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Some articles are unclear

I cannot understand what is said by the articles: protist and algae. The article protist includes algae int it and says that protists are eukaryotic. But the aticle about algae includes cyanobacterias which are prokaryotic. These articles' facts are opposing each other. The article about cyanobacteria includes the cyanobacteria into bacteria domain. But in the article algae there are sentences like this:

• Most algae except cyanobacteria contain chloroplasts

So if algae are protists(as mentioned) and protists are eukaryotes (as mentioned), then cyanobacterias should not be included in algae because they don't have a membrane bounded nucleus. What can we do? --G.Kiruthikan (talk) 04:47, 20 January 2014 (UTC)

Did you read the lead of the algae article? I think it answers your questions. Basically the answer is that the protist article should have said that they include some types of algae. Looie496 (talk) 05:09, 20 January 2014 (UTC)

"It depends who you ask, and when," to some degree. Have a look at some of the most common classification schemes in use today. Some articles are surely using different schema. We can even find and cite sources that give contradictory correct answers!

I'm actually much more interested in this problem that Wikipedia articles contradict each other!

When I went to lower-grade school, our text-books used the five-kingdom classification method (bacteria, protists, fungi, plants, and animals). This was mostly consistent with what I "knew" to be correct; I had read, cover-to-cover, my home library copy of the 1967 World Book Encyclopedia, and it used a similar categorization. By the time I went to high-school biology, our text-books had switched to the "2.5 kingdom" (archaea, bacteria, everything-else) schema. Everything seemed wrong! Even the waterbears were in the wrong chapter of my high-school book, and there can be no doubt what they are! I got into a lot of trouble with my teacher by making noise about that issue. (If only more people could get so passionate about these important flaws in school biology textbooks!)

What had happened is that over the years, new scientific research has enabled us to classify the same organisms in many different ways. There is no single canonically-correct way to classify an organism; and if you assume that some microorganism must be either a protist or a cyanobacteria, you'd better be very sure you know exactly how you've defined those classifications. Sometimes, superficial treatments about science portray a level of consistency that doesn't really exist in the research community. Molecular biologists may prefer one classification scheme, while zoologists prefer a different scheme, while ecological conservation policy-makers use a totally different type of taxonomy. Classification schemes for organisms are not "facts;" they are positions that are put forward by prominent researchers. Old-fashioned publications, like paper encyclopedias and schoolbooks, had an editorial board who would convene, and there would be a top-down commandment specifying that one set of "facts" was canonically correct and reflected the current state of scientific knowledge (at least for the purposes of that year's publication). That's not how science works - if anything, Wikipedia is giving you more "correctness" by presenting contradictory information and letting you make the critical judgement.

If you are classifying an organism, you need to know which scheme you're using, and what basis is the standard for determining taxa. You should be aware that different sources and authors may use different schema. Particularly at Wikipedia, we are an encyclopedia edited by many individuals, and with very little coherent editorial oversight; nobody here is "the Chief Editor" who commands top-down that all articles shall use schema X. So, at a superficial inspection, our articles may contradict each other. Nimur (talk) 10:30, 20 January 2014 (UTC)

• In addition to Nimur's good points above, the reason it is hard to reconcile "protist" with "algae" is that neither of these groupings are currently believed to be clades. They are both highly polyphyletic, and so they don't make much sense in relation to each other, or to our more modern systematics. You might also be interested in Phylogenetic_nomenclature#Philosophy. Finally, if you read carefully, I don't think our article protist actually says or even implies that all algae are protists. SemanticMantis (talk) 00:07, 21 January 2014 (UTC)

I have now understood why there were contradictions. But we should make sure that other readers will not get any of the contradictions. Then all will got complicated. (I don't know the grammer well). Some books say that the classification of protists is not natural but rather it is artificial. They say that protists include organisms with many different evolutionary traits and no very recent evolutionary similarities. So regarding this point I think that there is no way of getting out of this complication. The only thing that matters is that according to Wikipedia's article, all protists are eukaryotic. So I think there is a small possibility of excluding cyanobacterias from protists.--G.Kiruthikan (talk) 02:43, 22 January 2014 (UTC)

January 21

Old French mechanical signals

How exactly did the mechanical ralentissement (slow 30) signal work? Was the mechanical vane operated from the signal box via the lever frame, or was it directly linked to the switch and the associated rappel de ralentissement signal? Also, how exactly did it produce the two yellow lights in the closed position, and the single green in the open? Were there two (or three) separate color lamps, or only one lamp fitted with movable color filters linked to the vane? Thanks in advance! 67.169.83.209 (talk) 03:37, 21 January 2014 (UTC)

I forwarded this query to Clive Feather, who has kindly replied as follows:

From http://www.carreweb.fr/stfr/sl_en.html and other pages (found by searching for "French railway signalling" or similar), it is clear that Ralentissment 30 is an aspect shown at the running signal (like "Medium to Clear" in North American practice). For the mechanical layout, you have a Carré above a Ral30. If the lever for the main route is pulled, only the Carré rotates. If the lever for the diverging route is pulled, both rotate.

If you asked me to implement this, I'd use an inverted slot mechanism. You have three bars that are centre pivoted on the same axis. A weight holds the left side down by default. The wire from the main lever pulls on the right end of bar 1. The wire from the diverging lever runs through the Ral30 rotation mechanism and pulls on the right end of bar 3. Bars 1 and 3 each have a short bar at right angles that crosses over to bar 2. So if either lever is pulled, the right end of bar 2 is pushed down by the relevant short bar; this in turn pulls the Carré rotation mechanism. When the lever is replaced, the weight on bar 2 rotates the Carré back again. (It's an "inverted" slot because the standard slot is an "and" gate, not an "or".)

Rappel de ralentissment is like the UK double yellow; it's a preliminary warning used when the signals are closer togther. The mechanical version would be driven from the same lever or from the equivalent of a distant signal lever.

It's clear from the images that there are three separate lamps.

-- Clive D.W. Feather

Forwarded (and lightly copedited/wikified) by: --50.100.193.107 (talk) 21:28, 22 January 2014 (UTC)

Thanks! So it is operated from the lever frame and not linked directly to the switch mechanism, right? 67.169.83.209 (talk) 03:50, 23 January 2014 (UTC)

what is the difference between chemistry and biochemistry in the blood test

I have noticed that there are two kinds of blood tetsts. One is chemistry, and the two is biochemistry. So what is the different between the two? which kinds of tests are included in the chemistry or biochemistry blood tests. 194.114.146.227 (talk) 05:53, 21 January 2014 (UTC)

See Blood test#Types of blood tests. Red Act (talk) 07:02, 21 January 2014 (UTC)

thank you. But it doesn't answer on my question: What does define a bihemiemical blood test as biochemical test? 194.114.146.227 (talk) 09:43, 21 January 2014 (UTC)

Chemical tests relate to things like simple ions (e.g. Na+, K+) and pH. Biochemical tests look for larger molecules, for example certain serum proteins e.g. serum albumin. --—Cyclonenim | Chat  09:27, 21 January 2014 (UTC)

Thank you. So I can understand that the chemical blood test is looking for the elements or the ions of them in the blood while the biochemical tests is looking for molecule. Am I right? 194.114.146.227 (talk) 09:43, 21 January 2014 (UTC)

Not quite. Biochemical tests are a subset of chemical tests. A biochemical test is a chemical test that detects or quantifies a biomolecule. If you want to reserve the name "chemical test" to "chemical tests that are not biochemical tests", they would still include ions composed of several atoms, such as phosphate, and dissolved gases such as ammonia. --NorwegianBlue ^talk 20:46, 21 January 2014 (UTC) — Preceding unsigned comment added by 109.189.65.217 (talk)

Identify this animal

What animal is this? [1] — Preceding unsigned comment added by Bobatnet (talk • contribs) 10:17, 21 January 2014‎

a monitor lizard? —Tamfang (talk) 11:00, 21 January 2014 (UTC)

A legavaan? A white-throated Rock_monitor. 196.214.78.114 (talk) 13:14, 21 January 2014 (UTC)

A bengal monitor, I think. Mikenorton (talk) 21:09, 21 January 2014 (UTC)

Goanna? HiLo48 (talk) 06:04, 22 January 2014 (UTC)

Looks like a Lace Monitor (varanus varius) to me, quite a big one. There's not many monitors that have those spots. Tom duF (talk) 07:01, 22 January 2014 (UTC)

"Alabama Rot" in the UK

The BBC reports that 17 dogs across Britain have been killed by "Alabama Rot". However an article mentioning Alabama rot says that it is "Idiopathic cutaneous and renal glomerular disease", affects only Greyhounds, and is associated with them eating raw meat. What makes them think that the cases in the UK are the same disease, it sounds quite different. -- Q Chris (talk) 10:59, 21 January 2014 (UTC)

The BBC report does not say that, but maybe it has been updated since you read it. Suggest you read it again.--Shantavira|^{feed me} 11:47, 21 January 2014 (UTC)

You're right it changed! -- Q Chris (talk) 13:29, 21 January 2014 (UTC)

The BBC article says it's "similar to Alabama rot" - not that it is that. Both diseases involve skin lesions in the early stages, Idiopathic just means that the cause is unknown, and "renal glomerular disease" means it affects the kidneys (see Glomerulus), which probably means it leads to renal (kidney) failure, like the disease in the BBC article. The second article says Alabama rot has "only been reported in greyhounds". That doesn't mean it only affects greyhounds - only they it hasn't been seen in other breeds yet. Richerman (talk) 13:21, 21 January 2014 (UTC)

Not to be confused with the live concert CD: Alabama Rot in the UK      —(sorry, couldn't resist. 71.20.250.51 (talk) 18:53, 21 January 2014 (UTC)}

Metric expansion of space 2

So, as I seen from the graphic, the recession velocity didn't change too much with the time. My final question is: if there wasn't that difference, how is possible that the limit of our observable universe is 46 billion light-years, where the recession speed is three times c (the light's speed)? This would mean that the recession velocity would have at least triplied from the time the radiation that reacht us was emitted, a thing that according to the graphic is impossible (the highest difference isn't more than 20%). Thanks for answering and excuse me for my insistence. 93.45.32.204 (talk) 12:56, 21 January 2014 (UTC)

It doesn't mean that at all. Suppose that 6 billion years ago, the universe was 50% its current size, so a=0.5. A photon travels for 1 year across the universe. That one light-year would be two light-years today, giving the impression that the ancient photon traveled at 2c.

