We can't really offer you advice about your symptoms, including offering a possible diagnosis or prognosis for your condition. If you are concerned about your health, you should speak to an appropriate professional. TenOfAllTrades(talk) 01:01, 18 May 2008 (UTC)[reply]

http://www.drivecarwithwater.com

DISCUSS. Namely, discuss whether or not this is possible, or if it's nothing more than a scam.

216.178.50.4 (talk) 01:33, 18 May 2008 (UTC)[reply]

No, it's crap. The hint is the mention of 'HHO gas'—some nonsense espoused by noted crank Ruggero Santilli. Note that it also fails the 'too good to be true' test. TenOfAllTrades(talk) 01:43, 18 May 2008 (UTC)[reply]

Took me 3 seconds to call the scam. Apart from everything else wrong with it, the question is if its that easy, why isn't everyone doing it? It would solve the worlds energy problems. Luxosus (talk) 01:51, 18 May 2008 (UTC)[reply]

It's possible, but it's still a scam. You require more electricity to split water into oxygen and hydrogen that you'd get more power out of the battery converted to motion if you used the battery to run the car directly. --Wirbelwindヴィルヴェルヴィント (talk) 02:03, 18 May 2008 (UTC)[reply]

Basically, a solely water-fueled car would be possible in a frictionless, lossless universe - but that's just silly. If the fuel starts out as water and ends up as water, no energy has been extracted, so you can't give the car any energy to accelerate or counteract drag. This sounds like a repeat of Stanley Meyer's water fuel cell. In fact, how are these guys even allowed to do this, in lieu of the precedent set by the court case against Stanley Meyer? --Bmk (talk) 02:48, 18 May 2008 (UTC)[reply]

Actually, I didn't really look at it carefully - I guess this is different - they're claiming to have a gas-water "hybrid" engine. They don't say how it might work, so I guess it's hard to comment about its validity. --Bmk (talk) 03:04, 18 May 2008 (UTC)[reply]

See also: Water-fuelled car. --Heron (talk) 09:59, 18 May 2008 (UTC)[reply]

Just thought, this would be the same (actually theoretically worse) than running a electric car directly from the battery used in a normal car wouldn't it? Luxosus (talk) 12:55, 18 May 2008 (UTC)[reply]

It's a complete scam - and several people who tried to make money from it wound up being found guilty in court as a result. Stanley Meyer is the most notorious - he was found guilty of "gross and egregious fraud" following his efforts to con investors out of large amounts of cash. The deal is that water is already in it's lowest possible energy state. There is no energy inside a water molecule - think of it like the ash that's left over after burning a piece of wood - the ash can't be burned any further...neither can more energy be extracted from water. Hence these machines have to put energy INTO the water to split it into hydrogen and oxygen - then burn the hydrogen in the oxygen to get some energy back. But nothing in the world can run at 100% efficiency - so you lose some energy in pulling the electricity out of the battery - you lose more energy as heat when converting water to hydrogen and oxygen - more energy is lost pumping the gas into the engine - and we know for sure that the engine isn't 100% efficient because no internal combustion engine ever can be. Then the energy that the engine produces has to be used to recharge the battery - but the generator/alternator loses energy - and when you recharge a battery, you lose energy. So through all of these lossy processes there is no way for the car engine to keep the battery recharged - let alone extract energy to drive the car. So these things are ALL scams - 100% certain - there is no wiggle room for cleverness because the laws of thermodynamics are cast iron scientific laws that cannot be breached. 66.137.234.217 (talk) 14:05, 18 May 2008 (UTC)[reply]

• 1) Was is the estimated weight of all the known and unknown universe, including all real and virtual matter and energy ?

• 2) What would the universe weigh if it was filled with milk or tomato soup ?

69.157.239.231 (talk) 13:01, 18 May 2008 (UTC)[reply]

Nobody knows the size/weight of the entire universe. What's more, in a sense nobody can ever know because it is so large that light has not had time to travel from the furthest extents to Earth since the big bang. Worse still, you can't talk about the 'weight' of something unless you know what the local gravitational field is - and that's different everywhere. Even 'size' becomes a tricky concept with curved space and the expansion of the universe. So to be able to answer this question in any way at all, I have to assume you are really asking about the mass of the known universe (the part we can theoretically see with telescopes). See Observable universe which says the diameter is 92 billion light years and the volume is 3×10⁸⁰ cubic meters with the total mass of everything within that volume being 3x10⁵³ kg. Since liquids like milk and soup are roughly as dense as water, and a cubic meter of water has a mass of 1000 kg, the mass of a ball of soup or milk the same volume as the known universe would be roughly 3x10⁸³ kg. Of course such an object would collapse under it's own gravitational field into a black hole leaving nothing but a feint smell of chicken and noodles. 66.137.234.217 (talk) 13:54, 18 May 2008 (UTC)[reply]

In response to question #2, given that most of our universe is empty space it would be alot more massive if the whole thing was filled with soup. And it would also be delicious. --Shaggorama (talk) 07:51, 19 May 2008 (UTC)[reply]

You might want to look at Orders of magnitude (mass). You definitely want to see mass instead of weight. This reminds of of a nursery rhyme about what if the oceans were filled with ink, but I can't place it... Sandman30s (talk) 14:17, 19 May 2008 (UTC)[reply]

How does a magnetic field exert a force? My thinking is it must be from an exchange of particles, similar to gravity and gravitons, however I've never heard of such a particle/theory. Luxosus (talk) 13:02, 18 May 2008 (UTC)[reply]

Photons transmit the electromagnetic force.--Shniken1 (talk) 13:14, 18 May 2008 (UTC)[reply]

That's just theory, however, and I don't buy it, as it requires an infinite number of photons to account for the magnetic interaction of every particle in the universe with every other particle. The same is true of gauge boson theory in general, however. StuRat (talk) 16:21, 18 May 2008 (UTC)[reply]

Well, I'm not fond of the photon-exchange picture either, and I don't think it makes sense at cosmological scales. It's probably better to think of an electromagnetic field (or a gravitational field) as something which is simply present in space and affects the motion of objects in regions where it's present. This is the usual classical picture, but it's also a correct quantum picture.

As for how the field exerts a force, here are a couple of possible answers.

1. It just does; we don't know why (yet). Hypothesis non fingo.
2. There aren't really any forces; the apparent forces are all really side effects of the geometry of spacetime, just like gravity. This is the idea behind Kaluza-Klein theory. It seems likely that something along these lines is correct, but it's too early to be sure. -- BenRG (talk) 19:17, 18 May 2008 (UTC)[reply]

The photon picture is perfectly plausible and consistent with all observations, such as small fluctuation in the electromagnetic force at small length scales. It does work across larger, even cosmological, scales and it does not require an infinite number of photons unless there are an infinate number of charged particles interacting. *Max* (talk) 21:23, 24 May 2008 (UTC).[reply]

If physicists were able to isolate the hypothetical graviton particle, what kind of energy would it give out ? Is this the point where we would have flying cars ? Could it help solve the issue of travel at light speed ? 69.157.239.231 (talk) 14:30, 18 May 2008 (UTC)[reply]

I don't think isolating it would be enough, you would need to be able to create them artificially. If you could that, then anti-gravity would probably be possible, and that would easily allow for flying cars. It might allow faster than light travel using wormholes, or something - currently theories for the creation of wormholes require exotic matter, which the ability to manipulate gravitons would probably help with. --Tango (talk) 14:58, 18 May 2008 (UTC)[reply]

A graviton would just be a gravitational wave, in the same way that a photon is just an electromagnetic wave. Maxwell didn't anticipate things like broadcast radio when he developed his theory of electromagnetic waves, and I suppose there might be non-obvious uses of gravitational waves as well, but offhand I can't think of anything. I don't see any way to use gravitational waves to make flying cars, but I do see a way to use electromagnetic waves for that: you just fire a sufficiently powerful laser beam downward from the car, and the light pressure will push it upward. But sufficiently powerful here means on the order of 10 trillion watts for a car of a couple of tonnes, so the laser will fry anything unlucky enough to be underneath the car, not to mention guzzle gas at a rate of around 100,000 liters per second. As usual, more prosaic technologies tend to work better in practice.

One big difference between gravitational and electromagnetic waves is that everything is transparent to gravitational waves. This is the main thing that makes them so difficult to detect—imagine trying to build a telescope using nothing but transparent materials, keeping in mind that the building housing the telescope is also transparent and "night" is no darker than day because the Earth is transparent too. And everything has refractive index 1, so you can't even make a lens. Nevertheless it is possible in principle (though extremely difficult) to do gravitational-wave astronomy, and this might be one use of gravitational waves, though not gravitons as such—they would allow us to "look" directly inside things that are opaque to light, like the Sun and the big bang primordial fireball. Neutrinos share some of these properties and might be useful in a similar way. We can already detect solar neutrinos and they do help in understanding stellar structure.

One could imagine, say, using gravitons (or neutrinos) instead of photons for broadcast radio and cell phones, thereby eliminating the problem of dropout when you drive under a highway overpass. But the detection (and even generation) problem is far too difficult for this to work in the real world. That's the closest thing to an application that I can think of. -- BenRG (talk) 17:14, 18 May 2008 (UTC)[reply]

DNA base letter representations. DNA bases can be represented by letters like A, G, T and C, but there are also other letters used to represent particular combinations of the other four (like, perhaps Y represents either G or A in a sequence). Where might I find a full list of these? ----Seans Potato Business 14:42, 18 May 2008 (UTC)[reply]

Why, you'd be looking for the list of degenerate bases. TenOfAllTrades(talk) 14:55, 18 May 2008 (UTC)[reply]

Indeed I would! Thank you, old sport! ----Seans Potato Business 16:57, 18 May 2008 (UTC)[reply]

Hi all,

I am planning on making a small wind turbine to generate 5-10V (probably a Savonius, but I don't think it matters for this question).

I have a number of used bicycle parts, such as gears and chains. I was trying to decide whether it would make any sense to have the generator separate from the turbine, connected by a chain, and had a couple of questions:

1. If we pretend that we have a 100% efficient, frictionless drivetrain (and a spherical cow...), would there be any advantages or disadvantages to having different gear ratios between the turbine and the generator (where the magnets and coils are)? Would any ratio deliver more volts for a given wind speed than a 1:1 would?
2. If there were some ratio better than 1:1, would this be enough to offset the real-world loss in efficiency caused by having a drivetrain? (I've read figures for losses of up to about 15% from using a drivetrain).

Any thoughts greatly appreciated, thanks! — Sam 15:34, 18 May 2008 (UTC)

The drive strength is proportional to the amount of wind, and the effectiveness of the turbine at converting a linear force to a torque. You want to spin the generator as fast as possible to generate the most amount of energy; and you want to maximize the turbine's ability to spin freely with a light wind. These two are conflicting desires - if you had a numerical description, you could find a maximum efficiency. I would be willing to guess that a small wind turbine will need to spin very freely in order to capture light breeze, so you may want the higher gear ratio on the turbine side, instead of the generator (e.g. 10 turns of the fan yields 1 turn of the generator). Nimur (talk) 15:55, 18 May 2008 (UTC)[reply]

I want to try to put a "finer edge" on Nimur's reply. I think what you're looking for is "maximum power coupling" between the wind and the electrical line feeding out of the generator. The gear ratio and the generator design doubtless have a big influence on that but I suspect you'll find that optimum gear rato varies depending in the wind speed, so you'll need to chose a ratio that hits some sort of "sweet spot" in the overall range of velocities. (I think the whole situation is strongly analagous to how matching the source and load electrical impedances in a circuit optimizes power transfer.) I also assume you'll actually be driving an alternator and not a direct current generator (even if you use bicycle parts). For that, you need the alternator spinning fast enough to overcome the relatively-fixed voltage drop that occurs in the rectifier diodes that convert the AC to DC. For larger alternators that use an electromagnet as their "field", you also gain another tuning parameter: by varying the current in the field winding (the "excitation"), you can vary the mechanical load that the alternator puts upon the wind turbine. And, of course, your design can't allow the wind turbine, alternator, or generator to "overspeed" (exceed its design limits) in any wind condition.

Atlant (talk) 13:37, 19 May 2008 (UTC)[reply]

(Thanks, I was having a hard time articulating my meaning!) Yes, the "optimum" gear ratio will vary based on the wind speed, so you should design based on expected wind speed. As Atlant says, it's very much like matching impedance. Nimur (talk) 03:28, 20 May 2008 (UTC)[reply]

A generator from a car with field coils (no magnets) needs to spin much too fast, use something with permanent magnets. Direct drive is good; theoretically if the voltage needs to be higher at a particular speed you can have more poles. I know a system like this that used direct drive, and then a voltage doubling electronics to charge a battery.Polypipe Wrangler (talk) 23:14, 19 May 2008 (UTC)[reply]

For economical dishwashing, does the reduction in efficacy of washing-up liquid necessitate re-filling of the sink once the bubbles have left the surface, or does this signify that the remaining capacity of the washing-up liquid has fallen below a certain percentage? I read that some surfactants don't even make bubbles. ----Seans Potato Business 16:28, 18 May 2008 (UTC)[reply]

Lack of bubbles means that all the soap is in the water instead of in the bubbles. It doesn't necessarily mean that all the detergent is bound up with food particles yet. If the dishes aren't coming clean, you can always just squirt a little more soap into the existiong water. Franamax (talk) 18:07, 18 May 2008 (UTC)[reply]

We are talking about manual dishwashing in a sink here, not using a machine, right ? Instead of adding dishwashing detergent to the water, I suggest you add a drop to each dish directly, so that all the detergent touches the dishes, which is better than the small portion of the detergent that the dishes touch when they are dunked in soapy water. You can then do a first rinse in the water under the dish you just washed and a second rinse in the water on the other side (I'm assuming a two-sded sink here, if you lack one, use a plastic tub for the primary rinse). If you really hate any detergent residue, you can rinse each dish a third time under the tap, but this wastes tap water. StuRat (talk) 19:12, 18 May 2008 (UTC)[reply]

Stu, the problem I see there is that the soap droplet will not disperse on the dry dish; there is no water-of-hydration to form the detergent micelles around the hydrophobic contaminants; and immersion of the dish in warm water will cause dispersal from the surface in any case. Proper consideration would also consider release of the detergent to the general environment, so excess detergent is also detrimental. Sloshing the dish around in the soapy water and using the dishcloth should give effective random contact of the "soil" and the detergent. Now that I think of it, pre-soaking of the dishes in cold water will give the best overall cleaning efficiency. Franamax (talk) 22:48, 18 May 2008 (UTC)[reply]

The best dishwashing efficiency is acheived by getting someone else to do the dishes. But, failing that, I heartily second Franamax's advice: pre-soak your dishes, preferably overnight. Most soil can then be easily removed with minimal effort, even stuff that seemed really hard-cooked-on the night before.

