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November 10

Image quality: 16mm versus DVD/Netflix

If one like classic movies of the 1930's through 1950's and has the option of a 16mm sound projector or a high definition flat screen showing DVDs/Netflix/OnDemand and ignoring the higher cost of obtaining 16mm films, and the higher inconvenience of storing films and changing reels, does the high definition win in terms of image quality (resolution, contrast, color saturation), or does the 16mm projection? Edison (talk) 02:54, 10 November 2013 (UTC)

It is possible to buy a digital projector today that will outcompete a film projector from 1950 on every single relevant specification: color accuracy, contrast ratio, optical geometric distortion, acoustic noise, energy consumption, ... Until fairly recently, contrast ratio was probably the only line-item on which a film projector could meaningfully outperform a digital projector.

It is possible to procure a high-definition video stored in a modern digital format that is bit-identical to the source footage. Common video compression schemes yield an output video that is nearly identical to the source video, using lossy compression, but is indistinguishable for most viewers. The bit depth, resolution, and frame rate of modern digital video systems effectively oversample images compared to the capabilities of 16mm film, so there should be no relevant information loss due to quantization from the analog format - neither in spatial resolution, nor in the gamut of each digitized pixel compared to the gamut of the optical film. Ken Rockwell has an article on digitized equivalent resolution for several types of photographic film, and the tradeoffs involved. Motion picture film is usually equivalent to a higher ISO film, so there is less reward for digitizing it at very high resolutions.

A video needs to be processed and converted professionally (or at least by a skilled non-professional) to make sure that the digitization does actually preserve all the information that is possible to be preserved. It is very easy to foul up the procedure, and result in digital video that is lower quality than its analog source. Nimur (talk) 04:05, 10 November 2013 (UTC)

Yet on reading that article the conclusion seems to be that each frame of 16 mm would need roughly 1/4 of the data of a 35 mm slide, say 30 Mb. So without any compression, a 6.4 Gb DVD would hold just over 3.5 minutes of uncompressed 16mm film. So all the rest, a factor of say 40 times, must be compression of one form or another. That is rather a lot. Incidentally I have worked for 30 years in the field of digital audio, and am always amused by claims that 'this time we've really cracked the compression problem'. I'd be interested to see the results of ABX testing on video compression. Greglocock (talk) 19:27, 13 November 2013 (UTC)

Momentum vs kinetic energy

If you apply the kinetic energy formulas you will calculate that (for example) a 6 kg projectile with a speed of 1800 m/s has kinetic energy of 10 Megajoules, enough to lift 1000 tonnes 1 meters high. But if you apply the momentum formula you will rescue that in the same conditions the projectile has a momentum of 10800 Ns enough to give 1000 tonnes only a 1/100 m/s speed, that is less than 1 mm elevation. What is the right formula (what would happen in real world)? 79.49.236.203 (talk) 03:39, 10 November 2013 (UTC)

You have conservation of energy and momentum, which means that the total momentum and energy of an isolated system will remain the same. If a body collides with another body then you need to consider the system comprising of both bodies as that is then an isolated system. If a 6 kg body collides with a much heavier 1000 ton body, then the kinetic eenrgy of the light 6 kg body will be approximately conserved. This is because kinetic energy equals p^2/(2m) and by conservation of momentum the heavy body will get a momentum of order of the ligher body, it's huge mass means that it's kinetic energy can be ignored. So, the lighter body's kinetic energy is conserved, which means that it will change direction. The heavy body will thus get twice the momentum of the ligher body. Count Iblis (talk) 04:17, 10 November 2013 (UTC)

I think the vector relationship makes the worst cast transfer of momentum to be twice the momentum of the original. (i.e ball hits wall orthogonal to it's face and the return direction is 180 degrees). Any impact at an angle will impart less momentum. This is easy to visualize as the limit of the impact angle gets shallower, there is the parallel limit where no energy or momentum is transferred - i.e. no collision). --DHeyward (talk) 06:11, 11 November 2013 (UTC)

The mistake you made, 79, is assuming that all of the kinetic energy of projectile will become kinetic energy or gravitational potential energy of the 1000 tonne object. This can never be assumed - you never know a priori where the kinetic energy is going to go. Much of it could wind up as heat, for instance. Accurately predicting the outcome of a collision based on momentum calculations requires only knowledge of what type of collision is occurring (elastic versus inelastic, and knowing that there is no splintering of objects helps). Someguy1221 (talk) 06:42, 10 November 2013 (UTC)

I assume this a collision? Momentum is always conserved and is a vector quantity. So you can calculate it two ways:

• the first way is as an elastic equation where the 6 kg projectile collides and bounces off the larger one. The vector sums of momentum before and after must be equal. It's elastic so the sum of kinetic energies before and after are equal. The 2 simultaneous equations to solve are $\,\!m_{1}{\vec {u}}_{1}+m_{2}{\vec {u}}_{2}=m_{1}{\vec {v}}_{1}+m_{2}{\vec {v}}_{2}$ and $\,\!m_{1}u_{1}^{2}+m_{2}u_{2}^{2}=m_{1}v_{1}^{2}+m_{2}v_{2}^{2}$. You know $\,\!m_{1},{\vec {u}}_{1},m_{2},{\vec {u}}_{2}$ so need to solve the simultaneous equation for $\,\!{\vec {v}}_{1},{\vec {v}}_{2}$.
• In the inelastic case, the smaller projectile sticks to the larger body and the equations to solve are $\,\!m_{1}{\vec {u}}_{1}+m_{2}{\vec {u}}_{2}=(m_{1}+m_{2}){\vec {v}}_{f}$. You solve directly for ${\vec {v}}_{f}$. After that, there will be a difference in kinetic energy. $\,\!{\frac {m_{1}u_{1}^{2}+m_{2}u_{2}^{2}-(m_{1}+m_{2})v_{f}^{2}}{2}}=lost\ kinetic\ energy$. (someone should check this, it's been a while). --DHeyward (talk) 10:32, 10 November 2013 (UTC)

I was assuming that the collusion is totally elastic and no kinetic energy is lost. I made this question mainly to know if, to know the power of a projectile, must be considered the momentum or the kinetic energy (i.e. a projectile with a speed of 400 m/s has a force twice or four times higher then another with the same mass travelling at 200 m/s?). In the case I made before, even if it's truce that normally the 1000 tonnes object wouldn't be moved, if the decelaration is higher than 1000 g, the force applied is enough to lift that weight. 95.247.218.92 (talk) 15:04, 10 November 2013 (UTC) PS: solving the equation for inelastic case, the solution is a speed of 1/100 m/s for the whole system, the same I gave for momentum. So is the momentum the right solution? — Preceding unsigned comment added by 95.247.218.92 (talk) 15:22, 10 November 2013 (UTC)

No, momentum on its own will not give you the right solution because it does not tell you how the momentum and energy are partitioned after the collision. You need to write down the equations for both kinetic energy and momentum and then solve them simultaneously. I did the maths and found that the projectile would bounce back at well over 1799 m/s. (Obviously this wouldn't happen in the real world because the collision would be highly inelastic. Real bullets are designed not to bounce!) Only 233 joules out of the original 9720000 would be transferred to the target, which is why you got such a small answer for the final speed of the target. --Heron (talk) 16:39, 10 November 2013 (UTC)

Yes, as I explained above, you only need to consider the momentum, as the kinetic energy stays (almost entirely) in the lighter body. While you can solve the equations as the other have explained to you, that may obscure the physics of this issue of why momentum and not energy is relevant here. Count Iblis (talk) 16:54, 10 November 2013 (UTC)

I now see what you mean, Count Iblis, but I'm not sure that the OP has noticed your factor of 2 (it took me a while to catch up). OP, you need to refer to Count Iblis's answer above and note the statement "The heavy body will thus get twice the momentum of the lighter body." If you solve the momentum equation on its own (p = m1v1 + m2v2), as you appeared to be doing in your original question, you will get the answer for an inelastic collision (0.01 m/s). To get the answer for an elastic collision, you need to double the target's momentum, and you will then get the correct answer of 0.02 m/s. The factor of 2 is not exact, but is close enough when the target is much more massive than the projectile. If you are satisfied with the approximation, you can forget about kinetic energy and calculate solely using momentum. --Heron (talk) 18:03, 10 November 2013 (UTC)

A projectile's KE doesn't necessary have to stay with a smaller body though. Modifying the OP's original question with some different assumptions, consider a bowling ball rolled down the lane onto and up a ramp the height of which is just enough to convert the ball's KE to PE. As it comes to a stop, it's positioned onto the upper-end of a long lever, which is simply a see-saw that pivots, on which the other end is situated a much larger and heavier ball. Because the arms of the see-saw are unequal, under the bowling ball's weight the long arm drops as this larger ball gets lifted to an equivalent PE a shorter distance at which point it gets dropped onto another ramp, such that it continues on forward down the lane with the energy of the original ball. Now due to conservation of energy we have the OP's conundrum. The short answer is, I think, that the system's momentum is still conserved due to Newton's action reaction principle, because if we allowed the larger ball to be propelled out the back of a ship, it produces more thrust (using the same energy) than had we simply thrown the bowling ball and not transferred its energy to the weight. Photons also don't make for very good propellants. Perhaps we can direct the OP to the relevant articles. -Modocc (talk) 17:27, 10 November 2013 (UTC)

Yes, this is actually a special case of impedance mismatch casing energy to reflect back instead of being tranmitted to the desired system, and impedance matching to solve this problem. In case of collisions the mass plays the role of the impedance, in electric circuits you of course have the usual electric impedance. In case of sound waves the impedance is related to the speed of sound. If you connect a transmitter to an antenna with the wrong impedance, the power will be reflected back into the transmitter which can damage the transmitter. In that case, you can still use the same antenna, you just have to put an impedance matching device between the transmitter and the antenna. Count Iblis (talk) 18:10, 10 November 2013 (UTC)

The different momentum in this case is explained by a change in the momentum of the lane (and eventually the entire Earth). The idea of the efficacy of different propellants is related to specific impulse. Photons are actually the best propellants if you count by total energy, but the worst if rest mass is free and you count by the amount "added". --Tardis (talk) 02:24, 11 November 2013 (UTC)

To be clear, in an elastic collision, all the kinetic energy that goes in is preserved somehow in kinetic energy going out. Because kinetic energy and momentum are simultaneously conserved, the usual result is that an elastic collision involves a substantial rebound! If you shoot your projectile into a block and it sticks, then it gets the feeble momentum in the projectile transferred to the total mass of block and projectile, and the rest of the KE goes into heat, noise, flying shrapnel, etc. (Well, I guess the shrapnel is elasticity rearing its head; inelastic collisions shouldn't make any shrapnel) The situation where you levitate the block a huge distance is more like if you had a bouncing bullet continually going between the block and the ground banging to push it up, and at the exact moment of collision (only) you released some kind of clamp on the block so that it was in free fall only for that instantaneous moment (since otherwise its PE turns to KE as it falls) Wnt (talk) 20:23, 10 November 2013 (UTC)

Why did lunar module dock with command module on the Apollo program

After leaving the earth orbit on the way to the moon, the command module performed a 180 degree turn and docked with the lunar module. Why was this necessary ? Why wasnt it launched in the correct configuration ? I cant find an explaination anywhere on the internet. I saw this animation on youtube, but no explaination http://www.youtube.com/watch?v=8VvfTY-tVzI Thankyou — Preceding unsigned comment added by Matboyslim (talk • contribs) 20:32, 10 November 2013 (UTC)

The Apollo Command Module was situated forward (above) of the Apollo Service Module. The simplest way to design an egress from the CM was "through the top." An equally valid question is, "why did the CM have two doors?" There are an infinite number of possible design configurations; the astronauts could have been seated anywhere during launch; but at an early stage in the program, this design was selected: the astronauts launched in the foremost compartment, and an orbital rendezvous was required. If you are interested in the very fundamental design tradeoffs that went in to the overall architecture of the Apollo Program, you might enjoy reading NASA's history archive: the Apollo Lunar Surface Journal. There is a chapter on spacecraft design. More specifically, Buzz Aldrin wrote his Ph.D. thesis on why an orbital rendezvous was the best design choice for a manned lunar mission. Nimur (talk) 20:45, 10 November 2013 (UTC)

(ec) The CSM was a separate spacecraft, which was designed to operate independently of the LM (as it did in the Apollo 7 and Apollo 8 missions). There was no need for it to launch in a docked configuration. Perhaps more importantly, launching with the LM docked would have made a mission abort rather more difficult - the CM/CSM would have had to make a 180 degree turn (possibly in the atmosphere) after an abort to get into the correct configuration for re-entry. Tevildo (talk) 20:50, 10 November 2013 (UTC)

Ultimately, the design decision was: given the natural differences between the Earth and the moon; and given the realizable technology available to American humans in the 20th century; two spacecraft were required to deal with the distinct terrestrial and extraterrestrial launch and landing requirements. Therefore, those spacecraft would require at least one rendezvous and docking operation. In Project Apollo, it was decided to use two rendezvous and docking operations. That mission profile allowed astronauts and ground crew to assure that the rendezvous and docking functioned correctly while still in Earth orbit, and to experiment with that operation on pre-Lunar flights (e.g. during the Gemini Program) instead of waiting until the end of the lunar mission to test it. Nimur (talk) 21:04, 10 November 2013 (UTC)

A minor factual correction - TD&E was performed after TLI (although that was technically still in Earth orbit, the actions necessary to go to the moon had been performed). However, I agree that an abort (or fixing a problem with the docking mechanism, as happened on Apollo 14) was much better at that stage than discovering a problem when the LM returned to the CSM from the lunar surface would be. Tevildo (talk) 21:55, 10 November 2013 (UTC)

Correlation between intelligence and sensitivity to the cold?

