Wikipedia:Reference desk/Archives/Science/2006 August 2

MRI Questions
I have some questions about MRI scans (specifically fMRI) that I hope you can answer.


 * 1) How loud is it inside an MRI machine (i.e. how many decibels)? Are the earplugs they give you any good at filtering out the noise?
 * 2) Do they use any radio frequency waves? Is the amount of these waves large enough to be harmful?
 * 3) Is the magnetic field harmful to the human brain? What are the long-term effects?
 * 4) Are there any other potentially dangerous/harmful things about MRIs?

Thank you!--Anakata 00:34, 2 August 2006 (UTC)


 * I have no technical info, but I can tell you it's not so bad with the earplugs. And I'm sure they're perfectly safe. Melchoir 01:32, 2 August 2006 (UTC)
 * When I went they gave me head phones to listen to any radio station I wanted. I couldn't really hear any noises, and I could also hear the mri tech through the head phones asking me how I was doing and how long each scan was going to take.

Another question: Is the noise potentially harmful to my hearing?--Anakata 02:42, 2 August 2006 (UTC)


 * Now that I don't know about. I seem to recall that the reason for the earplugs was more that the sound is annoyingly loud rather than dangerously loud... but my memory is terrible. Anyone else? Melchoir 02:59, 2 August 2006 (UTC)


 * The only thing potentially dangerous about MRI scanners are freak accidents relating to the magnets—i.e. if something metallic is brought into too close of a range with an active scanner it can be pulled into the machine (when that "something" is a gun or an oxygen tank, it can easily be fatal), or if the patient has some metal in their body they don't know about (which is why people who have worked in autoshops or other places where you can get filings embedded into you without your knowledge are generally prohibited from being in MRIs). Other than that there is no known damage to be suffered from MRI scanners, to my knowledge. It's a danger worth taking seriously but it is a side effect of the way the scanner works, not a direct product of being scanned. Statistically it is very safe (I have had it done to me personally, and there was no problem at all. In the end I got a neat picture of my brain out of it by asking the people to send me the raw datafiles). --Fastfission 03:14, 2 August 2006 (UTC)


 * So one shouldn't go into an MRI scanner with a gun strapped to one's head. The things I learn on Wikipedia. DirkvdM 08:34, 2 August 2006 (UTC)


 * The gun incident happened because there was a police officer in the room, just a bit too close to the magnet, if I recall... --Fastfission 12:41, 2 August 2006 (UTC)


 * As stated in the article, it does indeed use RF energy. If you go to the NMRI article, and scroll down to the safety section, you can read all about the health concerns.  --198.125.178.207 13:35, 2 August 2006 (UTC)


 * 1) MRI's can generate sound pressure levels up to about 130 dB during certain scans. There is the potential for hearing loss at these levels, so earplugs (or muffs) are necessary to protect the patient / subject's hearing.
 * 2) MRI's do use RF energy. The energy can create focal heating, particularly on electrically conductive materials that can act as antennae. Make sure that there is space and / or padding between your body and the walls of the MRI and any wires used to monitor your vital signs during the exam. The RF energy is believed to be of no health concern.
 * 3) Magnetic energy (and RF energy, for that matter) is non-ionizing. This means that the cancer risks that are present in conventional X-ray imaging are not present in MRI imaging. The magnetic fields used in MRI, even though they are dramatically more powerful than most people would otherwise come into contact with, are not shown to have any adverse biological effects. The magnetic fields can interfere with implants and devices, so it's critical to provide your full medical history to the MRI provider.
 * 4) The primary risk in MRI is the magnetic attraction of ferromagnetic materials. These sorts of accidents make up the majority of injuries in the MRI environment. Focal heating is second. These accidents are largely avoidable and, despite recent dramatic increases in MRI accidents, are fortunately not terribly common.Tgilk (talk) 16:17, 14 December 2008 (UTC)

Speed of the Space Shuttle
Hi, Does anyone know what the speed of the space shuttle is from T-0 to SRB separation? I was watching the launch the other week and just got around to asking the question. Deltacom1515 02:03, 2 August 2006 (UTC)


 * Um, do you mean how long it takes, or what's the average speed over that interval, or the final speed...? Melchoir 03:01, 2 August 2006 (UTC)

Sorry 'bout that. I meant the acceleration of the Shuttle from 0 to SRB separation and the velocity is is traveling when it clears the tower. Deltacom1515 20:51, 2 August 2006 (UTC)

What is the difference between electrostatic and electromagnetic levitation and another question
What is the difference between electrostatic and electromagnetic levitation? i have heard that electrostatic levitation can also lift non-conductive materials. is this true? secondly could electromagnetic waves or electrostatic waves be used to push an object instead of levitate it? [ by directing the force at the side rather than the bottom for example] thanks curious marve


 * The diff is that magnetic repulsion lifts in the one case and electrical repulsion in the other. Yes, only certain materials, like metal alloys containing iron, may be magnetized, while all materials can hold an electrical charge.  And yes, either force could be used to fire a projectile, see coil gun, rail gun, linear accelerator, and cyclotron.  StuRat 03:59, 2 August 2006 (UTC)


 * I'm not sure exactly what you mean by electromagnetic levitation. It is true that only some materials can be magnetized, however by electromagnetic induction, any conductive material can have an induced magnetic moment in a changing magnetic field via electromagnetic induction.  Also see maxwell's equations for the classical physics behind the electromagnetic force.  And if you're curious about how electricity and magnetism are unified, you might be interested in special relativity.  --198.125.178.207 15:28, 2 August 2006 (UTC)


 * A copper bowl can be made to levitate by coils placed below it which produce an ac magnetic field. May be related to work by Faraday with a copper disc in a magnetic field, or by Tesla with a copper egg in a rotating magnetic field. I'm told the bwol heats up so the demo is usually for a few seconds. I've seen a demo with a magnet and liquid nitrogen in which the magnet levitates, or maybe a condictor levitates over the magnet. Maglev is used for some high speed trains. A charged object should levitate above a plane conductor with the same charge, if the magnetic repulsion is greater than the object's weight. It should similarly be lifted by a plane or point of the same charge above it, but this would tend to be unstable if the charges were constant. Edison 23:22, 3 August 2006 (UTC)

Thank you all, but can i crarify this please. So any material can be moved or levitated by elecrostatic fields, even stone,plastic or wood? Curiousmarve

U.V- Effect
Hello! Very recently, one of my friends was working in the Laminar-chamber, he was busy streaking... and accidentally, the UV was switched on. Engaged in his work, he didn't realise it for about a minute, ie. he withdrew his hands from the laminar after about a min. Later, he consulted a general physician, and a radiologist too. All the tests indicated that he had no internal or external damage whatsoever. I want to know was he too lucky? Or may be the intensity of UV was too low? Is a minute's duration enough, to cause damage to human tissues(keeping in mind, the UV used here) ? --Pupunwiki 02:52, 2 August 2006 (UTC)


 * What's a "Laminar-chamber"? You don't say what the wavelength and intensity were, so I'm thinking the dose was so low it was harmless. —Keenan Pepper 03:58, 2 August 2006 (UTC)