Atlant (talk) 13:18, 19 May 2008 (UTC)[reply]

However, I would discourage you from soaking dishes for much longer than 12 hours because all those yummy food particles will eventually promote the growth of bacteria in your dish water, which can be unhealthy. Dragons flight (talk) 14:22, 19 May 2008 (UTC)[reply]

Ahh, good point, but my thought would be to discard the "soak water" at the conclusion of the soaking period and then wash the dishes per your favorite usual method; ours is usually using a dishwasher. (And often, the "soaking" just means piling the dishes into a suitably-sized dirty pot/pan and flooding the pot/pan; almost by definition, that soak water then gets dumped prior to further washing-up.)

Atlant (talk) 17:32, 19 May 2008 (UTC)[reply]

I agree with the soaking advice. That's what I do myself, I just forgot to mention that part. Also note that a few drops of bleach can be added to the soak water to stop the nasties from growing, but don't do that if you have anything metal in there that could rust (including allegedly "stainless" steel). Wood may lighten but should be otherwise OK. Plastic is a good thing to bleach periodically. StuRat (talk) 18:56, 19 May 2008 (UTC)[reply]

What is considered to be the first primate species that evolved? Sorry if I demonstrate no understanding of this topic. 24.77.21.240 (talk) 17:01, 18 May 2008 (UTC)[reply]

No apologies are necessary. The topic of primate evolution is still quite debatable, despite it being a topic of rather intense research. So far as I can determine, this little fellow currently qualifies as one of the earliest primate or primate-like fossils found. Cute little fella, isn't he? I don't know why they gave him such a nasty name. Matt Deres (talk) 19:04, 18 May 2008 (UTC)[reply]

Cute? Little? What happened to respect for one's elders? :) Zain Ebrahim (talk) 19:13, 18 May 2008 (UTC)[reply]

Because the type specimen came from a site called Purgatory Creek, I believe. Presumably that's somewhere hot and unpleasant. 134.96.105.72 (talk) 11:41, 19 May 2008 (UTC)[reply]

That's a primate? Looks like a rat to me! I will never understand how biologists classify animals - seems like picking names out of a hat, half the time! ;) --Tango (talk) 21:12, 18 May 2008 (UTC)[reply]

Primates are most closely related to rodents, among the other large mammalian orders. What the paleontologists mean (and classification of extinct species is quite different from classification of living species) is that ancestors of primates at the point in time in which primates began to separate from rodents (at which time, yes, they all pretty much looked like rats) were more like Purgatorius than they were like the other protorodents running around at the time. It's true, Purgatorius doesn't look much like a primate, but every other mammal alive in its time (that we know about so far) was even less primate-like. arkuat (talk) 21:25, 18 May 2008 (UTC)[reply]

Actually, this is still in question. Some believe primates are closer to bats than rodents; see Archonta (the classification that puts bats closer) versus Euarchonta (the classification that thinks rodents are closer). (There is also a proposal that bats are not monophyletic, and that the Megachiroptera are very close to, or even nested within, primates while the Microchiroptera are distantly related.) Vultur (talk) 22:05, 18 May 2008 (UTC)[reply]

It's not really still in question, I think. The association of megachiropters with primates was primarily due to similarities in visual pathways (i.e. they see in similar ways), but all the genetic studies since that theory was floated have pointed to the monophyletic system (i.e. all bats share a common ancestor). The supposed similarities are more likely due to convergent evolution, which makes sense as they developed to perform the same kind of thing. Matt Deres (talk) 02:19, 21 May 2008 (UTC)[reply]

Very interesting! I guess I should stop thinking of Chiroptera as a small mammalian order compared to Primates and Rodentia. arkuat (talk) 02:23, 19 May 2008 (UTC)[reply]

What is the primary reason large wind turbines used for power generation typically have very few blades, which move slowly? Is it for power conversion efficiency? Ease of construction? Safety for the turbine itself and the humans near it? Safety for birds? --71.162.233.156 (talk) 17:51, 18 May 2008 (UTC)[reply]

Cost, I imagine. Putting too many blades on will start needing pretty heavy-duty bearings in the turbine. The blades seem to rotate quite slowly, but the tips are actually moving very fast, ~100 mph If I recall. Franamax (talk) 18:00, 18 May 2008 (UTC)[reply]

There also is aerodynamic efficiency. Rotor blades will cause turbulence. Putting to many too close together will actually be counterproductive. The same is true if you spin them too fast. As far as I know, they are constructed to spin at an approximately constant speed (which will also be the speed that the generator is optimized for), which is regulated by adjusting the load on the generator. See wind turbine for more. --Stephan Schulz (talk) 18:14, 18 May 2008 (UTC)[reply]

I'm pretty sure that rotation speed is also regulated by adjusting the pitch of the blades; at least, I've seen some that appear to have pivoting blades. ~Amatulić (talk) 21:36, 19 May 2008 (UTC)[reply]

I believe I've read that the newer, larger-but-slower designs also minimize the problem of bird mortality near the wind turbines.

Atlant (talk) 13:14, 19 May 2008 (UTC)[reply]

They don't move slowly, they are just so large that the rotation rate becomes low for a given speed of the blade tips. The tip speed is actually close to the speed of sound. (It is held below the speed of sound to avoid the messy and lossy aerodynamic effects that would kick in if they went supersonic.) --169.230.94.28 (talk) 18:54, 19 May 2008 (UTC)[reply]

Um, no, I don't think so. Here's a typical example: [5] 33m diameter, 50 rpm gives a blade tip speed of 125 m/s, far below the speed of sound in air (about 346 m/s). Still 125 m/s is pretty fast (about 280 mph). ~Amatulić (talk) 21:36, 19 May 2008 (UTC)[reply]

The slowly rotating wind generators are able to generate 60 Hz (or 50 Hz, depending on the country) power by having a great many poles in the windings, so that one rotation produces many cycles of electricity. Edison (talk) 19:59, 19 May 2008 (UTC)[reply]

How powerful would a bomb using sub-nuclear particles be ? Say, a neutrino bomb ? Or a muon bomb ? A hadron bomb ? Or even graviton bomb ? What would that look like ? 69.157.239.231 (talk) 18:18, 18 May 2008 (UTC)[reply]

• I can't see any way to make a bomb out of such things. Neutrinos barely interact with anything, so you certainly can't build something with them. And I can't see how muons or gravitons would bind together, either. Hadrons include regular atomic nuclei, though, so you can just build a normal nuke. --Tango (talk) 18:31, 18 May 2008 (UTC)[reply]
• (edit conflict)This question is not really well-posed. An atom bomb goes boom because certain nuclear reactions generate net energy, not because of the size of the particles. It's unclear which sub-nuclear reactions would provide energy. Neutrinos don't really interact much with anything, so a neutrino bomb is somewhat pointless. All particles made up of quarks are Hadrons, so everything from a China cracker to an antimatter bomb could be described as a hadron bomb. --Stephan Schulz (talk) 18:37, 18 May 2008 (UTC)[reply]

I think the intent of the question is this. An ordinary chemical explosion releases energy stored in chemical bonds (between atoms in a molecule). A nuclear fission explosion releases energy stored in the bonds between nucleons in an atom. What would a bomb that broke the bonds between quarks in a nucleon be like? —Preceding unsigned comment added by Vultur (talk • contribs) 22:11, 18 May 2008 (UTC)[reply]

There is the problem that this appears to be more or less impossible. See color confinement. Algebraist 22:21, 18 May 2008 (UTC)[reply]

As I understand it, bonds actually reduce the energy stored in a molecule/nucleus - a bomb exploits the energy released when new bonds form. Basically, you need to go from a high energy state to a low energy state, and the difference is what goes bang. As Algebraist points out, separate quarks is not a lower energy state than a nucleon (in fact, it's not an achievable state at all). It might be possible to convert mesons to baryons, or vice versa, and get energy that way. I'm not sure what the bind energies are for such things, or even if there are combinations that would work. --Tango (talk) 23:25, 18 May 2008 (UTC)[reply]

Take a look at Energy density—it basically tells you what sorts of things would make a good bomb (or, put another way, a good bomb is something that can release a large amount of energy in a very limited amount of space or time). The only thing that really is more impressive than nuclear fusion (in a thermonuclear weapon) are pure matter-antimatter interactions. --98.217.8.46 (talk) 15:15, 19 May 2008 (UTC)[reply]

What about using the w boson to catalyze a fission reaction via beta decay? convert a neutron to a proton which then makes the atom unstable?--75.20.225.74 (talk) 18:09, 18 January 2010 (UTC)[reply]

Would it be possible to increase the efficiency of a home generator (whether gasoline, propane, natural-gas powered, etc.) by using the excess heat produced to run an extra steam-powered generator ? I'd design it to have an expandable tank so it wouldn't split if the water freezes in winter. The water tank would have a hose attachment so you could hook a regular garden hose up to it to provide the water. I'd also design it so that the cooling fins in the water would air-cool the device when the water runs dry. I realize that scale from the minerals in the water would eventually build up on the fins, but for a generator only used for emergencies, this may not happen for decades, and the fins could always be cleaned. StuRat (talk) 18:46, 18 May 2008 (UTC)[reply]

This is confusing. If it's only for emergencies, why would you care about efficiency? However, you could capture excess heat in a combined cycle, although maybe just using it as a source of hot water instead of steam would be more practical. There's also the question of how to capture the heat. If you use an enclosure to capture the heat, when the water ran dry, wouldn't you have an empty enclosure with non-circulating air, thus no cooling function whatsoever? Franamax (talk) 19:01, 18 May 2008 (UTC)[reply]

Also, beware if you're going to play around with pressurized steam, that's called a boiler, needs certification, and can burn you real good. Franamax (talk) 19:01, 18 May 2008 (UTC)[reply]

I'm no expert but I'd apply Occams Razor here (in a sense). Rather than try and power a steam generator from the excess heat, find a way to use the heat more directly. Exxolon (talk) 19:15, 18 May 2008 (UTC)[reply]

The point of the efficiency is to get more energy out of a given sized generator. You could design the pressure tank out of metal with fins so that any heated air inside would heat the tank and dissipate heat into the environment. However, to make the tank be able to withstand freezing water, I wouldn't make the tank entirely out of metal, but also include flexible materials. As for any boiler requiring certification, certainly a tea kettle doesn't require an inspection, and it's actually inside the home, so their must be some lower limit on size and pressure, below which an exemption exists. StuRat (talk) 19:24, 18 May 2008 (UTC)[reply]

As I and Exx have said, the best way to get more efficiency is probably to make hot water, not steam. Your heat dissipation plan is OK, but you are introducing an extra stage, metal->air->metal->air, whereas the generator is designed for single-stage metal-to-free air cooling. You will drastically decrease the cooling efficiency if you are dissipating heat into confined air. As for the boiler, I'll look at Ontario TSSB requirements, but basically a kettle is releasing steam into free air, you are talking about confining the steam until it is sufficiently pressurized to do meaningful work, I can pretty much guarantee you that under those circumstances an accidental release will burn you very badly. I'll look around though. Franamax (talk) 21:07, 18 May 2008 (UTC)[reply]

Per TSSA (they changed the letters), you are talking about a "low pressure boiler" since you will presumably have < 30 sq.ft. of wetted surface, or <160 psi and <10 sq.ft. surface, so go nuts. Everything else about cooling efficiency and severe burns still applies though. Good luck :) Franamax (talk) 21:21, 18 May 2008 (UTC)[reply]

The problem is that to extract useful energy you need a big temperature differential. It's quite easy to extract energy when there is a 100 degree temperature difference - but it's really hard when there is only a 1 degree difference. In this case, instead of attempting to turn your relatively low grade temperature differential first into motion, then into electricity and then into something useful - why not use the heat directly. For example, you could take a cool water feed from the bottom of your home hot water tank, run that off to the generator - wrap the hose around the hot exhaust a few times and then back up to the top of your hot water tank. Since hot water is less dense than cold, the water should flow around the loop without being pumped - and your hot water tank will gradually heat up. If you normally heat your water with electricity - then the electricity savings should be a lot more than all of that messing around with steam engines could posibly get you.

