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May 21

Absorbent glass mat (AGM)

can i get a Absorbent glass mat (AGM) battery 4 my honda accord —Preceding unsigned comment added by Tom12350 (talk • contribs) 04:16, 21 May 2010 (UTC)

It would probably be more expensive than an ordinary one, and you won't see much difference if it isn't a hybrid. --Chemicalinterest (talk) 15:37, 21 May 2010 (UTC)

Actually, quite a few modern non-hybrid cars use these batteries - they last longer and are both smaller and lighter than a regular car battery. So even on a non-electric car, they save energy just by making the car lighter. My car has one - on previous MINI Cooper'S models there was no space under the hood for the battery - so it had to go into the trunk - I was surprised not to find it there...and doubly surprised when I couldn't see it anywhere under the hood either! On my car, the amazingly tiny AGM battery is tucked away in an extremely hard-to-reach place (against the fire-wall right beneath the lower-right edge of the windscreen, hidden in the ducting and air-vent metalwork). The claim is that they are reliable enough to never need replacing...We'll see!

I don't see any reason why you shouldn't be able to replace a conventional battery with one of these gizmo's - weight savings are always a good thing! But it might be wise to check with your local Honda dealer before you do it...you never know what weird stuff is different with them. SteveBaker (talk) 20:19, 21 May 2010 (UTC)

Photon clocks in GR

According to the equivalence principal, in a uniform graviational field, clocks at different heights will run at different speeds. If two identical photon clocks (a clock consisting of two mirrors seperated by a fixed distance with a photon reflecting between the two to measure time) are placed at different heights, then it seems that they too must run at different rates. But this would seemingly imply that the speed of light changes with height, which is obviously not true. So what gives? 173.179.59.66 (talk) 08:02, 21 May 2010 (UTC)

I assume you mean at different heights in a spherically symmetric gravitational field (which is not uniform as the direction and strength of the field both vary). If you have two photon clocks at different heights then the curvature of spacetime is different and light travels along different geodesic paths within the two clocks - so you need to think about what you mean by "identical" photon clocks. Parallel transport may be a useful concept here. Gandalf61 (talk) 08:21, 21 May 2010 (UTC)

No, I meant a uniform gravitational field. 173.179.59.66 (talk) 16:58, 21 May 2010 (UTC)

Along with time dilation, you also have length contraction. So the distance between the two mirrors will be shorter in the clock in the stronger gravitational field. Ariel. (talk) 20:07, 21 May 2010 (UTC)

Are you sure you got that the right way round? Would not the stronger field be time dilated, compared to the weaker field, and therefore have a bigger mirror spacing to get the same time delay. You could get the same idea by measuring wavelength. Graeme Bartlett (talk) 20:55, 21 May 2010 (UTC)

And the gravitational fields are the same for both clocks, no? Unless you meant potential...173.179.59.66 (talk) 21:19, 21 May 2010 (UTC)

If you really do mean a uniform gravitational field then the two clocks are indeed equivalent and run at the same rate from the point of view of any observer. You will only get a difference in time dilation rates if the gravitational field is non-uniform. Gandalf61 (talk) 21:28, 21 May 2010 (UTC)

I have to disagree with you on that one. Replace the uniform gravitational field with a uniformly accelerating rocket, with a clock A at its front and a clock B at its tail. If clock A emits light pulses at a uniform rate, then the time it takes for any pulse to reach point B from point A will L/(c+v), were L is the distance between the two clocks (which remains constant). Because v increases , the pulses will take increasingly less and less time to reach clock B, so an observer at B will conclude that the clock at A is running faster. Equivalently, redshift still occurs in a uniform graviational field, so relative time dilation must necessarily still occur. 173.179.59.66 (talk) 05:32, 22 May 2010 (UTC)

You need to be clear about what you mean by "uniform acceleration". If your ship is a solid object with a rocket that accelerates the back at a constant rate, then the (constant) acceleration of the front of the ship is not the same as the (constant) acceleration of the back. This situation is often called "uniform acceleration", but the acceleration is not actually uniform, if "uniform" means "the same everywhere". You also have to be careful when you say that the distance between the clocks is constant. It's not constant with respect to any inertial reference frame. It's constant with respect to a Rindler frame, but that doesn't match the usual special relativistic definition of length. -- BenRG (talk) 01:45, 25 May 2010 (UTC)

It's not clear to me what a "uniform gravitational field" would be in general relativity. The closest thing is flat spacetime in Rindler coordinates, which is not uniform inasmuch as the acceleration needed to stay at the same (x,y,z) position varies as a function of x. Trying to apply length contraction and other concepts from special relativity to this problem is hopeless. (Length contraction barely makes sense in special relativity, in my opinion, but that's a different question. It makes even less sense in general relativity.) There's no difficulty in the definition of identical clocks as long as they're small compared to the scale of variation in the gravitational field (which is the usual assumption).

When people say that the clocks run at different rates, what they mean is that if you send periodic signals ("ticks") from the clocks to a common location, the received signal rate at that location will be different for the two clocks. This is the same as saying that there is gravitational redshift. Light clocks essentially define what time means at a given location, so you can't say that they run fast or slow in any absolute sense. If you do a local speed-of-light measuring experiment with a light clock and a meterstick, you'll get c. -- BenRG (talk) 22:23, 21 May 2010 (UTC)

I'm not very well aquainted with general relativity, but I'm using as an approximation a gravitational field equivalent to a uniformly accelerating rocket, which is simple enough so that I can understand with my current level of knowledge. In that case, two observers at different altitudes will the other's clock run slower or faster depending on the relative height of the observers.173.179.59.66 (talk) 05:37, 22 May 2010 (UTC)

Time dilation due to constant acceleration depends on rate of acceleration and initial velocity, but not on initial separation - see Time dilation#Time dilation at constant acceleration. Therefore, if your definition of "uniform gravitational field" is "equivalent to constant acceleration", then the time dilation in your "uniform gravitational field" will not depend on separation either. So all (stationary) clocks in this "uniform gravitational field" will run at the same rate. What makes you think they will not ? Gandalf61 (talk) 14:18, 22 May 2010 (UTC)

In the wikipedia article you linked to, the observer is outside the rocket, and so the time dilation in that case is just a special relativistic effect. In my scenario the observers are both inside the rocket. The thought experiment that I mentioned above shows how two clocks at different heights in an accelerating rocket will run at different rates. If you don't trust me, then here's a more comprehensive article: http://www.peaceone.net/basic/Feynman/V2%20Ch42.pdf173.179.59.66 (talk) 18:10, 22 May 2010 (UTC)

Feynman's observer is outside of the rocket too. For an accelerated observer inside the rocket, the lengths L1 and L2 would be the same. You need to have an observer outside of the rocket, in an inertial frame of reference, to establish a baseline time against which you measure proper time and hence calculate time dilation. Gandalf61 (talk) 16:11, 23 May 2010 (UTC)

Yeah, and this outside observer will see both clocks run at the same rate. But the observers inside the rocket will notice a discrepancy. 173.179.59.66 (talk) 04:27, 24 May 2010 (UTC)

Then you seem to have answered your own question. The true time dilation relative to an inertial frame of reference is the same at all points in the uniform gravitational field. The apparent time dilation observed by two stationary observers within the uniform gravitational field comparing their proper times, does depend on their separation, but this is a consequence of the fact that these observers are not using an inertial frame of reference. Gandalf61 (talk) 09:01, 24 May 2010 (UTC)

There's no "true" or "apparent" time dilation. There is only the results of various experiments. I'm still not sure what a "uniform gravitational field" is. You (Gandalf) seem to be talking about two ships accelerated by independent, identical rockets with one clock aboard each one. The anon is talking about one ship accelerated by a single rocket with two clocks on board. These are different physical situations. In Newtonian physics they would be equivalent, but relativistically they aren't. See also my reply above (the one dated today). -- BenRG (talk) 01:45, 25 May 2010 (UTC)

Note that in weak gravitational fields, the metric in natural units is approximately given by:

$ds^{2}=(1+2V)dt^{2}-(dx^{2}+dy^{2}+dz^{2})$

where V is the Newtonian gravitational potential. Count Iblis (talk) 17:08, 23 May 2010 (UTC)

Wind Turbine and surface drag

I read an article on a new paint that reduces wind resistance [1], and one of the applications mentioned was wind turbines. My first thought was that you would not want to reduce wind resistance on a turbine or the air would just slip by without turning it. Then I began to wonder whether the turbine is turned by a pressure difference rather than friction with the air, and if so does the creation of the pressure difference rely on friction? Even if the wind resistance is not responsible for the effect, is it in any way detrimental? I am now completely confused as to what actually makes a wind turbine turn! -- Q Chris (talk) 09:29, 21 May 2010 (UTC)

It depends on the type. Some wind turbines work by redirecting the air flow sideways, creating torque via Newton's third law. These usually have flat vanes angled into the wind. Most modern high-performance turbines have an airfoil profile and generate torque by the pressure difference caused by the different speeds of air travelling over the more curved leading side and the straighter trailing side. In either case, energy lost to friction just warms the blade and does not contribute to the generating capacity. --Stephan Schulz (talk) 09:40, 21 May 2010 (UTC)

Thanks Stephan. I can see that the energy that just heats the blades will not aid generation, but will it be detrimental to the generation? As far as I can see the air will be slipping off in the same direction that the blades rotate, so it won't make much difference either way. -- Q Chris (talk) 10:03, 21 May 2010 (UTC)

What friction will do is slow down the airflow. Thus, somewhat simplified, you have a reduced "effective wind". In the case of simple vanes, for example, the induced sideways motion of the downwind air will be less (part of the energy is lost to friction), and hence the opposing force acting to turn the vanes will be less. A similar argument can be made for the airfoil. --Stephan Schulz (talk) 11:33, 21 May 2010 (UTC)

Also, friction can result in turbulence, which can wiggle the blades and cause heating and wear and tear on the bearings. Thus, laminar flow is preferred. The blades themselves may also tend to get pitted more if grains of sand are dashed against them, due to turbulence. This could in turn cause more friction and turbulence, and also unbalance the blades. StuRat (talk) 15:05, 21 May 2010 (UTC)

What is this weird creature?

Opossum

Opossum

River otters

weird creature Kittybrewster ☎ 11:21, 21 May 2010 (UTC)

Here's some more pictures: [2]. Most of the comments (i.e. here) I've seen are saying otter or possum, or possibly a nutria or groundhog. Buddy431 (talk) 12:35, 21 May 2010 (UTC)

I vote for "exceptionally ugly/drowned looking opossum." Compare with this beauty queen. Either than or an otter whose lost a lot of fur on the snout. (The skull is very otter-like.) --Mr.98 (talk) 12:37, 21 May 2010 (UTC)

If it's 'playing possum' it's overdone it.. Really appears to 100% dead possum. cf image seach for "possum skull" - note the lower 'canine' - not otter as far as I know.

Does anyone know what happens to the hair - is it common for it to fall out of dead animals in water? eg this [3] 77.86.115.45 (talk) 16:29, 21 May 2010 (UTC)

The face looks like a wolverine's, but the article says "The creature's tail is like a rat's tail and it is a foot long.", which suggests possum. Maybe a hybrid? Wolverines don't have rat-like tails do they? Vranak (talk) 17:59, 21 May 2010 (UTC)

I'd vote for otter - perhaps with mange, perhaps something else - decomposition? - causing the fur loss. The face looks very otter-like to me, though I'm curious about the tail. Of course, if hair loss also occurred on the tail, it could well look like a rat tail. Matt Deres (talk) 19:39, 21 May 2010 (UTC)

I don't think anyone would look at an otter tail and say it was rat-like though. Vranak (talk) 19:51, 21 May 2010 (UTC)

Comparing to the pictures to the right (feel free to adjust the formatting, I can't figure it out), I think the snout is too short for an opossum, and the ears too small. Also, the place where the whiskers would be doesn't seem quite right either. I'm voting tentatively for the river otter. Perhaps without fur on the tail, someone who has not seen a rat recently would say it looked like a rat tail. The river otter's ears look closer to me, as does the snout and the whiskers. Falconus^{p t c} 21:03, 21 May 2010 (UTC)

Note: I revised inaccurate captions on the pictures. I am fairly sure, for example, that the bottom picture is not a badger, but rather a river otter.Falconus^{p t c} 22:06, 21 May 2010 (UTC)

Bovine Tubersulosis versus the Human Form.

During my research into my family history I've discovered that my grandfather lost three of his siblings over a 5 year period at the turn of the 20th. Century. I am wondering if occupation conveyed a part of the other siblings immunity? I know, for example the Jenner discovered that immunising someone with Cow Pox gave them a marked immunity to Smallpox, hence my curiousity regarding T.B.11:47, 21 May 2010 (UTC)~ —Preceding unsigned comment added by 2.102.26.59 (talk)

Assuming that contact with Mycobacterium bovis can generate resistance to Mycobacterium tuberculosis (the more typical cause of tuberculosis in humans), it is important to take a major difference between M. bovis and the cowpox virus into account: the latter doesn't cause a typically life-threatening disease, while the former does. This is what made inoculation so useful. – ClockworkSoul 16:55, 22 May 2010 (UTC)

0t,1t 2t bend test / galvanized/colour coated coils

Does anyone recognise what is being asked here Wikipedia:Reference_desk/Miscellaneous#Bend_test ? 77.86.115.45 (talk) 11:57, 21 May 2010 (UTC)

Oil spill - quick drying cement?

Why cannot the source of the oil spill just be covered with a large amount of quick drying cement. After the first batch has hardened, another batch, then another. This is not a silly question - cement does set under water. 92.28.253.142 (talk) 14:32, 21 May 2010 (UTC)

I believe the force of the oil, which is coming out under pressure, would push the concrete out of position before it could harden. StuRat (talk) 14:58, 21 May 2010 (UTC)

As do many polymers, going back to the wet-climate-set Chinese lacquer. My guess is that the big question is how to put a big heavy block onto a big hole spewing crud at very high pressure and not just having it get knocked to the side by the spray. Consider how hard it is to stop the water from coming out of a hose with your thumb. SamuelRiv (talk) 15:07, 21 May 2010 (UTC)

As an extension to the above idea - first cover the flow with large chunks of broken stone - so that the oil is diffused out between the gaps in the stone - the concrete would be less likely to be swept away before setting due to the reduced local flow rate.. In practice once completed the flow would probably just exit below the stone - and scour the (loose?) sea bed, creating its own channel.

I wonder if a rheopectic substance or Dilatant would help here (probably not).77.86.115.45 (talk) 16:13, 21 May 2010 (UTC)

Along these lines, Google for: bp oil "junk shot". DMacks (talk) 16:29, 21 May 2010 (UTC)

I wonder if they've considered using (hydraulic?) clamps to 'crimp' the end of the pipes to restrict the flow? - are the pipes made of a workable steel or a brittle steel?77.86.62.107 (talk) 16:57, 21 May 2010 (UTC)

Not a good idea, it could break the pipes. Even workable steel has a limit to which it could be cold-worked before it starts to crack (generally no more than 20% deformation), so "crimping" the pipes won't work. 67.170.215.166 (talk) 05:05, 22 May 2010 (UTC)

And is it possible that it is impossible to close this oil spill until all the oil has run out? Mr.K. (talk) 16:00, 21 May 2010 (UTC)

No, just until the pressure drops. Are they not planning to drill nearby to relieve the pressure? Dbfirs 17:19, 21 May 2010 (UTC)

"They" (we) are planning to do just that, but it could take up to several weeks due to the great depth of the well required and also the difficult rock formation. (Well, I don't know all the particulars -- I work on the refining end, not the extraction end -- but that sums up what I've heard from the company management.) FWiW 67.170.215.166 (talk) 05:00, 22 May 2010 (UTC)

I believe the amount of oil shooting out of the broken pipe would prohibit this sort of remedy. And it's a little sloppy too, just pouring heaps of cement over a leak. Reminds me of Chernobyl. And just getting the cement out in the middle of ocean, and then down miles beneath the surface, is rather more problematic than, say, trying to plug Old Faithful in the same manner. Which, come to think of it, seems rather problematic in itself. Mind you one is a pipe, the other, a natural geyser -- apples and oranges and all that. But the point remains, pouring cement at those depths, that far from land -- not entirely trivial. But ultimately, I feel that the force of the oil is the critical factor. From all I have read, pumping drilling mud into the aperture is the way to go. Vranak (talk) 17:50, 21 May 2010 (UTC)

If I understand it correctly, the advantage of injecting heavy mud is that it can flow down the borehole against the oil counterflow. As the depth of the borehole fills with mud it creates a backpressure to gradually reduce the oil flow while also narrowing the part of the borehole through which the oil is flowing. The other approach, of capping the pipe, can only work if the pressure inside the cap is kept below the surrounding water pressure. Given the amount of dissolved gas from this well, that's not a trivial thing either. As the gas rises and expands it undergoes adiabatic cooling (like the working fluid in a refrigerator or air conditioner). On mixing with water this cold gas can form ice crystals that clog the pipe to the surface platform. This appears to be what happened to the first attempted cap. LeadSongDog come howl! 19:31, 21 May 2010 (UTC)

Not exactly ice crystals but methane clathrate, which is less dense than pure water ice. The mud (it's actually synthetic) is made extra dense by adding the mineral barite to it, which is how highly pressured oil and gas are controlled when they are first encountered when drilling. Mikenorton (talk) 19:55, 21 May 2010 (UTC)

The key problem here is three-fold. One is pressure - the oil isn't just slowly washing out - it's coming out at some ungodly pressure. Below the seafloor, there is about 18,000 feet of solid rock pressing down on the oil reservoir - that's an incredible amount of pressure. Nothing like wet cement is going to be able to resist that. Second is temperature. This oil is incredibly hot. Third is that there is a lot of debris there - for starters, there is 5,000 feet of crumpled up pipe that fell from the rig onto the well-head. Then there is debris from the rig itself. So wet concrete is out of the question. Even dropping a very large concrete block onto the well-head won't work because the oil is under such pressure, it would just channel a route through the sand and stuff underneath it and squirt out around the edges. So you'd have not one neat little pipe to cap - but the entire perimeter of the concrete block. The various domes and such they've tried (and failed) with would have to have the oil continually sucked out of them - with a suction more powerful than the pressure of the oil - so as to 'suck' them onto the sea floor. These are all very difficult solutions.

The one I could imagine working would be to construct four vast rolls of flexible water/oil-proof fabric or plastic sheeting - each 5,000 feet long by (let's say) 100 feet wide - and to unroll these from the sides of ships to create four curtains around the well-head - then to heat-seal or 'zipper' the edges together as they are unrolled to make a vast, square-cross-section, floppy tube that could eventually rest on the seafloor far enough from the well head to avoid the debris field and the immediate heat/pressure of the oil. (You'd have to weight-down the bottom edge of each strip). This container would start to fill up with oil - which could then be pumped out from ships on the surface. The large width of the tube would ensure that the oil had room to expand and to relieve the pressure. Since oil is less dense than water, and we're pumping out the inside of this giant tube - any small leaks would have water flowing in - not oil flowing out. The technical difficulty is in handling such enormous amounts of fabric - and how well the stuff performs at the very low temperatures at the bottom of the ocean - also, how the pressure of ocean currents would work to push the thing out of shape.

