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May 4

The Unidentified Crawling Objects

What are they? these pictures are taken in New England. -- Toytoy 01:38, 4 May 2007 (UTC)[reply]

Possibly a centipede? Nimur 01:45, 4 May 2007 (UTC)[reply]

(ec) They're house centipedes. They are harmless to humans, but not to any roaches, flies, or spiders thinking about moving in with you. --TotoBaggins 01:48, 4 May 2007 (UTC)[reply]

Actually, not completely harmless... I got bitten on the foot by one last summer while I was on holiday (in the Dordogne in France) and it hurt a lot more than I was expecting. The next day I was emptying the bin and I got bitten/pinced/whatever by a European mantis. Gah. --YFB ¿ 01:54, 4 May 2007 (UTC)[reply]

Their bite is supposedly equivalent to a bee sting, ouch! But they do eat all the other bugs in your house. So if you can avoid them, they are best to leave alone, as they are like brilliant little roach-hotels running around killing other intruders. --Cody.Pope 09:01, 4 May 2007 (UTC)[reply]

When they are being attacked, they may shed legs (see the left image). What's wrong with them? -- Toytoy 02:27, 4 May 2007 (UTC)[reply]

Complete speculation, but I guess that they will shed a few legs so that a predator will be happy with that small, easy meal rather than the larger meal that is running away. 213.48.15.234 08:05, 4 May 2007 (UTC)[reply]

it looks like it has been squashed--Lerdthenerd 09:05, 4 May 2007 (UTC)[reply]

No. I didn't do anything other than spray insectide (I know it's not insect). It just breaks apart. -- Toytoy 15:54, 4 May 2007 (UTC)[reply]

Length of Legs

In human beings, which leg is usually longer, the upper leg or the lower leg? Does the relative lengths of the legs of human beings depend on gender, race, or age?The Anonymous One 08:59, 4 May 2007 (UTC)[reply]

I don't know about you, but I have a left and right leg, both of which are pretty similar in length. 213.48.15.234 09:53, 4 May 2007 (UTC)[reply]

Check out tibia, femur, and fibula. The femur, the bone of the "upper leg," is always longer (though I guess you could have a wierd mutation). The fibula (one of the bones of the "lower leg") differs in shape between genders. Also note that "upper leg" is more accurately called the thigh, and the "lower leg" is the leg itself. Someguy1221 10:30, 4 May 2007 (UTC)[reply]

The relative lengths depend on whether you go to a chiropractor doing "free" public screenings. Unless you appear unable to afford a series of adjustments, he will demonstrate a discrepancy and offer to fix it.[1][2] alteripse 11:25, 4 May 2007 (UTC)[reply]

Well, that is rather biased, and it doesn't seem to address the original question. I went to a Chiropractor for some back problems, and I could afford treatment. He commented that I had a good symmetrical stance, and had an even walking rhythm. He physically examined my back and was able to point to the exact spot (with out me telling) where I was hurting. He adjusted my back, and I think that is was definitely worth it. The ever present low grade pain that I had been living with for over a year was gone. To me this was a much better treatment that the pain killers and muscle relaxants that I had been given when I originally hurt my back. Chiropractic treatment can't cure cancer, but sometimes people do benefit from it. -Czmtzc 12:49, 4 May 2007 (UTC)[reply]

Chiropractors can help if you genuinely suffer from a pinched nerve. Unfortunately, the lack of regulation has also led to a world full of chiropractic quacks. StuRat 23:49, 4 May 2007 (UTC)[reply]

Maglev Speed

This question was placed in the article JR-Maglev by Chris apodaca . I will tell him/her that I reposted it here.--MrFish^{Go Fish} 11:40, 4 May 2007 (UTC)[reply]

Is it true that a maglev train can be powered to the speed of light if it did not have to worry about aerodynamics.

1. With today's understanding of science, Nothing with mass can be accelerated to the speed of light. It's impossible.

2. Even with absolutely no atmosphere to slow the train with viscous drag, there would be friction created by other effects in the magnets (depending on the type of maglev used).