Mathematically, a photon travels a distance c*dt in time dt. But this distance corresponds to a distance of c*dt/a(t) in today's universe, because the universe has since expanded by a factor of 1/a. To find the size of the observable universe, we integrate c*dt/a from t=0 to t=13.7 billion years:

$R=\int _{0}^{t_{age}}c{\frac {dt}{0.72*sinh^{2/3}(1.28H_{0}t)}}$

$\approx {\frac {3.45c}{H_{0}}}$

where $c/H_{0}$ is very close to 13.6 billion light-years. Multiplying that by 3.45 gives 47 billion light-years. You can see the result of the integral here. --Bowlhover (talk) 21:02, 21 January 2014 (UTC)

The recession speed was generally higher in the past, not lower, which makes sense since gravitational attraction slows expansion down. If it weren't for the cosmological constant, the recession speed would always decrease. The speed goes to infinity at the big bang (in the standard radiation-dominated model without inflation).

The image on the right shows visually what's going on with the distances. Light travels at a "45° angle" relative to the local metric. The earth (brown, left) and a distant quasar (yellow, right) have gone from a few billion light years apart to 28 billion light years apart in 13 billion years, which is an average recession speed of about 2c over that time, but light (red) traveling at a local speed of c can get from one to the other regardless. The geometry just works out that way. It's often said that the distance the light travels early on "counts for more" because the distance it has covered later expands. I'm not sure how much I like that explanation, but it's probably fine if you find it helpful. -- BenRG (talk) 20:47, 21 January 2014 (UTC)

Ancient Mesopotamian units of measurement

Dear Sirs

Regarding mesopotanian measurement standards the talk section describes a potential problem

In the table of values the length of the Cubit and smaller values seens to be consistant but the values fro the larger standards appear to be rounded off

the talk section describes a possinle solution which seems correct to me

IT IS VERY IMPORTANT to researchers like myself to have accurate data

I have been critized for using this Wikepedia reference but am convinced that you are correct in stating the length of the cubit at 497 mm

can you help me overcome my rejection of by reviewers on this single issue

Roland Boucher — Preceding unsigned comment added by Roland Boucher (talk • contribs) 16:33, 21 January 2014 (UTC)

For convenience, this question seems to be about our article Ancient_Mesopotamian_units_of_measurement. That article gives no source for the claim 1 cubit=497mm. Cubit gives some examples of ancient metrology standards that have been recovered, with a range of 518 to 529 mm. It then states that 450mm is an estimate used by biblical scholars.

If I were reviewing your article, I would not allow you to publish 1cubit=497mm based on only a citation to Wikipedia. I looked quickly on google scholar, and found this paper, which is probably citable, [2] and this manuscript [3], which is not citable, though it does have some good references for several types of cubits and metric equivalents that you can read/cite for a peer-reviewed article. If you cannot get access to these articles, I suggest you ask at WP:REX. Finally, if you are seeking to be a good researcher in this field, then you are in the best position to improve these WP articles! You can add the citations that you need for your research to support our articles, and everyone then can benefit from your work! SemanticMantis (talk) 17:45, 21 January 2014 (UTC)

Finding the value for the cubit at the particular time and space that you're researching is essential. For example, the Olympias was a super-carefully researched reconstruction of a Greek trireme (an oared vessel). They spent a small fortune building the thing - and only after they tried putting a crew into it to row it did they discover that they'd used "the wrong cubit" and the ship was much more cramped than it should have been. Given the massive amount of work they put into doing this - this minor catastrophy is a measure of how easy it is to get the wrong cubit. It's really not an easy question to answer - and there is no single answer that's correct over more than a small interval of time and a small geographical region. Worse still, researchers can only really relate these ancient cubit measures to modern units by physically measuring some historical artifact who's dimensions were documented in cubits. We know the dimensions of things like the great pyramid in cubits - and we can measure the real thing and know what size the pyramid builder's cubit was...but if you want to know the size of cubit used by a trireme builder, you're right out of luck because there are no surviving vessels of that kind still around. (I don't recall how the Olympias people figured out how they'd screwed up). SteveBaker (talk) 21:04, 21 January 2014 (UTC)

The other way of finding out is by finding extant physical standard cubits. Our cubit article has photos of a few, and says "Fourteen such rods, including one double cubit rod, were described and compared by Lepsius in 1865" -- so at least some cubits can be "rigorously" converted to metric. As you say though, it really depends on time and place, and those known samples won't necessarily say much about the cubits that Roland needs. I think he could probably dig through the refs I gave above and find an estimate that is at least vaguely for the right time and place. For something this subtle, I think that's far better than relying on the authority of Wikipedia! SemanticMantis (talk) 22:06, 21 January 2014 (UTC)

Hmmm, our article on the trireme doesn't cover the cubit mix-up. I'm reminded of a film This Is Spinal Tap which came out just a year afterward -- I'm not seeing any hits to document a connection, but my nose knows. :) Wnt (talk) 22:40, 23 January 2014 (UTC)

I'm not sure what your nose knows...but it's all described in their book "The Athenian Trireme" by Morrison, Coates and Rankov (an excellent book BTW) - with the relevant passage starting on page 245 & 246. "...excavations at Philon's naval storehouse in the Piraeus in 1989 revealed that this building of the mid-fourth century had been constructed using a foot of 0.327m in length and therefore a cubit (= 1.5 feet) of 0.49m. This discovery suggested that the longer cubit could have been used contemporaneously in other naval contexts, such as ship construction. If so, then the two-cubit (rowing space) room of an Athenian trieres could have been as much as 0.98 meter, an invaluable 9 centimeters longer than that of the Olympias." ...I'm not going to quote it all because the explanation runs on for most of the chapter, but it eventually emerges that this error in the choice of 'which cubit' meant that the rowers in their reconstructed ship were too cramped to do their work efficiently - and that this more or less invalidated much of the data they collected over the speed and acceleration rate of the vessel compared to the real thing.

I know all this because I spent a long time conversing with the authors because they were interested in a video-game I was writing that involved Greek sea battles with triremes. I managed (for example) to prove to them that their theory that the ships would have communicated using flag signals from on deck would be impossible due to how low the deck is to the ocean - and the curvature of the earth! The greeks de-masted their ships before battle - so they couldn't haul flags up to the mast-heads - and practical experiments with the Olympias made it quite clear that using drums or trumpets to communicate would have been impossible given the deafening amount of noise made by the rowers and their oars. They couldn't have sent out smaller ships as messengers because the trireme was the fastest vehicle known to mankind at the time and the messengers would have been unable to catch them once battle had commenced. This inability to communicate orders once the action had started has severe implications for how the Greek commanders ran large scale battles - which in turn casts doubt on modern interpretations of several historic naval battles! SteveBaker (talk) 15:02, 24 January 2014 (UTC)

Hmmmm, smoke signals, kites, flaming arrows? But quite interesting! Wnt (talk) 17:54, 24 January 2014 (UTC)

Trouble is, there is no historical account of them doing any of those things. Fire was a really feared thing on wooden ships - so it's unlikely that they'd want to be loosing flaming arrows right in the middle of a bunch of friendly ships! (Yes, I know you're going to mention "Greek fire" - but that didn't start to appear until long after the heyday of Greek naval power - it was really a Byzantine invention). Kites were not known in Europe until the end of the 13th century - so that's extremely unlikely. (Hint: Read more articles before speculating!) It's known that triremes carried both trumpets and drums - and that had long been thought to be used to pass on orders between ships - but the Olympias study strongly suggested that they were instead used to relay orders to the rowers and used to carry a beat that would determine the pace of the rowers (especially during acceleration and turning). The "discovery" that triremes are incredibly noisy places was not obvious until someone tried to get one moving quickly under oars. SteveBaker (talk) 03:07, 25 January 2014 (UTC)

January 22

Is this right? (Order of reactants)

The problem is Zero, First and Second order reaction rate... things (I'm so screwed I don't even know the correct way to say it. but anyway, I'm not sure if this is correct, but It's what I gleaned from what I've read online:

• A zero order reactant does not affect the rate of reaction if doubled
• a first order reactant makes the rate go two times as fast if doubled
• a second order reactant makes the rate go four times as fast if doubled.

