Wikipedia:Reference desk/Archives/Science/2010 July 9

= July 9 =

Human flight to mars or venus
What's the shortest time it would take a spaceship carrying astronauts to reach Mars or Venus, assuming both of those planets were at their maximum distance from Earth? Are there any propulsion systems in development that could speed up the journey? And no need to question why they would be going to Venus, I'd just like to know the travel time. Thanks in advance!--92.251.187.65 (talk) 00:01, 9 July 2010 (UTC)
 * There is no shortest time, except the time it would take light to make the trip. You can always shorten the time by expending more energy.  There is a lowest-energy trip -- would that help you?  (And why in the world would you assume the planets are at their maximum distance?) Looie496 (talk) 00:56, 9 July 2010 (UTC)
 * At maximum distance for Mars means 400 million km "as the crow flies". That's ignoring having to avoid the sun, while at its closest it's only 55 million km. Apollo 11 reached a max speed of around 800m/s. Not sure how much faster an interplanetary craft could go. Voyager is going at about 16km/s, so i imagine somewhere between those two values, but probably closer to the lower end. Vespine (talk) 01:12, 9 July 2010 (UTC)
 * Only 800 m/s? Man, that's slow for a spaceship -- even some airplanes can go faster than this! 67.170.215.166 (talk) 03:10, 9 July 2010 (UTC)
 * 800 m/s is wrong. Apollo 13 (which was the fastest of the Apollo missions) topped out at around 40,000 kph, which is around 11,000 m/s.  The others were slower, but by a factor of ~10% or less. &mdash; Lomn 14:24, 9 July 2010 (UTC)
 * Sorry yes, ignore 800m/s, i can't find where I sourced that from, but it's very wrong, so much more a realistic guess is between 11 and 16 km/s... Vespine (talk) 22:49, 12 July 2010 (UTC)
 * It depends. It sounds like the OP is meaning humans and a trip starting from rest relative to earth. Unless we find some way to counteract the effect of acceleration on the human body inside the space ship and this seems a rather difficult thing to do, you're going to have limited acceleration so particularly for a short trip like from earth to Mars/Venus the speed of light isn't really the limit for human spaceflight since even with unlimited energy and a wondership you still need to accelerate/decelerate and you need to do it slow enough that you don't kill the human inside (and of course you can never reach the speed of light anyway even if you used 10^10^10^10^10^10G acceleration). For such a short trip, the acceleration/deceleration is really the limit. While admitedly the OP just said to reach Mars/Venus so you could argue there's no need for deceleration, I suspect the OP want's to actually stop on or near Mars/Venus rather then either slam into them of fly past at a high velocity so I'm presuming we do need deceleration. It's common to assume a 1G acceleration in these sort of wondership scenarios usually on trips to stars although humans could likely survive higher even on such long trips. You can use this  (or plenty of other calculators) to help with calculations based on a 1G acceleration. Liquid breathing suggests a potentially practical method for 15-20G perhaps higher so if you want to be generous perhaps take 20G. Of course practically we can't even manage close to 1G constant acceleration and there are so many technical challenges to achieving that that it's a moot point. Nil Einne (talk) 05:55, 9 July 2010 (UTC)


 * It's worth noting that nobody's planning to make a worst-case trip from Earth to Venus, Mars, or anywhere for the foreseeable future. Instead, we'd use Hohmann transfer orbits, which are achievably fuel-efficient.  Travel times vary depending on how long you want to stay at the destination -- anywhere from three to ten months is a possible Earth-Mars transfer time.  Venus would be faster (and the launch windows more frequent), but as nobody is discussing a near-term manned mission to Venus, I'm not aware of literature on trip times.  However, JPL's site discusses the mechanics of interplanetary travel and includes some commentary on possible future use of ion drives. &mdash; Lomn 01:27, 9 July 2010 (UTC)
 * So basically only someone who works for Nasa could know how long a "worst-case" trip would take?--178.167.149.82 (talk) 13:43, 9 July 2010 (UTC)
 * Plenty of people could calculate how long it would take. The point is, no one in the industry cares about calculating it, because no one in the industry is going to plan a worst-case trip.  In all probability, with our current tech, a worst-case launch is simply not doable.  That's why we have launch windows for missions of all types. &mdash; Lomn 14:22, 9 July 2010 (UTC)
 * Hohmann transfer orbits are great for unmanned probes. Manned missions would probably use something quicker. They wouldn't do the trip while the planets were on opposite sides of the sun, though; that would be crazy. --Tango (talk) 21:10, 9 July 2010 (UTC)
 * Why would we want to fly to Mars when it's on the other side of the sun? This sounds like a bad idea.  142.104.215.119 (talk) 01:47, 12 July 2010 (UTC)
 * If you are using a Hohmann transfer, you might want to leave when Mars is on the far side of the sun so that it is at the closest point to earth at the same time as you get that far from earth. Googlemeister (talk) 13:57, 12 July 2010 (UTC)

Location of Navajo Sandstone
According to the introduction, Navajo Sandstone is a large formation of sandstone found in Utah, northern Arizona, and northwestern Colorado. No map is shown, and the statement isn't sourced. Is this really true, or is "northwestern" an error for "southwestern"? After all, the only portion of Colorado that borders Arizona is the southwestern corner. Nyttend (talk) 00:31, 9 July 2010 (UTC)


 * This USGS webpage gives the areal extent of the formation as northern Arizona, northwestern Colorado, Nevada and Utah, remember that later events can chop up an originally continuous distribution. I'll add the link to the article page. Mikenorton (talk) 08:45, 9 July 2010 (UTC)


 * There is no discontinuity. Almost the entire western border of Colorado is shared with Utah, where the bulk of the Navajo Sandstone lies. Looie496 (talk) 17:40, 9 July 2010 (UTC)

Self-inflating Ball
My dog has a rubber playground ball that he loves to chase around and chew on. One day, he bit a hole in the rubber and it deflated (Although, this didn't seem to bother him at all!). Strangely enough, over the next couple of hours while the ball was left alone, it began to re-inflate! This seems to happen every time that he squeezes the air out. Why does this occur? Perhaps there is some difference in the air pressure on the inside and outside of the ball? I'd appreciate any ideas as to what's going on! Thanks! Stripey the crab (talk) 00:46, 9 July 2010 (UTC)
 * Possible: The ball is a sponge - the air is squeeze out using force, the rubber holds its shape and wants to return to spherical, slow ingress of air prevents the sponge rapidly returning to its normal shape - it happens slowly.87.102.42.55 (talk) 00:56, 9 July 2010 (UTC)
 * It may be that the rubber's "natural" shape is the full ball shape. If you think about the deflated state, the surface of the ball is very folded, and the rubber may exert a force against that which overcomes gravity pulling the top in. Rckrone (talk) 01:56, 9 July 2010 (UTC)


 * Is it a hollow ball or a solid one?87.102.42.55 (talk) 02:05, 9 July 2010 (UTC)
 * How does a dog deflate a solid ball? Cuddlyable3 (talk) 10:07, 9 July 2010 (UTC)
 * The ball is completely hollow and made of a flat sheet of rubber. It's like a small kickball.  It has that distinctive crosshatching pattern of squares.  —Preceding unsigned comment added by Stripey the crab (talk • contribs) 12:48, 9 July 2010 (UTC)
 * By the ball being a fine sponge, which is solid, not hollow ;) --Chemicalinterest (talk) 10:41, 9 July 2010 (UTC)
 * It's not a sponge. If you completely empty any ball of air and leave it alone for a while, it will re-inflate to a certain extent although it will remain very soft. Probably because the rubber or leather can't retain a squashed shape.--178.167.144.225 (talk) 15:46, 9 July 2010 (UTC)
 * I bet it's the rubber that wants to go back to its original shape and has nothing to do with air. —Preceding unsigned comment added by 142.104.215.119 (talk) 01:45, 12 July 2010 (UTC)

Wind turbine blades
Wind turbine blades appear to be usually long and thin (in both other directions) - I was wondering what reasons there are why shorter, wider blades are never seen? Indeed Wind_turbine_design says :"For a given survivable wind speed, the mass of a turbine is approximately proportional to the cube of its blade-length. Wind power intercepted by the turbine is proportional to the square of its blade-length" - a shorter blade would seem to be easier to support and thus lighter for a given cross sectional area, as well as having a lower rotational inertia. Are aesthetics a consideration causing long thin blades?, or other factors I haven't considered? (ie I wondering about something more like File:HydroelectricTurbineRunner.png but made of lightweight composites instead of cast metal, and with the ability to vary the pitch, and not quite so stubby either..) 87.102.42.55 (talk) 02:42, 9 July 2010 (UTC)


 * The reason for long narrow blades is aerodynamics -- an airfoil with a high aspect ratio makes better use of the pressure difference between its two surfaces by minimizing the induced drag caused by vortices at the wingtip, therefore it's more efficient. Same reason why helicopters and autogyros use long narrow blades for their rotors.  (This, incidentally, is my last post here for a while, since I am boycotting Wikipedia because of its extreme left-wing, cosmopolitan, pro-Soviet, pro-Third World, and anti-American/anti-Israel bias.)  Clear skies to you, and farewell. 67.170.215.166 (talk) 03:19, 9 July 2010 (UTC)
 * This is off-topic - but in the interests of truth, I should point out that the previous poster has been blocked from editing Wikipedia for making abusive personal attacks on other editors. So this is not so much a 'moral standpoint' boycott as it is a 'shut out for breaking our rules' situation. SteveBaker (talk) 13:32, 9 July 2010 (UTC)
 * Looking over your edit history reveals a majority of posts -- technical/scientific in nature -- which were very valuable and constructive, and a minority of posts -- political in nature -- which were inflammatory or worse. I hope that some day you'll find some modus vivendi that allows you to continue the helpful posts and leave out the obvious political disagreement you have with many Wikipedians.  --Sean 16:30, 9 July 2010 (UTC)
 * We have a cosmopolitan bias? I thought the whole idea was to be accessible to the world, and not just you know, Americans. John Riemann Soong (talk) 16:13, 9 July 2010 (UTC)
 * (rewritten once) I didn't really understand how induced drag is less for longer blades - the article says it related to the angle of attack, which makes sense. Yet it will also be proportional to the speed of the moving object.Mmmh but induced drag just pushes the blades back, not like an airplane where it affects flight..I'm guessing that induced drag due to reactive forces is not a big issue for a stationary object (excluding the strength of the support)
 * How does the drag due to wingtip vortices compare to the frictional drag? 87.102.42.55 (talk) 03:40, 9 July 2010 (UTC)