3. How on Earth would you turn a corner going at the speed of light with mass? 213.48.15.234 11:58, 4 May 2007 (UTC)[reply]

Doesn't light have mass? How else could it be effected by gravity? Jeffrey.Kleykamp 12:19, 4 May 2007 (UTC)[reply]

No, photons have no rest mass. They are affected by gravity anyway, general relativity being like that. Algebraist 12:28, 4 May 2007 (UTC)[reply]

Mass bends space. Therefore even massless object curve around massive objects, because the space is curved.Czmtzc 15:46, 4 May 2007 (UTC)[reply]

Well, it bends spacetime. Capuchin 21:37, 4 May 2007 (UTC)[reply]

An extremely high speed maglev in an evacuated tunnel could benefit from two systems:

1) A straight line could be drilled between each pair of stations. This would mean it would go deep underground in the middle. The pairs of stations would need to be fairly close, or the depth in the center would go down too far, where the temperatures are extremely hot. The advantage of such a system is that no energy would be needed for acceleration and decel (other than to overcome any residual friction), as gravity will slowly accelerate the train at the start and decelerate it at the finish.

2) A train following the curvature of the Earth and going at the proper speed would have a centrifugal force equal to gravity, so wouldn't need any energy to levitate it, as it would essentially be in orbit at ground level. The speed of escape velocity at the Earth's surface is 11.2 kilometers per second (~7 mi/s). This system would only be suitable for very long distances between stations, such as London to Tokyo, and would certainly kill everyone on board in an accident.

Hybrid systems, that go deeper in the middle but still somewhat follow the Earth's contour, or trains that go a substantial fraction of the escape velocity at the surface, could also be used. StuRat 23:35, 4 May 2007 (UTC)[reply]

Plant life

I have a Mermaid Vine houseplant that must be sixteen years old.It definitely looks past its prime.Do houseplants have recognised life spans as do,for instance,trees? Where can I find this sort of information? —The preceding unsigned comment was added by 86.13.217.242 (talk) 13:44, 4 May 2007 (UTC).[reply]

Yes, an individual Mermaid Vine plant (probably Cissus sp.) has a definite life span. Propagating it by cuttings "resets the clock" for the new plants; but, sadly, not for the parent plant. See Vegetative reproduction. Dr_Dima.

As for the more general question, some plants do have life spans (especially annuals), while others don't, and survive as long as all the proper conditions remain for their survival. StuRat 23:12, 4 May 2007 (UTC)[reply]

The knowledge needed to start from scratch

I quite often wonder what would happen if you take a few thousand modern-day people from around the world and make them the only survivors of an apocalypse - and in this hypothetical let's assume all technology was destroyed and all the resources we had were back to their natural forms - the sea, jungle, forest, grassland, etc.
So to clarify there would be no records of information, no manuals, textbooks, nothing - just natural resources - heck maybe the people are even naked to begin with.
All that they have left are memories and the knowledge they had before the apocalypse.

I then wonder how much technical knowledge is needed among people to do these various things:

Manufacture metal
Generate electricity
Build a computer
Build a labroratory
Fly a rocket
Etc

How possible is it to do those things from absolute scratch using only natural resources? - in other words in order to harness metals it would be extremely difficult to do without metal tools
Similar to the previous question, is it in the power of a single person to posses the knowledge of these things (see list above) - or is it currently highly unlikely that a single person possesses the knowledge to do all these things.

Any thoughts or references to these types of questions would be appreciated.
Rfwoolf 14:04, 4 May 2007 (UTC)[reply]

Metals don't have to be particularly difficult. Fire, wood, and clay are easy enough to get hold of; from there you get to kilns, pottery, charcoal, and ceramics—all the tools you'll need for very basic metalwork. (A post-apocalyptic world would actually have gobs of refined metals just lying around, but you've stipulated that all of that has been lost.) With very modest tools you start being able to gather coal, which lets you make steel. It's time consuming to scale up these technologies from scratch, but certainly not impossible.