In humans, is there any correlation between intelligence and sensitivity to the cold? 86.171.42.209 (talk) 20:42, 10 November 2013 (UTC)

That's an interesting question. What makes you think that there might be? It's such an unlikely connection that I doubt whether anyone has done any research on it. There is certainly a correlation between age and sensitivity to the cold, and I'm beginning to wonder whether intelligence decreases with age (especially in my own brain), but remember that Correlation does not imply causation. Dbfirs 20:53, 10 November 2013 (UTC)

I've spent time in both warm and cold climates, and it's really a matter of acclimation to a given area. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:59, 10 November 2013 (UTC)

I have noticed that there does seem to be some correlation between intelligence and sensitivity to various things like that. Purely personal anecdotal though. Dmcq (talk) 00:05, 11 November 2013 (UTC)

I'm a Mensan and I thrive in cold conditions. Plasmic Physics (talk) 00:14, 11 November 2013 (UTC)

Probably due to our reduced body hair.--Auric talk 00:25, 11 November 2013 (UTC)

Reading around there does seem to be a link between autism and sensitivity to touch and cold and various things like that, and in particular it is a common complaint of those with Asperger's. I guess that might explain my feeling that there is a correlation with intelligence. Dmcq (talk) 00:33, 11 November 2013 (UTC)

And by correlation I don't mean that all or even most of one corresponds with the other. I'm simply saying in a statistical sense. Dmcq (talk) 00:40, 11 November 2013 (UTC)

What a coincidence, not only am I Mensan, who thrives in cold conditions, I'm also an Aspie. Plasmic Physics (talk) 00:53, 11 November 2013 (UTC)

The section in the article Asperger syndrome#Motor and sensory perception seems to indicate the subject has been been studied a bit but there is no general agreement on it. Dmcq (talk) 01:09, 11 November 2013 (UTC)

Are we talking about cold climates like the arctic vs. tropical, or like living in the basement? There are things that people can naturally adapt such as altitude changes will change red blood cell volume, whence the acclimatisation phase of mountaineering summit attempts like Mt. Everest as well as seasonal blood vessel changes -> people take coats off in the spring at lower temps than they put them on in the fall because the amount of blood vessels at the skin surface change to accommodate the need to radiate heat. But I believe Einstein had a wardrobe that consisted of multiple sets of identical clothes so he wouldn't have to clutter his brain with frivolous choices. Therefore, I'm going to say a moderate, unchanging climate without appreciable seasons is best so that coats, sweaters, shorts or pants decision are never necessary. --DHeyward (talk) 07:07, 11 November 2013 (UTC)

I was thinking that under this premise, the Sherpas and the Inuits must be the most intelligent peoples on earth. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:24, 11 November 2013 (UTC)

Have another go at reading the query. Dmcq (talk) 13:44, 11 November 2013 (UTC)

The OP asked "is there any correlation between intelligence and sensitivity to the cold." Have a go at explaining precisely what the OP meant. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:35, 11 November 2013 (UTC)

I'm not aware of one in humans but there is a correlation more directly between intelligence and temperature in Trolls. Equisetum (talk | contributions) 10:31, 12 November 2013 (UTC)

There do appear to be links between various psychological states and temperature (specifically aggression), this could bias one's viewpoint to a certain degree- I'm not suggesting there is an actual link with intelligence. At any rate, see [1], [2], [3], [4], [5], [6], [7], and [8] if interested.Phoenixia1177 (talk) 10:43, 12 November 2013 (UTC)

Sorry, I just reread your question; obviously, none of the above is really that applicable, still, it's somewhat related, so it may be of interest.Phoenixia1177 (talk) 11:01, 12 November 2013 (UTC)

medical condition. Brokers affasier

want to know if this is a correct medical problem.not sure if it is spelt correctly — Preceding unsigned comment added by 5.69.167.5 (talk) 21:08, 10 November 2013 (UTC)

There's an apostrophe missing in "broker's". μηδείς (talk) 21:21, 10 November 2013 (UTC)

The correct condition is "Broca's aphasia", which I see on editing Medeis has also linked, in a less obvious way. - Nunh-huh 21:35, 10 November 2013 (UTC)

Occupational precautions regarding chemotherapy

What does the "Occupational precautions" section of Chemotherapy say? Does it simply say that medical personnel in contact with chemo patients have to be careful lest they end up getting small amounts of the drugs themselves? The wording is complex and hard to follow (I've re-read it several times), and I don't at all understand the ramifications of the first half of the second sentence. Nyttend (talk) 21:48, 10 November 2013 (UTC)

That section of our article contains verbatim excerpts from this CDC website. You have paraphrased it pretty well. Chemotherapy drugs are potentially hazardous. People who handle the drugs need to be careful, avoid direct exposure, and avoid long-term indirect exposure. According to the CDC, exposure to certain anti-cancer chemotherapy drugs can cause everything from skin rashes to causing cancer in healthy people. Antineoplastic drugs are very potent chemicals.

In this instance, I use the phrase "cause cancer" because the CDC expressly states that certain antineoplastic drugs are "known carcinogens." We should be careful to distinguish "known carcinogens" from entities that are suspected to increase risk, or are correlated to cancer incidence in lab studies.

We should also probably re-write the section of this article. Nimur (talk) 21:58, 10 November 2013 (UTC)

Agreed, and what you just wrote above is perfectly clear, so we should change it to say something like that. StuRat (talk) 22:28, 10 November 2013 (UTC)

It was fascinating for me to read this question and its answers, and to look at the CDC material. There are 2 kinds of hospital here in Australia - public and private. Public hospitals are run by the Government and accept "public" patients - that is the cost is carried by the Government. The patients pay nothing. Private hospitals are run by for-profit companies, benelovent foundations, and churches and charge the patients a multitude of fees, which are mostly covered by medical insurance. Public hospitals also accept private patients - that is patients who pay much the same fee as they would in a private hospital, and in return get to choose their doctor(s), avoid waiting in queues and get extra drugs regarded as beneficial but non-essential. When my wife had her first breast cancer, she had chemo as a private patient in a public hospital. The chemo ward nurses wore standard uniforms, and handled syringes, intravenous lines, etc in the normal way. When she had cancer again in the other breast, she opted for a private hopital. The difference in care was very noticeable. One of the differences that stunned us though was that the private hospital chemo nurses, when they went to administer a chemo agent (eg inject it or connect it up to the intravenous drip) they put on, over their standard uniform, a face mask much like the mask that metal worker use to prevent metal filings from entering eyes, nose, etc) a sort of neck-to-ankle apron made of plastic, and gloves. I asked "whats all this?" and the nurse explained that it was standard mandatory safety precautions for her - contact of her eyes, mouth, or even skin with any leak or splash would be regarded as serious. Each time a nurse went from one patient to another, she took off all the safety gear, threw it in a bin, washed her hands, and put new safety gear on. We never saw any of this in the public hospital. 124.178.135.228 (talk) 01:55, 11 November 2013 (UTC)

That seems like an over-reaction, to me. I'd also guess that such gear causes more harm than good, due to obscuring the nurse's vision and having her poke herself accidentally with the needle. This is why most soldiers don't wear full body armor, as the lack of mobility and inability to see presents more danger than the protection afforded by the armor. StuRat (talk) 02:04, 12 November 2013 (UTC)

As to whether it is an overkill, I'm not qualified to say. However, given that that this particular hopital is run by a for-profit company, it is unlikely that they would incur costs not necessary. What I can say is that the nurses' vision would be unaffected by the protective mask worn. I've worn similar masks when doing metalwork, and vision is just not a problem. Also, a nurse accidentally poking herself with a needle is extremely unlikely. What is possible, is that the nurse though a muscle spasm might accidentally push the plunger causing some of the stuff being squirted out, or while working on the drip or intravenous administration pump, accidentally cause a line break, or operate the taps in the wrong sequence, either of which could possibly result in some chemo discharged. 120.145.90.77 (talk) 11:10, 12 November 2013 (UTC)

However, the economics from the POV of the company include the risk of lawsuits and, if it's a union shop, the union rules, both of which can lead to behaviour which doesn't make economic sense alone. StuRat (talk) 17:47, 12 November 2013 (UTC)

All nurses here are members of their union - that applies to both public and private hospitals. The union is mostly focussed on improving pay for nurses working in public hospitals. Lawsuit risk may well be a greater factor for private hospitals, however that will only be the case if there is a real ie case-demonstrated risk to the nurse. In Australia, an isolated one-of-a-kind accident is unlikely to pprovide success at lawsuit if the employer can demonstrate their training and gear is industry standard. Since public hospitals don't use the protective gear, a smart lawyer retained by the hospital could probably get the suit denied on that basis, unless the risk is real. See post by RmHermen below. 120.145.90.77 (talk) 00:18, 13 November 2013 (UTC)

Also, even if it was on net value, I'd bet the money spent on such equipment could improve safety more if spent elsewhere. StuRat (talk) 02:04, 12 November 2013 (UTC)

Here is a link describing U.S. practices [9] which seem very similar to those in the private hospital that you saw. Rmhermen (talk) 18:37, 12 November 2013 (UTC)

Unidentified goose (Orange County, CA)

I saw this odd-looking goose at a park in Orange County, California. It's about the size of an Egyptian Goose, and was associating with a gaggle of them. What species/breed is it? 69.111.17.141 (talk) 23:40, 10 November 2013 (UTC)

My browser gives a warning on visiting that site. μηδείς (talk) 23:46, 10 November 2013 (UTC)

Darn, sorry about that. It should be perfectly safe. But in case there's a problem with dropbox, I'll rehost the picture here. 69.111.17.141 (talk) 00:06, 11 November 2013 (UTC)

Thanks for rehosting that. If you search for "grey goose" (you have to use advanced search to exclude "vodka") you will see plenty of grey geese on google images. Indeed, geese of the genus Anser are called the grey geese. But they all seem to have orange bills, not black ones. This may be an example of partial melanism. I suggest going to Wikipedia:WikiProject Birds if you don't get a more . . . black-and-white answer . . . here. μηδείς (talk) 01:16, 11 November 2013 (UTC)

Looks like the Snow Goose, or at least the one pictured here: [10]. StuRat (talk) 01:10, 11 November 2013 (UTC)

Thank you for the feedback-- upon consulting a few different bird guides, I think what I have is an immature Snow Goose. 69.111.17.141 (talk) 01:30, 11 November 2013 (UTC)

Chronic effects of nerve agent exposure - why?