 * Oh, you must be talking about a laminar flow cabinet. Hold on and I'll give a better answer. —Keenan Pepper 04:28, 2 August 2006 (UTC)


 * A laminar flow cabinet is a type of biology safety cabinet for culture and/or for filtering potentially biohazards. Often they have UV sources for sterilisation purposes. Obviously UV exposure is not ideal, but i have seen quite a few scientists expose themselves to UV (usually in a electrophoresis gel transilluminator, which one might imagine to have higher UV intensity) for many minutes. Generally they suffer the equivalent of a bad sunburn on the exposed area. Of course, the long term effect of such an exposure on the skin and eyes is unknown, but there is no reason it should do any more damage than spending too long at the beach one summers day.
 * If your friend didn't even have superficial skin burns, then i expect the dose was low enough, the intensity was low enough and/or his skin tone was dark enough for no serious damage to be done. Or more likely a combination of all three. Either way, if the doctors have given him the all clear, it is most likely not something to worry about.  Rockpock e  t  04:38, 2 August 2006 (UTC)


 * Pretty much what I was going to say. Laminar flow cabinets use UVC (the shortest wavelength of UV and the most harmful) to kill germs, but one minute isn't long enough to do significant damage (unless you stare at it and it hurts your eyes). The reason for all the warnings is that if you make a habit of working with the UV on, the damage will build up over time and you'll get skin cancer. —Keenan Pepper 04:46, 2 August 2006 (UTC)
 * I have to say, I'm a bit skeptical. When the UV is switched on in one of these hoods, there is no doubt that it has been turned on. In every model that I've ever seen, the lighting switches are configured as "on/off/UV", where "on" is working lighting, "off" is no lighting, and UV is a brilliant radiant purple or blue. I can't imagine that anybody would be so engrossed in their work that they wouldn't notice such an abrupt change in lighting, or somebody making such a mistake in the first place. That being said, such exposure for less than a minute is unlikely to have any problems. – ClockworkSoul 16:35, 2 August 2006 (UTC)

Unknown scientist
I was linking more names in the Timeline of luminiferous aether, but I could not find who Tomascheck was. ("1924 - ... uses stars for his interferometer light source, getting the null result.") Anyone know his full name? Rmhermen 03:53, 2 August 2006 (UTC)


 * That would be Rudolf Tomaschek. Not a lot on him on the web. --Fastfission 04:22, 2 August 2006 (UTC)

erosion prediction
At current erosion rates, how long would it take for the present continents to erode to sea level if there were not any new land mass created from volcanic activity or any other process? The reason for this question is that I heard it said that it would take only 14 million years. If this is true, then how are there any fossils found dating back any further?


 * Just 14 million years is indeed an impressively short time span. And in the 80's erosion was considered the biggest threat to human food production (that place is now probably taken by climate change), although that is in part due to the wrong ploughing techniques.
 * Anyway, erosion is not just the removal of material - the material also gets deposited elsewehere. Also, it doesn't take all land above sea level to erode to below the present sea level. As more material gets deposited into the seas, sea levels will rise, speeding up the process. So the mountain tops will erode away, depositing their material on the lower ground, where most life resides. In time, this will get flooded, life will move further up, get covered in turn, etc, until it is all gone. And buried. In real life, apart from volcanic activity, there's also the rising (and falling) of landmasses. So many bones buried beneath the sea will eventually 'surface' (literally). Some have even made it to the highest peaks (sea shells on Mount Everest).
 * In short, erosion doesn't expose fossils. It buries them. DirkvdM 09:26, 2 August 2006 (UTC)


 * You ask " If this is true, then how are there any fossils found dating back any further?" That's an easy one, because there is volcanic activity and other processes. Personally, though, I doubt it can be true. Would Mount Everest erode to nothing in 14 million years? Let's see now, it is 8,850 m high. To go away in 14 million years it would have to erode 8850 / 14000000 m per year, which is about 0.6 mm per year. That's quite a lot for solid rock. Notinasnaid 09:36, 2 August 2006 (UTC)


 * That rate sounds believable to me. The missing element is that the mountains are being pushed up as fast or faster than they are being worn down, however. StuRat 06:31, 3 August 2006 (UTC)


 * This seems to be a creationist myth started in 1972, presented here along with such gems as the saber-toothed duck. It is debunked here. -- Avenue 09:50, 2 August 2006 (UTC)


 * Do fossils get buried by volcanic activity? Of course some will, but are they preserved for us to find? Sediments (from erosion) sound more probable to me. DirkvdM 10:36, 3 August 2006 (UTC)

Ok, I visited the suggested web pages. Thank you for the advise. However the web page said that 200 million years ago the mouth of the Miss. was as far back as Illinoise. My question has changed direction. How is it that Florida formed? If you receed all rivers back proportionately the same amount Florida becomes disconnected. Florida also has the St. John river, which is pretty large, that would split it. Florida seems to be to flat to be formed from plate uplift or volcanic activity. both of these actions make me think of mountains, Florida does not have any. I hope ya'll like to answer questions because I have a lot. Thank you for your patience.ĆÁḌ


 * I believe most of Florida, the Gulf coast, and central US were underwater at that time. I'm not sure if the water level was higher or the land lower or some combo of the two.  Do we have a map of this in Wikipedia ? StuRat 06:17, 5 August 2006 (UTC)


 * I geus nobody has a good answer?


 * Sure we do. Your assumption that erosion happens by itself is wrong.  At the same time some surfaces are being eroded, many others are being buried in sediment.  Surfaces so buried, and any fossils they contain, are completely protected from erosion. StuRat 06:30, 7 August 2006 (UTC)

MRI accident on House
In an episode of House ("Euphoria" part 1), Dr. House wants to find out whether it's safe to do an MRI on a patient with ferromagnetic bullet fragments in his head, so he goes down to the morgue, shoots a corpse with the same kind of gun, and puts the corpse in the MRI. The bullet fragments jump out of the corpse and destroy the MRI machine.

Two questions:


 * How large does a ferromagnetic object have to be to cause harm to the MRI machine or the patient? I mean, many breakfast cereals contain "reduced iron" which is basically iron filings. Is it safe to undergo MRI after eating a lot of Cheerios?
 * Why did Dr. House think it would work? He's a brilliant doctor, he speaks many languages and he knows random facts about everything... why is he so clueless about basic physics? Did the show's writers just make a mistake? —Keenan Pepper 04:25, 2 August 2006 (UTC)


 * Because he plays by his own rules. (I've never seen the show.) Melchoir 04:42, 2 August 2006 (UTC)


 * I would suggest the primary explanation is that it makes better tv to have him destroy a MRI after shooting a corpse to demonstrate the point, than explain the same thing in dry scientific language. And anyway, House isn't really that smart.  Rockpock e  t  04:49, 2 August 2006 (UTC)


 * Yes he is! --Dweller 13:24, 2 August 2006 (UTC)


 * an amazing number of ferromagnetic objects find their way into mri rooms... i think i want an x-ray Xcomradex 08:32, 2 August 2006 (UTC)

http://www.simplyphysics.com/flying_objects.html

http://www.ajronline.org/cgi/content/full/177/1/27


 * What about ear/eyebrow rings? I have a few. I wonder if they'd be torn from my flesh and fly around like shrapnel inside the machine? --Kurt Shaped Box 08:36, 2 August 2006 (UTC)