SteveBaker (talk) 20:03, 21 May 2010 (UTC)

You're hired. Get your ass to the Gulf of Mexico. Comet Tuttle (talk) 20:16, 21 May 2010 (UTC)

Well, there's theory, then there's practice. I should think that Red Adair was so good at capping blowouts because of his experience in the field, not so much a sound theoretical background. I also imagine that too much theory and not enough experience was one of the chief causes for this mess in the first place. Vranak (talk) 20:20, 21 May 2010 (UTC)

The oil coming out now is actually at low pressure. It's being dumped into the ocean as quickly as the weight of the rock is able to force the oil into the well, and so there is very little accumulation of pressure. (Even given the large weight of the sea floor, oil will move slowly through the pore spaces in oil bearing rock.) If you are losing "only" 100,000 barrels per day through a 50 cm pipe then the average flow rate is only about 1 m/s (2.2 mph), which would imply the pressure difference of only about 500 Pa between the well and sea floor. Any person with a stout piece of plywood could actually block that off. The problem is that the weight of the sea floor will continue forcing more oil and gas into the well space even after you block the opening, so pressure will buildup and unless your obstruction is very sturdy the well will blowout again. Dragons flight (talk) 00:08, 22 May 2010 (UTC)

Why can't they just use a wider (4 -5 ft) pipe from the source to the surface and that would no doubt solve the problem of slushing up the pipe with frozen methane? —Preceding unsigned comment added by 98.221.254.154 (talk) 02:05, 22 May 2010 (UTC)

Actually the pipe would still slush up, it would just take longer. 67.170.215.166 (talk) 05:21, 22 May 2010 (UTC)

I would like to clear up a scientific inaccuracy that seems to be floating around in the above posts. The reservoir pressure is not exactly caused by the weight of the 18,000 feet of rock overhead. Rock is not a fluid (not a good one, at least); it does not behave like a hydraulic head; although the weight of the rock does contribute to the pressure, the real defining equations for pore pressure are a lot more complicated. The pore pressure contributes to, but must be converted into, an effective reservoir pressure. Finally, this can be used to estimate a pressure at the wellhead on the seafloor. The Terzaghi equation, in conjunction with reservoir characterization and geomechanical measurements, can be used to calculate the reservoir pore pressure; or an empirical law relating pore pressure to some other geomechanical property or observable from a borehole logging measurement. Finally, the fluid seep into the borehole needs to be modeled and eventually a hydraulic head can be calculated to determine the pressure at the exit point of the wellhead (on the seafloor) or at the ocean surface. To do all this, you need to know a lot of details about the fluid composition in the bore (probably drilling mud and other debris at this point), as well as details about the reservoir that only a privileged member of the BP E&P team would have access to. I just want to make sure nobody is thinking of applying the old "P = ρ g h" static pressure-head equation with the density of rock in a feeble effort to calculate the fluid pressure - it is unfortunately much more complicated than that. The short answer is, we don't know what pressure the oil is under as it rises to the well-head - the fact that there was a blowout indicates that neither did BP or its subcontractors. Nimur (talk) 02:44, 22 May 2010 (UTC)

We do know that at the time when it started to flow that the pressure in the reservoir was somewhere between the hydrostatic pressure (the pressure at the base of a column of water equal to the depth) and the lithostatic pressure (the pressure at the base of a column of rock equal to the depth). Most reservoirs are 'normally pressured' and lie close to the hydrostatic pressure, taking into account the column height of the hydrocarbons involved. Some reservoirs are 'overpressured' and lie closer to the lithostatic gradient but never reach it because high pressures will cause fracturing of the top seal (the impermeable layer that helps form the top of the 'trap') and this is known as the fracture gradient, so again we know that it will be less than that. After flow has started the pressure will start to reduce, something known as depletion, but the amount of depletion depends on the extent to which water flows into the reservoir as the hydrocarbon is removed, something known as 'aquifer support'. As to the blowout, the gas may have come from a shallower formation (unless this is associated gas i.e. coming out of solution from the oil), which should have been held back by the cement liner or casing in the wellbore above the reservoir. Mikenorton (talk) 13:12, 22 May 2010 (UTC)

I don't udnerstand why they can't just bring another rig to that location, send a pipe down and resume normal operations. Why not?--92.251.177.211 (talk) 20:30, 22 May 2010 (UTC)

BP are currently drilling two 'relief wells' to try and intersect the original wellbore, but it takes time and the target is rather small. Mikenorton (talk) 20:36, 22 May 2010 (UTC)

Field Strength of LHC Magnets

I am told that the magnets at the 27 km circumference LHC operate at 8.3 Teslas, while the protons contained in the beam have an energy of ~7 TeV (see Wikipedia LHC article). Trying to match these data up using simple physics fails, and so I'd like to know where my mistake(s) is/are.

As protons are travelling at near the speed of light:

$mv\approx {\frac {E}{c}}$

$F={\frac {mv^{2}}{r}}=Bqv\implies B={\frac {mv}{rq}}\approx {\frac {E}{crq}}$

Substituting in values:

$B={\frac {7\times 10^{12}{\mbox{ eV}}\times 1.602\times 10^{-19}{\mbox{ J eV}}^{-1}}{3\times 10^{8}{\mbox{ m s}}^{-1}\times 4300{\mbox{ m}}\times 1.602\times 10^{-19}{\mbox{ C}}}}=5.4{\mbox{ T}}$

I presume I've missed off some relativistic effects, but even when I tried to account for some of them, I still got around 5.4 Tesla. Any suggestions? --80.229.152.246 (talk) 15:46, 21 May 2010 (UTC)

(altered/corrected your ref tags - no reference section at bottom of this page)

Is it possible that the figures you've used are maximum operational limits - eg the magnets can go up to 8.3T safely ? (but are operated at a lower figure?)77.86.115.45 (talk) 16:19, 21 May 2010 (UTC)

there doesn't seem to be a reference for the 8.3T figure to get its context from.77.86.115.45 (talk) 16:23, 21 May 2010 (UTC)

There are a few mentions of 8.3 T being the required field in LHC: The Guide. --80.229.152.246 (talk) 17:38, 21 May 2010 (UTC)

Mmmh actually - plan B - the magnets aren't actually completely circular are they?? ie it's magnet/straight/magnet/straight etc? Thus the turning circle at the magnetic turning sections must be smaller than the radius of the machine - hence a higher magnetic field required - ie the colider shape in not a circle but a n-agon (polygon) (with rounded corners) - surely this must be the case? So radius is less than 4300m. 77.86.62.107 (talk) 18:31, 21 May 2010 (UTC)

I'm pretty sure it's quite circular. But what about length contraction? The magnet slightly ahead of the current position of the proton is length contracted toward the proton, so the radius might be lower than what you calculate. But it's not totally ahead of the proton, just slightly, so the contraction is only a fraction of the total speed. Ariel. (talk) 20:16, 21 May 2010 (UTC)

Fairly certain polygonal eg [4] states 1232 15m dipole magnets - so that's 18.5 km of bending magnets - but the circumference is 27km. 77.86.62.107 (talk) 20:27, 21 May 2010 (UTC)

(ec) That's correct. The bending magnets occupy only a portion of the ring's total circumference. The remainder contains quadrupole focusing magnets, experiments, and gaps between magnets. In total, the LHC contains 1232 dipole bending magnets, each with a length of approximately 15 meters. (That PDF link contains a number of other important specs for the bending magnets, as well.) 15 meters times 1200 magnets accounts for just 18 kilometers (about two thirds) of the total tunnel length. TenOfAllTrades(talk) 20:33, 21 May 2010 (UTC)

...back of envelope attempt at getting radius of curvature of magnetic sections - since for each turn (2pi/1232 radians) angle is small I assume sin x=x and cos x=1

r_effective=4300m , L=(27000m-18500m)/1232 (length of each straight section), A = 2pi/1232 (angle radians)

r=radius of curvature of magnetic sections

I get r_effective/r = (rA+L)/rA using similarity of triangles (approx since cosA~1)

solving for r (using pi=22/7)

gives r=4300x(15/22)

Thus using the original equation with the new r I get magnetic field = 5.4 x (22/15) = 7.92 (pretty close to the 8.3 quoted)

Looks like this method is probably along the right lines.?77.86.62.107 (talk) 21:36, 21 May 2010 (UTC)

I should probably point you back to the PDF that I linked in my response — it actually has more precise values for the length of each magnet, as well as explicitly specified bending radius and angle per magnet. The real magnet length is actually a bit less than 15 m — the specs say 14.3 m — which probably just about accounts for the discrepancy between your calculated field value and the nominal. TenOfAllTrades(talk) 03:11, 22 May 2010 (UTC)

doh, silly me I should stop skimreading - yep my estimate came out at ~2930m - the pdf gives ~2800m .. giving an unsuprising 8.3T for the required field which is spot on.77.86.62.107 (talk) 03:23, 22 May 2010 (UTC)

Thanks everyone. I'm glad to see it's not down to awkward relativistic effects like length contraction and the like (I did consider that but didn't think it'd have a large enough effect, plus I have no idea how to work that out...). --80.229.152.246 (talk) 15:45, 22 May 2010 (UTC)

Iron in high oxidation state

Is there any way to create iron compounds with an oxidation state of more than +3 using household chemicals? --Chemicalinterest (talk) 20:57, 21 May 2010 (UTC)

Potassium ferrate - you would probably only have access to the sodium compounds - sodium ferrate is more unstable (see http://library.sciencemadness.org/library/ferrates.html)

In sweden you can produce it from bleach possibly http://sv.wikipedia.org/wiki/Natriumferrat ?? seems to be confirmed by youtube http://www.youtube.com/watch?v=pUvdETUQPuo (I think this is probably true) 77.86.62.107 (talk) 21:49, 21 May 2010 (UTC)

I tried adding KOH and household bleach (NaClO) to ferric oxide but it didn't react. (Oh and I boiled it).--Chemicalinterest (talk) 22:42, 21 May 2010 (UTC)

Watch the youtube video linked above - you need strong bleach, and they boiled it.77.86.62.107 (talk) 22:47, 21 May 2010 (UTC)

Oh.. and the step were they add ammonia at the end - don't try that if there is excess bleach ammonia can react with it to make hydrazine - explosions can potentially follow... alternatively the reaction produces chloramines - which are toxic.. (or nitrogen trichloride even which too is explosive) In fact I wouldn't try this at home - boiling bleach sounds like a recipy for disaster in one form or another..77.86.62.107 (talk) 22:56, 21 May 2010 (UTC)

Pushing or pulling Asteroids

Lets say we have a spaceship that's powerful enough to move asteroids. Is it easier for it to push it or to pull it? ScienceApe (talk) 21:04, 21 May 2010 (UTC)

A joule is a joule is a joule. Presently, I don't believe we even have any technology that is capable of such a feat, so it's a purely speculative issue at this point, yes? Vranak (talk) 21:07, 21 May 2010 (UTC)

It would be easier to pull using the gravity inherent in the ship's mass, because that would not use any external energy. dude❶❽❶❽ (talk) 21:11, 21 May 2010 (UTC)

You still have to use energy to keep the gravity tractor in the right place. --Tango (talk) 21:13, 21 May 2010 (UTC)

Pushing is easier. Dauto (talk) 21:17, 21 May 2010 (UTC)

From an energy point of view it's the same, but from an engineering point of view pushing is easier. For two reasons: One you can just push the asteroid, and don't need some method of attaching to it. Two: If you pull, your exhaust gases will impact on the asteroid, which will push it back - you'd need some way to reroute your exhaust around the asteroid. Ariel. (talk) 21:42, 21 May 2010 (UTC)

Ok. But think of failure. If your're gunning it full steam towards an asteroid and the 'link', whatever that may be, fails, then you're going to crash into it (unless your distance is great, or you have good retro rockets, etc). If you're pulling it, you just go in the opposite direction. Vranak (talk) 21:44, 21 May 2010 (UTC)

That assumes pushing from a distance. If the asteroid is strong enough to be pushed from a single point without breaking up, the spacecraft can be brought right up against it first (in effect a soft landing) and then start pushing. However, you would need to keep the pushing force accurately aligned with the center of mass. --Anonymous, 23:08 UTC, May 21, 2010.

Exactly. In any case, a worst-case scenario looks a lot worse when you are pointing towards the 'roid, rather than away from it. Well, if it were remotely-operated, I suppose a hull breach isn't necessarily curtains. Vranak (talk) 00:16, 22 May 2010 (UTC)

I too would pull - for using you need a structure to transmit the pushing force from the front of the spaceship - but the force propelling the spaceship is probably at the back - would need a strengthened airframe - you also can't see where you are going..

For pulling all you need is some ropes - these can be attached close to the propulsion source - ropes can be long - gas back draft shouldn't be a problem..77.86.62.107 (talk) 21:46, 21 May 2010 (UTC)

Gas back draft most certainly is a problem. Or earth if you go far away the air disperses the gas. Not so in a vacuum. The gas will go directly toward the asteroid, and will totally cancel out the effect of the propulsion. It would be like trying to move a sailboat by attaching a fan to the boat and blowing on the sail. Ariel. (talk) 23:43, 21 May 2010 (UTC)

That depends on whether the gas molecules collide after being ejected - if so the gas will disperse (in a 'cone' shape) - I think it would be hard to make a rocket nozzle that outputs molecules that do not collide with one another - would require low gas densities - though it would be the most efficient.77.86.62.107 (talk) 00:34, 22 May 2010 (UTC)

For pushing you have to locate and get exactly behind the asteroid's center of mass or the thing will start spinning instead of going the direction you expect. For pulling this is not a problem. Cuddlyable3 (talk) 22:24, 21 May 2010 (UTC)

It's exactly the same problem for pulling. If the force, whatever the direction, doesn't go through the centre of mass then you will introduce a torque. If you are using a gravity tractor, then the force is automatically through the centre of mass, but if you are pulling it using a rigid scaffolding or something, then it could be a problem. If you are pulling it using a flexible cable, then the torque will be temporary and it will soon end up going through the centre of mass. You can avoid a torque when pushing by having the engine attached to the asteroid via a gimbal - that way you can make sure the thrust is straight "up", which means it goes through the centre of mass (actually, that may only be precisely true for a spherical asteroid, but I think the principle can be generalised). --Tango (talk) 22:39, 21 May 2010 (UTC)

Also for turning - if the spaceship has weak turning thrusters and powerful main engine fixed on axis then it is easier to pull since "thrust vectoring" can be used - whereas when pushing the turning thrusters would be required to turn the entire combined mass - depends on what sort of spaceship you're using I suppose...77.86.62.107 (talk) —Preceding undated comment added 22:34, 21 May 2010 (UTC).

see: Pendulum rocket fallacy.—eric 23:10, 21 May 2010 (UTC)

I don't think that fallacy is relevant. The IP is correct - if you are pulling the asteroid using a cable then all you need to do to turn is change the attitude of the rocket. If you are fixed to the asteroid, thrusting in a fixed direction and pushing it along then you would need to turn the whole asteroid. However, if you are fixed to the asteroid but can change the thrust direction of the main engine then you can use the main engine to turn the asteroid and it becomes pretty easy (in fact, it's probably just as easy as in the pulling case, since in both cases you will use the main engine to turn the asteroid). An alternative would be to push the asteroid using a rocket than can move around on the surface (probably hopping around - there is so little gravity on a typical asteroid that the thrust required to hop would be minimal, you could probably do it with an air horn!). --Tango (talk) 23:25, 21 May 2010 (UTC)

(I was assuming that someone would be steering the ship . but it is an interesting link)77.86.62.107 (talk) 00:37, 22 May 2010 (UTC)

I like the idea of pushing with a clamp-on linear accelerator, which mines the asteroid, ionizes it, and accelerates a small portion of it to near the speed of light as a source of propulsion, all powered by nuclear reactors, or better yet, a matter-antimatter reactor. StuRat (talk) 04:15, 22 May 2010 (UTC)

If you test that device at home, you'll need a user manual. Cuddlyable3 (talk) 22:42, 22 May 2010 (UTC)

Car Mechanics...... power steering

Hi evry one ... my car power steering system breaks down .... so i tried to find out how it works , i googled it , to find this ... that the system use a pump attached to the engine (use engine power to compress hydrulic oil) in the system to maximize your hand power and make it easier to rotate the car .... so while searching i found that the oil pump compress the system faster at higher rpms (revolve per minute) .... which leads to more sensitive steering at higher speeds ... should'nt it be the other way around ...? as a safty measure the steering should have a slower response at higher speeds ...? --Mjaafreh2008 (talk) 21:47, 21 May 2010 (UTC)

Did you read in the article Power steering this: "...at high engine speeds the steering would naturally operate faster than at low engine speeds. Because this would be undesirable, a restricting orifice and flow control valve are used to direct some of the pump's output back to the hydraulic reservoir at high engine speeds." ? Cuddlyable3 (talk) 22:19, 21 May 2010 (UTC)

I don't know that it's done intentionally, higher oil pressure is a necessary side-effect of more RPMs (ergo more mechanical and thermal stress). I don't think increasing oil pressure would increase steering sensitivity, but I do think it would increase the power that goes into turning the wheels, which is better used at high speeds than at low speeds - as speed increases, so does momentum, which means changing the direction of the car requires a heck of a lot more force. I can safely drive at 20mph to the corner market lot with no power steering at all, I just have to put some muscle into turning it. But I don't want to imagine what happens if I drove unpowered at 75mph on the highway; I've done it, but at great risk - if something happened at that speed (blowout, shenanigans with other cars, etc) a gorilla couldn't control that wheel, let alone me. ZigSaw 12:14, 24 May 2010 (UTC)

May 22

If Earth was great big ball of magnetism

If the earth was magically replaced with a new earth made totally from a strong magnetic material like neodymium what sort of impact would that have on the solar system? I know that gravity is really weak compared to the other forces so i'm just curious would an earth of neodymium pull other planets towards it? Would it have any effect on the sun? Mike --87.112.183.70 (talk) 01:17, 22 May 2010 (UTC)

I don't think so -- at the sorts of interplanetary distances involved, the gravitational force would still be much more of a factor than the magnetic force. Keep in mind, too, that the other planets would still be non-magnetic. FWiW 67.170.215.166 (talk) 05:17, 22 May 2010 (UTC)

This is a terrific question that I know will have several people puzzling. I can't speak much to the change in Earth's natural magnetic field at all - I will defer to someone who knows more about it - and I'm not sure how the polarity is set up in those Nd magnets. That said, most planets have natural magnetic fields, and if the field lines from two bodies reinforce each other, they will attract according to the cube of the distance from each other. This tapers off much more quickly than gravity, but even if it didn't, Earth's field may be strong but even Jupiter's, the strongest in the solar system, is relatively weak and will likely not result in much orbital disturbance.

