Wikipedia:Reference desk/Archives/Science/2008 August 21

= August 21 =

Herbal infusion
Can I make a herbal infusion from the cannabis plant leaves.?
 * Cannabis (drug). --JWSchmidt (talk) 03:08, 21 August 2008 (UTC)


 * Do you want to know a) if it is legal, b) if it is technically possible, c) if it is a good idea to do so, or d) other? Wanderer57 (talk) 03:25, 21 August 2008 (UTC)


 * Note the key point from the above article. Because THC is lipophilic, it's not a particularly effective way if you want to get stoned... That's why people tend to make cannabis cookies, cakes and food items containing a fair amount of fat. You could try perhaps some sort of cannabis Cendol or other dessert or drink with a liquid base containing a fair amount of fat if you really prefer it in drink form (never tried it myself but it seems plausible). Nil Einne (talk) 11:42, 21 August 2008 (UTC)


 * However, if you use one of those recipes for Tibetan butter tea that can be found on the net, your lipophilic troubles are eliminated. Butter tea needs getting used to, though. --Ayacop (talk) 16:07, 21 August 2008 (UTC)


 * Science! It like totally does stuff, you know dude? Oh man! SamuelRiv (talk) 00:51, 22 August 2008 (UTC)


 * Bhang Lassi. DuncanHill (talk) 08:56, 22 August 2008 (UTC)

eye damage from hand dryers
Hi, I read just now on a hand dryer in a public toilet, that if you blow the hot air in your face, there is a risk of eye damage, from something called "fusion." What is the story here? 134.115.68.21 (talk) 08:36, 21 August 2008 (UTC)
 * I don't know the specifics, but it seems blindingly (pun unintended) obvious that if your eyes get too hot, there's a strong risk of damage and given the low level of pain receptors in the eye, you may not even realise Nil Einne (talk) 11:46, 21 August 2008 (UTC)


 * Unless the dryer was made by the Fleischmann & Pons Corporation, I'd say they're referring to the danger of a plastic contact lens fusing to the eye because of the heat; ouch! --Sean 16:54, 21 August 2008 (UTC)


 * It might not even be the heat. Could it be that the drier would normally dry the liquid from the surface of your eye - but you'd blink and tear up a bit - and no harm is done.  But one of those soft contact lenses that's permeable to water would dry out without you noticing and form a water-tight seal against the eye - with no way for liquid to get back inside and rehydrate it?  That's a guess though. SteveBaker (talk) 17:42, 21 August 2008 (UTC)

Astronomy Question: Need a Repeating Celestial Event
I'm looking for an astronomical/celestial event for a story I'm writing. Thus far, I haven't been able to find anything that exactly fits what I'm looking for. My conditions are this: the event has to repeat every 200 to 300 years. It has to be visible from the same location on Earth. Also, I'd rather not go with a comet if I can help it. Can anyone give me some suggestions, or a pointer in the right direction? Thanks. --Brasswatchman (talk) 08:45, 21 August 2008 (UTC)
 * The Transit of Venus occur in a pattern that repeats every 243 years, with pairs of transits eight years apart separated by long gaps of 121.5 years and 105.5 years. Of course the sun has to be up for one to see it, but as half of the transits currently occur in june, there are populated places with midnight sun that could have viewed it regardless. In any case, the article has a table of the timings. EverGreg (talk) 10:16, 21 August 2008 (UTC)


 * And if you did choose the transit of Venus (which I think is an excellent choice, personally), you'd have a rich set of historical anecdotes to draw on and even some interesting scientific controversies (the "black drop effect" has been a major issue regarding the transit of venus, and there is ample historical material out there about international attempts to resolve it in the 19th century, etc.). In 1874 it was referred to as the "astronomical event of the century". --98.217.8.46 (talk) 12:18, 21 August 2008 (UTC)
 * As with a solar eclipse, observing a transit of Venus is fraught with risk of serious eye damage. Whether this might affect your story, I don't know. Wanderer57 (talk) 12:24, 21 August 2008 (UTC)


 * The trouble with events that widely separated is that the previous occurrance would have been back in the 1700's when telescopes were still pretty primitive devices. So you're really needing a more or less "naked eye" event.  Comets really are your best chance.  If this is fictional - then a meteor shower might do what you need.  Events like the Perseids happen annually as the Earth passes through a stream of debris that was originally a comet that broke up a very long time ago.  That debris stretched out so far that pretty much the entire orbit of the original comet has debris within it.   But if the comet had been one that repeated every 300 years and if it had only broken up relatively recently (on the scale of cosmic events) then there might well be a bunch of debris that only intersects the Earths orbit every 200 to 300 years.

