an excessive amount, contact emergency medical professionals immediately for informed instruction. --Mr.98 (talk) 12:27, 14 April 2012 (UTC)

This was in the news recently in the UK because some packs labelled "Co-Codamol" actually contained "Solpadol", which contains a significantly higher dose of codeine. --TammyMoet (talk) 16:26, 14 April 2012 (UTC)

What is PTH (electronics, resistors)?

What does the abbreviation "PTH" stand for when referring to a type of resistor?

Sample 1: "500 resistors, 1/4 Watt, ±5% tolerance, carbon film PTH."

Sample 2: "This is 1/4th Watt, +/- 5% tolerance carbon film PTH resistors. "

--Mortense (talk) 17:44, 14 April 2012 (UTC)

Plated through hole.ie they have leads on them for going through holes in the pcb as opposed to chip resistors which do not..--78.150.233.18 (talk) 18:01, 14 April 2012 (UTC)

PU sections occurence and toxcicity

Refering to the sections "toxcicity"and"occurence" There should be no doubt that plutonium is an man made toxic and radioactive element ;the featured article on plutonium in this worthy encyclopdia gives the impression that Pu is mainly natrually occuring and the toxic effects are minamal. There has been few occasions when people have been exposed to Pu without being exposed to other radioactive elements..The data is incomplete (remember the half life is 10000 years)and uncertain.Uncertainty is a fact in nuclear physics and should be included in a fact based encyclopedia. Something like 2000 tonnes of Pu now exists in the world ..it is no longer a military secret ,indeed it seems to be moving into the economic sphere ,this being the case it is essential that the information in wikipedia is comprehensive and when uncertainty exists it is reported. These two sections are anecdotal badly, sourced and misinformative,I am working on rewrites(see talk) but as a layperson with sporadic internet i may not be in the best position to do this... My question is; why are the misleading articles left in place while someone does the rewrite?, which i assume is happenningSebastian barnes (talk) 18:03, 14 April 2012 (UTC)

Here's a link to the article in question: plutonium. Plutonium#Toxicity is the relevant section. Our Plutonium in the environment article is also related. StuRat (talk) 19:31, 14 April 2012 (UTC)

I don't see the issue. The Toxicity section cites journal articles and books for medical studies involving those exposed to Plutonium. It says what is known about Pu toxicity and mentions previous theories that have been falsified. The whole thing seems to be well written and well sourced (and hardly "anecdotal"). The section on Occurrence says several times how rare it is in nature. It also mentions that nuclear testing and accidents are the primary source of Pu found in the human body. It also mentions that the most abundant element isotope (Thanks StuRat) is manufactured for use in reactors and weapons. Furthermore, the introduction mentions that "Plutonium is mostly a byproduct of nuclear fission in reactors". I don't know where you got the figure of 10,000 years for "the" half life from. All of the isotopes have different half lives, none of which are known to be 10,000 years. 203.27.72.5 (talk) 20:43, 14 April 2012 (UTC)

I take it "the most abundant element" is meant to say "the most abundant isotope" ? StuRat (talk) 21:06, 14 April 2012 (UTC)

If you have a complaint about a specific article, you should post it to the article talk page, not here. In this case it is Talk:Plutonium. As for toxicity, there is a lot of uncertainty about it, but there have been lots of animal studies (the beagle is the model organism for inhaled plutonium) and some human studies, and the article, as far as I know it, reflects these studies. The length of the half life is not related to the uncertainty (individual humans don't live anywhere near the length of the half life, so you can ignore it for the most part when thinking about the effects on individuals). --Mr.98 (talk) 21:50, 14 April 2012 (UTC)

Apparently Sebastian was directed here by someone at the Teahouse. 203.27.72.5 (talk) 22:29, 14 April 2012 (UTC)

Pseudo science

can you guys give list of theories or scientific discoveries that seems pseudo science at first but was later confirmed to be legit 203.112.82.129 (talk) 18:32, 14 April 2012 (UTC)

• Some would say that Lamarkism was a form of pseudoscience, but later inheritance of acquired characteristics was proven to happen in some organisms which exhibit horizontal gene transfer. See e.g Lamarkism#Current_views for additional details. (One could also argue that Lamarck was engaging in valid science, but his claims were simply falsified for many cases.) SemanticMantis (talk) 18:58, 14 April 2012 (UTC)