 * Yep, if you google 'mri accidents' you'll see there was a case where someones hairpin was dragged inside their head... Xcomradex 10:07, 2 August 2006 (UTC)


 * If you walk by an MRI machine with metal earrings you can feel them start to tug (or so said my girlfriend at the time), much less a bullet in a gun. My guess is that it made more sense for the writers to have eclectic Dr. House do something like that than it did to have him say, "Well, obviously the better way to test if a bullet is ferromagnetic (if we need to test this at all) is to, I don't know, just put it near a smaller magnet, or maybe even just very slowly introduce it into contact with the MRI machine?" Anyway... when you sign up for an MRI they make you answer a million questions about ways you might have accidentally got metal filing into your body (people who have worked in machine shops for a living are not allowed to take them because of the chance they might have a metal sliver in them somewhere that they don't know about), so I imagine it doesn't have to be too big of a piece. I am sure the iron content of your blood is not a problem though, X-Men 2 not withstanding. --Fastfission 12:47, 2 August 2006 (UTC)


 * I had to get my permanent retainer temporarily removed to have an MRI awhile ago, but oddly enough, the reason they gave is that it would ruin the image(distort the field around my head), not that it might rip my teeth out. Black Carrot 22:03, 2 August 2006 (UTC)


 * The retainer may have been made out of a metal that is not ferromagnetic, which would not pull your teeth out but could cause distortion. 48v 18:37, 4 August 2006 (UTC)


 * Based on my experience, people who have worked in machine shops are not prevented from having an MRI scan performed on them. Depending on the risk exposure, they may be x-rayed a few times to see if any fragments of metal are actually still in them (in the eyeball, in my case); and if none are found the MRI scan will proceed.  Anecdotally, I heard that one can hold something metal, like, say, a spoon up to the wall outside an MRI suite and it will be magnetically stuck to the wall.  Depends on the building, of course, and how close the MRI scanner is to a wall...


 * Didn't that whole episode turn out to be a hallucination? House might be allowed a little rhythm under those circumstances.... --Trovatore 04:02, 3 August 2006 (UTC)


 * No, that was a different episode. =P —Keenan Pepper 19:52, 4 August 2006 (UTC)

In answer to the House MRI question...
 * 1) How large does a ferromagnetic object need to be? A patient was blinded by a tiny sliver of ferromagnetic material in the eye some years back. An aneurysm clip of a couple centimeters twisted and tore, killing a patient, and a nail clipper put out an eye of yet another patient. So, depending on where it is, a very small mass of material can be very dangerous to a patient. Damage to the MRI machine typically requires something a bit more massive (i.e. chairs, gurneys, gas cylinders, etc...). However, MRI service personnel are sometimes called to take care of a machine that isn't producing quality images, a problem that is often triggered by a collection of small ferromagnetic materials (barrettes, jewelry, paperclips, etc...) that wind up getting collected inside the MRI machine.
 * 2) Would his corpse experiment work? NO, it wouldn't, at least not the way it was shown on TV. There are two forces that act on ferromagnetic materials in the presence of a magnetic field. One is torque where the object tries to line-up with the magnetic polarity of the field. The other is the translational (or 'missile') effect which draws ferromagnetic materials to the strongest part of the MRI field (in the center, where the patient lies). The torque forces keep getting larger and larger as you move to the center of the MRI. The 'missile' effect forces, however, are greatest near the entrance to the 'mouth' of the MRI and actually drop to zero where the patient would be for imaging.

So, when House put the corpse into the MRI and 'turned it on' and the bullet came flying out, there are a number of things wrong. First, there is no turning the MRI's magnetic field on and off for most systems. So, the attractive 'missile' effect would have been present and increasing as they brought the corpse towards the MRI, but would have dropped to zero once they had the corpse's head in the middle of the MRI. The torque, which would have wanted the bullet to align with the polar orientation of the MRI's magnetic field, would have grown and grown, but having the bullet simply twist wouldn't have been nearly as good 'TV drama' as having it blow through the skull and 'shoot' the MRI machine.

Now the recent ER episode of the patient being pinned to the MRI by the gurney that they were brought into the room on... that's another story... see http://mrimetaldetector.com/blog/?p=217 Tgilk (talk) 16:33, 14 December 2008 (UTC)

EM sound???
We know that EM waves dont comprise of sound.But if we were to hold the blades of a fan and turn it on,then from where do we here that noise?
 * The noise from a running fan is caused simply by vibration in the motor and the fan blades. -- AJR | Talk 12:30, 2 August 2006 (UTC)

How about when I put 5 amps through a nail-and-copper-coil solenoid I made in high school? That thing made some noise! — [  Mac Davis ] (talk)


 * If you stop a fan from going round, then the coils in the motor will be pulling on each other, or on the permanent magnets if there are any, with a force that's proportional to the current. Assuming the fan is mains-powered, then that current is alternating at 50 or 60 hertz (cycles per second). This makes the force pulsate at 100 or 120 hertz (because each cycle of current has two peaks, one positive and one negative). The pulsating force makes a buzzing noise because the parts of the fan are periodically distorted by the force. The same thing applies to the solenoid. The distortion is partly due to electrostriction magnetostriction and partly just to mechanical forces. --Heron 21:02, 2 August 2006 (UTC)

light speed
What if light were travelling in a striaght tunnel,and the tunnel happened to be the radii of a fast moving object.Since the end of the rod would be moving faster,would not that light be moving faster than light?


 * I'm not sure I really understand the question; but the answer is no.


 * Light moving faster than light, so something moving faster than itself? I suppose you mean a specific beam of light moving faster than 'the speed of light'. In other words, you're asking why there is such a thing as 'the speed of light', ie why light has a fixed speed. I could try an answer, but I'll leave that to someone more knowledgeable. I just tried to help you make your question clearer. DirkvdM 09:47, 2 August 2006 (UTC)


 * I'm not sure what the question means either, but you might find the article on frame of reference interesting, or special relativity, which is Einstein's answer to the dilemma which I think you are addressing.   --198.125.178.207 15:31, 2 August 2006 (UTC)


 * I'm going to guess that you are imagining a long tube being spun round and then light shone down the tube, and then you are imagining that the light would move at the sum of it's own velocity and the velocity of the tube it is shining down. The answer is still no, because a) relativistic effects would ensure that the light always moved at constant speed and b) if the tube were spinning at any noticable speed the light would hit the walls, not follow the changing path of the tube. Light doesn't change direction to follow the walls it is 'contained' in. DJ Clayworth 17:43, 2 August 2006 (UTC)
 * There are several different recorded light speeds. I just heard on NPR radio that scientist claim to have stopped light and held it in place for a few seconds.
 * The speed of light depends on the medium it's travelling in. Air reduces it by a percentage point or two, diamond by about 60%, and certain exotic materials by a great amount indeed. This doesn't affect the fact that the speed of light in vacuum is a constant, and the highest possible speed. --Pyroclastic 14:03, 10 August 2006 (UTC)

Quanta UNIVERSE
We know that the theory of everything comprises strings.So does that not make it possible only for integral values of particles or strings to exist,so therby only intergral values of force and other quantity to be transmitted and recieved?