Once you have coal, metal tools, water-powered mills, and the capacity to smelt metals, you're able to start doing things like draw wires and machine metal. That gets you to electricity, if you want it.

Early electronic computers (vacuum tube-based) could have been built using technology available in Thomas Edison's time, though you'd really want electrically-driven mass production equipment. Semiconductors to build transistors are going to cost you another whack of time and effort to get pure silicon or germanium. Really, it's all a bootstrapping issue—since we already know how to do all of the things listed, it's just a matter of building the infrastructure (adequate supplies of fuels, metals, tools, and electricity) to support each task. TenOfAllTrades(talk) 15:07, 4 May 2007 (UTC)[reply]

There's also a question of critical mass. At the hypothesized level of "a few thousand", you clearly won't have a biological store of all of the accumulated specialties of knowledge. You'll also be polluted with a great many people who believe they "know" something, but are quite, quite wrong; it wouldn't take many of those folks to undo all the correct knowlegde brought forward. And finally, a few thousands aren't enough to immediately do everything needed to be done to restore technology. Imagine how many people it takes to build a big hydroelectric dam, for instance (especially when you trace back everything that goes into the dam).

Maybe we'd better hope that a good copy of Wikipedia survives and that it wasn't too vandalised when the snapshot was taken?

Atlant 16:02, 4 May 2007 (UTC)[reply]

(adding some paragraph breaks per Atlant:)Yes, a copy of Wikipedia or Diderot's encyclopedia or Britannica (even th e 1911 edition) would be pretty useful. If it did not contain detailed plans for every doodad they needed, at least it could steer them toward things that were doable and away from alchemy and efforts to build perpetual motion machines or find the fountain of youth. Prisoners of war in Hanoi pooled their memories to reconstruct Bible passages, fo a coterie of scientists could make some papyrus and write down most of Halliday and Resnick's physics textbook, etc. The premise allows for post-apocalypse people in a non-post-apocalypse world. After any conceivable natural or man-made event such as giant asteroids striking, nuclear war, biological war, or the global triumph of some vicious ignorant tribe of Luddites, there would be a virtually inexhaustable supply of steel, copper, lead, brass, aluminum and every other useful metal. Native Americans quickly adapted from flint arrowheads to ones made form scavenged metal when Europeans moved in. In some developing countries, they can't keep guardrails in place along highways because the steel is such a handy thickness for fabricating tools. The ruins of buildings would furnish vast quantities of rebar, steel columns, steel and copper from pipes, and steel from beams and columns, as is evident if you watch the recycling which goes on when a building is demolished.

If nasty space aliens somehow used nanomachines to remove all our buildings, roads, sunken ships, buried pipelines, etc, then we would not be back in the world that our primitive ancestors found, because all the easily found petroleum, coal, and ores would be long gone. Your scenario would have to move modern people back through time to the primordial past, or to a different but similar unspoiled planet. In such a world, assuming it was like pre-Columbian America but without the native population, with the mineral exploitation clock reset to zero, on day one some survival specialists who knew how to make stone tools and start a fire without matches would be invaluable, as would be hunters and fishermen, as well as people who are born leaders to keep the people rational in a challenging situation. An historian of science and technology preferable who has worked in industry and with woodshop and metalshop skills, would need a labor force to do the drudge work of cutting and hauling wood and stone, and digging in the ground to extract mineral ores. You use flint to make flint tools, which can make wooden wedges to split trees into planks and to quarry stone. You use fiber to make rope, which combined with strong backs can move large stones and timbers to make structures. Animal hides bones and sinews are very useful in the beginning. A few Boy Scout and Girl Scout vets would be useful, along with military people who have survival training.