 * see Wingtip_vortices. as I understand it (which may be badly) drag-inducing wingtip vortices only affect the end of the lift-generating surface, so a long, thin blade produces - proportionally - a lot of unaffected lift area with respect to drag area.  but then, I'm just a left-wing, cosmopolitan, anti-American liberal, so what do I know?    -- Ludwigs 2  04:26, 9 July 2010 (UTC)
 * I don't see why they would be only at the tip - I get the explanation of them reducing lift (by air flowing back to increase the top surface wing pressure) - but why not all along the trailing edge ?? I don't get the airspeed explanation for why the trailing edge doesn't have the same effect - isn't the airspeed similar at the tip. I did understand the bit about shorter chords being better. (Maybe wingtip vortices are a red-herring?). I'll think about the chord effect.87.102.42.55 (talk) 04:52, 9 July 2010 (UTC)


 * I'll say this and hopefully find an online source later - a couple physicists and engineers at my university were very interested in a slow-rotating wide-short-blade wind turbine concept - one of the key selling points, apparently, was its inability to kill birds. They must have run into some subtle technical problems along the way - bad lubrication, poor wind deflection, etc - that killed the concept, though I'll have to double-check. SamuelRiv (talk) 09:57, 9 July 2010 (UTC)

If 3 blades is good, would not more blades be better? Cuddlyable3 (talk) 10:05, 9 July 2010 (UTC)
 * Not necessarily. Adding a fourth blade will increase the weight of the turbine, which means it is harder to keep it spinning.  Now this would probably be overcome by the additional force of another blade (though your tower now needs to be stronger from the additional force), but then you also have a higher cost to buy the additional blade, and the added complexity of the system (one more thing to possibly break).  I would be utterly shocked if the company that produces these turbines did not do some kind of cost/benefit analysis and optimization on these turbines and found that the additional power a fourth blade would add did not overcome the added costs and complexities.  Googlemeister (talk) 13:16, 9 July 2010 (UTC)
 * Three blades keep the wind pressure more evenly distributed. Note that normally, the wind speed increases with altitude. In a four-blade rotor, you always have the same surface distribution above and below the point of rotation. Hence there always is a stronger push on the upper half of the rotor than on the lower (surface is the same, but average wind speed is higher). This creates a torque that has to be borne by the bearings, something that is, apparently, very undesirable. With the configuration of a three-bladed rotor, the effect is less pronounced. In the Y configuration (two blades up), there is a larger surface area above the axis, but the blades are less high, and the lever is much smaller. In the inverted-Y configuration, the longer lever on the upper blade and the higher reach balances the larger area below. As a result, there is less torque, and the rotor runs more evenly. --Stephan Schulz (talk) 13:34, 9 July 2010 (UTC)


 * Vertical wind speed gradient loads the bearings with near-constant torque with a 4-blade rotor or a torque that oscillates at 3x the spin rate with a 3-blade rotor. If I were a bearing I'd prefer the 4-blade rotor. Cuddlyable3 (talk) 19:30, 9 July 2010 (UTC)
 * I can't even imagine being a bearing ;-). But as I understand it (i.e. not very well), it's the magnitude of the torque that matters, not the frequency. --Stephan Schulz (talk) 20:02, 9 July 2010 (UTC)

In aircraft wing terms, lift is proportional to area. A windmill blade is just a sideways wing. For a given weight of rotor, you can have a fixed amount of area and choose to have more or fewer blades, wider or narrower blades - but the total area-to-weight ratio is pretty much a constant. So why longer/thinner blades? Well, that tip-vortex thing is the main issue. If you think about an airplane wing (because it's easier) you know that the air pressure under the wing is higher than on top - that's what keeps the plane in the air. But at the tip of the wing, there is nothing to stop the high pressure air underneath from sneaking up around the wingtip and into the low pressure region on top. This 'wastes' lift by lowering the pressure beneath and increasing it above - and the swirling motion caused by that air sneaking around where it's not wanted causes a spiral motion to get started in the air that swirls out behind the wingtip as a vortex. Making that air swirl around takes energy that's clearly being lost from someplace and therefore wasted. Having a narrow tip cuts down on that effect. Hence, a long, narrow 'wing' or 'blade' is more efficient. However, in aircraft, there are other trade-offs with stability, controllability, etc that mitigate that effect. Jet fighters that need to turn on a dime with high g-forces can't have long thin wings because they'd snap off! But in things like the U2 'spy plane', gliders ('sailplanes') and helicopters - and also windmills, the benefits are all in the direction of long-and-thin and against short-and-fat.

You could have more blades - but more blades means more 'tips' and that's functionally just like having fatter blades - for a given weight and the same total area - four blades have more 'tip width' than three. You could go down to two blades - but (I'm told) that causes problems with vibration and wears out the bearings on the windmill faster than three. Also, there is a point with long-thin blades where the height of the tower needed to keep the blades above ground level becomes a problem. If you go from three blades to two - and keep the same total blade area and the same blade width, you'd need a 50% taller tower - which is structurally difficult and costly. Having said that, I have seen two-bladed windmills - so this isn't such a cut-and-dried choice.

In the end, all engineering is about compromise - and it seems that three blades is the best compromise in this situation.

SteveBaker (talk) 13:48, 9 July 2010 (UTC)


 * Just to highlight the main point in what Steve said - it's the sideways slippage of air around the tip of the airfoil (not the direct slippage of air under the edge of the airfoil) that causes problems. -- Ludwigs 2  17:24, 9 July 2010 (UTC)

veneer
do they use formaldehyde resin or contact cement to glue the Wood veneer on a a particle board or MDF desk? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 02:44, 9 July 2010 (UTC)
 * A similar question came up before Reference_desk/Archives/Science/2010_May_20 - I'm sure it depends on whether it's a wood veneer or a plastic effect wood veneer.
 * For a real wood veneer this site recommends the same things you would use to glue wood to wood I'm not sure if this applys to commercially produced wood on MDF veneers.87.102.42.55 (talk) 02:57, 9 July 2010 (UTC)


 * This product http://www.titebond.com/ProductLineTB.asp?prodcat=4&prodline=19 is a PVA glue, this seems the most common, though I can also find references to people using epoxy, and urea/formaldehyde resins, as well as hot melt adhesives.87.102.42.55 (talk) 03:06, 9 July 2010 (UTC)


 * There are also real wood veneers produced with the glue already attatched, not sure what sort of glue they use for these.87.102.42.55 (talk) 03:09, 9 July 2010 (UTC)

its a real wood veneer on a mdf desk by Ashley furniture. im just curious how its attached. —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 03:17, 9 July 2010 (UTC)
 * Could you contact them and ask http://www.ashleyfurniture.com/ I'm sure they won't mind answering a customer's question. There's a contact link at the bottom of their home page. (Normally for home-diy I'd guess PVA, but for a commercial product it's also likely that they use a heat bonded glue) 87.102.42.55 (talk) 03:44, 9 July 2010 (UTC)

whats a heat bonded glue? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 04:02, 9 July 2010 (UTC)
 * Like the glue they use in Glue guns - it melts and becomes sticky. For small scale verneers there's an example here of using it with a household iron http://www.joewoodworker.com/veneering/iron-on-veneering.htm . This is the stuff they might buy for factory use http://www.bostik-amer.com/products/ardal-t7631 it's just Ethylene-vinyl acetate also known as EVA glue. 87.102.42.55 (talk) 04:09, 9 July 2010 (UTC)

so they dont use formaldehyde resin ? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 04:25, 9 July 2010 (UTC)


 * I don't think there is a single answer. Certainly you can stick plastic laminates to particle board using a Contact adhesive (our article calls out exactly that as an application).  Contact adhesive is basically just natural or synthetic rubber dissolved into some kind of solvent - it's not a formaldehyde resin.  On the other hand, we know that there was a big kerfuffle about the trailers that FEMA supplied to the victims of hurricane Katerina that had used formaldehyde resin for this job - and that subsequent outgassing from the counter tops produced dangerous levels of formaldehyde inside the confined spaces of the trailers.  Hence, there must be multiple different adhesive technologies used by the furniture and kitchen cabinet industries in different applications.  Which particular technology is used where is clearly an important matter.  If you are doing this yourself, then you should probably use contact adhesive in a well-ventilated area where there are no sources of ignition (both of those things are really important for contact adhesives - especially when you're using it in huge quantities to stick large areas of veneer/laminate).  Be sure to follow the instructions carefully - contact adhesive has to be applied correctly and left to dry for a while BEFORE you bring the two surfaces together.  Also, the stuff 'grabs' like crazy - so you have to align the two surfaces perfectly the first time you bring them together - there is no 'wiggle room' once they are in contact.  For real wood veneers - use any kind of 'white' wood glue. SteveBaker (talk) 13:25, 9 July 2010 (UTC)

Dehydrated vs. freeze-dried
What is the difference between dehydrated food and freeze-dried? Is there a different process? —Preceding unsigned comment added by 71.137.244.115 (talk) 04:57, 9 July 2010 (UTC)
 * Wouldn't dehydration be anything that dehydrates or dries the food (like in the sun, hot air, freeze drying, whatever), but Freeze-drying be the specific process that requires freezing (well be the specific process outlined in the article)? Nil Einne (talk) 06:22, 9 July 2010 (UTC)

Immiscible liquids
Suppose you have two immiscible liquids in a beaker, with boiling points separated by 20 degrees or so. Obviously, one is going to float on top of the other. If you gradually heat the beaker and its contents, a book I have claims that at a temperature lower than both boiling points, the mixture will start to boil from the interface. The reasoning is that both liquids would contribute to the vapor pressure of a bubble nucleated on the interface, so that's where the first boiling would occur. The book also claims that this boiling from the interface would occur until one of the liquids is gone, at which point the temperature starts to rise until the other liquid's boiling point is reached.