Why are the effects of nerve agent exposure long-lasting and cumulative, when nerve agents act solely by inactivating acetylcholinesterase, and therefore normal transmission of nerve impulses can resume as soon as the inactivated acetylcholinesterase is replaced? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 23:47, 10 November 2013 (UTC)

Can you give a source for this assumption? Which nerve agent(s)? μηδείς (talk) 23:50, 10 November 2013 (UTC)

I suppose (although I'm guessing) that it's not the production of the acetylcholinesterase or the acetylcholinesterase itself that's being "inactivated". It's probably blocking whatever the next step in the biochemical pathway is - and thereby preventing the acetylcholinesterase from working - even though there is plenty of the stuff in the body. If that's true, then it wouldn't matter that fresh acetylcholinesterase is being produced. But as I said, this is only a guess. SteveBaker (talk) 00:43, 11 November 2013 (UTC)

The organophosphates inhibit acetylcholinesterase, which makes the signal from acetylcholine last longer. According to [11], these somehow lead to excitotoxicity, which leads to apoptosis. There is a lot left unclear in that "somehow", both in the paper and its sources I think; I haven't looked into it deeply but there may be some important biology undiscovered there. In principle though, we can see that more signalling can do that. The link I give even specifies some compounds that can interfere with the process. Wnt (talk) 02:40, 11 November 2013 (UTC)

Guessing is the problem here. [deleted suggested answer] This also sounds like a homework or test question. μηδείς (talk) 02:45, 11 November 2013 (UTC)

It might be, and then it might not be. I think we should give the OP the benefit of the doubt in this case. 24.23.196.85 (talk) 07:19, 11 November 2013 (UTC)

That's interesting it means that medicines to protect from damage due to strokes or epilepsy for instance might help as well as ones to block acetylcholine. I guess the ones looking at protecting from nerve gases have tried all sorts of things like that though. Dmcq (talk) 14:09, 11 November 2013 (UTC)

November 11

Plastic cracking due to rapid temperature change

Some plastics can be exposed to sudden changes in temperature (e.g. +21 to -190 C) without cracking while others can't. How can I predict this? Are certain plastics or plastic additives needed? Is thickness relevant? — Preceding unsigned comment added by 78.148.107.181 (talk) 13:49, 11 November 2013 (UTC)

This has to do with several factors, among the most important of which are the plastic's thermal conductivity, ductility and tensile strength: plastics with higher values for these parameters are less likely to crack due to temperature changes. Also, adding plasticizers reduces the likelihood of cracking, by increasing ductility. And yes, thickness is VERY relevant -- a thick piece is more likely to crack than a thin piece, due to thermal shock. 24.23.196.85 (talk) 00:31, 12 November 2013 (UTC)

The biggest factor is probably the class of plastics. Thermoset plastics, like Bakelite are hard and inflexible, and likely to crack, while thermoplastics, like a bread wrapper, are soft and flexible. Also, older plastics tend to become more brittle, as the plasticizers evaporate or leach into the solid, liquid, etc., they contain. StuRat (talk) 01:55, 12 November 2013 (UTC)

Official Specs from Nissan (I don't have a Chilton book)

I'm trying to find specs for what Nissan says the thermostat opening temperature is supposed to be for a 2002 Sentra GXE. At Advance Auto's website, one with an opening temperature of 170 F says it's an exact match, but that's lower than specs I have seen from official sources for other engines and I'd like to see the temperature number Nissan itself says. I'm already getting the check engine light because my thermostat's stuck open and I'm running below optimal running temperature, and getting a themrostat that opens too soon will keep things that way. 20.137.2.50 (talk) 15:30, 11 November 2013 (UTC)

I don't have access to a reference to look up the specs right now, but you can probably get the answer with a call to a Nissan dealership's parts department. Katie R (talk) 17:49, 11 November 2013 (UTC)

Who's eating our high-energy neutrinos?

Does the failure of the IceCube Neutrino Observatory, as noted here http://www.wired.com/wiredscience/2013/11/future-physics-experiments/?cid=co14315194 indicate that something is sapping the punch of the Universe's high-energy neutrinos?

If so, could the culprit be dark matter? Hcobb (talk) 17:22, 11 November 2013 (UTC)

If Iron nuclei dominate the primary ultra high energy cosmic ray particles, then there isn't a problem. Count Iblis (talk) 18:43, 11 November 2013 (UTC)

Huh? What's the ref? Hcobb (talk) 19:19, 11 November 2013 (UTC)

See here, certain models are now ruled out. Count Iblis (talk) 13:52, 12 November 2013 (UTC)

I think it's disingenuous to say that the IceCube experiment "failed." It is an experimental apparatus, and the data that it has produced is still being interpreted. Two measurements were collected that imply extremely high energy neutrinos, but only with a low confidence (by the rigorous standards that are applied to particle physics experiments). I am not an expert in neutrino spectroscopy, but I think we should refrain from calling the experiment a "failure" just because a popular science writer glossed over the important details. The experiment has provided a lot more data than those two specific events. You can read an overview at IceCube Quick Facts; that webpage links to more technical publications, like this one that was published in PRL: First Observation of PeV-Energy Neutrinos with IceCube (2013). "These two events could be a first indication of an astrophysical neutrino flux; the moderate significance, however, does not permit a definitive conclusion at this time." That's the paper I'd be spending my time reading, if I were interested in answers - not a Wired.com article. Nimur (talk) 22:42, 11 November 2013 (UTC)

Can't really help except to say I remember SN 1987A and how excited my physics professor was. I would be reluctant to attribute anything to a measurement done on earth simply because of the lack of reactivity of neutrino's with anything. Count the number they observed for a supernova that was visible and it becomes rather difficult to apply measurement. --DHeyward (talk) 10:20, 12 November 2013 (UTC)

Storm surge timing

How long does it take for a storm surge, like the one that just destroyed Tacloban, to come ashore? In other words, how quickly does the water rise to its maximum level? I looked at storm surge but didn't see anything. --71.163.153.146 (talk) 18:53, 11 November 2013 (UTC)

Depends on how large the storm is and fast it is moving. Dragons flight (talk) 19:26, 11 November 2013 (UTC)

In the case of Haiyan, the tropical storm force winds extended about 300 km from the center, and the storm was moving 40 kph, so people would start experiencing a serious storm about 8 hours before the peak of the storm surge arrived. Dragons flight (talk) 19:43, 11 November 2013 (UTC)

• The surge from the storm moves at the same speed as the storm, but is affected by the tide and the shape of the land and any falling or rising of the storm's wind speed. In this case, if the storm was moving at 40kmph and the winds were not varying and the tide was not influential, and we ignore the shape of the coastline, the surge was moving at 40kmph. μηδείς (talk) 23:04, 11 November 2013 (UTC)

What's the reason for the large death toll? Is it because they were not adequately warned? Or were they warned but had no practical way to leave and seek higher ground? ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:30, 11 November 2013 (UTC)

A few other possibilities:

1) They may not have believed they were in serious danger. The usual logic is "I've seen storms like this before, and everyone who stayed was just fine."

2) There was significant risk to leaving. This could involve having their homes and businesses looted, having their pets starve if they can't quickly return, etc.

3) Some may have stayed for the looting opportunity.

4) They were asked to stay. This would involve emergency workers, like reporters, police, fire department, and hospital workers.

5) Some people just say "If it's my time, I shouldn't fight God's plan". This is especially true of the elderly. StuRat (talk) 01:47, 12 November 2013 (UTC)

Good points. That kind of thing happens in the US also, the mentality that they can ride it out. Those types of folks typically end up as statistics. Maybe you've heard the one about the guy on his roof, waiting for God to help him? ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:09, 12 November 2013 (UTC)

• Storm surge is determined by a combination of air pressure, wind, and tide. The wind tends to give the strongest surge north of the eye, because it pushes water ahead of the storm, but in a complicated-shaped body of water such as the one that Haiyan passed through, the wind effects are difficult to work out. The main cause of fatalities is just that this was an incredibly strong storm. The only things the US has experienced that are comparable are the 1935 Labor Day hurricane and Hurricane Camille, but both of those made landfall in relatively uninhabited places, whereas Haiyan made landfall directly on a city of over 200,000 people. Looie496 (talk) 00:02, 12 November 2013 (UTC)

Have you forgotten Hurricane Katrina??? 24.23.196.85 (talk) 00:33, 12 November 2013 (UTC)

Katrina actually weakened at the last moment and veered aside. It only hit New Orleans with a glancing blow, and was only Cat 4 at the time. The factor that caused most of the trouble in New Orleans is that much of the city is below sea level. The results were very serious, of course, but the way they happened was completely different. We got lucky -- if Katrina had hit NO directly at Cat 5 intensity, probably tens of thousands of people would have died. Looie496 (talk) 00:58, 12 November 2013 (UTC)

OP here. Here's my hypothesis, based on a direct-hit scenario: storm surge depends mostly on wind speed and air pressure, so, the surge would come ashore gradually as the wind speeds gradually increased and the eye, the area of lowest pressure, approached. It would come ashore relatively slowly, over a period of several hours, not a sudden 20-ft wall of water like a tsunami. So, even though the storm is moving at 40kph, no one got hit by a wall of water going 40kph because the water level rises gradually as the storm approaches, the wind speed increases and the pressure drops. Please correct me if I'm wrong. --71.163.153.146 (talk) 06:24, 12 November 2013 (UTC)

In general, yes, but the actual flow of water is considerably modified by the shape of the coast and the slope of the shore, hence the spectacular tidal bore effects (that can travel "faster than a galloping horse" ) where one would expect only a gradual rise of tide. Dbfirs 08:01, 12 November 2013 (UTC)

Development and duration of a storm surge can be seen by looking at historical tidal gauge data. For example, here's lower Manhattan during Hurricane Sandy. From this, we can say that a storm surge develops generally over days (note how far above normal the water level already is 24 hrs before peak) and acutely with the arrival of the storm, predominantly within a 12-hour span (though this will naturally vary with the particulars of the storm and the local geography). The surge will tend to recede more quickly than it built, but again, this will vary. — Lomn 16:24, 12 November 2013 (UTC)

Thank you, everyone, for your answers. They are all helpful, especially those by Dbfirs and Lomn. --71.163.153.146 (talk) 16:46, 12 November 2013 (UTC)

November 12

Softening Hair with Electricity

Is it possible to soften hair with electricity. I want develop a electric razor that softens hair as you shave. I am trying to replicate the condition your hair is in after a hot shower. It is well established you get a better shave when the hair softened prior blade shaving. I am not sure if TENS technology would apply in this case. Any suggestion would be appreciated174.17.240.215 (talk) 00:39, 12 November 2013 (UTC)

It seems unlikely - I think it's the heat and humidity that changes the nature of hair in the shower - which is (in part), the reason that some people have "bad hair days" in hot and humid weather (another reason is something to do with copper plumbing pipes!). You might (maybe) use mild electrical stimulation to the skin to induce the hairs to stand more upright...and I'm almost sure I recall someone selling such a thing back in the 1970's or so. SteveBaker (talk) 01:38, 12 November 2013 (UTC)

"Dr White's" was the main brand before the war - see this, for example - but I don't remember anything similar being available as recently as the 1970's. Tevildo (talk) 23:22, 12 November 2013 (UTC)

Wind force as concrete design factor

How thick concrete is needed to withstand a 100 m/s wind? I assume the force is 1/2*density*speed²=1/2*1.242*100²=6210 N and the shear strength of cement to be 6000 MPa. I get the required thickness to be 0.26 mm.. which seems wrong. Electron9 (talk) 06:49, 12 November 2013 (UTC)

It seems to me that this Q can't be answered without asking what is supporting the concrete. If it's just a 0.26 mm thick, tall concrete wall with no rebar, then it will fall over at the slightest breeze. StuRat (talk) 06:58, 12 November 2013 (UTC)

Well, think of a shed at 15 m² where human can stand. Moulded in solid concrete or cement. So it would be surrounded by other concrete to support it. And rebar is likely to be used. Electron9 (talk) 07:05, 12 November 2013 (UTC)

If the OP hsa been triggered to ask this by Typhoon Haiyan or other similar recent events, it's worth pointing out that it's not the wind alone that causes damage. It's the objects the wind picks up along the way that cause more problems. These can include roofing materials, garden furniture, bicycles, and really, anything you can think of that could be outdoors and blown by wind. So a speed calculated for wind alone is of no practical use in storm damage planning. HiLo48 (talk) 07:10, 12 November 2013 (UTC)

Something is wrong with your approach - your force seems to be independent of the area, and any sailor can tell you that's wrong. You need to take the relationship of load-bearing parts to total surface area (and indeed shape) into account. This becomes a highly non-trivial fluid dynamics problem. --Stephan Schulz (talk) 07:53, 12 November 2013 (UTC)