Am I figuring this correctly?--Ye Olde Luke (talk) 04:04, 22 January 2014 (UTC)

According to our article rate equation. A zero-order reaction is at a constant rate with changing concentration of reactant, a first-order reaction is linearly proportional to the concentration of reactant, and a second-order reaction is proportional to the square of the concentration. So yes, the example numbers you cite are correct. SpinningSpark 16:29, 22 January 2014 (UTC)

Awesome, thanks! --Ye Olde Luke (talk) 01:06, 24 January 2014 (UTC)

User:Ye Olde Luke, be careful. Spinningspark's answer, and our article, say the reaction rate is proportional to the square of a second order reactant. Mathematically, we say x is proportional to y^2 if x=Cy^2, for some constant C. My understanding is that this constant would depend on the details of the chemical species involved, but I believe it is incorrect to say that doubling a second order reactant always means the reaction goes exactly 4 times as fast. But I'm speaking mathematically, not as a chemist; perhaps the meaning is a little different in chemistry. SemanticMantis (talk) 17:04, 24 January 2014 (UTC)

@SemanticMantis: If y is doubled in $x=Cy^{2}$ then x is quadrupled regardless of the value of C. SpinningSpark 01:46, 25 January 2014 (UTC)

Polar Bears

If a few polar bears were introduced to Antarctica, what would happen to all the penguins? — Preceding unsigned comment added by 216.114.215.239 (talk) 04:15, 22 January 2014 (UTC)

As long as those polar bears are all male the answer is not much. 220.239.51.150 (talk) 05:46, 22 January 2014 (UTC)

And if they are all female? --Bowlhover (talk) 05:54, 22 January 2014 (UTC)

Still not much. The IP editor is suggesting that they couldn't mate and thus would die off after a few years. Dismas|^(talk) 07:59, 22 January 2014 (UTC)

Polar bears live for around 25 years...if there is going to be ecological damage, I'd expect it to happen long before enough of the bears died out to prevent it. SteveBaker (talk) 16:54, 22 January 2014 (UTC)

It depends greatly how you intepret 'a few'. I would intepret it to be a fairly low number less than 20. 10 polar bears could definitely cause great ecological damage, heck even if only 5 die they could also cause great ecological damage if left unchecked. I mean a single rat, cat or dog can devaste an unadapted population [4]. That said, it's a lot less likely than if you import a breeding group. Nil Einne (talk) 00:14, 23 January 2014 (UTC)

The penguins would be fine. The polar bears couldn't get the wrappers off. Rojomoke (talk) 06:33, 22 January 2014 (UTC)

Some joking is fine, but I think the main focus should be answering the poster's question. That's part of civility.76.218.104.210 (talk) 12:28, 22 January 2014 (UTC)

The joke isn't even that unique [5] Nil Einne (talk) 00:14, 23 January 2014 (UTC)

Uniqueness is an absolute, so something either is unique or isn't. This info should allow you to supply perfecter responses in the future. :-) StuRat (talk) 00:26, 23 January 2014 (UTC)

[6], [7], [8], [9], [10], [11], [12], Comparison (grammar)#cite_note-4. Nil Einne (talk) 08:23, 23 January 2014 (UTC)

It's pretty difficult to predict the effect of introducing a non-native species; the oft-quoted examples of brown tree snakes, rabbits in Australia and, to a lesser extent gray squirrels, suggest it may not be good news for the penguins, but food webs are complicated and who knows what trophic cascade may follow. benmoore 13:10, 22 January 2014 (UTC)

Hear, hear! USA government actually promoted planting kudzu in the south, to disastrous effects. Experts usually know enough to know that they cannot predict the long-term outcomes of population dynamics of endemic species when exposed to introduced species. Really, we don't even know if polar bears are any good at catching penguins ;) SemanticMantis (talk) 15:12, 22 January 2014 (UTC)

It's important to note that many (most?) species of penguin don't live anywhere near the antarctic - so while it's possible, and even quite likely that some of them would suffer - it's undoubtedly true that not all of them would even notice. For the antarctic penguins, let's consider what polar bears eat - and how they hunt. Here are some quotes from our Polar bear article:

• "Mature bears tend to eat only the calorie-rich skin and blubber of the seal, whereas younger bears consume the protein-rich red meat. Studies have also photographed polar bears scaling near-vertical cliffs, to eat birds' chicks and eggs. For subadult bears which are independent of their mother but have not yet gained enough experience and body size to successfully hunt seals, scavenging the carcasses from other bears' kills is an important source of nutrition." -- There are plenty of seals in the Antarctic, although not the familiar species that the bear prey on. So we might expect the antarctic seals to have a very hard time of things - they aren't adapted to avoid land-predators, their biggest problem normally being killer whales. Once they get over the 6 months of "jet lag" due to mid-winter being in July, I think this would give the bears the diet they need without too much trouble. Since we know they will take birds eggs and chicks, they might well cause the penguins problems - we know that penguins are completely unafraid of humans - so very likely they'd just stand around looking stupid while the bears grab their eggs and chicks.
• "Most terrestrial animals in the Arctic can outrun the polar bear on land as polar bears overheat quickly, and most marine animals the bear encounters can outswim it. " - so the bears won't be able to catch penguins in the ocean. Whether a penguin can out-run a bear is hard to guess.

My best read on this is that if you could transfer the bears without screwing up their body clocks and have them hibernate at the right times - then they'd survive just fine on seal meat...possibly thriving because the seals don't expect attacks when on land. I think the bears might then not need to resort to hunting penguins - and when they do, it would be chicks and eggs that they'd grab. Since leopard seals are a major predator of penguins - and the seals would be in huge trouble from the bears - the penguins might actually do rather well out of the deal.

Bears prefer to hunt in sea-ice - which will constrain them to the oceans' edge - so some penguins that do their breeding inland might also be OK.

CONCLUSION: Both bears and penguins probably do just fine...very, very bad news for the seal population though. SteveBaker (talk) 16:32, 22 January 2014 (UTC)

See also polar bear which mentions difference between Artic and Antartic seals believed to be partially the result of polar bear predation. I wouldn't BTW underestimate the possible effect of polar bears on Antartic penguins. Seals in the Antartic and of course the terrain are somewhat different from those in the Artic. And more significantly, many examples have shown predatorsorganisms are nothing if not good at adapting to new preyfood species they encounter in a new environment. Several commentators seem to agree [13] [14] [15] [16] [17] [18] [19] [20]. (The first source BTW may be a little confusing, the paper it refers to [21] [22] is not about such long range translocations and in fact specifically mentions polar bears to Antartica as something they are not proposing.) And of course, if they are too successful at hunting seals and you're right there's a good chance to think they will be, they could easily quickly devaste the seal population even more so if you import a breeding group. And as they devaste the seal population and their plentyful food supply runs out, if they weren't already hunting penguins there's a good chance they will start. Nil Einne (talk) 00:14, 23 January 2014 (UTC)

I agree - this is a complicated scenario. Whether the bears would be able to make a significant dent in the size of the seal population is very hard to estimate...and for the penguins, that's a critical thing. If the bears can be satiated from the existing seal population - depressing their numbers, but not eradicating them - then the penguins win because the bears have full stomachs and there are fewer seals predating on them. If the bears wipe out the seals completely, then they'll have to start eating penguins to survive - so that's really bad news for the penguins. Somewhere there is a tipping point where bears are eating penguins - but the number of seal predators is depressed enough to make up for those losses. But an artificially-created scenario isn't likely to produce that result naturally - so the entire eco-system is more likely to go into frequent boom/bust cycles. The predation rates in the natural population have evolved to produce a stable balance - but it could take a hundred thousand years for evolution to catch up with a sudden man-made change like this, and that might be enough time to see the extinction of seals, then penguins and soon after, the bears. SteveBaker (talk) 16:48, 23 January 2014 (UTC)

You should also consider the seals that would have been eaten by the whales anyway that the polar bears got to first (that's a wash). So not as much attrition as originally thought.165.212.189.187 (talk) 21:19, 24 January 2014 (UTC)

I doubt it's "a wash" - if there were a one in fifty chance per month of a particular seal being eaten by a whale - then the one in fifty chance that the polar bear got it first is a pretty small percentage. Also, the whales aren't just going to go hungry if they fail to catch a seal - they'll keep looking until the get one. Of course since starving the whales would also cause them to go for more penguins, it's an even messier food mesh than I'd previously suggested. Bottom line here is *still* that this is a highly speculative question, and while we can come up with scenarios that apply pressure to one part or other of the population - we don't have the data to know which ones are the driving forces. 02:54, 25 January 2014 (UTC)

Elephants

Are elephants aware that the main reason they are being hunted by elephant poachers is for the ivory?76.218.104.210 (talk) 12:26, 22 January 2014 (UTC)

