Science desk
< August 27	<< Jul \| August \| Sep >>	August 29 >

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

August 28

Strength of piss

What is the thrust generated by an average penis ejecting an average amount of piss, as measured in newtons? —Preceding unsigned comment added by 81.44.97.243 (talk) 00:54, 28 August 2010

I only found normal values of uroflow for different genders and age groups, which are measured in mL/s. See uroflowmetry---Sluzzelin talk 01:05, 28 August 2010 (UTC)[reply]

So now that we have the amount of mass ejected per second (21.525 grams), we only need to know at what speed urine is usually excreted to complete the equation and find out how much thrust piss produces. —Preceding unsigned comment added by 81.44.97.243 (talk) 01:12, 28 August 2010 (UTC)[reply]

Surely it's the bladder that produces the force, not the penis... Physchim62 (talk) 01:38, 28 August 2010 (UTC)[reply]

You are absolutely correct Physchim62. Of course it is the muscles surrounding the bladder that generate the pressure in the urine in order to expel it. If that was not the case, how would women urinate? I suspect the OP really just wanted to post a question in which he got to publish the words penis and piss. I see a couple of smart Users deleted the question but our OP restored it both times, along with messages on the User talk pages of the deleters. I'm with the deleters. I think it is a crass question. Dolphin (t) 04:21, 28 August 2010 (UTC)[reply]

All that is needed for a woman to urinate is a relaxed sphincter: gravity will do the rest. The same goes for men, really. And I don't see anything wrong with the question, especially as it's given me the chance to dispel a myth held by yourself! --TammyMoet (talk) 08:19, 28 August 2010 (UTC)[reply]

Well, well, you're doing a great job of assuming good faith, aren't you Dolphin51? Couldn't my use of "penis" instead of "bladder" have been a genuine mistake? But well, keep screaming bloody murder every time you see a mildly low-registry word, if you wish...

As for those who were kind enough to reply, thank you. If as you say the major component driving piss flow is gravity, then that means an acceleration of 9.8 m². Therefore, after one second of flowing, piss is moving at 9.8 m/s. 0.021525 kg moving at 9.8 m/s equates to a thrust of 0.210945 newtons. Question solved.—Preceding unsigned comment added by 81.44.99.150 (talk) 09:31, 28 August 2010

... except that you need to include air resistance and the initial speed imparted by bladder pressure (which varies). Dbfirs 09:51, 28 August 2010 (UTC)[reply]

I'm not sure I agree, Tammy. Gravity is one component, sure, but I believe both genders are capable of regulating the rate of flow to at least some extent, too. By more than one mechanism, I would think. Anyway see Urination#Voluntary control.

To the OP, I would recommend the Thrust article. Wikiscient (talk) 11:36, 28 August 2010 (UTC)[reply]

The unfortunate individuals who aren't capable of regulating the flow by means of sphincter control suffer from incontinence (or retention if the sphincter is permanently closed). There are other factors, but if the sphincter is incapable of being closed, incontinence is inevitable. --TammyMoet (talk) 12:38, 28 August 2010 (UTC)[reply]

Ok. Assume the sphincter is completely open. Assuming an upright posture, gravity is helping void the bladder. Is it possible during this time to adjust the flow rate, without changing sphincter dilation, just by means of contracting or relaxing different abdominal muscle groups? Is there a significant gender difference in the control of that variable "thrust"? Wikiscient (talk) 12:54, 28 August 2010 (UTC)[reply]

The bladder and the rest of the urinary tract is lined with transitional epithelium, which is expandable, as is the connective tissue. The force that causes this expansion lessens when the urine is able to escape...wouldn't that be what generates urine flow? Bearing down also increases flow rate and flow force. DRosenbach ^{(Talk | Contribs)} 01:22, 29 August 2010 (UTC)[reply]

One should also take into account that lots of men in time develop prostate cancer. This often causes problems with urination and effects flow. --VanBurenen (talk) 11:47, 28 August 2010 (UTC)[reply]

To calculate the initial speed, one could use the observation that younger males of the species have been known to engage in competitions to see who can reach the greatest height. (Perhaps between one and three feet would be typical? - some may have even stronger bladders?) A simple energy calculation (v² = 2gh) gives the initial velocity. Initial velocity often tends towards zero with increasing age for males, as mentioned above, but to a lesser extent for females. Dbfirs 21:03, 28 August 2010 (UTC)[reply]

Surely we'd need to factor in the horizontal component of the velocity as well? Is there a standardised distance to the wall for such competitions? --81.158.2.129 (talk) 21:14, 28 August 2010 (UTC)[reply]

I don't know -- I never entered them! I assume that the distance is small so that air resistance is less and height is thus maximised, then the horizontal component of velocity would be small, but yes, my calculation would under-estimate the initial velocity. Dbfirs 22:19, 28 August 2010 (UTC)[reply]

