Wikipedia:Reference desk/Archives/Science/2013 March 26

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

March 26

recycled paper

I went to an office supply store tonight to get paper for my printer. In their store brand, they had regular paper, 30% recycled, and 100% recycled. Otherwise the descriptions were pretty much the same. The 30% recycled cost somewhat more than the regular paper and the 100% recycled cost nearly twice as much! Does using recycled paper really cost them that much more? If so, is recycling paper economically feasible? We recycle paper, plastic, glass, CFBs, batteries, and old electronics - is any of it worthwhile economically? Bubba73 ^{You talkin' to me?} 00:41, 26 March 2013 (UTC)

You've ignored the other half of the pricing equation, which is demand: are people willing to pay more for recycled paper. If they are willing to pay more, they will be charged more, regardless of what it costs to make. That is, a company will not charge less for a cheaper product if people are willing to pay more for it. Companies aren't in the business of making less money. --Jayron32 00:45, 26 March 2013 (UTC)

Perhaps you are right, but if recycled paper cost them less, they could charge the same for it and make more money. Of course, probably not, if they can get away with it. Bubba73 ^{You talkin' to me?} 00:58, 26 March 2013 (UTC)

The idea that they could charge the same for it and make more money isn't borne out by the evidence. If they could make more money by charging less they already would be doing that. The Price point for any product is a heavily researched concept, and one that retailers are constantly studying and experimenting on and gathering data about. It isn't random in any way, this is pretty much the major thing that ALL retailers do CONSTANTLY (at least, if they want to stay in business). The evidence that they are maximizing their profit at a particular price point is that the price point has remained consistent across time and space: The fact that all retailers use such price points (recycled paper is more expensive in nearly all stores) and it has pretty much always been that way. If you want to understand how pricing works, look at the pricing of bottled soda. A 2 liter bottle of Coca-Cola in a grocery store runs between $0.99 and $1.50; a 20 ounce bottle of Coca Cola in the same store, but being sold in the cooler by the checkout line is between $1.59 and $1.79. Why? Because will pay that. Obviously, the smaller bottle of soda is NOT more expensive to produce. The price of an object is very tenuously tied to the cost of producing it. The production and distribution costs set the floor for the price, but there is no ceiling at all: the ceiling is the price that will maximize profits. --Jayron32 02:27, 26 March 2013 (UTC)

If using recycled paper cost them less than regular paper, then they could charge the same price and make more off the recycled paper than the regular paper. Bubba73 ^{You talkin' to me?} 02:34, 26 March 2013 (UTC)

Why? If they can charge more and make more money with lest customers (that is, if the increase in revenue from customers who will still buy the paper at the higher price offsets the lost revenue from the customers that won't) then why would they charge less? That would make them less money. Look, consider these example, just making up numbers. Lets say that regular paper costs $1.00 per ream to make, and they sell it for $5.00 per ream. That's $4.00 per ream in profit. Let's, for the sake of argument, say that recycled paper costs $0.90 cents per ream and they sell it for $5.50 per ream. That's $4.60 per ream in profit. Now, lets say that 1000 people buy the regular paper, and 800 people buy the recycled paper. That's $4000 in regular paper and $3680 for the recycled paper. Now, let's say they lower the price of the recycled paper to the same price point. Now we've lowered the profit to $4.10 per ream. Let's say that now 100 people switch from regular to recycled, so now there's 900 buying each. That's $3600 for regular and $3690 for recycled. Under the older pricing scheme, the company made $7,680 in paper sales. Under the new pricing scheme, the company made $7,290 in paper sales. So, it isn't advantageous to lower the price of recycled paper because you make less money. Real world examples are going to be more complex than this, but this at least demonstrates that lowering the price of a product to sell more of it does not always make you more money, even if that product is cheaper to make. --Jayron32 02:47, 26 March 2013 (UTC)

Maybe they can charge more for recycled paper, but if it cost them less, they don't have to. They can charge the same price as regular paper and make more per unit. And if regular paper and recycled paper are the same price on the shelf, I think more people would chose the recycled paper, which could drive down the cost more, but that is another consideration. The bottom line is if recycled paper cost them less, and they sell it for the same price, they will make more per unit on recycled paper. Bubba73 ^{You talkin' to me?} 04:17, 26 March 2013 (UTC)

... But keeping the Coke cool is more expensive. And the customer may want one that is already cold because they want to drink it soon. Bubba73 ^{You talkin' to me?} 02:38, 26 March 2013 (UTC)

The second reason, and not the first, is your answer. --Jayron32 02:47, 26 March 2013 (UTC)

So, not taking the profit motive into consideration, can a company use recycled paper cheaper than cutting down trees? And what about the other things that are recycled? Bubba73 ^{You talkin' to me?} 02:07, 26 March 2013 (UTC)

If we want to apply microeconomics to this, an assumption should be made that the higher price does in fact reflect higher costs. There isn't a lot of differentiation between various forms of the same level of recycled paper, so in the long run the price is equal to the Average Total Cost. The price of recycled paper is more expensive in the long run so the average total cost must be higher. Ryan Vesey 02:26, 26 March 2013 (UTC)

Not necessarily. See my example above about bottled soda. The price will, of course, be affected somewhat by costs, insofar as no company will sell an item at a loss. HOWEVER, if a company can charge more for a product and make more money, they will. 1) If the potential loss of some customers at the higher price point is offset by the increased revenue from the customers who are willing to pay more, companies will charge the higher price. This has nothing to do with costs. 2) Some products actually sell better (i.e. move more units) at higher price points. Premium pricing involves using artificially high prices to increase the "stature" of a product and thus sell more units to people who buy it only because it is expensive. That is, lowering the price of such a product would actually move less units because people will have the perception that lower price = lower quality. This ALSO has nothing to do with actual costs. --Jayron32 02:30, 26 March 2013 (UTC)

