Wikipedia:Reference desk/Archives/Science/2011 December 20

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December 20

T of E

Do we need to discover all of the fundamental laws of physics before we can come up with a ToE or once we have a ToE, we will discover other fundamental laws? (this shows i have little to no knowledge about this topic). MahAdik _usap 01:14, 20 December 2011 (UTC)

What is fundemental? Science develops models, which are more complex the more accurate they become. All models are, of course, incomplete, and several of our best models work well for their own domains, but either omit some major factor, or are mutually incompatable. For example, quantum theory is not entirely compatible with general relativity, mainly over what to do with gravity. The whole idea behind a theory of everything is to marry the very accurate and experimentally verified predictions of quantum theory with the very accurate and experimentally verified predictions of relativity, and to do so in a way that incorporates gravity, perhaps through some form of quantum gravity. My understanding of these issues is purely secular, however, perhaps one of the physics experts who frequent here could correct me or expand a bit. --Jayron32 03:27, 20 December 2011 (UTC)

Finding out everything about the universe then formulating a theory from that would be tricky. To stop people simply inventing just so stories about the universe (e.g. "the planets orbit because they are attached to huge glass shells", or "because they are the gods flying across the sky", or "because angels carry them"), a theory has to be able to predict something which can be tested in the lab, and which will not be seen if the theory is untrue (this idea is called Popper's falsifiability criterion). If you've already discovered everything about the universe, then what new predictions can a theory of everything make? To some extent, string theory is stuck with this problem at the moment. Some versions of it predict all the same things that relativity and quantum mechanics do... but the only new things it predicts are too rare to find anywhere in the universe, too small to detect at the moment or need too much energy to produce in a particle accelerator. It won't be a valid theory of everything unless we can make it do something new and unexpected. Smurrayinchester 15:26, 20 December 2011 (UTC)

Discovering ToE (and, more generally, the process of discovering fundamental laws) is an example of induction. We collect a certain number of facts about the way the universe works, then theoretical physicists go to work and come up with 100 different theories that could possibly generalize and explain these facts, and these 100 theories make 100 different sets of predictions. Then we keep collecting more and more data, and some theories are ruled out and some are strengthened by additional evidence, until only one stands. And, from that theory, we can deduce other laws of nature.

If we knew all the fundamental laws, it would probably be very easy to build a ToE. If we knew exactly how many elementary particles there were and what masses they had and how they interacted with each other, we could write a theory that explains all that. But we're limited by the power and the sensitivity of tools that we have. So we have to speculate and to formulate theories based on incomplete data.

A good example is Standard Model. It contains 17 elementary particles (subject to nitpicking over what constitutes a distinct particle and what doesn't). At the time when it was formulated, scientists knew about 9 of them. Theoretical physicists managed to formulate a theory that explained all existing data and predicted that there would be more particles (which couldn't be observed at the level of technology in the mid-70's.) In the 30 years that followed, experimental physicists confirmed that the theory correctly predicted a wide range of events and brought the number of confirmed particles to 16 out of 17. There are probably 100 different extensions of the Standard Model out there, but we don't have enough data to say which one is right and which ones are wrong.

Building a theory of everything would face a similar challenge. We know a lot about the spectrum of particles up to 10^10 electron volt, but there are good reasons to think that there are many, many more between 10^10 eV and Planck mass (10^28 eV), and we have no idea what they are or what properties they have. It would take a combination of ingenuity, hard work, and luck to formulate a ToE that correctly explains everything we already know, as well as predicts things that we don't know yet. The more we do know, the easier the task of "guessing" the right ToE becomes.--Itinerant1 (talk) 02:04, 21 December 2011 (UTC)

One more point that probably didn't come across clearly. You need a certain critical mass of knowledge in order to go to the next level. Standard Model simply couldn't be discovered in 1930 or even 1950. Einstein spent the last 30 years of his life working on the theory of everything. He failed, because neither Einstein nor 100 Einsteins could even formulate the Standard Model based on the knowledge of the fundamental laws of physics as it existed in 1930. On the other hand, once the necessary pieces were in place in 1970, it was mostly a matter of luck that determined who'd make the next step (and end up getting a Nobel Prize.)--Itinerant1 (talk) 10:14, 21 December 2011 (UTC)

Efficacy of toilet tank tablets?