I think you misunderstand the term "pseudoscience", which is characterized by things that lack fundamental scientific characteristics. There are many presently well-acknowledged scientific theories that, when introduced, were not widely believed, but that didn't make them "pseudoscientific", merely contested (but see the round earth, heliocentricism, relativity, and quantum mechanics for some examples of such). In fact, it is the rare theory that is not initially contested; such doubt and independent verification is the hallmark of good science. Similarly, there are many scientific theories that are wrong, but that also does not make them "pseudoscientific" (see the luminiferous aether for one such). Further, the fact that pseudoscience has proposed some statement doesn't mean that the pseudoscience itself has been "confirmed legit" if some future scientific effort reaches similar conclusions. Suppose, for example, some day that faster-than-light travel is discovered -- Star Trek's references to "warp drive" will have no actual bearing on that process of scientific discovery. Similarly, medical breakthroughs that happen to use magnetism will owe no debt of gratitude toward bracelets with magnets. — Lomn 19:05, 14 April 2012 (UTC)

While pseudoscience just guesses rather than following the scientific method, even guesses will occasionally be correct. An example might be natural substances used to treat disease, not because a rigorous study proved them to be effective, but just due to anecdotal evidence. Many turn out to only work by placebo effect alone, if at all, but others have proven effective, like willow bark, from which aspirin was later isolated. StuRat (talk) 19:25, 14 April 2012 (UTC)

Why are my ears burning? :-) --Aspro (talk) 20:28, 14 April 2012 (UTC)

Going off on a tangent here (I don't claim this point is any way revelatory to the larger discussion about "pseudoscience"), the willow bark — aspirin link is a bit misleading. Willow bark does not contain aspirin; it contains salicylic acid, perhaps in some chemical combination of which I don't know the details.

Aspirin is acetylsalicylic acid, and the "acetyl" part is crucial. From aspirin:

Aspirin's ability to suppress the production of prostaglandins and thromboxanes is due to its irreversible inactivation of the cyclooxygenase (PTGS) enzyme required for prostaglandin and thromboxane synthesis. Aspirin acts as an acetylating agent where an acetyl group is covalently attached to a serine residue in the active site of the PTGS enzyme.

Now, fairly self-evidently, salicylic acid cannot act in that manner, because it has no acetyl group to attach to the enzyme. The fact that salicylic acid, in itself, also has some mild action similar to aspirin, appears to be mostly a coincidence. --Trovatore (talk) 20:47, 14 April 2012 (UTC)

See [1]. At least as of 1985, the idea was that the salicylic acid is oxidized to gentisic acid by the peroxidase activity of PGH synthase, which in turn could be further oxidized to quinonoids which could covalently bond the cyclooxygenase. Note that willow bark was likely determined to have the broad range of NSAID activities by pure observation and experiment, and was being used for its pharmacological effects in the city of Ur two millennia before Abraham. By contrast, aspirin was the result of a cheap chemical synthesis that could reach salicylic acid, which turned out to be corrosive to the stomach lining; under the notion that this was because it was an acid, it was variously acetylated to aspirin and sold in buffered formulations ("Bufferin") in an effort to blunt this which failed. More sophisticated alternatives with multiple salicylate units, like salsalazine, which have to reach the intestine before becoming active, have been invented, but remain locked down under the prescription system making them more or less unavailable to patients, who continue using the old, stupid method, and so as blood sacrifice to the medical cartel we offer a vast number of patients each year with serious gastrointestinal problems, because they don't feel wealthy enough to afford willow extract nor a medical consultation for each time they want an NSAID. Now that's a level of pseudoscience I'd like to think the residents of Ur were smart enough to avoid. Wnt (talk) 03:40, 15 April 2012 (UTC)

Well, that paper appears to contradict our article, or perhaps vice versa. I am not by any means an expert in this area, but someone really ought to resolve this. --Trovatore (talk) 05:33, 15 April 2012 (UTC)