It takes two good fields to magnetically tango. When magnets pick up pieces of metal like paperclips they do it by inducing a temporary field in the paperclip, because the iron in a paperclip is something that can quickly align as a magnet and then fall back out of it, depending on what other fields are in the environment (so it can attract itself to either pole of a magnet by rearranging itself, for example). A planet is not made out of this "ferromagnetic material". Most of them have heavy cores of iron or nickel, but those are far too high temperature to hold an attractive arrangement together to attract itself to the Nd Earth. However, Nd magnets are strong enough to induce magnetic fields in even non-ferromagnetic materials, even humans, and thus can make for neat household tricks (try dropping one down an iron tube).

In conclusion, I don't think this giant Nd Earth will have much direct effect on other planets, though someone will probably prove me wrong. SamuelRiv (talk) 05:24, 22 May 2010 (UTC)

I think that the neat trick you're thinking of involves dropping a strong magnet down a copper tube. The magnet will simply stick to an iron tube. APL (talk) 07:42, 22 May 2010 (UTC)

Now you've got me curious. What happens? Vimescarrot (talk) 07:57, 22 May 2010 (UTC)

assuming you've not already google'd it - here's a youtube video of what happens. (http://www.youtube.com/watch?v=30oPZO_z7-4) ny156uk (talk) 09:13, 22 May 2010 (UTC)

Nifty! Vimescarrot (talk) 15:27, 22 May 2010 (UTC)

This super magnetic earth will have an impact on solar wind it will probably drag all the solar wind nearby and accelerate it to the magnetic pole. It might also attract iron asteroids - especially if given enough time. I think the first order of business is calculating just how strong the magnet would be. Ariel. (talk) 02:11, 23 May 2010 (UTC) well u see magnet can attract only magnetic substances around itself. grationational pull of earth could be the reason of its magnetic effect but not the only one . gravitational force is effective between masses, gravitones are smallest particle exchange which goes on between the masses. if earth would be a giant magnetic ball then its shape and size will deform itself under many time period(permanent magnet is always in shape of a bar). their are few forces we know so we can think of it but many more types of orce do exist whose effect we don't know.......for more questions mail me to champgamy@gmail.com

rust forceps

i bough some German stainless steel Surgical OCHSNER Forceps. i put them on my sink counter. a few weeks later a small amount of rust appeared. hows that possible. —Preceding unsigned comment added by Tom12350 (talk • contribs) 04:57, 22 May 2010 (UTC)

What's your sink counter made of? If could the rust have come from that and not the forceps? This used as a source in stainless steel only says that stainless steel rusts less easily than normal steel. I'm no chemist though, hopefully someone can explain in more detail. 131.111.30.21 (talk) 08:59, 22 May 2010 (UTC)

Stainless steel is very resistant to oxidation by oxygen gas, where it forms a thin protective layer of chromium(III) oxide. If there is acid, the coating dissolves, starting the corrosion (although the rust dissolves too). If there is strong alkali, the coating dissolves, and some rust forms which is insoluble in alkali (iron is not amphoteric). But you shouldn't have strong acids and alkalis on your sink. --Chemicalinterest (talk) 10:51, 22 May 2010 (UTC)

[5] [6] Rust spots on stainless steel happen, for a variety of reasons.77.86.62.107 (talk) 14:51, 22 May 2010 (UTC)

Weather recce

What's an aerometeorograph, and what atmospheric parameters does it measure? 67.170.215.166 (talk) 06:06, 22 May 2010 (UTC)

From here "A self-recording instrument used on aircraft for the simultaneous recording of atmospheric pressure, temperature, and humidity." APL (talk) 07:30, 22 May 2010 (UTC)

Cool, three essential parameters measured with one instrument! Now, does anyone happen to know its typical weight and size, and also whether it's a self-contained instrument or whether it has to be hooked up to the plane's static port or OAT gauge? Thanks for the info! 67.170.215.166 (talk) 02:53, 23 May 2010 (UTC)

Update: Just looked up some pictures of modern units, they're quite small (about the size of your typical battery-powered portable emergency radio). So no problem about the size; the only thing I need to know is, is it self-contained or does it hook up to the plane's instrument systems? 67.170.215.166 (talk) 07:17, 23 May 2010 (UTC)

Can the acoustic guitar hurt your hearing?

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the talk page discussion (if a link has been provided). --TenOfAllTrades(talk) 13:40, 22 May 2010 (UTC)

TenOfAllTrades(talk) 13:40, 22 May 2010 (UTC)

Too fast to be an Iridium flare... so what was it?

I sat beneath the stars tonight for about an hour. I no longer have a grasp of the night sky, so all I can say is I was facing southwest (the Big Dipper was behind me somewhat). At one point, I saw what looked like a camera flash go off, but it was a pinpoint of light. It was extremely quick, no "few seconds" or "trail" that the Satellite flare article talked about. Then I noticed something peculiar... I kept staring at that spot and there was a second, almost imperceptible flash, just a hair to the left of the original flash. Huh! Anyway, time goes on and I'm staring to the northwest, closer to the Big Dipper, and again, there is a microburst of light way up in the heavens. This time I stared and stared, hoping to corroborate the secondary flash, and sure enough, after a few seconds, and just a fraction of some unknown stellar distance from the original flash was a second "pop" of light... What's up there, and is it rotating? I've seen dozens of "normal" satellites that are a constant reflection, a dot moving slowly across the night sky. I've never seen this before in my life. Any ideas? SR-71 taking pictures of me? :D – Kerαunoςcopia^◁_galaxies 09:17, 22 May 2010 (UTC)

It might be an airplane doing combat manuevers in the air. It also could be a meteor. Firecrackers? --Chemicalinterest (talk) 11:06, 22 May 2010 (UTC)

Without having seen it, it's hard to say for certain. It's also worth remembering that one's eyes can play tricks under low-light conditions. (For example, the second 'flash' might be just some sort of afterimage that you're seeing just because you're looking very hard for it. As well, to dark-adjusted eyes an object doesn't have to be particularly bright for it to look quite bright.) A couple of guesses: a meteor following a trail aimed almost directly at you, so that it didn't appear to move appreciably as it rapidly brightened and then disappeared. If the rock happened to break into more than one fragment, you might see a second flash. Another explanation could be tumbling space debris — the solar panels on a retired or 'lost' satellite, etc. That reflection would tend to have a much faster 'rise time' than an Iridium flare, and you might get a second flash as the satellite tumbled around. TenOfAllTrades(talk) 13:12, 22 May 2010 (UTC)

A fundamental problem we have here is not knowing how high was the artefact that caused the brief flashes. It could indeed be something as simple as a plane at altitude and you caught a solar reflection, you don't say how long after sunset this occurred. However the fact that it happened again in a different part of the sky makes me believe that it was some sort of image created by your eye or optic system. There are several non-pathological causes for the effect of "seeing stars" in a medical sense and I am not inferring that you have a medical condition that requires attention, I suggest this may be a possible reason for seeing microflashes of light. Richard Avery (talk) 14:59, 22 May 2010 (UTC)

It could easily be a satellite flare, just not an iridium reflection. There are other objects tumbling rapidly that could give a flash. If it is short you wont see a trail. Graeme Bartlett (talk) 22:09, 22 May 2010 (UTC)

Could it be a plane's anti-collision strobe lights? Many civilian planes have them, and they make bright white flashes every couple seconds. And if the plane was at high altitude (like an airliner at 30000 feet), then you can see the flashes but not hear the engine noise. FWiW 67.170.215.166 (talk) 02:58, 23 May 2010 (UTC)

If you remember the exact time, check the Heavens-above website. Count Iblis (talk) 16:56, 23 May 2010 (UTC)

Thanks, all. It wasn't an eye problem, it couldn't have been an airplane because I was watching for that, and beside, the night was absolutely crystal clear pitch black loaded with stars, and nothing was moving up there, and thanks for the Heavens Above website, but unfortunately I have no clue what time it was. Anywhere between 4 and 5 in the morning, but i have no watch. – Kerαunoςcopia^◁_galaxies 19:20, 23 May 2010 (UTC)

How many carbon black add in polypropelene polymers from protection SUN LIGHT

Dear, Plese, find answer headline and give me reply. thanks, Mr. jatin —Preceding unsigned comment added by Mjhirpara (talk • contribs) 12:14, 22 May 2010 (UTC)

More carbon black produces increased uv resistance.

This product [7] uses 3% carbon black.77.86.62.107 (talk) 15:03, 22 May 2010 (UTC)

See this book [8]77.86.62.107 (talk) 15:06, 22 May 2010 (UTC)

Iodine oxidation

Is sodium hypochlorite strong enough to oxidize elemental iodine (in its dilute state as household bleach)? --Chemicalinterest (talk) 12:19, 22 May 2010 (UTC)

Look up the reduction potentials for Cl⁺¹ → Cl⁰ or Cl^–1 compared to I⁰ → I⁺¹ to see which is stronger/able to oxidize or reduce which when you have these two redox half-reactions balanced. DMacks (talk) 15:06, 22 May 2010 (UTC)

There's a number of issues with this reaction:

• hypochlorite solutions are strongly basic - so the standard electrode potentials will need converting, or may not be applicable
  • particularily : Iodine disproportionates in alkaline solution to iodide and iodate
• Additionally Iodine reacts with chloride to form I₂Cl- and other reactions.

There's some more detail on iodine redox here [9] 77.86.62.107 , the chlorine potentials are also in this book a few pages before. (talk) 15:24, 22 May 2010 (UTC)

I never find the reduction potential for OCl^- + H₂O + 2 e^- → Cl^- + 2 OH^-; only see it for reduction to Cl₂. The iodide probably will be oxidized by NaClO when it is formed. --Chemicalinterest (talk) 17:04, 22 May 2010 (UTC)

It's in the above link, page 74 section C E=0.890V (in basic solution - not at [H+] = 1mol/dm3)

Probably the reason why it's never found as a standard E is that ClO- is unstable under standard (ie acidic) electrode conditions.87.102.18.191 (talk) 17:11, 22 May 2010 (UTC)

FWIW, "put a drop of solution on starch/iodide paper" is a standard test my students use for presence of hypochlorite in solution; turns dark if there is oxidizer available. See starch indicator and iodine test for some backround on what this might mean chemically. DMacks (talk) 18:55, 22 May 2010 (UTC)

Wembley Stadium grass - too dark?

Are the problems with the Wembley Stadium pitch simply due to the fact that the design of the stadium (high walls, roof) means that the grass does not get enough sunlight to grow properly? 92.28.248.33 (talk) 13:06, 22 May 2010 (UTC)

It seems unlikely, grass doesn't require a particularly high level of photosynthetically active radiation to grow. In fact at my house, the grass grows longer in the shade since there is more water available due to less evaporation. I'm not familiar with stadiums but I can't believe that Wembley is particularly different to any others and you'd think that they would have thought about it during the design stage. Reading this it sounds like it is more of a problem with it not being laid long enough before a game is played for a strong mat of roots to grow and form a good surface. 131.111.30.21 (talk) 16:33, 22 May 2010 (UTC)

The roof of Wembley was specifically designed to maximise the sunlight on the pitch, for the grass - that's why it's retractable. Vimescarrot (talk) 17:46, 22 May 2010 (UTC)

The stadium is in London, which is on the same latitude as Newfoundland, so it would not get as much intensity of sunlight as similar designs of stadium would in most parts of the United States for example. The grass is also 4 metres lower than it used to be, and the old design was less raked and roofless as far as I recall. 92.15.9.117 (talk) 18:04, 22 May 2010 (UTC)

dimple above penis

I have noticed that some men have a slight dimple just above the spot where the penis meets the pubis (this is normally only apparent if the pubic hair is shaved). Is this a medically recognised anatomical feature, and if so, what is it's name? Little radiolarian (talk) 13:14, 22 May 2010 (UTC)

Do you mean Apollo's belt? --Jayron32 04:25, 23 May 2010 (UTC)

Jayron -- I think he refers to the dimple in the midsagittal plane. It's a space between muscles that doesn't provide the support for the skin in that region as seen in the immediately surrounding areas -- anatomically, the space will fall in the midsagittal plane and will correspond to the skin and fatty tissue superficial to the suspensory ligament of the penis, just inferior to the pubic symphysis. DRosenbach ^{(Talk | Contribs)} 04:30, 23 May 2010 (UTC)

That certainly sounds like the same spot I'm describing. Would it be correct to describe this dimple as a surface feature of the pubic symphysis? If not, how would you refer to it (on the rare occasions one might have reason to)? Little radiolarian (talk) 15:25, 23 May 2010 (UTC)

I dreamt about this question last night, graphic imagery and all. Didn't even remember until I was passing through this question. – Kerαunoςcopia^◁_galaxies 19:16, 23 May 2010 (UTC)

According to the anatomy text I'm using (Moore), the pubic symphysis is too inferior to palpate -- probably because of both a low position and the erectile tissue being too massive to poke through. DRosenbach ^{(Talk | Contribs)} 01:28, 24 May 2010 (UTC)

The origin of life!!!!!!

I want to know how it was successfully verified that life on earth has arisen from complex molecules such as methane and oxygen was not present during the initial formation of life on earth? —Preceding unsigned comment added by Hitarth21 (talk • contribs) 14:58, 22 May 2010 (UTC)

Hi, your sentence is very confusing, can you rewrite it? Thanks. Beach drifter (talk) 15:00, 22 May 2010 (UTC)

Our knowledge and understanding of abiogenesis is very limited. There are some educated guesses about how it might have happened (see that article for details), but we don't really know. --Tango (talk) 15:50, 22 May 2010 (UTC)

TWO SCIENTIST DID AN EXPERIMENT: they took a round bottom flask, put two electrodes in it,filled it half with water, and put some rare gasses in same proportion they thought would have been present at the time of origin. they kept this setup for weeks at 100degree Celsius. electrodes are used for sparking mimicking lightning. and after weeks lo and behold1 TYHEY found key compounds needed to let life exist. THIS EXPERIMENT WAS CALLED MILLER'S EXPERIMENT ON THE NAME OF ONE OF THE GEEK. GOOGLE IT --Myownid420 (talk) 15:53, 22 May 2010 (UTC)

You're thinking of the Miller-Urey experiment. It was an important step in thinking about how life came about, though people today realize that the actual composition that they used probably wasn't very representative of Earth's early atmosphere. However, similar experiments have been done using other compositions, sometimes with interesting results. Buddy431 (talk) 16:23, 22 May 2010 (UTC)

Here are some of the problems with your original post:

1) Methane and oxygen aren't complex molecules, they are simple molecules (CH₄ and O₂). Oxygen, of course, is also a chemical element, O, but isn't normally found as a single atom.

2) The "complex molecules" you were probably thinking of are amino acids, the building blocks of proteins.

3) Then when you ask about whether scientists "verified that life on earth has arisen" from this process, you must realize that scientist can only propose a hypothesis that this is how it happened, as there's no fossil record of the original life forms. StuRat (talk) 16:30, 22 May 2010 (UTC)

The initial stages of the origin of life are still not clearly understood. To me it seems most likely that deep ocean vents are where the action took place. Regardless of that, there is very strong evidence that significant oxygen levels didn't show up until about a billion years ago -- the rocks that formed at the surface prior to that are not oxidized as they would be if high levels of oxygen had been present. Looie496 (talk) 16:52, 22 May 2010 (UTC)

AFAIK it is considered that oxygen was likely poisonous to early life. Vespine (talk) 22:55, 23 May 2010 (UTC)

Germ cell tumor

Whats the prognosis of a metastatic germ cell tumor —Preceding unsigned comment added by 24.97.164.250 (talk) 15:13, 22 May 2010 (UTC)

I assume you've read "Germ cell tumor#Prognosis"? Remember that Wikipedia does not give medical advice (see WP:MEDICAL). Gabbe (talk) 17:10, 22 May 2010 (UTC)

planets coming in align

in how many years does all planets come in one line. is it even possible or not? When they will align, will not it anyhow efffect Earth's life? if so then how.

<IN MY CLASS TEST ONCE I MADE ALL THE PLANETS IN ONE LINE AND MY TEACHER ASKED ME "WHAT IS THE PROBABILITY OF THIS". I SAID "MAY NOT IN COMING THOUSANDS OF LIGHT YEARS BUT SOME DAY IT WILL HAPPEN". I WANNA KNOW I WAS CORRECT OR NOT>

See Syzygy. How often it happens depends on how precisely you want them to line up. If you're happy with them just being in the same quadrant (ie. a 90 degree wide sector) then it will happen far more often than if you require them to be within a 1 degree sector, say. As for what effect it would have - none at all. About 70% of the combined mass of the planets is Jupiter, so all the planets acting together couldn't do anything significantly more than Jupiter can do on its own, which isn't much (as far as the Earth is concerned). --Tango (talk) 15:57, 22 May 2010 (UTC)

And when you consider the relative gravitational influence of solar system bodies on the Earth, you stop caring after the moon and the sun. Jupiter isn't even the most influential planet (it's 1/10th the effect of Venus), but none of them are meaningfully relevant. — Lomn 19:44, 22 May 2010 (UTC)

Ah, yes, I forgot it's tidal forces, not direct gravitational forces, that matter, so we need the cube of distance not the square. I believe Jupiter has the largest gravitational force out of the planets on Earth, just not the largest tidal force. Thanks for the link! --Tango (talk) 21:25, 22 May 2010 (UTC)

And a light-year is a unit of length, not of time. --Магьосник (talk) 16:37, 22 May 2010 (UTC)

Isn't there a particular name for this phenomenon?--Myownid420 (talk) 02:18, 23 May 2010 (UTC)

If you count Pluto as a planet, Neptune and Pluto "align" every 492 years ("align" = conjoin in geocentric celestial longitude -- it would be better to be heliocentric, but this is just for illustration). Uranus and Pluto align every 115 and 165 years, alternating. Uranus and Neptune align every 171 years. Saturn and Uranus align every 45 years. Saturn and Pluto align every 30-plus years, as do Saturn and Neptune. Jupiter and Saturn align every 29 years. And so on. Given that the solar system has been and will be around for billions of years, it's likely that at some point all nine planets will be within one degree of each other in heliocentric "longitude" because the product of all the periods is probably much less than several billion years. However, if you want alignment to within one arc-second, it seems unliekly that even the products of the periods will realistically indicate an exact nine-planet alignment, though I don't know the math for this. Anyone else? 63.17.50.130 (talk) 02:43, 23 May 2010 (UTC)

This data is based on short term observations. The solar system is basically an n-body problem; in the short term it can be predictable, but in the long term it becomes highly chaotic. So, we can pretty easily predict how often two bodies will be in line with the sun; but once we start waiting for three and four and five bodies to align in such a way, the time frame becomes long enough between occurances that chaotic effects take over and it literally becomes impossible to predict. --Jayron32 04:22, 23 May 2010 (UTC)