I have searched without success for a wikipedia page about these items. I'm talking about the large tablets you can place in your toilet's tank, which are meant to clean it and often turn the water blue to let you know that it's still around and not fully dissolved. 2000 Flushes is a well-known American brand. Do these things actually accomplish anything? or are you literally flushing your money away? I ask because they seem to be only infrequently used by Americans, and I would expect that if benefits were obvious then they would be more widely adopted... The Masked Booby (talk) 01:32, 20 December 2011 (UTC)

In the UK they're generally called toilet blocks, which on Wikipedia redirects to Toilet rim block, although that article also mentions the cistern (tank) blocks you are asking about.

Ours also come in clear and green, and occasionally purple (although the cheap purple ones I most recently bought from the 99p Shop leave a purple film in the bowl and inside the cistern, so I don't recommend them).

Apart from any supposed hygienic properties, they may also impart a faint, pleasant odour to oppose those niffs usual to toilets, and the colouration of the water can camouflage any sub-aqueous stains on the porcelain, or even "skid-marks" if one has neglected to deploy one's toilet brush. They're sold here in all supermarkets and all shops specialising in household goods, though the displays aren't enormous, so they're evidently widely but not universally deployed by Brits. As to USA usage, I can't speak: doubtless someone else will. {The poster formerly known as 87.81.230.195} 90.193.78.5 (talk) 02:19, 20 December 2011 (UTC)

"Pleasant". Hmm. Matter of taste, I guess. Or maybe you just meant, pleasant relative to the other smells likely to be in play. --Trovatore (talk) 02:24, 20 December 2011 (UTC)

Well, yes, I was being relative. I mean, I don't go out of my way to sniff them for the sheer sensual gratification. {The poster formerly known as 87.81.230.195} 90.193.78.5 (talk) 02:31, 20 December 2011 (UTC)

I use the clear ones in my toilet (the kind you drop into the tank), and I can tell within days after they have run out because a pink ring starts to form inside the bowl. Drop a new biscuit in the tank, and the pink ring goes away. So it does do something useful. --Jayron32 03:20, 20 December 2011 (UTC)

In my experience the really cheap ones just turn the color of your water, slightly pricier ones contain chlorine bleach, which does make a difference. Beeblebrox (talk) 17:33, 20 December 2011 (UTC)

Also these are discouraged , because they prevent people noticing blood in there urine and feces. 114.75.145.172 (talk) 20:43, 20 December 2011 (UTC)

That sounds like an over-reaction - who said that? Blood in urine/feces would show up fairly well against the pale green, yellow, or blue, particularly in comparison to those who never clean their trousers. --Colapeninsula (talk) 10:15, 21 December 2011 (UTC)

Some types of these blocks will gradually plug up the small jets under the rim of the toilet bowl, leading to poor flushing. There have also been cases of the cleaner in the toilet tank water gradually degrading the seal between the toilet tank and the bowl assembly, leading to a serious leak with potential to cause flooding. --Srleffler (talk) 18:24, 22 December 2011 (UTC)

Technology trees

In this article, an archaeologist argues that a technology tree cannot accurately represent Bronze Age or earlier history, since almost any technology would be found to have sometimes predated its apparent prerequisites. Does this hold true for later periods of history as well? Does it affect the validity of critical path analysis (even in a modified form that takes acceleration into account) for planning and forecasting real-world research on the grand scale? NeonMerlin 03:42, 20 December 2011 (UTC)

Technology trees can't accurately model the development of any modern technology. The idea that one technology leads to another in a nice, linear fashion doesn't really work (i.e. telegraph leads to telephone leads to the internet). See the work of James Burke (science historian), especially his landmark work Connections (TV series), which takes a more nuanced approach to the development of technology. Tehcnology trees, like shown in the article, work well for strategy computer games, but that's a game, and a game like Sid Meier's Civilization series is no more like actual history than chess is like medieval warfare. --Jayron32 04:11, 20 December 2011 (UTC)

Agreed. Looking at the illustration at the top of our technology tree article, I see many false assumptions. Just looking at the earliest 2 levels:

1) They say a code of laws requires an alphabet. Why can't simple laws be passed down by word-of-mouth ?

