Wikipedia:Reference desk/Archives/Science/2009 January 31

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= January 31 = WE USE 10% OF OUR BRAINS, IT IS A PROVEN FACT, ONLY INSANELY SMART PEOPLE LIKE ALBERT EINSTEIN CAN USE MORE HE USED 13%, IT HAS BEEN PROVED, NO ONE HAS EVER BEEN KNOWN TO USE MORE THAN 13%

momentum object

If a point object is rotating at radius r, and the radius of rotation is suddenly halved, by the consevation of angular momentum the velocity will double. But how then is linear momentum conserved? Is there a force acting tagentially to the radius? —Preceding unsigned comment added by 70.52.46.213 (talk) 00:00, 31 January 2009 (UTC)

It's hard to imagine any mechanism that would abruptly reduce the radius without exerting some force - and right there, you've blown all hopes of appealing to conservation laws. SteveBaker (talk) 00:51, 31 January 2009 (UTC)

Right, there would have to be a radial force to reduce the radius, but this force would be perpendicular to the motion and so would not affect the speed of the object. —Preceding unsigned comment added by 70.52.46.213 (talk) 01:25, 31 January 2009 (UTC)

For every action, there is an equal and opposite reaction. Linear momentum will be conserved for the entire system, meaning that the barycenter of the two rotating objects will not exhibit a change in momentum. You can't have it both ways with the "instantaneous" change of velocity... any real force, such as a rocket propulsion system, would operate on a conservation of momentum principle. If the linear momentum of the space craft changes, then so must the linear momentum of the earth, or of the rocket exhaust gases, or some other entity. Nimur (talk) 01:52, 31 January 2009 (UTC)

I agree, but there still isn't a force acting in the plane of the object's motion. How can the tangential speed change is there isn't any force acting in the same direction? —Preceding unsigned comment added by 70.52.46.213 (talk) 02:41, 31 January 2009 (UTC)

In that case, (say an orbiting spacecraft fires a rocket towards the planet, with no component of the impulse along the current tangential motion), then the tangential speed does NOT change. The object moves to a lower orbit, and the orbit becomes elliptical, because it now has a tangential velocity that is too fast for circular orbit at the new radius. See orbital transfer for a good overview, and Hohmann transfer orbit for a specific example with diagrams of this situation. Nimur (talk) 16:48, 31 January 2009 (UTC)

Wouldn't that violate convservation of angular momentum and Kepler's Third Law?

No. If you're worried that something is violating conservation, make sure you consider all the components of the system. Don't forget the rocket exhaust gases! Those have mass and momentum, and they go somewhere! Let me emphasize - the rocket exhaust gases are not a "small effect" - they are the entire means of momentum transfer. Nimur (talk) 19:14, 31 January 2009 (UTC)

For concreteness, let's suppose the point mass is moving in a circle on a table and tethered to a string. Further suppose that string isn't simply anchored but instead feeds through a hole in the table so that someone underneath can shorten the string by pulling on it. As someone pulls on the string, the point mass will have a component of its velocity that it radial (i.e. carrying it towards the hole). Since the tension in the string is no longer perpendicular to the motion, that tension will act to increase the velocity. Incidentally, since the total velocity is increasing the centripetal acceleration must be increasing as well, which implies the puller will have to exert increasing amounts of force to continue. Dragons flight (talk) 05:53, 31 January 2009 (UTC)

Sorry, why would the tension force not be perpendicular to the motion?

Because the "pulling-in" motion needed to reduce the length of the string involves moving the object in the same direction as the tension. Dragons flight (talk) 19:11, 31 January 2009 (UTC)

Wouldn't that mean that there's a torque being applied, and that the angular momentum would increase? —Preceding unsigned comment added by 70.52.46.213 (talk) 23:22, 31 January 2009 (UTC)

No, if you calculate everything from the axis of rotation about the hole in the table, then the radial vector ${\vec {r}}$ (which is always measured from the axis of rotation) stays parallel to the force at all times and consequently the torque is always 0. In the case described above the velocity ${\vec {v}}$ ceases to be perpendicular to ${\vec {r}}$ during the transition but that is simply the same as saying that the object is not moving in a perfect circle. Dragons flight (talk) 00:09, 1 February 2009 (UTC)