This happened about 5 years ago, all the red top papers in the UK were predicting workd disaster...nothing happened, just a normal day at the office. therefore, it does happen, rarely, but is of no significance to anyone. —Preceding unsigned comment added by 62.172.58.82 (talk) 14:24, 24 May 2010 (UTC)

I don't think anyone here would be happy to accept as evidence of multiple planet alignment, the word of red-top newspapers. --Tagishsimon (talk) 14:30, 24 May 2010 (UTC)

Solid phase extraction and Chromatography

Hi, I have just read both Solid phase extraction and Chromatography pages but I haven’t found the difference between techniques. I mean, they do the same thing and exploit the same principle or not? Thanks so much in advance, I ‘m studying Forensic pathology for next month exam.--151.53.91.218 (talk) 16:51, 22 May 2010 (UTC)

SPE deals with making the desired analyte specifically soluble/extracted or insoluble/stuck-to-solid-phase, the other starts and ends with the desired analyte in solution merely passed through. The key to SPE is where that article states "either the desired analytes of interest or undesired impurities in the sample are retained on the stationary phase" (emphasis mine) as opposed to the more general idea of chromatography "passing a mixture [...] through a stationary phase, [...] Subtle differences in a compound's partition coefficient result in differential retention on the stationary phase". Differential retention causes elution time to vary vs "retained or not-retained". DMacks (talk) 18:50, 22 May 2010 (UTC)

updates based on scientific fact

Shrimp are bottom feeders meaning their diet may include toxic substances including radioactive particles. However, since 1970 shrimp have been farmed in non-toxic environments. Consequently do any of the religions which in the past have excluded them from the diet now permit such non-toxic shrimp to be labeled "Kosher"? 71.100.3.228 (talk) 19:53, 22 May 2010 (UTC)

Toxins possibly being present in food has nothing to do with the food being or not being Kosher. Beach drifter (talk) 20:00, 22 May 2010 (UTC)

I think the toxin example is a bad one because it presumes to know the intent of the law, which would not sit with a religious person terribly well. (It assumes they have secular goals behind them; that is how an outsider views such things, not an insider.) But there are modern updates to things like kosher laws—for example, there is an entire industry of appliances designed to conform with Sabbath strictures as they are interpreted to apply to modern technology. See: Sabbath mode. In Judaism, there are rabbis who get together and debate whether or not, say, flicking a switch violates the strictures against "work", or whether setting an oven to heat up violates strictures against lighting a fire, and so on. --Mr.98 (talk) 20:52, 22 May 2010 (UTC)

To elaborate on Mr.98's concise post above, the laws of Judaism are immutable and the biblical violation of eating seafood that does not possess both fins and (easily scrape-off-able) scales (Leviticus 11:9) does not hinge on the toxicity or other physical uncleanliness of these organisms. DRosenbach ^{(Talk | Contribs)} 04:37, 23 May 2010 (UTC)

Okay then I'm really stumped here trying to explain why in this modern day why such ancient rules are not arbitrary but rather mandatory, unless they are intended to be arbitrary so they can serve more as test of obedience rather than anything else. If that is THE CASE and its just a matter of proving loyalty through compliance rather than compliance serving a practical purpose then not updating such laws makes more sense. 71.100.3.228 (talk) 07:54, 23 May 2010 (UTC)

"Why a religion has a certain rule" is not a scientific question. DMacks (talk) 08:13, 23 May 2010 (UTC)

Then what in your opinion is the purpose for a religion having rules? 71.100.3.228 (talk) 20:04, 23 May 2010 (UTC)

In any case, much of Judaism in particular is about doing what the law says even though you don't understand it. It is not and does not claim to be scientific. If you'd like a humorous send-up of Orthodox Jewish thought, which nonetheless gives a great (and entertaining) primer as to the logic behind it, I highly recommend Shalom Auslander's hilarious Foreskin's Lament: A Memoir. The basic philosophy is that you do what God says because God says to do it. As for whether the origin of the laws are based in some kind of secular purpose, well, there's been a lot of speculation about that, and that would be interesting for the anthropologist, but it would not be relevant to anyone practicing the religion. And I will note that my very reform cousins did not keep kosher at all, even at their bar mitzvahs and things like that (they served Hawaiian pizza, if you can believe it). There are multiple strains of thought within any religious heading. (I write all this as a nonreligious person myself, so if I offend anyone or have grossly caricatured a complicated thing, I apologize ahead of time.) --Mr.98 (talk) 12:53, 23 May 2010 (UTC)

What comes to mind are certain religious real world physical "journeys" in which the individual believer marks out the entire journey with a prone position to show devotion to its head. In any practical sense walking would be an update or flying in a plane but since the purpose is to show devotion to the religion's head by lying prone the entire length of the journey and walking or flying would not show this level of devotion they must be ruled out. From this perspective then I can see why religious rules would not be subject to update. 71.100.3.228 (talk) 20:12, 23 May 2010 (UTC)

Religious rules are subject to update - just, usually, not for scientific reason. Christianity is Judaism 2.0 (well, actually, a bag from 2.0 to 4.5 with plenty of mutually incompatible patches ;-) and Islam is essentially a merger of both rewritten from scratch. Looking at the early history of Christianity (which essentially started out as a jewish sect) shows significant debate of which laws apply to jewish Christians, and to gentile Christians. The laws given to Noah (don't kill, don't eat blood) were deemed to apply to all Christians (although the first has been very much rationalised away, and the second largely forgotten by now), but the Kashrut and circumcision were on the table for a while, too (with Paul being one of the strongest opponents of applying them to gentiles). --Stephan Schulz (talk) 20:46, 23 May 2010 (UTC)

Thanks for the Kashrut link. I have a friend who is developing meals that comply with individual diet plans which are based on varying amounts of commonly available foods which Kashrut will help guide. For instance, farmed shrimp was on the list until now. It would be nice in some cases though if the rules were updated to include farmed shrimp. 71.100.3.228 (talk) 20:59, 23 May 2010 (UTC)

(outdent) Religious observance is one of those things that really doesn't take kindly to an outsider trying to find technicalities or adjustments in how to apply or accommodate them. If you're trying to be polite and make certain populations feel welcome, you definitely take them on their own terms, however obsolete, confusing, nit-picky, or technicality/confusing-to-you they might seem. In fact, one of the tenets of Judaism and "follow its laws" I often hear is that you shouldn't try to find loopholes to excuse why you don't want to follow an observance (the flip side being whole movements that have taken a coherent look at deciding what observances are appropriate for modern-day). Or in a milder form, better to play it safe than to accidentally actually violate a law while trying to just tread close to the edge. Really, if you're trying to host an event where keeping kosher (to some level) matters (for some guests) ask them what they feel comfortable with. There's strictly kosher, who wouldn't even eat off your dishware and wouldn't drive to your venue on Saturday, there's "pretty kosher" who would be happy with a vegetarian option rather than putting you to the effort of cooking something really kosher, there's "kosher style" who would eat non-kosher beef but not a cheeseburger, etc. Just like there's vegan, lacto-ovo-vegetarian, "no red meat", etc. Actually, having a real vegetarian option (an actual entree, not just the side-salad) is a pretty good way to solve many different special diets (health, moral, religious). DMacks (talk) 21:45, 23 May 2010 (UTC)

I suppose the question arises from the use of the word "unclean" in reference to the different kinds of plant and animal that can be eaten as the basis for using a modern scientific designation of what is actually clean. Since shrimp are unclean from only what they eat it seems that if they are farm raised on only corn meal for instance that the designation of unclean simply cannot or would not apply. I'll ask the guests though from now on as the best strategy. 71.100.8.229 (talk) 03:15, 26 May 2010 (UTC)

Kashrut has nothing to do with unclean. Kashrut for animals is based on specific lists of things the animal needs to have. For a water-dweller (not just fish) it needs to have fins and scales. Shrimp doesn't. Unclean has nothing to do with it. Ariel. (talk) 11:38, 26 May 2010 (UTC)

magnetism versus temperature

what is the formula that relates and objects temperature to its magnetism? 71.100.3.228 (talk) 20:01, 22 May 2010 (UTC)

I'm not aware of one - maybe you were thinking of the Curie temperature .87.102.18.191 (talk) 20:25, 22 May 2010 (UTC)

So the state of magnetism undergoes a similar transition as state of matter phase change in which changes occur at junctures rather than continuously? 71.100.3.228 (talk) 20:49, 23 May 2010 (UTC)

Niel ?

I keep thinking I've heard of a "Niel temperature" - but search shows nothing. (Not Niels Bohr - I think it was a surname)

Is there a similarly name temperature or point - I'm sure it was a transition or phase change temperature.87.102.18.191 (talk) 20:27, 22 May 2010 (UTC)

Annealing temperature? --BozMo talk 20:34, 22 May 2010 (UTC)

:) (no) 87.102.18.191 (talk) 21:20, 22 May 2010 (UTC)

The Néel temperature is the temperature above which an antiferromagnetic material becomes paramagnetic. Cuddlyable3 (talk) 21:29, 22 May 2010 (UTC) Cuddlyable3 (talk) 21:29, 22 May 2010 (UTC)

Yes thanks. 87.102.18.191 (talk) 21:49, 22 May 2010 (UTC)

Resolved

What metals were thrown out by the icelandic volcano?

What heavy metals were ejected by the icelandic volcano?--92.251.177.211 (talk) 20:55, 22 May 2010 (UTC)

The material ejected by the volcano would have been basically basalt, which has metals in the form of silicates and oxides but none of the heavy metals are likely to be present other than in trace amounts, as far as I know. Mikenorton (talk) 21:26, 22 May 2010 (UTC)

Heavy metals are found in only trace amounts in basalt - but the overall effect of a volcanic eruption is to increase the levels of heavy metals in the surrounding area (in general) http://www.google.co.uk/search?hl=en&q=volcano+heavy+metal+emmision&meta=

In norway no effect had been noticed expected in this report http://www.niva.no/symfoni/infoportal/publikasjon.nsf/.vieEngInterForsideNIVA/1135331028BA9759C125770E00278CE0?OpenDocument&Category=&m1=News

[10] people are measuring this, but as far as I can tell the results aren't readily available as yet.87.102.18.191 (talk) 13:21, 23 May 2010 (UTC)

Is there any animal that can 'emit' fire?

Years and years ago I saw a wildlife documentary that featured a rainforest insect of some kind which (IIRC) as a defence mechanism was able to squirt a stream of *something* from its hindquarters which then spontaneously ignited in contact with the air, producing a small jet of flame. For some reason, I ended up discussing this with someone today, who insisted that I was wrong and asserted that there is no such and never has been any such creature. I'm open to the possibility that my memory is playing tricks on me and that I've mixed up something like a bombardier beetle (I looked that up first, thinking that it may have been what I was remembering) with Pokemon, or dragons - or that I saw it in a dream, or whatever.

So, does anyone know if there really is a bug, or anything else out there that can do this? --Kurt Shaped Box (talk) 21:05, 22 May 2010 (UTC)

I think you're just thinking of the bombardier beetle. There are no fire-breathing anything (other than people). --Mr.98 (talk) 22:07, 22 May 2010 (UTC)

Dragon —Preceding unsigned comment added by 79.76.233.61 (talk) 23:44, 22 May 2010 (UTC)

Animal, mythological creature. These are not equivalent, 79. Vranak (talk) 01:59, 23 May 2010 (UTC)

Salamanders are often associated with fire, though in reality they have very little to do with it. Buddy431 (talk) 04:12, 23 May 2010 (UTC)

It used to be thought that salamanders derive from fire, but it was later shown that they merely crawl from ground detritus when fire causes them to leave. See Slifkin's Mysterious Creatures (Targum Press 2003) ISBN 1-56871-248-0 (republished as Sacred Monsters) for a thorough review. DRosenbach ^{(Talk | Contribs)} 04:40, 23 May 2010 (UTC)

Any creature capable of setting fire to its environment would have made itself extinct by now.--Shantavira|^{feed me} 06:16, 23 May 2010 (UTC)

The conclusion being, any animal capable of emitting fire would have to live in a difficult-to-ignite environment. Vimescarrot (talk) 08:54, 23 May 2010 (UTC)

Or just be careful about what they ignite. I mean, humans are animals that are capable of setting fire to their environment. Yes, we've burnt ourselves a few times doing that, but it's hardly an evolutionary impossibility! --Mr.98 (talk) 18:49, 23 May 2010 (UTC)

Yes, but we've only been around for the blink of an eye. The (non-avian) dinosaurs still have about a factor of 1000 on us, and see where they are now. --Stephan Schulz (talk) 20:50, 23 May 2010 (UTC)

Not necessarily. Certain pines (I think Jack Pines are one), for example, need fire in order to germinate. If there isn't a periodic wildfire, they can be crowded out by other trees. (This has happened in portions of the western U.S., where there has been a "suppress all wildfires" policy for several decades.) Right now they require externally initiated fires, but one could easily imagine a hypothetical situation where a pine recognizes that it's being crowded by other species, so produces copious amounts of (fire-resistant) seeds, and then sets fire to the forest. Other species will be pushed out, and the seedlings now have ash-enriched soil to grow in. This might allow them to spread to wetter climates, where wildfires are not as wide ranging. -- 174.24.200.38 (talk) 17:48, 23 May 2010 (UTC)

A 2005 forum post [11] says: "There was an article a year or two ago in the NY Times, from a number of scientists who said that a fire-breathing animal was biologically possible." I haven't found the article. PrimeHunter (talk) 00:25, 24 May 2010 (UTC)

You're not thinking of fireflies, are you? (I wish I was a firefly I never would be glum Cos how could you be gloomy When the sun shines from your bum?)--TammyMoet (talk) 09:14, 23 May 2010 (UTC)

How about Bombardier beetle? RJFJR (talk) 17:42, 24 May 2010 (UTC)

The OP already mentioned the Bombardier beetle. --Tango (talk) 18:00, 24 May 2010 (UTC)

Black hole paradox

After watching an explanation of the black hole paradox from Leonard Susskind, the explanation made first at sense, but further thought has left me only more confused. First, a quick explanation of the paradox:

• When person 1 watching person 2 enter into a black hole, person 2 appears to freeze, and time for him stops due to the gravity. Person 2 will never progress beyond the event horizon from person 1's view.
• Time, however, does not stop for person 2; from his perspective, he will sail right past the event horizon.
• Point 1 appears to conflict with point 2. Thus anything done by person 2 inside of the horizon will be irretrievably lost to the outside world - this shouldn't happen though. Physics says that, in theory, person 1, with a perfect view of what's occurring, should be able to reconstruct person 2's past perfectly.
• The solution, as explain by Susskind and apparently mostly accepted by physicists, is that the information is stored on the surface of the event horizon, an unfathomably hot place where matter is squished into a two-dimensional (or essentially two-dimensional) plane.

What I don't understand is this:

1. For person 2, time on the outside world should go faster and faster. Right before reaching the event horizon, the world will speed up to infinite time. What then to make of what person 2 observes after passing the even horizon? (this situation, by the way, is far from just theoretical: the spaghettification on a smaller sized black hole apparently won't occur on supermassive black holes).
2. What of the matter towards the center of the collapsing star that becomes a black hole? That matter has no way of being "stuck" on the event horizon and as such wouldn't be visible as the event horizon slowly evaporates.
3. What happens to matter immediately inside the event horizon upon collapse? The gravity there would insist on a field faster than the speed of light. This seems to violate the laws of nature.

Magog the Ogre (talk) 21:25, 22 May 2010 (UTC)

I'm not sure what the problem is in your first question. Somebody falling into a black hole will see the outside world sped up (and massively distorted) and will observe things happening billions of years after they crossed the line in the few hours (at most) they can survive before being ripped apart, that's just the way it is. For your other questions, I don't think the problem exists since the collapse will happen from the inside out. The centre of the star will be the densest bit, so will become a black hole first and the rest of the star will fall into it. The event horizon will start out with very tiny diameter (you probably need a theory of quantum gravity to describe that bit) and grow. Your questions seems to be based on the assumption that the event horizon forms instantly at its final size, which isn't the case. --Tango (talk) 02:23, 23 May 2010 (UTC)

1. Remember that person 2 can only see what happens in his past light cone which will not include a infinite amount of the time of person 1
2. Tango answered question 2 pretty well above.
3. I'm not sure I understand your question, but be asured that any local observer (that is person 2) doesn't see any object passing by at a speed higher than the speed of light and light always is observed to move at the speed of light. He will, for instance, observe light rays moving outwards at the speed of light.

Dauto (talk) 02:45, 23 May 2010 (UTC)

Your bullet-point summary of the information paradox isn't really correct. "Losing" information behind an event horizon isn't a problem, because you can just say the information is on the other side of the horizon. Any surface that moves towards you at the speed of light behaves as an event horizon if you never cross it, including the unbounded redshift of objects falling through, the "gravitational" attraction, and even the Hawking radiation (though it's called Unruh radiation instead of Hawking radiation in some contexts). This is true even if you're out in the middle of nowhere and the "surface" is one that you just invented with no physical meaning whatsoever. Rindler coordinates has more information about this.

The problem with black holes is that they apparently can disappear completely by Hawking radiation, leaving nowhere for the lost information to go. People have proposed various unsatisfactory solutions to this, which you can find at black hole information loss paradox. The idea that infalling objects get "squished onto the event horizon" and then leave as Hawking radiation is the one called "Information gradually leaks out during the black-hole evaporation" in the article. The problem is that there's nothing physically special about event horizons, as I said above. You can define an event horizon anywhere, so the "new" physics should show up everywhere, unless you throw away the equivalence principle.

Susskind wants to solve this by having the "new" physics (where you turn into Hawking radiation) actually be mathematically equivalent to the ordinary physics (where you just fall through the horizon and nothing special happens to you). This sounds completely crazy, but there actually is a lot of circumstantial evidence for an equivalence ("duality") like this, and it's appealing because whereas the other solutions all break some nice physical symmetry (like unitarity or the equivalence principle) this one introduces a new physical symmetry, while preserving all the old ones.

I don't know why Susskind says that all physicists agree with him on this. Only a small number of physicists are interested in black hole information loss in the first place, and I've never had the impression that they agreed about much. I guess everybody now agrees that unitary is preserved (Hawking was the holdout, but changed his mind a few years ago). -- BenRG (talk) 21:44, 24 May 2010 (UTC)

May 23

Spider behaviour

In our shared house for university we have a dead spider that's been encased in some sort of plastic or wax near the ceiling for at least a year (before we moved in, damned if I'm gonna clean it!).

Today I've seen a big, similar sized spider climb up towards the dead spider about a day ago and it seems to be staying there up until this point of writing. It looks to be moving whilst up there too, and looks relatively healthy so I don't think it's dying.

That said, what would cause this sort of clinging behaviour to a dead, very-different-to-how-it-would-have-been-a-year-ago spider? Do spiders try to rescue their kind? Do they go off to die in similar places, or hang around with their dead counterparts? Is this just a coincidence and it might move in a couple of hours? Cheers!