It seems like you're asking about awareness on a cognitive level, which seems unlikely. But on a related note, (and I'm not aware of the actual research the press was based on) a few years ago it was claimed (e.g.) that due to the artificial selection imposed on elephants, killing those with the largest tusks, the mean population tusk length was decreasing. I'm not sure how they accounted for survivorship bias and it seems unlikely such a fitness benefit could be realised in such a short time, but then again I think dramatic morphological changes were noted in Atlantic cod in the North Sea before strict fishing restrictions were put in place, so who knows. benmoore 13:03, 22 January 2014 (UTC)

There is simply no way to know what the elephants may or may not be "aware" of. We can't know what any other beings are thinking - I don't know what my next door neighbor is aware of without asking, and how would you ask an elephant? You might possibly be able to prove that they were *UN*aware (eg if the poachers removed the entire elephant carcass before removing the tusks - you'd be fairly sure that the elephants wouldn't know whether they were after the ivory or...the toenails or something) - but even if they saw the tusk removal happening, it's not clear what they would or wouldn't be able to deduce from that. Worse still, you're asking for us to know whether the elephant knows what the poacher is thinking - and that's two levels of unknowability. SteveBaker (talk) 16:13, 22 January 2014 (UTC)

This made me think of the bear that watched its parents get shot and killed and then when faced with the hunter rolled over on its back as if to say "dont shoot me; it seems that you like us to lay still so here you go, but dont kill me" anyone hear of this account or is it some "rural" legend?165.212.189.187 (talk) 16:33, 22 January 2014 (UTC)

I guess what I meant is that it seems the bear deduced (albeit somewhat incorrectly) that the hunter wanted all the bears to "lay still" (be dead).165.212.189.187 (talk) 18:27, 22 January 2014 (UTC)

Consider the human equivalent. If random passersby were targeted by a psycho killer with a particular fixation (say for left-handed people with big noses), would they be able to decipher the reason from a tiny sample set? No. Clarityfiend (talk) 01:41, 23 January 2014 (UTC)

Whoa, why consider this obtuse example?? Consider .... me on a toilet. So what? Instead, Clarity, please give us some clarity as to why the bear acted the way it did. 165.212.189.187 (talk) 17:38, 23 January 2014 (UTC)

I thought there might be some ways a very elephant-knowledgeable and imaginative human in elephant territory might discern such awareness from elephants' day to day behavior, or devise a clever test for that kind of awareness. Also, I respectfully disagree with Clarityfiend. I dont think the analogy Clarityfiend provided is very close to what's been happening in Chad, according to Wikipedia.--Richard Peterson76.218.104.210 (talk) 09:33, 23 January 2014 (UTC)

How not? Is an individual elephant likely to witness (and survive) more than one hunt? Drawing conclusions from one such incident or even two would be hard for people. Why would it be any easier for elephants? Clarityfiend (talk) 11:50, 23 January 2014 (UTC)

Well if there were an enormous , well over 50%, decrease of human population by widespread slaughter, by a lot of hunters, and our bodies were left to rot, and all that was taken from us were our upper front teeth, those people remaining who came upon our dead bodies could notice. Likewise, living elephants could come upon herds of murdered detusked elephants more than once.76.218.104.210 (talk) 08:31, 24 January 2014 (UTC)

I think you mean hard for unimaginative pessimists who can't ever draw any conclusions from anything ever, because we cant really "know" anything.165.212.189.187 (talk) 17:40, 23 January 2014 (UTC)

Could we please keep this civil, 165.212.189.187?76.218.104.210 (talk) 08:31, 24 January 2014 (UTC)

@User:165.212.189.187 - that's ridiculous. There are plenty of things that we can know and conclusions that we can draw about the world - we know that there are elephants, we know that they die and we know that people sometimes kill them - and often that is for their ivory. There are all sorts of conclusions that we can draw about the economics of the ivory trade and how scarcity pushes up prices and so forth. But we do not (as yet) have a way to know what another being is thinking unless they speak to us about it (and even then, we can't be certain). We can't possibly know whether the elephants are able to deduce the stated conclusion from the available evidence. I'm not sure who you're calling an "unimaginative pessimist" - but that is an extremely rude violation of Wikipedia's No Personal Attacks rule - and I suggest that you apologize. Furthermore, answering a scientific question "optimistically" is a very bad idea - a healthy dose of scepticism is required, and the problem that there isn't a way to read the minds of elephants is hardly a matter of "imagination". We really can't know what the elephants are thinking - so we don't know whether they are intellectually capable of deducing the conclusion from the available evidence - we don't even know whether they think in ways we do - they might not care to seek a cause for these deaths. We simply do not know - and with current technology, cannot possibly know - and that's undoubtedly the correct answer to this question. Here on the reference desk, attacking another editor for the answer they give is considered rude - you may feel free to come up with a counter-argument, and I'm sure it would be carefull considered on it's merits - but name-calling isn't going to get you anywhere. SteveBaker (talk) 14:25, 24 January 2014 (UTC)

Steve, thanks for supporting my point that I was trying to make with reverse psyc. obviously we can know things. And I was not calling anyone in particular an unimaginative pessimist. But those that are would probably be the only ones who agree w/ clarity.165.212.189.187 (talk) 14:56, 24 January 2014 (UTC)

Does the bird know why the snake creeps into its nest filled with eggs?165.212.189.187 (talk) 17:45, 23 January 2014 (UTC)

• The loss (not merely reduction) of tusks by elephants is very real: see [23]. There are also certain places where tusklessness is almost universal, at least in a sex [24] those these are likely genetic drift. (Pure speculation follows ::) Still, this blogger I ran across [25] makes an interesting point: now that poaching is illegal, tusklessness seems to be increasing faster than ever. Now I think if you work out the math of the proportional increase, while mindful of the very heavy proportional toll of illegal poaching on elephants, that this is explainable in terms of direct selection. Still, I would not altogether rule out the possibility of demonstrating that elephants could somehow be sexually-selecting for a trait of tusklessness out of an 'awareness' that the tusks lead to an early death. Note that 'awareness' is not defined, at all, in any organism, and can occur at any number of levels, which may or may not be relatable to human thought. Wnt (talk) 14:31, 24 January 2014 (UTC)

Note that the elephants can (and indeed must) be selecting for less impressive tusks even if they are completely unaware of the problem. If elephants with large tusks are killed off more frequently, and earlier in life that those with smaller or slower growing tusks - then those carrying the "large tusk" genes will reproduce at a lower rate than those with the "small tusk" or "no tusk" genes. Evolution does it's thing and the tusks get smaller. It most certainly does not require the girl elephants to spurn the large-tusked boy elephants (and vice-versa) because of an awareness of the likelyhood of her babies being killed sooner. Indeed, that would assume that elephants have at least a passing understanding of genetic inheritance - which is even less likely (IMHO) than that they understand that tusk size relates to the likelyhood of humans coming to kill them.

That said, it's amazing that such evolutionary pressure could come so rapidly. Elephants remain in breeding condition for around 40 years - and the problem of ivory hunting has only been a significant impact on their population during the last 100 or so years. So only a few generations of selective breeding have occurred during that time. It seems unlikely that evolution could act so quickly on such a long-lived animal. However, the facts are the facts! SteveBaker (talk) 15:18, 24 January 2014 (UTC)

Oh no, I wasn't saying it was required - as I indicated, all that was just speculation. It's just that if you could show such an effect it would provide evidence for the OP's hypothesis. Elephants notably respond to skeletal body parts of one another after death^[26], so it isn't inconceivable they could get a clue, but definitely not necessary. Wnt (talk) 18:09, 24 January 2014 (UTC)

Lorentz transformation and Ampere's law

I have been thinking about the derivation of Ampere's law by applying the Lorentz transformation to Coulomb's law. My undergraduate physics text only treats the case of two equal currents with equal charge velocity, but I am having trouble getting the right answer for the more general case. We have two relevant articles, Relativistic electromagnetism and Classical electromagnetism and special relativity, but neither of them directly solves my problem. Here is what I have got;

Consider two parallel lines of charge a distance r apart with a charge density of Q₁ and Q₂ coulombs/metre respectively. In a frame of reference at rest to the charges, the Coulomb force between them is given by,

$F={\frac {Q_{1}Q_{2}}{2\pi \epsilon _{0}r}}$

If the charges are in motion axially (ie, are actually currents) we must apply the Lorentz transformation so that,

$Q'={\frac {Q}{\sqrt {1-v^{2}/c^{2}}}}$

and

$F'={\frac {Q'_{1}Q'_{2}}{2\pi \epsilon _{0}r}}={\frac {Q_{1}Q_{2}}{2\pi \epsilon _{0}r{\sqrt {(1-v_{1}^{2}/c^{2})(1-v_{2}^{2}/c^{2})}}}}$

Note that the velocities can be different even if the two currents are the same. This would pertain, for instance, if one conductor had a much larger cross-section than the other. The amount by which F' exceeds F is the Ampere's force,

$F_{\mathrm {m} }=F'-F={\frac {Q_{1}Q_{2}}{2\pi \epsilon _{0}r}}\left[{\frac {1}{\sqrt {(1-v_{1}^{2}/c^{2})(1-v_{2}^{2}/c^{2})}}}-1\right]$