I don't know of any such events in reality...but fictionally, I don't see a problem with inventing one. Anyway - a meteor shower (especially from a relatively recently broken up comet) could be as spectacular as you need it to be. Anything from chunks of rock and ice hurtling out of the sky smashing buildings and splattering our Hero's one true love over half a county...down to a bunch of gentle shooting stars that commemorate that tragic event and bring our Hero's great, great, great, great grandson together with the (sadly splattered) heroines' great, great, great, great granddaughter together. Anyway - it would occur on the exact same night of the year - although not generally at the exact same time of the night.


 * Oh - and if you need the last occurance to have happened before 1753 - beware of calendar reform! Actually, this would make a great plot point!  Suppose the original sighting of the event happened on September 1st 1752, with a prediction that it would happen again precisely 250 years later on Sept 1st 2002.  Our modern day heroes might initially be unaware of the fact that 11 days were 'dropped' from the calendar in 1752 (so the day after September 2nd 1752 was September 14th 1752!!).  They would gather with the bad guys holding guns to their heads (or whatever) at the appointed place on September 1st 2002 - and be horrified to find that the specified event doesn't happen as predicted.

We're confused, they are confused, the bad guys go away - could the prediction really not be true? Then, just a week and a half later when hero and heroine are strolling in some romantic place believing that the prediction was a lot of nonsense - he proposes to her and at that exact moment the sky bursts forth with meteor trails (because it's September 12th) - which is actually 250 years later to the day exactly on schedule. A wandering Wikipedian strolls past and comments "Hey didn't you read Calendar reform?".


 * This stuff practically writes itself!


 * Good luck with your book! SteveBaker (talk) 13:21, 21 August 2008 (UTC)


 * And here I thought Steve was going to mention the change of New Year's Day, which in England took place about the same time, so that one year after March 24, 1750, it was March 24, 1752. --Anonymous, 21:39 UTC, August 21, 2008 (N.S.).


 * The trail of debris left by a comet will cause a meteor shower every year, but you can get more dramatic ones in certain years due to particular passes of the comet leaving clumps in specific places. It might be plausible to have a extra dramatic shower once every 250 years, or whatever. I think a transit of Venus is a better choice, though - it's almost tailor made for the OP's requirements. --Tango (talk) 17:55, 21 August 2008 (UTC)
 * Yes - certainly the Perseids have good years and bad years - suggesting a certain clumpiness. But it kinda surprises me that the debris spread so far through the original orbit of the comet.  It seems that the debris was created about a thousand years ago and came from the 109P/Swift-Tuttle comet.  For the purposes of a story, the comet could have broken up much more recently - leaving the debris in a relatively compact bunch that would orbit with roughly the same period as the comet - which could easily be 200 to 300 years.  That would also produce an event with a fairly sharp onset and cutoff if most of the debris were still fairly close together. SteveBaker (talk) 00:17, 22 August 2008 (UTC)


 * Does it have to be set on Earth? How about a planet orbiting a flare star? (eg. a star like Groombridge 1618) Astronaut (talk) 18:30, 21 August 2008 (UTC)


 * Brasswatchman: Can we consider this question resolved, or would you prefer to keep it open? --Bowlhover (talk) 09:24, 23 August 2008 (UTC)

"Green Bags"
There's an ad on TV for "Debbie Meyer's Green Bags", which promise to almost stop fruits and veggies from rotting. The claim is that they remove ethylene gas produced by food which would otherwise cause spoilage. They also say the bags can be reused up to 10 times. I'd like to know if these claims are legit:

1) Do all fruits and veggies produce ethylene gas ?

2) Does this gas promote spoilage ? If so, to what degree ?  The commercial makes it look like there is no spoilage once this gas is removed.

3) Do the bags remove 100% of the gas, or only a tiny portion ?

4) Could they really be reused 10 times without losing their effectiveness ?

5) Are there other side effects, like stopping fruit from ripening ? I prefer yellow bananas over brown, but brown is still better than green.

6) I'd also be interested in seeing a cost/benefit analysis. That is, does the cost of the bags outweigh the financial benefit of avoiding lost produce ?