Is any of this true? I've never observed boiling from an interface before. --99.237.234.104 (talk) 08:24, 9 July 2010 (UTC)
 * Liquids being immiscible does not mean that their mixed vapours do not have a common pressure. A bubble at the interface will have the higher of the two liquids' vapour pressures. That prevents the other liquid supplying any vapour to the bubble. Cuddlyable3 (talk) 09:54, 9 July 2010 (UTC)
 * It's not only true, but it also has important practical applications: see our article on steam distillation. Physchim62 (talk) 10:16, 9 July 2010 (UTC)
 * Cuddlyable3 got it wrong. Cuddlyable3 (talk) 11:25, 9 July 2010 (UTC)
 * Steam distillation involves two WELL-AGITATED immiscible liquids. So well agitated that both liquids are roughly evenly distributed.  I'm asking about the exact opposite: the case where one fluid floats on top of the other, with no intermixing at all.  --99.237.234.104 (talk) 01:31, 10 July 2010 (UTC)

Magnetism
Two long parallel current carrying wires attract each other.Currents are in same direction.Due to magnetic force,they will come towards each other which will increase their kinetic energy.Does that mean magnetic force carry out a work as change in kinetic energy is equal to total work done? —Preceding unsigned comment added by Shreshtha Vibhu (talk • contribs) 09:29, 9 July 2010 (UTC)


 * Yes. Force multiplied by distance (over which force is applied) equals work. Someguy1221 (talk) 09:37, 9 July 2010 (UTC)
 * If the currents are in superconducting wires (so we can ignore resistance) where does the energy to do the work come from? Cuddlyable3 (talk) 09:57, 9 July 2010 (UTC)
 * If you actually use the system to do work (that is, you let one of the current-carrying wires move), you will generate an electromotive force in the other wire which opposes the movement: this is Lenz's law. So, to keep the current flowing, you have to counteract that electromotive force from whatever power source you are using. Physchim62 (talk) 10:14, 9 July 2010 (UTC)
 * The wires are superconducting loops that maintain a current with no external source. Will any two such loops if allowed to approach one another lose all their currents? Cuddlyable3 (talk) 10:50, 9 July 2010 (UTC)
 * Not all their currents, but presumably the motion will induce currents in the opposite direction, in effect reducing the original currents. How does one calculate the energy stored in a superconducting loop?    D b f i r s   16:38, 9 July 2010 (UTC)
 * WHAAOE: Superconducting magnetic energy storage  -- Coneslayer (talk) 16:50, 9 July 2010 (UTC)  ... ... Thanks.   D b f i r s   10:01, 10 July 2010 (UTC)
 * The article doesn't explain what happens when two superconducting coils with current I in each attract and are allowed to approach each other until they become one coil. What is the current in that coil? Cuddlyable3 (talk) 19:17, 9 July 2010 (UTC)
 * As they approach they loose energy, and when you pull them apart (which will take effort AKA energy) you generate electricity inside them. Although it's not totally reversible, since as they loose energy the magnetic force goes down, so it's easier to pull them apart the second time. Ariel. (talk) 23:33, 9 July 2010 (UTC)


 * Nonsense. As you described, that would be a reversible process. Dauto (talk) 00:53, 10 July 2010 (UTC)

Cyanide death
Hi, This is to resolve a bet with a friend..does poisoning by cyanide consumption lead to a quick and painless death? —Preceding unsigned comment added by 122.160.164.64 (talk) 11:23, 9 July 2010 (UTC)
 * Please read Cyanide poisoning. --Chemicalinterest (talk) 11:28, 9 July 2010 (UTC)
 * (ec)I tidied the layout of your question and hope you don't mind. The Cyanide poisoning article describes symptoms of non-fatal cyanide intake. Fatal intake quickly induces coma and is a popular method of suicide, suitable for the whole family. Please do not encourage your friend to try this at home. Cuddlyable3 (talk) 11:40, 9 July 2010 (UTC)
 * Not the editing other people's comments again; another 3-page discussion on WT:RD. (Rolls eyes). --Chemicalinterest (talk) 11:46, 9 July 2010 (UTC)
 * It's OK. Cuddlyable3 only removed leading spaces. It's OK to fix formatting errors that disrupt the flow of the page - and having the question displayed as 'preformatted' text made it disappear off the right side of the page. The prohibition is only against changing the actual text. No debate required this time. SteveBaker (talk) 13:10, 9 July 2010 (UTC)
 * I took the time to individually delete every letter in the comment preceding this one (by SteveBaker), and put them in one by one. Clearly not a single letter is the same one as that deleted, but merely another one of the same value.  Am I within bounds or outside of it for having done this action? 84.153.202.156 (talk) 14:50, 9 July 2010 (UTC)


 * How are we to know if you really did that since apparently nothing has changed? hydnjo (talk) 17:31, 9 July 2010 (UTC)
 * It's the old Comment of Theseus paradox. -- Coneslayer (talk) 17:46, 9 July 2010 (UTC)


 * DID NOT! --Chemicalinterest (talk) 17:43, 9 July 2010 (UTC)


 * Ain't a paradox, just check Special:Contributions/84.153.202.156! There is no record of doing that. --Chemicalinterest (talk) 19:16, 9 July 2010 (UTC)


 * The answer appears to be that it is quick (a matter of minutes) and perhaps slightly uncomfortable (at low doses you feel cold and short of breath before you lose consciousness; I don't know how much overlap there is between experiencing these feelings and the dose being fatal). 81.131.27.38 (talk) 20:12, 9 July 2010 (UTC)
 * Perhaps it depends what you mean by "consumption". By all accounts the victims of gas chambers did not die either quickly or painlessly. AndrewWTaylor (talk) 20:25, 9 July 2010 (UTC)


 * Cyanide poisoning isn't always effective, either. See Kim Hyon Hui. ~ A H  1 (TCU) 14:46, 10 July 2010 (UTC)

Zucchini
What is that awefully sticky substance on a freshly peeled zucchini and does it exist on any other produce that I'm just not aware of or can't think of right now?  DRosenbach  ( Talk 11:34, 9 July 2010 (UTC)
 * I've never heard of anyone peeling a courgette before - it must be almost as rare as peeling a grape. 92.24.181.157 (talk) 12:37, 9 July 2010 (UTC)
 * I don't think peeling them is that uncommon in the US, particularly in larger specimens which can develop a thick skin. (Heck, maybe our zucchini are thicker-skinned than your courgettes owing to differences in climate or varieties planted.)  -- Coneslayer (talk) 12:42, 9 July 2010 (UTC)
 * Now that I think about it I never remember peeling a zucchini in all the years we grew and ate them from our family garden (in the USA)... It's almost always cooked, being not as tasty when raw as it's cousin the cucumber. --144.191.148.3 (talk) 15:24, 9 July 2010 (UTC)
 * You don't mean on the peel itself, do you? Because they often put food-grade wax on the peel to prevent dehydration and it can be quite sticky. --Sean 16:16, 9 July 2010 (UTC)
 * I think you're talking about zucchini sap aren't you. When most vegetables are peeled there is a slight oozing of juice, and the zucchini sap is a bit thick and adhesive. It will do you no harm. 86.4.183.90 (talk) 17:04, 9 July 2010 (UTC)
 * Sticky? I've always found that peeled zucchini are very slippery: I peel zucchini, sweet potatoes, potatoes, carrots, apples, and rutabaga with various degrees of frequency, but only zucchini slip out of my hands while I'm holding them partially peeled.&mdash;msh210 &#x2120; 18:09, 9 July 2010 (UTC)

Well, yes -- at first zucchinis are very slippery, but if you leave the film on your fingers it becomes very sticky after a minute or so (very astute of you, by the way!).  DRosenbach  ( Talk 03:22, 11 July 2010 (UTC)

homosexuality
G'morning, everyone. I read somewhere that Homosexuality is an inherited (i.e., genetic) trait. How is this possible? Wouldn't it have been eliminated from the gene pool (for obvious reasons) and then we would have no more homosexuals if this were the case? But there is a large LGBT minority in the world. 76.199.146.154 (talk) 16:23, 9 July 2010 (UTC)


 * Some people believe that homosexuality is 100% inherited. Some people believe that it is 100% a learned behavior.  I believe that most people believe that some is inherited and some is learned. --  k a i n a w &trade; 16:32, 9 July 2010 (UTC)


 * See Biology and sexual orientation, particularly at Biology_and_sexual_orientation, for different theories. ---Sluzzelin talk  16:38, 9 July 2010 (UTC)