2) They say map making requires an alphabet. Why not just a picture map ?

3) I'd say ceremonial burial is more a result of mysticism than a cause of it.

4) Masonry is a prerequisite of mathematics ?

5) Polytheism requires horseback riding ?

6) Currency requires bronze working ? StuRat (talk) 04:27, 20 December 2011 (UTC)

That's off a video game though (FreeCiv), accuracy is not the primary goal of that particular tech tree. The goal of that tech tree is to "balance" the gameplay so that no set of reasonable choices has a clear advantage over the others. APL (talk) 06:10, 20 December 2011 (UTC)

That's what the archaeologist says in the article, which is all about that particular tech tree (or at least, the tech trees from Civ 1, Civ 4 and Civ 5, which are all similar). I don't think there are any tech trees that are made with serious intent instead of being part of games - if there are, the (Wikipedia) article ought to mention them. One amusing aspect of the Civ 1 tech tree is the innovation "democracy", which leads to only one other innovation, "recycling", which is a dead end.  Card Zero  (talk) 14:20, 20 December 2011 (UTC)

Oh, I didn't realize that. Serves me right for responding without reading the linked article. APL (talk) 01:08, 21 December 2011 (UTC)

Considering some 19th century technological inventions: I expect photography was a delayed discovery. Photography could in principle have emerged long before the actual 1830's, since the camera obscura with a convex lens to gather much more light than the earlier pinhole camera, dated to the mid 16th century , and could have pointed out the optics for a photographic camera, and silver nitrate dated back to the 13th century. Even with imperfect fixation, an artist could have made a photograph in a few minutes of exposure, then used it back in the studio to make an "accurate" painting or drawing of a person or building, before it faded. The phonograph was similarly a delayed invention, since the parts and media could have been made any time after fine brass instruments and clockwork music boxes could be fabricated. By contrast, the airplane needed lightweight engines, as well as insights into control surfaces and fluid flow, and likely could not have emerged much earlier than it did. Electronics (vacuum tubes) cold have emerged about 20 years earlier than they did, since Thermionic emission in a light bulb with an extra metal plate was discovered and reported in 1880, but not exploited as a diode until 1904. Electricity (electromagnets, telegraph, motors, lights) was somewhat delayed, since "The History and present State of Electricity" (1767) by Joseph Priestley and other mid 18th century writings discussed current flow causing wires to glow (from Leyden jars). The electrochemical cell could have been invented in by 1780 when Volta was already experimenting with electricity, accelerating all of 19th century electricity discoveries by about 20 years. Radioactivity's discovery was not the culmination of some laborious process, but an accidental discovery, which could have come along many decades earlier, since the pitchblend and photographic media or electroscopes were around many decades earlier. Edison (talk) 16:36, 20 December 2011 (UTC)

Quibble: photography was not a "discovery". It does not "exist in nature". It was an "invention". There's a lot of difference between the two. It wasn't like photography was out there just waiting around for people to come up with it. (Unlike radioactivity, which existed whether people were looking for it or not.) Also, you might find David Hockney's book, Secret Knowledge, and interesting read, with regards to the (perhaps very) early use of various types of optics in making art, if you haven't seen it... --Mr.98 (talk) 01:39, 21 December 2011 (UTC)

Counter quibble: One might argue that photography does in fact "exist in nature." One morning, there was a light snow or frost in the ground on the West side of the house, on an overcast day. In the morning, the clouds parted for a half hour and a beautiful replica of the outline of rooftops was created when the sun burned away the snow in the lawn not blocked by the roofs, before the clouds again obscured it. It was visible for hours afterward. It was a natural photograph or photogram. Edison (talk) 03:14, 21 December 2011 (UTC)

Counter counter quibble: that's not really what anyone means by photography, and has nothing to do with the invention of photography. It's interesting, though. --Mr.98 (talk) 00:25, 22 December 2011 (UTC)