The bottle example above isn't analogous. When you're dealing with pop, you're dealing with monopolistic competition where firms are price setters rather than price takers. When you're dealing with paper, you're in a perfectly competitive market and firms are price takers. If they refuse to accept the price decided by the market, their product will not be purchased. In the perfect competition, the long run price is at Average Total Cost so the only deciding factor in the long run price is changing costs. That being said, this is a bunch of economic bunk and requires a way of thinking that doesn't necessarily mesh with reality. Ryan Vesey 02:38, 26 March 2013 (UTC)

Yes, most people want a particular brand of soft drink. I don't know of any brand loyalty when it comes to a ream of paper for the printer, but there probably is some. Bubba73 ^{You talkin' to me?} 02:40, 26 March 2013 (UTC)

Anybody who doesn't believe that prices will rise to what consumers are prepared to pay, and doesn't believe in premium pricing just needs to look at few good examples:-

• I worked for a while in a building next door to the Nevada Shirt Company (now driven out of the market by cheaper Asian product), and got to know some of the girls working there. They were into a form of badge egineering, that is, they made much the same shirts using the same material on the same machines, but with several different brands and logos sewed on. Obviously the cost per shirt to the factory was the same in all cases. Some some logos were cheap brands eg Glo-Weave and some were more premium brands like Piere Cardin. The price you paid for a shirt in retail shops reflected the brand image.
• Some years ago, I was shown around a razor blade factory (to learn about their quality control). They made two lines - a cheap line and a premium line. The only difference was the branding on the blades, and the wording and colours on the packaging.
• In the 1970's, Mercedes cars sold small but steady numbers of cars here in Australia, for about 3 times the cost of a Holden (local GM variant roughly equivent to Chevy). But it was a MUCH better car, lasting about twice as long, 4-wheel independent suspension, full function heating and aircon, very quiet and many other features the Holden didn't have. Worth it if you could afford it. By the 1980's though, GM/Holden had caught up, and today Holdens last just as long and have all the features of a Merc. So what did Mercedes Australia do? They substantially increased their price, thus reinforcing the concept of exclusivity and something you can have because you are better than the ordinary peasant. It worked - their sales increased. It's a bit sad that GM's Australian division have never made such a good product as they do now, yet sales are falling - due to brand perceptions.
• Up until the 1970's pretty much all clothing sold in Australia was made in Australia, protected by an import tarrif. In 1974 there was a change in Federal Government, and the newly elected Govt (Labor Party) ended the tarrif protection, on the theory that it was causing high prices by preventing overseas competition. Somehow they thought that local manufactuers would improve their act under competivive pressure. Didn't happen. What happened is retailers started importing direct from cheap Asian suppliers (who sewed on the same brands and logos), rapidly forcing all the local manufacturers out of business. Did the retailers lower prices because they paid less money to factories? Of course not! People were accustomed to paying so much for a shirt, pants, or whatever, and the retailers kept on charging that much.

Wickwack 58.164.230.22 (talk) 03:11, 26 March 2013 (UTC)

All very good examples. Thanks for providing those. --Jayron32 03:18, 26 March 2013 (UTC)

This is elementary economics (not "a bunch of economic bunk"), and I'm surprised that nobody has linked to supply and demand. In particular, look at the first graph on the article, which illustrates exactly the scenario we're talking about. At any given price, consumers will want to buy a certain quantity of paper, given by the demand curve D1. At any given price, suppliers will be able to produce a certain quantity, given by the supply curve S. The intersection of D1 and S gives the price and quantity of paper exchanged in the economy.

Now, consider what happens if suppliers decide to sell recycled paper instead. If it costs the same as normal paper to produce, S wouldn't change. But consumers are more willing to buy recycled paper because it helps the environment, so at any given price, quantity demanded goes up. The demand curve shifts right, from D1 to D2, and intersects S at a higher price. Therefore the price of recycled paper is higher, even if the cost of production is equal. --140.180.254.209 (talk) 03:46, 26 March 2013 (UTC)

You're dealing with the short run. If firms are making profits, more firms are going to enter the market increasing supply. The price will be reduced. Again, long term price in a perfectly competitive market is dependent on ATC. Ryan Vesey 03:49, 26 March 2013 (UTC)

He's also dealing with a simple two-class market, comprising of only sellers and buyers. Real markets aren't that simple - theres's usually at least one layer of middle men, and often more. Take my example of Australian clothing prices above. Asian factories entered the market, which might be expected to drive prices down. They did, but not at the retail level - the shops just simply took a greater profit, knowing what the consumer was accustomed to pay. Economic/pricing theory is a bit like psychology - there's a bit of sound theory, but you are dealing with human buyers, and humans often don't do rational things. Like those who buy a $120,0000 Mercedes when a $35,000 GM/Holden is just a good, technically - but the GM doesn't say to the neighbours "look at me - I draw such a good salary I can waste it on image." Mercedes increased their sales by substantially increasing their prices. If GM did that sales would most likely nose-dive. Wickwack 58.164.230.22 (talk) 04:09, 26 March 2013 (UTC)