Really - the bottom line here is that if you don't account for absolutely ALL of the forces, precisely, mathematically (not "Um - it seems like this...") then anytime you find anything weird going on, you are missing something. Probably something simple. Dragon flight's observation about the changing angle of that shortening string is a classic case in point. You think about the mass moving tangentially to the circle and the string acting at right angles to it - but the moment you pull on the string, the mass is moving in a SPIRAL - not a CIRCLE - and the string is not quite at right angles anymore because a line at right angles to a spiral doesn't go through the center of the spiral. Simply discounting this effect because it seems negligable is OK...right up to the point where you proclaim that you've managed to violate some fundamental law! Then you must carefully backtrack over your assumptions and find out where you screwed up. In this case, a spiral isn't a circle - so different math applies and I'm 100% certain that if you crunch the numbers, it'll come out right. It's not necessary for us here on the RD to actually do that - it's sufficient to point out "you've missed this effect" and move on. 72.183.123.248 (talk) 23:40, 31 January 2009 (UTC)

Ah thank you very much, I think I understand. Now for a loosely related question: Consider the table with hole and rope running through it apparatus mentioned above. If the spinning object had mass m, and was fired at a tangential velocity v at a radius r from the hole, and the other end of the rope was attached to a brick of mass mv^2/(rg), would the brick fall? —Preceding unsigned comment added by 70.52.46.213 (talk) 00:59, 1 February 2009 (UTC)

It seems to me that it wouldn't move. The thing to check for here is stability: if the brick falls a tiny bit, how does the force change? The radius decreases, so the rotator accelerates, and the centripetal force increases, opposing the falling brick. Conversely, if the brick rises, the centripetal force is reduced and lets the brick fall again. --Tardis (talk) 04:40, 4 February 2009 (UTC)

general theory of relativity

please explain this formula for a tenth grade student in detail$R_{\mu \nu }-{1 \over 2}g_{\mu \nu }\,R+g_{\mu \nu }\Lambda ={8\pi G \over c^{4}}T_{\mu \nu }$ thanks —Preceding unsigned comment added by 117.193.228.220 (talk) 01:44, 31 January 2009 (UTC)

I'll direct you to the key terms (i.e. metric tensor, stress-energy tensor, Ricci tensor, Ricci scalar and cosmological constant), but I believe it is impossible to explain this in detail to someone with a tenth-grade level of understanding. I won't rule out that some tenth graders may be able to understand it, but if they did so it would indicate a mastery of significant college level topics. In general, we also have an articles on Einstein's field equations and introduction to mathematics of general relativity as well as general relativity and introduction to general relativity. That last one in particular might be where you want to start. Dragons flight (talk) 06:06, 31 January 2009 (UTC)

I think it can be explained in a fairly simple qualitative way. The first part of the equation, $R_{\mu \nu }-{1 \over 2}g_{\mu \nu }\,R$, is called the Einstein tensor. It describes the extent to which space and time are curved or bent away from flat or Euclidean space-time. The term on the right hand side, $T_{\mu \nu }$, is the stress-energy tensor. It describes the amount of matter, gravitational energy and electromagnetic energy at or near a given point in space-time. Ignoring the cosmological constant, $\Lambda$, for a moment, we have

$R_{\mu \nu }-{1 \over 2}g_{\mu \nu }\,R={8\pi G \over c^{4}}T_{\mu \nu }$

which says that the curvature of space-time at each point in space-time is proportional to the amount of matter and energy near that point. The constant of proportionality, ${8\pi G \over c^{4}}$ is numerically very small when we measure it in everyday units of metres, kilograms and seconds - so this means that it takes a very large concentration of matter or energy to bend space-time by any measurable amount. But if you get enough matter close enough together - say something the size of a planet - then it will bend the surrounding space-time so that nearby objects tend to move towards it. This bending of space-time is what we call "gravity".

The cosmological constant term, $g_{\mu \nu }\Lambda$, means that even where there is no matter or energy density, and the stress-energy tensor is zero, space-time still has a built-in tendency to be curved. From observations of distant stars and galaxies, cosmologists now think that Λ has a small positive value, which means that space-time has a built-in tendency to expand. What we aren't yet certain about is the actual physical source of this built-in expansion - what exactly causes Λ to be greater than zero, and what gives it one value rather than another.