70.116.10.189 (talk) 11:42, 19 May 2008 (UTC)[reply]

Actually, StuRat, I've seen this done in other areas. For example, in my line of work I saw a demonstration of using the heat from a vehicle's exhaust to generate electrical power using a Peltier effect hot-cold plate. In another example I saw an experimental pickup truck converted by NASA to run on a stirling engine, which merely needs a heat differential, and which could run an electrical generator. I'd say (just guessing) that various thermoelectricity methods might be more efficient than a steam engine. ~Amatulić (talk) 21:45, 19 May 2008 (UTC)[reply]

A common setup is to run a battery charger from the generator as well as the usual load. Then, later, when the generator is off run some things off the battery. Especially useful with generators that require a minimum loadPolypipe Wrangler (talk) 23:20, 19 May 2008 (UTC)[reply]

I remember seeing an old a for a small gas engine for use on farms before rural electrification. The motor, progagby under 1 horsepower, could be rolled around like a wheelbarrow, and could quickly be hooked up via drive belt for various applications. First, it could be hooked up to a generator to produce 32 volts DC or so to charge up batteries to light the home. When the batteries were charged, it could be wheeled over to the pump to pump the days water up into the water tower. Then it could be wheeled out by the barn to run a conveyor belt to lift bales of hay up into the hayloft, or to run a buzzsaw to cut firewood, etc, etc. Such an engine might have a water reservoir for cooling and the water sinply boiled away, but it could have been used to heat up water for the wash, if the timing were right. Edison (talk) 14:03, 21 May 2008 (UTC)[reply]

Ok, thanks for the answers everyone. StuRat (talk) 02:41, 20 May 2008 (UTC)[reply]

I heard there was a place in the super-galaxy called the neutrinosphere, where the surface is heavily blanketed by neutrino particles. What's the point of such a zone ? Does it hold the galaxies together ? 69.157.239.231 (talk) 18:58, 18 May 2008 (UTC)[reply]

I'm not sure whether you're talking about dark matter (or, even less likely, dark energy) or about something else entirely. I don't think a surface heavily blanketed by neutrino particles is physically possible, though, except momentarily inside stars going supernova, thermonuclear weapons exploding, and that sort of thing. Dark matter does help hold our galaxy together gravitationally, certainly: that's how it was discovered. arkuat (talk) 20:54, 18 May 2008 (UTC)[reply]

A neutrinosphere is a transient region within a supernova explosion where neutrinos exist in thermal equilibrium. It has nothing specific to do with galaxies. Dragons flight (talk) 22:15, 18 May 2008 (UTC)[reply]

Could neutrinos form a pool in a gravity field is a question I have been asking myself. However even with the very cold Cosmic neutrino background at about 1.9 K they are moving much faster than the escape velocity of the earth. How fast they move depends on their mass, which could be around 0.01 eV. Perhaps in the centre of galxies or near white dwarfs, the gravity may be strong enough to retain these neutrinos in a closed orbit. But more likely the neutrino will fall in to the gravity well, speed up and then shoot out the other side in a hyperbolic orbit and not slow down! Graeme Bartlett (talk) 22:13, 19 May 2008 (UTC)[reply]

I believe neutrinos generally travel at just short of the speed of light, so this is very similar to the question above about light in gravitational fields. You would need something close to a black hole to get neutrinos to orbit - the centre of a galaxy would qualify. Near neutron stars might work, white dwarfs probably not (but possible, I'd have to look up some figures to be sure). I'm not sure what you mean by "form a pool", though, pools form when gravity is resisted by contact with something (the ground, say), but neutrinos would pass straight through pretty much anything, so they can't form pools. --Tango (talk) 23:27, 19 May 2008 (UTC)[reply]

The resistance comes about from Pauli exclusion principle whereby fermions cannot occupy the same quantum state. A sufficient accumulation of cool neutrinos would start to resist each other's presence rather than just passing through each other. This is the same principle that keeps atoms apart. The speed of the CNB would be around 10⁷ meters per second, which is fast exceeding escape velocity of the sun or earth.

As far as I can tell, that accumulation would have appear as if by magic. Once you've got it, it can stop new neutrinos and grow, but I can't see how it can form in the first place. --Tango (talk) 11:59, 20 May 2008 (UTC)[reply]

This is perhaps more of a history of science question, but I expect the people here will probably be more helpful than the good folks at the history desk. I've already read the Ephemeris Time article and several other related articles and hope to add any information I get from the answers to this question to that article. ET and TAI are offset from one another by 32.184 seconds, because that was how far ET and UT had diverged from one another at the time that TAI was defined (1958) and in turn began its own divergence from UT. I already understand about leap seconds and that UT is not and cannot be a regular scale of time, and why it can't be.

What I want to know is when was ET adopted? Using a rough estimate of 0.7 seconds per year divergence between an ET clock and a UT clock, it looks as if the divergence began around 1912 or so. (That's 32.184 s divided among the 46 years from 1912 to 1958.) Can I get some historians of science to help me pin this down more precisely, and perhaps help me find the appropriate proceedings of the IAU (or whatever the IAU's predecessor was)? --arkuat (talk) 19:29, 18 May 2008 (UTC)[reply]

The Russian version (ru:Эфемеридное время) claims the decision was made in 1952 (8th General Assembly of IAU) with the "starting point of the time" chosen to be 1900 January 0. --Martynas Patasius (talk) 23:04, 18 May 2008 (UTC)[reply]

Thanks! So sometime between 1890 (?) and 1952, ET came into use, and became well-established enough at some point to have a statable divergence from UT, which divergence was not defined and fixed by international agreement until 1952, at which point the divergence was backdated to 1900. I am reminded now of Simon Newcomb#Director of the Nautical Almanac Office, which doesn't state any of this clearly, but hints at some of it. arkuat (talk) 02:13, 19 May 2008 (UTC)[reply]

Ephemeris Time (ET) was so named because it was the independent time scale used in government ephemerides from 1900 through 1983, in the American Ephemeris and Nautical Almanac, the British Nautical Almanac and Astronomical Ephemeris, the French Connaissance des Temps, the German Astronomisches Jahrbuch, and the Spanish almanac. ET was defined (but not named) by Simon Newcomb in 1895/98 as the weighted average of mean solar time refered to the Royal Observatory, Greenwich between 1750 and 1892. It was implemented at Greenwich mean noon on 31 December 1899 (0 January 1900), meaning that from that date on the stated positions of the planets in the ephemerides would be calculated in terms of ET, not in terms of Greenwich mean solar time (named UT in 1928) which had been used before 1900. ET differs from UT quadratically, not linerally, that is, the difference is generally a parabola. See ΔT. However, this divergence was not recognized in 1895, instead its implemention included a "great emperical term", a sinusoid with a period of 257 years. — Joe Kress (talk) 08:09, 19 May 2008 (UTC)[reply]

Thanks, Joe. I hope you don't mind that I've copied your entry here to Talk:Ephemeris time, because I think several of the points you make ought to be incorporated into the text of that article. arkuat (talk) 21:32, 20 May 2008 (UTC)[reply]

How would one convert ${\displaystyle yd^{2}in}$ to ${\displaystyle yd^{3}}$? Thanks, Zrs 12 (talk) 19:47, 18 May 2008 (UTC)[reply]

I have no idea what it means but does this help? Zain Ebrahim (talk) 20:04, 18 May 2008 (UTC)[reply]

Divide by 36. You might measure the amount of rainfall that lands on a rood in ${\displaystyle yd^{2}in}$, and the amount of water that this added to a cistern (via the gutters) in ${\displaystyle yd^{3}}$.-Arch dude (talk) 20:31, 18 May 2008 (UTC)[reply]

Indeed, divide by 36. All you actually need to do is convert inches to yards, the yd² can just tag along for the ride. --Tango (talk) 21:10, 18 May 2008 (UTC)[reply]

What puzzles me most about this question is why the OP asked it - given his user page. Richard Avery (talk) 06:46, 20 May 2008 (UTC)[reply]

Cut the kid some slack. Just because you are interested in complex topics doesn't necessarily mean you are great at them (no offense Zrs). According to his user page, he's a HS freshman. --Shaggorama (talk) 05:57, 21 May 2008 (UTC)[reply]

What is Spontaneous activation? And how it works in oocytes? —Preceding unsigned comment added by 131.220.58.9 (talk) 20:23, 18 May 2008 (UTC)[reply]

Activation of the oocyte genome is mentioned in Folliculogenesis#Primary. There's not much there, but I hope this helps. arkuat (talk) 21:05, 18 May 2008 (UTC)[reply]

Hi there:
Since last night, I couldn't logon my computer anymore. Every time after I typed the password,
the system will be shut down automatically and a blue screen popps up with some notes on it:

 STOP: c000021a {Fatal System Error}

 The windows Logon process system process terminated unexpectedly with a status of

 0xc0000005 (0x00000000 0x00000000).

 The system has been shut down. 

It all happened after the latest automatic update of Window XP. This kind of thing never happened
before since I have been using McAfee for more than 10 years to protect our
computer. Could that be a virus? Do you expert think so? Please help me out of this.

--Wendyzh (talk) 22:10, 18 May 2008 (UTC)Wendyzh[reply]

• [6] might help. I have no idea what the cause is, but that explains how to fix it (it's not easy, though - you may need to call your neighbourhood geek, every neighbourhood has one!). --Tango (talk) 22:24, 18 May 2008 (UTC)[reply]
• (edit conflict): I don't know if this is the right place for this question, but a lot of people had trouble with their computers after they instralled Service Pack 3. Apparently, there is some trouble with OEM versions, drivers, and (especially) AMD processors. You might want to upgrade to Linux. If you want to stick with Windows (why?), this site might help, and has further links into the Microsphere. --Stephan Schulz (talk) 22:26, 18 May 2008 (UTC)[reply]

• Try asking here :) Regards, CycloneNimrod^Talk? 22:39, 18 May 2008 (UTC)[reply]

Yup, it sounds like Service Pack 3 is the culprit, from the description and the news I've been reading. On the other hand, it could be a coincidence with a dirty cpu heat sink. I've had my computer shut down by itself when the heat sink cooling fins got too clogged. ~Amatulić (talk) 21:48, 19 May 2008 (UTC)[reply]

How do I find out which genes flank TJP1 in humans? I figure one of the many genomic databases would be able to help but they're terribly complicated and intimidating. ----Seans Potato Business 21:04, 11 May 2008 (UTC)[reply]

On the link you provided, scroll down to the section Genomic context. This will tell you the chromosome the gene is present on and it's location. By searching the position before it or after it should give you your answer. Regards, CycloneNimrod^Talk? 21:11, 11 May 2008 (UTC)[reply]

Its actually a bit complicated this one. However, 5' of TJP1 appears to be necdin-like 2, while 3' is CHRNA7-FAM7A fusion isoform 1 (which is a very odd locus). There may be other genes in between, but they have not been characterized. Rockpocket 21:53, 11 May 2008 (UTC)[reply]

How did you get those? ----Seans Potato Business 21:59, 11 May 2008 (UTC)[reply]

Okay, this isn't working. I'd like to know in which order the genes TJP1, NDNL2, GREM1, SLC12A6 and SPRED1 occur. I know they're in the same region, but I want to determine if there are any genes between them and in what order the occur. If I search for each gene I get:

ndnl2 15q13.1

slc12a6 15q13-15

tjp1 15q13

grem1 15q13-15

spred1 15q14

Yet none of these shows up on the 'genomic context' diagram of any of the others. How can I interpret this mess? Does SPRED1 exist on an exon inside both GREM1 and SLC12A6 which both exist in exons of each other? I suppose one may be on the antisense strand, but there's going to be overlap somewhere here. ----Seans Potato Business 21:55, 11 May 2008 (UTC)[reply]

According to Ensembl (by searching for each gene on the human genome):

• Ndnl2.. can be found on Chromosome 15 at location 27,347,645 - 27,349,325 and is anti-sense.
• Tjp1.... can be found on Chromosome 15 at location 27,778,863 - 27,901,998 and is anti-sense.
• Grem1.. can be found on Chromosome 15 at location 30,797,497 - 30,814,158 and is sense.
• Slc12a6 can be found on Chromosome 15 at location 32,309,489 - 32,417,557 and is anti-sense.
• Spred1. can be found on Chromosome 15 at location 36,331,808 - 36,433,526 and is sense.

Are there intervening genes? Yes in all cases, except between Ndn12 and Tjp1. Rockpocket 22:35, 11 May 2008 (UTC)[reply]

Okay, this is really helpful of you. Thanks. However, now I have a conflict; SPRED1, according to this is at 15q14 while GREM1 according to this is at 15q13-15. If 15q13-15 means 15q13 to 15q15, then why do those numbers you (kindly) provided not overlap? And how did you find out whether they were sense or anti-sense? --Seans Potato Business 22:48, 11 May 2008 (UTC)[reply]

The "q" refers to chromosome regions while the numbers (13-15) refer to cytogenetic bands identified by staining. That nomenclature is an old skool way of positioning genes on chromosomes and is not particularly accurate. Now we have a fully sequenced genome we can precisely identify exact positions of genes. In this case 15q13-15 means that Grem1 resides somewhere within bands 13-15, rather than meaning it spans that huge length. I used Ensembl to find the info, and identified the strand from that. For example, have a look at the diagram on the TJP1 page, under the "transcripts" sub-section. Find the thick blue line that says "DNA (contigs)". Now any gene identified above that line is on the forward strand (sense orientation) and any genes under that line is on the reverse strand (anti-sense). TJP1 is directly underneath the line, therefore it is anti-sense.

If you don't wish to use Ensembl, the NCBI site you were using gives the same info. On the Spred1 page, on the right hand side of the "genomic context" section there is a link to "See SPRED1 in MapViewer" If you follow that link [7], you can see that the Spred1 gene is located on the right hand side vertical line spanning roughly the same distance I provided (36331k to 36433k). If you want exact values, you can always zoom in by clicking on the gene. Note also the little black arrow beside the Spred1 gene name. The arrow points downwards, indicating the gene is on the sense strand. If it was to point upwards, you would know your gene of interest was anti-sense. Rockpocket 01:22, 12 May 2008 (UTC)[reply]

Just a couple more questions: how did you know that the little black arrow next to the gene name corresponds to sense/antisense? And, if we are able to define more precisely where a gene is located, why still quote 15q13-15 and not 15q13 or whatever? ----Seans Potato Business 22:32, 18 May 2008 (UTC)[reply]

Well I knew that something would indicate the direction of the gene and the arrow seemed a good candidate. So I checked to see if it was consistent with direction, and it does. Why quote the less detailed banding values? Probably because that page is only partially manually curated. A paper probably described the general position some time ago and no one has bothered to update the record with the exact position. Rockpocket 05:50, 20 May 2008 (UTC)[reply]

what part of the brain controls the pacemaker in your heart? (the real pacemaker-not an artificial one) —Preceding unsigned comment added by 97.115.18.248 (talk) 02:58, 19 May 2008 (UTC)[reply]

It's modulated by the autonomic nervous system, however the pacemaker cells of the sinoatrial node do not require any input from the CNS to induce the heart beat. Wisdom89 _{(T / ^C)} 03:12, 19 May 2008 (UTC)[reply]

More specifically, the Vagus nerve is a parasympathetic cranial nerve that slows the rhtyhm of the heart at the SA node when stimulated. It descends form the brainstem, which is evolutionarily the most primitive part of the central nervous system. I'm not entirely sure how/if sympathetic ennervation occurs directly in the heart. The brain also commands the heart indirectly by orchestrating the release of hormones that have a global effect on the body, such as epinephrine. --Shaggorama (talk) 08:06, 19 May 2008 (UTC)[reply]

Since you mentioned it, sympathetic innervation impinges on the sinoatrial node, the AV node, as well as the myocardium itself to increase the speed of conduction, as well as the contractility of the ventricles. Wisdom89 _{(T / ^C)} 17:43, 19 May 2008 (UTC)[reply]

Can birds fluff up their feathers at will, or is it just a reflex response to cold? —Preceding unsigned comment added by 84.66.70.50 (talk) 08:46, 19 May 2008 (UTC)[reply]

Both. Birds fluff up their feathers to trap air between then to act as an insulator. This is probably an automatic response, but they most defiantly can do it at will also. Have a look at this similar question. They sometimes also fluff them up when preening, to ensure they clean every layer, or to appear bigger to an opponent. Think outside the box 11:18, 19 May 2008 (UTC)[reply]

And often as a courtship ritual. --jpgordon^∇∆∇∆ 13:32, 19 May 2008 (UTC)[reply]

Swans carry their baby chicks in their feathers on their back when the chicks feathers are not water proof to swim yet. Bed-Head-HairUser:BedHeadHairGirl12:56, 20 May 2008 (UTC)[reply]

I am doing some reserch into solar power and its generation. I have searched companies and websites and find that they use SILICON FEEDSTOCK to manufacture solar cells. However none explain what the silicon feedstock is or the raw materialand processes used to manufacture the feed stock.