 * Well, we don't 'know' that. String theory is just a theory (and one might argue it is not even that because it cannot be tested - it is not falsifiable). DirkvdM 09:51, 2 August 2006 (UTC)


 * Please don't say "just a theory." However string theory fulfills only half of the scientific method. The theoretical part, not the experimental. — [  Mac Davis ] (talk)


 * I will say whatever I please. :) You're right that something being 'just a theory' doesn't mean it doesn't have value (the general theory of relativity being one example). Everything starts off as a theory anyway. But my point was that you shouldnb't confuse theory with knowledge. Strictly speaking, we don't know anything and everything is theory. Which again boosts the status of theories, of course. DirkvdM 10:41, 3 August 2006 (UTC)

Electron
An charged particle under acceleration should emit radiation.Then why would not a charged particle undergoing acceleration around the nucleus of the atom or in the cyclotron emit radiation,as it is tracing a circular path and objects tracing a circular path undergo constant acceleration?


 * The image of electrons as orbiting nuclei in a similar way to planets orbiting stars is a simplification. See Quantum Mechanics.


 * Here is one explanation: . Weregerbil 08:54, 2 August 2006 (UTC)


 * Regarding a cyclotron, it seems it does actually emit as you expect (see cyclotron radiation and synchrotron radiation), because those actually do have particles orbitting. DMacks 20:37, 2 August 2006 (UTC)

CD-DVD burn
why cant we use a blank dvd to burn on a cd burner and blank cd to burn on dvd burner?
 * The grooves are too close together on a blank DVD for the CD burner to understand. Notinasnaid 10:26, 2 August 2006 (UTC)


 * But you can use blank CDs to burn on a DVD burner in most DVD burners. It will use the capacity of the CD.--Wikicheng 13:44, 2 August 2006 (UTC)

Pneumatic brakes
whats the advantage of air brakes over their hydraulic counterparts. i see that heavy trucks and trains tend to prefer air brakes over hydraulic,why?why not have these air brakes on passenger cars if they are that effective?


 * An obvious answer is that passenger cars aren't quite as heavy as trucks. The other part of the answer would then be that hydraulic brakes are in some ways more expensive (the brakes themselves, their operation, maintenance, whatever). DirkvdM 09:57, 2 August 2006 (UTC)


 * There is no advantage - the two types of brakes do different jobs. Air brakes are used only as a failsafe backup system. In an emergency, the air is vented to the outside to apply the brakes. This is simple and reliable, but too cumbersome and not controllable enough for normal braking. Trucks, like cars, use hydraulic brakes for normal braking, because hydraulic brakes are quicker, smaller, easier to control and more powerful. --Heron 20:53, 2 August 2006 (UTC)


 * Many heavy vehicles do use pneumatic brakes for normal braking&mdash;haven't you ever heard them at a stop light? In order to stop a heavy vehicle quickly you need to exert much more force than for a passenger car. One could design a hydraulic system with enough mechanical advantage to provide this force from a foot pedal, but then you would have much less control over braking. Air brakes are controled by a valve which feeds air from a reservoir to the pistons&mdash;giving much more control over the range of forces which can be applied. Air brakes are also more tolerant of leaks and water in the system.
 * Pneumatic brakes are not used in passenger vechicles because the are not necessay, are more expensive and bulky, and require more maintenance.EricR 02:10, 3 August 2006 (UTC)


 * Well, what do you know, a subject I know next to nothing about and my answer was spot-on. Long live educated guesses. :) DirkvdM 10:45, 3 August 2006 (UTC)

Be careful not to confuse either with engine braking. StuRat 06:21, 3 August 2006 (UTC)

catastrophe and the internet
In the event of a major catastrophe, that sent mankind back centuries or approached (near-)existinction levels, could the internet data (such as the information from wikipedia) theoretically be retrieved then at a much later date? (such as the case of the Rosetta Stone being "translated" in the 19th Century) Also, could theoretically the internet be received or "read" by other distant civilizations? (as in the way that extraterrestial communication/signals are hoped for possibly through radio waves I think) Thanks for info. ==Joel==


 * Something similar was asked before here at the ref desk. Apart from that, the rosetta stone wasn't translated, it was itself a translation, helping with other translations. And if humans were almost extinct, the information on the Internet would not survive (it needs electricity). So the info would have to be stored in a different way. DirkvdM 10:10, 2 August 2006 (UTC)


 * The information does not need active electricity in order to survive as just data on a million computers. There is a lot of worried discussion among computer scientists about how long current data storage mediums last — not too long. The Rosetta Stone, being carved in a rock, is much more durable than magnetic storage media, much less affected by the elements, much easier to use if part of it became damaged. Still, I imagine the sheer volume of data which goes into the internet means that quite a bit could be recovered even if nobody was tending to it for a few centuries. I imagine that many servers are in places that would be relatively protected from the elements (such as those buried deep within large facilities).
 * As for the second questions, the only way that the internet would be read by someone off of Earth is whether it is broadcast (like television or radio). I don't know enough about tramission protocols, but I do think that some internet connectivity is done via satellite? If that's true then those connections may be potentially interceptable, decrypted, etc., I suppose (I don't imagine WiFi signals to be strong enough to make it that far, but I know little about this sort of thing). Let's hope that the people with connections like that don't just use it to surf for porn. ;-) --Fastfission 12:59, 2 August 2006 (UTC)
 * I've read a description of a wished-for radio telescope talked of by a radio astronomer: You take a star as your lens and sit back where the stuff you're interested in is focused by the gravity. The radio astronomer described it as potentially able to hear a walkie talkie (hand held radio) being used on a planet 10 light years distant. The latancy would suck though.


 * In my opinion, if it were some space beings coming to Earth long after humans were gone, it wouldn't be by chance. They would be attracted by the radio and television waves shooting out into space.  Surely, they would decipher it before arriving on Earth and will have prejudged humans based on what they've seen and heard - pretty much how humans prejudge other cultures based on mass media. Youth in Asia 15:01, 2 August 2006 (UTC)


 * The beauty of the Internet is that it is designed to work over just about anything - TCP/IP consists of many ayers and you just need to adjust the bottom layer (I think). And it does work over anything. I one route doesn't work, another one is used. So I suppose that everyone will at least once in a while receive some data that have gone through satellites. DirkvdM 10:50, 3 August 2006 (UTC)

Thanks to all above for the info., Joel

how do we know if its been tried?
hi my names ben, ive been thinking about this perpetual motion thing a bit, since i noticed what seems like a working example, i dont expect to hold the key, but im curious to see other failed attempts based on this illusion of free energy. is there a list i can go through? because regardless of weather or not it does create free energy, i think it may still be useful. i think we'll figure it out one day, we'll follow a trail that will lead us to the very beginning, and there we'll find the supernatural, proof of thats not hard to find, also seems someone have allready nailed it,i like the way joal thinks, out side the box,i consider the physical universe as we know it a box.theres alot more if if you know how to open your eyes. search psychic witnesses, and ufo evidence. thanks heaps for any help Beno