Well, see, now I'm wondering if there are people so determined to win that they make

u_{horizontal}

zero even given the obvious consequences. Which officially proves that I've thought about this question for too long. --81.158.2.129 (talk) 08:42, 29 August 2010 (UTC)[reply]

Justifiably deleted by Sluzzelin, restored for response:

"I see I got you all arguing again! Great! 8-) —Preceding unsigned comment added by 88.104.92.205 (talk) 22:38, 28 August 2010 (UTC) "[reply]

You got us all talking and laughing and having a good time. Thanks! Now, why not join us...? Wikiscient (talk) 00:30, 29 August 2010 (UTC)[reply]

I don't have a complete answer to the OP, but at least I have some references that others might be able to use to move this forward. According to this paper and this very detailed thesis, which apparently took 12 years to complete the bladder pressure generated during urination (a.k.a. "micturition" in biomedical literature) is generated primary by the detrusor muscle, and normally ranges as high as 60 cm H₂O (approx 6 kPa = 6000 N/m²). -- Scray (talk) 03:48, 29 August 2010 (UTC)[reply]

... which is decreased by the "nozzle effect" of Choked flow, with a corresponding increase in velocity dependent on the anatomical configuration. Why are we still discussing this? Dbfirs 12:31, 29 August 2010 (UTC)[reply]

A male is better equipped to direct his urinary thrust than a female which the former may demonstrate by writing his name in the snow. OR: I know of one female who can write her name in the snow. Her name is Dot. _{Excuse my wee joke.} Cuddlyable3 (talk) 23:36, 29 August 2010 (UTC)[reply]

about ICs

Why we use silicon chip only in ICs and not any other element —Preceding unsigned comment added by 182.156.95.31 (talk) 01:41, 28 August 2010 (UTC)[reply]

We don't only use silicon. List of semiconductor materials. Silicon is just the most commonly used one because it is, well, common. It is actually the 8th most common element in the universe and the 2nd most abundant element in the earth's crust. Vespine (talk) 02:03, 28 August 2010 (UTC)[reply]

It's also very easy to make ICs in silicon, and pretty hard in the other semiconductors. Silicon wafers are pretty hard to break or damage, which doesn't apply to the other materials. It's also easy to grow glass on the surface of silicon, which can't be done with the other materials. --Phil Holmes (talk) 10:40, 28 August 2010 (UTC)[reply]

"Silicon wafers are pretty hard to break or damage"?? I'm going to guess that you mean when compared to something else. I work with silicon wafers and people break them every day here. Dismas|^(talk) 00:01, 29 August 2010 (UTC)[reply]

I thought some ics were made from Gallium arsenide?--88.104.93.216 (talk) 11:44, 29 August 2010 (UTC)[reply]

A gas that clumps together in a gravity environment?

Is there some kind of high temperature gas that by its nature clumps together (even amid other gasses) in a gravity environment instead of spreading out? The gas would clump together in a gravity environment like water clumps together in a non-gravity environment? Are you ready for IPv6? (talk) 02:06, 28 August 2010 (UTC)[reply]

Water clumping is due to surface tension so since gasses do not have a surface, my guess is the answer is no. Another property of gas which makes me think this won't happen is that it will tend towards equilibrium in any container, whether there is gravity or not. Having said that, it depends on what you mean by "high temperature", once you hit plasma, the answer is probably different, but then it's no longer a gas. Vespine (talk) 02:26, 28 August 2010 (UTC)[reply]

I don't understand what you mean by water clumping together in a non-gravity environment -- water clumps together regardless of gravity. But that doesn't really matter, the answer is that anything that clumps together is a liquid or solid by definition, not a gas. Looie496 (talk) 03:41, 28 August 2010 (UTC)[reply]

Well, if you have enough gas that it can't escape its own gravity, then it will indeed "clump together". That's how stars form. Is that what you mean?

You might also be talking about plasma, as Vespine says; I disagree with him that that's "no longer a gas". Plasma is sometimes called "the fourth state of matter" but that's kind of bogus; plasmas are gases, just ones that are hot enough to be ionized, resulting in unusual behavior for gases as a result of electromagnetic forces. --Trovatore (talk) 03:47, 28 August 2010 (UTC)[reply]

Well there's no ambiguity in the Plasma article about it, plasma is like a gas, but it also has properties which are quite unlike a solid, liquid OR gas, so is in fact considered to be a distinct fourth state of matter. That claim doesn't seem to be sourced but it's the way I've always understood it. If you think it's bogus and can find some sources to back you up, you'd be helping the article by clearing that up. Vespine (talk) 23:06, 29 August 2010 (UTC)[reply]

My understanding is that the "fourth state of matter" claim is not widely accepted, on the grounds that there's no interface between plasma and gas "phases". So you can't draw a sensible phase diagram where at some point you have the two states coexisting, with a boundary between them.