I would be grateful for any guidance.

Many thanks

Kusum Thanki —Preceding unsigned comment added by KusumThanki (talk • contribs) 10:44, 19 May 2008 (UTC)[reply]

One way to gather energy from the Sun is to use photovoltaic cells - these are just silicon chips (like computer chips). The raw material for making them is super-pure silicon. So the 'feedstock' for that manufacturing process is silicon which is purified, cast into cylinders then sliced to form 'wafers' onto which the circuitry is printed and etched. Silicon is a very common element - it makes up 25% of the earth's crust so it's everywhere around us. I believe that it's extracted from sand using coal or charcoal and then purified. Our article Silicon covers that fairly well. 70.116.10.189 (talk) 11:28, 19 May 2008 (UTC)[reply]

The silicon isn't cast into a cylinder; rather, a boule of silicon is grown using the Czochralski process. It's a time-intensive process which is one of the reasons why the silicon raw material is so expensive. (And because the boules are cylindrical, they slice out to form those inconveniently-shaped (rather area-wasteful) circular silicon wafers.) For a contrast, see amorphous silicon.

Atlant (talk) 13:00, 19 May 2008 (UTC)[reply]

how is it possible for the continents to move? what are the consequences of drifting continents? what evidence exists to prove drifting continents? which hazards and opportunities result from continents on the move? if we stand on the beach,will we see how the land is moving?why? how fast is this movement? —Preceding unsigned comment added by 196.35.246.194 (talk) 13:58, 19 May 2008 (UTC)[reply]

I suggest reading the Plate tectonics article, and come back if you have any more questions. -- JSBillings 14:00, 19 May 2008 (UTC)[reply]

And Continental drift...--Cameron (t|p|c) 18:13, 19 May 2008 (UTC)[reply]

Do you know the technic of mastubate? —Preceding unsigned comment added by Aku orang ganteng (talk • contribs) 14:12, 19 May 2008 (UTC)[reply]

You are no doubt looking for our article on masturbation. For further advice, speak to a medical professional. TenOfAllTrades(talk) 15:03, 19 May 2008 (UTC)[reply]

Most likely a Sex therapist Nil Einne (talk) 18:07, 19 May 2008 (UTC)[reply]

If I want to sequence a length of DNA, why would I amplify by PCR and then clone into a vector for amplification within bacterial cells? Why can't I just use PCR for the amplification? What's the plasmid step all about? This is an example on such vector used by a research group whose paper I'm reading, before sequencing: "PCR products were cloned into plasmid vectors using the Topo TA cloning kit (Invitrogen, Carlsbad, CA, USA) following the manufacturer’s instructions. Five positive clones were purified from each test cell line using the Wizard Plus miniprep kit (Promega), and were then sequenced by the Applied Biosystems PRISM dye terminator cycle sequencing method" ----Seans Potato Business 15:55, 19 May 2008 (UTC)[reply]

These pages discuss some of the pros and cons of direct sequencing of PCR products. Direct sequencing of PCR products is much faster, but is prone to a number of pitfalls for the unwary experimenter. TenOfAllTrades(talk) 16:14, 19 May 2008 (UTC)[reply]

If there a substance that turns liquid at about the same temperature as wax but that is not flammable? —Preceding unsigned comment added by Taxa (talk • contribs) 17:07, 19 May 2008 (UTC)[reply]

Many solders might fit your description, but they're metallic, if that makes a difference. I suspect most non-metallics that melt at a reasonably low temperature are flammable to one degree or another, although the addition of flame retardants might affect that.

Atlant (talk) 17:26, 19 May 2008 (UTC)[reply]

Metallic again: Gallium, caesium, rubidium, francium. Rmhermen (talk) 22:14, 19 May 2008 (UTC)[reply]

Rubidium and francium will auto ignite in air, and most definitely are flammable. In the presence of a heat source, caesium might as well. Dragons flight (talk) 22:20, 19 May 2008 (UTC)[reply]

Low melting point solders melt at 90C, Wax melts at around 45C - so we need to do better than that. I can't think of anything that melts around 45C. The nearest that I'd suggest would be the plastic Polycaprolactone (sold in hobby stores as "Polymorph") which melts at 60C - but I don't know how flammable it is. Field's metal melts 62C, Wood's metal at 70C. Lipowitz's Alloy at 73C. Field's metal is relatively safe - but Wood's and Lipowitz's metals are toxic - so beware! More exotic: Rubidium melts at 40C and white Phosphorus at 44C...neither could be remotely described as "not flammable" though! Gallium might work - it melts in your hand at 30C and is thought to be non-toxic (although it's kinda tough to get off your hands)...but it'll melt at high room temperatures too! 70.116.10.189 (talk) 22:31, 19 May 2008 (UTC)[reply]

Let's back up a tick here...what's the application you have in mind for this material, and how "non-flammable" do you need (will be exposed to flame, vs will be heated strongly, vs just general safety concerns)? Is toxicity a concern? DMacks (talk) 22:42, 19 May 2008 (UTC)[reply]

Silicon based waxes would fit the bill. See Silicone oil --Shniken1 (talk) 23:18, 19 May 2008 (UTC)[reply]

Anything waxy with many halogen atoms in it would not burn, see flame retardant. Cacycle (talk) 01:10, 21 May 2008 (UTC)[reply]

Supposing one already owned the necessary hardware, how much would it cost, in terms of consumables, to sequence a sample of say, 200 basepairs? ----Seans Potato Business 20:27, 19 May 2008 (UTC)[reply]

To get an exact figure, you should pull out your Fisher Scientific/Sigma/Qiagen catalog(s) and look up exact costs for each item needed.

If you Google core sequencing facility or something similar, you'll be able to find price lists for various university labs, including the prices that they charge for internal academic users. Prices I've seen for a single sequencing reaction range from about 5 USD to 15 USD; some discounts are offered for large sample runs. Depending on how those core facilities are funded and subsidized, those figures probably represent a maximum cost of materials, but likely also include some amount of technician time and amortization of equipment costs.

In other words, the cost of sequencing a single 200 bp sample is trivial. TenOfAllTrades(talk) 20:44, 19 May 2008 (UTC)[reply]

Just from personal experience, DNA sequencing facilities typically charge customers between 6 and 12 U.S dollars per sample. This includes the reaction and the electrophoresis. Wisdom89 _{(T / ^C)} 20:45, 19 May 2008 (UTC)[reply]

Why Apples Iphone is such a success? why Microsft cant better than it, is microsoft techinally behind or something else —Preceding unsigned comment added by 198.109.30.86 (talk) 21:42, 19 May 2008 (UTC)[reply]

This isn't really a science question. Anyway, Microsoft has a long history of not leading, but rather entering a market segment only after an idea or product becomes successful, and then doing it (or marketing it) better. Internet Explorer, XBox, Zune, Microsoft Office... just wait. You can bet they aren't planning to cede the smart phone market to Apple. ~Amatulić (talk) 21:51, 19 May 2008 (UTC)[reply]

Microsoft is principly a software company, there are already phones which run windows mobile (I have one). Microsoft is more than willing to allow other companies to make the hardware while they write the software, but that doesn't mean they won't put out a phone built entirely in-house in the future. -- Mad031683 (talk) 23:29, 19 May 2008 (UTC)[reply]

Simple answer : Because Microsoft does not make phones. APL (talk) 17:56, 20 May 2008 (UTC)[reply]

More specifically, they don't make smart phones - I believe they're waiting until the market is bigger. They didn't make PDAs until Palm Pilots dominated that market. They didn't make portable music players until Apple iPods dominated that market. They didn't make video game consoles until fairly recently either. That was my point above: Microsoft innovates in the direction of already-existing BIG markets. Smart phones aren't yet dominant players in terms of total cell phone market penetration. Time will tell if Apple's iPhone and RIM's BlackBerry and other smart phone products become popular enough to spur Microsoft into selling similar hardware. ~Amatulić (talk) 18:18, 20 May 2008 (UTC)[reply]

Next time anyone wants to ask a question like this, there's a computing page for that purpose. 12:00, 21 May 2008 (UTC) —Preceding unsigned comment added by Cyberina 11 (talk • contribs)

I need to know the refractive index of solid ozone and solid HCl at infrared wavelengths and at ~80 K. I have not been able to find them anywhere. Can anybody help me? Cheers. --Shniken1 (talk) 04:23, 20 May 2008 (UTC)[reply]

Just a wild guess, but if this is a homework assignment they might want you to calculate it, rather than look s.th. up. Look at Hydrogen chloride "Melting point -114.2°C (158.8 K)" "Boiling point -85.1°C (187.9 K)" also look at Refractive index, phase velocity and Infrared.--71.236.23.111 (talk) 04:41, 20 May 2008 (UTC)[reply]

Nah it's not homework. Surely there is a comprehensive table somewhere with refractive indicies. All I can find are tables with the refractive indicies of gemstones on them..--Shniken1 (talk) 05:01, 20 May 2008 (UTC)[reply]

Doesn't look like it. These authors complained that there wasn't [8] They supplied some data. This might have something on ozone [9] For this you'd need an American Institute of Physics password, it might be something worth looking at, or nothing of interest [[scitation.aip.org/protected/mdfeed/ScholarFeed-20060721_JCPSA6_64.xml]. Good luck. 71.236.23.111 (talk) 05:25, 20 May 2008 (UTC) (oops, darn bot)[reply]

I had been under the impression that the reason it takes a greater force to start sliding something than to keep it moving was due to the jagged roughness (at an atomic level) of the surfaces. But if friction is due to electromagnetic bonds, then why does moving have anything to do with it? Is roughness irrelevant? Dicetumbler (talk) 04:37, 20 May 2008 (UTC)[reply]

I can speculate....

Perhaps it's because a moving object has momentum. In addition to the force required to keep the object moving, the object has an intrinsic force of m×g, where m is mass and g is the downward acceleration constant due to gravity (9.8 m/s²).

Or maybe, if an object is stationary, there are more electromagnetic bonds that form than when the object is moving and the bonds are continually being broken and re-formed. =Axlq 04:52, 20 May 2008 (UTC)[reply]

So about the Alcubierre_drive -- so if I'm getting this correctly, someone or something inside of the "warp bubble" would be unable to observe or interact with the area outside of the bubble. This leads to practical problems regarding steering and navigation. Okay. Got it. But supposing rather than the hypothetical spaceship inside of the bubble doing the driving, the bubble was merely generated around the ship, pointed in the right direction, and somehow made to deactivate or deteriorate after a given period of time? Or perhaps made to deteriorate in response to a given set of conditions, like entering the gravity well of a star? -- Call it the "warp cannon" or "warp rocket" approach. Is there anything in the theory (putting aside the known problems, like that pesky exotic matter) that would prevent this from working? Thanks. Please keep in mind when responding, I really don't know anything about physics, nor do I claim to. --Brasswatchman (talk) 06:16, 20 May 2008 (UTC)[reply]

There's nothing in the theory to prevent anything from working. General relativity relates the geometry of spacetime to the distribution of matter and energy in it, but it doesn't constrain the geometry. You can write down any crazy spacetime geometry you want and plug it into the equations of general relativity and it will tell you what the mass-energy distribution has to be. Alcubierre simply wrote down a geometry that roughly corresponds to the science-fiction idea of a warp drive, and then plugged it into general relativity to see what the mass-energy distribution looked like. The answer is that it looks like nothing known to science. It's not just that you need stuff with negative mass, it has to move over time in the way the warp drive demands, even though there are no laws of physics that would cause any kind of matter to move that way. That's where things should have ended, but for some reason they didn't, possibly because the desire to believe in warp drives is so strong and possibly because not everyone understands how little general relativity by itself can tell you about what is and isn't possible.

As for particular technologies like your cannon, there's only a limited amount of speculation you can do without inventing some laws of physics that would allow the drive to work in the first place. People who work on this stuff do make at least a couple of basic physical assumptions. One is no faster-than-light travel in the usual local sense, and the other is some limited form of causality to prevent the warp bubbles from showing up spontaneously for no reason. The second assumption is actually pretty dubious because the warp bubbles do show up spontaneously in Alcubierre's geometry, and if you invoke some physics to prevent that from happening, it's hard to see why it wouldn't also prevent the exotic matter from behaving in the right way once it's been introduced. But anyway, with those assumptions your cannon won't work. The outside of the bubble at later times is causally disconnected from the outside at earlier times, so (assuming no local FTL) it can't propagate on its own, and (assuming no acausal magic) the right configuration of exotic matter for continued propagation won't appear on its own. The closest you could get would be a cannon that starts firing long in advance, emitting a fast-moving configuration of matter that evolves into later stages of the warp drive in reverse order (the earliest matter fired becomes the last stage of the warp bubble). But it's only because we've discarded virtually every law of physics that we can even begin to contemplate such a thing. -- BenRG (talk) 10:50, 20 May 2008 (UTC)[reply]

Picklelilly (talk) 06:32, 20 May 2008 (UTC)[reply]

Look at Rock (geology) and Hematite--71.236.23.111 (talk) 07:20, 20 May 2008 (UTC)[reply]

I think it is because it has lots of iron in it. Bed-Head-HairUser:BedHeadHairGirl12:53, 20 May 2008 (UTC)[reply]

We also have a great Geology of Australia article. From there, I found maps from the Australian government's Geoscience division which document a whole lot of mineral deposits. These may help visualize the mineral distribution! Nimur (talk) 14:40, 20 May 2008 (UTC)[reply]

I wish to point out that not all of Australia's soil is red. The red colored soil in Australia is mainly due to the presence of iron oxide. 202.168.50.40 (talk) 02:53, 21 May 2008 (UTC)[reply]

See the Laterite article, and from Eyre, S. R. (1963). Vegetation and soils; a world picture. p. 255. OCLC 441202:

It is in those tropical regions with pronounced wet seasons alternating with definite seasons of drought that horizons of laterite are found extensively...because of climatic change, laterite can now be found in areas which are far too dry to permit laterite formation at the present time. These crusts are thus entirely fossil...