(Yes, yes, I know this is incomplete. If anyone feels I have over-simplified or missed out an important point, feel free to add your own simple explanations). Gandalf61 (talk) 11:09, 31 January 2009 (UTC)

The equation is expressed in terms of tensors and you really need to understand these before you can understand the equation. Our article on tensors is quite confusing for beginners. Instead, I recommend that you read the opening chapter of of this book which you can read online. It explains the concept in a very accessible way. SpinningSpark 11:47, 31 January 2009 (UTC)

electrodepostion of copper, efficiency of cathode?

In an experiment when measuring the percentage copper in copper ore by electrodeposition, i have read that cathode efficiency (which is the ratio of weight of metal deposited and the weight that would be if all the current had been used for deposition) is not always 100%, why is this? —Preceding unsigned comment added by 146.179.199.116 (talk) 15:48, 31 January 2009 (UTC)

Not every electron coming off that cathode reduces a copper ion to make copper metal. Some may reduce hydrogen, some may make a negative ion, some may reduce something that is immediately oxidised. Graeme Bartlett (talk) 21:09, 31 January 2009 (UTC)

Make our brain store memory.

Well we're all obviously familiar with how the brain functions in relation to storing memory and all. But just last week i was just sitting down and doing some random thinking when it struck me.....how is it that when we experience something really good or really nasty or anything for that matter the brain stores it in the memory.....something like your first girlfriend or your first day at your first job or your children's wedding day ,it automatically gets stored in the brain.....but at other times when you experience something and you know it ain't that great a memory but you want it to last forever and no matter how much you tell your brain "STORE IT" -- it never will. So my question is WHY?..WHY can't we tell our brain to store memory for us? Wouldn't that be such an amazing thing?You know like a normal hard drive....where you write something in a notepad file and save it and VOILA! its stored on your hard drive forever unless something tragic happens to it.On the same lines WHY can't ALL HUMANS DO THE SAME?ANd i mean like you just tell your brain - integral of cos(x) is sin(x) and it just saves it the first time you tell your brain to do it such that it never gets deleted from your memory I know the neurons get destroyed and all and the memories might get lost but even then in the short term .....example a year!Imagine a student whose a science student and hates history but has to pass it.If he just read through the textbook in one full day and told his brain to remember it ,he would not have to study it ever again and at the end of the year when the exams get over he could easily ask his brain to remove that memory.Wouldn't it be terribly advantageous?Why haven't we as humans tried this on a large scale?Or as a matter of fact why is it not possible? STEVE,if your reading this do answer! i know you might have something to say on this!Vineeth h (talk) 15:52, 31 January 2009 (UTC)

You can force yourself to memorize things, by repeatedly thinking of them many times, over many days. For example, flash cards can be useful to memorize things for a test. If, however, you don't care about it after the test, and never think about it again, it will slowly fade from memory after that. Only thinking about it from time to time will cause the memory to be retained. StuRat (talk) 16:01, 31 January 2009 (UTC)

Have also a search to the archive of this RD, because I remember this is a recurrent topic, although I do not remember exactly everything that has been said --you know, it's human memory pma (talk) 18:34, 31 January 2009 (UTC)

Unfortunately we don't know how the brain functions in relation to storing memory. We have clues and models based on those clues, but we don't have a a precise mechanism worked out yet. Further, memory is is probably encoded by many different mechanisms, depending on what type. For example, most people can "tell themselves" to remember something trivial and recall it a short time later. Some people are extremely good at this and others poor, probably for genetic reasons, but most people can get reasonable good at it with the right training. But long term memories (such as events in your life that made an emotional impact) are likely to be encoded in a very different way. They way these sort of memories are stored and retrieved do not lend themselves to that sort of training, and thus are outwith conscious control. This is probably a evolutionary relic of the origin of the two types and what parts of the brains they are encoded in. How and why is not known for sure, but I'm sure there are lots of models out there. Rockpocket 18:56, 31 January 2009 (UTC)

I imagine noradrenaline has something to do with long-term storage of memories, and other catecholamines which are released whilst experiencing something highly emotional. Where as revising is not at all emotional. --Mark PEA (talk) 23:25, 31 January 2009 (UTC)

See amygdala, part of the limbic system of the brain. The amygdala is involved in learning under particularly emotional conditions (fear, reward, etc.). It's hooked up to the hippocampus which is known to be involved in memory formation. You might be able to harness the amygdala for learning, say calculus, but you'd have to make the accompanying stimulus either really good or really nasty...--- Medical geneticist (talk) 04:25, 1 February 2009 (UTC)