In a year or two they should be at the level of the native populations of pre-Columbian America, but likely with a large death toll due to starvation and disease. Agriculturists would be needed to feed those workers, and doctors (hopefully with a knowledge of medicinal plants) to keep the work force healthy. Someone would need to start in selectively improving the native plants and domesticating cattle, sheep, goats, equine species, and dogs, as well as bees and hopefully silkworms. You need hides, wool and and plant fiber for clothes and industrial processes. Domesticate cats and you lose less of your grain crop to rodents. Carpentry and stoneworking skills would be needed to build the first generation of factories (due to the lack of iron and steel). The metallurgist would have lots to plan. Coal, timber and iron ore were readily available in many countries. Tin and copper make brass. Zinc and copper provide batteries. Mercury and glass allow good vacuum pumps. (You did include glassblowers? Shoemakers, seamstresses, brickmakers, boatmakers, and all the trades whose work spawned descendent's names: wainrights, coopers, bakers, brewers, turners, cordwainers, weavers, schneiders, etc?) Chemists would have to start producing basic industrial chemicals such as sulfuric acid and chlorine. Water power and steam engines fueled by coal could be the first generation prime movers to power big factories with overhead shafts driving belt operated tools, the first generation of which could be primarily wood with iron cutting surfaces. There were a few big iron meteorites from which natives obtained iron for tools. Given ore, stone for furnaces, and forests for charcoal, our ancestors made lots of iron with low tech furnaces. Metal allows movable type which allows books to preserve the knowledge in the memories of the first generation. Some engineers and architects and urban planners would be helpful to avoid stupid mistakes in putting up buildings and laying out towns. Chemists hopefully had the periodic table pretty well memorized before they left. Mathematicians should get to work building slide rules and calculating math and trig tables.

The second generation of technology would be able to extract copper and draw wire, and insulate it with cotton or silk. Now you can make dynamos, power lines, transformers, motors, arc lights for public spaces, and electric lights for homes. Light bulb technology allows vacuum tubes and you have radio and computers. Given a hypothetical Eden, there should be an increase of population to furnish the labor and adundant raw materials, such that your "few thousand" well prepared individuals could (optimistically) have early 20th century technology in 30 to 50 years, starting with a "few thousand" well prepared Robinson Crusoes.Look at the Amana Colonies for an example of colonists numbering about 1000 who migrated from Europe to the the east coast of the U.S then to the midwest, who were largely self sufficient, with people of each generation in the late 19th early 20th century assigned to print books, make shoes, build excellent furniture, brew beer, etc.) Edison 16:07, 4 May 2007 (UTC)[reply]

Gee, Edison, surely the paragraph break would survive, wouldn't it?

Atlant 16:31, 4 May 2007 (UTC)[reply]

First up you'd need a food supply, which means farming knowledge. The industrial revolution was kick-started by the green revolution. But the very basics, like the specifics of crop rotation would need to be known or rediscovered. Once that's in place, we can branch out a bit. Even fairly simple science can be difficult to impliment, as anyone who's watched Rough Science will know. Then it'd be a race against the clock, as you wouldn't have anyone with first hand knowledge in under 100 years, but knowledge can be passed on to the next generation, I guess. --h2g2bob (talk) 16:13, 4 May 2007 (UTC)[reply]

Do you mean the British agricultural revolution, h2g2bob? Algebraist 17:34, 4 May 2007 (UTC)[reply]

I've thought about this question a lot. My favorite critical technology -- not mentioned so far -- is the lathe. It's essential for forming threaded parts like screws, but it contains as one of its essential components a long lead screw, so there's a nicely-encapsulated bootstrap problem there. —Steve Summit (talk) 15:03, 5 May 2007 (UTC)[reply]

Nice to see that other people have similar thoughts. Often if there is nothing else that can be done I wonder how human progress (in a very broad sense) could be improved if we could use a hypothetical time machine to send something back in time. I imagine several levels of possibilities of such time travel. One, to go back in a kind of spacetime ship, carrying usefull things. Two, go back as a spirit only and take over the mind of someone living at that time. Three, be preborne back in time, with old knowlage becoming availabe as you grow up. Four and five, establish two way or one way information transfer to someone living in the past, for example, by apearing in their dreams.

