Wikipedia:Reference desk/Archives/Science/2012 July 2

= July 2 =

strange respirator
I saw this strange respirator/face shield combo. It looks like it may be disposable and it doesn't look like forms a very tight seal around the face. It also looks like it would be prone to fogging up quickly. It is apparently used by the CDC. Does anyone have any more information about this or how it works? Here is the picture-  http://upload.wikimedia.org/wikipedia/commons/8/86/Influenza_virus_research.jpg  — Preceding unsigned comment added by Wrk678 (talk • contribs)


 * Looks like a very low-end device to me, just with a fan to blow air from the room into the face mask. Obviously not what you would want with a deadly microbe in the room (note the exposed ears), but perhaps enough if the chemical reaction you're working on may create a slight volume of irritating gas. StuRat (talk) 02:06, 2 July 2012 (UTC)


 * There could easily be a filter in there somewhere. The lack of a tight seal around the face is a problem, though. I agree it's probably designed as a kind of wearable fume cupboard rather than as an infection control measure. --Tango (talk) 11:32, 2 July 2012 (UTC)


 * Looks like they rely on the positive pressure created by the fan to blow air out from the edges of the face mask, preventing air around the mask from seeping in. Judging from the location of the air intake, you'd better be careful not to pass gas while using it. :-) StuRat (talk) 18:12, 2 July 2012 (UTC)


 * BSL-3 isn't for instant-death-on-contact toxins and isn't usually designed for 100% body coverage. For this particular material being handled (influenza culture, according to the image-description), inhalable mists and perhaps small splashes are probably the hazards of interest, so physical barriers don't need to block from other directions as much, and positive air-flow from "away from the front work-area" (PAPR) prevents chemicals from getting to the breathing area. As long as there is positive air-flow, fogging is not any more of a problem than in other full-face breathing masks (diving, etc.) because the humid exhalation is constantly blown away out of the face-mask. But safety-equipment vendors will be happy to sell you all sorts of anti-fog sprays and tout all sorts of special coatings and such on the non-disposable models. DMacks (talk) 22:03, 2 July 2012 (UTC)


 * Presumably they are working with an ordinary flu strain, already out in the public, so the risk both to the researchers and public, should it get out, is fairly minimal. StuRat (talk) 18:19, 3 July 2012 (UTC)




 * Influenza A is listed as BSL-2. I'll embed the image here (makes it easier to access the WP page for the image and its links) and include a key part of the file-description in the caption to help us decide how "ordinary" it is vs requiring any enhanced protection per the descriptions of BSL-3. And this is all with hindsight information about the agent and its effects. Comparing the image info to the timeline of Spanish flu research, it doesn't seem like it was fully understood at the time. Handling a not-fully-characterized agent that had killed 3% of the world population seems like it would merit a cautious approach. DMacks (talk) 23:19, 3 July 2012 (UTC)


 * Would Spanish flu be deadly today, considering that most people who were highly susceptible already died, leaving only those of us who are most resistant ? Also, if it did get out, couldn't we create a flu vaccine effective against it ? StuRat (talk) 07:31, 6 July 2012 (UTC)

Can you survive without drinking fluids?
When I was checking my diet, I was surprised to learn how much water is present in the food I consume each day. At first I actually forgot to enter the 4 litres of water I drink each day and I got a warning that my fluid intake was too low. However it was still more than 1 liter (e.g. the 300 grams of brown rice I ate becomes 800 grams after cooking so this alone yields half a liter of water). So, I was wondering if the water that is present in bread, cooked rice, vegetables etc. etc. would be enough for the body if it is the recommended minimum amount of 1.5 litres. Or could it be that the more you eat, the more you need to drink to survive? Count Iblis (talk) 01:06, 2 July 2012 (UTC)


 * Koalas don't drink water if their leafy diet is moist enough, which is most of the time. But I don't think humans could easily do it eating a normal diet, like the stuff you list. That's stuff you are already eating and it doesn't give you enough water, so doubling the amount of food you eat just to get enough water would not be practical. But I expect you could easily survive without actually drinking water if you changed your diet to include more moist fruit, like eat a watermellon and a few oranges every day or something. Vespine (talk) 01:18, 2 July 2012 (UTC)


 * I suspect (and please nobody try this - just musing) that one could survive indefinitely in terms of fluids at least by eating a couple of large watermelons per day. --Kurt Shaped Box (talk) 01:22, 2 July 2012 (UTC)


 * It wouldn't be a very balanced diet, but you could probably keep from dying of dehydration, at any rate. StuRat (talk) 02:13, 2 July 2012 (UTC)