If you take a very long view, in the early modern period, the idea that a mathematician could come up with "philosophical" conclusions was considered methodologically invalid (they wouldn't have used the term pseudoscience, obviously). This was an issue for Copernicus when he wrote his book, and his introduction to De revolutionibus orbium coelestium is concerned with this. There are some people today (serious scholars) who think that Lysenkoism was less nutty than it is usually interpreted as having been. Phrenology was considered pseudoscience in its day, and much of it is still considered pseudoscience, but some aspects of it are considered rather important in the development of psychology. None of those are really strong candidates, though. --Mr.98 (talk) 22:09, 14 April 2012 (UTC)

Eugenics, due to it's association with the Nazis, is rather unpopular, as if it were all pseudoscience (and some of it was, like the "Aryan superiority" bits). Nonetheless, there seems to be some valid science behind it. StuRat (talk) 22:38, 14 April 2012 (UTC)

Actually, there's no evidence that I know of that a species can survive artificial selection in the long term. For many crops nowadays breeders need to turn back to wild cultivars seeking genetic variation that was discarded as inconvenient while seeking the most economically useful strain for the moment - which is also the idea underlying eugenics. Wnt (talk) 03:42, 15 April 2012 (UTC)

Well, since artificial selection is, by definition, as recent as humans, there couldn't possibly be any "long term" evidence, could there ? Unless you count dogs, bred from wolves thousands of years ago, that is. StuRat (talk) 04:06, 15 April 2012 (UTC)

Before its confirmation there were plenty of people who thought of plate tectonics as pseudoscience. Looie496 (talk) 00:29, 15 April 2012 (UTC)

Well, before the mechanisms were known, I suppose observations that "those continents almost look like could fit together" alone would constitute pseudoscience. StuRat (talk) 00:45, 15 April 2012 (UTC)

Why? Sounds to me like an observation leading to the formulation of a testable hypothesis. 203.27.72.5 (talk) 03:12, 15 April 2012 (UTC)

I don't think it was testable at the time. After all, satellites and lasers to accurately measure continental drift are only recently available. StuRat (talk) 04:00, 15 April 2012 (UTC)

The article plate tectonics#Summary gives the impression that there was other evidence of continental drift right from the beginning -- e.g. rock formations that coincided where S. America and Africa fit together, similar fossils, etc. So while many scientists opposed the theory in the absence of any theoretical mechanism for the drifting, I doubt they could have viewed it as pseudoscience. Duoduoduo (talk) 17:55, 15 April 2012 (UTC)

But that could have just been coincidence, similar to how alchemist thought urine might contain gold, since both are yellow. StuRat (talk) 18:17, 15 April 2012 (UTC)

It wouldn't be pseudoscience, just a claim that, at the time, was unfalsifiable. IRWolfie- (talk) 21:48, 15 April 2012 (UTC)

That's like saying that gravitational waves are pseudoscience because we can't detect them with current technology (even if they turn out to not exists, those who predict them are still doing science). And you don't need to directly measure continental drift to get evidence confirming plate tectonics; what about all of the geological evidence? 203.27.72.5 (talk) 04:20, 15 April 2012 (UTC)

In the case of string theory, until they come up with a testable hypothesis, it does indeed seem to fall under pseudoscience. StuRat (talk) 04:51, 15 April 2012 (UTC)

String theory is in principle testable and falsifiable, although we don't yet know how to test it with current or achievable technology. This makes it protoscience, rather then pseudoscience (indeed, it is given as an example of a protoscience in our article). Gandalf61 (talk) 08:42, 15 April 2012 (UTC)

Well, weren't things like the geocentric model of the universe and the five elements being earth, air, fire, water, and ether also protoscience then, in that they would eventually become testable ? StuRat (talk) 17:06, 15 April 2012 (UTC)

They were testable at the time (astronomical observations with the naked eye can show that the geocentric model is false). Believing them without doing the test (or when the test shows it to be incorrect) is what constitutes pseudoscience. 203.27.72.5 (talk) 20:56, 15 April 2012 (UTC)

Which observation with the naked eye can disprove the geocentric model? Galileo couldn't even figure it out until he got his hands on telescopes. 99.245.35.136 (talk) 03:40, 16 April 2012 (UTC)