Now that I see I'm not alone I wonder and ask if anyone knows of other people who have these things more elaborated, perhaps written down or in some kind of (please, non too fictional!!?!) discussion forums? 84.160.226.72 20:50, 4 May 2007 (UTC)[reply]

I would say we need science to progress slower, so it doesn't outpace social developments, as it has in our world. We now have tribal societies (like Pakistan) in possession of nuclear weapons, not a good combo. StuRat 22:58, 4 May 2007 (UTC)[reply]

As I remember the first two nuclear bombs that were actually used for mass destruction didn't come from a tribal society. I hear that the majority of US soldiers in Irak were in pro of torture. Democracy does not make better people, it only provides more efficient means to deal with internal conflicts. 84.160.226.72 08:01, 5 May 2007 (UTC)[reply]

You might be interested in the book Earth Abides, by George R. Stewart. While the setup isn't quite the same as yours (technology was preserved, but very few people survived a plague), the direction it takes is quite interesting, dealing with the loss of a "critical mass" of humanity. Ultimately, the remaining people aren't able to maintain the infrastructure and they lose their technology (as when they can't keep a forest fire from destroying the town) and even lose their belief in science, instead resorting to primitive beliefs (somewhat similar to what happens in Lord of the Flies). StuRat 22:51, 4 May 2007 (UTC)[reply]

I recommend All_the_Weyrs_of_Pern. You need to read the novel, you won't get enough from the Wikipedia article. DGG 23:01, 4 May 2007 (UTC)[reply]

This all is just tip of the iceberg and you have only uncovered the whole genre of Alternate history. One of my favorite book genres :) One of the biggest problems of a society without any books, computers and such would be transfer of education. In first years there would be an imperative on everyone having to help grow enough food and other essential stuff, and it will be become harder and harder to preserver higher-level knowledge. Pern examines that nicely, but even they started with books (that deteriorated after hundreds of years). And who knows what would happen without AIVAS... In 1632 series a whole town is transported back in time to year 1632. But with books, computers and so on. Even so, after 3 years there are many large problems, some of them to do with access to rare ores, producing stainless steel and so on. Baen's Bar has a lot of discusion about this at [3] (registration required). Shinhan 12:40, 5 May 2007 (UTC)[reply]

DGG above recommended "All the Weyrs of Pern", but another Anne McCaffrey book probably matches the premise even closer: Freedom's Landing. Not so much post-apocalyptic as "humans abducted by aliens and dropped on an empty planet" (which is not entirely correct but sums up how things look at the start). Confusing Manifestation 23:11, 6 May 2007 (UTC)[reply]

The death rate would probably be very high, because with antiseptics (see hygiene hypothesis) modern people have weaker immune systems than pre-civilized people. On the other hand, we understand sanitation better. On yet another hand (??), the majority of North American Native American groups tended to have few sanitation problems due to low populations and mobility, and their life expectancies weren't all that high. 24.167.75.163 02:11, 7 May 2007 (UTC)[reply]

Feedback from the asker

Thank you all so very much for your feedback on this, all the answers have been very interesting. I suppose I should have rephrased the question as "What if a few thousand people with the top technological knowledge were all transported back to pre-civilization with only the clothes on their backs and their knowledge, skills, and memories."
One of the questions that wasn't answered however was the one about whether or not there are individual people out there that have the knowledge to recreate a technology from scratch - so even though it may take thousands to build a power plant, maybe there's a guy out there that knows how to build one all by himself in a pre-civilized world. That's what I'm wondering about as well. I will be creating another question to focus on this aspect. Thanks again! Rfwoolf 13:27, 5 May 2007 (UTC)[reply]

(NB: This question was asked separately below...see answers there!) SteveBaker 15:54, 5 May 2007 (UTC)[reply]

little question

In the event of an adoption of a Non-Nuclear Proliferation Act in all countries north of the equator, would it be possible to lower the mandatory minimum military age from sixteen to six with the provisor that the agricultural marketing board would not be adversely undermined tomorrow or the day after? 138.130.23.133