Making the substitutions

$I=Qv$

and

$c^{2}={\frac {1}{\mu _{0}\epsilon _{0}}}$

gives

$F_{\mathrm {m} }={\frac {\mu _{0}I_{1}I_{2}}{2\pi r}}\left[{\frac {c^{2}}{v_{1}v_{2}}}\left({\frac {1}{\sqrt {(1-v_{1}^{2}/c^{2})(1-v_{2}^{2}/c^{2})}}}-1\right)\right]$

which is Ampere's law if the part in square brackets approximates to unity for small (non-relativistic) velocities. Unfortunately, it doesn't. Applying the binomial approximation

$(1+x)^{n}\approx 1+nx,\quad x\ll 1$

to the part in round brackets (I'm not showing all the detail here to keep it short) results in,

$[...]\approx \left[{\frac {c^{2}}{v_{1}v_{2}}}\left({\frac {1}{2}}{\frac {v_{1}^{2}}{c^{2}}}+{\frac {1}{2}}{\frac {v_{2}^{2}}{c^{2}}}\right)\right]$

$={\frac {v_{1}^{2}+v_{2}^{2}}{2v_{1}v_{2}}}$

which is unity when the velocities are equal but is clearly wrong - the expression goes to infinity if one velocity goes to zero. I would like to think that I have invented a new kind of motor with infinite torque, but in reality I have probably just made a mistake. SpinningSpark 12:39, 22 January 2014 (UTC)

$I=Qv$ isn't correct! The proper formula for the drift velocity is $J=\rho v_{\it {avg}}$, where J is the current density (current per unit *area*) and $\rho$ is the charge density (charge per unit **volume**). Alternatively, $Qv={I \over nA}$ where n is the charge carrier density. Not sure how to work those into your expressions, my physics is a touch rusty. MChesterMC (talk) 14:20, 22 January 2014 (UTC)

Starting from,

$J=\rho v$

which we both agree to be correct, and multiplying by cross-sectional area s,

$Js=I=\rho sv$

Since

$\rho s={\frac {Q}{s}}s=Q$

where Q is to be read as charge per unit length (a common enough contrivance in elementary textbooks to avoid having to explicitly include terms for length of the conductors) we have

$I=Qv$

as claimed. SpinningSpark 16:00, 22 January 2014 (UTC)

Sorry, but you made a wrong assumption. You can transfer from one frame of reference to another one, but you can not transfer to two frames of reference simultaneously! If charges are moving with different speeds they are in two different reference frames. So, the textbook is absolutely correct—you can only obtain the Amprere's law by frame transformation if velocities are equal. Ruslik_Zero 19:40, 22 January 2014 (UTC)

So what is the correct approach? I surely need the force between the conductors as observed in the rest frame. SpinningSpark 22:46, 22 January 2014 (UTC)

One approach that works is as follows:

So that there isn't any Coulomb force between the wires as measured in the lab frame, assume that in the lab frame, there is no net charge density on either wire 1 or wire 2. I.e., assume that on wire 1, in addition to the linear charge density $Q_{1}$ of charge carriers traveling at speed $v_{1}$ in the lab frame, there is also a linear charge density $Q_{1}^{*}$ of charges that are stationary in the lab frame, such that in the lab frame, $Q_{1}+Q_{1}^{*}=0$. Similarly, on wire 2, in addition to the linear charge density $Q_{2}$ of charge carriers traveling at speed $v_{2}$ in the lab frame, there is also a linear charge density $Q_{2}^{*}$ of charges that are at rest in the lab frame, such that in the lab frame, $Q_{2}+Q_{2}^{*}=0$.

The total force on wire 1 due to the charge densities on wire 2 is then a sum of four terms, one for each possible combination of a charge density on wire 1 and a charge density on wire 2. Each term is a Coulomb force, except that the charge density on wire 2 needs to be increased by a Lorentz factor to account for the length contraction within the charge density on wire 2 as observed in a frame in which the charge density on wire 1 is at rest. Thus, for each term, the Lorentz factor for the term depends on the relative velocity between the two charge densities involved. The total force per unit length on wire 1 as measured in the lab frame is thus:

$F_{m}={\frac {1}{2\pi \epsilon _{0}r}}\left(Q_{1}\gamma _{12}Q_{2}+Q_{1}\gamma _{10}Q_{2}^{*}+Q_{1}^{*}\gamma _{02}Q_{2}+Q_{1}^{*}\gamma _{00}Q_{2}^{*}\right)\ ,$

where

$\gamma _{ij}={\frac {1}{\sqrt {1-(v_{i}-v_{j})^{2}/c^{2}}}}\ ,$

and for convenience we're defining $v_{0}=0$ for the speed of the lab frame as measured in the lab frame. But since the expression for $F_{m}$ is in the lab frame, we can substitute $Q_{1}^{*}=-Q_{1}$ and $Q_{2}^{*}=-Q_{2}$ to get the simpler

$F_{m}={\frac {Q_{1}Q_{2}}{2\pi \epsilon _{0}r}}\left(\gamma _{12}-\gamma _{10}-\gamma _{02}+\gamma _{00}\right)\ .$

Doing a Taylor expansion of $\gamma _{ij}$ and ignoring terms that are more than quadratic in the velocities gives

$\gamma _{ij}\approx 1+{\frac {v_{i}^{2}}{2c^{2}}}+{\frac {v_{j}^{2}}{2c^{2}}}-{\frac {v_{i}v_{j}}{c^{2}}}\ .$

Substituting this low-speed approximation for $\gamma _{ij}$ in $F_{m}$ and simplifying gives

$F_{m}\approx {\frac {Q_{1}Q_{2}}{2\pi \epsilon _{0}r}}\left(-{\frac {v_{1}v_{2}}{c^{2}}}\right)\ .$

Making the substitutions $I=Qv$ and $c^{2}={\frac {1}{\mu _{0}\epsilon _{0}}}$ then gives

$F_{m}\approx -{\frac {\mu _{0}I_{1}I_{2}}{2\pi r}}\ .$

Red Act (talk) 07:02, 23 January 2014 (UTC)

Thanks for that, and indeed my Physics text also only treats the case of overall neutral conductors as well. It would appear that Ampere's law fails in a charged medium such as a plasma or electron beam. Is that true? The equations I derived (and yours if you put Q*₁ = Q*₂ = 0) above imply that there is a "surplus" force even if one current is zero (contrary to Ampere's law). SpinningSpark 10:04, 23 January 2014 (UTC)

Thinking about this some more, the infinities that come out of my equation are not so surprising—a simple algebraic feature. Setting a velocity to zero while requiring a finite current will result in an infinite charge density so no surprise an infinite force is needed to move them. More useful results are obtained if the expression is rearranged into the form;

$F=F_{\mathrm {e} }+F_{\mathrm {m} }+F_{\mathrm {d} }$

Where $F_{\mathrm {e} }$ is the expected Coulomb's law force, $F_{\mathrm {m} }$ is the expected Ampere's law force, and $F_{\mathrm {d} }$ is a term representing the unexplained discrepancy. I make,

$F_{\mathrm {d} }={\frac {\mu _{0}(I_{1}-I_{2})^{2}}{4\pi r}}$

for non-relativistic cases (preceded by a minus sign in the convention used by User:Red Act). This is most certainly not either a Coulomb force nor an Ampere force. Setting one current to go to zero results in a force that is dependant on neither the charge nor the velocity of the other conductor. It appears to be a self-induced circularly compressive force in the current carrying conductor and does not require another conductor for it to appear. Is there such a force? It would, for instance, tend to reduce the dispersion expected in an electron beam due to space charge effects. SpinningSpark 15:51, 23 January 2014 (UTC)

What is Abrogation?

I know the term abrogation in its colloquial and legal senses. But I see that it is widely used in scientific contexts, too, particularly in molecular biology, where it seems to refer to some kind of canceling or preventing of the expression of genes. I've Googled variously but been unable to find a decent definition or explanation of its technical nuances. Anyone resolve the mystery?—PaulTanenbaum (talk) 18:23, 22 January 2014 (UTC)

Don't have a detailed explanation, but Oxford English Dictionary (1997) gives for 'abrogate': "3. Immunol. To suppress or prevent (a physiological process)." Abrogation in this sense first attested in 1959 in Nature: "Abrogation by injected mouse blood of protective effect of foreign bone marrow in lethally X-irradiated mice.". - Lindert (talk) 20:44, 22 January 2014 (UTC)

You pretty much have it. It doesn't refer to any specific biological or experimental process in my experience, and simply refers to the state of some element, not necessarily genetic, not being present or functional. Also, as far as I am aware it is always used in practise to refer to an experimental manipulation, or a mutation, natural or otherwise, and never to a process natural to a wild type organism (for which you might use "repress" or "inhibit" instead). For example you could say "the expression of gene A was found to be abrogated in mutant B" (referring to the expression of a gene not being present any longer) or "inhibitor X was found to completely abrogate the function of protein Y" (referring to the function of a protein not being present any longer). Equisetum (talk | contributions) 11:37, 23 January 2014 (UTC)

January 23

New abiogenesis theory - needs some explanation.

This article has been making the rounds through digg and reddit today:

  https://www.simonsfoundation.org/quanta/20140122-a-new-physics-theory-of-life/

It's a proposed solution to the 'abiogenesis' problem - how did life emerge from non-living chemistry. It makes a claim that I don't really understand - and I'm hoping someone can explain it for me. The core idea here is in this quote:

"This means clumps of atoms surrounded by a bath at some temperature, like the atmosphere or the ocean, should tend over time to arrange themselves to resonate better and better with the sources of mechanical, electromagnetic or chemical work in their environments."