 * You'd think so, as watermelons can be comprised of upwards of 90% water and are rich in electrolytes. In reality though, watermelons also have a diuretic effect, making them impractical for maintaining hydration long-term.  That level of consumption would also probably mean you were getting the vast majority of your calories from sugars, which would grow problematic quickly with regard to body weight, blood sugar levels and metabolic homeostasis in general.  You could also end up turning your skin yellow-orange from carotenosis (watermelons are high in beta carotene), though this is an otherwise harmless condition.  All of that said,  for most in good health it would be possible to survive without hydration via pure water, provided you had a varied and tightly regimented diet. Snow (talk) 02:47, 2 July 2012 (UTC)
 * This idea of watermelons being a diuretic is surprising, considering the considerable quantities of mellon consumed in hot countries such as Australia and Saudi Arabia. The fact is, as they are almost entirely water, for every 1 kg of mellon you eat, that's 1 litre of water you don't need to drink.  My wife is on chemotherapy for her cancer.  Consuming sufficient fluid is key to maximising the ratio of good effects of chemo (shrinking tumours) to bad effects (side effects) by flushing the chemo metabolites out.  A local cancer support group advocates watermellons as a duretic, so she bought some.  But she found she didn't like them, so I ate them (one half a good sized melon per day for a week).  They certainly had no durectic effect on me, especially considering they are 95% water anyway.  We asked her (very experienced) doctor - he stated that the idea of watermellons being a duretic was utter nonsense.  I did a search of the internet - there are naturapathy and home remedy web sites that claim watermellons are a duretic, but the only "trustworthy" i.e., referenced article I could find was a report in a US newspaper published a few years ago.  Ratbone58.169.255.232 (talk) 03:27, 2 July 2012 (UTC)
 * I understand a healthy skepticism with regard to homeopathic remedies, certainly, but the idea of a watermelon being a diuretic actually makes sense, if only because of the glucose - mind you, in a healthy person with an average diet, glucose is a small factor, but when you're consuming that much sugar, it can inhibit the efficiency of a loop of henle from using osmotic gradients to reclaim water, which then instead is passed with the more dilute urine.  That's without even factoring in the possibility of diabetes, which, with an all-watermelon diet, is gonna become a possibility!  Notice also that while watermelons do posses electrolytes, they aren't present in as high a ratio as you usually get with other fruit, or even other melons, so the urine is going to be further dilute if you're entire diet consists of watermelon.   So is it the same type of diuretic as, say, caffeine? Nah, but if you eat nothing but, you're gonna be getting pretty familiar with the nearest urinals.  As to why it's so popular in hot countries, the answer is the same as why iced teas, chilled soda, cool beer, ice cream, and snow cones are all popular in those circumstances, despite being likely to dehydrate you in the long run - it's a refreshing, thirst-quenching, energy-packed treat.  And short term it does hydrate you more.  It's spread was also assisted benefited by way of historical economics too, since it was a cheap and efficient means of resupplying a labour force with calories and short-term hydration.  Hence the melon's association with slave labour.  In fact, in this way it would have had the same effect as beer did in earlier epochs of slave-labour - gives a burst of energy for the working hours and then leaves the worker drained when it comes time for rest - in the case of beer because of the alcohol content. In the case of watermelon though, it's because glucose is a simple sugar - meaning that it is assimilated into useful energy quite efficiently by the body and this does not maintain blood sugar and energy levels well over the long-haul.   But yes, for your wife's needs there are definitely better options,  I'm sure.   But as to the issue of the proposed watermelon diet - I wouldn't recommend it for that purpose either! Snow (talk) 05:01, 2 July 2012 (UTC)


 * How much water you need to drink depends on whether you look short term or long term. The amount of fluid is not dependent on how much food you eat (because the large intestine recovers vitually all water used in digestion).  In the very short term, how much you need to drink is dependent on ambient temperature and humidity - particularly if ambient temperature is above body temperature (~36 C).  This is because at high temperature, the body cannot control core temperature by radiation and conduction and must resort to sweating.  If the ambient is near to or above 36 C, then no heat is lost via radiation and conduction - sweating is the only way, and rises dramatically.  I have worked oudoors in remote parts of Australia.  I usually need only drink 300 ml of water per day when working indoors and up to 35 C or so, but when working in 45 C I drink several litres per day, and at 50 C I need to drink continuously.  You can only keep this up short term.  Longer term it appears that urinary tract problems (infections, kidney stones) rise in probability unless your kidneys get a good flush - the rule of thumb is that if your pee stream looks clear, you are drinking adequately, if yellowish, you are not.  The common "medical" advice to drink x litres a day (I notice that x varies quite a bit from reference to reference) is nonsense - what matters is how much you pee.  This rule means peeing about 500 mL per day (average weight person), and up to 750 mL per day if physically working hard) If you are cold, you don't sweat, so you only need to consume (drink plus water in food) enough to pee about 500 ml per day.  But if you located in an ambient of 45 C, you will sweat roughly 3 litres/day (average sized person, light work), so you need to drink 3 + 0.5 = 3.5 litres per day.  If working physically hard at 45 C, it will be Y + 0.75 l/day, where Y may be very much larger than 3 l/day.  Ratbone60.230.225.247 (talk) 02:25, 2 July 2012 (UTC)