Well thats all good...but you guys still haven't understood my question.....We've all seen "the matrix" right?Or atleast i'm hoping most of you have.Well you know how NEO finds out that they're all infact controlled by machines and stuff......like someone else is controlling them.....well in the same way.....well StuRat you said if we keep saying it over and over again we'll remember it.....but its going to fade away really really soon....and definitely wouldn't last a little over a month!....Its almost as if we aren't in control of our brain!...we can't make it do anything we wan't it to do.....its the brain making us to what IT wants us to do!.....so the real question was that we aren't in total control because like the others mentioned.....various chemicals are responsible and stuff and these aren't released because we tell them to be.....its our brain making all this happen!.....so it may sound pretty dumb but really if you think about it you really can't make your brain to much.....its like your a slave to your brain most of the time....It's like a symbiotic relationship.....we have the brain to make decisions and the brain has our skull for protection! but its just that its got a more parasitic character cause its in control almost all the time.......So really will be ever be able to be in total control over our brain? Yohttp://en.wikipedia.org/w/index.php?title=Wikipedia:Reference_desk/Science&action=edit&section=41u know literaly make it do even the SMALLEST of things that we want it to! You know i was just thinking of some more advantages.....think of a person with a tumour somewhere on their body and suppose that there's a cancerous growth of cells there...well instead of the doctor having to do something to break down the cancerous cells we could just take in the medicine orally and tell our brain to transfer the medicine via the blood stream and control it to move in such a manner that it directly reaches the tumour and starts working on it.....Well i don't know about you guys but it'd be pretty interesting if we could do this......and i do have some more crazy ideas but it'd be quite long.....so in short WHY CAN"T WE DO THIS!Vineeth h (talk) 06:00, 1 February 2009 (UTC)

On a practical level, we can't do it because we don't have the molecular mechanisms in place to do so. How exactly would your brain transfer medicine via the blood stream directly to one cell? Our bodies don't work by magic, they use electrical signals, chemicals and proteins to communicate between cells. Even if you can come up with some feasible mechanism for how this could work, it would require millions of years to evolve. For 99.999999999999% of human evolution there was no anti-cancer medicines, so there was no advantage to evolving a mechanism for delivering it!

On a more fundamental level, you are making the mistake of thinking of your consciousness as a little person sitting in in your skull, pushing buttons and telling your body what to do. It doesn't work like that. What you think of as "you" - really your consciousness - is created by your brain. So ultimately it controls you, because "you" don't exist outside the electrical connections of a few million neurons. If it makes it easier to understand, consider that your genes encode a brain that has made a "Matrix" that your consciousness exists in. Your genes have reserved a part of the brain, the cerebral cortex, for your consciousness to use for its own ends. Its this part that your consciousness has some control over. But your genes keep the rest of the brain for itself, particularly the limbic system, which is involved in emotion, instinct, and long term memory. These things are really important in ensuring your survival (and hence the survival and reproduction of your genes, which is the ultimate goal). Hence your genes are going to make sure it is reserved for these important functions, and not "stolen" by your consciousness to store some history homework for a week! Rockpocket 08:28, 1 February 2009 (UTC)

With all due respect, Rockpocket, aren't you unquestionably implying materialism in that reply? --ReluctantPhilosopher (talk) 16:12, 1 February 2009 (UTC)

Yes, I am. I purposely expressed a rather simplistic eliminativist explanation for maximum contrast with the OP's position. Rockpocket 19:25, 1 February 2009 (UTC)

But should we be peddling our prejudices on the refdesk? ReluctantPhilosopher (talk) 15:13, 2 February 2009 (UTC)

If forgoing a spiritualist explanation in favor of a purely scientific answer is prejudicial in your opinion, then yes. This is a science refdesk and science deals with matter, molecules, cells and their interactions. Neuroscientists, in general reject dualism. Reflecting that in an answer is hardly peddling prejudice in my opinion. That said, the OP may also be interested in reading our rather good philosophy of mind article, and make up his own mind. Rockpocket 20:31, 2 February 2009 (UTC)