 * BTW, even if homosexuality were a simple Mendelian trait where people with the recessive phenotype were 100% homosexual and the others were 100% heterosexual, that wouldn't mean the homosexual population would die out. You could have heterosexual "carriers" for the homosexuality allele who would reproduce and propagate it, sometimes resulting in offspring with the homosexual phenotype.  -- Coneslayer (talk) 16:44, 9 July 2010 (UTC)


 * And this is particularly true if the same gene that was recessive for homosexuality also produced another, reproduction-favorable trait (for example, good looks) and was dominant for that. Say if the gene for homosexuality is H and the allele for heterosexuality is h: then an HH individual is gay and probably won't reproduce, but an Hh (heterozygous) individual is attractive and not gay, and will have more children than average.  In real life this sort of effect has helped the gene for sickle-cell anemia to persist; the disease is detrimental but heterozygous individuals are more resistant to malaria than others, hence more likely (in some countries) to survive and have children.  --Anonymous, 16:51 UTC, July 9, 2010.
 * Related concept of some use: kin selection. Having, say, one male who works with the women exclusively (just to use a very crude and problematic example) could be of overall benefit to the survival of the family, so a gene pool that produced someone like that 10% of the time could be of benefit even if the person with that particular expression of the gene does not reproduce. --Mr.98 (talk) 22:16, 9 July 2010 (UTC)


 * Note that there are many genetic traits that either have no apparent survival advantage, or an apparent disadvantage, and yet they persist in the gene pool. --Sean 16:47, 9 July 2010 (UTC)

Being inherited is not the same thing as being genetic. Suppose a given trait is seen in people who have both of a pair of genes, A and B, and not in any other people. The trait is purely genetic, but since the two genes propagate independently, it is only inherited to a small degree. This isn't just a technical point, it's the key issue: even of scientists who believe that homosexuality has a genetic component, none of them believe that there is a single gene that is individually responsible for it. Looie496 (talk) 17:33, 9 July 2010 (UTC)

This entire thread assumes that gay people never have children, which simply isn't the case. Especially in older times or in countries that discriminated against gay people, maintaining a heterosexual lifestyle, had families etc just because that's what "society" expected 82.43.90.93 (talk) 17:38, 9 July 2010 (UTC)
 * I don't think any of us are assuming that gay people never have children in the real world. We're pointing out that even if the genetic basis for homosexuality were much simpler and stronger than it really is, the premise of the question (that it would die out) would not hold.  -- Coneslayer (talk) 17:49, 9 July 2010 (UTC)
 * It also assumes that just because a gene sequence is a dead-end (something that kills you or otherwise disables your reproductive system before you can reproduce) it would be quickly extinguished from the population; several genetic diseases would like to disagree with that thesis. In fact, that leads me to a question; is there a specific list of genetic diseases that are dead-end in this way? Things like Kleinfelters, Cystic Fibrosis, and Turners that severely inhibit reproduction come to mind. --144.191.148.3 (talk) 17:51, 9 July 2010 (UTC)

I read someplace that homosexuality was some the result of different devlopment in the womb?--92.251.220.50 (talk) 18:14, 9 July 2010 (UTC)
 * That's one of many hypotheses but it holds no more weight than any of the others. This debate is very much undecided and no 'cause' of homosexuality has been pinpointed. Regards, --— Cyclonenim | Chat 18:50, 9 July 2010 (UTC)


 * Also different hormone triggers, etc. Note that all those "in-the-womb" causes would be considered Nurture, as opposed to inherited causes, which are Nature, but not learned behavior. So in your original question, OP, you present what is called a false dichotomy - it is a wonderful illustration, because you are smart and everyone here is smart, but most of first posters seem to fall into this trap of arguing within the dichotomy. Sorry, just an interesting side note. Anyway, it just says that, as with blindness, left/right handedness, and certain allergies, there are "inherent" effects that aren't genetic (as with left-handedness, not necessarily bad effects). SamuelRiv (talk) 19:28, 9 July 2010 (UTC)


 * You can read about xenoestrogens at http://www.gobeyondorganic.com/Weekly-News-Tips/feminizing-of-america-part-i.html
 * and http://www.gobeyondorganic.com/Weekly-News-Tips/feminizing-of-america-part-ii.html. —Wavelength (talk) 23:03, 9 July 2010 (UTC)

The thing about evolutionary processes is that they don't require that (for example) no gay people ever have children in order to have that gene vanish from the gene pool given enough time. Consider animals like fish or amphibians that happen to fall into a cave system where there is no daylight. They always, without fail, lose their eyesight within a surprisingly small number of generations. You wouldn't think that there was any measurable advantage to being blind in such a system. But even the ever-so-slight benefit of needing slightly less nutrients to maintain those eyes and being slightly less vulnerable to injury and infection is enough to drive the entire population completely blind within perhaps a hundred generations. So it only takes a miniscule disadvantage to eliminate a gene in short order. So if there is a 'gay gene' (and I've seen no hard evidence of that), then it would have to confer some significant advantages to 'carriers' of the gene.

If this were a single gene (so no carriers - you either have the gene and are gay - or you don't) then consider what happens if even 80% of gay people overcame their sexual preference and had one child who inherits their gene. In the second generation, there would be only 0.8 times as many gays as in the first generation, then 0.8x0.8 in the third generation...and 0.8N in the N'th generation. Once 0.8N times the size of the original population gets anywhere close to 1 person - the gene will disappear completely with a 20% per-generation chance of vanishing. If you started out with a million gay people - the gene would die out within about 62 generations - just 1,200 years. If only 10% of gays had children, they'd be extinct in six generations - 120 years.

We're left with only a few possibilities:


 * 1) This is not (predominantly) a genetic condition.
 * 2) It's genetic but it's a really complicated consequence of a bunch of different genes - or maybe it's only switched on by some kind of environmental trigger (overpopulation, for example, might be a reasonable guess).
 * 3) This is like sickle cell disease: People only turn out gay if they have two copies of the gene and there is some significant benefit to people who only have one copy ('carriers').
 * 4) It's a simple single gene condition - but gay people produce surviving children at close to the same rate as straight people.

The last of these seems spectacularly unlikely - their rate of having children simply must be low enough that that 0.8N thing (or whatever the number is) would have comprehensively erased the gene within the last few thousand years. (3) also seems unlikely because we'd surely notice if both parents of gay people were resistant to some disease or otherwise more likely to have (non-gay) children. - so it's one of the first three...but separating 'nature from nurture' is very hard and it may be a long time before we know for sure. I'm not sure I believe (1) either - gay people come from a huge range of backgrounds and in all countries of the world. There just doesn't seem to be a common theme running through the population.

So that leaves us with (2)...it's complicated. A random combination of many genes with some other environmental triggers would be almost impossible to track down - particularly with the 'political correctness' issues surrounding the study of this behavioral pattern. I doubt we'll ever know the true causes of this...but I suspect we'll grow as a species to the point where we actually don't really care. Once we end the discrimination and social stigmas, there will be no need to 'cure' people or even particularly influence the way people behave...so who cares?

SteveBaker (talk) 03:01, 10 July 2010 (UTC)
 * First, the options in that list do not have to be disjoint. Secondly, you miss the kin selection part (unless you subsume it under #2). And thirdly, of course, hetero/homo does not seem to be a strict dichotomy, but rather a spectrum, and the need to identify oneself as either/or is very much cultural. For some cultures (like ancient Greece) it's completely normal to have a homosexual relationship for male bonding and raise a family. Being in a prestigious homosexual relationship may actually open up more chances of siring children. Consider the Sacred Band of Thebes - don't you think those young studs would get plenty of laid if they return victoriously from the battlefield, covered in manly sweat and extra virgin olive oil? --Stephan Schulz (talk) 07:02, 10 July 2010 (UTC)