Concrete is usually used for its compressive strength while rebar (steel) has tensile strength. Complex and large structures have many different force relationships both static and dynamic. For smaller structures (like houses), roof is often a lifting force in winds requiring many steel straps to the foundation through other tensile structures like wooden frames. Any structure where the wind can lift it will need weight to counterbalance the lift and tensile connections to the weight to prevent it. I suspect your calculation of the shear strength didn't included the weight of the concrete itself and is a compressive, not tensile number. --DHeyward (talk) 08:55, 12 November 2013 (UTC)

Stephan Schulz, I did a miss, 100 m/s wind should exert at force of 6210 N/m². It's easy to forget such things when measurements are evaluated at 1x1 m size and compared to each other. Electron9 (talk) 16:52, 12 November 2013 (UTC)

Designing concrete walls is a heck of a lot more complicated than you have thought, Electron9. For a start, you need to start with the flexural strength, not the shear strength. In my country we have what is known as the Masonry Code of Australia, which from memory takes at least 20 pages to explain it. To put boil it down as simple as possible, for any given thickness, for wind loading alone (and as others have said there are lots of other factors) there is a maximum area that must be surrounded by more rigid structure - eg built out pillars, walls at right angles, etc. There'll be an equivalent industry Code or National Standard in your country. You should obtain a copy. 120.145.90.77 (talk) 11:21, 12 November 2013 (UTC)

I would expect the weak point to be where the concrete attaches to the ground. The wind will exert a torque on the concrete there, causing it to crack at the foundation. In the diagram below, the cracks would be expected at the plus sign:

 ->|
 ->|
 ->|
   +---

In this case, the height (but not the width) of the wall will determine the torque, along with the wind speed. Also, wind speed typically rises further above the ground, so height makes things even worse than you might think. To counter this effect, you might want to make the concrete thicker at the bottom, and avoid a sharp corner, which can cause force concentration there. Think of the shape of the bottom of cooling towers; you might want a less extreme version of that shape (it can be vertical at the top, though, unlike a cooling tower). A circular foundation versus rectangular would also help to distribute the wind loading forces more evenly. StuRat (talk) 17:11, 12 November 2013 (UTC)

Question about forces and slopes

Hi guys

Sorry if this is worded wrong.

If a certain amount of force can move a 30 kg object 20 feet along a horizontal plane, and the same force is used to move an object of the same weight, but this time up an inclined plane, is there a way to find out the angular degree in the slope that will mean that the object only moves half as far? So basicly, If a force can move a 30 kg object 20 feet, on a horizontal plane, and a 30 kg object 10 feet on an inclined plane, what is the degree of the incline? Is it possible to guess at this? Disregarding friction?

regards

Rob — Preceding unsigned comment added by 86.136.127.255 (talk) 10:35, 12 November 2013 (UTC)

See thread at RD/M here. Gandalf61 (talk) 10:55, 12 November 2013 (UTC)

(ec)If you disregard friction, then any amount of force can accelerate any object to a non-zero speed, after which it will just keep going. The question makes no sense without friction. If you include friction, you still need to talk about energy, not force - a given force will either move the object (if the force is larger than the friction) or not at all. For the horizontal plane, all your initial energy is lost to friction. You can compute the amount using the mass, the gravitational field, and the coefficient of friction. If you go up an inclined plane, you slightly decrease friction, but are also converting part of the energy to potential energy (by lifting the weight). There are too many variables to estimate this flat out - are you moving a granite block up a rubber surface, or are you moving polished steel on an ice surface? --Stephan Schulz (talk) 11:10, 12 November 2013 (UTC)

For the sake of argument you are pushing a skate board with a 30 kg child on it, on a concrete horizontal strip, then up a concrete ramp. Does that help at all

Thanks

Rob — Preceding unsigned comment added by 86.136.127.255 (talk) 12:24, 12 November 2013 (UTC)

Actually, that makes it more difficult to estimate: skateboards have wheels, so the correct model for friction is complicated. Wheels lose energy to rolling friction between the axle and the bearing. They can also slip as they roll, if traction is imperfect. Both processes are difficult to accurately model as force terms. This is even more justification for applying a method based on conservation of energy - not directly reckoning with a force. We can add a correction factor for the non-conservative work that is lost to friction. Nimur (talk) 15:11, 12 November 2013 (UTC)

I'd say where the model is difficult to implement correctly, it's best to use a trial-and-error approach to get the answer. StuRat (talk) 17:14, 12 November 2013 (UTC)

Overthinking it. It sounds like a homework problem involving force through a distance vs. potential energy on an incline. A constant force through 20 feet that is stopped being applied at the ramp of 30 degree angle will travel a certain known distance up the ramp. It's a straightforward homework problem and I don't do homework anymore. --DHeyward (talk) 05:10, 13 November 2013 (UTC)

How did addictive behaviors and procrastination evolve in families?

It is known that certain human behaviors are addictive and maladaptive. How did this behavior arise in the first place, and how come it perpetuates itself in families? Wouldn't addiction be a major turn-off during courtship? I am talking substance addiction and behavioral addiction: drug addiction, alcohol addiction, video game addiction, procrastination, etc. 140.254.229.115 (talk) 14:40, 12 November 2013 (UTC)

By and large drug addiction didn't evolve - not even opium predates agriculture to any significant degree. Other forms of addiction are beyond the ability of evolution to quantify: someone who spends days at the tribal dance or doing online gaming might find some kind of gain from that or not. Procrastination may pass up opportunities, but it also passes up dangers; the caveman who waited longest before going out to investigate the lion's kill might have been the one who lived to tell the tale! Wnt (talk) 14:51, 12 November 2013 (UTC)

It makes sense. Sometimes, the environment can change, causing certain behaviors to become malaptive in certain situations while other behaviors become more productive, and human tendencies to perform certain behaviors over others may lead offspring to do the same. 140.254.229.115 (talk) 15:14, 12 November 2013 (UTC)

For a different approach to the problem – Attention deficit hyperactivity disorder is strongly correlated with both procrastination and addiction/substance (ab)use (possibly a form of self-therapy). A well-known attempt to explain ADD as having once conveyed an evolutionary advantage is the Hunter vs. farmer hypothesis by Thom Hartmann. --Florian Blaschke (talk) 16:30, 12 November 2013 (UTC)

Is the tendency toward either ADD or substance abuse (or both) considered to be more caused by genetics, or by environment? ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:52, 12 November 2013 (UTC)

ADD has at least partly genetic causes per current consensus, but it's hard to tell which is more important; I lean towards genetic factors being slightly more important at least (of course there are factors which are outside the strict genetic–environmental dichotomy, such as in embryonal development, which can be described as innate but not necessarily genetically caused, though possibly influenced by genetic factors, despite apparent environmental causes; consider that an alcohol-addicted mother can cause harm to her child's development, possibly resulting in mental issues, while her own addiction may have biological factors contributing to its rise, for example by developping a mental instability that makes her react considerably more sensitively to setbacks – this seriously complicates things: if the child develops ADD, this may seem to be caused by the mother's alcohol abuse, but in fact the tendency towards the development of ADD may simply, or additionally, be inherited from the mother, making cause and effect hard to disentangle). Opinions maintaining that ADD is exclusively caused by the environment and should not be treated with drugs at all (not even as part of a multimodal strategy involving behaviour therapy as well) can safely be described as fringe and not supported by research. They are often expressed by authors who believe in some sort of mind-body dualism, and do not agree that mental problems can have somatic causes, often associated with the anti-psychiatry movement. I suspect that biological factors are involved in some, but not necessarily all individuals highly predisposed to addictions as well. --Florian Blaschke (talk) 17:33, 12 November 2013 (UTC)

Given the list of things one can become addicted to, it would seem to cover a significant portion of humanity. So maybe there is a natural tendency to become addicted to something. There was an old Cheech and Chong bit where they run into a guy who says, "I used to be all messed up on drugs; then I found the Lord; now I'm all messed up on the Lord." I could argue that defines Johnny Cash perfectly - when he sobered up, he embraced Christianity like a bear. Not that that was a bad thing, and I was a fan of his; but it's said that one addiction will tend to get substituted for another. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:55, 12 November 2013 (UTC)

Not all addictions are bad, at least from an evolutionary POV. An addiction to food was a healthy thing when starvation was a concern, and eating any food you could find as quickly as possible made sense. A sex addiction has the obvious evolutionary benefit of passing down more of your genes. An exercise addiction can be healthy even today. StuRat (talk) 18:03, 12 November 2013 (UTC)

A sex addiction can get you killed, or at least get you bad publicity (and sometimes cost you severely if you run for public office). ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:46, 12 November 2013 (UTC)

However you define a sex addiction, it doesn't matter if it gets you killed if it leads toward leaving more and still successful children. There's also the estimate that approximately 10% of children result from rape. See Before the Dawn for this. μηδείς (talk) 04:05, 13 November 2013 (UTC)

Note that most addictive substances aren't addictive in the natural form, it's only our ability to breed, refine, or distill them that has made them "strong" enough to become addictive and harmful. Alcohol, for example, occurs naturally in rotting fruit and vegetable matter, but not in quantities that would normally get someone drunk. Therefore, during most of human evolution, there would be no advantage to evolving genes to resist these addictions. StuRat (talk) 17:25, 12 November 2013 (UTC)

I've heard of apes in the wild observed acting drunk after eating overripe fruit, so I'm not sure your assertion is quite correct. --Florian Blaschke (talk) 17:37, 12 November 2013 (UTC)

The question would be whether they get addicted or not. That is, do they find that drunkenness so pleasurable that they become great-ape winos on a constant basis, or do they just like to get a buzz on from time to time. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:51, 12 November 2013 (UTC)

And were humans involved in the process ? So, was the fruit bred to make more alcohol, or did the apes raid a warehouse full of over-ripe fruit, for example. In nature, they are only likely to find small quantities of over-ripe fruit at a time. StuRat (talk) 17:53, 12 November 2013 (UTC)

• Talking about addiction is like talking about diabetes or cancer. Those words apply to syndromes we see as similar, but which are suites of very different diseases with many different causes, united by one salient feature--malignant tumors or high blood sugar or self-destructive behavior. That being said, things like thrill-seeking behavior might arise in a population of ice fisherman, some of whom are literally bored to death by the activity, and some of whom get a thrill when they catch a little fish every hour or so. Behaviors like that transplanted to a gambling casino might be maladaptive and called addiction. That doesn't mean their "addiction" has the same explanation as, say, alcoholism, which might arise when people whose alcohol-tolerant ancestors survived on dilute beer as a safer and more nutritious alternative than unsanitized water when those people are then exposed to cheap hard liquor like gin. μηδείς (talk) 18:10, 12 November 2013 (UTC)
  • The nature of fishing (as a recreation rather than a vocation) does not necessarily require catching fish. What it requires is a willingness to spend hours doing nothing, i.e. relaxing. I expect relaxation could be addictive too. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:48, 12 November 2013 (UTC)

I wasn't talking about fishing in a modern context, but as an example a tribe of (Arctic/subarctic) people who depend on ice fishing as a large part of their diet in the winter. (We think of arctic peoples as reindeer herders or sea-mammal hunters, but those are relatively recent developments.) In that case you do want both patient dedication and a strong feeling of reward when a fish is caught. Same with the diluted beer example, for which I had in mind Northern Europe during the Middle Ages and until the advent of modern sanitation and distillation. μηδείς (talk) 19:07, 12 November 2013 (UTC)

• Not quite. Addiction is is cured through behavioral changes. Cancer is not. To the extent that society wishes not to stigmatize the uncontrollable nature of addiction and therefore quantify it as a disease does not change the variance of onset or treatment. But ultimately, there will be no determinate reason as to why disease or addiction or any number of differences observed in human beings has not been eradicated by natural selection. The problem is that either outcome could be rationally explained by the application of the simplistic "survival of the fittest" model. If there was no addictions we would explain it as eradication through fitness and if there is, it's because certain addictions provided either an advantage or continues to evolve the species. Therefore, using natural selection as the basis is too simplistic. It's like like trying to determine if clouds will warm or cool the planet. Everyone feels the cooling effect when a cloud provides shade yet it also provides a blanket that prevents radiation at night. Clouds are complex in climate modeling. Human behavior is complex for natural selection. Indeed, it becomes impossibly complex to identify whether one person is either/or supporting natural selection. Natural selection is over many populations/generations/variables and it is pointless to identify current features/behaviors as aither an outcome of or input to future selection. It certainly never applies to an individual person or animal. The epitome of human evolution could be hit by a bus tomorrow through pure coincidence without having any meaning or input. --DHeyward (talk) 05:32, 13 November 2013 (UTC)