Regards, --—Cyclonenim | Chat  02:32, 23 May 2010 (UTC)

You're presuming incorrectly that the source of the spider's attraction to that spot is the dead spider. Its attraction is to a good place to hang out; it would have no interest in the dead spider, but rather to that part of the ceiling itself. 63.17.50.130 (talk) 02:52, 23 May 2010 (UTC)

It certainly could move in a couple of hours, maybe to someplace you wouldn't like. If you want to dispose of it, try extending your vacuum cleaner's hose attachment, and the critter's last thought will be about how life sucks. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:57, 23 May 2010 (UTC)

Ha, yes maybe. Maybe it is a good place to hang out, but it's not even in a corner or somewhere remotely comfortable. It's just sitting on top of the dead spider. Regards, --—Cyclonenim | Chat  12:13, 23 May 2010 (UTC)

Would you rather live with a dead spider on your ceiling than to clean it? Dauto (talk) 03:31, 23 May 2010 (UTC)

Well it's never really been an issue, I guess it's hard to not sound disgusting unless you've actually seen where we're living. The place is an absolute shit hole as it is, a little dead, encased-in-wax spider from the previous occupiers isn't really going to bother me. Regards, --—Cyclonenim | Chat  12:13, 23 May 2010 (UTC)

How Spiders Work Count Iblis (talk) 16:42, 23 May 2010 (UTC)

Aircraft repairs, part 2

If the same saboteur as cut the generator wires also puts emery powder into the propeller pitch-change mechanism, could the damage be repaired by replacement/repair of parts and subsequent regreasing, or does it require replacing the whole screw? (Assume that the screw in question is a two-bladed Hamilton-Standard Hydromatic, if that helps.) 67.170.215.166 (talk) 03:07, 23 May 2010 (UTC)

• Hmmm, the wikipedia has a legal disclaimer, medical disclaimer, isn't it time for a "life critical systems disclaimer"? Right, I know that 67.170.215.166 wrote about a fictional setting, not real hardware, but what if one day someone takes wiki-advice on this matter seriously? East of Borschov (talk) 04:59, 23 May 2010 (UTC)

This kind of work is only done by licensed aircraft mechanics, and they know enough to always refer to the manual, not the Wiki reference desk. So there's no chance of this advice being taken seriously. 67.170.215.166 (talk) 05:57, 23 May 2010 (UTC)

Speaking of which, this being a reference desk, I suggest that you might consider referring to an aircraft mechanic. If you have trouble locating one, give me the identifier of your nearest local airport and I can see if I can help. Falconus^{p t c} 14:13, 23 May 2010 (UTC)

I believe this question refers to a fictional novel the OP is writing in which a pilot needs to make some emergency repairs to his plane (in a rainstorm, if I remember correctly), as the second part of a question he posed on the Ref Desk a few days ago. Hence, "Part 2." OP, you might give us a quick recap so we're all on the same page here. AlexHOUSE (talk) 21:57, 24 May 2010 (UTC)

Well, the story is, the pilot and crew are making a flight around the world (which is a scientific mission to study climate change as well as a commemorative flight for Amelia Earhart), and they're forced down in Pakistan due to engine problems, and while getting the spare parts they get in trouble with the local mutaween for breaking sharia law and decide that they have to escape to India; but one of the mechanics happens to be racist against Americans (which is very common in Pakistan, by the way) so he sabotages the plane by cutting the generator wires and reattaching them in such a way that they would vibrate loose in flight (so that the pilot wouldn't notice until well under way) and also loosens one of the engine exhaust valves to make it drop into the cylinder and wreck the engine. Well, after reading a recent posting by Alex Mandel on the Amelia Earhart talk page, I got an idea to have the said anti-American mechanic also throw some emery powder into the propeller pitch change mechanism in the hope that the prop would get stuck in the wrong pitch and hopefully make the plane crash on takeoff. My idea is that he does that, but the crew catch the malfunction in time and fix the propeller; but this will be contingent on how long it will take (the flight can't be delayed too long because of the monsoon season arriving). So if the damage can be fixed by simply re-grinding the damaged parts and/or replacing them with brand-new parts and then regreasing the mechanism, then I'll go ahead and put it in the novel; but if it requires replacing the whole prop, then I'll have to skip it because it will take too long to repair. So what's your take on this? 67.170.215.166 (talk) 06:09, 25 May 2010 (UTC)

Stable ranges for Albedo and Emissivity of Earth

The Earth has a Global Annual Average Temperature of 14°C.
The Global Average Albedo is 0.30 and the concomitant Emissivity is 0.622.
Hence:
$T_{p}={\frac {((6.955\times 10^{8})^{2})\times (5778^{4})\times (1-0.3)}{(4\times 0.622\times 149597876600)^{2}}}={14}$
(derived from Luminosity)

So I was wondering how far that 14°C can shift and the planet still sustain some "liquid water,"
somewhere on the planet, what range is possible, and also what is range for the Albedo,
and the range for the Emissivity, for a stable habitable temperature for Earth life?
For clarity, this question is only about the Earth, as a reference point, not exo-moons.
Earth's temperature range is 60°C to -90°C, or 150 degrees.
There must be limits.
Global Annual Average Temperature Maximum: ??
Global Annual Average Temperature Minimum: ??
Minimum Albedo: ??
Minimum Emissivity: ??
Maximum Albedo: ??
Maximum Emissivity: ??
24.78.178.147 (talk) 01:30, 23 May 2010 (UTC)

I won't answer your question, but I will fix your equation.

$(T_{p}+273.15)^{4}={\frac {((6.955\times 10^{8})^{2})\times (5778^{4})\times (1-0.3)}{4\times 0.622\times (149597876600)^{2}}}=(13.78+273.15)^{4}$

T_p=13.78°C Dauto (talk) 05:48, 23 May 2010 (UTC)

Thanks, I missed that because I'm used to Excel not the code here.
((((((695500000)^2)*(5778^4)*(1-A)/(4*ε*(149597870690^2)))^0.25)-273.15) = 14.000
A=0.3
ε=0.62009
24.78.178.147 (talk) 04:42, 24 May 2010 (UTC)

Pineal gland

Is serotonin produced in the pineal gland? At present our article on this gland makes a big deal in the opening paragraph of serotonin as a product of the gland. If it's true, it's a secondary or minor function of the gland and the info needs to be moved further down. I'd rather cut it out, but need to be sure. Thank you. --Hordaland (talk) 07:14, 23 May 2010 (UTC)

I know melatonin is produced from serotonin in the pineal gland. (Melatonin in retina and in the digestive tract is a different story). Serotonin is produced from tryptophan, not sure where. --Dr Dima (talk) 08:25, 23 May 2010 (UTC)

What I mean by "not sure where" is as follows. The primary location of the serotonergic neurons in the human brain is the raphe nuclei (a part of the reticular formation) in the brainstem. What I'm not sure about is whether they produce most of their serotonin locally, or whether they "recycle" serotonin that is produced elsewhere. I'm pretty sure that serotonin is produced in the digestive tract, too. How much of it is produced in the pineal gland, how much in the raphe nuclei, and how much in the gut - I do not know. --Dr Dima (talk) 08:34, 23 May 2010 (UTC)

According to PMID 8745273, serotonin is indeed released by the pineal, although its main function there is to serve as precursor for melatonin. I believe the accepted concept is that serotonin serves as an autocrine hormone (i.e., affecting the pineal itself), rather than exerting significant effects elsewhere. Certainly the pineal, being a gland, does not send specific serotonergic projections to parts of the brain, as the Raphe nuclei do. Looie496 (talk) 16:50, 23 May 2010 (UTC)

Thank you for your answers, confirming what I suspected was the case! Meanwhile, someone else has fixed that paragraph, saving me the trouble. Hordaland (talk) 20:28, 23 May 2010 (UTC)

Intramuscular fat

I'm a bit lost here, so this could be a silly question, but I'm wondering if it's possible to sort of "target" certain types of body fat, in this case IMTG, when chosing a diet? Thinking retroactively, eating chips and french fries seems to have a larger effect on visceral fat, or at least a large effect, but is there any, healthier alternative that might have less of an effect on a certain, less desirable "unhealthy" fat types, and help to produce intramuscular fat (IMTG)? This is a bodybuilding/nutrition question! 210.254.117.185 (talk) 09:24, 23 May 2010 (UTC)

The relevant article is spot reduction, which says any kind of targeted fat loss is a myth - regrettably that article is pitifully underreferenced. -- Finlay McWalter • Talk 09:37, 23 May 2010 (UTC)

I wasn't asking about fat loss, I was asking about the increase of a certain type of fat. Even if it was related (though in reverse), IMTG and visceral fat are made by a difference process, where as the article you linked talks about the same type of fat on different parts of the body. 210.254.117.185 (talk) 10:16, 23 May 2010 (UTC)

CO2 and infrared radiation

If you double the concentration of CO₂ in a glass container, say from 0.03% to 0.06% (can't think why I chose those numbers!) what happens to the percentage of infrared radiation that will be absorbed? Does it double (i.e. it's a linear relationship) or does it only increase by say 25% (i.e. it's logarithmic). Hopefully someone has actually done an experiment to show this! 131.111.30.21 (talk) 11:07, 23 May 2010 (UTC)

The answer is given by the Beer–Lambert law - assuming that the absorbtion is linear with concentration - which I'm sure it will be. Also did you mean reflection of IR (as per global warming)?87.102.18.191 (talk) 11:22, 23 May 2010 (UTC)

So the absorption coefficient will double - this means the ratio of light passing through (before and after) will be:

e^-ax / e^-2ax = e² = 7.4 times less light after doubling the concentration.87.102.18.191 (talk) 11:32, 23 May 2010 (UTC)

Yea sorry, meant reflect. Does that change the figures above? 131.111.30.21 (talk) 12:11, 23 May 2010 (UTC)

I think so yes - will have to go and check.. (hang on)87.102.18.191 (talk) 12:33, 23 May 2010 (UTC)

Actually I think I was wrong to say that reflection of IR is the factor behind global warming.

The equations for reflected light will be those of scattering - however I'm not sure if the scattering is elastic or not - I think CO2 can reflect by Raman effect at least.

Someone else will need to answer this.87.102.18.191 (talk) 13:01, 23 May 2010 (UTC)

Clarify: That would be 7.4 times less light NOT being absorbed (ie if 93% of light was absorbed before, then 7% escapes, after doubling CO2 only 1% escapes..)87.102.18.191 (talk) 13:44, 23 May 2010 (UTC)

In the case of the atmosphere the very low concentration is already enough to absorb most of the radiation so doubling makes little difference. However temperature is not relative to zero degrees Centigrade but absolute zero at -273°C so the 'little difference' can still mean a few degrees change. Dmcq (talk) 12:38, 23 May 2010 (UTC)

Where should I start?

1. Absorption of IR by CO₂ is the cause of greenhouse effect.
2. The equation used to get the figure 7.4 is completely wrong
3. The effect of the doubling of CO₂ concentration on how much IR gets absorbed depends on how thich is the path of the light through the container. If the path is thin enough that most of the radiation does get through, then doubling the concentration does double the absorption, but if the path is so thick that most of the radiation is already getting absorbed, then doubling the concentration has little effect. Think about it. If you look up at the sky through a canopy which has just a few liefs then doubling the number of liefs does double the fraction of the sky that's is covered but if you are looking through a canopy so thick that it already covers most of the sky than doubling the number of liefs has little effect.

Dauto (talk) 03:54, 24 May 2010 (UTC)

Can you explain 2 in more detail - assuming the atmosphere stays the same thickness - as an approximation, how is the Beer-Lambert law wrong here?87.102.85.123 (talk) 11:42, 24 May 2010 (UTC)

The law is not wrong. The calculation performed is wrong. Dauto (talk) 16:36, 24 May 2010 (UTC)

I see the error - the absorption coefficient doubles (?), or in the case of the equation T=I₀e^-σlN N doubles with double concentration.

So the ratio T1/T2 =

I₀e^-σlN/I₀e^-σl2N

e^-σlN/e^-σl2N

T1/T2=e^σlN

or T2=T1e^-σlN

So if 90% of the light was originally absorbed, then after doubling the concentration, a further 90% of the remaining unabsrobed light would be absorbed, or 90% of 10% - total 99% absorbtion.

Is that right?87.102.85.123 (talk) 17:31, 24 May 2010 (UTC)

Yes. Dauto (talk) 03:22, 25 May 2010 (UTC)

No, that is wrong. For the greenhouse effect, it is not relevant how much direct transmission there is ("how much sky can I see"), but how much light is transmitted at all, including diffuse light that has already interacted with one or more leafs. The canopy is actually not too bad an analogy. Even if you cannot see the sky at all, doubling the thickness of the canopy will reduce the amount of light that reaches the ground (for any given input). --Stephan Schulz (talk) 08:13, 24 May 2010 (UTC)

Yes Schultz, you're correct. I was simplifying my description to make a point. Dauto (talk) 16:36, 24 May 2010 (UTC)

Ok that makes more sense, so it is logarithmic rather than linear? Does anyone do direct measurements of infrared reflection by the atmosphere? I.e. shine an infrared laser from somewhere like Mauna Loa Observatory to a satellite and then see how this is changing over time? 131.111.30.21 (talk) 08:49, 24 May 2010 (UTC)

IR reflection is irrelevant here. IR absorption (and re-emition) is what has to be measured. Dauto (talk) 16:36, 24 May 2010 (UTC)

Yes, overall climate sensitivity is logarithmic. In other words, doubling CO2 causes an equilibrium temperature increase of 3 degrees centigrade (roughly best current estimate, but there are fairly large error bands). Note that the earth has a lot of thermal inertia, so the effect lags the cause significantly. --Stephan Schulz (talk) 14:23, 24 May 2010 (UTC)

Sneezing during examinations

The last couple of years I've been noticing that I do a disproportionate amount of sneezing about 15 minutes into an examination, and I'm interested in why this might be. I don't suffer from hay fever, and I don't sneeze a lot generally. Could it be a reaction to the stress of exams? There's nothing to sneeze - my airway isn't blocked, for example - and once it's done I generally don't sneeze again. My other thought was a slight allergic reaction to the surroundings, but I've noticed it happening in two different examination halls. Of course, it could all be down to observation bias, or any number of other biases, but I don't think it is, and it does intrigue me, so I thought I might ask. Thanks, - Jarry1250 ^{[Humorous? Discuss.]} 13:04, 23 May 2010 (UTC)

• Was it an air-conditioned room? could be adjustment to AC or just some draft. Or, perhaps, simply adjustment to sitting (as opposed to active walking etc.). East of Borschov (talk) 13:21, 23 May 2010 (UTC)

Preparation of examination rooms often requires moving furntiture etc - maybe this produces a lot of dust?87.102.18.191 (talk) 13:45, 23 May 2010 (UTC)

Yes. Inhaling dust and sneezing are inextricably linked. I would also say, normally if a person finds themselves in a dusty room, they might open a window, or leave -- but when you're writing an exam, these are not good options ("Excuse me miss, you have to hand in your test before you leave. No you may not leave the room and then return. I can't allow that."). Unable to deal with the dust in this fashion, all they can do is keep breathing it in -- and sneezing to help keep the nasal passages clear and clean. Vranak (talk) 13:59, 23 May 2010 (UTC)

Dust seems like a good suggestion, the exam tables and whatnot must accumulate a load during the year. Previous locations may have been air-conditioned, but I'm 99% sure the place I'm sitting this years isn't (they open windows, doors, etc.) - Jarry1250 ^{[Humorous? Discuss.]} 14:29, 23 May 2010 (UTC)

At my old school they placed down canvas tarpaulins on the gymnasium floor for examinations. I'm fairly sure they got no use apart from the exams in January and June, so I suspect a lot of dust would be stirred up whenever they got moved or walked on. Always had to take an anti-histamine tablet on the day of an exam, since sniffles were a problem. Brammers (talk) 10:57, 24 May 2010 (UTC)

Why does sugar make things less sour?

So lets say you are making lemonade. Why is it that sugar makes it less sour? Does the sugar flavor overpower the sour flavor, or does it negate it? Or I should ask, would other flavors, like salt (saltiness) for example, make it less sour as well? ScienceApe (talk) 15:56, 23 May 2010 (UTC)

Sourness is due to acidity Taste#Sourness - adding sugar doesn't affect the acidity. Lemonade sourness is in part due to the citric acid , and also due to dissolved carbon dioxide (if it's fizzy type). There's not a reaction between sugar and citric acid to be expected in lemonade (though it could possible esterify) I'm fairly certain it is a masking effect.87.102.18.191 (talk) 16:25, 23 May 2010 (UTC)

Sweetness competes with each of the other basic tastes (sour, salty, bitter), in the sense that increasing sweetness reduces the perception of the others, and increasing the others reduces the perception of sweetness. A notable example is tonic water, which doesn't seem sweet to many people even though it is almost gooey with sugar. I'm not sure whether the other basic tastes compete with each other (sour versus bitter or sour versus salty, for example). Looie496 (talk) 16:39, 23 May 2010 (UTC)

There's a significant difference between the taste of "straight" tea and coffee, which tend to be bitter, vs. adding sugar to them. The one I'm not sure you can do much about is saltiness. I can't think of any obvious way to counter saltiness other than simply diluting it (as you could with the other items as well). ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:30, 23 May 2010 (UTC)

The old wives' way of adding a potato to oversalted stews (and then discarding the potato, which will have absorbed the excess salt) does work. Never tried it for anything else, though. --TammyMoet (talk) 09:59, 24 May 2010 (UTC)

Has anyone seen Neptune with the naked eye?

Although it is commonly claimed that Neptune is too faint to be seen with the naked eye, this is not really true.