But obviously this is really a question of what definition you're using. --Trovatore (talk) 17:51, 30 August 2010 (UTC)[reply]

If you fill (say) an aquarium tank with a heavy gas (Sulfur hexafluoride, for example) then it'll pretty much stay right there - held in place by gravity. One famous demo of this is to make a boat out of aluminium foil and float it on the surface of the gas. It behaves a lot like a liquid - if you make a hole in the bottom of the foil boat, it'll gradually fill with gas and sink! Do a search on YouTube for "sulphur hexafluoride boat" and you'll find a bunch of videos...(half of which are probably faked because it's YouTube)...but at least some of them are real! SteveBaker (talk) 04:30, 28 August 2010 (UTC)[reply]

Wow, I'd like to see that. SF6 sounds like really cool stuff. Too bad it's a greenhouse gas. --Trovatore (talk) 10:02, 28 August 2010 (UTC)[reply]

The demonstration on Mythbusters was pretty neat - the tinfoil boat looks like it's levitating! I bet you could find it on YouTube. SteveBaker (talk) 14:03, 30 August 2010 (UTC)[reply]

Are there any plasmas that will clump together like a some thick oil? Or what about a gas with a bunch of stuff dissolved in it like how water plus dirt makes sticky mud? Are you ready for IPv6? (talk) 05:30, 28 August 2010 (UTC)[reply]

What about gaseous bromine, for the gas, and ball lightning for the plasma? ~A H 1^(TCU) 18:26, 28 August 2010 (UTC)[reply]

I've searched a lot and can't find any information on gaseous bromine clumping together (e.g. like mud) and about the only thing out there is that it's reddish color and that it is toxic. Any good links? Are you ready for IPv6? (talk) 23:11, 29 August 2010 (UTC)[reply]

I don't actually have a source for that; when I searched for "gaseous bromine clumping", the first result I got was this Reference desk entry. I've only observed the fumes of bromine appearing opaque in air before dissipating, so I'm not sure it has the specific desired clumping effect, and experiments involving the gas can be dangerous. ~A H 1^(TCU) 14:53, 2 September 2010 (UTC)[reply]

Bicycle physics

http://en.wikipedia.org/wiki/Bicycle_physics#Turning Please see Leaning section

The article gives the relationship between the lean angle and the other parameters as tanθ = m²/(gr). I tried to work this out myself, and I was only successful if I assumed the normal force was acting parallel to the bike, as in an angle θ from the normal. But I thought the normal force was always perpendicular to the surface. Help? —Preceding unsigned comment added by 76.68.247.183 (talk) 02:15, 28 August 2010 (UTC)[reply]

The normal force N is the component that is perpendicular to the surface. When a vehicle is following a curved path there must be a centripetal force. In the case of a bicycle the centripetal force F_f is a force parallel to the surface. (In the diagram it is described as the Friction force.) The resultant force exerted on the bicycle by the surface is the vector sum of the normal force N plus the centripetal force F_f . This resultant force acts parallel to the bicycle, up through the center of mass of bicycle + cyclist (ie at an angle θ).

The equation is not tanθ = m²/(gr) but v²/(gr). Dolphin (t) 05:39, 28 August 2010 (UTC)[reply]

Sorry, I had meant v². But why would the resultant force act parallel to the bicycle? It seems to me that the bicycle could be at any angle, and the normal force and friction force would cancel gravity and the centrifugal force respectively. 76.68.247.183 (talk) 11:58, 28 August 2010 (UTC)[reply]

The resultant of normal force and friction must act through the combined centre of gravity because otherwise there would be a moment about the centre of gravity and this moment would rotate the bicycle. In practice, the rider corrects for any such rotation by adjusting the angle. It has been known for inexperienced pillion passengers on a motor cycle to lean the wrong way and thus overturn the motor cycle. Dbfirs 18:36, 28 August 2010 (UTC)[reply]

So simple, thanks a lot. 76.68.247.183 (talk) 02:04, 29 August 2010 (UTC)[reply]

pituitarum

what is pituitarum? —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 03:25, 28 August 2010 (UTC)[reply]

From a scientific point of view, it's water. Salespeople might say otherwise. -- Scray (talk) 03:33, 28 August 2010 (UTC)[reply]