7) Is there a more efficient way of removing ethylene than disposable bags ? StuRat (talk) 12:37, 21 August 2008 (UTC)

Update: I found these reviews, which are mixed to negative:. However, I'd still like to know more about the science that's going on with the bags, so still would like answers to the Q's above. StuRat (talk) 12:50, 21 August 2008 (UTC)


 * Ethylene as a plant hormone may be of interest, and this site has an interesting sensitivity chart. Moving into the questions:
 * Most, certainly. "All" is a difficult blanket statement.
 * Promote, absolutely. Sole factor, generally no.  Per the sensitivity chart, reaction to ethylene varies.
 * Who knows?
 * It probably depends on how long you're keeping fruit in the bag on each of the 10 times. I'm betting on an over-optimistic marketing pitch, but that's just me.
 * Yes, rotting and ripening are both effects of ethylene.
 * Depends on you personally. How much produce are you losing without the bags?  How much produce would you lose if you just bought produce on an on-demand (or nearly so) basis?  It's unlikely you save anything if you're buying and storing produce responsibly to begin with.
 * Good ventilation is the easiest means of reducing ethylene quantities. Segregating ethylene producers from ethylene-sensitive produce is another useful approach.  There are other methods, but they seem to be targeted at the industrial level. &mdash; Lomn 12:56, 21 August 2008 (UTC)


 * As for question #4, if they do in fact work, I wonder if telling you they can only be used for 10 times is just a ploy to get you to buy more. Just a thought; there may be a chemical in the lining of the bag that reduces ethylene that runs out after so many uses, and of course you don't want to reuse a bag for food too many times, but still, I wonder.--El aprendelenguas (talk) 20:10, 21 August 2008 (UTC)


 * I've found this more science-based set of reviews. The reviews are mixed, but it is clear that the bag is more effective with some products than others.  It's also clear that leaving produce in a cool, open place is a better way to prevent spoilage.
 * To add some original research of my own, ethylene has about the same density as air and, for that reason, escapes very easily with minimal air circulation.  Trapping the ethylene in a plastic bag is not the best way to promote circulation.  --Bowlhover (talk) 10:24, 24 August 2008 (UTC)

The Large Hadron Collider and the Sun
Is the sole purpose of the large hadron collider to try to create black holes by accelerating hadrons to high speed and then crashing them into each other, or are there other experiments as well?

Is it likely that there are hadrons of comparable energy inside the sun? To put the question another way, is it likely that micro black holes are being created within the sun? If so, would this be a common event or a rare one? Thanks, Wanderer57 (talk) 16:04, 21 August 2008 (UTC)


 * Producing black holes is not a primary goal or purpose of the LHC at all. The only reason you hear about the LHC and black holes is that some cranks filed a lawsuit, because they thought it would cause the end of the world.  See Large_Hadron_Collider for its major goals.  If you had to pick one goal, it would probably be the discovery of the Higgs boson.  -- Coneslayer (talk) 16:13, 21 August 2008 (UTC)
 * It's interesting to note that we really do have machines which are reasonably likely to end the world at some point, but these folks didn't see fit to try to sue them out of existence. It's like fretting about spontaneous human combustion when there's a snake in the room.  --Sean 16:46, 21 August 2008 (UTC)
 * Well, it sort of is apples and oranges from a legal point of view. --98.217.8.46 (talk) 19:52, 21 August 2008 (UTC)


 * The energy in each collision of individual nuclei in the LHC will be around 10-4 joules. A rough calculation shows that this is equivalent to a temperature of around 1019 K. The temperature at the centre of the Sun is only around 107 K. So LHC collisions will be much much more energetic that reactions within the Sun. Gandalf61 (talk) 16:19, 21 August 2008 (UTC)


 * For comparison, see Orders_of_magnitude_(temperature). --Ayacop (talk) 16:31, 21 August 2008 (UTC)


 * If your question was really "do such high energy particles/collisions occur naturally and have we seen any disastrous effects elsewhere?" the answer is yes for the particles and no for the disastrous effects, see Ultra-high-energy cosmic ray. Well if someone would be hit directly that would not be healthy, but neither the end of the world nor the end of our planet. 93.132.168.99 (talk) 16:54, 21 August 2008 (UTC)


 * Well, not quite. The idea that a cosmic ray could produce whatever weird/dangerous particles the LHC might produce is valid - but if it were that easy, we wouldn't need the LHC!  The problem is that any particles appearing from a cosmic ray collision would continue to move at spectacular speed and probably go right through the earth and out the other side without anyone noticing.  Even if you were hit by a mini-black hole coming about from a cosmic ray event, it would drill a hole through your body that would be considerably smaller than the diameter of an atom...you wouldn't notice.   But if the LHC were to produce such an object, it could be stationary - or moving very slowly...so (the theory says) it could be a real problem.   I think that's nonsense - but that was the thesis put forth in the law suite.