Clearly, if that's true - then inorganic chemistry is subject to a kind of evolutionary pressure to produce molecules that are better at pushing entropy up - and I could see how that would favor the production of things like RNA which are very good at that. But I don't understand why the statement I quoted above should be true. SteveBaker (talk) 15:05, 23 January 2014 (UTC)

Skimming the (freely accessible) linked journal article, it looks like he's taking dissipative structures, in the vein of Ilya Prigogine, and then using some other first principles to formulate a birth-death process (eq. 9), applied to an interacting set of chemical species. The analysis of which brings about this claim. Note the few paragraphs after eq. 11 in the journal article, which seems to be relevant to your pull quote. At the moment, I'm inclined to agree with another quote from the article:

" “Jeremy’s ideas are interesting and potentially promising, but at this point are extremely speculative, especially as applied to life phenomena,” Shakhnovich said." SemanticMantis (talk) 20:11, 23 January 2014 (UTC)

I haven't taken the time to fully consider the article, nor is it my field, but certainly it is an interesting idea. The blurb above makes this sound a bit like Rupert Sheldrake, but I notice that 'reson' returns no matches from the PDF, nor do I see anything to give the impression that external forces give any exceptional degree of direction to what sort of life can result. I do worry, though, that physicists have a tendency to sell us old products in new packaging. We've long known that, say, photosynthesis has a very high efficiency, something like 40% of what is theoretically possible. Is this related to the measurement made in this paper? (I'm not really qualified to say) Normally, when we see life is very efficient, we suppose it is well adapted, and even early life at some point needs to be fairly well adapted, within the limits of its simple chemistry. I should also mention that [27] is an interesting idea. I don't think the "zombie vortices" actually have a genome (though again, there's some serious math that would need to be looked at more carefully) but it is certainly intriguing to see the first tangible indication in the direction that life might have evolved on the Sun. Wnt (talk) 22:28, 23 January 2014 (UTC)

Identify object please

Can anyone identify these? They look like light bulbs but I am not seeing any wires or electrical connections. The picture was uploaded to Commons in support of a hoax on Wikipedia (now deleted). The file needs renaming as it still carries the fictitious fungus name these were supposed to be, but this is certainly no fungus! SpinningSpark 15:23, 23 January 2014 (UTC)

To me, It looks like a bunch of door-knobs that someone has hung in a tree as a wind chime. APL (talk) 16:21, 23 January 2014 (UTC)

Agreed that they look like door knobs. But, if it was uploaded as an April Fools' Day prank, there doesn't need to be any other reason for them to be on the tree than that. StuRat (talk) 16:58, 23 January 2014 (UTC)

The description actually said: "All of the above information is theoretical and intended for use in a science-based art project. All ideas and images are my own." Nil Einne (talk) 20:29, 23 January 2014 (UTC)

I read that too (just before I deleted it), but I fail to see how that helps identify it. SpinningSpark 12:47, 24 January 2014 (UTC)

My reply was indented at StuRat because I was replying to StuRat. StuRat said 'But, if it was uploaded as an April Fools' Day prank, there doesn't need to be any other reason for them to be on the tree than that' and APL said 'someone has hung in a tree as a wind chime'. While neither of these can be ruled out as possibilities (although I'd note that the image was uploaded quite a few days after April Fools' Day so was either very late or intended for this year), we have information coming from the uploader that it's a 'science-based art project' which suggests it could be neither (and that even the uploader is acknowledging that it's not a real fungi) but StuRat is correct that 'there doesn't need to be any other reason for them to be on the tree than that' even if the 'that' may not be what they suggested.

In terms of the question, I agree they look like door knobs. I was a little suprised by the colour, but a quick search suggests perhaps they aren't that uncommon. Either way, since the file had already been renamed and there didn't seem to be any remaining dispute, it didn't seem that important to mention.

It's disappointing someone would try this even if they did include a disclaimer making it clear the fungi is fictional and I'm grateful that you dealt with this. And while I'm sorry if you feel this is distracting from you question, if that's your concern I also don't really understand why you would need so many people to say the same thing for something which doesn't really matter anyway (if they aren't door knobs does it really matter? It's not like anyone is really that likely to use the photo relying on the identification and if absolutely necessary the description could always be altered saying it's only probable these items are door knobs or something similar).

Since the issue came up (not started by me) from people who were trying to help, I thought it helpful to offer some clarification they may not have seen of the possible reason for these objects being on the tree.

Note that as emphasised by APL's post, this does actual help with identification. If you think they are supposed to represent something other than a weird 'science based art project' fungi, you may unneccesarily limit the possibily of what they could be. Similarly to the April Fools' Day suggestion, once you appreciate that they could easily be there for no reason other than a weird 'science based art project' supposed to look like a fungi and apparently partly being carried out on wikipedia, the only real limit is what is available to someone carrying out such a project.

Nil Einne (talk) 14:11, 24 January 2014 (UTC)

What I take to be the previous name, Caeruleos Bulbus, is Latin for "blue bulb", according to Google Translate. They look kind of like glass doorknobs, but the bolts look more like what you would find on a drawer-pull. As to what it's "supposed to be", it actually looks kindof like a cluster of pale-blue grapes. We can't tell the exact scale of this work, so it makes analysis a little difficult. ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:41, 25 January 2014 (UTC)

January 24

Interplanetary travel

In Kerbal Space Program, players have put together this map, showing the delta-V required to travel between the planets and moons of the Kerbal solar system. There's also this calculator for finding launch windows.

I can't seem to find a similar map or tool for the real solar system. Does anyone know of one? I'm very curious, for example, what the minimum delta-V is to get from Earth to Mars using the Interplanetary Transport Network. --140.180.241.138 (talk) 03:17, 24 January 2014 (UTC)

From what I remember, once you're out of Earth's gravity well, getting to Mars can be done with close to zero energy, if you don't mind taking millions of years to get there. It's theorized that Martian meteorites got here that way. 50.0.121.102 (talk) 08:53, 24 January 2014 (UTC)

This is equivalent to the Kerbal map for Earth and Mars. I think it is based on Hohmann transfers, like your map, not the ITN and other delta-V reducing techniques. Katie R (talk) 12:44, 24 January 2014 (UTC)

Apparently, the same authors have made a delta-v map of the real solar system. You can view it here. Some of it's shortcomings are discussed here where the NASA trajectory browser and how to use it is also discussed. Obviously, NASA is a rather more reliable source for this information if you are actually planning to make that journey. SpinningSpark 13:11, 24 January 2014 (UTC)

mermaid morphology

Mermaids are mythical creatures with the top half of a human and the bottom half of a fish. However, I noticed that while depictions of mermaids show scales like a fish, the tail is oriented like that of a dolphin (that is, moving up/down (like a dolphin) rather than side to side (like a fish)). Anyone know why there is this inconsistency? I would think that even before any particular scientific classification of the animal kingdom people would be able to tell the difference between a fish and an aquatic mammal. 173.35.158.194 (talk) 03:20, 24 January 2014 (UTC)

They're often portrayed as sitting on a rock, and generally as human-like as possible. Clarityfiend (talk) 04:04, 24 January 2014 (UTC)

"Fish" has not always had the strict definition it now has. At one time it simply meant any animal that lived exclusively in water. Hence, eating beavers in Lent, when the only animal allowed to be consumed is fish, has traditionally been allowed for Catholics (in the days when hunting and eating beavers was considered acceptable). SpinningSpark 04:10, 24 January 2014 (UTC)

Agreed. In Moby-Dick (1851), Melville takes up the best part of a chapter rehearsing the various arguments as to whether a whale is a fish or a mammal, and finally comes to the conclusion that it is a fish. Alansplodge (talk) 11:19, 24 January 2014 (UTC)

I think the up/down tail is influenced more by the way humans swims, or might swim if they had a tail, see monofin. It would be very hard, near impossible, for a human to swim with a side to side motion. Disney has also played a large part in fixing the mermaid representation. Representations of mermaids prior to the widespread ability to swim amongst people do not always follow this pattern. SpinningSpark 04:25, 24 January 2014 (UTC)

Have a look at this mermaid - very fishy! Alansplodge (talk) 13:17, 24 January 2014 (UTC)

• See Sirenomelia. Your mistake is in thinking mermaids are a fiction! :) [though I recall that article having a better picture of an otherwise healthy-looking infant ... so far I didn't find it in the history. I ought to write up some python app to run through all the history revisions and extract every image ever posted to an article. Wnt (talk) 14:14, 24 January 2014 (UTC)

Where you looking for File:Sirenomelia2.jpg? I won't actually post it here so readers who don't want to be grossed out don't have to look at it. Gross-out warning for the present article as well. SpinningSpark 15:50, 24 January 2014 (UTC)

I suppose it comes about from the thought that human hips and even, perhaps, knees would be present in the mermaid - that would certainly require the movement of the tail up and down rather than side-to-side - and that in turn means that the tail flukes would have to be whale/dolphin-like rather than fish-like. Remember that some cultures believed that the skeletons of large marine mammals like the manatee and dolphin were really mermaid skeletons. Also, note that some varients of the mermaid myth give them two "tails" - appearing as scaley legs, each tipped with a fin that looks like a diver's flipper. SteveBaker (talk) 15:43, 24 January 2014 (UTC)

This is probably the answer, for the most part anyway.