Brian skiff has tried but he failed to see it. The conditions were not optimal as Neptune was low in the sky. He claims that from the Southern Hemisphere it would be straightforward to spot. So, this suggests that there should be quite a few (amateur) astronomers with excellent eyesight who have seen it, but I haven't seen any such claims. Count Iblis (talk) 17:53, 23 May 2010 (UTC)

At a magnitude of ~8-7.78, it would require exceptional conditions to see it: an experienced astronomer who knows how to look for faint objects, exceptionally clear sky, hundreds of kilometers from any city, and knowing exactly where to look. Even if you could, by some miracle, manage to see it, I'm not sure that you could distinguish it from any other faint star out there. Do you know the positions of the tens of thousands of stars at least that bright with a high enough degree of precision to distinguish one barely visible point of light from another one? As the forum points out, even Uranus, with a magnitude of up to 5.32, and 4 Vesta, of magnitude up to 5.1, were not discovered and named until telescopes were around. I would hazard a guess that most celestial objects dimmer than magnitude 5 were not cataloged and named until after the invention of the telescope. Now granted, "named and recognized" is not the same thing as "ever seen", but if you can't recognize a faint dot as Neptune, do we really count that as "seeing" it? Buddy431 (talk) 18:22, 23 May 2010 (UTC)

Yes, "seeing Neptune" with the naked eye would be a tour de force involving detailed star charts and identifying all the brighter objects in the immediate neighborhood. But note that quite a few (amateur) astronomers do exactly this sort of a thing as a sport, but usually for spotting Messier objects with the naked eye. They keep logs of successful naked-eye observations, see e.g. here. So, given this dedicated effort, I find a bit strange that only [Brian Skiff's report] of his failure to see Neptune exists. Count Iblis (talk) 00:24, 24 May 2010 (UTC)

Incidentaly, Wikipedia doesn't have a comprehensive list of astronomical objects (or even stars) by magnitude that's very good. We have the List of brightest stars going down to magnitude 2.5. It would be nice if we could get lists for the other ranges (i.e. List of stars with magnitude 2.5-3.5, list of stars with magnitude 3.5-4.5, etc). If there are machine readable star catalogs available, such lists could be made with some sort of bot. Of course, such lists may be seen as "indiscriminate" by the deletionists here... Buddy431 (talk) 18:49, 23 May 2010 (UTC)

The problem with such a table is that the number of stars at magnitude X grows exponentially in X (there are roughly 3 times more stars with magnitude 2.5-3.5 than with magnitude 1.5-2.5, and another 3 times more with 3.5-4.5). So you get into really large numbers really fast - and I suspect for most of these stars we have very little information. --Stephan Schulz (talk) 11:41, 24 May 2010 (UTC)

I'm envisioning something along the lines of our list of minor planets. There's only about 10,000 stars in the Bright Star Catalogue (as opposed to 200 000 minor planets...), which would easily be manageable if broken into sets of 1000 or so. Even the Henry Draper Catalogue "only" has 350 000 entries: I imagine some sort of manipulatable list could be created from it too. It looks like the astronomy club here is currently trying to improve the table for their minor planets: maybe I'll drop by and try to urge them to work on stars next (I know, I know, or I could do it myself... much too lazy for that). Buddy431 (talk) 16:57, 24 May 2010 (UTC)

No fish

Is there a term for someone who eats meat, fruit and vegetables but doesn't eat any fish? Servien 18:47, 23 May 2010 (UTC)

Closest I've found so far is Pollotarianism, which excludes fish and mammals. Vimescarrot (talk) 18:53, 23 May 2010 (UTC)

Are there enough people that fit that description to warrant having a name for it? --Tango (talk) 19:17, 23 May 2010 (UTC)

I know two. They can eat mammals such as whale but are highly allergic to all fish (salt water and fresh), seafood and crustaceans. It is one of the nine most common food allergies. Kittybrewster ☎ 19:29, 23 May 2010 (UTC)

Reverse pescetarian? Clarityfiend (talk) 20:23, 23 May 2010 (UTC)

How does anti-pescatarian sound? Or just apescatarian. Vranak (talk) 21:03, 23 May 2010 (UTC)

Like they wouldn't eat fruits or vegetables either. Clarityfiend (talk) 21:09, 23 May 2010 (UTC)

Pesca- just means fish though. Apesca = no fish. Vranak (talk) 21:33, 23 May 2010 (UTC)

Heh, nice term. I guess that applies to me. I eat meat, vegetables and fruit, but I'm not a fan of fish so I don't eat it. Regards, --—Cyclonenim | Chat  22:33, 23 May 2010 (UTC)

Of course it's hard not to notice that the first part of the term forms the words ape scat. Vranak (talk) 22:47, 23 May 2010 (UTC)

Jane Brody has used the term "pescaphobia". Looie496 (talk) 22:58, 23 May 2010 (UTC)

That implies an irrational fear of fish, but if one is allergic, it's a rational fear, and if one simply doesn't like the taste of fish, that's neither irrational nor a fear, it's just personal preference. That does not preclude the possibility that there could be some having an irrational fear of fish. However, terms like vegetarian and vegan are preferred over "carniphobia" or whatever the equivalent would be. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:03, 23 May 2010 (UTC)

Bird call

What bird is this? http://commons.wikimedia.org/wiki/File:Unknown_bird_call_MN_052210.ogg

Taken 2010-05-22 in Interstate State Park. I was not able to see the bird making this call (all weekend!).

-Ravedave (talk) 20:37, 23 May 2010 (UTC)

Dragons

Are we absolutely sure that dragons have never existed? I find it interesting that almost every part of the world has stories about dragons of some form or another. Seems strange for something that was never real. If there *were* dragons (not saying fire breating and flying, which AFAIK would be impossible - just really big carnivorous reptiles, or even the long, thin, Chinese-style water-based ones) and their numbers were declining at around the same time that humans were becoming civilized, and the last few had been wiped out before 1000AD (say), would there even be any ovbious evidence today of their existence? Just curious. --95.148.108.186 (talk) 21:06, 23 May 2010 (UTC)

If they don't breathe fire or fly, why would anybody call them dragons instead of "just really big carnivorous reptiles"? Clarityfiend (talk) 21:14, 23 May 2010 (UTC)

Because they were stories of heroism that were exaggerated in the telling and re-telling? Going from a dinosaur/big lizard-like creature, to something with borderline magical powers? Don't know really, I was just thinking on the screen. :) --95.148.105.95 (talk) 21:25, 23 May 2010 (UTC)

Really big carnivorous reptiles? Like crocodiles and alligators? Or dinosaurs? They definitely exist(ed). --Tango (talk) 21:20, 23 May 2010 (UTC)

Or Pterosaurs? ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:45, 23 May 2010 (UTC)

Or Komodo dragons? "really big carnivorous reptiles" ... check, check, and check. We even call them "dragons". -- 174.24.200.38 (talk) 01:24, 24 May 2010 (UTC)

I believe the biggest issue is that dragons have, by classical definition, six appendages (four legs and two wings), while (and correct me if I'm wrong), all other higher land-going lifeforms have four. Snakes of course don't count; they have none. But six, no, that just doesn't seem feasible from an evolutionary standpoint. And then there's the small matter of there being no fossil record of such a thing. Vranak (talk) 21:31, 23 May 2010 (UTC)

Take a look at draco (genus). Looie496 (talk) 22:54, 23 May 2010 (UTC)

Fair enough! I'll revise that 'classical definition' then -- four legs and flappable wings, for more than just gliding. Vranak (talk) 23:19, 23 May 2010 (UTC)

two points, both from Dragon

• in Origin and Etymology "Dinosaur and mammalian fossils were occasionally mistaken for the bones of dragons and other mythological creature; for example, a discovery in 300 BC in Wucheng, Sichuan, China, was labeled as such by Chang Qu...." ... more in that section
• in Dragon#Indian , after removing hyperbole, appears to be a description of a Python

Anyway , if it didn't exist you'd have to invent it .. those long cavemen evenings without TV, and kids always asking "what is there over there/below"87.102.18.191 (talk) 21:37, 23 May 2010 (UTC)

I'm also likely to believe the idea of dragons being an exaggerated folk memory (of v. big snakes and crocs) - reason - apparent absense of dragon myths in countries that do have big snakes and crocs.87.102.18.191 (talk) 21:43, 23 May 2010 (UTC)

Folk memory, yes. Perhaps as with other mythical creatures, e.g. the unicorn. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:47, 23 May 2010 (UTC)

They probably come from descriptions of rhinoceri. (original research?) --Kurt Shaped Box (talk) 21:54, 23 May 2010 (UTC)

I've heard that theory before. And there typically weren't any rhinos in Europe, just the Rhineland, which is unrelated as far as I know. There's a much more modern analogy, though, and that is the current stereotype of what flying saucer aliens look like, i.e. like the characters in Close Encounters and E.T., which apparently evolved over time from the appearance of primitive crash-test dummies used in high-stratosphere balloon tests. This contrasts with The Day the Earth Stood Still, where the aliens looked like Michael Rennie. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:00, 23 May 2010 (UTC)

Which, trust me, was a lot more scary. HalfShadow 22:01, 23 May 2010 (UTC)

Yep. Klaatu barada nikto, and all that sort of thing. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:03, 23 May 2010 (UTC)

I have to ask -- I know this phrase from Army of Darkness, but does it have any deeper/earlier meaning? Vranak (talk) 23:18, 23 May 2010 (UTC)

We have an article on it, which I've now linked. Without looking at it first, I know "Klaatu" was the name of the alien played by Michael Rennie, and the whole phrase was spoken to the robot Gort, which somehow told him where to find Klaatu. That's a lot of info to be contained in 2 words, but the robots were programmed with a series of commands which were like shorthand of some kind. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:26, 23 May 2010 (UTC)

Also note that different parts of the world having stories about "dragons" is not terribly telling. A Chinese dragon isn't all that similar to a European dragon other than the fact that they're both mythical reptiles. Do big, scary (or auspicious, depending on your point of view) exist? Absolutely. Buddy431 (talk) 23:01, 23 May 2010 (UTC)

I have heard it proposed, though not directly by the experts of the field, that it goes way back. When our mammalian ancestors were evolving, there were still dinosaurs around. It would stand to reason that early mammals would have been extraordinarily cautious about large carnivorous reptilian animals. The theory that was proposed is that the reason that many human cultures have a dragon of sorts is just because those descriptions stand out to us on residual instinct. Now is that likely after 65 million years? I have no clue, maybe someone else can comment. Falconus^{p t c} 00:27, 24 May 2010 (UTC)

Hey, this seems to be directly related to what I just said above. An Instinct for Dragons.Falconus^{p t c} 00:33, 24 May 2010 (UTC)

I try to refrain from just giving comments which don't add to the discussion, but i have to say the above is just absolutely fascinating! What an amazing hypothesis. Vespine (talk) 00:55, 24 May 2010 (UTC)

I also heard that theory long ago. I think it was termed "racial memory". It seems a little far-fetched. However, humans often show a fear and distrust of reptiles in general, including the serpent in Genesis as just one example. Whether that's "racial memory" going back to times when mammals and dinosaurs may have co-existed, or if it's just good sense, is hard to say. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:36, 24 May 2010 (UTC)

On the subject of "pre-programmed" fear or knowledge of serpents - the plant/drug Yage is commonly reported to produce hallicinations of predators such as big cats/snakes.. even in people brought up in countries with no such thing [12] (also [13]) (it was reported possibly less reliably by Terence McKenna that even eskimos hallucinate cat predators under it's influence) If that is someway related to some sort of built in DNA memory of giant reptiles is tenuous .. It's not as far as I know been shown that people with no concept of cats / snakes hallucinate them under it's influence. Probably irrelevant.87.102.18.191 (talk) 01:33, 24 May 2010 (UTC)

Right. It is highly doubtful the "genetic memory of the dinosaurs as the arch-nemesis of humans" hypothesis has any merit at all. At the time dinosaurs went extinct our ancestors were not even monkeys; actually, at the time of the last dinosaurs the lemurs and the tarsiers did not yet split into separate lines (we are on the "tarsier" line, haplorrhini, in case you wonder). Big cats, hippos, and early hominids / humans were and are until this day a much more real and a much more present threat to our ancestors. Yet we do not have much of a natural fear of cats, large herbivores, or other people. What humans usually fear are bacteria, viruses, cockroaches, snakes, and spiders. People go to the zoo to see the tiger; people run away when they see a garter snake. A flying snake should be an outright nightmare. Hence, I guess, is the dragon. --Dr Dima (talk) 01:36, 24 May 2010 (UTC)

There are plenty of tropes which tend to occur independently in all sorts of cultures and stories. Like superhuman strength - how many people do you think in the history of man have been carrying something and thought it would be really neat if they could pick up the whole load in one hand? Or flight - all kinds of legends and myths talk about people soaring through the sky, not because humans ever had the ability to fly, but because it's almost universally held that it would be awesome. ZigSaw 11:51, 24 May 2010 (UTC)

over eating

If a person is disabled or older they cannot do as much exercise as may be needed for weight control. Therefore weight control is dependent on not over eating. Yet because the human body requires so little food it is very easy to over eat. Is there a pill or other means of controlling appetite so that a person will not over eat due to a feeling of hunger? 71.100.3.228 (talk) 21:24, 23 May 2010 (UTC)

There are lots of appetite suppressants available. I won't comment on their efficacy or safety, but they certainly exist. --Tango (talk) 21:45, 23 May 2010 (UTC)

What about other means besides pharmaceuticals? Are their foods or other means to control or eliminate appetite? 71.100.3.228 (talk)

I've heard of the opposite effect, i.e. that places like McDonalds used to put chemicals into your food which made you feel full slower, and thus more likely to buy more food. Regards, --—Cyclonenim | Chat  22:31, 23 May 2010 (UTC)

Regards what? 71.100.3.228 (talk) 04:27, 24 May 2010 (UTC)

"Regards" is a formal way of ending a letter. I don't see it much in Web postings, but that's what Cyclonenim meant. Comet Tuttle (talk) 06:58, 24 May 2010 (UTC)

It works better for starting threads than replying to them, but it's part of the signature and I sure as hell can't be arsed to write it out every time (i.e. think when it's needed). Regards, --—Cyclonenim | Chat  07:32, 24 May 2010 (UTC)

When I see it at the end of a web post I'll continue then to append (the word) nothing. 71.100.3.228 (talk) 08:47, 24 May 2010 (UTC)

Studies have shown that the feeling of satiety comes from bulk, not calories. Eat lots of vegetables and fresh fruits - bulk without much calories - and wheat- or oat-fibre too to fill you up. Avoid foods containing fat, especially saturated fat (although a small amount of fat is required for health). See http://www.nutritiondata.com/topics/fullness-factor After a few months you will prefer healthy food and be disgusted by fatty junk food. 92.28.255.202 (talk) 22:24, 23 May 2010 (UTC)

Byetta is a powerful appetite suppressant, which also delays emptying of the stomach. It is presently commonly used as a prescription drug for Type 2 diabetics, but might be the next big weight loss drug. The article notes some undesirable side effects of the drug. Edison (talk) 00:44, 24 May 2010 (UTC)

For severe cases of obesity, where the standard advice of diet and exercise does not work, bariatric surgery has been used to reduce the size of the stomach. A smaller stomach means that less food is needed to obtain satiety. -- 174.24.200.38 (talk) 01:20, 24 May 2010 (UTC)

The diet market is massive, so you'll hear hundreds of claims of "miracle diets" and "pills". Even moderate exercise can help though. Under normal conditions weight gain or loss is down to the amount of energy you use, minus the energy you take in from food (calories). You can increase your use of energy as well as decrease your intake and it works very well. FT2 ^{(Talk | email)} 04:17, 24 May 2010 (UTC)

This remedy is where the problem begins... exercise only increases hunger making the task to reduce intake even harder. 71.100.3.228 (talk) 04:25, 24 May 2010 (UTC)

No, I read about a study which said that although people did eat more after exercise, the extra calorie intake was still less than that expended. So there is no excuse for not exercising. Never mind the drugs - a simple thing to do, without possible bad side-effects, is to make sure you eat enough fresh vegetables and fruit each day. Something that may block this is that many people in my experience do not know how to do simple cooking, such as boiling vegetables (cut into chunks and put in a saucepan of boiling water for a few minutes until tender), and so have to buy junk food instead. 92.28.251.49 (talk) 11:13, 24 May 2010 (UTC)

Hunger is a very inaccurate sensation. People tend to feel hungry if they haven't eaten what their body is used to them eating at a given time of day. The calories you actually need are a very small factor in determining hunger. That means you generally don't feel significantly more hungry if you increase your activity (of course, if you try and run a marathon you are going to notice a need for extra calories, but small changes can easily go unnoticed). --Tango (talk) 00:33, 25 May 2010 (UTC)

help pLz \\ drugs used in managment of infusion

describe the drugs used in managment of infusion - related to side effects —Preceding unsigned comment added by Mrmr-rana (talk • contribs) 21:33, 23 May 2010 (UTC)

You're going to need to be much more specific if you want a meaningful answer. What type of infusion do you mean? Also note that we cannot give medical advice on the reference desk. If this is about a treatment you or someone you know is undergoing, you should talk to the doctor who's administering the treatment. Buddy431 (talk) 22:56, 23 May 2010 (UTC)

Possibly means "Blood infusion" ie Blood transfusion - an anticoagulant is Heparin, Paracetamol is used if minor side effects occur [14] not a medician so don't know much more.87.102.18.191 (talk) 00:32, 24 May 2010 (UTC)

This looks more like a homework question than a request for medical advice to me. AndrewWTaylor (talk) 08:18, 24 May 2010 (UTC)

I really hope it is, I'd hate for the triage nurses to have brought in a wireless laptop just to have the physician's Reference Desk question get rejected ZigSaw 11:39, 24 May 2010 (UTC)

Tiny bullet-shaped dog

I saw the tiniest dog I've ever seen being taken for a walk recently. It was white and bullet shaped, with the head forming the curved cone-like front of the bullet. Moving at walking pace, its little short legs were a blur, as its stride could only have been one or two inches. It was not a sausage-dog or a chichua. It did not behave like a puppy, but like a disciplined fully-grown dog. What breed could it have been? 92.28.255.202 (talk) 22:21, 23 May 2010 (UTC)

Sounds more like a pet guinea pig to me. 71.100.3.228 (talk) 22:38, 23 May 2010 (UTC)

or White rat on a lead ? (it happens).87.102.18.191 (talk) 22:44, 23 May 2010 (UTC)

What was its coat like? And it's not a Scottish Terrier is it? Vranak (talk) 22:46, 23 May 2010 (UTC)

It was not a guinea pig or a Scottish terrier. It had short fur. 92.28.255.202 (talk) 22:49, 23 May 2010 (UTC)

Sure it wasn't a ferret? --Kurt Shaped Box (talk) 22:51, 23 May 2010 (UTC)

It was definately a dog, and not a rat or ferret. 92.28.255.202 (talk) 22:53, 23 May 2010 (UTC)

Try teacup dog. 71.100.3.228 (talk) 23:06, 23 May 2010 (UTC)

It may have been something like a Bull Terrier (Miniature) except it had no neck, and shorter legs. Apparantly there are "designer dogs", so perhaps it had been specially bred to be super-tiny. 92.28.255.202 (talk) 23:14, 23 May 2010 (UTC)

Maybe a Pomeranian (dog)? —Preceding unsigned comment added by 86.4.186.107 (talk) 07:52, 24 May 2010 (UTC)

In case you haven't found it yet, the article on List of dog breeds gives you loads of pictures. If you were in Yorkshire, it's likely to have been a ferret.--Shantavira|^{feed me} 08:48, 24 May 2010 (UTC)

It was not a pomeranian as it did not have a fluffy coat, and a pomeranian is not bullet shaped either. Perhaps I underestimated the stride - it may have been more like three inches. I have seen ferrets being taken for a walk on one or two other another occassions, and it was definately not a ferret. If miniature Bull Terrier puppies have short legs and no neck, then it could have been one of them. As it had to concentrate on moving its little short legs as fast as propellors, then it may not have had time to indulge in the usual romping puppy behaviour. My best guess is that it was a cross between a minature Bull Terrier and some other minature dog that gave it tiny legs and no neck. 92.28.251.49 (talk) 11:00, 24 May 2010 (UTC)