[Discussion on body temperature typo removed and typo corrected] Ratbone124.182.182.130 (talk) 02:12, 3 July 2012 (UTC)

Yes, you can survive without drinking as do thousands of hospital patients being hydrated by IV drip. DriveByWire (talk) 16:04, 2 July 2012 (UTC)

Thanks for the answers! So, if it doesn't depend on how much you eat, you should be able to get the necessary amounts of water from eating relatively dry stuff alone like bread and rice, as I'm close to 1 liter from such sources alone (I also get something from fruits and vegetables, bringing the total over 1 liter). However, I do feel I need to drink a lot of water, though. Count Iblis (talk) 16:20, 3 July 2012 (UTC)


 * It does matter how much and what you eat:


 * 1) Excess fluid is needed for the digestion process. The amount of fluid your body can add to your digestive tract is limited, so you either need to eat moist food or drink fluids.


 * 2) Your body must maintain a balance between water and salt and other solutes. Thus, when you consume more of those items, you need to consume more water, to dilute them. StuRat (talk) 16:37, 3 July 2012 (UTC)


 * You might also be interested in metabolic water - 300 grams of rice (dry weight) gets turned into ~ 150 ml of water. IIRC this is an important source of water for desert animals like kangaroo rats. SmartSE (talk) 17:56, 3 July 2012 (UTC)


 * This brings to mind a recent TV report in Canada claiming that the eight glasses a day guideline is actually a myth, and nobody can find the source of this claim. Most food is likely to contain water, though if you're trying to drink more than 1.8 litres of water at once, beware fatal water intoxication.


 * From fluid balance:


 * The common misconception that everyone should drink two litres (68 ounces, or about eight 8-oz glasses) of water per day is not supported by scientific research. Various reviews of all the scientific literature on the topic performed in 2002 and 2008 could not find any solid scientific evidence that recommended drinking eight glasses of water per day. ~ AH1 (discuss!) 18:00, 3 July 2012 (UTC)

Suppositories - and the people who eat them
Just something based on a silly conversation I had today, and granted, there may not really be a good answer for this (but here goes)... Does anyone know if it's actually common for people who've been prescribed suppositories by their doctor to return a couple of days later and complain that the things are really difficult to swallow? Or is it more of an apocryphal tale? --Kurt Shaped Box (talk) 01:13, 2 July 2012 (UTC)


 * I suspect so, since there are plenty of oral laxatives, too, an inserting any med into the rectum seems very odd. So, those unfamiliar with them who don't read the label might very well swallow them. StuRat (talk) 02:11, 2 July 2012 (UTC)


 * On a quick look, this supports the idea that patients do sometimes do nonstandard things with medication designed to be delivered this way; whereas this one, perhaps surprisingly, dismisses as probably apocryphal the whole idea. I strongly suspect that a more structured search on PubMed or whatever would find more articles confirming that the problem is real. For some reason the BMJ Christmas edition springs to mind here ... Best wishes DBaK (talk) 07:49, 2 July 2012 (UTC)


 * On a related note - anyone got a reference for the 'I eat a tampon every month but it has no effect on the duration of my period' woman? Or the 'both my legs and one of my arms hurt when I touch them' guy (who actually has a broken finger)? I do suspect that these are urban legends. --Kurt Shaped Box (talk) 23:00, 2 July 2012 (UTC)
 * The former sounds like a "blonde joke". The latter was in Henny Youngman's catalog of one-liners. As regards eating those things, the article implies that it would be harmless, albeit probably not very effective. ←Baseball Bugs What's up, Doc? carrots→ 23:25, 3 July 2012 (UTC)
 * It occurs to me, Bugs, the suppository would still get where it needed to go. Someguy1221 (talk) 02:01, 4 July 2012 (UTC)

Turkey Turquoise
Added section header Rojomoke (talk) 06:39, 2 July 2012 (UTC)

Many big E-seller sites clients when describing their merchandise are confusing the terms for colors with the synonymns for minerals, such as silver, tibetan silver, or turquoise. I frequently see the term "turkey turquoise" which is not covered in wikipedia, except for word origin for turquoise. Please clarify the term "turkey turqoise" as it seems to include black and white, as well as many other color stones. Buyers have no hardness testing standards to check the main characteristic, while being subject to the technical correctness of being a turquoise color. If you can get E-seller sites to accept standard definitions it would be most helpful.