It's a homeopathic "treatment". Indeed - it's just water - and it doesn't work (unless you are trying to treat "thirst", for example!). Homeopathy is one of the great scams of our times - and it's hard to believe it's still legal. The manufacturers must be laughing all the way to the bank - they are charging $24 for 1 ounce of water! You can buy rather nice Evian spring water for $1.50 for 1.5 liters - which is about 3 cents an ounce...that means that the manufacturer of Pituitarum would be making an 80,000% profit if they didn't put the stuff in such nice little bottles! Unless of course they're using tap water - that's $3 for 1000 gallons - which is $0.00002 per ounce and would allow them to make a 100,000,000% profit if they sold the stuff in enough bulk! Not bad eh? So NEVER buy homeopathic products of any kind. See Homeopathy for details. SteveBaker (talk) 04:23, 28 August 2010 (UTC)[reply]

Never heard of "pituitarium", but I have some "homeopathic" remedies (cayenne pepper nasal spray) that makes your nose run a lot, but then stops it from running. It works; stopping my nose from running during a cold. --Chemicalinterest (talk) 11:12, 28 August 2010 (UTC)[reply]

That sounds more of a herbal remedy than the usual ridiculous dilutions of traditional homeopathy. Dbfirs 19:34, 28 August 2010 (UTC)[reply]

If you have a genuine homeopathic remedy, I highly doubt it works (other then as a placebo and/or hydrating you if necessary). A genuine homeopathic remedy is basically just water as others have said. This 'cayenne pepper nasal spray' doesn't sound like it's really a homeopathic remedy. The term is sometimes used loosely to mean any form of Alternative medicine at least a Westernised one but that isn't the traditional meaning (which our article uses). A real homeopathic remedy involves sufficient serial dilution that what you end up with is water. If your 'cayenne pepper nasal spray' actually smells like something other then water, then it clearly is not a homeopathy remedy, even if it may call it self one Nil Einne (talk) 12:16, 28 August 2010 (UTC)[reply]

Very concentrated. It burns your nose like fire when it is squirt up the nose. --Chemicalinterest (talk) 11:10, 29 August 2010 (UTC)[reply]

So don't use it. Why should you be stopping your nose running, anyway? Just get a lot of soft tissues and blow/wipe your nose regularly to carry the bad stuff away, washing your hands regularly. A runny nose is part of your immune response (and our article really sucks). 86.161.108.172 (talk) 00:15, 30 August 2010 (UTC)[reply]

If it stings in a way that water doesn't - then it's not homeopathic. SteveBaker (talk) 02:03, 30 August 2010 (UTC)[reply]

Homeopathy works. Just look at how many people piss piss after they drink water, and no wonder: all of the world's water has passed through piss. 67.243.7.245 (talk) 16:03, 28 August 2010 (UTC)[reply]

The central secret of homeopathy is that merchants can get away with labeling something with the name of some herb and a concentration like "10X" or "50X". And reasonable people assume, that's ten times some standard concentration. But that's not what it means! It is a special secret homeopathy notation that means that some fairly standard old USP drug has been diluted 1 to 10 for 10 times, or for 50 times, etc. Leaving no non-water molecule present. There's all kinds of post hoc explanation for this, but obviously it's the money.

Question: has anyone ever actually checked that they really start with the indicated drug solution? I bet they fill those things up straight from the tap. Wnt (talk) 17:59, 28 August 2010 (UTC)[reply]

Meaning of 'Red" in Red-Al

What is the meaning of "Red" in Red-Al? Does it mean the color or Red-Al? or it has other meaning ?

Thanks--Wolfch (talk) 04:49, 28 August 2010 (UTC)[reply]

Reduction or reductive.--Stone (talk) 05:16, 28 August 2010 (UTC)[reply]

Entropy

Why the cyclic integral of dQ/T for a cyclic reversible process is zero?? Does Entropy remain constant in an irreversible adiabatic process?? —Preceding unsigned comment added by 115.109.194.75 (talk) 13:25, 28 August 2010 (UTC)[reply]

No. If you take a look at Entropy#Classical thermodynamics you'll see that the equation is

\oint {\frac {\delta q}{T}}\geq 0

The greater than or equal to sign means that the entropy change being 0 (i.e. the process being reversible) is only a lower bound. --81.158.2.129 (talk) 08:36, 29 August 2010 (UTC)[reply]

What is the solubility of polystyrene in acetone?

Or, in other words, given a certain amount of acetone, say 100g, what's the maximum amount of polystyrene that will dissolve in it? 76.27.175.80 (talk) 15:23, 28 August 2010 (UTC)[reply]

This might be slightly tough to answer, as it will depend to at least some extent on temperature but also the size of the polystyrene chains. (Here is a paper for 60-ish years ago about how the solubility of polystyrene varies with molecular weight.) I don't know how standardised the molecular weight in commercially-available polystyrene is. It does, however, sound like the sort of experiment one could easily do at home (with appropriate safety precautions, of course). --81.158.2.129 (talk) 20:24, 28 August 2010 (UTC)[reply]

Herbal remedies

Why are herbal remedies considered alternative medicine? Many herbs contain chemicals with various beneficial effects. --70.134.48.188 (talk) 15:30, 28 August 2010 (UTC)[reply]

I presume this is coming from my answer to the above question? If so did you read the linked article?