Assuming you are addressing me, DH, you are denying a bunch of points I haven't made. I didn't say addiction and diabetes are cured the same way, nor diabetes and cancer either. I didn't address any form of "future selection". If there were no addictions there would be nothing to explain, including their eradication. And in saying clouds may warm or cool the planet you seem to have missed I said the word addiction covers a suite of behaviors with various causes and effects, the same as the very general word cancer. But perhaps I assume wrong, and you aren't addressing anything I said. μηδείς (talk) 06:44, 13 November 2013 (UTC)

I was only directing a small part for you and the rest is in general. The only thing that was related to you was treating addiction as a "disease" akin to "cancer". That's a sociological decision rooted in perception of uncontrollable vs. controllable afflictions. There are sociological and psychological reasons for treating addiction as a disease similar to cancer but causation and underpinnings are very different. The reasons to avoid stigmatizing conditions is well understood from a treatment perspective but the science that underpins a behavioral vs. physical condition are real disctinctions. The broader point is that natural selection is often used to describe minority/majoruty behaviors or features in individual people and it's nonsense. It simply cannot be applied in the timeline that describe human history, let alone behaviors in individuals or groups. Even physical predispositions to certain conditions cannot be explained by natural selection in the timeframes of documented human history. Basically we know the the genome narrowed a long time ago and has flourished since. Attributing things like longevity or intelligence to different broad classes (let alone addiction in narrower classes) will just lead to an answer that the researcher wants to prove a hypothesis. There is literally a logical reason for every behavior. Whether it's something like "violent males" or "passive males", it's easy to make a "natural selection" hypothesis that explains why both would dominate and therefore it tells us nothing about it. Heck, they use the same type of open solution to explain chimpanzees when they describe the ability of dominant and non-dominant males to reproduce. The answer is that behavior and choices are too complex and too evolving to describe within the broad umbrella of natural selection. Nature selects diversity and this is often overlooked. --DHeyward (talk) 08:17, 13 November 2013 (UTC)

Oh, okay, thanks for answering. But you seem to have missed my initial point. I wasn't comparing addiction to cancer in saying that the best treatment would be a specific drug regimen. I was warning that like cancer, addiction is a blanket term that refers to a whole lot of different syndromes, each of which has to be understood separately and treated appropriately. It is just as wrong to think there is one cure for a monolithic thing called addiction as it is to think there could be one type of pill that could cure all kinds of cancer. μηδείς (talk) 16:56, 13 November 2013 (UTC)

Non-economic meaning of "exchange rate"?

Deafness#Noise has made me aware that there is a meaning or usage of exchange rate apparently unrelated to the familiar economic term. However, while the term in question seems to belong to science, I cannot discern which scientific field exactly it originates from, or whether it even more properly belongs to some mathematical field, such as statistics. I would like to add a disambiguation notice to Exchange rate, but as long as I am unable to determine the exact meaning and context of the non-economic term, I am unable to do this as I have no idea where to send the reader for more information. Anyone able to help? --Florian Blaschke (talk) 16:19, 12 November 2013 (UTC)

Read the "What is the exchange rate?" section of this article for more info: [12]. As I understand it, to avoid hearing loss, you can trade off, or exchange, a high volume of noise over a short duration, or a lesser volume of noise over a longer duration. StuRat (talk) 17:41, 12 November 2013 (UTC)

I think you will find that the term also refers to the rates of ionic exchange across a membrane, and to casualty rates in military conflicts, and there may be other uses as well. DES ^(talk) 17:46, 12 November 2013 (UTC)

The idea is that for a constant amount of physical motion (+5 dB) or energy (+3 dB) the sound lasts half the duration. Note that this is an utterly absurd idea - it's like saying that dropping a lead weight on your foot is the same as pouring out a bag of lead shot of equal weight (or, at the other extreme, having a lead pellet dropped on your head once a minute for as long as you try to sleep). I don't know how it was arranged, but the description of environmental noise is the most corrupt, deceitful "science" I've ever encountered. The dBA scale is meant to ignore low-frequency sound, the exchange rate to ignore loud sound ... even something as basic as a television commercial, which any idiot watching the box knows is louder than the program, is maintained by experts to be at the same volume even when a congress resorts, in pathetic desperation, to passing laws about it! Wnt (talk) 19:57, 12 November 2013 (UTC)

To understand how loud sounds damage the ear, you need to understand how the ear works. Deafness mostly acrues by damage to the inner ear. Sound is transmitted to the inner ear by an arrangement of three little bones that fuction as levers to match the low mechanical impedance of the ear drum to the high impedance of the inner ear. The stapedius muscle acts on one of the three bones - the stapes. The function of the stapedius muscle is as an automatic volume control. When it is tensioned, it dampens movement of the bones, reducing the intensity of sound tranmitted to the inner ear. Without it, our own voices would be deafening, just as your partner's voice is if she talks at normal loudness but with her mouth 3 inches from your ear. In normal people, the brain tensions the stapedius on a syllable by syllable basis, so you can hear other talkers during the gaps in your own speech. Ever noticed that when striking metal with a hammer, it doesn't bother you, but others nearby complain about the noise? That's because your brain knows when the impact noise will occur and tensions your stapedius at just the right time. The others don't have this happening, so they hear it louder, even if they are a little further away from the noise.

Damage to the inner ear occurs primarily when sudden loud sounds occur - guns fired by others being a particular problem. In such cases the inner ear gets the full intensity before the brain can react and tension the stapedius muscle. In continuous loud noise, the brain tensions the stapedius and there isn't a problem - with a couple of caveats: 1) In the sound is loud enough, AND long enough, the muscle can get tired. That's why teenagers, young and fit, with good stapedious muscles, can withstand loud music for a whole concert without problem, but a 60-year old may notice pain and/or ringing in the ears quite soon after a loud concert starts. 2) If you are subjected to continuous loud noise, with occaisonal extra loud sounds as well, your stapedius muscle may be already partially tired and unable to react fully when the extra loud sounds occur. Note that continous loud sounds (as frequent attendence of loud nightclubs) also results in acclimatisation - you get used to it, just as you get used to higher or lower temperatures eg. Acclimatisation itself is reversible.

You can see from all this that the concept of exchange rate is an oversimplification and somewhat misleading. But it is a way of modelling the fact that the rate at which the stapedius gets tired and unable to control intensity for the inner ear is dependent on two things - the loudness of the sounds, and its duration. The stapedius only has to tension a moderate amount for moderately loud sounds, so for those it can do its job for longer before it gets tired. But it can really tension up and make the midlle ear bones just about lock up solid to control really loud sounds for a short period.

120.145.90.77 (talk) 00:53, 13 November 2013 (UTC)

Commercials can be more "insistent", with constant talking sped up to fit more in, so the annoyance factor is higher. StuRat (talk) 20:15, 12 November 2013 (UTC)

Well, I'm going by the usual standard that if you're in the toilet and you can't hear the television, you know you're missing the program. Wnt (talk) 20:20, 12 November 2013 (UTC)

Then again, if you're in the toilet, your ears might be water-logged. :-) StuRat (talk) 21:43, 12 November 2013 (UTC)

Question about quasi- spacetime?

Since matter, anti-matter and photon can also be associated with eons one one way or the other therefore does time amalgamate with matter (from quantum level to mammoth) besides space? If yes, then how it can be conceived? - I mean mass-time in a simple way162.157.235.1 (talk) 19:32, 12 November 2013 (UTC)EEC

Unlike matter and energy, which can be converted to each other (converting matter to energy happens in nuclear power, for example), matter and time are not convertible. They do, however, affect each other, as in the case of the spacetime you mentioned. StuRat (talk) 19:39, 12 November 2013 (UTC)

It is very difficult to make sense of what you're saying, i.e. I suspect it doesn't make sense, so you should clarify. I see little indication of "quasi-spacetime" as a term with established meaning. One sense in which time associates with matter is that a black hole by most interpretations places a singularity in the future of infalling matter, leading to the question, I suppose, of where the time "goes" when it gets there, whether the matter "stops in time" at the singularity, etc. But a singularity is typically a flaw in a physics model, not a state of being. Another sense is that during the timeline of the Big Bang different phases predominated during specific times, but in that case there is no real equivalence: time correlated with temperature, temperature correlated with a range of possible particles encountered under those conditions. Do you mean either of these? Wnt (talk) 19:45, 12 November 2013 (UTC)

Are you perhaps asking about space-time-matter theory, in which matter in four dimensions is viewed as being induced by geometry in a five-dimensional spacetime? Red Act (talk) 21:36, 12 November 2013 (UTC)

Its just a question came into my mind while thinking if both time and space have raison d'etre innately then why not time has with matter, antimatter, photon, temperature when all born to-gather/ simultaneously?

Matter distorted space-time. The time that appeared with space is also included with the matter by birth too therefore why time is related with space only during the distortion of space-time by matter?

Although, space-time-matter theory might be one of the close answers but is it possible to relate time with matter/ mass separately just like space-time (might not make sense) or all to-gather?162.157.235.1 (talk) 23:24, 12 November 2013 (UTC)EEC

I think I kind of understand so I will offer an opinion. In my understanding, on of the reasons for the existence of time is the "handedness" Chirality of the universe. There is not an equal balance of matter and anti-matter (electron, positrons are not equal and the universe has a preference). My personal interpretation is that this imbalance gives rise to existence and our perception. Had the universe lacked this asymmetry, there would be no time. Or possibly the resolution of this imbalance may have consequences regarding time in the future. --DHeyward (talk) 06:59, 13 November 2013 (UTC)

I don't know what you're asking, but you might be interested in: Quantum gravity, General relativity, CP violation, CPT theorem, Baryogenesis, Theory of everything, Grand unified theory, Entropy, and Arrow of time. If you'd be willing to elaborate a little more, I'm sure someone would be able to give you a good answer (or, at least, point you in the right direction). :-)Phoenixia1177 (talk) 09:07, 13 November 2013 (UTC)

November 13

Messages artifically coded into DNA?

Can this be taken seriously? It was accepted by Icarus. Bubba73 ^{You talkin' to me?} 00:47, 13 November 2013 (UTC)

If I'm reading that right, they want to check the DNA of Earth organisms for signs that a message is encoded in it, presumably from aliens who first seeded the Earth with life. The problem I see is that if this happened when life first appeared on Earth, billions of years ago, the "signal" would be totally lost to the "noise" of random mutations, by now.

On the other hand, if they visited recently, say a few thousand years ago, and placed the signal DNA where we can find it, then we might still be able to decipher it from the descendents of that organism. (Heck, if they used a long-lived organism, it might still be the same one they implanted.) StuRat (talk) 01:41, 13 November 2013 (UTC)

I believe that they are talking about a long time ago because the abstract says "might remain unchanged over cosmological time scales". Bubba73 ^{You talkin' to me?} 02:32, 13 November 2013 (UTC)

Certainly any message would be horribly corrupted by now - but if there was a deliberate effort to retain the message (and if it's simple enough) then they could use advanced error-correcting codes to make the message retrievable. We know that 35% of our useful genes are shared with algae and plants - so if the message was implanted before the split between animals and plants - then a third of it would still be there...and it's really quite easy to come up with error-correcting codes that can survive total destruction of two thirds of the message. The tricky part is that generating a useful message in the useful parts of the DNA would be difficult - you couldn't choose just any old string of A's, G's, C's and T's without making proteins that wouldn't work to keep creatures alive and reproducing. The likelyhood is that any message would have to be stored in "non-coding" or "junk" DNA...but the problem with that is that parts of the molecule that aren't important get mutated more quickly because changes don't kill the mutated organism and there is no evolutionary pressure to stop them from changing too quickly.

Perhaps we're not thinking big enough though. In the book (but not the movie) "Contact" (by Carl Sagan), the aliens somehow engineer a digital image of a perfect circle far down the expansion of PI. Now *that* is "godlike power"!