Huh? I don't really get the question. Most nuclear powers already sign the Nuclear Non-Proliferation Treaty. Nuclear weapons can be fired from the southern hemisphere into the northern hemisphere and vise versa. In any case, I'm sure people will have a lot to say on child soldiers. As for agriculture, that has many international problems already, largely related to the principles of free trade conflicting with the first world's use of subsidies and tariffs related to agricultural produce. If you can clarify what you mean, we can help you better. --h2g2bob (talk) 15:58, 4 May 2007 (UTC)[reply]

Electrical conversion

Some BLDC (brushless direct current electric motor) 3 phase motors are variable speed and appear to achieve this using either frequency modulation of constant pulse width (50% duty cycle), constant voltage and constant current or by pulse width modulation at constant frequency, constant voltage and constant current. I do not know which one predominates.

My question is how do you convert volt amps (VA) to watts (W) for such motors?

Would you calculate three-phase conversion as follows:

("POWER FACTOR" means motor efficiency, which best follows the applied power and RPM according to a tilted parabolic curve with a maximum of .80 at 300 RPM)

       WATT (W) = VOLTS x AMPERES x POWER FACTOR x 1.73
                                                                                 
       36x20x1.73 = 1245.6   1245.6 * .80 = 996.48 W

71.100.2.43 14:52, 4 May 2007 (UTC)[reply]

Please provide the words behnd abbreviations such as such as BLDC, since they may not be familiar to Ref Desk editors who are otherwise familiar with the topic of the question. Power factor makes sense with sinusoidal current and voltage. When the current and voltage are not even remotely sinusoidal, being pulses of variable duty cycle, it would seem to make more sense to simply integrate the instantaneous product of current times voltage throughout a cycle. This should be a trivial exercise when dealing with theoretical pulses. When measuring field data, recorders such as those by Dranetz and BMI can use calibrated current probes and voltage probes and a sampling process wherein analog to digital convertors sample the parameters at a high enough frequency (1000 Hz?) to capture the harmonics which contain meaningful amounts of power, then numerically integrate. These instruments should be able to print out or provide a digital record of RMS equivalent V, I, and P. "Parabolic motor efficiency" gets zero Google hits. Edison 15:20, 4 May 2007 (UTC)[reply]

In the absence of sinisodial variation then would you simply drop 1.73 but retain motor efficiency or the "POWER FACTOR" as listed for applied power and RPM of the motor to obtain the rated power in watts? 71.100.2.43 16:08, 4 May 2007 (UTC)[reply]

If you knew the integral of instantaneous volts and amps in each phase, the total is the sum of the three. Edison 16:19, 4 May 2007 (UTC)[reply]

BLDCs that are powered from 3-phase mains power almost all include power factor correction circuitry so that they draw roughly sinusoidal, phase-correlated current.

Atlant 16:34, 4 May 2007 (UTC)[reply]

Wait – a DC motor powered from 3-phase AC? That must involve circuitry to convert the AC power to (pulsed) DC, and the resulting voltages and currents on the DC side could be very different than on the AC side. Atlant is talking about the current drawn on the 3-phase AC side, but other of the above responses refer to the voltages and currents on the DC side. So to avoid confusion: is your question about the voltages and currents drawn from the line on the AC side, or delivered to the motor on the DC side? --mglg_(talk) 19:10, 4 May 2007 (UTC)[reply]

To eliminate any confusion the entire supply is from battery power and the controller does not convert (or invert) this to AC. My uderstanding is that current and voltage remain constrant and the circuit provides variable power by either modulating the width of the phase under constant frequency or by modulating frequency under a constant phase of say a 50% duty cycle or width. "Conversion" here refers entirely to conversion from Volt-Amps to Watts. 71.100.2.43 20:29, 4 May 2007 (UTC)[reply]