Interesting quibbles. Perhaps we may say that the properties of optics (e.g. Edison's example above) and the properties of silver nitrate were discovered. What was invented was a mechanical scheme to make a camera. To further confuse the issue, we can say that it was discovered that a certain scheme would produce a functional camera. In some ways, this is similar to the question "Is math invented or discovered?" According to the bright folks at ANL, the answer often essentially "yes." [1] :) SemanticMantis (talk) 15:02, 21 December 2011 (UTC)

It's not quite as deep as the "is math invented" question, which has deeper philosophical issues associated with it. (Whether mathematical truths exist outside of human heads is a big, deep question that people still fight over to this day. Most mathematicians and philosophers consider a mathematical proof to be the ultimate definition of "truth". Many philosophers, and especially cognitive scientists, beg to differ.) There are some areas where the discovery/invention line is very blurry, but I don't think photography falls into that. It's a combination of specific understandings (optical and chemical and mechanical) into a tool that does specific work. That is pretty squarely an invention to me. One doesn't think of an MRI scanner as a "discovery," even if it is reliant on knowledge of nuclear magnetic resonance. The deeper question is whether nuclear magnetic resonance is a discovery or an invention. Most folks would class it as a discovery without too much thought. Many historians and philosophers would argue that it was an invention under certain definitions of invention. I've even heard of people try to come up with silly words to indicate discovery/invention as a singular activity. Again, a deep, often contested question. --Mr.98 (talk) 00:25, 22 December 2011 (UTC)

Winter effectivity????

Dear friends, I have few queries.Can some of u pls solve my queries: 1. Why does our body wants "more food and less water in winter than summer"? 2.Our body shivers in winter...is it an instinct activity of body to shiver,thereby produce friction and heat? pls clarify my queries... — Preceding unsigned comment added by Challenging arjuna (talk • contribs) 09:03, 20 December 2011 (UTC)

1. Because among our ancestors, those that had the reverse inclination were less successful at surviving and didn't have enough children, and so their genes for "less water in summer" and "less food in winter" were not passed to us.

2. It is not only winter, it is any cold temperature. We can shiver in a fridge and on a cold summer night, see our article shivering: "the shivering reflex is triggered to maintain homeostasis."

--Lgriot (talk) 09:35, 20 December 2011 (UTC)

1) Sweating in summer causes us to lose more water, which in turn makes us want to drink more, to avoid dehydration. We burn more calories in the winter to maintain our core body temperature, which causes us to become hungrier, so we will replace those lost calories. StuRat (talk) 21:57, 20 December 2011 (UTC)

These are great questions. I just want to add to above - the oddness that you seem to be indicating is that one needs more calories and less water - but a main function of water is to make digestion reactions possible. However, the amount of water needed to sweat is much much greater than that needed to digest 25% more food.

In case you were wondering, shivering or any activity with continuous movement is how we can use our calories to get extra heat - basically, while burning calories gives us the energy to fire our muscles, it produces a lot of extra heat. When we're too warm, we dissipate that heat by sweating. However, it's not the water in the sweat carrying away our body heat, but instead the evaporation of the sweat makes an opposite reaction (called endothermic) to the one used in firing muscles (exothermic), so the surrounding heat is actually absorbed as water evaporates leaving behind a cold spot. Of course, full detail is in the linked articles, but I enjoyed this question very much so felt it was worth giving my own summary. SamuelRiv (talk) 17:36, 22 December 2011 (UTC)

Thanks a lot for all the above for spending your time and solving my query

                         -Regards,

Blood variation according to region???

Dear friends, I have few queries.can anyone of u pls solve it: 1.Why do people in high altitudinal regions have more litres of blood than people at lower altitudinal places? -Regards — Preceding unsigned comment added by Challenging arjuna (talk • contribs) 09:06, 20 December 2011 (UTC)

First we should ask: "Do people living at high altitudes have more liters of blood than people at low altitudes?" A cursory search doesn't reveal that to be the case. However, people at high altitudes do have more red blood cells (and correspondingly less blood plasma) than those at low altitudes. The "why" is likely tied to the reduced partial pressure of oxygen at high altitude. — Lomn 16:20, 20 December 2011 (UTC)