 * What some consider the standard family now is quite rare on a historical scale. For most of human existence we have lived in extended family groups with all members contributing in some way to the care and raising of children. And human children require very long periods in that care situation. Gay family members would actually enhance the probability of children reaching reproductive age. HiLo48 (talk) 07:52, 10 July 2010 (UTC)
 * You make the simple assumption that male members of the community would be willing to provide that long-term care for the child and increase it's likelihood of reaching puberty. In historical times, men didn't have a caring role (or at least a very minimal one). Care was left to the mother whilst the father was hunter-gatherer. I thought I read somewhere that when children were motherless, they were probably adopted by another mother or left to survive (depending on the age, presumably). Regards, --— Cyclonenim | Chat 11:12, 10 July 2010 (UTC)
 * But those males who go hunting tend to do it in groups and share their spoils with the rest of the extended family. Still an advantage to the child. HiLo48 (talk) 03:40, 11 July 2010 (UTC)
 * Hardly, males have to leave the child alone to go hunting. How is that an advantage over having a mother to care for them whilst the males are away? That way the child gets protection AND food. Regards, --— Cyclonenim | Chat 10:24, 11 July 2010 (UTC)
 * I cannot see your point at all. Of course the men leave the children to go hunting. Most are seeking food for their own children. A homosexual does not have children of his own. His hunting spoils will be shared with children of others. That is a benefit those children have that would not be possible if the homosexual was not there. HiLo48 (talk) 11:24, 11 July 2010 (UTC)
 * Sorry I misunderstood you, but I still think your point is flawed. It's likely that the strongest males won over females and had children, and that the others were 'forced' to turn gay for their sexual fulfillment (one of the two key pleasures in prehistoric life, along with food). It seems unlikely that a) a homosexual then would be able to hunt with decent prowess compared to those who had won the females; and b) that those heterosexual males would allow the homosexual males to approach their families and give them food anyway. That could be seen as the homosexual male trying to work his way into a family, and I find it sincerely unlikely that being a homosexual would be an evolutionary advantage in this sense. It's hard for evolution to work indirectly as you described, i.e. with a homosexual helping children not their own. Evolution works to keep your own genetic line going, not those of others. Regards, --— Cyclonenim | Chat 12:30, 11 July 2010 (UTC)
 * You've completely lost me now. If you believe that (1) homosexuals choose to be that way, and (2) they are somehow a danger to other family members, especially children, and are to be naturally feared, then you have no hope of understanding this phenomenon. Homosexuals ARE part of a family. HiLo48 (talk) 20:18, 11 July 2010 (UTC)
 * What the hell are you talking about? Please quote where I said that homosexuals choose to be the way they are, and the part where I said they were a danger to other family members. With all due respect, learn to understand what I've said before criticising and patronising me! If you don't understand, ask for further clarification. It's very well known that prehistoric creatures, including humans, enjoyed sex and food as their main pleasures. It's quite logical to assume that stronger and more successful males drew female mates and just had heterosexual relationships. I'm not saying homosexuals choose to be the way they are, I'm saying homosexuality could have arisen from a lack of success. I, in no way, suggested that homosexuals are a danger to other family members and I find it offensive that you think I would think that! You're assuming (again, might I add) that homosexuals spent all their time around family members. Humans didn't just hang around in family groups; the groups consisted of several families. Ignore the homosexual part. If a single heterosexual male tried to provide for the children of another couple, that could be taken as trying to work his way into that male's family and it could result in tension and anger. So it makes no sense to assume homosexuals would go and provide for other families as an evolutionary benefit for those genetic lines. It just wouldn't work like that. Regards, --— Cyclonenim | Chat 21:20, 11 July 2010 (UTC)
 * Well, I don't know about HiLo, but I was pretty appalled by "the others were 'forced' to turn gay" and associated reasoning in your answer. Frankly, everyone else is talking about being gay (being more attracted to your own gender than the opposite gender, sexually), while you (for some reason) are talking about men having sex with other men because they can't get women. Which is completely different, and not at all subject to the same pressures and interactions. What possible relevance this is supposed to have to the original question, I don't know. For it to be relevant, you would have to intend it to have the (offensive) suggestion that being gay is something people choose because they want more sex! And then are 'naturally' rejected by families!
 * On a more general note, most people here have followed the typical pattern of evolutionary psychology in only considering the men! A lot of the 'theories' about the evolutionary value of being gay focus almost exclusively on the value of gay men. It is very rare to find someone discussing the evolutionary value of women being gay (or even bi). 86.164.57.20 (talk) 16:47, 12 July 2010 (UTC)
 * The "forced" was put in inverted commas for lack of a better word at the time. The very nature of this discussion is taboo, and I apologise if I'm coming across as a bigoted prick because that's not my intention--I'm very open minded around homosexuality and have many as friends. When we're talking about the origins of homosexuality (which is, after all, loosely what this question is about) then we have to discuss possibilities. I am not saying that in our modern times all homosexuals are screwing each other because they can't get women. That's clearly NOT what is happening now. What I am talking about is the possibility of, in prehistoric lives as early hominids, the origin being a result of lack of interaction with the other sex. It does make sense for those who are less aptly suited to hunting to be less likely to have a female mate, and it is very well known that sex is a fundamental pleasure that everyone seeks. If that causes you offense then I'm sorry, but it's just an opinion about the past. It doesn't have the slightest bearing on how I approach homosexuals now.
 * You do have a point with female homosexuality though, my above comments clearly would not apply in this sense so who knows. Regards, --— Cyclonenim | Chat 17:59, 12 July 2010 (UTC)
 * But what would that, unknowable, prehistoric behaviour have to do with homosexuality? The discussion is about inheriting a tendency to prefer the same sex to the opposite sex: how would a hypothetical situation in which men chose to have sex with other men because there were no women lead to an inherited tendency to prefer men to women (even if gay women didn't need to be explained in the same way)? (And while you put 'forced' in quotes, you did use the phrase 'turn gay' with no quotes or apparent irony, to describe men choosing to have sex with other men as a last resort, when they would rather have sex with women.) As it is, you are discussing an unknown, unknowable behaviour, in some vague prehistoric society, with no bearing on an inherited tendency to prefer ones own gender. 86.164.57.20 (talk) 22:12, 12 July 2010 (UTC)


 * See this article from LiveScience. What about environmental (hormone chemical pollution) factors? ~ A H  1 (TCU) 14:40, 10 July 2010 (UTC)


 * Homosexuality is slightly correlated to higher IQ. Most likely, some genes that promoted intelligence and creativity may have influenced sexual attraction pathways. Bear in mind, sex is not all about reproduction. Look at our bonobo cousins. Sex is used for social bonding. Thus, homosexuality starts to have some evolutionary fitness.John Riemann Soong (talk) 18:00, 10 July 2010 (UTC)


 * DANGER WILL ROBINSON! JRSoong, that assertion requires citation first, a definition of "slightly" second, and a thorough checking of sources to make sure the author isn't a eugenicist third, because that very much resembles the old "penis size vs brain size" trade-off line of the racial eugenicists. IQ correlation is a very problematic thing in general anyway, since IQ itself has a still-debatable heritability factor, and is a quantity defined exclusively on a correlation itself. SamuelRiv (talk) 19:17, 10 July 2010 (UTC)
 * it's a blog post, but it's basically interpreting data from the GSS. I haven't crunched the numbers myself but it seems to verify the anecdotal observation that homosexual people do tend to 'seem' smarter on average at least. (or at least among my schoolmates) John Riemann Soong (talk) 20:31, 10 July 2010 (UTC)
 * Yeah - that's a crazily 'iffy' assertion...even if it's true. Recall that correlation does not imply causation.  Even if there were a 'gay' gene, it might still be a developmental matter that would produce a higher IQ.  You can think of all sorts of reasons - to pick a silly one: maybe gay teens don't get invited to so many parties when they are in college - so they have fewer hangovers and study harder.  The other problem is the assertion that higher IQ results in a better probability of having children...and for 100% sure, that's not at all the case.  There is a strong NEGATIVE correlation between IQ and number of offspring...Idiocracy rules! SteveBaker (talk) 04:30, 11 July 2010 (UTC)
 * That is only a very modern phenomenon, and even then only true in some cultures. In low-tech cultures, the number of (surviving) children you have is usually a function of how well you can provide for them, and that may very well be linked to IQ (or at least intelligence - we know that IQ primarily measures the ability to do IQ tests...). --Stephan Schulz (talk) 08:22, 11 July 2010 (UTC)
 * ...and if that (and all of the other assumptions that go with it) were true - then homosexuality ought to be in steep decline because the one genetic advantage for 'carriers' (parents of gay people) would have been overtaken by societal change. I don't think that's the case - although with the general population having a (mostly) more accepting view of the gay community, more people are "coming out of the closet" than in the past - so any idea of the numbers involved would be tough to ascertain. SteveBaker (talk) 17:19, 11 July 2010 (UTC)


 * I'm not saying anything about causation, merely correlation and linkage disequilibrium. In any case I want to investigate this further using serious and rigorous genetic and genomic studies, but no profs at my school seem interested. The professors interested in sexuality and homosexuality somehow occupy anthropology, psychology, English Lit or sociology, etc. positions and the only sexuality studies going on in the biology and neuroscience department appear to be work on C. elegans, Drosophila and S. Latifolia roadside flowers. Why do the people at gay/gender studies stay away from the natural sciences?
 * Anyway anecdotally I shall say that people who are gay tend to be disproportionately intelligent/educated and fill leadership positions. And believe me, these people partayy. In fact, since being gay is correlated with being fly/flamboyant/cool, I say they party harder than the population average. John Riemann Soong (talk) 04:06, 12 July 2010 (UTC)


 * Someone who does not feel the urge to mate with someone with whom they can reproduce is going to be far less likely to pass on their genes, so if homosexuality was inherited it would be very rare by now due to natural selection, not at a few percent of the population. —Preceding unsigned comment added by 142.104.215.119 (talk) 01:43, 12 July 2010 (UTC)

Come on, let's actually think
The causes of homosexuality appear to me myriad and complex, which goes the same for sexual attraction and personality. Come on, let's actually THINK. Start with sexual attraction in general. "Straight" people must be:
 * (boy) attracted to girls, dissauded sexually from other boys
 * (girl) attracted to boys, dissauded sexually from other girls

Now I shall cautiously propose that girl-girl dissuasion is weaker than boy-boy dissuasion (on average) -- but maybe in Western or modern culture it's more acceptable for girls to make out with girls. Anyyyway, to even effect such a thing it's highly likely that the whole thing is effected by a host of various protein products if not genes. And sexual selection can often be arbitrary -- see things like sexy son hypothesis and handicap principle. The weirdest shit can become sexually attractive or sexually repulsive.

It seems quite likely that once in a while, that the biological machinery will "mess up". So you get people who are attracted to both sexes and repulsed by none (or maybe with attractive forces to both genders but repulsion still holds for one, making that person 30% gay or 70% gay, etc. as per the Kinsey spectrum) .... the combinations are myriad. Likely there are a whole host of attractive traits that can be independently assorted. Meanwhile, some attractive traits or genetic elements that create attraction or repulsion are linked or piggybacked to other traits.

It could be that some of homosexual attraction piggybacks on general promiscuity, which may not increase all types of attraction equally. I put forth the unrigourous observation that girls who go clubbing a lot are a lot likely to make out with other girls than the population average. Ooh surprise surprise, the more promiscuous you are, the more you procreate. Again, see the sexy son hypothesis. Counter-intuitively, things that appear to be against the fitness of the individual can promote it to a certain degree. Or else why would some females be attracted to unfaithful males?