I see, "3-phase" referred to the construction of the motor, not to any AC power source. Thanks for the clarification. I think your assumption that both current and voltage are constant during each pulse must be invalid. The motor will define some time-varying relationship (a "load condition") between the voltage and current, imposed by the constant resistance and inductance of the motor windings together with the time-varying back-EMF caused by the rotating magnets. The driver will impose a "driving condition" (effectively open-circuit when the pulse is off, and either constant voltage or constant current (or most likely an intermediate case, which can be thought of as constant voltage plus internal resistance) during the pulse, onto the windings. The load condition and the driving condition will together define the voltage and current. Because the resulting voltage and/or current will vary with time, even during each "on" pulse, the best answer I can come up with is Edison's advice to integrate the instantaneous product of current times voltage throughout a cycle. --mglg_(talk) 21:03, 4 May 2007 (UTC)[reply]

Thanks for explaining the abbreviation. These motors should have clear advantages over brush type motors in low power, light weight application. Nikola Tesla would have heartily approved. The article says DC controllers feed full positive and negative power to two of the legs at a time. It should be possible to get better efficiency by using sinusoidal currents, which could be approximated from a battery supply through suitable electronics. Variable frequency power supplies are made for motors in the thousands of horsepower, which convert AC to DC and back to variable frequency AC for "soft starts" to eliminate the flicker caused by the starting of huge motors. If it works for kilovolts and kilohorsepower, it shoudl be easily implemented for the power levels you quote. Edison 22:51, 4 May 2007 (UTC)[reply]

I understand that it is an option but at significantly greater controller cost (two to three times maybe or more). Some motors I've seen try to deal with the problem of jerky starts by skewing the stator teeth and thereby to keep costs low (but then charge twice as much for this inovation). While Nikola would probably approve electronically produced AC from a DC supply for AC induction as a good thing I'm not so sure about skewed teeth as anything else but slight edge up on the competition. As LED STARS seem to have significantly increasing the efficiency of using current to produce lumens innovations that wpuld do the same for induction would be remarkable. 71.100.2.43 02:30, 5 May 2007 (UTC)[reply]

black hole

why there is blackholes ? —The preceding unsigned comment was added by 213.42.21.151 (talk) 16:37, 4 May 2007 (UTC).[reply]

See the cunningly named article black hole. Algebraist 17:30, 4 May 2007 (UTC)[reply]

If you do not understand the article fully, feel free to come back and ask a (more specific) question. Also, try typing something you want to know about in the search box at the top of this page to the left. [Mac Δαvιs] ❖ 18:41, 4 May 2007 (UTC)[reply]

Indicator for presense of Humalog® insulin

What chemical indicator would react by changing color to the presence of Humalog insulin on fabric by a color change, whether the fluid is present in a dried or liquid state? The insulin (which is clear) is described as follows: "Each milliliter of Humalog® insulin contains insulin lispro 100 Units, 16 mg glycerin, 1.88 mg dibasic sodium phosphate, 3.15 mg Metacresol, zinc oxide content adjusted to provide 0.0197 mg zinc ion, trace amounts of phenol, and water for injection." It has a pH of 7.0-7.8. I am looking for an indicator chemical which would react perhaps with the Metacresol or some other component to provide a color change indication, but would not react with water or perspiration. Some other method such as a light source which caused fluorescence in the presence of the product would also be good. The metacresol is apparently a coal-tar derivative, strong smelling, and present as a preservative, and seems like it might be a good possibility to react with an indicator. Edison 17:26, 4 May 2007 (UTC)[reply]

Depends on if you want to destroy the fabric or not. A blacklight might work. Many organic compounds, especially aromatics like cresols and phenols, and most likely the insulin, should glow under a blacklight, although there are a lot of substances that will glow (possibly the perspiration). If you have access to a lab, a ferric chloride test might work on the cresols and phenols, but that would require trying to extract the compound from the fibers, etc, and may react with water. --Bennybp 20:32, 4 May 2007 (UTC)[reply]

Why would anyone wish to do such a thing? If you want to quantify m-cresol, perhaps you'd get lucky with something like p-dimethylaminobenzaldehyde. One can reasonably assume that it would form a dye, along the theme of Spy dust. Wot, no article on spy dust? 129.170.29.111 21:18, 4 May 2007 (UTC)[reply]