The wrong answer that I've seen over and over is that people in high altitudes have more red blood cells because there is less oxygen, so they increase red blood cells to try and absorb more of the little oxygen that is available. Even at 2 miles above sea level, the amount of oxygen in the air is very much the same as as sea level. What changes is air pressure. With less air pressure, the transfer of oxygen into the blood cells inside the lungs is decreased. It turns out that our bodies have made use of air pressure to push oxygen into our blood. To handle this problem, the heart will initially beat faster, but then more red blood cells will be produced. Also, more tissue is created in the lungs to help in the transfer of oxygen to the red blood cells. More red blood cells doesn't really mean more blood, but it is very possible for someone to read it that way. -- kainaw™ 16:26, 20 December 2011 (UTC)

Actually, in the troposphere, gases are well-mixed, and the amount of oxygen per unit of air changes in direct proportion to the air pressure. In other words, the oxygen concentration is not reduced, but the oxygen partial pressure is. --Stephan Schulz (talk) 16:42, 20 December 2011 (UTC)

As Stephan Schulz explains, it depends greatly on what one means by "less oxygen", or "the amount of oxygen in the air is very much the same as as sea level". If you take a sample of air at sea level and a sample of air at the top of a mountain, both samples will contain (roughly) 20% oxygen. On the other hand, if you look at a liter of air at sea level and a liter of air at the top of a mountain, the mountaintop sample will be at lower pressure and less dense—each liter of mountaintop air will contain less oxygen, by mass, than a liter of sea level air. (Per Stephan, the partial pressure will be lower.)

To a reasonable approximation, the transfer of oxygen into the blood – that is, the binding of oxygen to hemoglobin – depends only on the partial pressure of oxygen. The other gases present in air aren't required to (and don't act to) 'push' the oxygen into the blood; the oxygen is 'pushing' itself, and it isn't 'aware' of the other gases' presence. You can see this with patients receiving supplemental oxygen via nasal cannula or through an oxygen mask in a hospital. Even though the gas is delivered at very nearly the same total pressure as the air in the room – if it weren't, it would blow the mask off, or pop the cannula out – it contains a higher partial pressure of oxygen, and so oxygenates blood more effectively. The phenomenon is even more dramatically demonstrated in a space suit. Typically, they're operated at only a third of an atmosphere of total pressure, with an internal gas mix that's about two-thirds oxygen—this gives about the same partial pressure of oxygen as we have at sea level and allows the astronauts to breathe normally. TenOfAllTrades(talk) 18:21, 20 December 2011 (UTC)

To the layman like me, it does sound like it's just a fancier way of saying "there is less oxygen"; which I always took to mean: "fewer oxygen molecules around (fewer air molecules around to be precise)", and never "the relative ratio of oxygen in the air is lower" which would imply there's more of "something else", (CO2 or nitrogen or whatever). Great infobit about the space suit btw, I did not know that.. Vespine (talk) 03:13, 21 December 2011 (UTC)

Thanks a lot for all the above who spend their time for solving my query

                       -Regards,

power amd energy consumed

will the fuel consumed equal for completing a given work for two engines who differ in their power? — Preceding unsigned comment added by 117.214.27.35 (talk) 09:46, 20 December 2011 (UTC)

Yes, assuming the efficiency is the same in the two cases. Red Act (talk) 14:08, 20 December 2011 (UTC)

For instance, a 1 HP engine operating 1 hour at 80% efficiency and a .5 HP motor operating 2 hours at 80% efficiency would consume the same fuel and produce the same amount of work as output. Edison (talk) 16:19, 20 December 2011 (UTC)

Though, in practice, efficiency is not a universal constant; it scales with engine size. To further complicate the problem, an engine whose rated maximum power is 1 HP can be used to perform 0.5 HP of work. A large engine may be more (or less) fuel-efficient if it is only required to deliver a fraction of its maximum capability. In such a circumstance, you need to be careful with definitions: are you comparing maximum rated power and efficiency, or are you only concerned with the actual power delivered by the engine? This is one reason why mileage per gallon can be misleading: the exact same engine may yield various different fuel-consumption rates depending on driving habits. Nimur (talk) 23:46, 20 December 2011 (UTC)