The degree of conscious control that out OP considers would be rapidly lethal to us! If we could consciously control all of that super-delicate machinery - without the slightest understanding of how it works - then you could easily make a mistake and kill yourself. Protecting your body from your conscious mind is a vital part of what makes our bodies work. Suppose you got distracted and forgot to make your heart beat - or if you turned off blood supply to your left leg and forgot to turn it back on again! No - this would be nothing short of a death sentence! SteveBaker (talk) 15:00, 1 February 2009 (UTC)

The OP should read up on determinism and Free will#In science. "You" cannot control your brain's actions because "you" are the result of your brain's actions. Of course this sparks many debates with almost all religions and the whole topic of spirituality. Ethical issues are discussed in the determinism article also (i.e. is someone with a psychological illness guilty of their actions, when they commit a crime). You can then ask the question if other mammals have free will, if anything with a CNS has free will, or maybe even a bacterium. Or you can just believe that neurons process it all and there is no "spirit" --Mark PEA (talk) 20:19, 2 February 2009 (UTC)

Grrr... if only I had the references... I will eventually get them and fix the biased articles written by materialists and determinists. I already fixed the free will article some time ago which, in all it's magnificence, had no section on libertarian (non-compatiblist) free will at all before. _lol ReluctantPhilosopher (talk) 16:45, 3 February 2009 (UTC)

If anyone can help me out here... two of the references I am looking for are the ones that say that 1) Physicists today reject out of hand any theory that denies free will (I heard this in a program on Discovery channel about the current theories of the universe and its origin), and 2)Most physicists try to keep free will out of their theories because it confuses matters (I read this on some webpage). Or may be I'll have to ask at the humanities web page. I know some wonderful philosophers who are much clearer on the issue involved in the discussion of free will than most of the physicists. Read this for starters. It's a must read for those who think the issue of free will can be settled through physics --ReluctantPhilosopher (talk) 17:03, 3 February 2009 (UTC)

Best way to pour liquid out of a cup without it dribbling down the side?

Does physics have something to say about this? Thank you Louis Waweru  Talk  16:05, 31 January 2009 (UTC)

Surface tension is a general idea of liquid sticking together as a blob (cohesion among itself) rather than just going with gravity as a perfect liquid would, and adhesion to the vessel could then pull that blob away from "straight down". More technically, consider the contact angle between the liquid and the edge vs the angle at which the edge is while pouring. DMacks (talk) 17:42, 31 January 2009 (UTC)

In fact, for this operation chemists usually have a glass stick into the lower vessel, so that the liquid adhere to it instead of adhering to the cup's side, especially when the liquid has to be poured very slowly. This also works for everyday needs, of course. Another way to prevent adhesion to the cup (only for kitchen use) is, pouring the water or milk with a certain velocity; I follow this method with reasonably good results, say I made only few disasters, very seldom. It's important to remember that the lower cup has to be stable enough, otherwise the flow just take it away on the floor. pma (talk) 18:25, 31 January 2009 (UTC)

So, putting a chopstick or something in the lower glass, and pouring onto the chopstick? Is that the idea? (Just tried it, works much better!) Louis Waweru  Talk  19:21, 31 January 2009 (UTC)

Yeah, just hold the chopstick over the top of the container you need to pour liquid out of and let the liquid run down the chopstick into the other cup. 96.242.34.226 (talk) 19:42, 31 January 2009 (UTC)

And if you need to use it frequently, you may want to get the apposite tool, which is named stirring rod (here [1] is a quick view). There are of various sizes, both for lab and kitchen, usually by glass. If you google it you'll find a lot of info about where to find it, and how to use it properly (like this [2] for lab's use). pma (talk) 20:05, 31 January 2009 (UTC)

I've noticed this problem is worst when pouring a small amount out of a large container, especially when the liquid is quite thick. This comes up often with liquid laundry detergent. One solution I've seen is a double circular rim. The detergent pours out of the inner rim. The outer rim catches any spills, and they slowly dribble back down a drainage hole (DH) back into the container. The top screws on outside the outer rim. Here's a cross-section:

         INNER
          RIM 
         |    |
   <-  | |    | | OUTER           HANDLE
 POUR  | |      | RIM      +-------------------+
  DIR  +-+  DH /           | +---------------+ |
         |    /            | |               | |
     +---+    +------------+ +---------------+ +--+
     |            CONTAINER                       |

StuRat (talk) 01:56, 1 February 2009 (UTC)