—eric 04:09, 21 May 2008 (UTC)[reply]

Per stellar evolution, Sun will become red giant in 5 billion years. However the luminosity of the Sun will increase by 10 percent over the next 1.1 billion years. Will civilization and higher group of land mammals become extinct only when Sun becomes red giant or within 1.1 billion years? What will be the effect on land animals/primates if luminosity of Sun increases by 10 percent? Otolemur crassicaudatus (talk) 13:14, 20 May 2008 (UTC)[reply]

A trivial calculation shows that, all else being equal, atmospheric temperatures would increase by 30C across the board. That would increase water vapor pressure by about a factor of 5 (in mmHg, at least), which would probably be catastrophic to land-based life. Sea-based life would certainly continue. Either way, these are incredibly slow changes, so evolution might work its way around such things. This is just my impression from some basic physics and little more. SamuelRiv (talk) 14:29, 20 May 2008 (UTC)[reply]

How do you get from +10% to 30C? The Stefan-Boltzmann law tells us that temperature goes as the 1/4 power of the radiative flux. So before we consider feedbacks +10% flux is only +2.4% in temperature which is more like 7 C. Feedback processes, like water vapor, will amplify that, but I think 30 C is an overstatement. Dragons flight (talk) 15:53, 20 May 2008 (UTC)[reply]

Earth#Future says the Earth is only expected to be habitable for about 500 million years. --Tango (talk) 15:03, 20 May 2008 (UTC)[reply]

I'm no expert, but maybe looking at those figures in perspective will help. The entire development from the first multicellular animals via dinosaurs to what we see now has taken less than 1.1 billion years or the 900 million years the article earth cites for plants disappearing. In the past 1.1 billion years, there have been several ice ages and "only" 200 million years ago all of earth's land mass was clumped together in one large continent Pangea. There have been five big and a couple of minor extinction events during the past 600 million years. This makes it kind of difficult to predict whether there are going to be land animals around and what land animals that would be. 71.236.23.111 (talk) 15:38, 20 May 2008 (UTC)[reply]

I think "habitable" in that context means habitable by humans - that's rather easier to predict, since we know what humans can survive. Life has a tendency to evolve to find ways of surviving in new environments, so I expect life in some form will go on much longer, but human life (without artificial means) won't be able to survive on Earth in 500 million years time (give or take). Of course, these are quite rough estimates and I don't think it would be too surprising if they turned out to be off by quite a large margin. --Tango (talk) 16:01, 20 May 2008 (UTC)[reply]

You're right Dragon - I forgot about SB and treating the Earth like a blackbody. My reasoning was just treating everything like a gas, which is quite silly now that I remember all those rules about how radiation transmits energy. SamuelRiv (talk) 16:24, 20 May 2008 (UTC)[reply]

What would the human being be like if the last Ice Age didn't happen?--Vincebosma (talk) 14:44, 20 May 2008 (UTC)[reply]

See almost exactly the same question asked a few days ago: Wikipedia:Reference_desk/Science#What_if_the_Ice_Age_never_happened.3F! --Tango (talk) 15:02, 20 May 2008 (UTC)[reply]

But no one described what the human beings would be like --Vincebosma (talk) 15:08, 20 May 2008 (UTC)[reply]

No meaningful extrapolation can be made. Your best guess is likely as good as anybody else's. — Lomn 15:18, 20 May 2008 (UTC)[reply]

Couldn't someone just try? --Vincebosma (talk) 15:34, 20 May 2008 (UTC)[reply]

Super intelligent 30 foot tall creatures with razor sharp claws, gene manipulation has left them unable to reproduce through natural means so they are reliant on cloning to propagate the species, also they have lost the ability to feel love. Actually humans would probably not be much different its only history that would have gone much much differently since I don't think humans have changed that much physically since the last ice age, just culturally. -- Mad031683 (talk) 15:44, 20 May 2008 (UTC)[reply]

The last ice age is this ice age, since the polar ice hasn't melted yet, last I checked. We are in an interglacial. So what if there were no polar ice. What would you model the climate to be like? You could create a scenario of Neanderthals and Homo erectus not dying out. Would you keep them in a zoo? Paranthropus might still be around. Would your homo sapiens have left Africa? The scenarios are yours to play with. Read the articles follow the links and see what you can make fit. 71.236.23.111 (talk) 17:14, 20 May 2008 (UTC)[reply]

I disagree that humans wouldn't be that different. If it weren't for cold weather, the mammals wouldn't have thrived in the first place. I'm not sure how long ago we are talking about here when the questioner said "last ice age," but in general the average size of organisms in the biosphere increases with the average temperature. Dinosaurs and their neighbors were so big because it was so damned hot. When it got cold, small mammals started to dominate and we arose from them. No ice, no people. --Shaggorama (talk) 05:26, 21 May 2008 (UTC)[reply]

The Last glacial period was recent enough that Humans had already evolved to something very close (if not identical) to modern man, so it didn't play a major part in our evolution. It may, however, have played a major part in us thriving so well all over the world. --Tango (talk) 11:57, 21 May 2008 (UTC)[reply]

The world is a 'chaotic' system - in the sense of a butterfly flapping it's wings in China causing a tornado in Texas years later. The consequences of such a major hypothetical as a missing ice-age are quite literally unknowable. Could some tiny detail of changed human evolution caused us to wipe ourselves out with nuclear weapons during the cold war? Sure! Really, there is no rational answer to this. 71.155.164.147 (talk) 19:58, 21 May 2008 (UTC)[reply]

I've always "heard" that for items that sit on the shelf for a while, fluorescent store lights degrade perishables that are in clear bottles/jars. When shopping for food (mayo, salad dressing, oils, etc) and heath items (vitamins, lotion, body wash, etc), I always select items near the back of the shelves (where it's dark and shadowed) Any truth to this? --70.167.58.6 (talk) 16:16, 20 May 2008 (UTC)[reply]

Not just fluorescent light, but any light in general tends to catalyze unwanted chemical reactions. (For a more extreme example, why do you think hydrogen peroxide is stored in brown bottles?) Of course, your idea doesn't work if the jars at the back of the shelf are older than those at the front. shoy 16:38, 20 May 2008 (UTC)[reply]

Consumer Reports magazine has reported for years that milk exposed to light will, at a minimum, develop "off flavors", hence the HP Hood Lightblock bottle. I expect it's true, to one degree or another, for many foods.

Atlant (talk) 17:02, 20 May 2008 (UTC)[reply]

The jars at the back should be newer - I believe pretty much all shops practice stock rotation. --Tango (talk) 17:58, 20 May 2008 (UTC)[reply]

Given that most bottles are plastic or cheap glass, there should be very little difference between fluorescent lights and incandescent lights having the same luminous intensity. People worry about the small amount of UV light in fluorescents, but the packaging should filter that. If a product is light sensitive, I would expect that it would react regardless of the type of lighting in the store. Dragons flight (talk) 18:09, 20 May 2008 (UTC)[reply]

Note that fluorescent and incandescent lights of the same luminous intensity will nevertheless have different spectra. Compare the essentially black body emission of an incandescent bulb (link) to the emission spectrum of a modern fluorescent lamp (link). Note that fluorescent lamps have sharp peaks down in the green (around 550 nm), whereas the emission of an incandescent lamp is brightest in the infrared.

The extra share of higher-energy green photons will drive some photochemistry that wouldn't happen under red light. Honestly, though, I'm not inclined to worry about it for items at the grocery store. You have no idea how things were stored before they got to the shelf, and a properly-managed store will rotate its stock (new products are added at the back) so that product at the front today isn't the product that was at the front yesterday. (In principle, then, you can get the freshest product by taking the stuff from the back—but that assumes that the store does rotate stock properly. It could be that the stuff at the back is the oldest on the shelf by a fair margin because the front items turn over regularly...then where are you?) I'd be more concerned for the very few items that demonstrate significant light sensitivity--like the aforementioned beer. TenOfAllTrades(talk) 19:26, 20 May 2008 (UTC)[reply]

It's well known that beer is light-sensitive. Too much light exposure leads to skunked beer. I would imagine other light-sensitive foods exist, but the details would vary depending on the chemical reactions involved. Friday (talk) 18:14, 20 May 2008 (UTC)[reply]

• My mother always takes from the back because less people would have picked it up and tampered with it. Now I know a better reason!Avnas Ishtaroth (talk) 01:41, 22 May 2008 (UTC)[reply]

A friends and I have argued after watching the film There Will Be Blood about whether or not oil can catch light without being heated. He argues that it is a common misconception that oil is highly flammable, and that it needs to be heated before it will ignite, though I disagree. Looking at the main oil article on Wikipedia I can't see a conclusive answer. —Preceding unsigned comment added by 81.137.213.177 (talk) 16:27, 20 May 2008 (UTC)[reply]

How would you ignite it without heating it? It's not likely to spontaneously burst into flames at room temperature, you would need to put a match to it or something. --Tango (talk) 16:31, 20 May 2008 (UTC)[reply]

How much you need to heat it will depend strongly on what oil you're talking about. Algebraist 16:42, 20 May 2008 (UTC)[reply]

Rumaging through my rusty ol' thinking box. You might have a look at Flash point, Combustion, Autoignition temperature, vapor pressure. What makes things go "boom" or "foomp" is released energy from rearranging chemical bonds. If you could use another reaction than oxidization, to break up the chemical bonds in your oil, you might be able to find something that works at room temperature and releases enough energy. That reaction might no longer qualify under "ignite" or "flamable". The finer the distribution of oil particles in your reactant the more efficient the reaction. Maybe someone else can help you develop this further. (Or tell you why it won't work.) --71.236.23.111 (talk) 18:12, 20 May 2008 (UTC)[reply]

I think that what the questioner is asking is what would happen if you simply dropped a match onto a pool of crude oil. Would it catch fire instantly like gasoline? Or would it take special effort to get it lit? APL (talk) 17:54, 20 May 2008 (UTC)[reply]

Crude oil is a mixture of all sorts of length of hydrocarbon chains. At a refinery they crack them into shorter ones and sort those by product. Assuming that your crude oil puddle hasn't been there for ages, it should still contain short chained hydrocarbons for immediate ignition. Don't try this at home, because the match will probably light the vapors above your puddle rather explosively. 71.236.23.111 (talk) 21:58, 20 May 2008 (UTC)[reply]

You really can't reliably light gasoline by dropping a lighted match into it. It's only the vapor that burns easily and if it's not in an enclosed space or sprayed out into an aerosol or something, gasoline is really rather reluctant to burn. 70.116.10.189 (talk) 22:57, 20 May 2008 (UTC)[reply]

Oil lamps were certainly the lighting of choice for quite a few of the previous centuries.

Many (many) summers ago, I did ceremonial work which involved lots of small flames here and there. The standard recipe was 6-oz metal juice can (yes, they were metal in those days), stuffed 3/4 full with cotton for the wick, and then filled not-quite-full with kerosene, same as #1 diesel today. Made a nice, flickery, not-too-hot, and definitely smoky flame.

To extinguish said lights, it was sufficient to poke the cotton wicking down below the surface of the kerosene -- it wouldn't burn without the wick. I think that brings us to the common thread here: be it wax, butter, animal fat, or other oil, the wick seems to be the key feature. The "heavier" products thus need at least sufficient heat to melt them enough to flow, mix with air, and burn.

-- Danh, 63.231.162.222 (talk) 23:15, 20 May 2008 (UTC)[reply]

The short answer is that most oils need to be either (a) heated or (b) atomized or (c) dispensed through a wick in order to burn. If you drop a lit match into a pool of oil (any kind of oil), the oil is unlikely to catch fire.

A nice way to atomize a natural oil and watch it catch fire is to hold a lighter or lit match next to some orange rind as you squeeze it. (An even nicer demonstration, in its way, is the Devil's Cocktail.) —Steve Summit (talk) 03:24, 21 May 2008 (UTC)[reply]

I hate to be anecdotal, but I can't find a good reference for this. I saw a thing on TV where some firemen were going to practice fighting oil fires by putting out a vat of burning diesel fuel. They had to use a propane torch to get it to start burning. Tossing a match into it would not have ignited it, I guess. Crude oil at the wellhead is another matter, though. I haven't seen the movie you mention, but I assume a gusher catches fire at some point. It is common knowledge that people who fight oil well fires live in fear of the spark that would re-ignite the gusher after they've blown it out with explosives. Crude contains lighter, more volatile hydrocarbons than does refined diesel, as was mentioned above, and the gusher itself aerosolizes the oil somewhat, I would imagine. --Milkbreath (talk) 10:45, 21 May 2008 (UTC)[reply]

Related question: In the video game The Darkness, there is one scene where the protagonist ignites money by pouring gasoline on it and shooting the money. I severely doubt this is possible, but is there any truth to it?Avnas Ishtaroth (talk) 01:44, 22 May 2008 (UTC)[reply]

Hi there folks, I've been searching for a while now, and have been staggeringly unable to find the answer to my question (including on #physics at freenode); which of the W bosons mediate the electron capture, positron capture, neutron-neutrino, and anti-neutrino-proton collisions? More helpfully, and in general, where can I find Feynman diagrams for these fairly straightforward weak interactions?