 * Anyway - the purpose of LHC is to "discover stuff" - and you don't always know what you're going to discover until after you've discovered it. It's hoped that there may be further evidence for dark matter - perhaps some of the predictions of string theory may be tested...and there is a lot of confidence that the Higgs Boson may be discovered.  The Higgs is predicted to be a very heavy particle and because of E=mc2 it takes more energy to make particles with more mass.  Since the energy comes from slamming particles together, the energy comes from the kinetic energy of the particle that's doing the hitting.  The giant circular tunnel accelerates particles to higher speeds than we've ever been able to do before.


 * SteveBaker (talk) 17:18, 21 August 2008 (UTC)


 * (ec with SteveBaker, somewhat redundant now) The purpose of the LHC is to see what there is to see in that energy regime. Theoretical particle physics has failed spectacularly at making predictions in the last 30 years, so nobody really knows what to expect. Almost everyone thinks it will see the Higgs boson, since the Standard Model limits its mass to a range that's easily accessible to the LHC. It's not really the main goal of the LHC to find the Higgs boson, it's just the one thing most physicists agree it will succeed in doing. Some people expect to also see black holes, some expect to see superpartners, some expect to see other exotic particles (about which I know nothing). Some people think the Higgs won't be found. Nobody wants the Higgs to be found; it would be much more interesting if it wasn't. The worst-case scenario for the LHC is finding a fundamental scalar Higgs particle and nothing else, giving theorists almost no clues about physics beyond the Standard Model. That could very well mean the end of particle physics.


 * I don't know much about conditions inside the Sun, but collisions at the energy the LHC will produce happen all the time. The only reason they need the LHC is to make them happen at a predictable place and time, so that they can stick a huge honkin' detector there and analyze the result. The proposed ILC would produce lower energy collisions than the LHC but under even better controlled conditions. -- BenRG (talk) 17:22, 21 August 2008 (UTC)

Apparently Natural Causes?
Could we please have medical input to the discussion here:

Talk:Jack the Ripper

Thanks, Wanderer57 (talk) 17:05, 21 August 2008 (UTC)


 * The standards of medicine in the 1880's were kinda poor so it's perfectly possible that nobody really checked for precise cause of death.
 * She died many months before the ripper murders became notorious - so there was no particular reason to pay careful attention to investigate and record cause of death - a lazy doctor could just have scribbled "Natural causes" in order to avoid a lot of hassle.
 * She died sometime AFTER she'd been discharged from hospital - over a month after she'd been stabbed - it seems unlikely that she was seriously injured at the time she died.
 * If she'd gotten some kind of general infection, it's perfectly possible that they would not have connected her death to injuries from the wounds - and perhaps a death from a serious infection would have been impossible to diagnose at the time.
 * It's unusual for someone who is only 38 years old to die of "natural causes" in this day and age - but even as late as 1900, life expectancies for urban poor were hovering around 45 years. So it's quite possible for the report to be 100% true.


 * I don't doubt that was the report of the time - but it's hard to know whether the report was accurate or not.
 * SteveBaker (talk) 17:34, 21 August 2008 (UTC)


 * Who she was and what she did for a living could also have prejudiced a doctor into not putting a lot of effort into her diagnoses. It's well known that cases of "undesirables" dying are often given far less attention by authorities, who are not looking to make more work for themselves if nobody cares or notices if they brush things under the rug. Just a speculation. --98.217.8.46 (talk) 19:42, 21 August 2008 (UTC)

Liquids going from perspiration to waste in humans
This may be a rather simple answer - at the point it reaches the kidneys, perhaps - but the womens' Olympic marathon brought to mind a query I'd had from a number of years ago. I'd consumed two bottles of water walking in 95 degree F heat for a couple hours,a nd hardly had to use the bathroom at all; it had all been sweated out.