In Western culture, alternative "medicine" is any healing practice "that does not fall within the realm of conventional medicine",[1] or "that which has not been shown consistently to be effective."[2] It is often opposed to evidence based medicine and encompasses therapies with an historical or cultural, rather than a scientific, basis.

Later it says

Jurisdictions where alternative medical practices are sufficiently widespread may license and regulate them. The claims made by alternative medicine practitioners are generally not accepted by the medical community because evidence-based assessment of safety and efficacy is either not available or has not been performed for these practices. If scientific investigation establishes the safety and effectiveness of an alternative medical practice, it then becomes mainstream medicine and is no longer "alternative", and may therefore become widely adopted by conventional practitioners.

I had planned to explain further but actually this seems clear enough to me.

But to summarise, most herbal remedies (and anything else that's alternative medicine) don't have sufficient evidence-based assessments of their efficacy and safety that is required by regulating agencies throughout the world, and in fact supporters of such remedies have generally strong opposed requiring such products to be regulated in the same way. Therefore they are alternative medicine.

If a herbal remedy does meet the same standards expected of normal medicine, then it isn't considered alternative medicine. However demonstrating the efficacy is not cheap or easy so it's rarely done (and often when the tests are done they are inconclusive or show now evidence). Also if you are going to go through that process it often makes sense to isolate the active compound and patent it if you can. That enables you to more easily control the variables and deliver higher levels. (Some alternative medicine practices are inherently opposed to the norms required too.)

To use an example, I could say 'cat fur is a great treatment for infertility'. This is something I just made up so is almost definitely nonsense. Some people may very well believe that cat fur has various beneficial effects, but without evidence it ain't science.

A different more real example would be vitamins and minerals. If you have a poor nightvision and a doctor determines you probably aren't getting enough vitamin A, they may very well proscribe vitamin A tablets and recommend a change in diet. This wouldn't be considered alternative medicine. Megavitamin therapy is however.

Nil Einne (talk) 15:58, 28 August 2010 (UTC)[reply]

One more thing worth mentioning perhaps.. there have been many cases in which herbal remedies have been studied, found effective, and the active ingredient identify and isolated. See History of aspirin for example. Once this has happened generally the herbal version falls out of usage in favor of the more consistent and controlled preparations. Lots of new-ager types will claim that herbals are "natural" and therefore not "drugs" and thus are somehow better and safer.. but this is nonsense. Plants can vary in potency, and will contain lots of ingredients other than the ones you want for medicine. When we manufacture a drug, we can make it contain just what we want, at a known dosage level. It's possible of course that some herbal remedies are out there which are effective and whose active ingredients have not yet been identified. But it's more likely that the ones that remain herbal remedies are there because they are not effective and have no useful active ingredients. Friday (talk) 16:23, 28 August 2010 (UTC)[reply]

However, it should be noted that natural willow bark salicylates, which are conjugated to sugars rather than just an acetyl group, have been shown to be more potent than aspirin, and do not cause gastrointestinal lesions and bleeding, a very widespread and potentially life-threatening side effect of long term aspirin usage. (See PMID 12244878, [1]) Yes, it's true - the stuff they sold in Ur 5000 years ago is better than the controlled chemical preparation that the FDA has certified for you!

So while your statement that regulated remedies are tested, while herbal remedies are not, might be true, it might also be true that medical regulation is a racket which stands between people with common complaints and ancient, well-known remedies to alleviate them, permitting them to pass by only if they hand over a large portion of their total wealth. Wnt (talk) 18:14, 28 August 2010 (UTC)[reply]

In nutrition, there is agreement that fresh fruit and vegetables are preferred over some combination of artificial vitamins and fiber. If it's all that "other stuff" (much of it unknown) that makes fresh produce more beneficial than isolated active ingredients, then might the situation be analogous for herbal remedies?--82.113.106.28 (talk) 16:35, 28 August 2010 (UTC)[reply]

When I trained as an aromatherapist, I was told that the synthetic lavender oil had none of the therapeutic properties of lavender oil obtained from nature. I don't have a reference for this (I no longer have access to the relevant research library) but have found this: adulterated oils and their effects. --TammyMoet (talk) 17:09, 28 August 2010 (UTC)[reply]