All of this discussion of pricing and economics is beside the point of my question. The question is about whether or not producing paper from recycled paper is more or less expensive than producing it from regular paper. And the question applies to other recycling as well. Bubba73 ^{You talkin' to me?} 04:21, 26 March 2013 (UTC)

This isn't the most scholarly source I've ever found, but it states that the extra steps required in the production of recycled paper increases the costs. Ryan Vesey 04:29, 26 March 2013 (UTC)

(edit conflict) [1]. --Jayron32 04:30, 26 March 2013 (UTC)

Bahaha, I love it. Ryan Vesey 04:39, 26 March 2013 (UTC)

Oh, haha. Looks like Google worked well for both of us. LOL. --Jayron32 04:40, 26 March 2013 (UTC)

(e.c. I haven't read the above yet.) Here's another case. We saved up aluminum cans for a couple of years and then I took them to be recycled and got a little money. We did this twice. Both times the gas for me to take the cans to the recycle center was about half of what I got for the cans. And that isn't counting other car expense, the environmental impact, and my time and trouble. Is is worth it - economically and envionmentally?

Similarly, when we lived in the Atlanta area, the county charged people to pick up their recycling. Is it worth it if they don't get enough out of the recycled materials to pay for the cost?

Now we put things in a recycle bin which is picked up every two weeks. Can the county send one of those big trucks down my street to pick up what is probably a few cents worth of recycling at each house? And what about the environmental impact of the truck, etc? Bubba73 ^{You talkin' to me?} 04:42, 26 March 2013 (UTC)

Thanks - that link is to the point of my question regarding paper. Bubba73 ^{You talkin' to me?} 04:46, 26 March 2013 (UTC)

Another consideration with products made from recycled material is that some organizations have policies that require the use of recycled products. I used to work for a government agency which was under the directive of a law that required the use of recycled products wherever one was available. The administrative staff had to order recycled paper for the office regardless of its higher cost. — Preceding unsigned comment added by 148.177.1.210 (talk) 14:38, 26 March 2013 (UTC)

Maybe the idea is that we have to do more recycling to get the cost down to where it does pay off. Bubba73 ^{You talkin' to me?} 16:45, 27 March 2013 (UTC)

Chemical reaction and water vapor related questions

Some questions related to chemical reaction and water vapor. Feel free to answer any question.
1. Is there any method (or trick) by which one can predict what will form after a reaction? Consider the following two reactions-

          Cu + H2SO4 → 

          C2H6 + O2 → 

How can one know what product will form after these reactions?
2. Which is the most reactive metal and which is the most reactive non-metal?
3. Clouds hover in the sky (carrying huge amount of water) even when water has higher density than the air. What is the reason behind this?
4. Why does water vapor go up in the sky even when water has higher density than the air? They should remain on the earth. Yellow Hole (talk) 08:32, 26 March 2013 (UTC)

I can offer an answer on question 3. Cloud is a colloid (or mixture) of microscopic droplets of liquid water dispersed among the millions of molecules of nitrogen, oxygen and other gases comprising the air. Even though these microscopic droplets of liquid water are much denser than the surrounding air, the force exerted on each one by Brownian motion (violent impacts from colliding gas molecules) is much greater than the weight of the droplet, so the weight becomes insignificant. Any droplets that do wander out the bottom of the cloud (into air of less than 100% relative humidity) promptly evaporate so this process is invisible. If and when the interior of the cloud cools sufficiently, droplets increase in size and coallesce with others. When this process passes a critical point, large water droplets accumulate and begin falling because their weight becomes much more significant than the forces due to Brownian motion. When these large water droplets emerge from the bottom of the cloud we say it is raining. Dolphin (t) 08:55, 26 March 2013 (UTC)

.

In regard to questions such as what happens when you allow Cu + H₂SO₄ (raeacting a metal and an acid) to react, chemists learn that this is a ceratin class of reaction, and rules apply that lead you to Cu + 2H₂SO₄ -> SO₂ + 2H₂O + Cu⁺⁺ + SO4^-- at ordinary temperatures. Ratbone 120.145.20.58 (talk) 10:21, 26 March 2013 (UTC)

In regards to what happens when you react C₂H₆ with O₂, i.e., combusting a hydrocarbon fuel (Ethane in this case) the problem is a lot more complex. The rate of reaction and what results you get is very highly temperature dependent, especially at low temperatures for rate, and high temperatures for products. For complete combustion, you'd need not C₂H₆ + O₂ as you've written, but C₂H₆ + 3.5O₂ -> 2CO₂ + 3H₂O, but this will only happen at low temperatures, and does not occur in a single step, but in a multi-step chain reaction. In general, for complete combustion of a fuel CnHm into steam and carbon dioxide, you need obviously need n + 0.5m of O₂. At very high temperatures, what you will get is a misture of mostly CO, O₂, O, H₂, and H.

The combustion of hydrocarbons is not fully understood at present, though good progress is being made. An approximate answer can be made by identifying a writing the individual steps in the chain reaction, and the modified arrhenius equation coeficients (if known) for each step, and all the possible products. Then solve the set of reactions over time. As this involves a large number of non-linear simultaneous equations that don't usually converge very fast, considerable computer time is required. And I do mean considerable. Fortunately, published data for arrhenius coeficients exist for most reaction steps, more gets published as time goes on, and we are at the stage where non-critical reaction steps can be guessed and overall accuracy is still tolerable. The rate of any single step gas phase chemical reaction may be predicted by the modified arrhenious equation:-

R = a.T^b.e^[-c/RoT] [A]ⁿ[B]^m

where R is the rate, a, b, and c are constants (generally determined by measurement), T is temperature, and [A] and [B] are the concentrations (gas partial presssure) of the two reactants A and B. Ro is the universal gas constant, 8.3143 kJ/kmol.K. Constant C is often termed the Activation Energy. n and m for this application are integers corresponding to the species formula prescripts. Considerable enginuity is required to measure the constants and, just to make it interesting, they generally vary with temperature.