Thank you, 75.186.36.70 (talk) 06:20, 2 July 2012 (UTC)
 * http://www.internetstones.com/turquoise-gemstone-jewelry-gallery.html has a mention of it. I see Ebay has lots of listings with turquoise in quotations like 'ranch fur' which is artificial fur. They may have many artificial types of 'turquoise' as well.--Canoe1967 (talk) 17:53, 2 July 2012 (UTC)


 * turquoise is the French word for 'Turkish', because the stone was first brought to Europe through Turkey. Could "Turkey turquoise" mean stones that were worked by Turkish jewelers? —Tamfang (talk) 23:32, 6 July 2012 (UTC)

Restricted FTL Without Causality Violation?
Ok, I've been brainstorming ideas for a story setting featuring faster than the speed of light interstellar travel, and trying to avoid 'easy' causality violations as a result. I'm wondering if this is possible.

The key trick I'm considering is this: in this setting, the FTL technology itself is hopelessly out of the realm of humans, but rather consists of automated ships flying fixed routes, that people merely piggyback on. So the question is this: can there been a configuration of fixed routes, and intervals, and speeds for FTL, that will allow FTL to take place, but which will avoid creating observable causality paradoxes (at least, without substantial effort)?

Some thoughts I'm considering: 1. How about setting the speeds of the Ships such that a 'round trip' will always arrive after one has set off? Is this possible, or will this lead to a contradiction?

2. How about changing the network shape so that certain causality violations cannot happen? I'm not sure how, but maybe a network of routes without any loops in it would work?

3. How about having it so that all star systems the Ships go to are *stationary* relative to each other?

Any other ideas? Would these suggestions work?--Fangz (talk) 11:45, 2 July 2012 (UTC)
 * Even if FTL travel were possible, it would not allow for traveling backwards in time for two reasons, first that the experienced time would be imaginary, not negative, second that even if someone traveling FTL would experience negative time flow, that would make that person younger, but he/she would still arrive at his/her destination after takeoff. That in itself creates a contradiction, because if someone becomes younger, he/she will never have departed in the first place. The problem with describing this scenario is not that the technology is not available, but rather it is fundamentally impossible and therefore cannot be described in terms of relativistic physics. It's like asking what would be the circumference of a square circle. If you still want to write such a story, you'll have to make up your own physics, so asking at the science desk may not be of much help. - Lindert (talk) 12:45, 2 July 2012 (UTC)


 * Well, the issue isn't so much 'can FTL be done with current physics'. The question is 'can FTL be sealed into a black box so as not to imply various large and disruptive effects on the rest of the story'. Assuming as much of relativity etc is preserved as possible, the ideal is that we have a situation where (ignoring how this is done), people can go to some distant star and back again in a reasonable time, without logically implying that they can make a phone call to themselves in the past, etc. --Fangz (talk) 13:15, 2 July 2012 (UTC)

See here for a detailed discussion. Count Iblis (talk) 16:50, 2 July 2012 (UTC)


 * It's actually not that hard to invent a way of doing FTL without violating causality. The easiest way, I think, is to assume there is a preferred reference frame (an "ether"), and only permit travel that goes forward in time in the preferred reference frame.  That way it will still be possible to appear to go backward in time, but it will not be possible to do a loop that brings you back to the starting point earlier than you left. Looie496 (talk) 17:37, 2 July 2012 (UTC)


 * I suggest using the many worlds hypothesis. Then, when you go back in time, you appear in another universe, identical to our own up to the time when you arrived.  You are then free to mess that universe up as bad as you want to, since it won't affect ours.  You can even return to our own universe, but not at a point earlier than when you left.  You could then use this other universe as a simulation of what will happen in our own, given certain actions on your part. StuRat (talk) 18:01, 2 July 2012 (UTC)

Your biological clock can travel faster than light in vitrified cryonic suspension. However, the clocks everywhere else will be tens of thousands of years in the future. 75.166.192.187 (talk) 19:18, 2 July 2012 (UTC)


 * If the technology was available, I'd make a wormhole, put one end on Earth, the other on a spaceprobe, send it on a time dilated 10 year round trip journey, and plan to walk through it when it arrives 50 years later. When 50 years older me walks through the stargate only 10 years later I'd ask him what my children's names are and then not name them those names. Sagittarian Milky Way (talk) 20:09, 2 July 2012 (UTC)


 * I like the idea of wormholes with the many worlds hypothesis. That way, I can ask my kind friends from the future to please work out the tech, then send me back a gram of gold as proof it works, and because this one moment in time corresponds to a bazillion possible futures, it'll add up to a massive pile of loot.  The problem is, trying to calibrate it so that the incomprehensibly large number of possible followers of this missive in possible futures don't end up sending so much gold that it collapses into a black hole around the Earth, at which point it wouldn't be gold any more.  But I suppose I won't get gold back from the possible universes where the Earth collapsed, only the ones where it didn't, which means that the pile should be manageably small, only a few cubic miles...  hmmm, but then the others get the chance to send their share after all... maybe there's a happy medium where there's, like, a 10-10 -10 chance that the Earth doesn't collapse into a gold-fueled black hole, reducing the amount of gold received to what just barely allows that chance that somebody survives? ;) Wnt (talk) 20:41, 2 July 2012 (UTC)