 * You want us to check if something you will not describe has been tried before? Thanks for the confidence, but we're not gods. :) DirkvdM 10:13, 2 August 2006 (UTC)


 * You may well find something that is supposed to work the way your idea is supposed to work listed under Perpetual motion. See also Laws of thermodynamics --Polysylabic Pseudonym 11:49, 2 August 2006 (UTC)


 * There's "a lot more" out there than "psychic witnesses" and "ufo evidence", indeed. But the latter two strike me as not very interesting, frankly: examples of a human willingness to believe, age-old desires to know that someone is in control, somewhere -- a hope that there is still mystery in the world. But there's much more mystery in the natural world than there are in dreams of the supernatural. How much more interesting the mantis shrimp is than the "greys" that the UFO nuts like to talk about! How much more bizarre the human mind is, with its strange wiring and odd sense of the world, than ramblings of New Age "psychics"! Oh, if only we could really appreciate how fascinating and bizarre the natural world is, we wouldn't have to take refuge in the relative banality of fantasies, which only reflect the limits of the human imagination! --Fastfission 13:06, 2 August 2006 (UTC)
 * Well said. --198.125.178.207 15:35, 2 August 2006 (UTC)
 * Very well said. I'm keeping that. — [  Mac Davis ] (talk)


 * Truth is indeed, in many ways, stranger than fiction. Sadly, though, the curious appearance of a shrimp doesn't help me make things levitate. Black Carrot 21:51, 2 August 2006 (UTC)

I wouldn't view an apparently successful perpetual motion machine as proof of the supernatural, but rather as evidence of a natural, although currently unknown, form of energy. Radio wave energy, for example, was unknown for most of human existence StuRat 06:08, 3 August 2006 (UTC)


 * You can fill in pretty much what you like for 'radio wave energy' because most of what we know now was unknown for most of human existence. DirkvdM 18:52, 3 August 2006 (UTC)


 * Yep, that was just one among many possible examples. StuRat 20:57, 3 August 2006 (UTC)

When you talk about tings supernatural you are only talking about things observed that we can not yet understand. Things such as religion. There is ample amounts of imformation to support the thought of intelligent desighn. One day ,if man ever does find a way to understand these things in a way that would go further than religion, these things will be facts & not religion. Something that is truth from the begining is not less true simply because we do not understand. If nothing else, Science has taught us that. So, indeed there is an answer to prpetual motion and energy.ĆÁĎ

Consumption
I was looking for disseases/afflictios that greatly eat up/damage the inside of the body. Necrosis and consumption, but i'm looking for other, and perferabbly stronger examples.
 * Consumption doesn't eat up the body any more than many other diseases (see tuberculosis), though it was once thought so. The classic diseasse that eats up the inside of the body is cancer. For nasty and well known diseases try leprosy and ebola. Notinasnaid 11:38, 2 August 2006 (UTC)

As well as 'eating up' the inside, im looking for things that make them go black-like when you see those anti-smoking adds, and they show you those black lungs.
 * That doesn't 'eat up' the lungs either, nor is it a disease, and anyway, working in a coalmine (or living next to a highway) is much more effective in blackening your lungs. DirkvdM 10:53, 3 August 2006 (UTC)


 * Necrotizing fasciitis is a pretty good example for a disease that quickly "eats up" the flesh (hence the nickname of its cause, "flesh-eating bacteria"), but this isn't the inside of the body, its the deeper layers of skin and subcutaneous tissues (fascia). – ClockworkSoul 16:23, 2 August 2006 (UTC)
 * Hemotoxic venoms do, and Phosphorus certainly would, although I don't know if you could call it an affliction.--Anchoress 19:17, 2 August 2006 (UTC)

These are all very good, and thanks to all the contriubtors. What woudl be great though are things that are very astheticaly profound, like more with an urg factor.
 * Did you read the article on ebola? Hollywood has embraced it because it considers (perhaps wrongly) that it has more urg factor than any other condition in history. Notinasnaid 12:28, 3 August 2006 (UTC)

sexual thought freqency
Is there a real study on the freqency of sexual thoughts in men and women? All I find is contradictory and annecdotal.


 * It's nonsense. See this article on Snopes.--Shantavira 15:01, 2 August 2006 (UTC)


 * I saw an article once (I forget where) about an interesting experiment which tackles (one element of) this question. They kitted out subjects with special spectacles which recorded where they were directing their attention. If I remember correctly, it was found that the average woman does look at the "interesting bits" of men, but proportionately less than men do for women.
 * I don't the experiment analysing gay men and women's behaviour.
 * Clearly, looking at bums is just one aspect of sexual thought, but it was a usefully revealing methodology, even if the specs themselves weren't all that revealing. --Dweller 15:04, 2 August 2006 (UTC)


 * Hmmm, I think about sex about 95% of the time, but I'm more likely to look at a guy's car than his goodies. That having been said, '"frequency of sexual thoughts" study' turned up some interesting google hits.--Anchoress 20:21, 2 August 2006 (UTC)
 * So it's true then? Girls don't like boys; girls like cars and money? --Trovatore 20:30, 2 August 2006 (UTC)


 * Well I sure like boys, but I'd rather look at a car.--Anchoress 21:01, 2 August 2006 (UTC)

I've never understood the concept of "sexual thought frequency". To think about it repeatedly, wouldn't you actually have to stop thinking about sex at some point ? Who can do that ? :-) StuRat 04:07, 9 August 2006 (UTC)

Geologic time scale terminology: Paleo- vs Eo-
In the Archean eon, why does the Eoarchean era precede the Paleoarchean era, when in the Paleogene period (early Cenozoic) the Paleocene epoch precedes the Eocene epoch? (Yes, I realize that the Precambrian time divisions were only recently established and assigning names to them is somewhat arbitrary; but even so, why would the International Commission on Stratigraphy have chosen to go along with a usage of prefixes which is inconsistent with the already long-established Cenozoic sequence of epochs? Were they catering to previous publications, or lazy geologists, or what?)  Lots of searching on this seemingly trivial point has revealed absolutely nothing, which makes it all the more annoying (to me, anyway). --DWIII 15:08, 2 August 2006 (UTC)

Megawatt_hour
How to compute the cumulative power output (in MWh) of a power plant generating 100MW?


 * 100MW is the power. MWh is used to measure energy, not power. Youth in Asia 16:30, 2 August 2006 (UTC)

Sorry, I mean cumulative energy (at least for a day).


 * Just multiply. 24h * 100MW = 2400MWh.  --Allen 16:57, 2 August 2006 (UTC)


 * What do you mean by 'at least for a day'? In case you're confused, the unit Wh is confusing and converting from power to energy is sort of 'the wrong way around'. One watt is one joule per second. So the Wh first divides by one unit of time (the second) and then multiplies by another (the hour). 100 MW means 100 MJ/s (one Joule of energy every second). There are 60x60x24 = 86400 seconds in one day, so the power plant produces 86400 Joule (or 86.4 GJ) per day. Which is equal to 2400 MWh, but that is not an SI unit (because of the 'hour' in it), so preferably use J. DirkvdM 11:03, 3 August 2006 (UTC)

Invisibility
This is awesome http://www.royalsoc.ac.uk/exhibit.asp?id=4659&tip=1. It is real right?