What blows your mind is that since PI doesn't repeat and is infinitely long, it is certain that there are many digital pictures of circles embedded in it! (Sadly, there are also full color photos of Aardvarks and an infinite number of photos of Angelina Jolie - so this has little to teach us of the mind of God!) After I read "Contact", I wrote software to see if there was an image of a circle in the binary expansion of PI to the first few billion digits - and there isn't anything large enough to be convincing in base 2.  :-(

Perhaps the message the aliens left was "Let there be life!"...and that message has survived through the 4 trillion generations since the first cell was formed. SteveBaker (talk) 04:08, 13 November 2013 (UTC)

Hmm. I suspect you're using a bit more than that (the decimal expansion) of pi doesn't repeat (that is, never settles into an infinite repeating pattern). Probably you're assuming that pi is a normal number, or at least normal to base 10? That's almost certainly true, but no one knows how to prove it.

For example, 0.1101001000100001000001000000100000001... (hope the pattern is clear) also "doesn't repeat and is infinitely long", but it doesn't have any photos of Angelina as contiguous binary strings corresponding to JPEGs. I suppose you could argue that it necessarily encodes such photos in some other way; any JPEG can be coded as a natural number, and every natural number shows up as the number of 0s between two 1s. Is that what you meant? --Trovatore (talk) 04:40, 13 November 2013 (UTC)

Thank you. As far as the image in the bits of pi, nothing or no one can change what pi is. Bubba73 ^{You talkin' to me?} 04:32, 13 November 2013 (UTC)

When I see so-called documentaries discussing "ancient aliens" who supposedly built all of our ancient wonders and perhaps also re-engineered our DNA to be smarter or whatever, they never address the obvious question: If that superior species had to tinker with our DNA, who had to tinker with their DNA? And so on... kind of a "turtles all the way down" issue. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:09, 13 November 2013 (UTC)

It doesn't have to be turtles all the way down. For example, if human scientists made intelligent organisms, it wouldn't entail that we were made. Perhaps hyper advanced aliens got really bored and decided to monkey around and make Earth life, nothing about that requires that they were made. Of course, though, I'm not saying I think that this happened, but that being engineered doesn't imply the engineers were too.Phoenixia1177 (talk) 11:47, 13 November 2013 (UTC)

Having considered any number of crazy ideas of my own devising, I recognize a kindred spirit in these Kazakhstanis. But despite the effort they take, this bioqabbala doesn't actually prove much: there's no significance, no estimate of probability that I can see. Note they are claiming that the message was embedded into the genetic code. However, from a paper I enjoyed in PLOS just recently [13] it is fairly convincingly argued that the genetic code was evolving in known evolutionary time: single celled organisms didn't just show up with a finished product ribosome, but spent close to a billion years around 3 billion years ago figuring out how to do it better and better. (That paper itself is way out there, but IMHO it's on the part of the branch that ought to hold)

I do not exclude the possibility of aliens tinkering with DNA of early life - I don't think that the "turtles all the way down" idea is disproved, because it seems like the pace of life (and physics) was asymptotically faster the closer you come to the Big Bang, so that any number, perhaps even an infinite number, of epochs of civilization, each shaping the next, are possible. But it'll take more proof than this. Wnt (talk) 07:23, 13 November 2013 (UTC)

It's worth noting that the DNA content we share with algae is shared because it's so useful. Functional DNA appears to mutate at a slower rate, because organisms with deleterious mutations in useful DNA tend not to reproduce. It would be quite a feat to encode a message that is also indispensable into an existing organism. Someguy1221 (talk) 11:35, 13 November 2013 (UTC)

I'd just like to note that with the exception of Wnt's comment, all of the comments above show a misunderstanding of what the cited paper says. It does not argue that messages can be found in the DNA, it argues that messages can be found in the genetic code -- that is, in the code that defines the relationship between DNA and the proteins that it produces. If you don't have a reasonably deep understanding of genetics, you will need to read the genetic code article to understand what that means. I personally think it's a bizarre idea, but even so, we should at least be clear on what idea we are discussing. Looie496 (talk) 15:46, 13 November 2013 (UTC)

That's ridiculous. The genetic code is really simple. It is a set of rules (kinda like a computer programming language) for making proteins from a description stored in DNA. It's an incredibly simple mechanism: For each three letter combination of A's, G's, C's and T's, a different amino acid chunk is added to the protein being constructed. A couple of those combinations mean "STOP" and a few are unused. The code is just about the most simple language imaginable - there really isn't anything there to imply a deep mystery. DNA codon table explains the whole thing in a tiny table that fits on half a page of text. There simply isn't room in that encoding to carry any sort of a message! That's flat out impossible - and if they are even discussing that, they are complete idiots.

They must be talking about a message that's embedded in DNA strands themselves - and some misreading or mistranslation of what this research group are doing has occurred.

It's entirely possible to embed binary (well, technically, base-4) messages in DNA. There are actually companies out there that will do that for you for a fee (http://www.genscript.com, for example). You can go to them and for just 28 cents per base-pair, they'll make DNA for you with any sequence of A/G/C/T you like! There are papers being written about standardizing the "BioCode" used to store messages - which A's, G's, C's and T's correspond to which binary digits - how ASCII text may be converted to BioCode, what error-correction scheme should be employed and so forth. Two strains of common bacteria are routinely used for this: E. coli and D. radiodurans.

This is well-established science and it's done for things like DNA watermarking. You can buy a pen with specially marked DNA in the ink which can be used to sign important documents in such a way that would allow future investigators to prove beyond reasonable doubt that that particular pen was used to sign that document.

Civilisations of the future may very well find themselves able to read messages that this generation of humans embeds in the DNA of all manner of living things. It's only a matter of time until someone decides to leave such a message.

Hence, if you believe that aliens ever came to earth (which seems entirely unlikely), then it's entirely plausible that we might find a message left by them in the DNA of some or all living things (depending on how long ago they came here). However, because of the need to employ a highly redundant code in order for the message to survive natural selection and mutation - it might be quite hard for us to detect and decode it.

If you truly did want to leave a message for the future - that's a great way to do it because unlike physical objects like stone tablets or CD-ROMS, it's self-renewing and would be more or less guaranteed to still be here millions of years into the future.

But there is simply no possibility to embed any kind of a message in the "genetic code" mechanism that transcribes it - there simply isn't enough information in the code to say anything more than "Hello"...and certainly not enough information to allow some future civilization to figure out the encoding and translate the language!

SteveBaker (talk) 16:25, 13 November 2013 (UTC)

Steve, Bubba linked to the full paper. All you have to do is read the abstract to see that I am telling the truth. I never said it made sense. I did say one thing a bit misleadingly though -- they aren't exactly talking about complex messages embedded in the genetic code, more like information that provides evidence of intelligent design. Looie496 (talk) 16:36, 13 November 2013 (UTC)

Sorry - I didn't mean to imply that the posting here was nonsense - to the contrary, it was a valuable contribution. I only meant to imply that the paper seems to be either nonsensical - or misinterpreted in some way. SteveBaker (talk) 21:34, 13 November 2013 (UTC)

In theory, assuming a three letter code and 22 amino acids [sic] + stop, you have 64 positions which can express 23 outcomes, i.e. 64 x 23 options = 5 bytes + 6 bits. Perhaps the Gods do not speak Unicode, or perhaps they are Chinese. :) Wnt (talk) 19:50, 13 November 2013 (UTC)

While it's true that there are 64 possible outcomes - of which only 23 (-ish) are used, this is not particularly wasteful. With a base-4 number system (A/G/C/T), you get 16 possible outcomes from a two letter code and 64 possible outcomes from a three letter code - so any less than we have now is clearly not enough. So godlike or evolved, you need a three letter code...and that's what we have. I don't know enough biochemistry to say whether life could have been "designed" to get by with only 15 amino acids...but I suspect not. Another theory about this is that periodically, DNA will lose one base-pair. This causes the whole code to slip one digit. Having unused codons forces the DNA transcription to purposefully fail under such situations rather than to generate a bunch of junk proteins that don't do anything useful...which I believe to be important to the mechanisms of DNA repair and such like. If there had been exactly 15 amino acids plus one stop code...or if there were 63 amino acids - then that would be impossible. SteveBaker (talk) 21:34, 13 November 2013 (UTC)

Yes a three-position codon unit is the minimum needed to be able to handle 23 distinct amino acids. However the specific mapping is more or less arbitrary. In theory any of 64-factorial/23-factorial different codes could have become established. If you postulate aliens who could tinker with early life of a very fundamental level (quite unlikely, I think) then they could have made that choice, leaving essentially a single number, the index of the actual coding table sued out of all the possible tables. But that gives us a value without an encoding scheme. If I tell you that 100110100100011101010000111101010111001001010111111100001010111001001111001100011 is an encoded message, well maybe it is. but unless you have some idea what encoding scheme it uses, there is no meaningful message there. (By the way, I understand that the Genetic code isn't completely random. It seems to be so arranged that one-base errors will often result in an amino acid with similar chemical properties to the one originally coded for, thus reducing the chance that mutations are completely destructive, as I understand it. I don't know how many distinct genetic mappings ("codes") would have this property.) DES ^(talk) 22:44, 13 November 2013 (UTC)

Note that above I was taking 64 x 23, not min(64, 23), and considering all possible genetic codes, not all possible things encoded with a genetic code. The paper I cited makes a good argument that life initially got by on a much smaller set of amino acids, including simple repetitions of a single pair of amino acids, and that, oddly enough, our proteins still show traces of some of this ancestry! I should add that there is quite some interest in adding new amino acids to the code for purposes of synthetic biology, and there's been considerable progress. Wnt (talk) 22:46, 13 November 2013 (UTC)

If you want to consider all possible genetic codes, you may actually have to go beyond 23. As our expanded genetic code article explains, modified organisms have been created that use altered genetic codes involving at least 40 different nonstandard amino acids. It's not clear what the full range of possibilities is. Looie496 (talk) 00:43, 14 November 2013 (UTC)

Thanks, I should have linked that article. For past alien designers these aren't an option, unless we suppose life lost much of the code (and with it, the message). For us creating new life, that's another matter. Actually, there's one thing I'm interested in which I haven't seen - is there a way to make a basic amino acid closely homologous with lysine/arginine that doesn't have any nitrogen in it? (Except the backbone, and that also could use replacement...) I'm sure you can guess where I'm thinking that would be useful! Wnt (talk) 01:31, 14 November 2013 (UTC)

Personally, if anything found outside of earth with A/G/C/T as the genetic code, I'm going for at least common origin. Human's share 99+% with Chimpanzees. And more than 70% with fruit flies. With all the variety of life flowing from arrangements of 4 molecules, it seems non-random that the exact same 4 would be found elsewhere. --DHeyward (talk) 23:15, 13 November 2013 (UTC)

Amount of information

How did the authors get to 384 bits that are supposedly encoded in the genetic code? It's of course log2(64⁶⁴), but there aren't 64 possibilities for each of the 64 codons. The way I would calculate the number: There are 20 standard amino acids (for simplicity forget the 2 nonstandard ones, as they are encoded in a nonstandard way), and a stop codon, i.e. k=21 items that have to be encoded. And there are n=64 codes. We assign one of the k items to each code; that would make kⁿ possibilities. But that number includes genetic codes that do not encode all k items, so we have to subtract the number of possibilities to encode less than k items, which is (k-1)ⁿ. The amount of information in bits is then

log2(kⁿ - (k-1)ⁿ)

For k=21 and n=64 this is approximately 281 bits. Do I make a mistake? Icek (talk) 04:12, 14 November 2013 (UTC)

Volcanism (Earth versus Mars)

(moved here from the Humanities desk)

Approximately when volcanism will stop on Earth as on March for example. tx4urtm --YB ^✍ 00:31, 13 November 2013 (UTC)

If and when the earth's internal heat goes cold, and the planet is dead. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:45, 13 November 2013 (UTC)

I'm guessing that the OP means 'Mars'. Volcanism on Mars#Potential current volcanism confirms that we have never observed any active volcanism on Mars or any other phenomena which imply volcanism there more recently than a couple of million years ago, so it may indeed be the case that Mars is no longer actively volcanic; in which case this is a reasonable question and Bugs' reply rather unfriendly. Having said that, I suspect that we simply don't know an answer. --ColinFine (talk) 01:09, 13 November 2013 (UTC)

As a practical matter, volcanism would probably slack off or stop well before the earth became totally a cold stone. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:50, 13 November 2013 (UTC)