Making a primitive bathtub
Let's say the world runs out of oil, natural gas, coal and all that and we're all back to 15th century living. I was wondering if there would be any way to construct a functional bathtub so that I could at least enjoy that creature comfort. The heat source would either be directly from a fire underneath, or by taking rocks out of a fire and placing them in the tub, probably with a loose buffer between the rocks and the bottom of the tub. Does anyone have the slightest clue how you might fashion a tub like this? I suppose the simplest solution would be to drag a bathtub out of a derelict house and use that. But is it possible to create a tightly-joined wooden tub, for instance, that won't be horrendously leaky? Thanks. Vranak (talk) 18:15, 2 July 2012 (UTC)


 * Carve one out of a tree trunk, sand it, and seal it with oil (animal grease will work). This would work better with the "hot rocks dropped into the water" method.  Flip it over to drain it, or add a drain and plug.  (Of course, during the 15th century they could make elaborate ceramic bathtubs, but you had to be rich to afford one.)  StuRat (talk) 18:34, 2 July 2012 (UTC)


 * I hate to state the obvious, but in the actual "pre-technological" past, nobody used bathtubs that had active flames or heat sources as part of them, for the fairly obvious reason that there are real risks of burning or scalding associated with that. It's much easier to heat the water first and then add it to the tub, mixed with as much cold water as you need to keep things at a desired, non-cooking temperature. The same as we usually do now, frankly — we just have elaborate ways of moving the hot and cold water from tanks that you can't see. You can make basins out of wood, ceramics, or metal with technology that is well prior to the 15th century (there are evidence of this technology back to the Ancient world, it isn't a new thing), and can heat water similarly. --Mr.98 (talk) 19:06, 2 July 2012 (UTC)


 * Whoo there! If the world runs out of oil, natural gas and coal then you're going to compound the problem by burning what combustibles are left.  If you look at Jenny Agutter here . She seem very happy in a naturally formed, solar heated Billabong (there are better images of her than this  but they are a wee bit too revealing). What more creature comforts do you need than that? --Aspro (talk) 19:10, 2 July 2012 (UTC)


 * If you want to have a proper bath, I'd forget about 15th-century technology, and go back a lot further - the Romans had a better approach. And yes, the water was heated by 'active flames', along with the rest of the building. AndyTheGrump (talk) 19:42, 2 July 2012 (UTC)


 * I'm assuming they want to make this tub themself, not using the skills of metal smelters or a Roman engineering team. StuRat (talk) 19:57, 2 July 2012 (UTC)


 * By active flames, I just meant, nobody sits in an individual bathtub with a fire underneath it. For water with a very large volume, maybe you could get away with it. But it would be hard to control to temperature, easy to get burnt. There's a reason that for small basins, people have nearly always heated the water separately and then mixed it with cold water to get the right temperature. --Mr.98 (talk) 21:43, 2 July 2012 (UTC)
 * Japanese Goemon bath (named after Ishikawa Goemon) is a kind of bathtub you described. A metal bathtub made of iron, with a fire underneath it. --Kusunose 04:09, 4 July 2012 (UTC)


 * Running out of fossil fuels doesn't mean going back to 15th century technology, but going forward to 20th or 21st century tech. Try a solar hot water heater, for example. Wnt (talk) 20:25, 2 July 2012 (UTC)


 * Or just using wood, which is renewable. --Mr.98 (talk) 21:08, 2 July 2012 (UTC)

Thanks everyone, very interesting answers so far. Vranak (talk) 00:42, 3 July 2012 (UTC)


 * Wood is a pretty good thermal insulator, so externallly heating a wooden tub of water is not going to work. Do what is a Japanese tradition.  Use your wood fire (which can be the fire you use to cook with) to heat rocks.  When rocks are hot, place in wooden tub of water, or natural pool of water.  Rocks will heat the water very effectively but are too hot to step or sit directly upon, so place a piece of wood on top of the rocks.  Ratbone124.182.182.130 (talk) 02:18, 3 July 2012 (UTC)
 * Rocks "heated in a fire" tend to have soot and ashes attached, which would leave a lot of crud on the bather. If the rock is really hot, it might fly apart or burn the bather if it came in contact. A separate water heating vessel is highly desirable. Before running water and water heaters were common, a less-than wealthy household might have used a collapsible canvas bathtub with a wooden supporting frame, or a metal tub just big enough to sit in, if not stretch out, and heated water in a pot on the stove, or in an open copper boiler attached to the wooden cookstove. The whole family might use the same tub of water. Bathing even a child in "almost cold water" was apparently common in the 19th century. Edison (talk) 14:34, 4 July 2012 (UTC)