I believe that would be the apparent retrograde motion of the planets, where they seem to periodically move backwards along their normal orbit. StuRat (talk) 05:41, 16 April 2012 (UTC)

Thanks, didn't know that before. That explains how they differentiated planets from stars in ancients times. 99.245.35.136 (talk) 06:25, 16 April 2012 (UTC)

It's not just retrograde motion that differentiates the planets. When moving forward they still move relative to the constellations, which don't appear to move at all (other than the apparent motion caused by the Earth's rotation). The stars do move, of course, but it's only visible over thousands of years. Everything within the solar system, on the other hand, seems to be in a new position every day. StuRat (talk) 17:22, 16 April 2012 (UTC)

I think that's unfair to the proponents of the geocentric theory. They put forth a theory, tested it with observations, found anomalies, tweaked the theory to make it consistent with the anomalies, did more observations to test it, etc. That's not pseudoscience, it's the scientific method. Sometimes the scientific method leads to a theory ultimately being rejected entirely, especially if it has gotten too unwieldy (as the geocentric theory did), but generally that requires the presence of an alternative theory that's better at explaining the anomalies of the old one. Duoduoduo (talk) 21:06, 15 April 2012 (UTC)

Specifically, I believe they tweaked it by adding epicycles. StuRat (talk) 23:00, 15 April 2012 (UTC)

That depends whether by proponents you mean Aristotel who presented a scientific argument for geocentric theory, or Tommaso Caccini who persecuted Galileo Galilei for presenting a conflicting theory. 203.27.72.5 (talk) 21:30, 15 April 2012 (UTC)

A pure geocentric system with circular orbits is easy to falsify simply by observing retrograde motion, which is why we got the Ptolemaic model with its deferent and epicycles, the Tychonic system, Copernican heliocentrism, and Kepler's heliocentrism with elliptical orbits. (Fun fact: unless you can measure stellar parallax, the above systems are all mathematically equivalent. Stack up enough epicycles and you get an ellipse.) --Carnildo (talk) 02:45, 17 April 2012 (UTC)

The complete lack of any explanation as to what mechanism causes the planets to move in epicycles makes measuring the stellar paralax a moot point; even if you can measure it, who's to to say that the stars aren't just moving in some unexplainable way so as to perfectly account for what we're seeing? 203.27.72.5 (talk) 21:30, 17 April 2012 (UTC)

One thing all those models had in common was that they treated the celestial sphere as a physical object. Once you can measure stellar parallax, you've got to move the stars off the sphere: either they're at varying distances and the Earth moves around the Sun, or the Earth is stationary and every star has its own lateral oscillation with a period of one year. Once you get the ability to do single-time measurements of parallax (eg. a pair of widely-separated telescopes), you can prove the stars are at varying distances. I don't think it's possible to disprove a modified Tychonic system where the Sun and Moon orbit the Earth, while the rest of the universe moves with the Sun, but once you start working with relativity and interstellar distances, the math becomes a lot simpler if you assume the Earth moves. --Carnildo (talk) 00:45, 18 April 2012 (UTC)

I'm no astronomer, but I always assumed that once you start launching satellites and getting measurements of planetary positions from "telescopes" that are at arbitrary positions in the solar system, it would become astronomically (you won't believe me, but no pun intended) difficult to reconcile the measurements with any geocentric model. Someguy1221 (talk) 01:12, 18 April 2012 (UTC)

I didn't say it was pseudoscience, just that lots of geologists thought so -- many thought that the idea of continents wandering around was crazy, comparable to Velikovsky's ideas about planets wandering around (which are still thought of as pseudoscience by the vast majority of scientists). Looie496 (talk) 03:42, 15 April 2012 (UTC)

"The vast majority of scientists" must be the understatement of the year... ;-). --Stephan Schulz (talk) 04:52, 15 April 2012 (UTC)

Apparently it happens in other solar systems... --TammyMoet (talk) 08:00, 15 April 2012 (UTC)

It's an interesting question, but perhaps it's better to rephrase it: Are there any theories or scientific discoveries that are accepted today, but were at one time called pseudoscience by scientific consensus or at least by one or more respected scientists?Sjö (talk) 10:16, 15 April 2012 (UTC)