Also, remember group selection. Human sexual evolution is COMPLICATED, especially when you toss social and cultural factors into it. John Riemann Soong (talk) 04:44, 12 July 2010 (UTC)

pheresis rate
Already checked:, pheresis, plateletpheresis.

Why do plateletpheresis machines (or at least the newer, electronic ones) go so much faster — that is, collect so many more platelets per minute — toward the end of a draw than toward the beginning? For example, I was on a machine today for 39 minutes, in which it collected 7.0 platelets (estimated), but in the first 28 minutes (72% of the time) it collected only 4.0 (57%) of the platelets — and the discrepancy was even worse earlier in the draw.&mdash;msh210 &#x2120; 18:02, 9 July 2010 (UTC)
 * This is quite simply a guess and I'll readily admit as such, so you're all welcome to shoot me down. Removing platelets will decrease blood viscosity and wouldn't that increase blood pressure? Increased blood pressure would lead to the blood traveling through the machine faster and more platelets would be removed in that time than earlier when your blood pressure was lower. Again, purely a guess. Regards, --— Cyclonenim | Chat 18:43, 9 July 2010 (UTC)
 * Actually, that makes no sense. Removing stuff from your blood would make it less viscous and thus slightly lower in pressure. I'm stumped. Regards, --— Cyclonenim | Chat 18:45, 9 July 2010 (UTC)
 * I believe that the platelet count displayed by the machine is a rough estimate. When I came back after donating platelets my first time, they told me that they had gotten more platelets than they expected, which, from the sound of it, they didn't even know until after some offline processing.  It's also possible that the machine was adjusting the rate for some reason.  Paul (Stansifer) 23:08, 11 July 2010 (UTC)


 * I agree with Paul Stansifer's reply - I know they always input an estimated platelet count before they begin a run, along with estimated blood volume, to estimate the rate of collection and total duration of collection. I don't know for certain whether this gets corrected during the procedure based on counting within the machine, but I don't think so - I think revisions are related to tolerated flow rates (draw and return).  I found this to be an interesting read on related topics (platelet collection, storage, etc) but it does not directly address the OP's question.  A possibility to seriously consider is that the collection rate is not really uniform, but rather multiphasic.  What I mean is that if you allow 10-15 minutes for low-yield priming of chambers, balancing of flow rates, etc prior to actual collection commencing, then the rate of collection would be a fairly uniform 2.7 x 1010 platelets per minute.  This is just speculation, but you might ask how long it takes for them to actually begin the collection in earnest.  -- Scray (talk) 03:29, 12 July 2010 (UTC)
 * I asked the nurses when I was there (not this time, but a previous time) why the process seems to speed up over its course, and none of them had an answer. Perhaps the replies given — that it's due to the correction of initial estimates, that it's due to an initial low collection rate due to other tasks the machine is doing, or both in combination — account for it. I'll keep an eye here for a while in case anyone has any further ideas. Thanks to those who've replied already.&mdash;msh210 &#x2120; 18:19, 12 July 2010 (UTC)

Best season for avoiding camel spiders?
I am considering a trip tp Jordan that includes a two day stay in the desert. However, I'm arachnofobic and absolutely terrified of camel spiders. Which would be the season during which I am least likely to come across one? —Preceding unsigned comment added by 213.10.229.86 (talk) 20:27, 9 July 2010 (UTC)

If you're worried because of things you've read about them online i'd highly recommend reading the article Solifugae. Contrary to popular belief they aren't as fast, large and dangerous as rumours suggest. That said as a fellow 'phobe' I can certainly see why they'd be a worry regardless! ny156uk (talk) 22:04, 9 July 2010 (UTC)

do people really believe their beliefs?
It seems to me that actual conclusions from religious beliefs, such as the idea that Jesus must have ridden dinosaurs, always come from scientists. In other words, I've never seen a religious person actually use what they believe in the way they use their personal experiences. So, my question is, do they even believe their beliefs in a literal sense? For example, I bet I could elicit a conclusion from a religious person about what must have happened during the nineteenth century, for example if two people they know lived in that time might have met, but I think it would be impossible for me to casually elicit a conclusion based on their religious "beliefs", I don't think they picture the things in the same way. In other words, I am saying that I think even the Pope does not think his beliefs actually happened, as he thinks of his beliefs about nineteenth century Europe. Am I right in this, a-hem, belief? 84.153.230.67 (talk) 20:47, 9 July 2010 (UTC)
 * I'm afraid your question doesn't make that much sense to me, and I'm not sure it's a particularly scientific question anyway. If you hold a certain belief, then you 'believe' that belief. The key is in the world itself. If you're asking whether religious people are deluded, that's a hard question to answer. Certainly some people would conclude that they are; others wouldn't. I'm fairly confident that the Pope does truly believe in Catholic/Christian principles and that it's not just some sort of cover story. Feel free to elaborate further if I haven't answered your question. Regards, --— Cyclonenim | Chat 20:56, 9 July 2010 (UTC)
 * I think some "believers" genuinely believe and others say they do more out of habit than anything. An example of evidence for that latter would be a Christian that has repented for all their sins yet fears death. If they genuinely believe they will go to heaven, there is no reason to fear death. There are plenty of examples of Christians fearing death (ask any hospital chaplain). The opposite is hard to prove - someone might not genuinely believe what they say they believe but might be a very good actor, so we can't find any definite examples of someone that genuinely believes. I'm confident they exist, though. --Tango (talk) 21:28, 9 July 2010 (UTC)
 * I don't think you can infer from a Christian's fear of death that he doesn't really believe in the afterlife. He may not be quite sure where he'll wind up.  Trying to figure out if you're really sorry for something you did, especially if you really enjoyed it, is pretty tough. --Trovatore (talk) 21:35, 9 July 2010 (UTC)
 * That and even people who are moving to a better house or job can still be a little anxious because they are leaving the known for a somewhat less familiar situation. Googlemeister (talk) 13:49, 12 July 2010 (UTC)

Fear may be a biological or psychological activity rather than an intellectual activity. Why should an atheist fear death any more or less than a religious person? Bo Jacoby (talk) 22:13, 9 July 2010 (UTC).
 * Are you asking if people believe in their religion in a literal sense or a figurative one? If that was the question, you'll find both.  Creationists believe that God created the world five or six thousand years ago in a very short period of time.  They, so far as I know, firmly believe that, and will not hear otherwise.  Other Christians believe that God created the world, but not such a literal interpretation.  You can find similar variances for a lot of scripture.  But with my particular beliefs (I am a member of a Christian denomination), my faith does not involve the Creationist theory; whether God created the world in 6 billion years or 5000 years is irrelevant.  I believe in the most widely accepted scientific explanations (chunks of rock got together and created a planet etc).  Absolute irrefutable proof of either would not change my belief one bit.  Therefore, I conclude that we all believe firmly in the things we believe, and even though other people with the same labels (i.e. other Christians or Jewish people etc) believe in other things, we really don't believe in anything that we don't believe in.  That is a confusing, but I think, the most accurate answer to the question. Falconus p  t   c 22:48, 9 July 2010 (UTC)


 * This is a really interesting question, and quite a difficult one. The classical concept of belief requires that if a person believes something, they must also believe everything that logically follows from it.  But it is quite obvious that real people don't work that way.  Philosophers and psychologists have struggled endlessly to find the right way to deal with this; the best way to get into the literature is to key on the concept of irrationality. Looie496 (talk) 23:24, 9 July 2010 (UTC)
 * One interesting angle are scientists who believe. 84.153, you might be interested in some of the references listed under studies of scientists' belief in God. ---Sluzzelin talk  23:34, 9 July 2010 (UTC)


 * You have to be a little careful about those studies. The problem is that if you are being strictly scientific about it, you cannot say: "God doesn't exist" because there is essentially no way to prove that - you have to say that "God might exist - but we can neither prove nor disprove it".  Similarly, even if you believe in God, you shouldn't say "God definitely exists" - because you can't prove it either.  Hence, taking things strictly, there should be no atheist scientists - we should all be agnostic no matter what we feel inside because the 'God hypothesis' is unfalsifiable.


 * That's why the numbers from these surveys are all over the map. The answer you're going to get depends sensitively on how you ask: If you ask something like "What is your gut feel about this whole "god" thing?" - you'll get a lot of atheists and a reasonable number of religious types - but relatively few agnostics.  But if you ask "Does God exist?" - then you should logically get almost all agnostics.  For myself, I always say I'm an atheist - even though, strictly speaking, I should be retaining some measure of doubt...that's because nobody ever asks me whether I also believe that pink piano-playing aardvarks live on the dark side of the moon - or whether the Tooth Fairy is real - because if we're speaking strictly - then I have to say that those are both rather more likely than God - so I'm also "Tooth Fairy-agnostic".  But religious people always seem much happier when you just say "agnostic" because they kinda think that you're 50/50 on the subject and could easily be pursuaded to become a full-time churchgoer if only they could give you a little encouragement.  When (like me), you're more like 99.99999999999999999999999% no-God/0.000000000000000000001% god then the term "agnostic" is a poor one because it doesn't have shades of meaning.  These days I say "atheist" because if we drew a line with 0% chance of god existing at one end of the line, 50% in the middle and 100% certain that he/she/it exists on the other end and label those three points 'atheist', 'agnostic' and 'believer' - then my personal position is so very close to the 0% point that it would be nuts to go with any other label.  Telling people that I believe that "God might exist" gives an entirely false impression of my position on the subject - so I'm forced to say "God doesn't exist" even though I can't prove it because that delivers a much more accurate impression of my degree of doubt to laypersons.