If you assume that your mermaid has human-like hips, (Necessary for 'sexy' mermaids) then the tail has to be oriented like a dolphin's for the whole thing to "work". (Especially for animation. Disney has probably contributed a lot to the modern mermaid imagery.)

Functional mermaid costumes actually used for swimming are pretty much required to have the flipper move front-back like dolphins, a human couldn't move her legs left and right like a fish.

Less human, Non-'Sexy' mermaids, like the fiji mermaid have all kinds of tails. There's some images in the Mermaid article. APL (talk) 16:50, 24 January 2014 (UTC)

There's a lot more diversity in mermaids that what you describe. As mentioned above, some have more "fish" style tails, and the cetacean/true fish distinction is not that old. For examples of mermaids that don't fit your description: the famous Starbucks mermaid has two tails, or a split tail:[28]. Some mermaids have fish tops and human bottoms, like this classic Magritte [29]. You also might be interested in this WP user's article on the "Mermaid problem" [30]. SemanticMantis (talk) 16:55, 24 January 2014 (UTC)

René Magritte would hardly be expected to portray anything "normal" or "standard", or even the least bit functional. All his work is pretty much the antithesis of all those things. SpinningSpark 17:28, 24 January 2014 (UTC)

Sure, but he wasn't the first to depict mermaids that way, and my main point is that there isn't just one canonical mermaid, there are many depictions of this fantastical creature. SemanticMantis (talk) 17:51, 24 January 2014 (UTC)

Human brain question.

Does the human brain work best in pictures? There are phrases such as "a picture is worth a 1000 words" and our society seems to be full of pictures, diagrams, charts etc. However some people are very good with numbers or words. Others are good at reasoning and logical deduction. I know there are alot of articles and research around different types of intelligence and ways the human brain works but is there something which is common for all human brains? For example, do all human brains work best with pictures? Are all other types of intelligence, such as those I've listed just an addition to that? Clover345 (talk) 03:32, 24 January 2014 (UTC)

We have a very capable visual system and images are able to represent a large degree of data (depending on situation). Beyond that, though, I'm not exactly sure what it would mean to think in pictures as opposed to something else; at least, not in any way that's rigorous enough to attempt an answer. As for the idiom "a picture is worth a 1000 words", I think it's very subjective and very contextual: a picture of starving children will be more compelling than any description of starvation, a diagram of a machine will, probably, be more clear than a description, etc. However, there's plenty of things that we can't picture, or that pictures would mislead us about, mathematics and physics abound with these (picturing an atom usually ends up as imaging a small solar system, that is quite misleading, but also quite hard to avoid - etc.). Vision is a powerful method of presenting information/ideas, but it isn't the only one, nor do I think it is the sole primary one; again, it's a matter of what the idea is and who you are presenting it to. --Note: I have no citations and am approaching your question from a loose concept of "thinking in pictures", I'm sure there are more precise senses and answers, thus, if you had something more narrow in mind, just disregard this:-)Phoenixia1177 (talk) 06:00, 24 January 2014 (UTC)

You basically answered your own Q, some people think best in pictures, some don't. People blind from birth, for example, probably don't think in pictures. StuRat (talk) 06:47, 24 January 2014 (UTC)

In terms of raw bandwidth, our eyes are by far the fastest way to get data into our brains. Audio signals top out at around 40kHz, touch, taste, smell, balance, pain, proprioception and thermal senses have speeds in the tens of bits per second - but our eyes can pull in millions of pixels worth of data at tens of frames per second. There is also much more brain matter handling vision than sound or any of the other senses. That's why diagrams can generally convey data much more rapidly than the other options. SteveBaker (talk) 06:49, 24 January 2014 (UTC)

I think your ears are operating at the Nyquist rate :) . Humans generally are around 20-22 kHz (with good hearing at age before iPod.) --DHeyward (talk) 16:11, 24 January 2014 (UTC)

Perhaps he's sending separate signals to each ear. Doubling the data rate. APL (talk) 16:58, 24 January 2014 (UTC)

Nobody's eyes can "pull in millions of pixels worth of data at tens of frames per second". 84.209.89.214 (talk) 23:39, 24 January 2014 (UTC)

Re other types of intelligence, yes, empathy or emotional intelligence to use the buzzword of a few years back. 50.0.121.102 (talk) 09:09, 24 January 2014 (UTC)

Also known as the "Hurray! Everyone's a winner!" buzzword. --DHeyward (talk) 16:11, 24 January 2014 (UTC)

A human may stroll through a forest and catch sight of an ear and a striped tail projecting from the undergrowth. A person inclined to logical deduction would infer the probable size of a hypothetical creature that bears the ear and tail, then would seek in memory knowledge about known creatures of matching size, colour and habitat; that would be followed by estimations of the abilities of the candidate creatures to cause him harm; eventually he would gauge his need to carry out a life-protecting strategy such as retreating along his path. In contrast, a better equipped human in that situation has a lively pattern recognition i.e. "thinks in pictures". He immediately connects the (partial, noisy) evidence of the ear and tail to a vision of a tiger, which immediately stimulates his Fight-or-flight response, likely an escape requiring intense muscular effort, supported by all of the body’s systems. These scenarios demonstrate that A) the (human and animal) brain's ability to think in pictures has evolved as an optimum way to handle incomplete sensory data where any delay threatens survival, and B) the (human only) brain's trained ability to digest and develop logical deduction without emotive bias is the comparatively slow but only way that collective human Knowledge is acquired, validated and eventually preserved for generations in an encyclopedia. Educators are most effective when their teaching activates both types A) and B) of intelligence and they are less effective when learning depends on either A) alone (e.g. textbooks that are literally text-only such as language grammar books) or B) alone (videos without textual reference or formal exam). 84.209.89.214 (talk) 12:29, 24 January 2014 (UTC)

• Roughly half of the human brain is devoted to vision -- processing visual input and controlling eye movements. As Phoenix said, our visual bandwidth is orders of magnitude higher than the bandwidth of any other mode of communication we can perform. Looie496 (talk) 21:10, 24 January 2014 (UTC)

This general topic is a recurring theme on the TV series "Brain Games": How when we see something only vaguely or partially, our brain uses our previous pattern-recognition experience to fill in the gaps as best it can, and assess the situation. We're not perfect, and that tendency to fill in can sometimes lead to mistakes or failure to see other things. But it's vital for survival. ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:32, 25 January 2014 (UTC)

O2 arena london structural engineering

Is there a reason the O2 arena in london is missing seating stands on the upper tier of the front part of the arena, from a structural engineering point of view? Clover345 (talk) 12:21, 24 January 2014 (UTC)

While seats full of people would add a significant amount of weight, even more weight could be added if it's filled with standing fans, which could be packed tighter. Do we know what the intended use of that area is ? Maybe it's meant for people in wheelchairs ?

As far as structural concerns, if it has a cantilever design, as opposed to support columns at the front, then the torque created at the cantilever attachment points would be a concern, and weight at the front of the upper tier would contribute disproportionately to the problem. Do we know if it has support columns at the front ? StuRat (talk) 17:33, 24 January 2014 (UTC)

Science of steaming food

I have a food steamer, which consists of an insert full of holes, placed inside a stock pot. The steamer holds the food and the stock pot holds the water. The problem is, since the holes on the steamer insert are down the sides and on the bottom, small food items or liquids drop through the holes. I'd rather eat them than have to clean them off the stock pot later.

So, my question is, if we eliminated the holes on the bottom, and halfway up the side, leaving only holes near the top, would it work as well to steam foods ? Or, for that matter, if we eliminated the holes entirely, would the air gap at the top be enough to fill the inside of the steamer with steam ? Would it slow the steaming process down, or even stop it, for some reason ? So, let's say we reduce the open area between the two by 90%, would that increase cooking time by 10X ? (I'm guessing no, that it would make little difference.)