Electric shock

Is there a danger of getting an electric shock when a person(standing on the ground) touches one of the wires of two phase generator of electricity that is not grounded? —Preceding unsigned comment added by 202.70.74.181 (talk) 17:46, 31 January 2009 (UTC)

Definitely. It sounds like that arrangement is a guaranteed way to create a life-threatening electrocution hazard. Worse yet: the most dangerous hazard is the possibility that the wiring is not correct, or does not match the schematic, or otherwise has high voltage and high current in places you might not expect. Even a wire which "should be" safe may actually be live. You should always assume a wire is live and dangerous unless you are trained to make a more thorough assessment. Nimur (talk) 19:18, 31 January 2009 (UTC)

Well its definitely not a safe thing to do but I think the question was more theoretical. If the generator is genuinely isolated from earth then you should not get a shock if you were to touch only one conductor. However, it is too difficult in practice to prevent accidental grounding in a real electrical distribution system. The only places this is done to my knowledge is on oil rigs were sparks to ground are a bigger safety hazard than electric shock and even then there are additional safeguards. SpinningSpark 01:25, 1 February 2009 (UTC)

Urban legend regarding pitbulls

Is there any truth to the claim that if a pitbull is allowed to taste human blood, it will become uncontrollable and keep attacking humans to experience that delicious taste again(and likely have to be euthanized)? Is this true of any dogs, or any animals? 69.224.37.48 (talk) 19:51, 31 January 2009 (UTC)

No. — Lomn 22:38, 31 January 2009 (UTC)

No. They don't do that for (for example) cow blood. A dog that once tastes a steak doesn't subsequently lose all control of itself whenever there is another steak around. Why would human blood be any different? Nope - this is nonsense...please tell whoever told it to you. The world needs fewer of these stupid urban legends. 72.183.123.248 (talk) 23:24, 31 January 2009 (UTC)

Okay, no, dogs that taste human blood don't inherently go crazy and become uncontrollable. However, there is still some legitimate cause for concern. An animal that bites people may be sick or dangerously vicious (not because blood makes it crazy, but because it was already violent to begin with). The former may be treatable, while the latter might be controllable with reasonable precautions. There is also a risk that some animals that bite people might come to think it is okay to do so again in the future, i.e. a form of learned behavior, so one needs to be careful about not encouraging such behavior. In general, a dog that has bitten people is probably one that it is best to keep away from unfamiliar people and take greater care around. I will also note that it is common in many jurisdictions to euthanize animals that have attacked people. Dragons flight (talk) 00:28, 1 February 2009 (UTC)

There is cause for concern - sure. If a dog gets the idea that it is the alpha-dog in the 'pack' of humans with which it lives then the humans who live with it had better plan on taking back the alpha slot - or being continually hassled by the dog. If the dog tries this on - you need to wrestle it to the ground - roll it onto it's back - place your hand around it's throat and squeeze gently. This says "I am the dominant animal in this pack and don't you ever forget it!". You also need to ensure that when you and the dog approach a doorway - you go first. Don't feed the dog until AFTER the family has eaten. Make a point of taking away the dog's food while it's eating (you can give it back later). Basically, it's got to know that it's place in the pack is somewhere below the lowest human. This seems a little sad - but a dog is happy to be what it is. What they don't like is uncertainty. 72.183.123.248 (talk) 02:14, 1 February 2009 (UTC)

That's good advice ....248. There are no bad dogs just bad owners. Richard Avery (talk) 08:40, 1 February 2009 (UTC)

Its good advice except for the rolling the dog on its back part. This actually says to the dog "I am going to kill you." Would you feel comfortable living with someone who was threatening your life everytime you walked in to the room? Especially bad if the dog is violent. Don't do this. Livewireo (talk) 20:34, 2 February 2009 (UTC)

i dont want JOWLS

how do i keep from getting JOWLS when im old. i'm 25. this is not a request for medical advice. —Preceding unsigned comment added by 82.120.227.157 (talk) 21:07, 31 January 2009 (UTC)

There are exercises you can do. One is to bring your bottom lip over your top one and hold it there for 5 seconds, then relax. Then do the same thing while smiling. Also keeping all your teeth helps! --TammyMoet (talk) 21:39, 31 January 2009 (UTC)

Unfortunately, a lot of this stuff is genetic; if you dad and/or mom had jowls, you are more likely to have them as well. --Jayron32.talk.contribs 22:25, 31 January 2009 (UTC)