Cheers! Carl Turner (talk) 16:37, 20 May 2008 (UTC)[reply]

Well, here are some beautiful suitable-for-framing Feynman diagrams for the interactions I think you're talking about:

    electron capture  positron capture   neutron-neutrino  antineutrino-proton

       |       |          |       |          |       |          |       |
     n ^   W+  ^ nu     p ^   W+  v nu     p ^   W+  ^ e-     n ^   W+  v e-
       |--->---|          |---<---|          |---<---|          |--->---|
     p ^       ^ e-     n ^       v e-     n ^       ^ nu     p ^       v nu
       |       |          |       |          |       |          |       |

The reason you can't find out whether it's the W+ or the W- is that the particle-antiparticle distinction doesn't make much sense for virtual particles. These are tree diagrams, so the W does have a well-defined four-momentum, and if it's timelike (which it won't always be) you could say that you "really" have a W+ or W- depending on which way the four-momentum points. E.g. in the first diagram if the neutrino's final energy is small enough then the electron momentum minus the neutrino momentum could be timelike and future-directed, in which case you could say that the electron "decays" into a W- and a neutrino and the W- collides with the proton turning it into a neutron. But it's a pretty dubious thing to say; you have to wonder why the electron happened to spontaneously decay when there was a convenient proton nearby to absorb one of the decay products, thereby making the decay possible in the first place. Also, these aren't the only Feynman diagrams for these processes, just the first-order contributions. It's better to think of the whole thing as a single interaction which involves the W field but not a W+ or W- particle. -- BenRG (talk) 18:35, 20 May 2008 (UTC)[reply]

Thanks a lot, those are the interactions I was describing, and I appreciate the clarification; and blame our educational system for talking in terms of virtual particles and not the fields/forces they represent. Oversimplification will be the death of us yet. Two further queries; by "first-order contributions", are you just making a distinction between quarks and hadrons? And secondly, is it justifiable to discriminate between the W bosons in the case of the beta decays? Given that they are usually illustrated with the interaction happening 'over time', i.e. with the following diagram, does this mean that the 'distance' the W- boson 'travels' is always time-like? I'll write this up for the articles shortly, and include the discussion in terms of space-time vectors, so I'd like to be clear.

Regards, Carl Turner (talk) 20:58, 20 May 2008 (UTC)[reply]

By "first-order contributions" I mean that there are many Feynman diagrams for these particular interactions and the ones I drew above are just the simplest ones. E.g. you could add a photon line between the electron and the proton in any of those diagrams and get a more complicated diagram with the same inputs and outputs, and that diagram also contributes to the overall amplitude of the interaction. There are also diagrams with more than one W. The different diagrams aren't different ways the interaction can happen, they're different "corrections" to the amplitude of the true, unique interaction, which is like a combination of all the diagrams. So this is another reason why it's problematic to talk about "the" W particle.

In the β^- decay diagram shown above the W always has a timelike momentum, but I still don't think it makes physical sense to call it a W- for the reasons I've already mentioned. You can't split the diagram into two separate events, the emission and subsequent decay of a W-, because there's not nearly enough energy in this situation to make a real W particle. The intermediate W is doomed to remain on the inside of the Feynman diagram, undetectable and ontologically ambiguous (since that isn't the only Feynman diagram).

On the other hand there's clearly a transport of charge going on here, it just isn't time ordered. In the electron capture diagram it seems fine to say that the intermediate W boson carries positive charge out of the nucleus or that it carries negative charge into the nucleus. Those are two descriptions of the same thing, whereas a real W+ moving to the right isn't the same as a real W- moving to the left. Even in the more complicated diagrams I think there will always be a W performing this "role", since there aren't any other Standard Model particles that can do it. So maybe you could play that up in the description. Or maybe it would just be confusing. I want to suggest something helpful here, but I don't think I understand QFT well enough.

You can probably ignore the fact that the nucleons are made up of quarks and gluons; there's no requirement that the particles in Feynman diagrams be fundamental (and who knows what's fundamental anyway?). Similarly you can deal with the proton and neutron being part of a larger nucleus by replacing the "p" and "n" with ¹³⁷
₅₆Ba
and ¹³⁷
₅₅Cs
or what have you. I don't know how one deals with the electron capture situation where the electron starts out orbiting the nucleus instead of coming in from infinity (which is the usual assumption for Feynman diagrams). -- BenRG (talk) 19:01, 21 May 2008 (UTC)[reply]

If francium reacted with water, i know its not possible because it decays radioactively too quickly or something, what would the explosion be the equivalent of, a TNT blast? --Hadseys 21:47, 20 May 2008 (UTC)[reply]

This is rubidium, then caesium in water. At a guess, I'd say that the francium would scatter pieces of container into the four corners of the room. --Kurt Shaped Box (talk) 21:56, 20 May 2008 (UTC)[reply]

And what do you get once you've watch Kurt's video - the Francium Bomb Test in Water video :-)) Astronaut (talk) 22:39, 20 May 2008 (UTC)[reply]

Francium does not exist for long enough to be able to react with water due to its extreme instability. The video posted was a nuclear detonation test. Acceptable (talk) 23:47, 20 May 2008 (UTC)[reply]

Specifically, Operation Crossroads, shot Baker. --98.217.8.46 (talk) 00:26, 21 May 2008 (UTC)[reply]

Of course it was and I would hope the OP spotted that too - that's why there's a big smiley after the link. Astronaut (talk) 12:46, 21 May 2008 (UTC)[reply]

This source estimates the enthalpy of formation (that is, how much energy is released or required when making given amount) of francium hydroxide hydrates. Hopefully, one of our more chemically minded contributors can convert these into something more meaningful. Laïka 18:59, 21 May 2008 (UTC)[reply]

There are other effects that need to be considered. For example, if francium generates a hydrogen explosion so quickly it blows itself out of the water, you might get a series of small "pop"s as it bounces around on the water. Total energy released doesn't mean much if it's released over half an hour of bouncing around. --Carnildo (talk) 21:04, 21 May 2008 (UTC)[reply]

What benefits does a plant gain from containing vitamins and other compounds that are nutritious to animals? I can see why a plant would want to make nutritious fruit so animals could eat it and disperse the seeds, but I'm wondering why there are nutrients in other parts such as leaves and roots which the plant presumably doesn't want eaten. Although I understand that animals have probably evolved to make use of the chemicals in plants rather than the plants evolving "for" the animals, I'd like to know why the plants contain these nutrients in the first place, what function they serve. 69.224.182.55 (talk) 01:56, 21 May 2008 (UTC)[reply]

Plants are biochemically complex too, thus the production of those chemicals for use in the metabolic pathways. —Preceding unsigned comment added by 199.76.188.69 (talk) 02:02, 21 May 2008 (UTC)[reply]

You could just as well ask why cows evolved to provide nutritions milk. That's not the purpose nature intended. --71.236.23.111 (talk) 02:12, 21 May 2008 (UTC)[reply]

uh....what? actually, 71.236, 'it is'. First off, it should be pointed out that the whole teleological notion of "nature intended" is intrinsically flawed. But as long as we're going to use that kind language, the 'intended purpose' of cow's milk is to supply nutrients to its calves. So yes, the nutritious quality of cow's milk is a direct result of evolution.

In response to the original question, though plants and animals look really different, the general biological strategies are often similar. For instance, take energy storage. Lipids (oils and fats) and sugars are general strategies used by plants and animals to store energy. Consequently, plants often store energy for their own purposes in areas that get eaten by animals; basically the animals are raiding energy from the plants. Also, plants and animals use vitamins and minerals in fairly similar ways (often as cofactors to enzymes, or precursors to other molecules). (In theory) Animals evolve dependency on nutrients from external sources when there is a sufficient quantity available to them in their diet that it is no longer energy efficient for them to synthesize the substance on their own . For instance, take vitamin c. It is incredibly important in a variety of metabolic pathways and consequently most organisms synthesize it on their own; humans are one of a (relatively) few exceptions. Other nutrients, such as minerals, simply cannot be synthesized and may just be present in sufficient quantities in the diet to be incorporated into the metabolism. Take iron. Iron is a metal that is an important component of many proteins, such as hemoglobin. As an element, it just can't be synthesized. Plants suck it up from the ground and we eat the plants (to be fair, we also get it from some water sources). --Shaggorama (talk) 05:17, 21 May 2008 (UTC)[reply]

As far as "that kind of language" goes, I can't help it, it's common English. (I could try a couple of others with a lot less ability and effect.) Plants having a strategy sounds only slightly less off to me than "nature intending" something. (Which I wasn't too happy with to begin with.) I agree that my post wasn't worded to mean what I intended to say if read by itself. What I was trying to imply was that cows produce milk for calves, not humans. While there are symbiotic relationships based on mutualism (both win). Lots are based on commensalism or parasitism. 71.236.23.111 (talk) 06:19, 21 May 2008 (UTC)[reply]

Well, on the one hand, humans are also mammals and produce milk as well. Our milk isn't that different from cows milk, so the nutritious qualitites of cows milk are nutirtious for us as well. BUT, this statement needs qualification. As we both agreed, cows milk is "intended" for calves, in the same way mother's milk is produced for the consumption of babies. As humans age, we lose an important enzyme for the digestion of milk, Lactase, causing Lactose intolerance in many people. Fact is, the evolution of the role of lactase in our bodies hasn't caught up to our consumption of cows milk. You are absolutely right: cows produce milk for calves, not humans. Likewise, cows milk didn't evolve a nutritious capacity for humans, and it makes many people feel sick. --Shaggorama (talk) 17:18, 21 May 2008 (UTC)[reply]

A lot of veggies are very different from their naturally occurring sources due to many years of plant breeding, selectively breeding more nutritious and easier to grow crops. Many veggies are Root vegetables which originally stored nutrition in their storage organs to allow themselves to be able to grow quickly when the correct season occurred. As you mention, some fruits have a different strategy, there flesh is deliberately attractive to animals so that the fruit and seeds are consumed and the indigestible seeds unwittingly deposited elsewhere (often with a healthly dose of compost!). GameKeeper (talk) 07:18, 21 May 2008 (UTC)[reply]

Most plants are not nutritious to humans or other animals. We tend to think of those that are as common only because we have evolved a long-term mutually symbiotic relationship with them, where we (like honey bees and flowers) aid the plant in its survival and reproduction for our own benefits. With things like agriculture it is a major conceptual error to forget that humans have been involved at an ecological level for tens of thousands of years. --98.217.8.46 (talk) 16:13, 21 May 2008 (UTC)[reply]

Is it known what substance(s) in peanut is/are responsible for the severe allergies to the food that seem quite common these days? Have there been studies on possible changes in the nutrition/allergen content of peanut over the past several decades? --72.94.50.27 (talk) 02:46, 21 May 2008 (UTC)[reply]

I'd like to know something about this to. I never heard of peanut allergies back when I was a kid (less than two decades ago). Now it seems like it's this huge problem. Have humans suddenly become more sensitive to allergens, have peanuts become more noxious or has awareness just increased? --69.151.29.16 (talk) 04:22, 21 May 2008 (UTC)[reply]

See Peanut allergy for 72. As for 69's question. No, humans aren't more susceptible to allergies, it is because the environment that they live in has become cleaner (that's why allergies and asthma are more common in developed countries). Anyways a tidy environment has decreased the population of gut parasites in humans. This caused IgE, a part of our immune system that deals with parasites to become "bored" (due to lack of a better word) and tries to attack something else which usually the thing that the person becomes allergic to.--Lenticel ^(talk) 04:53, 21 May 2008 (UTC)[reply]

I have heard of the hygiene hypothesis too, but I'm not convinced yet that's the correct explanation, or that cleaner environment is the only or dominant cause of peanut allergy. The possibility that peanuts today are not the same as they were decades ago should at least be examined. The peanut allergy article does not mention any specific allergens in peanut; it doesn't seem to answer the original question. --72.78.102.134 (talk) 12:33, 21 May 2008 (UTC)[reply]

It's also likely that we just understand more about allergies now than we did, and communication has become more common (so it's better known). Many of the recent "epidemics" tend to come down to better diagnosis and more awareness of the allergies/conditions. -- — The Hand That Feeds You:^Bite 13:22, 21 May 2008 (UTC)[reply]

If you eat a good variety of common vegetables, do you need fruits? Clarityfiend (talk) 05:15, 21 May 2008 (UTC)[reply]

If you eat enough Big Macs, you don't need to eat anything else at all! --Shaggorama (talk) 05:44, 21 May 2008 (UTC)[reply]

That's funny. I can't see why not when veges have loads of benefits (weight loss, heart disease prevention, fibre etc). Currently there's a push to get people vege-wise here in Oz[10] in a ratio of 2 fruit, five veg. In countries where grains are the basis of a diet, I doubt fruit would get a look-in or would be a rare treat/seasonal thing.

But wait for it, there's the dark side of broad beans here[11] aka Favism. So maybe it's "common vegetables" plus all the other things (nuts, grains, etc) or is it just veges vs fruit? Julia Rossi (talk) 06:02, 21 May 2008 (UTC)[reply]

there's also a problem regarding the definition of fruits and vegetables.--Lenticel ^(talk) 06:15, 21 May 2008 (UTC)[reply]

83.130.129.138 (talk) 05:42, 21 May 2008 (UTC)[reply]

Nice pic. There's Halesia as in Halesia tetraptera or Silverbell? Flowers around this time. Depends where you are and I'm assuming it's a tree (not shrub or vine). Anyone? Julia Rossi (talk) 05:55, 21 May 2008 (UTC)[reply]

Well, I'm from Israel. However, I took the picture in the Liberty Island :-) 83.130.129.138 (talk) 06:28, 21 May 2008 (UTC)[reply]

On closer inspection, it's an apple blossom, see the article Apple tree and scroll down to right side image "apple tree in blossom flower". I love a good mystery, : ) and now we know what grows on Liberty Island. Feel free to add your pic to the article to show blossoms in cluster formation. Julia Rossi (talk) 07:02, 21 May 2008 (UTC)[reply]

how long does it take to detect hiv after having sexual intercourse with an infected person ?

Thanx —Preceding unsigned comment added by 200.56.111.250 (talk) 07:39, 21 May 2008 (UTC)[reply]

HIV. Wisdom89 _{(T / ^C)} 07:41, 21 May 2008 (UTC)[reply]

People who become infected with HIV may have no symptoms for up to 10 years, but they can still pass the infection to others. After being exposed to the virus, blood tests results change from HIV negative to HIV positive usually within 3 months from[12] Julia Rossi (talk) 09:28, 21 May 2008 (UTC)[reply]

Is this a trick question? It is perfectly possible to have unprotected sex with an HIV infected person and not get HIV. However I would not recommend playing russian roulette with your healthy body. 122.107.199.2 (talk) 10:43, 21 May 2008 (UTC)[reply]

I think the OP means "reliably detect whether or not you have HIV", and Julia's answer looks correct to me. Of course, standard disclaimer: If you have any concerns regarding a medical issue, you should consult a doctor. --Tango (talk) 11:49, 21 May 2008 (UTC)[reply]

I want to know if light can,t escape black hole, then how gravitons are able to leave it and affect the near by objects by gravitational force? —Preceding unsigned comment added by Pkbansal (talk • contribs) 12:13, 21 May 2008 (UTC)[reply]

Gravitons are entirely theoretical and, as I understand it, not generally acknowledged to be likely or necessary. Gravitation as warped space-time absolves the need for such particles. Further developments in quantum mechanics (and other fields of physics) are needed to fully explain or refute the graviton. — Lomn 12:42, 21 May 2008 (UTC)[reply]

But black holes can be electrically charged too, and photons certainly exist—how do they get out? I agree with your answer, though. This is a case where the virtual-particle picture of fields is misleading, and I'm not certain it works at all. There's more to quantum field theory than Feynman diagrams.