To give you a feel of the problem, I list below the most important chain steps for a much simpler combustion reaction, xH₂ + yO₂. For maximum accuracy 136 reaction steps need to be considered.

The products of reacting hydrogen H₂ and oxygen O₂ are-

H, H₂, O, O₂, O₃, OH, HO₂, H₂O, and H₂O₂.

In theory, there are an infinite series, but products not in the set of 9 above only occur in less than parts per million and can be ignored.

The most important reactions (out of a total of 136) between these nine products are:-

H+O2>OH+O

H+OH>H2+O

H+H2O>H2+OH

H2+O>H+OH

H2+O2>HO2+H

H2+OH>H2O+H

Using only these 6 reactions in a calculation will result in considerable concentration errors. Calculations will be within 10% over a wide temperature range if the most critical 23 equations are used. Included in the 23 equations are reactions of the form X + Y + M > Z + M where Z is a combination of X and Y and M is each of the 9 species, with different arrhenius coefficients for each species. Al these reactions proceed simultaneously at different and changing rates until equilibrium is reached.

In one sense, the case of reacting H₂ and O₂ is simple, as H2, O2 and the other 7 species are all transparent. So there is no black body absorption of light, adn no emision of light. As soon as you add carbon atoms, and carbon is an ideal black body, you get both the emission of light, and light accelerating the reactions. This can be handled by tweaking the arrhenious constants, but the problem is knowing how much tweaking is needed.

In short, to find the products of reacting a hydrocarbon fuel with oxygen, we can say what it is for complete combustion is (its steam and carbon dioxide), but if anyone says to you he can work out a practical case with a page or two of figuring, he's having you on.

Ratbone 120.145.20.58 (talk) 09:25, 26 March 2013 (UTC)

If only the end-point concentrations of the products is required, then there is another way, at first glance much simpler: You can use the technique of dissociation mathematics. This relies on the fact that any chemical system will head for relative concentrations that have the lowest energy at the given temperature. In this technique, one writes out the princple reactions between the expected products, and from them derive equilibrium reactions. Knowing the thermodymanic properties of each product (you can find them in published tables for most products, and calculate for the ones not published), you can then balance the equations. This is then an application of solving a set of non-linear simultaneous equations. The trouble comes because typically the solution converges extremely slowly. Common numerical methods don't work, giving false convergence dure to rounding error. Again you need a lot of computer time. Personally, I find that it is all too easy to make mistakes writing the equilibrium reactions, causing much waste of time solving simultaneous equations that are not valid. By contrast, the modified arrhenious method given above, while tedious, is easily checked at each step and thus proceeds error free. Ratbone 124.178.132.17 (talk) 02:03, 27 March 2013 (UTC)

.

In answer to (4), water vapor mixes with and rises up through the air because it is not liquid water but a gas, that is individual molecules darting about. Liquid density has no relavence for a gas. Any substance in liquid form (eg water pooled on the ground) has at any given temperature a vapor pressure. Molecules leave the liquid in order to establish the vapor pressure. In a sealed rigid container containing nothing but H₂O, at temperatures high enough to prevent freezing (~0 C) there will be a portion of water in liquid form and the remainder in gasseous form. Just enough will be a gas in order to establish the vapor pressure for that temperature. There cannot be a full vacuum. Vapor pressure rises sharply with temperature, so at high temperaures there will be more gasseous H₂O and less liquid in the container. In the atmosphere the H₂O molecules mix thoroughly with the air accodring to the laws of diffusion, driven by brownian motion, until low temperatures at altitude cause the water to precipitate out to form clouds. Ratbone 120.145.32.100 (talk) 11:07, 26 March 2013 (UTC)

As to number 2, it would depend on how you define "reactive", and depends on ambient conditions and what the substance is reacting with. Cesium has the lowest first ionization energy (table here), which makes it a good candidate for the most reactive metal. Below 28C, Cesium is solid and is less reactive than when it is in liquid form. NaK is also very reactive in terms of ionization potential and remains liquid down to -11C. (Both will react violently with water.) Fluorine is perhaps the most reactive non-metal, both because it has the highest electronegativity (except for neon, I suppose, but neon is inert) and because it spontaneously reacts with nearly every other element.--Wikimedes (talk) 11:39, 27 March 2013 (UTC)

Why does light follow straight line?

We have a number of proofs regarding the speed and path followed by light. My question is why does light always follow straight line and its speed in vacuum is constant? 106.215.97.55 (talk) 08:50, 26 March 2013 (UTC)

Science makes observation of the universe, and the natural world. Science rarely addresses the question why? For example, science observes that light mostly travels in straight lines; and the speed of light is constant in a vacuum, regardless of latitude, altitude etc. Theologians might be interested in speculating why it is so, but scientists are not. However, scientists are interested in making observations to find conditions under which light does not travel in straight lines; and in trying to find conditions of vacuum in which there is a discernible difference in the speed of light. Dolphin (t) 09:07, 26 March 2013 (UTC)

Actually, science continualy asks, as a famous scoffer of chocolate (http://en.wikipedia.org/wiki/Julius_Sumner_Miller once said multiple times at each appearance, "Why is it so?".