Traditional Japanese bathtubs are made of wood. See Furo. --Kusunose 04:25, 4 July 2012 (UTC)

Local robot SETI
The question on the cost of interstellar colonization veered into local robot SETI, after taking a turn into statistics education:


 * Hypothetically, if machines are going to colonize the galaxy, then I wonder which planets / moons they would prefer? In terms of building durable, long-lasting technology there would seem to be some real advantages to avoiding both weather and biological life. Robots, at least the simple ones that humans have been able to make, tend to operate best is simple and predictable environments. A robot colonist first arriving in the solar system might well think that the Moon or Mars is a more inviting first stop than a place like Earth. Engineers motivated by "moral" concerns might even tell the robots to always avoid planets (or even whole systems) with biological life. Dragons flight (talk) 23:57, 30 June 2012 (UTC)


 * Position preferences are things that life has, but I'm not sure if machines would have strong position preferences. 75.166.192.187 (talk) 01:31, 1 July 2012 (UTC)


 * Large robots might prefer asteroid belts or planetary rings, as those provide lots of materials, sunlight (for solar power), and less gravity/atmospheric resistance to fight against (especially if they want to leave orbit). Smaller bots would have insufficient shielding to protect their electronics, control systems, etc., from radiation damage and micro-meteors. StuRat (talk) 02:26, 2 July 2012 (UTC)


 * That is why Asteroid 2010 SO16 should be explored.

Is there a better target for local robot SETI exploration than Asteroid 2010 SO16? 75.166.192.187 (talk) 19:15, 2 July 2012 (UTC)


 * Well, if it's just a single robot which lacks the ability to move to other asteroids, moons, and planets, you might want it to explore a large object, like the Moon or Mars, since it will soon explore all of any one asteroid. However, if it can move on to others, or has the ability to replicate itself and send it's copies on, this no longer applies.  Also note that Asteroid 2010 SO16 is only interesting because of it's unusual orbit, not because it shows any promise of extraterrestrial intelligence.  When searching our solar system for life, the best bet is planets and moons large enough to have an atmosphere and/or oceans. StuRat (talk) 19:47, 2 July 2012 (UTC)


 * This may be too speculative, but wouldn't a single large robot want to keep hidden from nuclear capable biological organisms? Wouldn't it attempt to communicate by placing artifacts in impossibly unnatural orbits just out of reach of biological civilizations without global cooperation, or at least some semblance of it? 70.91.171.54 (talk) 02:50, 3 July 2012 (UTC)

The smart thing to do for a machine civilization is to first colonize their own solar system. Then, instead of attepting to directly move on to another solar system, they could attempt to detect signals from another machine civilization. There is then the possibility of traveling directly to another machine civilization by uploading the software and the design of the machines to the other civilization, or to download a copy of another civilization and implement that civilization here.

This way, a civilization can jump from one place to another place millions of lightyears away. The entire output of the star is available for transmitting the data, so an astronomical high data rate can be achieved over long distances. Count Iblis (talk) 16:14, 3 July 2012 (UTC)
 * I think nonbiological machine civilizations would be more likely to get along with each other than life-based civilizations, and they would also want to keep life around, but at a distance, because they would admire the Darwinian nanomachines of life. But they would also see life as dangerous and unpredictable, I would think. I doubt a machine civilization would want to stop life from colonizing other planets in the same or different solar system, but it seems very unlikely that they would take any steps to help unless the life made some really concrete progress on reducing nuclear weapons. If the machines did not feel vulnerable, then they might want to help in the same way a gardner might want to make cuttings of a favorite tree for a different garden. 75.166.192.187 (talk) 22:47, 3 July 2012 (UTC)

Energy in a mass of fluid
Im guessing the components of energy in a mass of fluid are kinetic energy, potential energy and internal energy. If so, what is the source of each of the components of these energies? 176.250.196.132 (talk) 19:18, 2 July 2012 (UTC)
 * Kinetic: motion of molecules, from weather, heat, life and seismic disturbances; potential: gravitation and binding energy of nucleons; internal: heat, turbulence, laminar flow. 75.166.192.187 (talk) 19:26, 2 July 2012 (UTC)
 * Heat being the same as kinetic motion of molecules, added to molecular vibration and rotation, of course. Ratbone124.182.182.130 (talk) 02:22, 3 July 2012 (UTC)
 * There is of course also turbulence kinetic energy. ~ AH1 (discuss!) 17:47, 3 July 2012 (UTC)

Why isn't solid combustion a popular topic?
There's talk of engines that run on biodiesel, ethanol, vegetable oil, algae oil, restaurant deep fryer crap, grease, crud so viscuous it needs to be heated to flow, why not very fine powders like sawdust? Sagittarian Milky Way (talk) 20:44, 2 July 2012 (UTC)