(ec) A couple million years is short for geological time scales, so I wouldn't call that "volcanically dead", but merely dormant. The main difference is the size of the two planets, with Earth considerably larger than Mars. Thus, it takes much longer to cool from it's formation. Another big factor is that the Earth has a large moon, which causes significant tidal heating, while Mars only has smaller moons. A minor factor is that the Earth is closer to the Sun, so gets more solar heating, but of course that's mostly at the surface, with little of it making it's way deep underground. It's entirely possible that the Earth will remain volcanic until the Sun becomes a red giant. StuRat (talk) 01:31, 13 November 2013 (UTC)

• The Earth is denser than and has 10 times the mass of Mars, but less than 4 times the surface area. The dense radioactive elements in the Earth's core give off a lot of energy, and the energy is retained much longer than it was on Mars. We are nowhere near cooling off as far as I am aware (I am sure someone will find an estimate, it may be after the sun goes red giant). In fact, there's evidence there was a naturally occurring nuclear reaction in the crust of Africa at some point. μηδείς (talk) 01:28, 13 November 2013 (UTC)

YB seems to be a Francophone Quebecker, per his user page. In French, the words for "Mars" and "March" are identical, which probably explains the error in the question. I wonder whether the song The Waters of March gave its name to the Dr Who episode The Waters of Mars. --Trovatore (talk) 02:10, 13 November 2013 (UTC)

Yes, I had to go through my list of the 12 joueurs de hockey de l'année québécoise to make sure I'd understood: Gardiner, Trottier, Messier, Lafleur, Lemieux, Dionne, Joliat, Chabot, Primeau, Pilote, Perrault, Parent. I hope our Canadian friend understands this was très amusant, et tout en plaisantant. μηδείς (talk) 02:43, 13 November 2013 (UTC)

As Medis points out, the earth is 10x more massive - so if it started out with the same overall temperature as Mars, then it contained 10 times as much heat energy. So if they both radiated heat at the same rate, you'd expect it to take 10 times longer to cool off to the point where there would be no more vulcanism. However, there are a ton of variables here. With four times the surface area, you'd expect heat loss at four times the rate - and with ten times the mass, you'd wind up with maybe two or three times the amount of time. But there is more to it than that. There is the tidal effect of the moon - but also the core is heated by the radioactivity there - most of the heating comes from Uranium238 - and with a half-life of 4.5 billion years - we've already used up half of it. A NASA site I found says that over the past three billion years the core has probably cooled by a few hundred degrees...I'm not sure how many degrees it would need to reduce to eliminate vulcanism though. The core is somewhere between 5,000 and 6,000 degrees - so I'd guess that our vulcanism would easily outlast the life of the sun.

Remember, Mars and Earth are about the same age - 4.5 billion years. If we think that Mars was volcanic as recently as a couple of million years ago - and if the sun will swallow us up after 7.5 billion years - then volcanism only has to survive for three times what it managed on Mars. Between the larger mass and the tidal effects of the moon (plus closer proximity to the sun, insulating effect of the atmosphere, etc) - this doesn't seem unlikely.

Another way to estimate this is that the inner core is solidifying at a rate of about a half millimeter per year. A meter every 500 years - a two kilometers every million years - so if that rate were maintained, then it'll take 3 billion years for the whole planet to become solid. Of course that depends on that rate not changing - and there are many complicating factors that might speed it up or slow it down.

Bottom line is that we don't know - but it seems that the odds are very good that the sun will kill us before we run out of volcanoes.

SteveBaker (talk) 03:50, 13 November 2013 (UTC)

Again, the Earth is also denser than Mars. This may be a result of the collision event that created the moon, and threw off the less dense layers to create the moon and into space. The denser parts are proportionally more radioactive, so it is likely an equal amount of Mars's mass was less heat producing than the Earth's mass from the beginning. μηδείς (talk) 04:01, 13 November 2013 (UTC)

Note that Mars' core is still under investigation [14] but is believed to be liquid [15]. I've even seen speculation that it is liquid, but at risk of freezing in the future [16]. This seems of great significance for several reasons, foremost being that it appears that Providence has apparently reserved an opportunity for the planet to form a magnetic field just as its water and carbon dioxide are warmed up into an atmosphere by the brightening sun, so that rather than being rapidly stripped by the solar wind, its future oxygen atmosphere might remain for billions of years. But of course, that is very speculative indeed! Wnt (talk) 07:08, 13 November 2013 (UTC)

I suspect that Earth (core) cooling is not primarily limited by radiation, but by heat transport from the core to the surface. Notice how easily the surface changes temperature by 20 K or so between day and night, or even 40 K between summer noon and winter morning - still a geologically trivial time. Part of the internal heat transport is done by convection (which is reasonably efficient), and part by conduction (which is not). Since the diameter of the Earth is (slightly less than) 2 times that of Mars, its core is much better isolated - even if he material is not exactly styrofoam, 3000000m thick rock walls should meet any building standard for energy efficiency ;-). --Stephan Schulz (talk) 07:37, 13 November 2013 (UTC)

Our article Future of the Earth says (with a source) that plate tectonics will cease on Earth about 1.1 billion years from now, so I'd imagine that vulcanism would cease in roughly the same time frame. Of course, all such estimates are extremely speculative. Deor (talk) 19:46, 13 November 2013 (UTC)

I doubt that assumption. The plates can fuse while the Earth still has a substantial molten core, which continues to produce volcanoes, black smokers, etc. StuRat (talk) 20:13, 13 November 2013 (UTC)

Something like this seems to have happened with the planet Venus, which, if I remember from PBS in the 90's, is believed not to have any major tectonic or volcanic activity for 600 million years--but when it last did, a good third or two thirds of the planet was resurfaced in one giant burst. μηδείς (talk) 02:46, 14 November 2013 (UTC)

Is it theoretically possible for machines/vehicles to float like they do in sci-fi stories?

I'm thinking like the squids or ships from The Matrix, where they seem to employ some poorly-defined electromagnetic way of levitating. Is this within the realm of possibility? And if so, how could it actually be utilized, and what kind of energy output would it require? Goodbye Galaxy (talk) 15:21, 13 November 2013 (UTC)

Yes, our article on levitation describes the methods that have been used. Magnetic levitation is probably the most useful method. Looie496 (talk) 15:35, 13 November 2013 (UTC)

(ec) No.

Blocking, cancelling or negating gravity doesn't seem to be possible without resorting to some fairly ridiculous tricks involving entirely impractical things like neutron star material and such. So we're left with something that can exert a force equal in magnitude and opposite in direction. This is done routinely with "magnetic levitation" - such as in the Transrapid train system in Germany which "hovers" 15 centimeters above the track. The problem with that is that you need some magnetic (possibly electromagnetic) surface beneath the vehicle - so you're limited to things like trains that run on tracks of some kind...although perhaps you could consider cars on a road.

Another possibility is to use Newton's third law (every action has an equal and opposite reaction) - which implies some kind of downward thrust - such as in a hovercraft or a Jet pack or (my personal favorite) water-powered jet packs. But you're not going to get the kind of quiet, passive floating of a Star-Wars Landspeeder - and it takes continuous use of energy to keep the machine off the ground.

One fun thing that a lot of people talk about in this context is an Ionocraft - which supposedly uses an electric field to levitate - but which is in fact just a kind of hovercraft with a rather interesting way of creating an airflow. They are impractical beyond a very small scale device.

Our article Levitation explains a few other mechanisms - but mostly they only work with incredibly tiny objects and with massive expenditures of energy.

Short answer: No.

SteveBaker (talk) 15:46, 13 November 2013 (UTC)

I'm guessing it's far too weak, but could the earth's magnetic interior not function as a global "track" for (electro)magnetic levitation? Goodbye Galaxy (talk) 16:00, 13 November 2013 (UTC)

Yes, too weak. And if we could create a magnetic field strong enough to levitate a large vehicle using the Earth to oppose it, it would rip apart any metal ferromagnetic objects nearby. StuRat (talk) 19:28, 13 November 2013 (UTC)

The problems mentioned by SteveBaker can be dealt with by some advanced civilization as follows. The spacecraft uses photon rocket for propulsion, when it lands on Earth, the aliens don't want the emmitted gamma rays to sterilize the local environment. A way to do that is to use an extremely strong magnetic field to convert the gamma rays to axions via the Primakoff effect. Count Iblis (talk) 16:05, 13 November 2013 (UTC)

I think that some fairly mundane mechanisms should not be written off out of hand. A means of applying force to surrounding air or the ground is needed, and the array of electromagnetically mediated mechanisms available is already surprisingly large. One should also not assume that it should look exactly as portrayed in the stories. Otherwise, someone a couple of centuries ago might similarly have answered the question of whether self-propelled horseless carriages were improbable sci-fi with a categorical "no". You need to allow for what might yet be discovered. Plausible mechanisms might include somehow maintaining a higher pressure under the craft: essentially a hovercraft with a perfect skirt. With mechanisms such as plasma windows, ionic thrusters and electrohydrodynamic thrusters, it is easy to imagine systems that could plausibly confine such a pressure without physical skirts, albeit at the cost of some air movement and perhaps some pyrotechnics. Another mechanism might involve properties of a prepared surface (say, in a city, like we already do) with suitable dielectric, conductive or magnetic properties. If we can already levitate graphite and frogs using a static magnetic field against full gravity, it seems we should be saying "maybe" rather than "no". —Quondum 16:32, 13 November 2013 (UTC)

Also, a tethered vehicle provides some additional options for levitation, since it can now have unlimited electricity delivered via the tether, and can be made more stable than a free-floating vehicle. This could work well with an ion engine, for example, as mentioned previously. The tether could also be connected to a ground vehicle, so the entire apparatus can move together. So, you could have a nice floating observation car above a train, for example. Just watch out for those tunnels ! :-) StuRat (talk) 19:48, 13 November 2013 (UTC)

I would not say impossible, because theoretically all you need to levitate a vehicle by action-reaction is to have some particle which is capable of passing through air, water, and perhaps solid matter (terahertz light, X-rays, neutrinos, etc.) but which can be bent around and sent back the way they came by human agency (like many other particles). For example, you could have a couple of focussed neutrino mirrors (I mean corner reflectors) on the bottom of your car which communicate (via neutrino, no doubt) with broadcast stations in several cities on the far side of the planet, which send tremendous beams of neutrinos back at them. The neutrinos, of course, are caught by mirrors at the station and reflect back to you again. Only trouble with those flying chariots is that they get dicey if they fly too fast and can't hold to their projected trajectories, on account of the slow speed of light. Wnt (talk) 19:58, 13 November 2013 (UTC)

Do you have a link to such a particle, Wnt, or are you just using sounds with no relation to reality and pretending they are words? μηδείς (talk) 22:50, 13 November 2013 (UTC)

Really no need for that tone. I was amused by his whimsical idea. 86.134.51.230 (talk) 23:34, 13 November 2013 (UTC)

He said theoretically, a word which should be used carefully. :) Besides, I did describe a particle, a neutrino, and a design; we just need to build some of those pesky mirrors to reflect them. I'm not an expert, but I think that's pretty basic subatomic engineering. If you simply make a macroscopic quark-gluon plasma, would that be enough to start refracting neutrinos? Or if you can get some fine control over the structural changes in nuclei so that you can try to shift them directly to some sort of extended unified planar structure that might be in an island of stability? Admittedly, there I'm speculating, but what I know for sure is that if you can reflect neutrinos you ought to be able to levitate stuff. (Note this is essentially a variant of beam-powered propulsion, and if the device fails to focus and recover essentially all of the neutrinos, it is very expensive. The consequences of irradiating stray peasants on the ground with the neutrino beam are also not very clear to me, though surely better than with the laser system ... call it "research".) Wnt (talk) 01:17, 14 November 2013 (UTC)

Thanks, Wnt. My point, IP 86, was nothing personal with Wnt. But when you start positing imagined entities with no evidential basis whatsoever, like string theory, there's no way to evaluate it. This being the ref desk, we should at least identify when we have no evidence for something. I post all sorts of things like my reference to ice-fishing arctic tribes. But I wouldn't be insulted if someone challenged me on that. μηδείς (talk) 02:43, 14 November 2013 (UTC)

Aqueous cream as a moisturiser?

For many years I've used aqueous cream as a moisturiser. I don't have any medical condition that requires me to use it so this isn't a medical question. I started using it around age 19 when a friend said that I already had lines around my eyes when I smile (I don't know but I'm guessing that would still have been the case if I had used Oil of Olay since I was six; I think it's just the arrangement of my face). For reducing the rate at which my skin appears to age, does aqueous cream make any sense? — Preceding unsigned comment added by 129.215.47.59 (talk) 18:42, 13 November 2013 (UTC)

Moisturizers alone don't actually reduce skin aging. In the US, all the advertisers can say is it "reduces the appearance of fine lines". This effect only lasts as long as the moisturizer is on the skin.