It can be proven mathematically that the speed of light in a vacuum can be calculated from the permitivity and permeability of free space, which are constants, and by other mathematical means.

In saying light travels in straight lines, what we really mean is that the wavefornt is not tilted. Tilting can only occur where there is a transition from one permitivity or permeability value to another - this can only happen if what the light is passing through is not a vacuum. Light does travel in curved lines when passing through material that has a gradient of permitivity or permeability. Ratbone 120.145.32.100 (talk) 11:48, 26 March 2013 (UTC)

I agree that the speed of light in a vacuum can be determined by taking account of the permitivity and permeability of free space, and nothing else, but that doesn't answer the question "why is it so?" Scientists have little interest in why vacuum displays this particular property. Theologians might say that vacuum is a concept created by God for the benefit of mankind, and that God dictated all the properties that vacuum will display. However, scientists are not much interested in such an explanation. Dolphin (t) 12:28, 26 March 2013 (UTC)

That's because it offers nothing, it offers no understanding. It's just saying it is because it is. What's the good of that? You can say scientists are not interested in why as much as you like - that doesn't make it right. Ratbone 120.145.32.100 (talk) 13:11, 26 March 2013 (UTC)

Saying "God made it that way" is the same thing as saying "the forces of nature made it that way." Hence, as you say, it adds no new facts. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:56, 26 March 2013 (UTC)

The problem is that people have two different things they mean when they use a word like "why". One of them is "by what mechanism did this come to be", as in "Why are the mountains on Earth located where they are?". Science can totally answer those questions. The other use of "why" is "For what purpose is it this way", for example "Why am I here?" or "Why are the properties of the universe the way they are, rather than some other way?". Those are fundamentally unanswerable by science because they don't present falsifiable concepts. Science can't give you purpose or meaning. It can tell you how things work, just not for what purpose (even if there is no purpose). Such questions must be answered by other methods.--Jayron32 16:01, 26 March 2013 (UTC)

There are no "other methods" that can discover what purpose a mountain has if it has absolutely no purpose. If something does have a purpose--for example, if an aspect of the universe was designed by an intelligent entity--that has observational consequences, and would most definitely be a scientific question. There's simply no sense in which science cannot answer "why" questions. The most we can say is that we don't have enough knowledge to answer some "why" questions, but saying they can never be answered is arrogant and an insult to future generations. --140.180.254.209 (talk) 17:35, 26 March 2013 (UTC)

There are many non-falsifiable propositions, and questions like "Why am I here?" does not have falsifiable answers. That is, even if your answer is "You have no purpose", that answer itself is nonfalsifiable, and as such, not testable. There are many nonfalsifiable things we deal with as humans all the time. Questions of asthetics or faith, for example, are not really falsifiable. That one person prefers to listen to death metal and another likes Mozart is not determined by any laws of science, and not subject to falsifiable experiments. --Jayron32 20:25, 26 March 2013 (UTC)

"You have no purpose" is most definitely falsifiable. Namely, anyone can falsify it by discovering the purpose that you were made for. The fact that we haven't falsified it as of now does not mean that it's unfalsifiable.

I don't know of any respectable biologist who would seriously argue that aesthetic preferences are not subject to the laws of science. It's not as if your brain decides to obey Schrodinger's equation when regulating breathing rate, but not when enjoying or being annoyed by music. I agree with you on faith, but most people use faith as an excuse to believe in one fairy tale with absolute conviction while rejecting slightly different fairy tales with equal conviction. Of course, all these beliefs are not just wrong; they're not even wrong. --140.180.254.209 (talk) 20:41, 26 March 2013 (UTC)

Silly me. Of course you are 100% correct. --Jayron32 21:38, 26 March 2013 (UTC)

For the first part of your question - "why does light follow straight lines" - see Fermat's principle (and note that in general relativity you must replace "straight line" with "geodesic"). Gandalf61 (talk) 13:22, 26 March 2013 (UTC)

For the first part, an alternative explanation is Newton's first law--everything moves in a straight line at constant speed in the absence of external forces. If a photon doesn't encounter anything, it moves in a straight line, just like everything else.

For the second part, see electromagnetic wave equation. From Maxwell's equations, which encompass all of classical electromagnetism, you can derive an equation that represents a wave propagating through space. The speed of the wave can be directly read off from the equation. --140.180.254.209 (talk) 17:35, 26 March 2013 (UTC)

Science could try and answer why there is something instead of nothing and why does matter and energy has the properties that it has. All the rest would follow from that. As to why, in the sense of "what for", I agree with Jayron32 above, that it's not a question science could dwell into. OsmanRF34 (talk) 18:17, 26 March 2013 (UTC)

It doesn't; it is affected by the curvature of space-time - see gravitational lensing. That said, in a localised area any curvature can hard (or impossible) to detect, and bear in mind that the thing you use to measure the straightness of a beam of light might also be curved by space-time as well. Astronaut (talk) 20:12, 26 March 2013 (UTC)

To me, the more interesting question is, "What is it about the nature of light that compels its speed to be what it is?" ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:53, 26 March 2013 (UTC)

I agree with Jayron32. His appeal to the concept of falsifiability is very persuasive. Dolphin (t) 22:01, 26 March 2013 (UTC)

That is a very valid scientific question, possibly with falsifiable consequences. For one possible answer, see anthropic principle. Basically, we don't really know, which does not translate to "we will never know", or to "it's impossible to know", or to "God did it". --140.180.254.209 (talk) 22:38, 26 March 2013 (UTC)