 * Feeding into into the combustion chamber is more difficult, but not impossible. The extra weight and complexity involved in using something like Archimedes' screw to feed it in makes it not a very good choice for a vehicle, but it might work for heating a building (say the saw mill where the sawdust is generated). StuRat (talk) 21:48, 2 July 2012 (UTC)


 * To expand on that, a powdered fuel might require larger diameter injection tubes, would have to be air-pumped through the engine, it might clog the airtight valves around the piston, and you'd need to find a lubricant for the piston that didn't gunk up with the powder. A sawmill might find it easier to burn off excess dust in a steam-powered generator designed to handle it without exploding. Someguy1221 (talk) 22:03, 2 July 2012 (UTC)


 * Gasoline is chemically stable at high temperature, burns at a predictable rate, and does not burn at all in the absence of oxygen. On the other hand, sawdust decomposes to charcoal at high temperatures and has a huge surface-area-to-volume ratio, meaning that it burns explosively when spread around the air at the right density.  Sawdust particles are irregularly shaped, meaning there's going to be large amounts of air trapped inside, so combustion rate is difficult to control.  --140.180.5.169 (talk) 23:26, 2 July 2012 (UTC)
 * Technically, nothing burns in the absence of oxygen. But yes, you're right about sawdust not burning in a manner conducive to automobile engines. In fact, I'm not sure there's any solid fuel that would work well in an internal combustion engine. As I see it, the easiest way to get an automobile running on solid fuel would be to introduce coal-fired steam engines, but that brings with it a whole host of other problems. Evanh2008 (talk 02:29, 3 July 2012 (UTC)


 * The above post by 140.180.5.169 is a little misleading, as hydrocarbon fuels (eg gasoline, diesel) also decompose at high temperatures - if temperature is high enough, what you get is a mix of monatomic hydrogen and carbon.
 * A perhaps more precise answer to the OP's question is that actual combustion can only occur when the fuel is in gaseous form. For fuels like gasoline and diesel, all that is required to get from the liquid to the gaseous form is vaporisation.  Combustion then occurs at a very predictable and controlled rate and proceeds to virtual completion (ie exhaust is almost entirely water vapour and carbon dioxide.  Any solid fuel, like wood, that cannot be vapourised or sublimated (http://en.wikipedia.org/wiki/Sublimation_(phase_transition)) must first be pyrolysed, i.e., chemically (driven by heat) separated into gas components, which can be burnt.  This takes too much time in an engine, is too variable, and gnerally won't be a complete conversion.  As well as the injection mechanical issues mentioned by StuRat, pyrolysation of wood results in an unburnable component, ash, as well as the gas components.  It is quite simple to remove accumulating ash periodically, or by conveyor belt etc from a furnace at atmospheric pressure.  However, removing ash from an internal combustion engine is likely to be difficult, and will cause extremely rapid wear.  Which leads to how wood, swadust, and wood flour HAS been succesfully used to run an IC engine:-
 * Producer Gas method (http://en.wikipedia.org/wiki/Producer_gas)- wood is burnt in oxygen starved conditions in a vessel at atmospheric pressure. The resulting fumes, which are carbon & hydrogen rich, are sucked into a conventional piston engine. Every few 10's of miles you add more wood and dump the ash.  Many early IC engines were designed to run on producer gas.  During World War 2, gasoline use in Australia was restricted to military, police, and emergency services.  Ordinary citizens purchased producer units, usually installed on trailers, to run their cars.  It was very succesfull, though the engine power output was quite a bit less than with petrol.  Producer units are simple low tech - many folk made their own.  You may enjoy http://www.lowtechmagazine.com/2010/01/wood-gas-cars.html
 * Ratbone124.182.182.130 (talk) 02:51, 3 July 2012 (UTC)
 * Apparently there are designs for gunpowder engines. Mythbusters tried it on a 2006 show but it didn't work.Sjö (talk) 06:07, 3 July 2012 (UTC)
 * We tried a related concept in high school and it worked just fine. Short Brigade Harvester Boris (talk) 20:04, 4 July 2012 (UTC)
 * One way solid fuel is used is in a pulverized coal-fired boiler, which can be used to generate steam to turn turbines. This involves a boiler and a condenser (which may need cooling towers) - OK in a power station or perhaps in a ship but a bit bulky otherwise. So why not burn the pulverized fuel in the turbine (as in a gas turbine), or in a reciprocating internal combustion engine? The answer is that the hot ash erodes the metal, which is tolerable in a boiler but very quickly ruins a nicely machined engine. A satisfactory solution has yet to be found (there are reliable sources that confirm this ,). Also you're not allowed to vent the ash to the environment along with the gaseous combustion products. --catslash (talk) 23:34, 4 July 2012 (UTC)

Genes coding for brain stuff
What percentage of the human genome codes for brain related stuff, and is this number typical for mammals? 65.92.7.168 (talk) 20:52, 2 July 2012 (UTC)