(BTW, those who saw my previous post on this topic know I was looking for stainless steel bowl to place in the steamer to solve this problem. I ended up using a ceramic bowl, which works, but the volume is much smaller than if I could use the entire steamer basket. I also tried Crock Pot liners (plastic bag inserts), but they were too small for my steamer basket.) StuRat (talk) 18:56, 24 January 2014 (UTC)

The problem is that without holes on the bottom, water will condense inside and fill up the steamer. Looie496 (talk) 21:07, 24 January 2014 (UTC)

Yes, that does happen, especially if I start with frozen ingredients, but I'm OK with that (also tomatoes and other foods will drain their juices). I end up with vegetable soup, with no risk of it burning, which is exactly what I wanted all along. If I make soup the normal way, I have to use excess water and/or watch it like a hawk, to prevent it from boiling dry, and I'd have to stir periodically to prevent burning at hot spots on the bottom, and burning at the waterline can also occur when using a gas stove. But this way, I can "set it and forget it". (Well, it would eventually boil dry, too, but the much larger water reservoir in the covered stock pot would take many hours to boil off.) Of course, this does create excess heat and humidity, but those are welcomed in winter. (I don't make soup in summer, I eat cold food then.) StuRat (talk) 01:13, 25 January 2014 (UTC)

I feel silly for saying something so obvious, but steamers are made for people who want their food steamed, not for people who want their food simmered. Looie496 (talk) 18:38, 25 January 2014 (UTC)

Fingers versus thumbs

I wasn't sure whether to ask this here at the Science Desk or over at the Language Desk. I settled on here. I am just curious, why is it that the thumb is (sometimes) not considered to be a "finger"? At other times, it seems that it is. I read the thumb article, which didn't really address this (unless I missed it). Thanks. Joseph A. Spadaro (talk) 20:28, 24 January 2014 (UTC)

It's always a finger. Otherwise how could we have five on each hand, and a middle one? Clarityfiend (talk) 20:31, 24 January 2014 (UTC)

Always? No, I have heard it said (many different times in many different places) that the hand has four fingers and a thumb. For whatever reason, the thumb is not "counted" as a "finger". I just wondered if there was some reason behind this? Thanks. Joseph A. Spadaro (talk) 20:35, 24 January 2014 (UTC)

According to Wiktionary, fingers are "one of the long extremities of the hand, sometimes excluding the thumb." According to the OED "one of the five terminal members of the hand; in a restricted sense, one of the four excluding the thumb." So yes, the thumb is sometimes excluded. I would have thought that it was fairly self-evident why the thumb is considered separately. SpinningSpark 20:57, 24 January 2014 (UTC)

Thanks. But, what is the "self evident" part? I obviously know how the thumb is different than the other four; the question is why would it not be considered/called a finger? Thanks. Joseph A. Spadaro (talk) 21:42, 24 January 2014 (UTC)

Because language is funny that way, which usually is a sign that humans are funny that way. Are Neanderthals human or not? Are dogs wolves or not? Are whales fish or not?Yes, I know the scientific answer.. Is a foil a sword? Pluto a planet? --Stephan Schulz (talk) 21:56, 24 January 2014 (UTC)

Good examples, especially Pluto. Joseph A. Spadaro (talk) 22:13, 24 January 2014 (UTC)

It very much depends on the context. In keyboard music, the thumb is not only a finger but is primus inter pares, as it were, being counted as Finger No. 1. -- Jack of Oz ^{[pleasantries]} 03:04, 25 January 2014 (UTC)

The thumb is the only digit of the hand that is opposable to the other four fingers, has two phalanges rather than three, has greater breadth in the distal phalanx than in the proximal phalanx and is attached to such a mobile metacarpus (which produces most of the opposability). The etymology of the word: "tum" is Proto-Indo-European for "swelling" (cf "tumour" and "thigh") since the thumb is the stoutest of the fingers. 84.209.89.214 (talk) 23:46, 24 January 2014 (UTC)

Red tomatos that are green inside

I was at local deli where they build your sandwich while you watch. I noticed that the gelatinous insides of the tomatoes (where the seeds are) were all greens and very unappetizing. What causes this? --209.203.125.162 (talk) 23:54, 24 January 2014 (UTC)

With over 7,500 varieties of tomatoes, it's entirely possible that what you saw was simply an odd varietal; appetizing is in the eye of the beholder, after all. It could also be that the tomato really was still green and only the outside of the tomato was reddened, due to incomplete "forced" ripening via ethylene gas. Matt Deres (talk) 00:14, 25 January 2014 (UTC)

Yes, forced ripening would be my guess. If the tomatoes had naturally ripened, the part by the stem would be the last part to turn red, not the interior. StuRat (talk) 01:06, 25 January 2014 (UTC)

January 25

Gravity wells

Plot of a two-dimensional slice of the gravitational potential in and around a uniform spherical body. The inflection points of the cross-section are at the surface of the body.

How is this a two-dimensional slice? Unless "two-dimensional" refers to the image itself (it's a 2D picture, not a 3D model) in the style of The Treachery of Images, I can't understand; it looks very much 3D to me. It's not simply a mistake in the image caption, since the gravity well article says A plot of this function in two dimensions is shown in the figure. If it's in relation to the 3D stuff mentioned in the article's section on relativity, could you explain (basically) how that works? I don't understand the section at all. Nyttend (talk) 00:42, 25 January 2014 (UTC)

[Sorry, this is wrong – see below] It's a two-dimensional slice of the (intrinsically) curved four-dimensional geometry, embedded in flat three-dimensional space to show that (intrinsic) curvature. The 3D embedding space is not part of the slice. Likewise, to mathematicians, a sphere is a two-dimensional object with positive intrinsic curvature. -- BenRG (talk) 01:21, 25 January 2014 (UTC)

Yes, well said. I'll just include links to embedding, topological dimension, and cross section, though the articles are a bit obtuse . In short, it's a 2d surface embedded in a 3d euclidean geometry. The information displayed in the 3rd dimension could also be encoded in a pure 2d image, e.g. with color, as in a heat map, or with isoclines, as in a topographic map. SemanticMantis (talk) 02:23, 25 January 2014 (UTC)

This is an embedding. The other image is a graph.

Erm, now that I look at it, this is not an embedding at all. It's simply a graph of the gravitational potential on a flat 2D slice of Newtonian space, with the spatial coordinates on the horizontal axes and the gravitational potential on the vertical axis. It's two dimensional because there are two spatial coordinates. The "height" of the potential could have been shown in other ways in a 2D image, as SemanticMantis said.

The second image on the right shows what I was actually talking about. The gravity well (first image) is often mistakenly presented as an embedding (second image) because they look so similar, and now I'm adding to the confusion. They are really quite different not only in interpretation but also in shape: the gravity well is a paraboloid surrounded by a hyperboloid, while the embedding diagram is a portion of a sphere surrounded by a paraboloid (but, as I said, is often not drawn that way). -- BenRG (talk) 05:00, 25 January 2014 (UTC)

Our retina's are 2D surface and our brains are very good at turning 2D images into a perceived third dimension. Whence illustrating a plane warped into a third dimension is easy to perceive even on a 2D surface of a computer screen. On an infinite 2D plane, moving in single direction will never bring you back the origin. Curve that plane into a sphere, and you end up at the starting point. We imagine that very well as our brains are suited for it. Brains are not well suited for warping 3D space into a 4th physical dimension. There is no picture to show it. I believe one of the outcomes is that the earth is actually traversing a straight path while we perceive it as an elliptical orbit. The distinction between the gravity well and general relativity seems more like a modelling issue than a distinction. Sort of like Newtonian laws and relativity. They are different but not unrelated. --DHeyward (talk) 17:47, 25 January 2014 (UTC)

TrES-2b: Gas giant without clouds?

Curious. I was reading the article on TrES-2b and I noted that it is classed as a gas giant, but it is thought to not have clouds... what other forms would this gas be taking? — Crisco 1492 (talk) 13:17, 25 January 2014 (UTC)

The article says it's without reflective clouds, which is why it's so dark. There may be non-reflective clouds. Either way, it's perfectly possible to have an atmosphere without clouds. Clouds (at least as we know them) are masses of liquid or solid particles suspended within the gas. Rojomoke (talk) 13:36, 25 January 2014 (UTC)

• Do we know of any gas giants without clouds? — Crisco 1492 (talk) 13:47, 25 January 2014 (UTC)

• While it's possible to have an atmosphere without clouds, as on Mars (at least part of the time), I'm not sure it's possible to have a gas giant without clouds. That's because there is so much atmosphere, even a very small percentage of particles in suspension will be visible as clouds.

• For comparison, consider liquid water. A thin layer of water may or may not be clear, depending on the amount of particles in suspension. However, water that's miles thick is never completely clear. (Yes, water has a faint color all it's own, but even without that, I don't think you'd be able to see through water that's miles thick, due to the particles in suspension, unless that water was distilled in a lab.) StuRat (talk) 16:56, 25 January 2014 (UTC)

Converting motor to generator

The motor

Hello-

I am trying to convert a mechanical fan motor to a generator. Where should I go from here?

Thank you, Seattle (talk) 15:27, 25 January 2014 (UTC)

Figured it out, but advice here would be helpful anyway. Seattle (talk) 18:27, 25 January 2014 (UTC)

A good place to go is the article Electric motor where you can identify the principle of your motor. It does not appear to be a PM DC motor which is the only type that can be simply driven as a dynamo. If your purpose is to charge a battery or to power low-voltage lighting, the article on car alternators may suggest a better choice. 84.209.89.214 (talk) 19:16, 25 January 2014 (UTC)

BCAAs positive or negative affect on health

The article on BCAAs is confusing to me. It reads to me like BCAAs negatively impact health. My specific question would be in regards to the ALS paragraph that states in the article a link between excessive BCAAs and ALS, while a quick amount of referencing I've done from other website indicates BCAAs may be used to TREAT ALS. I'm no doctor or expert, but I feel like this article is leading and does not contain full accurate information on this suppliment. — Preceding unsigned comment added by 174.71.15.179 (talk) 18:15, 25 January 2014 (UTC)

This is about branched-chain amino acids. That is a poorly written article, like many on Wikipedia. Unfortunately it would take somebody who knows more than I do to improve it. Looie496 (talk) 18:44, 25 January 2014 (UTC)