These are miniature bull terrier puppies. I don't know if they're what you saw, but they I do know that they are adorable. --Mr.98 (talk) 15:51, 24 May 2010 (UTC)

Next time, ask the person who is walking the animal. Failing that, a photograph would be more useful than any verbal description. --Teratornis (talk) 19:43, 24 May 2010 (UTC)

In any case, it might not be a recognized breed at all—it could be a mixed-breed dog. --Mr.98 (talk) 21:45, 24 May 2010 (UTC)

May 24

OIL SPILLS

Technically aren't asphalt highways just oil spills mixed with dirt? 71.100.3.228 (talk) 02:26, 24 May 2010 (UTC)

No. Part of the definition of "spill" is that it is accidental. Also, asphalt is a specific component of crude oil, rather than crude oil itself. --Tango (talk) 02:32, 24 May 2010 (UTC)

That's right — fractional distillation is used to separate crude oil into things like gasoline, kerosene, and asphalt. But then the asphalt is indeed mixed with dirt; our asphalt article, in its Rolled asphalt concrete section, states that an asphalt highway is actually only 5% asphalt itself, and 95% "aggregates", meaning gravel, sand, and stones. Comet Tuttle (talk) 06:56, 24 May 2010 (UTC)

Roads and urbanization are a different form of habitat destruction than oil spills. They definitely all involve introduction of non-natural (or at least, non-local) materials into the environment, often significantly altering the local ecosystem. However, unlike oil spills, roads have a measurable benefit - improving the quality of life for humans - so there is at least some level of tradeoff to consider. Nimur (talk) 14:43, 24 May 2010 (UTC)

Asphalt is not a liquid, so it doesn't have the same effects that the liquid crude oil has on birds, fish, etc. --Chemicalinterest (talk) 14:55, 24 May 2010 (UTC)

Roads are also confined to discrete areas; their destruction is intense, but it covers only a fraction of land area. Roads generally do not move on their own, so animals have some hope of avoiding their hazard. Oil spills on water can spread widely and uncontrollably. Sea birds and other animals have trouble avoiding oil slicks. However, note that motor vehicles can drip appreciable amounts of engine oil onto road surfaces, which tends to run off during rain storms, thereby polluting the runoff. A busy roadway thus functions like a low-level oil spill that continues indefinitely. A widespread shift to battery electric vehicles and bicycles instead of the current dominance of internal combustion engine vehicles would greatly reduce oil pollution on road surfaces. --Teratornis (talk) 19:40, 24 May 2010 (UTC)

Well, if you're advocating some kind of worldwide mandate to ban automobiles and force everyone to use bicycles or glorified golf carts, then we will veto it in the United Nations before you can say "oil spill". This kind of change is absolutely out of the question for civilized, industrialized nations -- what about the eighteen-wheeler trucks that take merchandise from the warehouse to the local neighborhood store? A much better way would be to implement more frequent, more stringent and consistent mechanical inspection requirements for motor vehicles to make sure they don't drip motor oil all over the place -- this would achieve substantially the same result, but without nationwide economic upheaval that your proposal would cause. 67.170.215.166 (talk) 06:38, 25 May 2010 (UTC)

acetone

does acetone evaporate like alcohol or does it leave a residue? can u use it on food surfaces? —Preceding unsigned comment added by Tom12350 (talk • contribs) 03:37, 24 May 2010 (UTC)

Yes, it evaporates very quickly, maybe not as quickly as most alcohols though. No, I would never use it on anything that would ever contact food. Beach drifter (talk) 03:44, 24 May 2010 (UTC)

After a little reading, it appears to be hardly toxic at all. I still see no reason you would need to use it in the kitchen. Beach drifter (talk) 03:47, 24 May 2010 (UTC)

can i use it on a plastic counter top, and a particle board kitchen table with a wood looking plastic/ vinyl vanear —Preceding unsigned comment added by Tom12350 (talk • contribs) 04:11, 24 May 2010 (UTC)

It's a solvent, so plastic-based and printed food surfaces might get damaged, or colors from packaging transfer. What would you intend to use it for? FT2 ^{(Talk | email)} 04:12, 24 May 2010 (UTC)

There are lots of products specifically designed for this use, visit your local supermarket. Vespine (talk) 04:50, 24 May 2010 (UTC)

No. Don't use it on those - it will dissolve them, then evaporate, leaving an impossible to clean mess. Not really a mess - more like a mushy smear of the veneer. It's pretty non-toxic though (it's actually legal as a food additive!), and does not leave any residue behind, so in that regard it's safe in the kitchen. I use acetone to remove stickers. But you have to work VERY fast, it evaporates very quickly - even the open bottle will evaporate. Put the acetone on a tissue, and rub the sticker - don't put the acetone on the sticker, it will dissolve the glue, then run, leaving a bigger sticky spot than when you started. Ideally have a second person to cap the bottle in between putting some on the tissue. Acetone is probably the fastest evaporating solvent commonly available. Ariel. (talk) 05:32, 24 May 2010 (UTC)

A little WD-40 will remove stickers as well and there's no bottle to close. Dismas|^(talk) 08:10, 24 May 2010 (UTC)

You dont' want to use that stuff in the kitchen, though, it leaves a mess and it can be toxic if ingested. 67.170.215.166 (talk) 06:43, 25 May 2010 (UTC)

How much are you using?! Do you lick your counter clean?! I doubt any reasonable person would A) use so much WD-40 as to be a health hazard and B) just let WD-40 sit on their counter after cleaning off sticker residue and then use that spot to make a sandwich. Dismas|^(talk) 08:06, 25 May 2010 (UTC)

how will plastic-based and printed food surfaces get damage if they use it in labs to clean plastic labware? will it help if i dilute it 50-50 w/water? —Preceding unsigned comment added by Tom12350 (talk • contribs) 06:13, 24 May 2010 (UTC)

Not every plastic is the same, some will be totally unaffected, others will dissolve into goo - there are a LOT of different kinds of plastic. I don't know what water will do, probably it will slow down the dissolving. Ariel. (talk) 08:08, 24 May 2010 (UTC)

arent there only 7 kinds of plastic? —Preceding unsigned comment added by Tom12350 (talk • contribs) 08:41, 24 May 2010 (UTC)

Category:Plastics. 212.219.39.146 (talk) 08:47, 24 May 2010 (UTC)

There are many more! I used acetone in the lab and I saw somebody cleaning a keyboard. The Grey keys like Strg And Alt got very soft and the printed letters vanished, the other white keys showed no problem and ended up very clean.--Stone (talk) 09:37, 24 May 2010 (UTC)

While there are seven classifications in the Resin identification code, the seventh is "other", and would include everything from ABS to nylon to teflon to polycarbonate. -- 174.24.200.38 (talk) 04:38, 25 May 2010 (UTC)

The better cleaning agent for you might be, what other people use for disinfection, it is a mixture of 70% isopropanol and water.--Stone (talk) 09:37, 24 May 2010 (UTC)

i already tried that. will it help if i dilute acetone 50-50 w/water? —Preceding unsigned comment added by Tom12350 (talk • contribs) 10:49, 24 May 2010 (UTC)

That would slow its evaporation, but it would also slow its cleaning abilities, so there would be no net difference. You can put it in a spray bottle, not a mist one, a squirt one. --Chemicalinterest (talk) 11:02, 24 May 2010 (UTC)

i dont understand. if i dilute it wont it be less corrosive? —Preceding unsigned comment added by Tom12350 (talk • contribs) 11:14, 24 May 2010 (UTC)

Yes diluting it will make it less likely to damage the plastic. Alchohol is a better choice though if you have it. What are you cleaning?87.102.85.123 (talk) 11:47, 24 May 2010 (UTC)

I used to be a follower of the "throwing assorted chemical compounds on a surface makes it cleaner" school of thought, I must admit, but a lot of 'em will ruin your crap if you aren't careful. The way I see it, just because something kills bacteria and viruses doesn't mean it's safe for you to eat. It's not that antiseptics and antibac soap are actually making the surface cleaner on a microscopic scale - they're simply poisons designed to kill microbes instead of humans. Which is why you're supposed to wipe away the disinfectant before you eat off something you use it on. In the same vein, just because something is caustic doesn't mean it's necessarily going to clean whatever you put it on. And if its effects are 75% "creating a goopy catastrophe" and 25% "cleaning the surface", no matter how much you dilute it you're still going to get three times as much goop as cleaning action. ZigSaw 11:46, 24 May 2010 (UTC)

I don't understand why you are so intent on using acetone in your kitchen. Did you get a hold of an industrial quantity and just trying to use it on EVERYTHING? Lol… if you absolutely insist on using it, at least try rub some on the least conspicuous spot first and leave it for a few minutes and rub it again, see if it damages the surface before making a mess of it.. My know it all uncle once used to clean his fancy hi fi with metho, one day he decided that acetone might be a better idea and it melted the face of the LCD display making a matted mess you couldn't even see through, he was gutted. Vespine (talk) 23:13, 24 May 2010 (UTC)

Crystal Violet

Hi there :) My name is Elin and I'm from Sweden. Right now I'm writing an assay about terraforming in astrobiology with chemistry and biology as "main subjects". I'm now stuck on gram staining and I really need to know how crystal violet is produced. When I read this article: http://en.wikipedia.org/wiki/Crystal_violet, I don't quite get the production. Mostly it's because I don't understand everything that is written, for example I don't get if it's ment that it is redox (gain) or oxidation (loss) that happens when you oxidize the compund in the second prodction step. And what about the last step? Is that the final step to get crystal violet, or is it a step to produce something else since it says "Hydrolysis of crystal violet gives the carbinol"? And what is a leuco? I've written about the first two steps, but I've left out what I've asked about (the oxidize-question, leuco and the third step). I feel like I should bring more to the table in order to get a higher grade and it would be sad if difficulties with language should stop me from getting the grade that I need. Please try and explain clearly and detailed. I don't mean that I want it to be simple, just that i'm thankful if you explain a lot since I don't understand all english words. Thanks a lot! /Elin —Preceding unsigned comment added by Ailithey (talk • contribs) 08:56, 24 May 2010 (UTC)

The leuco (white or colourless) form is oxidized with oxygen. The carbinol is a alcohol derived from methanol by substituting the hydrogen by something different, here the central C-OH is attached to three 4-dimethylaminopheny substituents.--Stone (talk) 09:46, 24 May 2010 (UTC)

The German article Kristallviolett has a better image what happens.--Stone (talk) 09:49, 24 May 2010 (UTC)

Gentian violet and Crystal_violet are the same substance, but the Gentian violet is about the medical use!--Stone (talk) 09:53, 24 May 2010 (UTC)

Thanks a lot, I'm starting to get it. But if you look at the article http://en.wikipedia.org/wiki/Crystal_violet, I still don't really get the production. The ast step says this: A typical oxidizing agent is manganese dioxide. Hydrolysis of crystal violet gives the carbinol: [C(C6H4N(CH3)2)3]Cl + H2O → HOC(C6H4N(CH3)2)3 + HCl Is this step part of the production of crystal violet? Do you get crystal violet by following all three steps, or is the last step the formula for the production of a carbinol? —Preceding unsigned comment added by Ailithey (talk • contribs) 10:38, 24 May 2010 (UTC)

The article was a bit confusing - I've changed it to avoid confusion - http://en.wikipedia.org/w/index.php?title=Crystal_violet&oldid=363908374

It should be clear now. The last step was not part of production. 87.102.85.123 (talk) 12:06, 24 May 2010 (UTC)

center of mass

why does objects rotate around it's centre of mass ..? I mean as a example, when we throw a rod (something like that) in the air holding at the edge,we can see it rotates around its CM.dany (talk) 13:19, 24 May 2010 (UTC)

Try to imagine an object that does not rotate around its CoM. Then that would mean that the CoM of the object would rotate around some point (inside or outside of the body). Therefore the CoM would be accelerating toward the point of rotation (centripetal acceleration). That would require an external force. Count Iblis (talk) 14:06, 24 May 2010 (UTC)

When an object is forced to rotate around something other than its center of mass by an external force, the object will precess, and if it continues to rotate for a long enough time (e.g., low friction or low damping), it will eventually change its rotation through a precession so that the rotation aligns with its principle axes. Nimur (talk) 14:48, 24 May 2010 (UTC)

You mean principal axes. lets mantain the principle of spelling words correctly. Dauto (talk) 16:18, 24 May 2010 (UTC)

Let's punctuate our contractions correctly, and capitalize the first word in each sentence. --Teratornis (talk) 19:25, 24 May 2010 (UTC)

lets not. Dauto (talk) 02:27, 25 May 2010 (UTC)

aching muscles = laughing reflex?

Yesterday I played in an action cricket tournament. Being the most unfit person ever, today my muscles are all exacting their revenge on me and I could hardly roll myself out of bed this morning. Funny thing is, I discovered that whenever I move (and stretch some of my sore muscles) I get this urge to laugh for no apparent reason. Even thinking about it now makes me giggle. Is this a known thing or am I the only one? Could it be related to tickling (I'm VERY ticklish and laugh uncontrollably when people try to tickle me, even before they've made any contact)? I tried Googling but I'm getting false hits about laughing so much your muscles ache. Zunaid 16:28, 24 May 2010 (UTC)

The Delayed onset muscle soreness article does not mention this effect. You could ask on that article's talk page if you get no help here. --Teratornis (talk) 19:30, 24 May 2010 (UTC)

You evidently have an easily-triggered laugh reflex, so perhaps the pain in your muscles triggers this by reminding you of the fact that you find the situation amusing. Dbfirs 06:57, 25 May 2010 (UTC)

Sodium hypochlorite and Sodium acetate

I mixed solutions of sodium hypochlorite and sodium acetate together. Is the hypochlorite strong enough to oxidize the acetate ion? I noticed some gas being produced (not much), but otherwise there was no indication of a reaction. Thanks. --Chemicalinterest (talk) 17:19, 24 May 2010 (UTC)

(edit conflict with below) Oxidize it to what? Peracetic acid? Usually that's done with hydrogen peroxide, but hypochlorite isn't that much weaker of an oxidizing agent than peroxide, so I suppose it could. Even with hydrogen peroxide, the equilibrium still lies to the left, so it makes sense that only a little, if any acetic acid would be oxidized. Buddy431 (talk) 20:40, 24 May 2010 (UTC)

Did you look on a standard reduction potential table? We've linked them before, and there are many of them out there on the internet and in books as well; the numbers should tell you if it is possible for hypochlorite to oxidize acetate. The only possible products are the chloride ion and carbon dioxide, so if hypochlorite DID oxidize acetate, you'd get some bubbles. --Jayron32 20:31, 24 May 2010 (UTC)

The standard reduction table here doesn't have acetic acid, so no beans. And why do you say only that Chloride and CO₂ are the only products? It could only be reduced to chloride gas (a weaker oxidizing agent than the hypochlorite), which could be the bubbles observed. Buddy431 (talk) 20:42, 24 May 2010 (UTC)

Chloride gas doesn't exist, but hydrogen chloride might. --Chemicalinterest (talk) 21:06, 24 May 2010 (UTC)

I meant chlorine gas. Hydrogen chloride would stay in solution. Buddy431 (talk) 22:35, 24 May 2010 (UTC)

Doubtful. Chlorine gas disproportionates to hypochlorite and chloride in any basic solution, see Chlorine_bleach#Chemical_interactions. Cl2 may be an isolatable intermediate, but I think that spontaneously, the chloride ion ends up being the lowest-energy product here. Consider that the Eo for the reduction of chlorine gas is highly positive itself... --Jayron32 21:03, 24 May 2010 (UTC)

Special Relativity

One of the implications of Einstein's Theory of relativity is- If two observers are in relative motion, they will not, in general, agree as to whether two events are simultaneous. If one observer finds them to be, the other, in general, will not. Now I read this example in Halliday/Resnick, Fundamentals of Physics. Two observers Sally and Sam stand in two long spaceships. They are stationed a the midpoint of the two ships. The relative velocity of ssSally with respect to ssSam is v separating along a common x axis. They are stuck by two meteorites just when they were crossing each other, one setting off a red flare and the other blue, leaving marks at R and B on ssSam and R' and B' on ssSally. Let us suppose that Sam and Sally are positioned right in the middle of R and B and R' and B'. Sam receives the two light waves at the same time and gave the following explanation. Sam: Light from event red and light from event blue reached me at the same time. From the marks on my spaceship, I find that i was standing halfway between the two sources. Therefore, event red and event blue were simultaneous events. Sally and the expanding wavefront from event red are moving towards each other, while she and the expanding wavefront from event blue are moving in the same direction. Thus, light from event red reaches her before light from event blue. Her explanation goes as follows. Sally: Light from event red reached me before light from event blue did. From the marks on my spaceship, I find that i too was standing halfway between the two sources. Therefore, the events were not simultaneous. These reports do not agree. Nevertheless, both observers are correct.

My question goes as follows: If we observe the two spaceships from a third inertial reference frame, we will discover that the two events occurred simultaneously as they occurred at a unique instant when the two spaceships coincided on the x-axis. Does that mean Sally's explanation was wrong? If that is so, is the first postulate of the Theory of Special Relativity contradicted? Please explain the validity of Sally's explanation in this light. --Lightfreak (talk) 18:20, 24 May 2010 (UTC)

You said that Sam is equidistant from R and B and saw light from the two flares at the same time. That means that the two collisions were simultaneous in the rest frame of Sam, so your third inertial frame is the same as the rest frame of Sam. There is no unique instant when the spaceships cross because they have length; it takes a while for them to pass each other completely. There is a unique instant in a unique inertial frame when the ships occupy the same range of x coordinates, but the collisions didn't happen at that instant. (One of them may have, but not both.)

I don't think there's much insight to be gained into special relativity by looking at different reference frames. It's like checking that 5+5+5 = 3+3+3+3+3 and 7+7+7+7 = 4+4+4+4+4+4+4 and so on. What you really want to understand is why multiplication is commutative in the first place; then you don't have to try all the special cases. The best way to understand this problem is to draw a spacetime diagram showing all of the events. -- BenRG (talk) 18:51, 24 May 2010 (UTC)

What is the point of a lawn?