For background, according to the OED, the first use of "pseudo-science" (hyphenated) was to describe alchemy in 1796. The OED also has examples of the term used to describe blazonry, theology, homeopathy, opinion polling, and psychoanalysis. --Colapeninsula (talk) 12:03, 15 April 2012 (UTC)

The problem with the 'one or more respected scientists' criterion is that it's ridiculously broad. There are probably millions of scientists in the world today, and at least tens of thousands who qualify as 'respected'. If you pick that many people from any community, you're going to get a few loose nuts. I don't know of any specific examples that respond to Sjo's question, but I can certainly point to a number of respected (or at least, once-respected) scientists who have gone the other way and wandered off into pseudoscience. Just among Nobel laureates, we have Luc Montagnier, who has drifted into homeopathy; Linus Pauling, who became enraptured by megavitamin therapy and orthomolecular medicine; Brian Josephson, who dabbles in parapsychology and more recently has been suckered by cold fusion; Kary Mullis fell in with the AIDS denialists and hallucinated a visit by a fluorescent alien raccoon; Louis Ignarro shillsis a scientific consultant for an MLM herbal supplement company; Nikolaas Tinbergen plugged an unsupported and potentially abusive autism therapy. Creationists (and those crypto-creationists who talk about 'intelligent design') like to make lists of scientists who don't support evolutionary theory, or who do support intelligent design. Any time any science is discussed on a television news show, the producers are able to recruit someone with an impresssive-sounding title to take the opposing side for the purposes of 'fairness' or 'balance'. (Project Steve was an interesting response by the evolutionary biologists who got tired of this tactic; there are more biologists named Steve who endorse evolution than biologists in total who oppose it.) TenOfAllTrades(talk) 15:39, 15 April 2012 (UTC)

Very true, and my rephrasing was only an attempt to get away from the discussion about what "seems" to be pseudoscience and start discussing statements that can be verified.Sjö (talk) 16:53, 15 April 2012 (UTC)

The way I've heard it described which I liked is that science and pseudo-science are terms like tall and short, not like "on and off": It's a spectrum not a dichotomy. Few reside on the extreme ends and most fall somewhere in between. People who practice good science will be closer to one end and people who practice bad science will be on the other, but even bad scientists can do some good science and good scientists are certainly capable of bad science. Vespine (talk) 23:19, 15 April 2012 (UTC)

It just occured to me that this is actually already formalized as the Demarcation problem. Vespine (talk) 01:19, 18 April 2012 (UTC)

Hydrons

It's been a long time since Chemistry class, so my apologies for asking what is probably a high school level question. In our blood article, it's stated that most CO₂ is carried in blood via the reaction CO₂ + H₂O → H₂CO₃ → H⁺ + HCO⁻
₃. My eye was caught by the H⁺. Our hydron article notes that H⁺ is very reactive ... so why doesn't it just re-bind immediately to the HCO⁻
₃? Second, more general question: How much energy does it take to liberate an H⁺ ion from a molecule, compared to other chemical reactions? (I suppose there's a an enormous table somewhere.) Comet Tuttle (talk) 18:54, 14 April 2012 (UTC)

It doesn't recombine because it binds to water to form the hydronium cation, which is fairly stable. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 19:05, 14 April 2012 (UTC)

The key thing is that the H⁺, like the stereotypical rockstar, once freed from its first embrace finds many different fans vying for its affections. There are lots of conjugate bases of weak acids, like carboxylic acids, which can react with it. Blood being pH 7.4 must have approximately 10^-7.4 moles of hydrogen ion per liter, which is very little - indicating how quickly that hydrogen reacts. If there were not mechanisms in place to take up the hydrogen ion released by this reaction, the blood pH would become more and more acidic. Another aspect that might help the equilibrium to be reached faster is that if you look up [2] you see in the figure there, that the HCO3^- and H⁺ are emitted at different points in a cycle, with the enzyme carrying charge for some of the time. Thus, the two ions don't shoot out into the solution from the exact same place at the exact same time. Wnt (talk) 00:59, 15 April 2012 (UTC)