Well, aromatherapy is generally based on tradition rather than evidence, is it not? So I wouldn't be surprised to hear that many of them believe that the natural version has a magical "essence" that is lacking in a synthetic version- this is vitalism which is a common view in alternative medical practices. And yes, with food, most people will say that you're better off getting your vitamins from real food rather than vitamin supplements. This is, to some extent, to encourage people to eat healthy foods rather than eating crap and trying to make up for it with vitamin pills. Friday (talk) 18:01, 28 August 2010 (UTC)[reply]

Yes I accept that, but these days there is a growing body of research into aromatherapy (as well as other alternative/complementary medicines) which has been conducted "according to the rituals of the Church of Science" (as I like to call scientific research orthodoxy). I used to have access to the major UK repository of this research, but as I'm no longer a student I don't. It's not really acceptable to dismiss CAM as being not research based these days because of the research which is being conducted by, among others, Dr Peter Mackereth at the Christie Hospital, Manchester. The studies are, of necessity, small - who can match the research budget of GlaxoSmithKline, for example? but nevertheless it exists. --TammyMoet (talk) 18:36, 28 August 2010 (UTC)[reply]

Take a look at homeopathy, naturopathy, traditional Chinese medicine, orthomolecular medicine, culture-bound syndrome and acupuncture. ~A H 1^(TCU) 18:22, 28 August 2010 (UTC)[reply]

Wind on mars

Is the martian atmosphere sufficiently dense/energetic to move martian dust around? If so how long will it take for the tracks of spirit and opportunity to be obliterated? -- SGBailey (talk) 16:29, 28 August 2010 (UTC)[reply]

Spirit rover#Dust devils...small dust storms have cleaned the panels from Spirit. So yes, there's wind. Since there's enough to move dust around like that, I wouldn't think the tracks would last long at all...but I don't know. Vimescarrot (talk) 17:28, 28 August 2010 (UTC)[reply]

Also Climate of Mars#Wind. Vimescarrot (talk) 17:29, 28 August 2010 (UTC)[reply]

See Mars dust. Strong dust storms occur regularly on Mars with enough intensity to envelope the entire planet. ~A H 1^(TCU) 18:18, 28 August 2010 (UTC)[reply]

There is a panoramic image of one of the rovers taken over a whole winter. The tracks from roving in that area before the winter started are 100% visible and look very undisturbed. I talked to a Scientist Walter Goetz an he told me that the 9mbar only allow very fine dust particles to be carried around by the wind. The small cm high dunes would take year to create and the tracks would take decades or centuries to vanish. If there is a strong dust devil this might change, but most of the landscape on mars is changed very slowly. The dark tracks of the rovers can be seen from MRO for a very long time --Stone (talk) 20:32, 28 August 2010 (UTC)[reply]

The image I was thinking of is File:McMurdo panorama.jpg --Stone (talk) 20:37, 28 August 2010 (UTC)[reply]

The tectonic plates on mars also don't shift so it's not got mountains like earth to slow down wind. Mars has this one gigantic volcano that just keeps growing due to plates not shifting and lava keeps exiting on that same spot. Are you ready for IPv6? (talk) 08:09, 29 August 2010 (UTC)[reply]

sneeze

How powerful is a human sneeze. user--86.41.133.57 (talk) 17:28, 28 August 2010 (UTC)[reply]

According to sneeze, "Conservative estimates place the speed of release at around 100mph. However, the data collected from the 147th episode of Mythbusters titled 'Flu Fiction', concluded that the speed is closer to 35-40 mph, and launching from 15-20 feet." ~A H 1^(TCU) 18:16, 28 August 2010 (UTC)[reply]

That was a good experimental test of velocity and range. "How powerful" seems to need an answer in watts or other units of power, though an answer stating the total energy would also be relevant. Edison (talk) 20:19, 28 August 2010 (UTC)[reply]

Well, let us suppose that you were to expel an entire breath's worth of air - about 500ml, about 0.6 grams in your sneeze. So 0.006 kg of air at 40mph (18 meters/second) means that the kinetic energy you're creating is about 1 Joule. If your sneeze were to last for (let's say) about a half second - then you're looking at about a half of a watt - 1/400th of a horsepower. Not much. SteveBaker (talk) 04:46, 29 August 2010 (UTC)[reply]

...but if you are a 76 kg person your sneeze will propel you backwards at 1.4 mm/s. It's useful to know. Cuddlyable3 (talk) 13:48, 29 August 2010 (UTC)[reply]

Very helpful quantification. I would expect the momentary contraction of the chest and abdominal muscles to be more powerful for the brief instant of a sneeze, comparable to any other momentary bodily action like hitting or kicking something or throwing something, or jumping. I would expect a good hard sneeze could be several watts, since a person can momentarily produce a sizeable fraction of a horsepower, and it seems to accelerate the head in the opposite direction noticeably. If an astronaut in the International Space Station or other microgravity environment sneezed, the acceleration of his body should provide a measure. Edison (talk) 03:48, 30 August 2010 (UTC)[reply]