I see that an improvement could be made to insulin infusion sets used with insulin pumps. Presently the pumps will give an indication if there is blockage in the catheter, but if the insulin is leaking due to a bad connection at the infusion site, or if due to degradation of the tissues and skin over the several days the preparation is left in place, it is oozing out of the patient's skin, there is presently no way of telling except for the patient's blood sugar reading going dangerously high. An adhesive cloth patch covers the skin at the infusion site. There should generally be none of the medication around the infusion site, so an indicator sensitive to any of the components of the medication would provide a visual indication that the site was leaking, something that the brain of an insulin pump can't detect. Edison 22:11, 4 May 2007 (UTC)[reply]

Per [4] p-dimethylaminobenzaldehyde is "slightly hazardous in case of skin contact" and "Repeated exposure to the substance can produce target organ damage" so a possibility but less than ideal. Anything else that would change color in contact with Metacresol? Edison 22:37, 4 May 2007 (UTC)[reply]

The only leakage indicator you need is your nose (or someone else's if you are not a contortionist). Cresol and phenol have strong, unmistakeable odors. Sniff near the hub or at the infusion site and you will see what I mean. alteripse 00:23, 5 May 2007 (UTC)[reply]

Smell is not VISUAL as requested, and large quantities of te chemical lost would be required to allow an olfactory detection. Looking for something like phenolphtalein (which doesn't work). Edison 06:39, 6 May 2007 (UTC)[reply]

Is there a database of chemical indicators where one cold look for something to achieve the stated goal of reacting to a component of the medicine by a color change? Edison 14:17, 7 May 2007 (UTC)[reply]

Microwave Ovens

I have recently received an e-mail to the effect that research at John Hopkins reveals that putting plastic containers in a microwave oven releases dioxins which can cause cancer, especially breast cancer. True???68.106.12.232 20:10, 4 May 2007 (UTC)[reply]

No. Snopes page debunking this particular email. --LarryMac 20:24, 4 May 2007 (UTC)[reply]

THIS urban legends site provides a more comprehensive and referenced answer, and their conclusion isn't as clear-cut as Snopes'. Anchoress 23:56, 4 May 2007 (UTC)[reply]

The question specifically referenced dioxin, though. --LarryMac 00:11, 5 May 2007 (UTC)[reply]

Yes, I noticed that. Anchoress 00:16, 5 May 2007 (UTC)[reply]

However, if you microwave plastics (or foam-type containers) to the point that they melt and mix with the food, then you do, indeed, expose yourself to a variety of toxic chemicals, some of which may be carcinogenic. StuRat 22:26, 4 May 2007 (UTC)[reply]

It's generally not recommended to eat plastic, melted or otherwise ;-) Someguy1221 23:14, 4 May 2007 (UTC)[reply]

IIRC, Consumer Reports magazine mentioned years ago that there are two different chemicals used to make plastic wrap. One was low-density polyethylene and the other was Polyvinylidene chloride (sold under Dow Chemical Company's trademark of 'Saran Wrap') that used (more?) plasticizers. That second wrap was not recommened for microwave cooking, but I see from our article that Dow switched to LDPE in 2004.

Atlant 23:57, 4 May 2007 (UTC)[reply]

In a similar vein, can anyone confirm or deny that microwaving a CD produces Arsenic? --Kiltman67 02:25, 5 May 2007 (UTC)[reply]

I think you might consider rewording that question to releases Arsenic since we're talking about an element (although produces Arsenic may be sufficient in some contexts). And obviously it need be a element used in production. Root⁴(one) 03:45, 5 May 2007 (UTC)[reply]

It is apparently used "in construction of electrical semiconductors, diodes, and solar batteries" according to Occupational Safety and Health Guideline for Inorganic Arsenic and its Compounds (as As), Potential Human Carcinogen. That article was created a few years before CDs really became popular AFAIK ('88). So you might not want to microwave that solar panel or that hard drive you have lying around ;-) Root⁴(one) 03:59, 5 May 2007 (UTC)[reply]