Some days I wonder how a particle can "know" that it is traveling in a straight line. That implies some form of interaction with the surrounding empty space that affixes a particular direction and kinetic energy. I haven't seen a satisfactory explanation of how this can happen at the quantum scale, for example. Praemonitus (talk) 02:09, 27 March 2013 (UTC)

Why not turn it around? There's nothing to tell it /interact with it to cause it to diverge. Wickwack 124.178.132.17 (talk) 03:25, 27 March 2013 (UTC)

Conservation of momentum, which follows from the fact that the laws of Nature are invariant under transations. Of course, the momentum of a system is not conserved if the system is interacting with another system, so a photon can change directions in a medium or in a gravitational field. Under a translation of only the system you are looking at with the other things present, you don't have translational invariance. But if you are locked up in a box that is completely isolated from the environment, then the result of experiments done within the box won't depend on the position of the box in space. Under this assumption it can be proved that the total momentum of a system is conserved. Count Iblis (talk) 00:04, 28 March 2013 (UTC)

Relative speed thought experiment

Hi all, Imagine 2 spaceships of about the same size of the space shuttles (to avoid quantum effects mostly). The ships both set off with two very accurate clocks which both start off at the same time t=0. The only constraint on their movement is that they both have to observe the same relative speed of each other (ie if ship A records a velocity of v then so must B at all times). The observations are also constrained by modern interpretations of physics (such as they can't record the other ships velocity instantaneously).

Under classical mechanics their clocks will both record the same times at all points. Is there a way to use relatavistic effects to make this not the case? Like is there a way to use a large mass to distort spacetime to make the clocks record different times, whilst the ships both observe the same velocities? Or a large moving third mass? Or close to light speed travel?

Thanks! 80.254.147.164 (talk) 11:14, 26 March 2013 (UTC)

One thing is noticeable that mass as well as velocity, both distort space-time. Technologous (talk) 12:10, 26 March 2013 (UTC)

Just for phrasing clarity, I'd suggest that you go with the two ships needing to remain at rest relative to each other. That's what "observe the same velocity" amounts to, and helps illustrate why you then don't have to further care about speed. But as above, mass will impact the clocks, per gravitational time dilation. The clock in the deeper gravity well will run more slowly. If your clocks and measurements are sufficiently precise, this doesn't even have to be a "large" mass. — Lomn 13:50, 26 March 2013 (UTC)

Ah that makes sense, I had forgot that relative rest is the same thing, I think I had just overcomplicated things. 80.254.147.164 (talk) 13:59, 26 March 2013 (UTC)

Product of two scalars

The product of two vectors may be scalar by dot product or vector by cross product. But when we multiply two scalars what would be the result - a scalar or a vector ? Technologous (talk) 12:05, 26 March 2013 (UTC)

A scalar multiplied by a scalar is also a scalar. Dolphin (t) 12:15, 26 March 2013 (UTC)

I was also thinking the same, but here is a contradiction. We know, Pressure(P) = Force(F)/Area(A), hence it can be re-written as F = P*A. Here, both 'P' and 'A' are scalars, but their product 'F' is a vector. So, what is your opinion about this. Technologous (talk) 13:09, 26 March 2013 (UTC)

I would dispute that force, in F=P*A, is a vector. Given a pressure P and an area A, what direction is the force acting in? Based on that information, all you derive is the magnitude of the force, i.e. a scalar. — Lomn 13:53, 26 March 2013 (UTC)

Force can be a vector if you use an area vector for the area. No contradiction here. Gandalf61 (talk) 13:59, 26 March 2013 (UTC)

This means that force in few cases could also be direction-less. Thanks for correcting me. Technologous (talk) 15:06, 26 March 2013 (UTC)

I disagree that force can be direction-less. I believe the error in the above posts is the suggestion that pressure and area in the above equation are both scalar. In the equation F=PA it is the area that is a vector. The magnitude of the vector is simply the area of the shape on which the pressure is acting, and its direction is orthogonal to the shape, and it acts at the centroid of the shape. Wherever water pressure acts on a surface, or a small part of a surface, the resulting force always acts orthogonally to the surface. So F=PA is a scalar (pressure) multiplied by a vector (area) and the result (force) is also a vector. Dolphin (t) 21:37, 26 March 2013 (UTC)

I would also disagree, but isn't it the pressure, not the area, which is a vector? Imagine a book dropped on top of a rheopectic liquid? It exerts pressure on the surface, but only in one direction.--Gilderien Chat|List of good deeds 22:54, 26 March 2013 (UTC)

No, Pascal's law says fluid pressure acts equally in all directions. Resnick and Halliday say "Pressure is a scalar quantity." I am looking at Physics by Robert Resnick and David Halliday, section 17-2 Pressure and Density. Elsewhere in section 17-2 they say "An element of the surface can be represented by a vector delta S whose magnitude gives the area of the element and whose direction is taken to be the outward normal to the surface of the element." The force delta F on an element of fluid is equal to p times delta S. Dolphin (t) 05:11, 27 March 2013 (UTC)

You need to describe this using tensors. The stresses in a material are described by the stress tensor, the pressure contributes to this via the term $p\delta _{i,j}$. The i, j component of the stress tensor is the jth component of the force per unit area exerted accross a plane that has its normal in the ith direction (so that plane divides the medium into two parts and you can consider the force that one part is exerting on the other). Count Iblis (talk) 23:45, 26 March 2013 (UTC)

men body hair

why have some men too many hair in body? what is the efficient and cheaper way to remove them?? is this way is suitable or it has some side effects?? — Preceding unsigned comment added by 14.102.26.19 (talk) 16:25, 26 March 2013 (UTC)