 * I think the picture is fake. The plausible types of 'invisibility' I've come across either require you to look through a specific viewpoint (and so would be handy to make your car look transparent from the rear view mirror) or only work at specific wavelengths, currently very small, meaning they could cloak against some detection systems, but not the human eye. I'm trying to work out which this is, or if it's new. Skittle 17:44, 2 August 2006 (UTC)
 * Mmmm...yeah, the hand picture looks fake to me. The article is kind of vague about what exactly the research finding or engineering breakthrough is.  It sounds kind of like they're talking about a metamaterial, but it's hard to say.  And the appications they talk about don't make any sense, at least under that interpretation.  If they've invented a specialized material that is invisible, how would that help you look through earthquake rubble?  Or see through a hand?  In any case, materials that are invisible (i.e. allow visible light to pass through them) are nothing new!!  See glass and water and diamond, etc, etc.  I really don't know what this article is talking about.  But i'm also confused, because I thought the Royal Society was a reputable organization... someone want to clarify, or confirm, or explain why this is legitimate after all?  --198.125.178.207 18:08, 2 August 2006 (UTC)


 * The alt text for the hand image says "This is what you'd see if the system worked with the atoms in your hand". It doesn't work with the atoms in your hand, so the picture is a fake. There's a slightly less dumbed-down version of the story at hero.ac.uk. --Heron 20:39, 2 August 2006 (UTC)


 * Ah. That makes much more sense.  The other article did a good job making it sound like a crackpot fraud.  None of that silly "seeing through earthquate rubble" stuff.  --198.125.178.207 21:10, 2 August 2006 (UTC)

It did sound awesome though, thanks.


 * The picture isn't supposed to be a picture of the experiment (it is still all hypothesized anyway), just as a nice looking thing that goes with the article. If you want to learn more, what the articles talk about are nanotechnology's quantum dots used as artificial atoms. — [   Mac Davis ] (talk)

Possible to reduce ozone levels indoors?
I'm finding that my throat is inflamed and it's just a bit harder to breath lately -- and I think it may be due to elevated Ozone levels in the area. (I read about this effect here.) My question is: is there a way to reduce the amount of ozone in my house? -Quasipalm 18:29, 2 August 2006 (UTC)


 * Turn off any ionic air filters, as they are a primary cause. StuRat 05:55, 3 August 2006 (UTC)

I should also point out that there are other, far more likely causes, such as dry air, mold spores in the air, dust mites, pet dander, chemicals (like formaldehyde) released from new furniture, carpets, paint, and cleaning compounds, etc. StuRat 05:58, 3 August 2006 (UTC)


 * Candles are supposed to produce ozone and I thought that was a good thing, or is that just new age mumbo jumbo? DirkvdM 11:08, 3 August 2006 (UTC)


 * Ozone indoors (and outdoors, at ground level) is generally a bad thing, although it can kill bacteria and viruses in the air. As for candles, I'd be more concerned with the soot they produce than any small amounts of ozone. StuRat 21:01, 3 August 2006 (UTC)


 * You haven't been breathing in air out of your microwave after you put lots of metal in it have you? That might be the cause. It could be inhalation of bug zapper fumes. — [  Mac Davis ] (talk)

unit question about article : List of countries by electricity consumption
Hello,

I am quite interested in the total number of Watts countries around the world use for industry/civilian purposes/others...

But : List of countries by electricity consumption gives consumption in numbers of kWh, and consumption per capita in kWh as well. Call me crazy, but I thought people use Watts/kilowatts, and they use kilowatthours during a day or year or whatever. So in short : what is up with the units? Are they for a full year or what?

Thanks,

Evilbu 19:05, 2 August 2006 (UTC)


 * The unit "kilowatt hour" is a unit of energy - it is the amount of energy transferred in one hour by one thousand watts (a watt is a unit of power). The list you cited is describing how much electrical energy each country consumes in a year.  I agree that it is confusing - the article should say that the time period is one year (i'm fairly sure it is).
 * I'm not sure what you would use "watts/kilowatts" - for. The per-capita figure is simply the total figure divided by the population of the country.  If you want to know the power usage, you can find the average power usage of the country by dividing by the number of hours in a year (8760); then you will have the average power consumption of the country in kilowatts.  --198.125.178.207 19:19, 2 August 2006 (UTC)


 * I think it can be assumed that the figures are kWh/year, since there's a column in the table that states which year the figure is for. I added "/year" anyway, just to make it clearer. --Heron 20:30, 2 August 2006 (UTC)

Thanks, I discussed this with my dad (he works with industrial energy) and he agreed there is almost no doubt they mean :per year. But I wanted to check with you.

Now forgive my insolence, but I like to think in Watts (megawatts) too. For instance the power generated by windmills is given in megawatts. So... wouldn't it be nice to have a separate column converting it to Watt too? I mean, it would also be nice to compare then with I am willing to take care of that conversion. Evilbu 22:23, 2 August 2006 (UTC)


 * It's generally assumed that readers will be able to convert between units. Otherwise we'd have to include horsepower, ergs/second, etc. Composite units like kWh/year actually make sense, because giving consumption in watts would give a false impression of continuous consumption when actually electricity consumption is highly diurnal and seasonal. 1 kWh/yr = 0.114 W. EdC 03:35, 3 August 2006 (UTC)
 * Though, Orders_of_magnitude_%28power%29 has it wrong: it's taken kWh/y figures as W. EdC 03:41, 3 August 2006 (UTC)


 * Wow, that is even more important. Are you saying that the Orders of magnitude article uses Watt as unit while the numbers are incorrect?? Evilbu 11:25, 3 August 2006 (UTC)


 * That would indeed be a rather serious error., Especially if it isn't done consistently. What makes you say that?
 * Btw, Watt and Megawatt aren't different units. It's the same unit with an SI prefix. 'Mega' means million, so 1 MW is 1,000,000 W, The conversion is so easy it doesn't need to be given, but then of course you do need to know about prefixes, but you should learn that pretty soon at school. However, kWh/yr doesn't make sense because it mixes up three units of time: second, hour and year. I keepon trying to add this info to Watt-hour, but it keeps on being removed because it wouldn't be interresting info. I think this discussion disproves that.
 * If you're from the US it may take some getting used to that there is just one unit per quantity in the SI system, but ultimately it's a much easier (because simpler) system. DirkvdM 13:04, 3 August 2006 (UTC)
 * I fixed the error mentioned above in orders of magnitude (power). They were just a power of 1000 off :)  --Bmk 13:24, 3 August 2006 (UTC)

Snakes
Is the saying about venomous snakes, "red next to yellow, bite a fellow, red next to black, friend of Jack," true? 69.40.240.98 19:40, 2 August 2006 (UTC)