The sneezing astronaut will start rotating. He can cancel this by ejaculating. That is why NASA studied Sex in space. Cuddlyable3 (talk) 10:59, 30 August 2010 (UTC)[reply]

He'd only start rotating if he was inside a space-station or something. Outside in his space-suit there would be no effect whatever...other than a rather messy face-plate. SteveBaker (talk) 13:59, 30 August 2010 (UTC)[reply]

Do they have something built into the suit so that he can clean the inside of the faceplate so the astronaut can see? Googlemeister (talk) 14:32, 30 August 2010 (UTC)[reply]

sequence, chain, scheme

Just a quick question, do the phrases "decay sequence", "decay chain" and "decay scheme" all mean the same thing (when referring to radioactive decay). Thanks. Differentially (talk) 17:43, 28 August 2010 (UTC)[reply]

They're all related, but all refer to slightly different ideas. A decay chain is the set of different nuclides that are formed on the way to stability. Personally, I would say "decay sequence" was a synonym (and it's certainly used as such on Wikipedia) but looking around online some sources (e.g. here) use it to specifically refer to a plot of a decay chain on the N-Z diagram to show the changes going on. OTOH, a decay scheme is a more detailed look at an individual step in terms of the energetics and particular products involved. --81.158.2.129 (talk) 20:17, 28 August 2010 (UTC)[reply]

Synthetic cannabis

This a general request for further information about synthetic cannabis.

How do its experiential effects in humans compare to those of (natural) cannabis?
Has there been any further work done recently on its psychopharmacological mechanism of action?
Have any long-term physiological/psychological consequences of its use been determined?
Does anyone have any good recipes to share as to a really good mix of synthetic cannabinoidal agents?

(Note that this substance is still legal (and readily available) in much of North America and Australasia (but not in the UK). Thanks, Wikiscient (talk) 18:15, 28 August 2010 (UTC)[reply]

I think the quotes from Huffman are rather illuminative. The problem is that if you speak of psychoactive effects, they are so subjective that it would be next to impossible to define what is "good" or "bad" or even "the same". Perhaps with some fMRI...? But I doubt it's being done, because who's going to fund the study? As for other health effects, it is clear that natural cannabis contains highly useful and non-psychoactive compounds like cannabidiol, which alleviates nausea without creating a "high" - so conversely there should be healthy effects that these synthetic cannabinoids cannot duplicate. (Note that from the days of Marinol cannabis psychoactives have always been more legal than cannabis therapeutics, and cannabidiol remains strictly and severely illegal. However, ginger has not yet been banned, and may help with some forms of nausea) Wnt (talk) 18:50, 28 August 2010 (UTC)[reply]

[Note: Huffman is quoted as saying, "People who use it are idiots." Information on whether he believes this to be a cause or effect of using it, or both, and on what basis, would be welcome but peripheral to my core interest in this topic. And I am not interested here in any non-psychoactive compound]. Wikiscient (talk) 19:23, 28 August 2010 (UTC)[reply]

The psychoactive properties of cannabis may not contribute to its medical use, but oddly, its medical use might contribute to its psychoactive properties. As Huffman said, [2] "It's like playing Russian roulette. You don't know what it's going to do to you... You're a potential winner of a Darwin award." The same article says that Scalzo said "the symptoms, such as fast heart beat, dangerously elevated blood pressure, pale skin and vomiting suggest that K2 is affecting the cardiovascular system of users." Now bear in mind that cannabidiol and other components greatly suppress nausea, and that cannabigerol and cannabidiol lower blood pressure. Thus, by separating the high from the cannabis, you may take a known experience and turned it into an exercise in being terrified and dizzy-sick, if not worse. Wnt (talk) 20:32, 28 August 2010 (UTC)[reply]

To the first two points as far as I can tell (I've been trying to find sources for the article this week) there aren't any reliable reports. I'm sure that drugs-forum and bluelight will have some relvant threads where people have discussed their experimentation though. There are a couple of papers discussed in the safety section regarding some problems associated with its use but it's difficult to tell how different these are to problems with normal cannabis. It's also worth noting that some of the sythetic cannabinoids found (JWH-018 and JWH-073 for example) are very different in structure to THC and are reported to be full antagonists of the cannabinoid receptors whereas THC is a partial antagonist_{(haven't added this to the article yet)}. I'm no pharmacologist but it's not a big leap to think that they could have other effects on the body that the phytocannabinoids do not. It's not really a "substance" by the way, it's a mixture of chemicals sprayed onto some unidentified plant material. Smartse (talk) 23:39, 28 August 2010 (UTC)[reply]

You mean it's a full agonist, yes. Which is... interesting. Wikiscient (talk) 00:36, 29 August 2010 (UTC)[reply]

Err I guess so, like I said, I'm not a pharmacologist. Also note the very different effects of the enatiomers HU-210 and HU-211. HU-210 is hundreds of times more potent than THC, whereas HU-211 doesn't bind to cannabinoid receptors. It's unlikely that manufacturers are producing pure HU-210 without HU-211 as well. I'm not sure if any of the analyses of the products would be able to distinguish between these either. Smartse (talk) 09:59, 29 August 2010 (UTC)[reply]

Dragonfly Species Identification

This was in my backyard. It is in southern California, driving distance to coast the coast.