 * So when you consider a bunch of scientists making these kinds of determination about how to express our true understandings, it's not surprising that these surveys are all over the chart. SteveBaker (talk) 04:28, 10 July 2010 (UTC)


 * So basically you're a strong agnostic atheist? Regards, --— Cyclonenim | Chat 11:22, 10 July 2010 (UTC)
 * I have similar views and describe myself as a weak atheist. It's not particularly precise, but it is accurate and it's good to keep things simple. I usually explain it by analogy: I believe there could be a god in the same way that I believe that when I drop something it might not fall and just levitate. (Dawkins gives a similar analogy with fairies at the bottom of the garden rather than levitation, but I prefer mine since his is more of a restatement of the god question than an analogy - of course his views on gods and fairies are the same, there isn't really a difference between gods and fairies, they are both supernatural entities.) --Tango (talk) 11:53, 10 July 2010 (UTC)


 * Yep - hence "Tooth-Fairy agnostic". But 'weak' doesn't really cover it either.  There are an infinity of possible things that might be true but which are unfalsifiable.  God is one of those infinite possibilities.  Thus far, not one of those crazy things has proven to be true - so the 'probability' that I assign to God being true is roughly the same as the probability that any one of those other things are true.  Although it has to be said that the probability of the Tooth fairy being true seems somewhat higher than God because there are severe logical and thermodynamical problems with a being that can do literally anything and which has no origin.  The Tooth fairy could possibly be a naturally evolved flying creature with human appearance who has some biological drive to collect human teeth - this doesn't break any laws of physics, biology, logic.  But with an infinite number of seemingly impossible things that one might possibly believe in - it seems odd that you'd pick the one that's least possible!  So God-atheist, Tooth Fairy-agnostic describes my position most accurately. SteveBaker (talk) 15:21, 10 July 2010 (UTC)

It's unclear why you find the 19th century significant. The last person who remembered the last of the years 1800 to 1900 died a few years ago but thousands of us have had friends or parents that told of those times. There was photography, sound recording and you can see some of the people on film. Nobody that I know of believes that Jesus rode on a dinosaur. Typical Christian teaching is that Jesus was spiritually active in the creation of everything but did not appear as a human until long after all the dinosaurs were dead, and therefore Jesus had to ride on a donkey. It's not practical to test how strongly people believe what they say they believe, but if you read the article Religion you may notice peoples' different religions depend largely on where they grew up i.e. what their parents believed. That suggests that a belief in a religion (or no religion) is a psychological state that is hard to change. Cuddlyable3 (talk) 23:33, 9 July 2010 (UTC)


 * It's certainly surprising that people who profess to believe in any serious kind of god would even consider breaking his/her/it's rules. However, the bible is the most shoplifted book in the world (and for sure, it's the most shoplifted in the deep bible-belt city of Austin Texas where I happen to live.  I suppose it's possible that people have to steal the book in order to discover that pesky little "Thou shalt not steal" clause - but I really don't think so.  The jails in the US are full of deeply religious murderers, car thieves and so forth - the rate of religious belief amongst criminals is much higher than in the general population!  But if you truly, deeply believe that you're going to suffer a literal infinity of time spent in the most unbearable pain imaginable rather than an equally infinite amount of time in the most pleasurable place imaginable - why on earth would you even consider breaking the slightest one of those 10 simple rules?  It is truly incredible that in the deepest bible-belt US states, we have the highest tolerance for the death penalty.  Whatever happened to being required to forgive people?  It is indeed hard to believe that any self-proclaimed religious people actually believe at their core what's being told to them...because in 99% of cases, their behavior certainly doesn't mirror their belief systems.   SteveBaker (talk) 01:55, 10 July 2010 (UTC)


 * You got that wrong there. People believe that they will go to hell (the place of torment) if they do not accept God's cover (salvation) for the sins they have committed. Religious people can steal just as much, or more (the Inquisition confiscating estates of people they condemned) than a nonbeliever. Major laws in the US were based on the Bible. Like "Murdering is wrong and should be punished". If the Bible is disregarded, then all laws have only the basis of tradition, a weak barrier that can be crashed any time (example the Third Reich). Many religious people do not make an effort to please God; they just sin, get pardoned, sin, get pardoned, sin, get pardoned... like eating junk food and getting heartburn, taking antacids, eating junk food again and getting heartburn, taking antacids... That is not God's plan.


 * If you don't support the death penalty, why do you support the "death penalty" of the people who were killed in the crime? The death penalty is based on the Bible, and the only reasons it is still instated is a belief in the Bible or its laws, or tradition. The Muslims who hijacked planes on 9-11 were deeply religious, dying for their cause. It is hard work to become a perfect Christian; it does not come automatically. Most just slip back into their old ways, or they believe that they can buy pardon every time they commit a sin.


 * About the dinosaur thing. Jesus might have or might not have rode on a dinosaur; all I know is that it is not notable enough to be included in the Bible.


 * Conclusion: People have been given the freedom of choice by God. They can choose to believe in a god, remain neutral, or not believe in a god regardless of the evidence. --Chemicalinterest (talk) 11:08, 10 July 2010 (UTC)
 * No, Jesus did not ride a dinosaur. Dinosaurs were extinct, and it isn't mentioned. The two go pretty well together, and people who say otherwise have absolutely no reason to believe he really did. Regards, --— Cyclonenim | Chat 11:15, 10 July 2010 (UTC) That is... in my opinion ;) Regards, --— Cyclonenim


 * I'm not sure why we're looking at it solely as a religious question. Look: "beliefs" exist for everything. What did primitive man look like, tens of thousands of years ago? You can conjure up an image. You see it quite clearly and you find it quite compelling. You can imagine what it would look like to walk around in Roman times. You can imagine what the Pyramids must have looked like under construction. You have a whole intricate vision in your head of things you yourself have really very little good knowledge of, and you believe that things happened in a certain way. When someone comes to you and says, "Oh, here is a new and surprising fact about the past!" you say, "huh," and, if you find it compelling (and the source reliable), you integrate it into that belief system of yours. Now whether the "beliefs" held by archaeologists and historians are better founded than those produced by theologians or preachers is a different question (and a good one, to be sure). But the underlying structure of how it works in our heads is probably the same; the difference is how we come up with new beliefs in the first place, what lines of evidence and logic we find permissible, etc. I believe Julius Caesar existed (and have what I consider pretty good reasons to believe this); I believe that Attila the Hun existed; I believe that humans are descended from odd ape-men like Lucy and so on. Just because these beliefs are validated by current archaeologists, historians, and scientists doesn't change the fundamental mental structures that I use to make sense of them, as compared with someone who believes in the miracles of Jesus, or the bizzaro-world Creationist vision of things. If you have a hard time taking seriously the idea that other people may indeed sincerely believe things that you do not believe, I suspect you need to travel a bit more—the world in which you, yourself, live as an individual is unspeakably small when compared against the world as a whole, and what seems perfectly straightforward and "obvious" to someone who lives in one place is totally arbitrary and mysterious to those who live elsewhere. --Mr.98 (talk) 12:18, 10 July 2010 (UTC)


 * This question actually gets to the heart of a source of much misunderstanding. People with a belief in God, with 'faith' in God, absolutely feel that God is there. It is a feeling, like loving someone or grief, which seems like an intrinsic part of the world and being human. It can be difficult for people who feel this, particularly if they've felt it as long as they can remember, to really believe that other people don't feel it. That's where you get all the strange 'atheists are just lying' stuff that a few people throw up. But equally, if you've never felt it, or haven't for a long time, it can be hard to believe that people do feel it. And that's where you get the strange stuff about 'Christians lying to themselves' and attempts to logically explain that there is no reason to believe this stuff.
 * The old saying is 'For those who believe, everything is proof: for those who don't, nothing is.' And this is so true, because those who believe have this feeling that makes attempts to ridicule their faith seem like someone who has never felt lust ridiculing you for having sex.
 * But your original question is slightly confused by including the Pope and certain literalist views. Roman Catholicism has a different view on scripture to the literalist/creationist Christians. Catholicism is much more open to allegorical interpretations, and interpretations that allow for the documents having been written by flawed humans over the course of centuries. So it is indeed possible that the Pope doesn't believe some stuff that you might assume he does, but we can be pretty sure he really believes in God. 86.164.57.20 (talk) 14:16, 10 July 2010 (UTC)
 * There is a big difference between religious self-affirmation and religious doubt. While both may be considered "believers", the former generally has positive life effects and the latter negative effects. Apart from "group" experiences in religion such as attending a church, a person may have a much stronger belief if they undergo a religious experience, in which their beliefs are often confirmed or expanded upon. A type of withdrawl from a religious or spiritual experience is often termed the Dark Night of the Soul, which can cause doubt within the believer or a lack of a sense of religious direction. Mother Teresa was a well-known sufferer of DNotS. Also, would it be safe to say that the opposite of agnosticism is gnosticism? ~ A H  1 (TCU) 14:34, 10 July 2010 (UTC)
 * Oh, I absolutely agree that it's more complicated than I described, and that's a really good addition. I just figured that sort of thing wouldn't really make sense to someone without understanding that there is this feeling in the first place. 82.24.248.137 (talk) 08:44, 11 July 2010 (UTC)


 * Some readers of this discussion may be interested in http://www.whywebelieve.ca/. -- Wavelength (talk) 21:11, 10 July 2010 (UTC)


 * In Breaking The Spell, Daniel Dennett pointed out the almost impossible goal of determining certain religious beliefs. 67.243.7.245 (talk) 14:16, 11 July 2010 (UTC)