 * See coral snake. Youth in Asia 19:42, 2 August 2006 (UTC)
 * Also see milk snake. The saying is correct. --Ginkgo100 talk · contribs · e@ 20:13, 2 August 2006 (UTC)
 * To clarify: it is correct regarding coral and milk snakes, not poisonous snakes in general. – ClockworkSoul 20:34, 2 August 2006 (UTC)
 * Yes, thanks ... also, it should say "red on yellow, kill a fellow," as a milk snake can certainly bite. Its bite is not venomous, but it could be painful. --Ginkgo100 talk · contribs · e@ 03:26, 3 August 2006 (UTC)
 * Yeah, I meant to say "kill a fellow". Thanks. 69.40.240.55 04:31, 3 August 2006 (UTC)


 * I always thought the "friend of Jack" part was a really lousy rhyme in comparison to the "kill a fellow" part. Jack? Jack who? In any case, this little rule does take the fun out of movies when one can easily see that a "deadly snake" is a relatively harmless milk snake. --Fastfission 05:00, 3 August 2006 (UTC)
 * I agree. When I heard 'friend of Jack', I thought 'friend of the devil', either meaning the snake was really bad or that the person who came in contact with the snake would be dispatched to the afterlife. Combined with the 'bite a fellow' mistype, I thought the rhyme was backwards.--Anchoress 06:11, 3 August 2006 (UTC)


 * Ask Jack. DirkvdM 13:12, 3 August 2006 (UTC)
 * Don't ask me, I've never heard that rhyme before, and I know next to nothing about snakes (which is very surprising, given that I am the Devil incarnate). :--) JackofOz 03:22, 4 August 2006 (UTC)
 * On the other hand, I'm not above biting a fellow or two, given half a chance. You have been warned.  JackofOz 03:23, 4 August 2006 (UTC)

Alcohol Gel and Salt
While playing around with some alcohol gel, I sprinkled some common table salt into it, and found that it causes the gel to seperate into a thinner liquid (just the alcohol and alcohol soluable substances?) and a whitish, flaky solid. Has anyone else see this phenomenon? What causes it? Any ideas? Brian Schlosser42 20:50, 2 August 2006 (UTC)


 * Common ion effect?--G N Frykman 22:26, 2 August 2006 (UTC)


 * Having just read common ion effect, it doesn't really explain how the addition of a substance containing one ion (which is present both substances) causes the solubility product of one to be exceeded. Salting out is another phrase for it.  G N Frykman 22:31, 2 August 2006 (UTC)


 * Might be interesting to read the ingredients of the alcohol gel to see what ions or other dissolved solids might be present. DMacks 22:57, 2 August 2006 (UTC)
 * Here are the ingredients from the Purell website- Active: Ethyl Alcohol Inactive: water, isopropyl alcohol, glycerin, carbomer, fragrance, aminomethyl propanol, propylene glycol, isopropyl myristate, and tocopheryl acetate. Brian Schlosser42 12:17, 3 August 2006 (UTC)


 * I don't have an answer, but intuitively, it doesn't seem illogical that the salt could de-emulsify the substance, causing the liquid to separate from the gelling agent.--Anchoress 06:09, 3 August 2006 (UTC)

Molecular orbitals and symmetry
I was going to ask this question about benzene, but then it occurred to me that acetylene is a simpler molecule with the same basic problem. Acetylene has two pairs of electrons in two perpendicular pi bonds, but its electrostatic potential map has full cylindrical ($$D_{\infty h}$$) symmetry. How is this possible if neither of the pi orbitals has cylindrical symmetry? —Keenan Pepper 21:05, 2 August 2006 (UTC)


 * Now I'm curious to know the answer too. Also, the second paragraph of acetylene says, "As the molecule cannot twist around the triple bond, all four atoms lie in the same straight line, with bond angles of 180°."  Now, the first part of that sentence makes sense with the two pi bonds, and would go agaist the cylindrical symmetry.  But the second part of that sentence seems to be a non-sequitur.  The bond angles would be 180 degrees either way, right?  --Allen 22:32, 2 August 2006 (UTC)

"Not twisting around a pi bond" is how we normally explain the existence of cis and trans isomers in substituted ethenes to our pupils. The phrase is meaningless with ethyne - twisting of this linear molecule would mean bending, and I am sure that there is an IR absorption for triple bonds doing this! The cylindrical symmetry in ethyne (lengthwise) implies indistinguishable overlap between the two perpendicular pi bonds.--G N Frykman 22:48, 2 August 2006 (UTC)


 * The "twisting" phrase is a bit odd for a triple bond. There presumably is no twisting in the olefin sense (rotation of the orbitals on one atom in a way that breaks and then reforms a different π system), but that would have no effect on the geometry. I'd be interested to see an electrostatic map that includes orbital information and is cylindrical. For most purposes, treating the triple bond as a "fat bond", a cylinder of π cloud, gives good enough results. DMacks 23:11, 2 August 2006 (UTC)


 * There is a fundamentally simpler answer to this question. Recall that the px, py, and pz orbitals are actually probability maps for where electrons will be in space at a given time.  Combined, all three p orbitals map to a perfect sphere.  The usual drawings of the orbitals are actually drawings of the area in space in which there is a 60% probability that an electron occupying the orbital will reside at a given instant in time.  There is, however, a 40% probability that one or more electrons will be outside of this area at a given instant.  Thus, in acetylene, the py and pz orbitals that hybridize to form the pi bonds seem to be asymmetric when drawn, but this is because you are only considering 60% of the probability density for each electron.  If you instead consider the volume of space for which there is a probability density that one or more of the four pi electrons will reside at any given instant, you will actually see a perfectly symmetric tube surrounding the x-axis of the molecule.  Hence, if there is a lower probability that a py electron will reside in a specific area, this is compensated by the fact that there is a higher probability that a pz electron will be in this area.  As such, it is correct to say that acetylene has $$D_{\infty h}$$ symmetry.


 * As for rotation around pi-bonds, there is actually some computational evidence to suggest that it requires less energy to rotate around a triple bond than a double bond. While this may seem counter-intuitive because two pi bonds must be broken to rotate around a triple bond (versus one for a double bond), it actually makes sense because the overlapping p orbitals must only rotate 45 degrees out of phase before they come into phase with a new set of p orbitals and begin to re-form a pair of pi bonds.  Since energy varies non-linearly as the orbitals come out of phase, the net energy barrier to rotation around a triple bond is lower than around a double bond.  However, since the four atoms in the triple bond lie along a single axis (this is due to electron repulsion, NOT molecular orbitals: electrostatic repulsion leads to molecular geometry which, in turn, leads to the mathematical construct of molecular orbitals - probability densities determined by specific molecular conditions unique to each molecular environment), this cannot be tested experimentally and is therefore basically irrelevant.  -- C. S. Joiner (talk) 01:02, 10 August 2006 (UTC)

Brushing your teeth
Everyone in the know seems to recommend brushing your teeth for 2.5 minutes, twice or three times a day. But what I wonder is, after the first 30 seconds or so, what is being cleaned off my teeth? And is it better to brush my teeth twice a day for 2.5 minutes, or five times a day for a minute?--Anchoress 21:41, 2 August 2006 (UTC)


 * My Sonicare manual says that you should brush for two minutes. As for what is cleaned off, it is probably like scrubbing a wall.  If you scrub for too long, you will through the paint and into the drywall.  I don't think it is a matter of how many times you brush.  It is when.  You do not want food - especially sugar - sitting on your teeth.  So, brushing every time you eat and then not drinking sugar-water between meals will not only help your teeth but also help your breath. --Kainaw (talk) 23:09, 2 August 2006 (UTC)