Bird never make nest in bare tree. ;-) Anyway our article on this is Hair removal Dmcq (talk) 16:41, 26 March 2013 (UTC)

Here's the article on Body hair. Some men have more (or more visible) than others, but I don't think there's any medical definition of "too much". thx1138 (talk) 17:29, 26 March 2013 (UTC)

There is such a thing as too much hair, Hypertrichosis, but I doubt that's what the OP is talking about. Anyway, having a lot of body hair should help you get in touch with your more distant ancestors :P 109.99.71.97 (talk) 18:01, 26 March 2013 (UTC)

The colour of your body hair can make a big difference to the perception of how hairy you are. Dark hair against lighter skin (and to a lesser extent light hair against a darker skin) can make you look more hairy. Other factors include how long the body hair is, and your age (older men just seem to more hairy). Hair can be removed by shaving and costs only the price of a suitable blade and perhaps a lubricant. Other methods cost more. Permanent removal can be expensive. Astronaut (talk) 18:55, 26 March 2013 (UTC)

Let's be honest here. The concept of "too much hair" is largely based on fashion. When I was younger, hairy chests were all the go, at least for men. Men only removed hair from their faces, and not all did that. I haven't done it since 1970. There was a brief period in the '70s when it was OK for (some) women to not shave anywhere. (Maybe it paralleled bra-burning). Current fashion for both sexes (guaranteed to change) seems to be the pre-pubescent, totally hairless look. All at a time when we are more concerned than ever about paedophilia. Go figure. HiLo48 (talk) 04:54, 27 March 2013 (UTC)

A prowl of 4chan might suggest it is not so out of fashion for men after all, though it seems files like Image:Nude_doorwaygirl.jpg are not so common. Wnt (talk) 14:22, 27 March 2013 (UTC)

whales

can a whale swollow a person?? — Preceding unsigned comment added by 99.104.97.215 (talk) 18:46, 26 March 2013 (UTC)

No, although their throats measure some inches. They are not much bigger than ours, and not in proportion to their mouths . OsmanRF34 (talk) 19:04, 26 March 2013 (UTC)

Even a sperm whale? thx1138 (talk) 19:11, 26 March 2013 (UTC)

The OP didn't say anything about eating whole, though their question might have been inspired by the story of Jonah. A killer whale is an apex predator, quite capable of killing a person and presumably eating them. That said, it is rare that a killer whale will attack a person. Astronaut (talk) 20:01, 26 March 2013 (UTC)

The story of Jonah actually says he was swallowed by a "great fish", not by a whale as such. The assumption of it being a whale is a folk extension, like the "apple" eaten by Adam, and the "three" wise men. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:46, 26 March 2013 (UTC)

Of course, at the time that was written, the distinctions between a whale (mammal) and fish were unknown. StuRat (talk) 23:42, 26 March 2013 (UTC)

I think they would know a whale when they saw one. That presupposes that the story is literally true, which I wouldn't bet the family jewels on. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:24, 27 March 2013 (UTC)

They wouldn't know a whale isn't a giant fish. That requires science they didn't have yet. To them, if it lived in the sea and swam like a fish and looked like a fish, then it was a fish. StuRat (talk) 00:52, 27 March 2013 (UTC)

Well, the point has been made that it's not possible for Jonah to have been swallowed by a whale. But a "great fish", sent specifically by God to punish Jonah, could do the trick (within the confines of the story). ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:51, 27 March 2013 (UTC)

But, if we're going to allow the impossible by saying "God can do anything", then why not just let God enlarge the throat of an actual whale ? StuRat (talk) 04:32, 27 March 2013 (UTC)

• The English term whale and the Latin for shark, squalus are cognates and the PIE root (s)k^walos is cognate with various other Eurasiatic languages, from Proto-Uralic through Eskimo-Aleut, all meaning "big fish". I remember reading that sea predators find humans generally unpalatable because of our boniness compared to fish and pinnipeds. μηδείς (talk) 01:05, 27 March 2013 (UTC)

Are you saying that it was a shark that swallowed Jonah and then spat him out? 24.23.196.85 (talk) 03:33, 27 March 2013 (UTC)

What she's saying is that there are different possible translations from the original Hebrew into English as to the exact English word or words used to describe the thing that swallowed Jonah, and either "Whale" or "Large Fish" would, from a linguistic point of view, be entirely consistent. That is, there is no distinction in the original Hebrew which would lead one to pick the word "whale" or "large fish", so whichever the translator chooses would not be constrained by linguistic concerns. --Jayron32 03:38, 27 March 2013 (UTC)

And, as I pointed out above, it's not just a case of having a common word for two different concepts. To them, a whale was a large fish. StuRat (talk) 03:45, 27 March 2013 (UTC)

Which is why they didn't have a separate word. Medeis's point is that in early Indo-European languages, there was ALSO not a separate word, which is why both Whale and Shark are cognate words: not to point out that the bible is saying that it was a shark that swallowed Jonah, but merely to point out that linguistically, different words have evolved from the same earlier word that means "large fish". --Jayron32 03:48, 27 March 2013 (UTC)