The barge hitting the "Duck" boat
In a recent incident, a vintage amphibious "duck" boat carrying a load of 3 dozen or so tourists had engine failure in a river, and 10 minutes later was run over by a barge pushed by a Towboat(or perhaps pulled by a tugboat), resulting in the sinking of the tourist boat and the deaths of some passengers. I have seen many long barge strings going down rivers, with a powerful towboats behind them. A news article said the barge was being "directed" by a "tugboat," which sounds like it the propelling craft might have been in front of the barge. I wonder if they normally have a lookout at the front to inform the skipper if there is a boat or obstruction stopped ahead in the river or channel? Or is the pilot high enough above the water to see over the barge except for some dead zone in front of the barge? How long or over what distance does it normally take a towboat to stop a string of barges? Does a commercial boat carrying dozens of passengers normally have radio communication with other commercial craft on the river, or have a powerful boat horn, or other means of signalling its inability to get out of the way? Would it be the normal practice for passengers on a craft which has suffered engine failure in the middle of a river to be issued life jackets, rather than waiting until seconds before the collision to start grabbing for them? Edison (talk) 23:01, 9 July 2010 (UTC)


 * Wikipedia has an article on Duck tour that mentions this and earlier fatal incidents. Cuddlyable3 (talk) 23:42, 9 July 2010 (UTC)
 * Really no info there, any more than in the sketchy news articles. Basically, a barge going along a river, with no one able to see a craft or obstruction ahead, and with no capability to stop, and with the certainty that anything in its path which can't dodge will be destroyed, makes as much sense as someone driving a large truck at high speed down the highway with his eyes closed. Edison (talk) 02:27, 10 July 2010 (UTC)


 * I sincerely doubt that the barge pilot is at fault here. Barges are huge, slow, and not what one would call nimble in the water.  They undoubtably have forward lookouts (the last thing a barge wants to do is run aground on a submerged obstacle), but if a boat positions itself in front of the barge, the best options the lookout and the pilot will have will be jumping up and down and yelling really loudly.  to use your analogy, if you're driving down the highway in a Mini Cooper and you slam on your brakes without noticing that there's a semi right behind you, inertia will most surely have its way with you.  -- Ludwigs 2  03:32, 10 July 2010 (UTC)
 * Yes, indeed :-( SteveBaker (talk) 03:53, 10 July 2010 (UTC)
 * And whoever was driving the semi would get in deep shit for following too close Nil Einne (talk) 04:18, 10 July 2010 (UTC)
 * Of course, the rules of the road are different at sea. (And, of course, the semi driver wouldn't be at fault if the Mini driver made a sharp lane change and slammed on his brakes immediately.)  There are provisions in maritime law dealing with vessels operating in narrow navigable channels, vessels constrained by draft (that is, vessels that require deep water), and vessels with limited ability to manouevre.  There are rules regarding maintaining a lookout, but there are also rules about notifying other vessels about hazardous situations &mdash; in the recent incident named above, there is some question about whether the disabled duck boat issued a general warning to other vessels that they were in distress.  Given the limited information available to us, we should strictly avoid speculation about legal or moral fault. TenOfAllTrades(talk) 06:22, 10 July 2010 (UTC)
 * The difference with the rules of the road are that the guy who is behind a car in front is supposed to allow enough distance to be able to stop - so if someone gets rear-ended, it's clearly the fault of the guy at the back. However, this kind of rule only works well when everyone is organized into nice, neat lanes.  On a lake or wide river, people are criss-crossing about all over the place - and the stopping distances for big heavy ships can be measured in miles so leaving enough room to stop isn't possible in many cases.  There are cases when no-one is to blame...I think this is probably one of them.  The duck pilot unexpectedly lost power so he couldn't get out of the way - the barge captain had no way to avoid them.  Sad - but perhaps no fault. SteveBaker (talk) 07:21, 10 July 2010 (UTC)
 * Note that there are also "rules of the water", which generally include that commercial traffic has precedence before leisure craft, that sail has precedence before power, and, critically, that whoever has precedence in a potential conflict must maintain course. In this case, I agree with Steve, though. Unless the Duck operator was lazy in ensuring the seaworthiness of the vehicle. --Stephan Schulz (talk) 07:46, 10 July 2010 (UTC)
 * In Ludwig's the driver of the semi would still likely be at fault, particurly since if we are talking about the duck example, it was evidentally there for 10 minutes. But I agree that we shouldn't try to apply the road case to this, that was part of my point, Ludwig's example doesn't really help explain his/her point since in his/her given example the semi driver is generally expected to be able to stop in time without ramming into the Mini in front. This doesn't work very well at the sea for reasons like SB mentioned. Nil Einne (talk) 11:46, 11 July 2010 (UTC)
 * The problem for both truck drivers and barge pilots is that even when you DO leave plenty of stopping distance to the vehicle in front, you have no way to prevent someone from crossing into your lane right in front of you and cutting that gap in half (or worse). Your only recourse then is to slow down in order to open up an acceptably wide gap again - but it is in the nature of the beast that this takes time - so for a while, you don't have enough stopping distance even though you obeyed the traffic rules perfectly.  On water, with hundred ton barges, the whole thing plays out in agonizingly slow motion (10 minutes in this case) - but the result is exactly the same.  If you change lanes in your car and end up cutting into the stopping distance of that truck that's behind you, you are placing both yourself and the truck in danger...and that's what happened with the 'duck'. SteveBaker (talk) 17:09, 11 July 2010 (UTC)
 * I may be mistaken but my impression is it's unclear if the barge did try to stop for 10 minutes (while I appreciate it may take longer then 10 minutes for it to stop), the general consensus of the above discussion to me appears to be that it's not normally expected the barges have a lookout capable of seeing something 10 minutes away (which doesn't surprise). Also from what I've read, it's not clear the duck did 'change lanes' so to speak. It may have been in the 'lane' of the barge for 50 minutes for all we know.
 * The problem was it broke down in the lane, a rather unfortunate thing and then 10 minutes later it was struck by the barge. The equivalent in the case of a motorway would be if your Mini broke down in the fast lane of the motorway and 1 minute later (for example) a truck hit you. In such a case the truck would likely still be responsible although the Mini driver would also be in trouble if they failed to properly maintain their Mini, failed to signal that their car was broken, or whatever. There may be some edge cases like in extreme fog or something (particularly if the car was indeed failing to signal and/or the signals were broken) although I think they'll be very rare (in a case of fog for example I presume the normal expectation is the truck reduces speed so it can see obstacles with enough time to stop).
 * Note that if you change lane into the path of a truck, even if you do so unsafely, if 1 minute later the truck hits you because they were following too closely because they still hadn't adjusted (perhaps because they had a form of road rage), in the vast majority of cases the truck is going to be the one responsible (the driver of the Mini may be had up for an unsafe lane change or whatever but the truck driver still has to adjust their following distance no matter what stupid thing the Mini driver my have done 1 minutes ago). To avoid dispute, I will mention there are bound to be some edge cases where the truck driver won't be responsible because it's not resonable to expect them to adjust speed. For example if the truck brakes are broken, or it is travelling up a hill and can't safely slow down or whatever.
 * To put it a different way, it seems to me this 'changing lane' thing is a red herring as we've no indication the barge shouldn't have been there, or suddenly appeared out of no where, rather it appears it was there for a while since it was broken down for at least 10 minutes and may have been there for a lot longer while it was working. In other words, the way I see it this truck equivalency just doesn't work because the rules of the water don't require or expect a barge to have a lookout to see any obstacles 10 minutes away, so even though it had been there for 10 minutes, and may have been in the 'lane' for longer, it not clear they saw it that far out, and it doesn't appear it was expected they should have seen it that far out, and one of the reasons is it's not even clear the barge could have stopped in 10 minutes nor is it clear they should have tried had they even be aware it was broken down 10 minutes in front of them.
 * Nil Einne (talk) 17:44, 11 July 2010 (UTC)


 * There should certainly not be any placing of blame here, just a quest for referenced information. Nor should there be a determination of "no fault." I would not apply the highway analogy too closely, but in a highway analogy the Cooper did not "slam on the brakes." It had been disabled in the roadway for ten minutes. In the railroad analogy, a high speed train has a very long stopping distance which often exceeds the distance at which it can see a car stopped on the tracks (the US, unlike UK, has far more grade crossings than roadway/railroad overpasses/underpasses). But modern railroads have an electric block signal system to tell the driver/engineer if there is train traffic on the next section of track. This does not protect a car stopped on the crossing, but it should prevent catastrophies of train hitting train. It is surprising that speeeds of a barge are allowed too great for it to stop  before hitting, say another barge or boat large enough to sink the barge. Even at 12 knots, a high speed for a barge string, a 10 minute warning would have allowed a couple of miles for the barge to stop. A tugboat typically has a several thousand horsepower engine. I have seen one rise up in the water like a stunt boat while trying to pull a barge off a mud bank. Has the specific tugboat in question ever been identified? Is there a reference for the stopping distance that a tugboat/barge combination is supposed to maintain on the Delaware River in Philadelphia? Rationally, the allowed speed should be limited by visibility and stopping distance. Rules like this are typically spelled out as 20/20 hindsight gets written into administrative law after the many thousands of marine tragedies in the last 200 years. This concerns me a bit because, in addition to some tourists being killed and a boat sunk in this case, barges often carry dangerous cargos. I well remember my family having to evacuate suddenly once when a batge sank and chemicals on board released chlorine gas. If a barge string stops because of engine trouble, how is the following barge supposed to avoid a similar collision with even worse consequences, if the stopping distance is the claimed unspecified "miles?" Edison (talk) 13:17, 11 July 2010 (UTC)
 * Apologies if I took this somewhat offtrack. I came across which goes into some of the complicated factors although it is looking at it primarily from a blame angle. The comments also have some interesting suggestions (although as always take them with a grain of salt) Nil Einne (talk) 18:10, 11 July 2010 (UTC)