Besides the aesthetic aspect, is there any coherent reason to constantly trim, weed, fertilise and reseed the part of your property with nothing built on it? I can understand preventing erosion, but wouldn't regular old wild weeds do that? Does anything horrible happen when grass gets too long? It seems to me that a ludicrous amount of money goes into herbicides, mowers/gas, fertilizers and all kinds of ugly side effects of fighting natural selection to get a "good-looking lawn". Unless there's some benefit I'm not seeing... ZigSaw 20:36, 24 May 2010 (UTC)

Small animals, some of which may be pests, can hide in tall grass. Jc3s5h (talk) 20:41, 24 May 2010 (UTC)

I figured lawns were a sign of the wealthy being able to afford land and to manicure it as well. As well as for aesthetic purposes, lawns provided ample grounds for one's "constitution" I suppose. More recently, lawns are smaller and part of the package when you buy a nice house. It's probably more for aesthetic purposes now than it ever was, because most lawns (at least around where I live) are so small, you can't even play Badminton on them. Backyards usually allow for a single sport and maybe that's it... barbecues and other activities are restrained to a porch. I know that with my family's country estate, we have no "lawn", because it's all overgrown and wild and absolutely beautiful. (According to lawn, it's still a lawn.) Of course, lawns at, like, Versailles, are simply ostentatious but stunning. – Kerαunoςcopia^◁_galaxies 20:43, 24 May 2010 (UTC)

There's nothing wrong with doing things for aesthetic purposes. You either do something because you want to adhere to cultural norms, or you do it specifically to fuck with cultural norms. So, either you maintain a lawn because its expected, and your culture tells you it looks good, or you let it grow wild because you want to intentionally go against those norms. Either position is equally valid, and both have as much weight. It comes down to personal aesthetic choice and little else. --Jayron32 20:52, 24 May 2010 (UTC)

Kids and pets can play on them. They are pleasant places to sit or snooze with a beer and a good book. Grass is basically outdoor carpeting. If you don't have grass then you have...what?

1. Nothing - you live in an apartment with no outdoor space.
2. Dirt - which you can't lie on and isn't comfortable to walk on - and is unusable for days after rain.
3. Xeriscape - less work but also uncomfortable to lie on. Also, doesn't naturally absorb dog poop and is hopeless for little kids to kick a ball around on.
4. Concrete - ugly, also not very useful for all the reasons above.

If you want extra space beyond your indoor living space, a garden...and therefore a "carpeted" garden is the way to go. Grass is the natural choice because unlike most other plants it's evolved to survive being grazed by herbivores - and can therefore be mowed to keep its height in check and to maintain the density needed.

Having said all that - my house is situated out in woodland and my kid is old enough not to need to go out and play in it - so we mostly have wild grass which doesn't grow too long because of the dense trees - and doesn't get mowed because we don't live someplace where we have to conform to social norms with manicured grass.

SteveBaker (talk) 21:05, 24 May 2010 (UTC)

This probably goes back to the rise of surburban life - in the 20th century - before then people didn't have lawns - they either lived in towns (with almost certainly no garden at all) or in the countryside.. Lawns did exist prior to surburbanisation - notably common land such as the village green; the lawns would be 'mowed' mostly by sheep - which do a very good job.

The rise of surburban life meant that everyone got their own miniature village green - called a garden. (along with a miniature mock tudor mansion - or 'semi').

That is basically the origin of the grass lawn. Basically people now imitate the cutting sheep once did using lawnmowers. Strange behaviour but true. If you don't believe me ask on the humanities desk. Obviously grass is good for playing on. Doh, I just found out all this is at lawn, nobody will read it anyway. 87.102.85.123 (talk) 21:39, 24 May 2010 (UTC)

We do have a History of the lawn article: they appear to date from before the 20th century: the first lawnmower (as opposed to a scythe) was invented in 1827. Buddy431 (talk) 22:28, 24 May 2010 (UTC)

As mentioned above by many, having a lawn at the backyard is actually quite nice. I just want to point out that you don't really need to use herbicides, fertilisers or gas to have a nice lawn. I don't use any of that and still am quite happy with my lawn. Dauto (talk) 03:19, 25 May 2010 (UTC)

Old Testament

Old Testament states "Adam has lived 930 years".How this can be explained? Real today's years, or possible short years of the old time? Does the length of years,as days,may be variable? Today 1 year=365 days, but billion years ago 1 year=15 days for example?TASDELEN (talk) 21:13, 24 May 2010 (UTC)

There's no evidence such intervals have changed that much in Earth's history. 67.243.7.245 (talk) 21:32, 24 May 2010 (UTC)

In scientific terms, it is explained by pointing out that many cultures have myths that are not scientifically accurate. Anything other than that is sheer interpretation. Creationists and others who are decidedly not scientific (in that they take their conclusions as givens and then work backwards from there) usually say things like "God let him live that long" and "since the time of the Flood people have been more and more sickly and sinful and degraded" and things of that nature. See e.g. Answers in Genesis, a young-earth creationist ministry. But there is absolutely zero scientific evidence for this and it is entirely implausible from a truly scientific standpoint. AIG happily distorts scientific evidence to fit its very literal interpretation of the Bible. Frankly I think (as a nonreligious person) that such analytical attempts miss out on the entire point of the Bible, which was not meant to be considered a science textbook. But that's a personal opinion, to be sure. --Mr.98 (talk) 21:34, 24 May 2010 (UTC)

(edit conflict with above x2) Look at this article we have: Longevity myths#Biblical. Some scholars argue that people inflate the lifespans of their important patriarchs and elders (sociological/anthropological reasons I guess, I'm not in this field, so I can't discuss that aspect any more). Note that most (i.e. all) non-religious scholars do not believe that there was a literal single first human (named Adam or otherwise). Buddy431 (talk) 21:37, 24 May 2010 (UTC)

(ECx3) I don't know why this is on the science desk since the obvious scientific answer is it's all nonsense, but AFAIK it's generally held by those who believe in those parts of the bible literally that human age was significantly reduced after the great flood. E.g. [15] [16] [17] [18] [19] [20]. The reason for this is obviously something those who do believe in such things can't agree on, since it isn't really discussed in the bible but it's either thought of as a result of direct action by god (punishment or whatever), the problems/consequences that resulted from flood or the way humans have lived since then (see the earlier links some of which include discussion). Not to do with changes in the length of years AFAIK. Nil Einne (talk) 21:38, 24 May 2010 (UTC)

Not sure where you got a billion years from, neither creationists nor evolutionists would try to argue that anything like first humans were around a billion years ago. For some actual science, a DAY is determined by how fast the Earth spins on its own axis, a YEAR is determined by how long the Earth takes to orbit the sun. Days and years are independent of each other, a planet can have a long day and a short year, or a long year and a short day, there is no correlation. For example, in the Moon's orbit around the Earth, Moon days and years are actually equal, they are both one Earth month. We're less interested in length of days for the time being. As for years, the orbital period of any object around a much more massive object, like the Earth around the Sun is directly determined by the distance between the objects. This means: how far the Earth is from the Sun. The further apart the objects are the longer the orbital year. Mercury is only 0.4 of the distance from the Sun to the Earth and it has a year of about 88 days, Venus is 0.7 of the distance from the sun to the earth, it has a year of 224 days. Earth obviously takes 365 days to orbit the sun, Mars is 1.5 the distance from the Sun to the Earth and it has a year of 780 days. So for the earth to have a shorter year it would have to be closer to the Sun. There's no evidence that the Earth shuffled around or changed places since the formation of the solar system, there may have been some catastrophic events which changed the year a bit, but there's some decent evidence that the Earth has been at least in the Habitable zone, since life arose anyway. Vespine (talk) 22:42, 24 May 2010 (UTC)

So just for completeness, for Earth's year to be 15 days, it would have to be 0.15AU away from the Sun, that's a third of the distance to Mercury which is already a hot Sun scorched rock with any hope of an atmosphere blasted away long ago, quite certainly incapable of harbouring any life. So we can be pretty certain that at no stage during evolution of life was the Earth's year as short as 15 days. Going by the habitable zone link I gave above, I think shortest possible year that the Earth with life could have is about 345 days. Vespine (talk) 23:01, 24 May 2010 (UTC)

The explanation that I am familiar with is the confusion between the lunar month and the solar year that has occurred before the stories of the Bereyschitt (Book of Genesis) were written down. I think this is the explanation Zenon Kosidowski gave in his "Biblical stories" (Russ. transl. from Polish: Библейские сказания) book. Kosidowski is almost certainly not the first one to come up with it, though; I do not know who is. Our Longevity myths#Biblical article mentions this explanation, too. --Dr Dima (talk) 22:46, 24 May 2010 (UTC)

So that means he lived 930 months which would be 77.5 years, that's much more believable, while still being very old for the time. Vespine (talk) 23:04, 24 May 2010 (UTC)

According to http://multilingualbible.com/genesis/5-9.htm, Enos (or Enosh) fathered a son at the age of 90 years. According to http://multilingualbible.com/genesis/5-12.htm, Kenan fathered a son at the age of 70 years. If a "year" was a month, then 90 "years" meant 7 years and 6 months, and 70 "years" meant 5 years and 10 months. -- Wavelength (talk) 23:22, 24 May 2010 (UTC)

We may have ended up with some ages in months and others in years. Hunter/gatherers tend to use months, while farmers tend to use years, with herders using a bit of each. Since society of the time had a mixture of farmers and herders, they may have gone back and forth between the two systems. And just as we often omit the word "years" when giving our age, so do those who give their ages in months. Also realize that many books of the Bible were told, retold, written, rewritten, compiled together from multiple accounts, etc., to make the final text. This method results in rather poor quality control and many inconsistencies. This was also common to other books from antiquity, such as the Odyssey and Iliad.StuRat (talk) 00:27, 25 May 2010 (UTC)

So Enos fathered a son at 90 years old even though he died about 15 years before? (905 months = 75.4166667 years) I never knew the bible discussed sperm preservation and artificial insemination (well not counting the virgin Mary). And to think some Christians are opposed to these sort of things despite having the clear approval of god! Nil Einne (talk) 08:39, 25 May 2010 (UTC)

Five months equaled 150 days, according to http://multilingualbible.com/genesis/7-11.htm, http://multilingualbible.com/genesis/7-24.htm, http://multilingualbible.com/genesis/8-3.htm, and http://multilingualbible.com/genesis/8-4.htm. -- Wavelength (talk) 23:46, 24 May 2010 (UTC)

The modern practice of observing nature, making written records, and thinking freely and critically are recent developments. Galileo Galilei is considered to be the father of this scientific approach to thinking, and he did not do his ground-breaking work until the early 1600s. Prior to Galileo’s new approach to thinking, myth, superstition and intuition were all that was available. People were illiterate and favourite stories were passed by word-of-mouth from parents to children, generation after generation, gathering embellishment along the way. The ancient scriptures, including the Bible, were written by men in that era of myth, superstition and intuition. We should not be surprised when we find things in these ancient scriptures that are not believable. These things should be ignored. Dolphin (t) 23:50, 24 May 2010 (UTC)

That is not true. Schliemann found Troy based on the Iliad record. Archaeological sites in modern Israel, Palestinian Autonomy, and Jordan are too numerous to even start to mention, and match very well the Biblical record, at least in their location (see e.g. Temple Mount, Tel Megiddo, Tel Hazor, Tel Be'er Sheva). Timelines are far more fuzzy, as expected for the events that took place several hundred years before being written down. Regarding month / year confusion, I recall Kosidowski speaking specifically about people's ages; it may have something to do with how the human age used to be specified 3000-4000 years ago. The day and the month of the Great Flood are indeed specified, as Wavelength has mentioned; but that does not mean that Noah's age is accurately recorded. --Dr Dima (talk) 00:08, 25 May 2010 (UTC)

I didn't imply that everything found in ancient scriptures is incorrect or unsound. My view is that when we find things in these ancient scriptures that are not believable, we should not believe them. See Scientific scepticism. The alternative, to which User:TASDELEN alludes, is that the things in the ancient scriptures must be correct and therefore we need to construct an explanation that makes them believable. Dolphin (t) 04:38, 25 May 2010 (UTC)

As someone who believes in the literal truth of the Bible, I'm rather confused by the idea that "most non-religious scholars do not believe that there was a literal single first human" — wouldn't standard evolutionary theory hold that there was a point at which one organism reached the point that it would be classified as Homo sapiens? Nyttend (talk) 05:44, 25 May 2010 (UTC)

Not really, we have a Most recent common ancestor also Mitochondrial Eve and Y-chromosomal Adam. I don't think you could really pinpoint the origin or Homo Sapiens to one individual. Even if we are commonly descended through ONE of the individuals, there were thousands of other very similar individuals in the same species which just happen not have surviving descendants today. Vespine (talk) 05:55, 25 May 2010 (UTC)

(edit conflict) Not really. Speciation is a much more fuzzy and fluid concept. We don't really have a hard-and-fast definition of what makes one group of living things a distinct species. Some of the stuff is really obvious (for example, dogs are different than cats), but at the edges it becomes quite fuzzy. For every aspect of the standard "textbook" definition of distinct species, there are exceptions which are common enough to make the definition problematic. There is the Mitochondrial Eve, often cited as the ancestor of all modern humans, but that doesn't make her a single individual which was a unique species different from the other members of her community. After all, she had to be able to mate with the members of her community to have viable offspring; which would make her the same species as those other members. At a temporally zoomed-out view, we can say that the first modern humans developed sometime around, say 200,000 years ago. But its not like on Monday there were no humans, and on Tuesday there suddenly was one. AT any given point, there are a population of fully interbreedable individuals; that is usually the common definition of a species; when two populations drift genetically apart to the point where they are no longer able to produce viable offspring with each other, we generally hold that they are now different species. But its not a binary state; if we go back to the time when the populations became seperated, they likely would be considered the same species for many thousands of years before genetic drift causes them to differentiate. There isn't a single individual which represents the new species. --Jayron32 05:57, 25 May 2010 (UTC)

Postscript: Found a good link for Nyttend which discusses in more detail what I was trying to explain above. See Species problem. --Jayron32 06:10, 25 May 2010 (UTC)

TDS

Say one has a geophysical electric log with data for SP, short number (16), long number (64), and what one wants to do is to calculate/estimate the TDS (Total dissolved solids) -- water quality -- from that data. How does one go about doing that? Killiondude (talk) 22:14, 24 May 2010 (UTC)

May 25

Consider a satellite moving at 3.87 km/s - how much is the clock aboard the satellite affected by special relativity per day?

The calculation I did was $86400{\sqrt {1-(3870/299792458)^{2}}}-86400=-7.2\times 10^{-6}s$ meaning that the clock aboard the satellite falls behind by about 7.2 microseconds per day. Could someone please verify that this is the correct approach?220.253.221.60 (talk) 00:32, 25 May 2010 (UTC)

Could you give us the rest of your approach? It is difficult to know if it is right based on just the final answer. (I could try and calculate it myself and see if I get the same answer, but even if I do, that doesn't mean your approach was right - you might just have been lucky.) --Tango (talk) 00:54, 25 May 2010 (UTC)

(ec) It's fine, except that a day is 86400 seconds long, not 86500, and you can't realistically ignore general relativity in this situation. (Also, you're comparing your satellite clock to a clock "at infinity". If you wanted to compare to a clock on the surface, you'd have to take into account that surface clocks also move at up to 0.5 km/s relative to a nonrotating frame, depending on latitude.) -- BenRG (talk) 00:55, 25 May 2010 (UTC)

Ah, that's why I wasn't recognising the method! Now I see what the method is! --Tango (talk) 01:04, 25 May 2010 (UTC)

Global Average Annual Temperature limits

How low/high can the Global Average Annual Temperature drop/rise before it irreversibly spirals into either an snowball effect or a runaway greenhouse gas effect.24.78.167.139 (talk) 01:00, 25 May 2010 (UTC)

I don't think the scientific community has reached a consensus on that. I'm not sure there is even a consensus that either of those things would happen at all. --Tango (talk) 01:12, 25 May 2010 (UTC)

The problem with climate change is that the current climate system has been relatively stable for a long period of time. Historical records of climate show that in transitions between different stable climate states, the system becomes highly chaotic and unpredictable before establishing a new equilibrium. So, while the current rate of carbon emissions is likely to lead to a warmer, on average, equilibrium climate conditions, the path to that new equilibrium state is likely to be a wild ride, and very unpredictable. Picture several centuries of unpredictable and wild climate swings, and that is part of the big problem. Its not that we can predict what will happen that is the problem. That would actually be less of a problem, because we could at least prepare for it even if we couldn't stop it. Its that we a) know its going to be crazy and b) can't predict what kind of crazy its going to be. The problem is that this is a complex problem which has been reduced by the popular media to "global warming" or "global cooling". Then people here scientists making both predictions, and think "they don't know what they are talking about, so we can ignore whatever the scientists predict." It might be better to think of it as "global climate clusterfuck." --Jayron32 01:30, 25 May 2010 (UTC)

Y'know, climate change could go different ways in different parts of the world, too (for instance, we could have global warming in Europe and Africa but global colding in North America, among many other possibilities). FWiW 67.170.215.166 (talk) 06:53, 25 May 2010 (UTC)

I think there is a consensus that if it somehow got so cold that the oceans froze over down to the equator, the resulting Snowball Earth state would be stable until CO2 built up to extremely high levels. I think there is also a consensus that a runaway greenhouse is not a real possibility -- CO2 levels have been over ten times higher in the past without producing such an effect. Looie496 (talk) 06:56, 25 May 2010 (UTC)

So there is no maximum temperature, and there is no minimum temperature??24.78.167.139 (talk) 07:12, 25 May 2010 (UTC)

Brewing yeast and fructose

What is the difference between yeast metabolism of glucose and fructose? Our yeast article only mentions fructose once. Specifically, I'm curious in brewing yeast whether fructose has the same conversion rate as glucose. Shadowjams (talk) 02:07, 25 May 2010 (UTC)

Most yeast uses glycolysis to convert sugars into energy (and alcohol). One of the early steps in glycolysis is the conversion of glucose-6-phosphate to fructose-6-phosphate. This reaction is easily catalyzed, and goes back and forth freely (glucose-6-phosphate isomerase is not a control point in glycolysis). The only difference between glucose and fructose utilization would be differences in efficiencies between going from free glucose to glucose-6-phosphate and free fructose to fructose-1-phosphate. -- 174.24.200.38 (talk) 04:32, 25 May 2010 (UTC)

Thank you for that, but I think glycolysis differs greatly from fructolysis and fructose-6-phosphate is quite different from molecular fructose. Do yeast have a fructolysis pathway? Shadowjams (talk) 05:37, 25 May 2010 (UTC)

Cats and newborn/infant humans

My wife and I have 4 cats and we are planning on adding a human soon. Could someone please help me find reliable sources regarding precautions and practices for newborns and cats? I am not asking for medical advice, I'm asking for help finding government health guidelines and the like - there is certainly a distinction. I'm already aware of toxoplasmosis - but that's the only reliable and well-sourced issue I can find. Help? 218.25.32.210 (talk) 03:19, 25 May 2010 (UTC)

The medical professionals you consult at various stages during the pregnancy will be able to give you advice on pets or at least tell you where to find that advice. I think they can do that better than we can. --Tango (talk) 03:22, 25 May 2010 (UTC)

When I was a baby our cat (Kitty Fisher) used to sit in my pram and guard me :) DuncanHill (talk) 07:40, 25 May 2010 (UTC)

if in future somebody makes a future predicting device/computer , what would be its concequences??? —Preceding unsigned comment added by 117.197.246.107 (talk) 10:03, 25 May 2010 (UTC)

is tyvek any better than nylon —Preceding unsigned comment added by Tom12350 (talk • contribs) 10:03, 25 May 2010 (UTC)

nylon

is tyvek any better than nylon