I have absolutely no knowledge of Hebrew. My point is that big fish/vs whale is not a conceptual distinction shown to be made before the modern era. Semitic is not very closely related to Eurasiatic, so the comment on (s)k^walos (*kala in PU, *iqaluq in Eskimo (if I remember correctly)) is more cautionary than informative. μηδείς (talk) 03:52, 27 March 2013 (UTC)

Our article Shark#Etymology says nothing about it being cognate with whale or anything else. It says its origin is uncertain. If you know different, you'd better update the article pronto, with references. -- Jack of Oz ^[Talk] 05:29, 27 March 2013 (UTC)

You didn't read me carefully; I said whale and squalus were cognates. I said nothing about what the word shark is cognate to, and was aware its etymology is obscure. μηδείς (talk) 16:40, 27 March 2013 (UTC)

Wow, my first mistake this century. It had to happen eventually. Thanks for setting me right. -- Jack of Oz ^[Talk] 21:10, 27 March 2013 (UTC)

I'll keep a list of every error I come acrost so you needn't trouble yourself. μηδείς (talk) 01:06, 28 March 2013 (UTC)

Whale shark problem solved. Article says they are known to "cough" things that they unexpectedly ingest. any more brain busters, kidding165.212.189.187 (talk) 13:46, 27 March 2013 (UTC)

Great info, Medeis! I should note generally though that the use of the word doesn't really mean that there was no distinction drawn. For example, we still use the term "slime mold" even though it may refer to as wide a range of organisms as are to be found in nature. Many of our common usages are polyphyletic like that, based on general qualities rather than true genetic affinity. I wonder if there is something political in the careful distinction of fish from cetacean - the notion being that those of the Moby-Dick generation might have thought of a "fish" as anything you could gaff or harpoon in the water, while many in modern times might prefer a monophyletic term to distinguish mammal from an unprotected species.

I should further add that the mouth of a blue whale is indeed enormous [2] I see no reason why someone couldn't be "swallowed" in such a cavity without being literally in the stomach. The story of Jonah itself, of course, is not consistent with any mundane interpretation - three days and nights! - but a skeptic might plausibly argue this could be an exaggeration that began with some such brief swallowing episode and subsequent rejection by the baleen plates. Wnt (talk) 14:14, 27 March 2013 (UTC)

Yes, it is only negative evidence that there doesn't seem to be any distinction inherited within the Indo-European languages that shows a common early distinction between whales as a group and fish as a group. For example, we can be sure the PIE's had separate concepts for the head and the body even if the Greek, Russian, and Italian kephali, golova, and testa and soma, telo, and corpo are not cognates. But we can be sure on positive evidence that they did distinguish consistently between dogs and wolves, given the separate PIE roots *wlk^wos and *kunos and their descendants, such as wolf and hound and lupus and canis and λύκος and κύων. (Incidentally there does seem to be a distinction between two possible Eurasiatic roots, approximately *qal- and *tik- (think squalus and ichthys) meaning "big fish" and "little fish".) μηδείς (talk) 16:40, 27 March 2013 (UTC)

OK, maybe more to the point: Is there any known sea creature that is capable of swallowing an adult human whole? ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:24, 27 March 2013 (UTC)

It's known that great whites don't swallow prey that large whole, they take chunks, so fish are out. Killer whales don't appear to do so either, they toss large prey about to soften and tear it up, and I am unaware of any case of a human having been eaten by one. Sperm whales eat giant squid, and it is unlikely they chew them. This guy from NOAA says a Sperm Whale could do so, and that sounds possible to me. But about as likely as a human trying to swallow an egg whole. The biblical story is so silly as not to merit consideration, and the fact that it is often told with the sea monster leviathan as the antagonist speaks toward the total unreality of it. μηδείς (talk) 22:51, 27 March 2013 (UTC)

It's still a reasonable question to ask. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:07, 28 March 2013 (UTC)

You mean whether a whale can swallow a person? I don't expect any reasonable person would call that a ridiculous question. μηδείς (talk) 02:42, 28 March 2013 (UTC)

The article on Jonah[3] gets into that question a bit, and pretty much answers the OP's question. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:49, 28 March 2013 (UTC)

In so far as misleading and relating bullshit to someone counts as answering him to some extent. Interesting to learn that dag is Hebrew for fish. μηδείς (talk) 03:53, 28 March 2013 (UTC)

The OP asked if a whale can swallow a human being whole. The first answer said "No" but didn't provide a source. The Jonah article has a sourced answer to the OP's question, which, while not specifically asking about Jonah, is a question often asked in reference to the Jonah story, which is why the Jonah article talks about it. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:00, 28 March 2013 (UTC)

It's a reasonable link, just not at all a good article. μηδείς (talk) 16:06, 28 March 2013 (UTC)

It looks pretty good to me. It's written in good English, and it gets into various possible origins and references to the story. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:26, 28 March 2013 (UTC)

It has a lot of "some people think" type statements and speculation, and poorly supported claims such as great whites eating people whole, which is obvious nonsense, unless you count people who win the Nathan's Hot Dog Eating Contest as eating hotdogs "whole". The simple fact is the story is an obvious myth on the level of Leda and the Swan, that no whale or fish could possibly swallow a man whole, let alone keep him alive for three days, rather than biting, crushing, drowning, and killing him within a few minutes if not much less. The question of what real beasts may have served as partial inspiration for the mythical beast the unnumbered authors and retellers of this story may have had in mind is an open one. But our article doesn't provide more than armchair analysis toward that end. μηδείς (talk) 19:14, 28 March 2013 (UTC)

That being said, we do have documentary evidence of fish swallowing prey whole.