There's clearly some level at which gravitons make sense. You'd expect a theory of quantum gravity to predict quantization of gravitational wave amplitudes, i.e. real gravitons. And weak-field general relativity can be quantized against a fixed background, leading to Feynman diagrams with virtual gravitons ([13]). But I don't think virtual gravitons make sense in a background-independent theory. -- BenRG (talk) 19:40, 21 May 2008 (UTC)[reply]

Anyway, I think the answer is that gravitons have to be massless, yes? Or else they'd be affected by gravity as well. --98.217.8.46 (talk) 14:46, 21 May 2008 (UTC)[reply]

Photons are massless, they're still affected by gravity. --Tango (talk) 15:21, 21 May 2008 (UTC)[reply]

Of course photons have mass, namely ${\displaystyle h\nu /c^{2}}$. What they lack is rest mass.

Well, yes, but gravitons contain energy and therefore mass as well, don't they? --Tango (talk) 18:42, 21 May 2008 (UTC)[reply]

Hi. I heard that gravitons can't have mass otherwise the physics wouldn't work. Also, perhaps the gravitons are more clustered near the black hole, so that don't actually leave it? Also, would gravitons actually approach each other? Probably not, because even photons don't do that and gravitons are always travelling away from each other. Also, black holes are more like a deep tunnel in spacetime, deep but not very wide, so an object parsecs away likely won't be very much affected by an average black hole, and an object takes forever to be ingested into a black hole because the centrifugal force is almost as strong as the gravitational attraction. They might send gravitational waves if they collide. Also, light doesn't actually escape a black hole, it spirals around it before being stretched and swallowed, although some say radiation might shoot out of some black holes' polar axes. I've also heard that the only laws of physics and forces black holes don't almost always break are gravity, rotational force, and electromagnetic force. Thanks. ~AH1^(TCU) 20:02, 21 May 2008 (UTC)[reply]

I think when people say gravitons have to be massless, they mean rest mass. --Tango (talk) 20:25, 21 May 2008 (UTC)[reply]

There is an anser to this question from the sci.astro newsgroup FAQ here. Long story short, it says that the Coulomb force is mediated by the exchange of virtual photons which can escape from inside the event hroizon, so a black hole can carry a charge. A consistent quantum theory of gravity (if we ever develop one) would presumably involve virtual gravitons which would behave in the same way. What you can't do is send either electromagnetic or gravitational waves from inside the event horizon to the outside, as this would require the escape of real photons/gravitons. Gandalf61 (talk) 08:31, 22 May 2008 (UTC)[reply]

What are the gases that dissolve in water? Why do some gases dissolve and some don't? —Preceding unsigned comment added by 124.43.204.248 (talk) 15:53, 21 May 2008 (UTC)[reply]

Are gases really different than solids or liquids, or is "Like dissolves like" (a polar or ionic compound will dissolve in water) not affected by the physical state of the compound at room temperature? Remember that many things are "a little soluble": there is no sharp distinction between "soluble" and "insoluble", so you have to decide how soluble you want. If it weren't for oxygen dissolved in water (concentration of 7.6 mg/L at 20 °C), all the fish would die, but that sure looks like a low solubility (carbon dioxide is 1.7 g/L at that temperature). DMacks (talk) 16:35, 21 May 2008 (UTC)[reply]

And also, there's a solubility table in regards to water. --Wirbelwindヴィルヴェルヴィント (talk) 16:40, 21 May 2008 (UTC)[reply]

I believe the solubility of a solid or liquid in water generally increases with temperature, whereas the solubility of a gas decreases with temperature. That's the only major distinction I can recall. --Prestidigitator (talk) 20:58, 21 May 2008 (UTC)[reply]

One very soluble gas is ammonia. You can easily get a 30% solution. This is polar. nitrogen and oxygen only dissolve a little, but what does is very important to life. Graeme Bartlett (talk) 21:38, 21 May 2008 (UTC)[reply]

We feel pain when we touch a heated object or boiling water. What is exactly the cause for this? —Preceding unsigned comment added by 124.43.204.248 (talk) 15:57, 21 May 2008 (UTC)[reply]

"Pain" is how the brain interprets the nerve impulses generated by sensory neurons. DMacks (talk) 16:14, 21 May 2008 (UTC)[reply]

See Pain.-Arch dude (talk) 16:48, 21 May 2008 (UTC)[reply]

If you want a less biologically oriented answer (as implied by your title), you might be interested in heat transfer. --Prestidigitator (talk) 21:00, 21 May 2008 (UTC)[reply]

All the diagrams of a full wave rectifier I've seen incorporate a diode bridge with a capacitor to smooth the output. However, this appears to be basically equivalent to a single diode with a capacitor. Plugging it into this simulator doesn't yield any obvious reason that this isn't used – so, since I'm assuming there's a reason, I'm curious as to why this simpler rectifier isn't used? Angus Lepper^{(T, C, D)} 16:47, 21 May 2008 (UTC)[reply]

File:Simple Full Wave Rectifier.svg

What's rectifying the full wave? Only one diode means that half of your input waveform is entirely clipped out. See rectifier and you'll see your circuit, sans smoothing capacitor, as a half-wave rectifier. — Lomn 16:58, 21 May 2008 (UTC)[reply]

Ah, I was being daft! Of course half of the input waveform is clipped out; this was being hidden by the capacitor (so it sort of works, but requires a larger capacitance to make up for the 'lost' wave). I somehow managed to convince myself that the capacitor was doing some magic. Whoops! Cheers, Angus Lepper^{(T, C, D)} 17:13, 21 May 2008 (UTC)[reply]

The half wave rectifier was used when diodes cost a lot, back in the hollow state thermionic valve era. Nowdays the rectifier costs perhaps 1% what they used to but the transformer still costs plenty, so we get more diodes and transisters in the power supplies. Graeme Bartlett (talk) 21:43, 21 May 2008 (UTC)[reply]

He discovered its sweet taste serendipitously when he licked his finger, which had accidentally become contaminated with aspartame.^[1]

— http://en.wikipedia.org/wiki/Aspartame#Discovery_and_approval

There are electronic tongues which taste, for example, toxicity in different substances, since this would be unethically dangerous for humans to do. Do they use any sort of this technology to test new and existing chemicals for taste, such as sweetness?

Same question, but bitterness?

Same question, but sourness?

Etc.

Etc.

Thank you.68.148.164.166 (talk) 17:24, 21 May 2008 (UTC)[reply]

I noticed on the side of a box of stink bombs "if swallowed, take vinegar or juice of citrus fruits, followed by vegetable oil, and seek medical advice". What does the odd combination of acid and oil do to the stink bomb chemicals? Why do they recommend this strange combination of foods? Laïka 17:49, 21 May 2008 (UTC)[reply]

Does the box also have a list of ingredients? Judging by our article on them, I don't think stink bombs all contain the same chemicals. Drinking acid suggests the contents are a strong alkali that needs to be neutralised - I'm not sure about the oil... it might form some kind of barrier against the contents, perhaps? --Tango (talk) 18:38, 21 May 2008 (UTC)[reply]

The only ingredient it mentions is Ammonium hydrosulphide, which is indeed an alkali. I guess that explains the acid, although probably, having hydrogen sulphide and ammonium citrate in your body is at least as bad. Besides which, stomach acid is many times stronger than lemon juice, so the contribution made by the juice would be tiny. Laïka 19:08, 21 May 2008 (UTC)[reply]

Yeah, it doesn't quite make sense, does it? It's my only guess, though. --Tango (talk) 20:22, 21 May 2008 (UTC)[reply]

It isn't always necessarily about strength, but also about the amount of available reactants. Probably if there's a base that is of concern, ingesting plenty of acid that you know your body can handle without harm wouldn't be a bad plan, but that's just an idea to ponder regarding a possible explanation; definitely not advice. Don't know about the vegetable oil. Could it be acting as a more effective solvent or something? --Prestidigitator (talk) 21:11, 21 May 2008 (UTC)[reply]

I would have thought not dissolving would be better - more likely to pass straight through. A less effective solvent, maybe? --Tango (talk) 21:23, 21 May 2008 (UTC)[reply]

If I have a prognostic marker of cancer, and some multivariate analysis of some description shows that it's not an independent marker, am I right in thinking that it's still a useful marker if it's easier to measure than those other markers and that the only drawback is that it doesn't offer anything in addition to those aforementioned markers? ----Seans Potato Business 18:13, 21 May 2008 (UTC)[reply]

I suppose so if you are going to not be bothered checking out those other harder to measure markers. And you have to consider if you want a prognosis or not. For example I don't care if the cockroaches in my kitchen have cancer or not, even if there is an excellent marker for it. Graeme Bartlett (talk) 21:49, 21 May 2008 (UTC)[reply]

Straightforward question!

Okay, for DNA replication an RNA primer is needed. Does this mean that for PCR the amount of DNA being replicated each cycle is LIMITED by the number of RNA primers included in the sample?

Thanks! —Preceding unsigned comment added by 83.141.77.130 (talk) 18:20, 21 May 2008 (UTC)[reply]

In standard PCR, almost universally one uses DNA primers in their reaction. Secondly, yes absolutely, the primers become incorporated into the amplicon as its number grows exponentially. Therefore, the primers become depleted as the reaction proceeds with time. This can definitely affect the outcome. Wisdom89 _{(T / ^C)} 19:49, 21 May 2008 (UTC)[reply]

---True, although in practice it is rarely an issue since usually the primers are in excess. If one uses a pair of primers at one micromolar, which is common, that would be enough for up to one micromolar product, which is an extremely large amount (100 microliter reaction, 250 bp product: 16.7 micrograms]. The nucleotides probably run out first. Woodlore (talk) 01:36, 22 May 2008 (UTC)[reply]

chicory

“

use of chicory as a coffee substitute (Root chicory - Cichorium intybus var. sativum) has been shown to damage human retinal tissue, with dimming of vision over time and other long term effects. Although small amounts of root chicory consumed medicinally or as a seasoning can be healthy and/or harmless, root chicory contains volatile oils that can be metabolized in the liver and digestive tract into toxic by-products that damage retinal nerve cells and cause dimming of vision if regularly consumed in large quantities as a coffee substitute

”

How can that possibly be true?? Why is it legal then, or -- I just looked carefully at the box -- there is no warning at all whatsoever :(

I would guess for the same reasons that coffee, alcohol and cigarettes are all legal, even though consuming large quantities of any of them can be detrimental to your health. The quote does say "Although small amounts ... can be healthy and/or harmless," so the question is just "what constitutes a safe, daily amount?" — Sam 18:54, 21 May 2008 (UTC) —Preceding unsigned comment added by 63.138.152.238 (talk)

I've noticed this as a common fallacy, that "x can't be harmful otherwise it would be illegal / have a warning", I guess it could be an appeal to authority. Some common examples of x are burned meat, aspartame and sodium benzoate. (also alcohol as previously mentioned). --Mark PEA (talk) 22:08, 21 May 2008 (UTC)[reply]

chicory is Generally Recognized as Safe. This abstract in PubMed supports that. I actually skimmed through the whole paper; it finds chicory to be safe in rats at the doses tested, and seems to imply in the introduction that it is not reported as toxic for humans. So there is probably no reason to worry. Still, if you find a refereed journal citation that reports chicory toxicity in humans, please post it. Kindest wishes, --Dr Dima (talk) 04:31, 22 May 2008 (UTC)[reply]

Hi all,

If I had a bunch of small generators (wind turbines, or even solar panels), each of which might be producing 0-5 volts, what is the best way to collect all that power together? Can I just wire them up in series? Will the fact that they're not all producing the same amount of power be a problem?

Thanks! — Sam 18:52, 21 May 2008 (UTC)

When you say "power" are you talking in the technical meaning of that word or are you concerned about different voltages from different sources? The (DC) voltages don't matter. You can (for example) connect up a 1.2 volt battery to a 9 volt battery and make a 10.2 volt source and it'll work just fine. HOWEVER: Imagine you took a 2 Gigawatt nuclear power station and had it produce a 9 volt DC output - and connected THAT up in series with your 1.2 volt AAA battery and tried to use the resulting 10.2 volt source to power a small city. The battery would (of course) vaporize in the first gajillionth of a second! So you have to bear in mind that each device is conducting the current for the entire series of devices. Also, if your devices are (for example) small AC generators being turned by hamster wheels - then their voltage oscillations would not be in sync because some hamsters run faster than others. The result would be that your final output voltage would be bouncing around all over the place. Not good! 71.155.164.147 (talk) 21:22, 21 May 2008 (UTC)[reply]

You are only going to be able to produce the current that the lowest current device produces. So if your solar panel can make on amp, but your wind generator 2 amps, you will only get half its power. It will be better to get a special circuit in a box to combine the power by doing DC-DC conversion, and that can draw appropriate current from each source. If you have AC generators, you will have even more troubles, as you have to match the phase produced, else one will cancel out the other! Graeme Bartlett (talk) 21:56, 21 May 2008 (UTC)[reply]

Snails visit my garden and eat my plants. Sometimes I remove them and take them to a field 50 metres from my home. I'm sure they come back! Has there been any work done on the homing instinct of snails and the distances involved? Any links or information would be appreciated. Thanks S Snailsaregreat (talk) 19:46, 21 May 2008 (UTC)[reply]

How do you know these are the same snails? Start marking their shells with an X using a permenant marker - then you'll know if they are "homing" or whether there are just a lot of snails around. 71.155.164.147 (talk) 19:49, 21 May 2008 (UTC)[reply]

Thanks - will try this but still curious to know if there is any research on snails homing instinct? Snailsaregreat (talk) 19:52, 21 May 2008 (UTC)[reply]

A quick scan of a Google Scholar search looks like there is some research suggesting a degree of 'homing'. Angus Lepper^{(T, C, D)} 20:15, 21 May 2008 (UTC)[reply]

A positive control is a procedure that is very similar to the actual experimental test, but which is known from previous experience to give a positive result. A negative control is known to give a negative result. The positive control confirms that the basic conditions of the experiment were able to produce a positive result, even if none of the actual experimental samples produce a positive result. The negative control demonstrates the base-line result obtained when a test does not produce a measurable positive result; often the value of the negative control is treated as a "background" value to be subtracted from the test sample results.