It would not be surprising if a larger engine were more efficient than a smaller one, or that an engine might be less efficient when operating at a fraction of its rated power. But I specified the case of equal overall efficiencies. (Mileage may vary). Edison (talk) 03:06, 21 December 2011 (UTC)

Lagrangian when contact forces are involved

Hi, After reading the wikipedia pages and also other literature on Lagrangian and Euler-Lagrange equations, I am unable to understand how Lagrangians are formulated when contact forces are acting on a system, like when a person is pushing a free body forward, how is that fact reflected in the Lagragian for that free body, since it has only the kinetic energy and potential energy terms. Any information on this would be helpful.Thank you.Gulielmus estavius (talk) —Preceding undated comment added 18:21, 20 December 2011 (UTC).

The contact force is formulated as a "residue" or "residual", placed on the right side of the Lagrangian equation. An entire chapter is dedicated to this treatment in Marion/Thornton, Classical Dynamics....

If you prefer, nothing stops you from treating the contact force as the gradient of a potential field (one that happens to have very difficult geometry, even in generalized coordinates). In that case, you can roll the contact constraint into the potential energy term of the Lagrangian. Nimur (talk) 18:08, 21 December 2011 (UTC)

How many bones in the ear are there?

Hi, I would like to know: How many bones in the ear are there? — Preceding unsigned comment added by 84.229.231.86 (talk) 19:05, 20 December 2011 (UTC)

See the article Ossicles. --Jayron32 19:34, 20 December 2011 (UTC)

Is it true that all redox reactions involve hydrogen in some form?

Topic says it all. ScienceApe (talk) 20:26, 20 December 2011 (UTC)

No, oxidation and reduction can occur without hydrogen being present. Plasmic Physics (talk) 21:20, 20 December 2011 (UTC)

The opening paragraph of Redox gives the example of "the oxidation of carbon to yield carbon dioxide (CO2)". Vespine (talk) 21:21, 20 December 2011 (UTC)

What about rapidly occurring oxidation reactions like fire? Do they all involve hydrogen in some form? ScienceApe (talk) 21:44, 20 December 2011 (UTC)

Surely there are some things that burn even though they contain no hydrogen? What about the same example of carbon, for instance? Or magnesium? 86.181.170.34 (talk) 22:02, 20 December 2011 (UTC)

Gun powder :2 KNO₃ + S + 3 C → K₂S + N₂ + 3 CO₂. Not an extremely simple reaction, unquestionably "rapidly occurring" and no hydrogen there either. Vespine (talk) 22:30, 20 December 2011 (UTC)

It seems to me that the question would have made more sense if it was about oxygen instead of hydrogen but even that wouldn't be true. Dauto (talk) 22:53, 20 December 2011 (UTC)

Really? can you give an example? The redox article states "in which atoms have their oxidation state changed". How could they have their oxidation state changed with no oxygen? Vespine (talk) 23:10, 20 December 2011 (UTC)

Duh! Should have read just a bit further down in examples of redox reactions, H
₂ + F
₂ → 2 HF. So it's more specifically about donating and/or stripping of electrons, rather then anything specifically to do with oxygen. Very good, carry on. Vespine (talk) 23:19, 20 December 2011 (UTC)

And for the double-whammy, Ca + F
₂ → CaF
₂. This oxidation reaction contains neither oxygen nor hydrogen. Our article explains the etymology of the term "oxidation" - it's a bit confusing. Historically, oxidation was first discovered only in relation to reactions involving oxygen. Now we use the term "oxidation" in a more general sense. I would call it abuse of notation, but it's so commonly used that it's probably not going to disappear. Nimur (talk) 23:51, 20 December 2011 (UTC)

Geosynchronous orbit

Hi, Geosynchronous orbit says:

"In the general case of a geosynchronous orbit with a non-zero inclination or eccentricity, the ground track is a more or less distorted figure-eight, returning to the same places once per solar day."

Is this correct, or should it say once per sidereal day? 86.181.170.34 (talk) 21:45, 20 December 2011 (UTC)

It seems to me that sidereal day would be the correct one here. Dauto (talk) 22:50, 20 December 2011 (UTC)

Thanks, I'll change it... 86.181.170.34 (talk) 22:57, 20 December 2011 (UTC)