To reduce skin aging, the most important factor is avoiding UV light damage. This means avoiding sunlight, wearing a hat, or using sunblock. Now, some sunblocks also contain moisturizers, so, in that sense, a moisturizer could reduce skin aging. StuRat (talk) 19:21, 13 November 2013 (UTC)

According to this story the answer is 'no' as the scientist said that this was the first time that it had been scientifically proven that a cosmetic face cream could effect a "clinically discernable improvement" in wrinkles. Richerman (talk) 23:56, 13 November 2013 (UTC)

November 14

Type of hearing loss with anger at loud sounds

There's a type of hearing loss that is characterized by extreme sensitivity to loud sounds, which is typified by abnormal anger in the patient when subject to loud sounds. I remember it being called something like acquisition deafness; although acquisition is apparently the wrong word. Can anyone identify the name of this type of hearing loss? Thanks. μηδείς (talk) 01:08, 14 November 2013 (UTC)

(Three words I am not looking for are phonophobia, hyperacusis, and misophonia. It was a two-word term, axxxxxxxx deafness.)

Acoustic trauma? It's two words starting with "A", at least. Red Act (talk) 02:44, 14 November 2013 (UTC)

The "anger at loud sounds" bit sounds like one of the symptoms of autism. StuRat (talk) 03:39, 14 November 2013 (UTC)

No, acoustic trauma's not it. Autism isn't even close, unfortunately. It was a type of hearing loss in otherwise "normal" older people that was accompanied by extra sensitivity to loud sounds, to the point of outrage at an unexpected loud sound. It was something I hadn't heard of until I went looking for articles on hearing loss and heard of this specific type. μηδείς (talk) 04:58, 14 November 2013 (UTC)

It sounds like you're describing loudness recruitment (see: [17], [18], [19]), which is related to/part of Sensorineural hearing loss. I couldn't find the specific term you were looking for, but the only thing I can think of would be "acquired deafness", but that's only an indicator of when, not the what. Presbycusis is age related hearing loss, it could be described as "acquired" and it can/does involve recruitment.Phoenixia1177 (talk) 07:15, 14 November 2013 (UTC)

Ducks adopt unrelated chicks?

Hi, noticed that a particular species of duck often has hordes of ducklings following the parents around, often as many as 20-24. However checking out the species page i note the clutch size is only about 10 wood duck. Where do the extra chicks come from? I've heard of parents ducks adopting as many chicks as they can since ducklings are largely autonomous in terms of feeding and don't require any extra work while the more foreign ducklings she has the greater the chance of her own surviving a crow/seagull attack.. couldn't find anything after a few quick Google searches on the topic however. ideas? --Benjamint 01:40, 14 November 2013 (UTC)

I could think of additional reasons for adopting other ducklings:

1) Once the adopted ducklings mature, they provide mating opportunities for their own ducklings, and prevent inbreeding.

2) Since they fly in flocks, it's useful to have a larger flock, for better aerodynamic efficiency, etc. StuRat (talk) 03:37, 14 November 2013 (UTC)

Earthling Phone Home!

Clickable image, highlighting medium altitude orbits around Earth, from Low Earth to the lowest High Earth orbit (geostationary orbit and its graveyard orbit, at one ninth of the Moon's orbital distance), with the Van Allen radiation belts and the Earth to scale.

If we disregard all possible national security and flight safety issues, can an astronaut in the ISS or any earth-orbiting spacecraft phone home using the Iridium service? (If the radio signal can penetrate the spacecraft's metal hull).

Most manned spacecrafts, except for Apollo moon rockets, are travelling below Iridium's orbits. They must have very good views of many of these satellites at any moment. Does the speed affect their use of Iridium phones?

What would happen if they use a very powerful GSM cellphone to phone home? Let's say a Russian cosmonaut wants to phone home when the ISS is over the great Russian land (if your country is too small, the ISS flies past your country in less one minute!). His beefed-up signal could be picked up by hundreds of ground stations. However, each station may only hear the signal for a very short time depending on signal strength. How does the GSM handle this situation.

Can an astronaut use his off-the-shelf GPS smart phone, tablet or wrist watch to get his approximate location over earth?

Many spacecrafts use GPS as a way of navigation. They must take altitude into consideration. However, the GPS or Glonass circuits in consumer devices probably assume that you're on the ground or maybe within civilian aviation altitudes. How do these inexpensive gadgets operate if they are 400 km above the earth? -- Toytoy (talk) 01:42, 14 November 2013 (UTC)

Some systems like the GPS receiver may not believe that it could be travelling so fast, and therefore not lock on correctly. For a telephone system the Doppler shift would be large and not acceptable to the operator. So I suspect it would not work. Graeme Bartlett (talk) 10:56, 14 November 2013 (UTC)

Duel Electric Meter for saving money?

I live in Michigan and have moved into a house that is electric everything and each room (10 in all)has it's own thermostat. I have been told that we can save money by having a duel electric meter put in if our electric company (Consumers Energy) provides this. What exactly is a duel electric meter and how can it help us save electricity? Officerswife (talk) 02:14, 14 November 2013 (UTC)

I don't know what it is but it's likely spelled "dual" as in two of something rather than "duel" as in a sword or gun fight between two people. A Google search confirms that there are such things as a Dual Electric Meter but I haven't been able to figure out what they do. Dismas|^(talk) 02:20, 14 November 2013 (UTC)

This talks about dual rate electricity but it seems to center on the UK, so I'm not sure how much it would apply to your situation. To my knowledge, we only have a single rate charged to us for electricity here in Vermont but Michigan may have two like the article discusses. Dismas|^(talk) 02:25, 14 November 2013 (UTC)

The article cited by Dismas talks about off-peak electricity delvered via the second meter. This can work well, lowering your electricity costs if you have storage hotwater systems and/or storage space heating - you mostly want heating in the evenings, which are off-peak for the power company, anyway. You can aslo run a small oven from the off-peak meter, so that if you like late (or even early) evening snacks, you can cook them on cheap electricity. You may alternatively have a system used by power companies elsewhere. The second meter is set up to charge at a slightly lower tariff, but the power company has the right to turn off the power to it when demand is high. They usually only do this for short periods - under an hour. You need to consider the usage of such power carefully. In hot weather, if your airconditioning is fed from the low tariff meter, it can result in increased electricity charges, as your aircon will go like the clappers to catch up when the power comes back on. 60.230.232.138 (talk) 03:05, 14 November 2013 (UTC)

I live in Michigan, and have dual meters, as our house was once set-up for an upstairs tenant. However, just having two meters alone may actually cost you money, since now you have 2X the flat monthly rate. However, there are so many plans it's difficult to tell, without analyzing your usage patterns:

1) They have "off-peak usage plans", as mentioned above, which typically charge more at peak times and less at off-peak times. That might require a dual-meter.

2) They have "interruptible service" which promises they will only interrupt it in an "emergency", but my brother had that, and every hot day was considered an emergency, with the result being that he could only use his A/C on days when he didn't need it. I wouldn't expect this to require a dual meter.

3) They have "senior plans", where they charge a lower rate for light usage, and a higher rate for higher usage. Again, I see no reason for a dual meter here.

4) They have lower rates for those with whole house electrical heating. If the heating unit is on one meter at the lower rate and the rest of the appliances go on the other meter at the higher rate, that might explain it. I think this is the case you have. Yes, that could reduce your bill. However, even at the lower rate, electrical heating is still far more expensive than gas heating. StuRat (talk) 03:30, 14 November 2013 (UTC)

Do they not have smart meters in Michigan? I have a single meter that is remotely read and has time-of-use rates. I am not sure how having two meters would be used for multi-rate service. Dual meters are used for solar and other grid-tie systems as they measure the power that is put back on the grid. If you house isn't designed to have multiple service entrances, I don't see how splitting up the service is possible or efficient. Is there a penalty for exceeding a certain amount of kWh per month? Is your house underpowered for a heat pump or central heat such that someone is recommending a different heating system on it's own service? StuRat's #4 sounds most likely (and also can't be turned off in winter by law). --DHeyward (talk) 07:20, 14 November 2013 (UTC)

They have "smart meters" designed to broadcast whether we are home or not to nearby thieves, yes. However, they don't broadcast on the Internet, but only to the street, so the meter readers need to go around in a vehicle to take readings. Unfortunately, the portable units they use to read the meters from the street have a seriously underpowered battery, and the utility company requires the employees to return to base to verify that the battery is dead and get a replacement. Rather than deal with this hassle, the employees instead continue to read the meter manually, just as before. :-) StuRat (talk) 08:20, 14 November 2013 (UTC)

Wow. I believe ours use the power-line for data transmission and is updated daily. The meter is addressable and queryable. Everyday, the power company posts usage (down to the hour) on my account. It's not 100% as sometimes it updates at midnight or 4am but it's correct. My meter is supposed to be physically accessible but I created a courtyard with a gate (the Fire Department could get in, but the power company would have complained if they had ever checked in the last 5 years. They phased out the meter readers. The gas company and the water company read by hand with the gas company being the least efficient. --DHeyward (talk) 10:26, 14 November 2013 (UTC)

That's what my Michigan smart meter is like. It actually lets you break it down to the minute if you want to.

Solar power systems have become common in Australia due to the stupid Government heavily subsidising the installation, and imposing a tarrif for power fed back to the grid much higher than for power drawn from it. No additional meter is required - they have new technology meters that store the amount of electricity fed back separately from electricity drawn off. But dual tarrif (either off-peak or off-in-high demand) are much older ideas that have required dual meters. 60.230.232.138 (talk) 08:56, 14 November 2013 (UTC)

Net metering (the solar meter) is usually required by the local city/utility code based on fire codes (NFPC/NEC) and also allows the utility to lock it out safely. Even though the inverters are suppose to cut out without a grid and there is both a DC and AC disconnect, removing and locking out the meter is the way the power company controls the service entrance. One of the the codes that makes solar ugly is that it's not allowed to penetrate the roof or a wall until it hits the service entrance disconnect and meter. Because of utility laws, only regulated companies are allowed to sell electricity to consumers (i.e. homeowners can't install a sub-metering system to tenants, but a power company can) so a meter is almost always required between the solar power and the consumer. I always wanted to forego the solar array and use off peak cheap energy to charge deep-cycle batteries and then connect the batteries to the solar inverters during on-peak hours. It's almost as cost effective as the raw cost for solar but they won't give me a tax break to buy the batteries. The break even point is around 12 years for current prices. --DHeyward (talk) 10:26, 14 November 2013 (UTC)

That must be a quirk of DHeywood's power company or of the US National Electrical Code (NEC). Or error by DHeywood. DHeywoods's requirement that the solar invertor output be routed to the meter/service connection point before entering the building cannot be applicable in Australia. We have what are known as "battle-axe" blocks. This is a way of saving money on roads. Each roadside in a battle-axe area has residential or light industrial blocks of land fronting the street, and another lot of blocks behind the roadside blocks. The "behind" or rear blocks get their access via drive-ways running down the side of the road-fronting blocks. Hence the name "battle-axe" as that is what it looks like on the title deed survey drawing. To make life reasonable for the meter readers, all gas, water, and electricity meters are installed at the road/street end of the driveway, and there is typically 100 to 300 m of gas-pipes, water pipes and electric cabling from the meters to the house or factory. If the owner of a battle-axe block installs solar power, the power company replaces the meter (and charges a fee), if the existing meter is an old type. But nobody installs additional cabling so that the solar can go via the meter - that would be very expensive, involving trenching, the new cable, filling-in, and re-instatement of the driveway surface, macadam, bitumen, or concrete, whatever it may be. Many $1000's. Who wants cabling running across their roof, over the eaves, and down the side of their house anyway? Not sensible. If the cable is correctly sized and fused, fire is extremely unlikely, virtually impossible, and it is much safer concealed inside the structure. Most invertors are not rated for external installation (ie they are not weather-proof and/or cannot tolerate direct sun) - they can be installed outside in porches and the like however, so long as the sun and rain cannot reach them. 60.230.247.177 (talk) 11:41, 14 November 2013 (UTC)