What does "positive", "negative", "positive result", and "negative result" mean?68.148.164.166 (talk) 21:34, 21 May 2008 (UTC)[reply]

See truth value and null result. A positive control should be a sample which is known to produce a true result for a given proposition. A negative control should be one that is known to produce a false result. These can be used to test the validity of the procedure and/or possibly for calibration of results. For example, if you are testing whether samples are over 5 grams of mass (a ridiculous though concrete example), a positive control might be a bowling ball and a negative control might be a penny (~1g). I guess that is just a restatement, but I'm not sure what else you are looking for. --Prestidigitator (talk) 22:18, 21 May 2008 (UTC)[reply]

A "positive result" is "whatever data would indicate something is present or worked" and a "negative result" is "whatever data would indicate that thing is absent or didn't work"; it's all in relation to a specific experimental subject or design or detector. Think of an experiment to examine radioactivity in various samples using a Geiger counter. A "positive control" might be something that is known to be radioactive and a "negative control" would be something that is known to be non-radioactive. You test each one and make sure you get the expected readings: a "positive" detection of radioactivity for something that is and a "negative" (non-) detection of radioactivity for something that is not. You can thus calibrate instruments and data analysis for when you test things whose radioactivity is not known. DMacks (talk) 22:20, 21 May 2008 (UTC)[reply]

Can BritaTM Containters Leach Bisphenol A? Are they made of polycarbonate? Are they made of a plastic that can leach BPA?68.148.164.166 (talk) 21:40, 21 May 2008 (UTC)[reply]

I am doing the Egg Drop in science class, but I can't figure anything out! I only have straws, paperclips, and masking tape. What am I supposed to do???!!! —Preceding unsigned comment added by 66.92.160.148 (talk) 21:43, 21 May 2008 (UTC)[reply]

Do you have an egg? Is this a competition to see how far you can drop an egg without breaking? Graeme Bartlett (talk) 21:59, 21 May 2008 (UTC)[reply]

I assume (because it's a science class) it's this type of Egg drop competition as opposed to some sort of cooking class contest:) The whole point is that you figure out what to do. Be creative! What are some ways you can keep the egg from falling so fast? What are some ways you can keep the egg from into the ground so hard? What are some ways you can keep the egg from breaking when it hits the ground. You actually won't learn a thing if you just do what someone else tells you. DMacks (talk) 22:13, 21 May 2008 (UTC)[reply]

Well, we aren't allowed to do your homework for you. But here are some things that might help: You're trying to stop the egg from breaking when it's dropped - right? Think about the kinds of things that we do to stop people from breaking when they are hurled violently at a block of concrete. What happens in a car crash for example? The person is held inside the car by straps - and the car is designed to crumple to absorb the energy of the crash. Could you build something around the egg that would crumple on impact? Could you restrain the egg inside that thing to stop it flying forwards into the ground? How can you join straws together to make a structure? Suppose you wanted some straws to be strong and others to be more easily crumpled? How might you do that with the things you have? 71.155.164.147 (talk) 22:11, 21 May 2008 (UTC)[reply]

Algebraist suggest that our article, egg drop competition might be useful. 71.155.164.147 (talk) 22:14, 21 May 2008 (UTC)[reply]

Clicking on SPORTS-RECREATION then HYDRATION PACKS then VIEW ALL then 100 OZ (2.95 L) then STOAWAY 100 OZ on [14] will get you the StoAway 100 oz. Does the StoAway 100 oz use BPA or polycarbonate or any other plastic that leaches Bisphenol A? Thanks!68.148.164.166 (talk) 21:54, 21 May 2008 (UTC)[reply]

Our article, egg drop competition, might be useful. Algebraist 21:57, 21 May 2008 (UTC)[reply]

Probably not. Which is a shame because the previous questioner might have found it interesting. 71.155.164.147 (talk) 22:13, 21 May 2008 (UTC)[reply]

FWIW, I think someone deleting an earlier section while I was typing was responsible. Algebraist 22:18, 21 May 2008 (UTC)[reply]

Why don't you try contacting the manufacturer? --Shaggorama (talk) 04:38, 22 May 2008 (UTC)[reply]

Alternatively, you can just read the website. Franamax (talk) 08:45, 22 May 2008 (UTC)[reply]

I'd like to shorten my very early morning walk to the commuter rail, which I currently walk to. Is there anything that is, like, I don't know, a rollerskate that goes over your shoes, for example, or a collapsible skateboard or longboard, or unicycle or bicycle (the very small, trick kind). I just want to shorten my walk by a little bit, the main requirement is I be able to collapse it, preferably flat, and put it away/out of sight. No one should know I have it. I'm inspired by these kids I see who have trick sneakers that magically contain a wheel too, you know what I mean? —Preceding unsigned comment added by 87.88.122.226 (talk) 22:34, 21 May 2008 (UTC)[reply]

p.s. if I can avoid it I wouldn't like to use a full-sized bike, or even a bulky half-way collapsible one I've seen some people take on the commuter rail.

p.p.s is this any faster than walking?? It seems because you can't "coast" at all, and there are no gears, there should be no leverage, ie no different from applying feet directly to the ground by walking. But maybe I'm missing something. So would someone on an "ultimate wheel" be able to ride it faster than the same person walking with the same 'intensity'? Thank you. —Preceding unsigned comment added by 87.88.122.226 (talk) 22:53, 21 May 2008 (UTC)[reply]

Magic carpet? --hydnjo talk 22:55, 21 May 2008 (UTC)[reply]

We have an article on the subject of that link: Ultimate wheel. I don't believe such a device would shorten your walk. You can view videos of it on YouTube; it's difficult to ride and not fast. You want something that can coast, but not the even more difficult impossible wheel! A skateboard with fold-out wheels is an interesting idea although I am not aware of one that's being marketed. The closest thing I can think of is the Wave skateboard, which is a two-wheel tandem design that might fold compact, although I'm not sure.

A Razor (scooter) or a foldable scooter of similar design might suit your needs. --Shaggorama (talk) 04:37, 22 May 2008 (UTC)[reply]

How do diketopiperazines occur in humans?68.148.164.166 (talk) 17:48, 21 May 2008 (UTC)[reply]

The article explicitly tells you how they are made and gives examples/links for some specific examples. DMacks (talk) 18:40, 21 May 2008 (UTC)[reply]

Um, no actually it does not explain how diketopiperazines occur in humans.68.148.164.166 (talk) 21:56, 21 May 2008 (UTC)[reply]

Perhaps you'd better explain further what you mean by "how". Do you mean what creates them ("how"=="method") or what compounds have them ("how"=="form") or why they are there and what they do ("how"=="how come")? DMacks (talk) 22:07, 21 May 2008 (UTC)[reply]

My original question was if diketopiperazines even occurred in humans at all. What creates diketopiperazines, what compounds have diketopiperazines, why are diketopiperazines in humans, and what do diketopiperazines do?68.148.164.166 (talk) 23:06, 21 May 2008 (UTC)[reply]

They are found in mammals per the article; chasing the cited refs says specifically rat/mouse. They are present in biological systems as the result of a certain type of enzyme per the article; googling for the enzyme and "human" gives many hits that say that enzyme is present in humans. I don't know if anyone has specifically looked for this particular structure itself in humans. So they almost certainly are present in humans (both the enzyme and substrate are present). DMacks (talk) 23:37, 21 May 2008 (UTC)[reply]

Where and how does aspartate occur in humans, if even?68.148.164.166 (talk) 23:24, 21 May 2008 (UTC)[reply]

"Aspartic acid is also a metabolite in the urea cycle and participates in gluconeogenesis." DMacks (talk) 23:43, 21 May 2008 (UTC)[reply]

Aspartate would be everywhere, as it is a common amino acid present in virtually all proteins. Woodlore (talk) 01:25, 22 May 2008 (UTC)[reply]

Do computer mice use plastics that might contain Bisphenol A? Are plastics that are made from Bisphenol A used in Bisphenol A? Do speakers use plastics that are made from Bisphenol A used in Bisphenol A? Do wires use plastics that are made from Bisphenol A used in Bisphenol A?68.148.164.166 (talk) 23:31, 21 May 2008 (UTC)[reply]

The Bisphenol A article may be of some use. It exists in most plastics as an antioxidant and/or polymerization inhibidor, and is necessary for polycarbonates and epoxies. I believe computer mice and speakers use polycarbonate, although wire cladding is likely PVC (which also contains bisphenol A). The chemical is an aid in plastic manufacture, it's there for the convenience of manufacturers. ~Amatulić (talk) 23:42, 21 May 2008 (UTC)[reply]

Why? Are you licking any/all of these things? —Preceding unsigned comment added by 96.242.34.177 (talk) 00:33, 22 May 2008 (UTC)[reply]

I found this little guy under a rock in the water. Does anybody know what it might be? Sorry about the blurry picture; it didn't like to stay put. Djk3 (talk) 00:58, 22 May 2008 (UTC)[reply]

Looks like a Dragon fly larvae. But that's a big ballpark. --71.236.23.111 (talk) 01:33, 22 May 2008 (UTC)[reply]

I think it's an earwig. Dragonfly larvae don't have such antennae AFAIK. If you want to be sure, dragonfly larvae have a very peculiar "mask" (labium) which can project forwards to catch prey; you can't see if it is present in the photo you posted, but this is how you can tell the dragonfly larva from anything else on this planet. Hope this helps. --Dr Dima (talk) 04:14, 22 May 2008 (UTC)[reply]

It wasn't an earwig. It was definitely some sort of water-dwelling thing. It was completely submerged, and when I lifted the rock out of the water, the thing went right back under water. Djk3 (talk) 05:43, 22 May 2008 (UTC)[reply]

Is there a way to find out what is the correction for local mean time for a given locale or longitude? For instance, although Boston and Philadelphia are in the same time zone, local noon (when the sun is highest in the sky) will occur at different times because Philadelphia is maybe 200 miles west of Boston. In the days before time zones, there must have been charts or guides for travelers, no? Woodlore (talk) 01:26, 22 May 2008 (UTC)[reply]

Every 15 degrees of longitude equals a 1-hour difference. Every degree of longitude equals a 4-minute difference. And so on. So if you know the universal time (which is the time at zero degrees longitude, you can easily calculate the "local" time at any longitude. ~Amatulić (talk) 01:36, 22 May 2008 (UTC)[reply]

Perfect-- thanks amatulic Woodlore (talk) 01:45, 22 May 2008 (UTC)[reply]

See also Equation of time.--Shantavira|^{feed me} 06:33, 22 May 2008 (UTC)[reply]

What is the magnetic moment of a single iron atom. Thanks, *Max* (talk) 01:56, 22 May 2008 (UTC).[reply]

it lives in brazil and i think it lives in lakes and rivers. if a man pees in the water the fish will swim up his penis. —Preceding unsigned comment added by 216.228.178.218 (talk • contribs) 14:19, 22 May 2008

You'd be thinking of the Candiru. Confusing Manifestation(Say hi!) 03:29, 22 May 2008 (UTC)[reply]

This morning it so happened my sister was involved in an accident, when she lost control of her small rental car after being dragged into the slipstream of a passing tractor trailer in Tennessee. ( Miraculously, she walked away with only minor injuries despite her car being dragged along by the truck, flipping, and hitting a tree.) But in the course of her talking with people in the area, there seemed to be a consensus that this happened more frequently with 'fully loaded' trucks. I think the implication is that the weight of the truck somehow affects the strength of the slipstream. I'll admit I'm no graduate student in physics, but this doesn't make much sense to me. While a fully loaded truck would have more kinetic energy and momentum, I would think that the shape of the truck and its speed were the only factors affecting the slipstream, and while I could come up with something involving momentum and collision with air molecules, I don't really buy it. Any ideas? —Preceding unsigned comment added by 68.112.229.82 (talk) 05:01, 22 May 2008 (UTC)[reply]

The only way someone could even know a truck was "fully loaded" would be an open-bed trailer loaded with cargo. In that case, there would be much more turbulence than from an empty flat-bed trailer. A closed van would create the same air disturbance, no matter what was inside. However, I'm not a PhD either ;) Franamax (talk) 08:16, 22 May 2008 (UTC)[reply]

How long does an adult flea, which has had a blood meal, live ? (ie. If there are adult fleas in my house, how long do I need to vacate the house before they die of starvation ?)

How long does a newly hatched flea live without a blood meal ? (eg. if my house is vacated for a week, then I visit to jump about and make vibrations to cause any unhatched fleas to hatch, how long to I need to remain absent to cause the new hatched fleas to die die of starvation ?)

How long does it take to drown a flea ? (ie. could clothing be submerged in water for,say, 2 hours to drown fleas and ensure their removal ?)

Signed:Jennylindmac (talk) 08:01, 22 May 2008 (UTC)[reply]

Ugh, fleas. Don't scratch the bites. If the flea has had a blood meal, it will be in position to lay eggs. According to this, the adult can live two months to a year without a meal. According to the same link, the flea can develop to adulthood inside the pupa and survive for months as long as they don't emerge. Running your clothes through a normal wash and dry should take care of any adults and eggs on the clothing.

I went through a bad experience with fleas (I now know why they call them "flea-bag motels") that got in my bedroom at home. Washing, vacuuming and putting down powder would work for about three days, then I got bitten again. Eventually, moving and leaving the bed unslept in for three months solved the problem. Hopefully your experience will be better! Franamax (talk) 08:30, 22 May 2008 (UTC)[reply]

RTI International is

The second largest independent nonprofit research organization in the United States....

— RTI International

.

Which is the first?68.148.164.166 (talk) 10:08, 22 May 2008 (UTC)[reply]

Can anyone help me explain to my 5 year old daughter why it's still daylight when we send her to bed? Obviously this is not because we send her to bed in the afternoon - her bed time is 7.30/8.00pm, it's just light in the summer and dark in the winter.

thanks spiggy 83.104.131.135 (talk) 10:15, 22 May 2008 (UTC)[reply]