It has brownish-wings and bright red abdomen.

Even a genus or family would been appreciated.

From top

--Mathboy48 (talk) 20:23, 28 August 2010 (UTC)[reply]

I'm going to guess either a Flame Skimmer (Libellula saturata) or a Sympetrum species, perhaps S. illotum, both of which are which are found throughout California (though the latter tend to hold their wings angled downward when resting). Cf. this image of the former. There are a number of other possibilities, though, and precise identification depends on characteristics (such as size) that aren't really visible in the photo. You may find the field key here helpful. Deor (talk) 21:52, 28 August 2010 (UTC)[reply]

It had a length of approx. 2.5 in (35mm). Very helpful post--Mathboy48 (talk) 04:12, 29 August 2010 (UTC)[reply]

Guy being electrocuted

In this video, http://www.facebook.com/video/video.php?v=148725461813437&ref=mf a guy touches an overhead electric cable for a train and appears to have been electrocuted. You'll notice that as soon as he touched the wire, he doesn't let go until he collapses. I'm sure the electric current is responsible for that, but what specifically made it impossible for him to take his hand away from the cable? ScienceApe (talk) 23:19, 28 August 2010 (UTC)[reply]

Railways run on Direct current which has the effect of contracting your muscles so that you can't let go. This page[3] explains it better than I can. Alansplodge (talk) 23:25, 28 August 2010 (UTC)[reply]

The page seems slightly confused. I mentions that AC is more dangerous, and that DC is more likely to throw someone clear of the line, but sometimes causes the continuous muscle contraction that prevents letting go. Our article on Electric shock says the same. Dbfirs 01:11, 29 August 2010 (UTC)[reply]

Agreed. I think Alansplodge you may have got it the wrong way round. DC throws you away, AC causes muscles to contract so you grip the thing that is electrocuting you, which is why it's so dangerous. The OP may also be interested in Nikola Tesla and War of Currents 87.115.183.214 (talk) 01:32, 29 August 2010 (UTC)[reply]

You are quite right - I take it all back - see this page[4] - scroll down to "Type of circuit". Alansplodge (talk) 15:52, 29 August 2010 (UTC)[reply]

Look, it's simple. If someone wants you to keep away from a DC high-voltage line, they tell you that DC is more dangerous than AC because it can cause your muscles to freeze in position (which is true -- they might freeze in a way that throws you away from the wire, but they might not). If they want you to keep away from an AC high-voltage line, they tell you that AC is more dangerous than DC because it can stop your heart (which is also true). They're both dangerous, and especially so in the case of railway power systems, which operate at high voltages and can supply high current as well.

Different railways use both DC and AC power. On DC systems the voltage is generally in the range of 600 to 1,500 V; on AC systems it's usually even higher, up to 25,000 V and even higher in a few systems. --Anonymous, 04:34 UTC, August 29, 2010.

~~Can anyone provide a link to the video that does not require surrendering one's e-mail address to Facebook?~~ I think this is the video. According to this site the overhead cable carries 25kV AC which would be enough to strike an arc even before the man touched it. After that the man would have to move a considerable distance away from the cable to break the arc. On the video it looks like there are two successive arcings and that the current fuses his right arm and shoulder joints in upstretched position. Cuddlyable3 (talk) 23:18, 29 August 2010 (UTC)[reply]

Yes, that's the same video. Dismas|^(talk) 01:26, 30 August 2010 (UTC)[reply]

Protective relays on AC circuits sometimes are set up to interrupt fault current, then reclose the circuit one or more times in case the fault was a momentary one such as nearby lightning or something that burned clear. That might explain the two shots of electricity seen. At 25kv I would not rely on DC or AC to safely throw someone clear. I would not rely on either one not to cause a hand co clench a conductor even at 240 volts. In the "War of the Currents" tests of the 1880's, DC seemed to be safer at 100 or 200 volts. The argument then was that high voltage in general had more capability to electrocute than lower voltage, and that at a given voltage AC was more lethal than DC. This is not to say that DC or some arbitrary low voltage is "safe." Edison (talk) 03:33, 30 August 2010 (UTC)[reply]