 * Its really something that is more qualitative than quantitative: How well you brush, not how long. — [  Mac Davis ] (talk)
 * But brushing straight after you eat can cause slight erosion of the enamel on your teeth, which can build up over time if you do it regularly. So wait a while after eating. Or brush before eating to remove the plaque so there's nothing for the sugar to stick to. Sugar doesn't just stick to enamel. At least, that's what I was taught. Skittle 12:49, 3 August 2006 (UTC)


 * I thought that brushing after or before eating was a bad idea, which is why just before going to bed is the best time to brush. Also, it depends on the food. Sugar rots your teeth, so you should avoid eating that, and especially around brushing time. Acids are also bad. One of the worst combinations is yoghurt with sugar. Or cola, which also contains loads of acid and sugar. When I was a kid I drank loads of cola (almost a litre per day!) and almost all my fillings are from around that time. I got accustomed to getting new filings every time I went to the dentist. From my twenties that stopped and until a few years ago (I'm now in my fourties) I almost never had any problems at the dentist. Also, when I was a teenager I brushed my teeth more often than later on in life, so that should give the previous explanation extra credibility, unless brushing your teeth (the way I did it?) is actually bad for your teeth. DirkvdM 13:22, 3 August 2006 (UTC)


 * My Sonicare says to spend 2 seconds on each tooth, on the front surface and then the rear. Given the standard human allotment of 32 teeth, that's 128 seconds.  --LarryMac 14:59, 3 August 2006 (UTC)


 * I don't know what 'my first sony-care' is, but does it do one tooth at a time. My toothbrush is several teeth wide. Still, I spend more than 2 minutes brushing my teeth, but I do it only once a day - the quality vs quantity thing that MacDavis mentioned, just a different interpretation of the principle. :) DirkvdM 19:13, 3 August 2006 (UTC)
 * Ah yes, if only there were some type of online reference source where one might look up words he considered unfamiliar.  --LarryMac 14:21, 4 August 2006 (UTC)
 * Ah, it's sonic air! DirkvdM 18:48, 4 August 2006 (UTC)

Having been to the dentist this morning, I'm in a good position to chime in here! Apparently, the number 1 cause of adult tooth loss in the UK is not tooth decay, but gum disease. The time spent brushing your teeth (and, as importantly, flossing), is to improve the health of your gums; preventing your otherwise healthy, decay-free teeth from falling out! --Dweller 14:10, 4 August 2006 (UTC)

Considering my background, perhaps I should say something as well. Though there may be some technical result found in research saying that it is harmful to brush after eating, in reality this is not seen as a problem. Brushing your teeth after you eat is generally not seen as causing detectable levels of damage. However, how you brush is important, and not necessarily how often. If you brush 26 times a day but not in a manner to remove all the plaque, then those 26 times really do no good. Since the point of brushing is to remove all the plaque, you probably will not remove all the plaque off a tooth on your first stroke--- which is why you will have to spend some time on it. And a bit unrelated, sugar helps form tooth decay, but the frequency of your sugar intake is more important than the amount. So, eating a bag of candy in 30 minutes will be less harmful for you teeth than eating the same bag of candy slowly throughout the day. - Dozenist talk  23:05, 8 August 2006 (UTC)

Valium + Alcohol = ?
I'm currently taking valium, prescribed by my doctor (5mg, every 3 hours). Is it safe to drink *any* alcohol at all? What happens when you mix the two? Is it a case of just getting drunk quicker or could it kill me?


 * Valium + Alcohol = Death. They are both depressants. Its best to stay away, the combination of the effects can cause your heart to stop if the right amounts are taken. Don't be stupid. pschemp | talk 22:20, 2 August 2006 (UTC)


 * a) I agree with pschemp; they're both nervous system depressants. b) talk to your doctor or pharmacist. This is definitely near the top as far as questions that should not be settled on the advice of anonymous posters.--Anchoress 22:24, 2 August 2006 (UTC)


 * I think it was answered quite well here, by saying they should NEVER be taken together. You can't go wrong by taking that advice. StuRat 05:50, 3 August 2006 (UTC)


 * It's always a good idea to not be stupid. That should, however, not be confused with ignorant. If there is any danger in combining valium with alcohol, there should be a warning on the valium bottle (or whatever that comes in). If there isn't then that would be stupid (and if you're in the US you might think of sueing them). DirkvdM 13:25, 3 August 2006 (UTC)


 * There is a warning: "Drunk, pregnant children operating heavy machinery while driving should not take this product". Or something like that. :-) StuRat 21:09, 3 August 2006 (UTC)

Value and alchohol can make your brain work like its never worked before. that can either kill you or make you a super human. you choose the red pill and your free.

What mushroom is this?
Hey, I have this mushroom growing in my front yard and I was wondeirng what type it is. Thanks for any help, Newnam(talk) 23:29, 2 August 2006 (UTC)
 * I dunno, but don't eat it no matter what anyone here says! :)  ok, now more knowledgeable people can take over and identify it.  --18.239.5.61 02:09, 3 August 2006 (UTC)


 * It looks like a portobello, I think. Black Carrot 03:38, 3 August 2006 (UTC)


 * Or it could be a death cap which will kill you in about the nastiest way there is. Weregerbil 06:00, 3 August 2006 (UTC)


 * It doesn't look the least bit like the death cap. Are you just trying to scare people? DirkvdM 13:30, 3 August 2006 (UTC)
 * Nor does it look like a portobello mushroom. Are you trying to poison people? :) DirkvdM 14:17, 3 August 2006 (UTC)
 * It looks at least somewhat like these death caps. --Lambiam Talk 20:08, 3 August 2006 (UTC)
 * It looks a lot like the death caps I see in the forests where I go mushrooming (and they are not portobellos as those are rare in this climate). All white, pronounced collar, and a sock (is that what it is called in English). Given the deadly nastiness of death caps I certainly don't mind scaring people away from all white mushrooms that can't be positively identified. Like for all mushrooms: I love picking and eating them, but not enough to die for a meal. Weregerbil 20:44, 3 August 2006 (UTC)

Yeah. You can see from the protruding spots on top that it's almost certainly a death cap, and absolutely not a portobello. Do not eat this, if you were considering it. If you have a mouse problem, cut it up, soak the pieces in milk, and wait a couple days. All the mice in your house will die fairly quickly, because the milk attracts them. Sashafklein 22:40, 3 August 2006 (UTC)


 * Thanks for all the imput. I certainly will not eat it. I was just wondering, as this mushroom was by itself, and the first I ever noticed in my yard. Thanks again, Newnam(talk) 03:43, 4 August 2006 (UTC)

Might be a destroying angel too, or some other similar Amanita species. If the photo was a bit sharper it'd make the identification easier, as would seeing the gills and, most important, knowing where the photo was taken. I could be wrong, of course — I'm certainly no mushroom expert — but something about the general shape does scream Amanita to me, at least enough that I'd leave the thing well enough alone. —Ilmari Karonen (talk) 23:51, 10 August 2006 (UTC)