 * According to the Allen Institute for Brain Science, 82% of human genes are expressed in the brain. It should be noted that most of these genes will also be expressed elsewhere in the body. A similar number is found in monkeys, in this paper, although you have to dig through their methods a bit to figure that out. Furthermore, that papers shows that less than 10% of genes in the brain are even unique to it. I'm guessing the inspiration for this question is that you are wondering whether smarter animal means more genes that work in the brain, but that is unlikely to be true. What's far more likely, and what researchers are actually looking for, are changes in those genes, that are already expressed in the brain. Someguy1221 (talk) 21:15, 2 July 2012 (UTC)


 * Yes, strange as it seems, it appears that one gene can do different (apparently unrelated) things, in different parts of the body. The FOXP2 gene comes to mind.  StuRat (talk) 22:36, 2 July 2012 (UTC)


 * And that doesn't even take into account alternative splicing. A single "gene" could potentially encode thousands of distinct proteins. Most studies of the transcriptomes or proteomes of specific tissues do not distinguish between the different isoforms, unless alternative splicing was the precise focus of the study, which is rare. So when a paper says that 90% of the genes expressed in the brain are also expressed in the liver, we can't say for certain the same isoforms are expressed in both tissues. It's possible reanalysis of existing deep sequencing done on cDNA could reveal the answer in this specific context. Someguy1221 (talk) 00:46, 3 July 2012 (UTC)


 * There's not actually a lot of difference between a brain cell, and a skin cell, or for that matter any cell. They all have nucleus, mitochondria, membrane, etc, etc.  That's why >82% of genome expression is common.  What is more important for brain functionality is the interconnection of neurons.  On a macro scale it is genetically coded, but on the micro level it isn't.  In fact there is nowhere near enough data capacity in our DNA to specify the interconnectivity.  Connections are made during experience-driven development with a high degree of randomness - no 2 persons (even identical twins) have their brains wired up even approximately identically.  Ratbone124.182.182.130 (talk) 03:07, 3 July 2012 (UTC)

Perfect, thanks for the answers. 65.92.7.168 (talk) 04:01, 4 July 2012 (UTC)

Salt water fuel
I read recently there was a man that used a certain type of radio wave, put it over salt water, and it combusted. He thinks that it is possible that one day this method could be used in the future. I realized one problem with it could be the fact that it takes more power to make the radio work than it produces, but what byproduct would this method of combustion make? 64.229.5.242 (talk) 21:29, 2 July 2012 (UTC)


 * Generally these schemes and scams are some sort of electrolysis or related process, which converts water into hydrogen and oxygen, which burn to give water. See Stanley Meyer's water fuel cell for one of the popular forms of this nonsense. DMacks (talk) 21:38, 2 July 2012 (UTC)


 * I would like to answer your question about how harmless the by-products are but it is a commercial secret. However, I can let you know privately if you invest in the development of this amazing high return –guaranteed!!!-- opportunity of a lifetime. You will miss the boat if you  waste time asking more questions – just send your money to me- then lay back  and dream about how  you will spend that fortune that awaits you.  --Aspro (talk) 21:42, 2 July 2012 (UTC)
 * What is the fax number, so I can send you the currency?Edison (talk) 14:19, 4 July 2012 (UTC)
 * If you're in North America, then try toll free number PATSY-1234. --Aspro (talk) 16:14, 6 July 2012 (UTC)
 * And you're right that you'd need to put more energy in than you get out. An exception is using substances which already have a lot of chemical potential energy.  Such substances tend to be flammable and/or explosive or at least give off heat spontaneously.  Salt water doesn't. StuRat (talk) 21:44, 2 July 2012 (UTC)

This one specifically is the invention of John Kanzius. It has been discussed previously on the science desk, here and here. Basically, what you saw is real. Passing radio waves through saltwater at the appropriate frequencies does liberate a flammable gas, which combusts spontaneously during the experiment. But you are also correct that this is absolutely not a way to generate energy. When the combustion occurs, all you will have done is reconstitute what was originally in the salt water, and so you could not have released any net energy from the water. A use might still be found for it, but it certainly won't be energy production. Someguy1221 (talk) 21:50, 2 July 2012 (UTC)


 * That mysterious gas is just hydrogen, no? Evanh2008 (talk 22:27, 2 July 2012 (UTC)


 * And some pure oxygen, presumably, which makes it burn better than hydrogen in air. StuRat (talk) 22:33, 2 July 2012 (UTC)


 * If you're electrolysing salt water, though, aren't you going to be getting chlorine and unpleasant sodium-oxygen-hydrogen compounds in the place of oxygen? Evanh2008 (talk 22:39, 2 July 2012 (UTC)


 * I'm assuming that the salt merely acts as a catalyst for the hydrolysis of water, and does not itself react. StuRat (talk) 22:44, 2 July 2012 (UTC)