My question is, at what point does water consumed go from being utilized as sweat to being discarded as waste? My guess from both articles would be that anytime before it reaches eht kidneys, it's game for being sweat, but afterward, it's automatically urine, but I'm not sure; it almost seems like if you've really gotta go, and yet you're running a lot, it can still wind up used as sweat even if it's in the bladder. Is the answer true for other liquids, too? Or, only with respect to the amount of water in them? (Weird, the thing to sign wasn't illuminated before. Now it is.) Somebody or his brother (talk) 19:03, 21 August 2008 (UTC)
 * The kidney is the irreversible/committing step where water goes to urine. Once it diffuses out of the blood and is not re-absorbed in the collecting ducts, there's no further chance for it to go anywhere else except ureter→bladder→urethra→outside. DMacks (talk) 19:09, 21 August 2008 (UTC)
 * Water also goes out through the digestive system but it can be recovered from the colon when needed. Franamax (talk) 22:37, 21 August 2008 (UTC)

what is important of material sciences?
—Preceding unsigned comment added by 116.71.61.200 (talk) 18:56, 21 August 2008 (UTC)
 * Not really a coherent question here. But did you read the material science article? Think about how important it is that someone made the stuff your keyboard and monitor are made out of. DMacks (talk) 18:59, 21 August 2008 (UTC)
 * Studying it gives me something to do outside of Wikipedia. the wub "?!"  23:17, 21 August 2008 (UTC)

Telephone call to 911
Let's say that a person is incapacitated, cannot speak, and has absolutely no idea where they are (as a result of an accident or a crime or for whatever reason). The only thing the person can manage to do is to dial "911" on a telephone. Scenario A: If that person dials 911 from a landline phone, my understanding is that the 911 dispatchers can tell immediately what the location of the landline phone is. And, if the incapacitated person does not speak (after having made the 911 call), they will still dispatch help to the correct address. Is all of that correct? Scenario B: Now, what exactly happens if the 911 call was made from a cell phone? Does anyone know how exactly this works? I assume -- at some point -- and through technology -- they can somehow locate the cell phone and the person. Now, will this take a few minutes, hours, days, weeks, what? In other words ... in an emergency, how long would that incapacitated person expect to wait before help arrived, when summoning 911 from a cell phone? Also, are there procedures (similar to the landline phone) where they dispatch help no matter what, even if the incapacitated person on the cell phone does not / cannot speak? Thanks. (Joseph A. Spadaro (talk) 19:49, 21 August 2008 (UTC))


 * You should probably start with Enhanced 911. -- Coneslayer (talk) 19:52, 21 August 2008 (UTC)


 * The FCC's page on wireless 911 may also be of interest. &mdash; Lomn 19:53, 21 August 2008 (UTC)


 * I am fairly sure that 1. is correct at least in some locations. I have friends who dialed 911 and then hung up after a second or two and the cops did indeed show up their door. (It's a long story. It involved LSD. It worked out fine in the end. Just in case you're wondering.) As for a cell phone, hypothetically you can locate which cell tower the call came from (which puts you within a mile or so), and maybe even triangulate it based on information from multiple towers, I suppose, but emergency dispatchers do not currently have that capability as far as I know. If you don't tell them where you are, they don't know. Eventually I am sure this will change. --98.217.8.46 (talk) 20:05, 21 August 2008 (UTC)
 * As long as the phone is still turned on, you can track it more accurately. I'm not sure of the details, and I'm not sure if it's routinely used, but it can be done. --Tango (talk) 20:14, 21 August 2008 (UTC)
 * One thing the dispatchers get is the phone number, so that they can all back to see if the call was an accident, or a prank, or genuine. There is also a special number for tty machines if the user has such a facility. Graeme Bartlett (talk) 21:35, 21 August 2008 (UTC)


 * In many jurisdictions, if you don't talk to the 911 operator and simply hang up, the first thing they do is try to call you back at the same number. Also, if you have the misfortunate of living in my jurisdiction, you can call 911 and listen to a ridciulous "All operators are busy, please stay on the line" message for 10 minutes.  This happened to me when trying to report a car crash.  I can imagine that such delays have probably resulted in a least a few deaths from people that might otherwise have been saved.  Dragons flight (talk) 01:00, 22 August 2008 (UTC)


 * The dispatch depends on the Emergency Medical Dispatcher protocols used by the authority having jurisdiction. In my county, this type of call goes out as an "unknown rescue;" fire, EMS and police respond together. Also see 9-1-1. --Shaggorama (talk) 03:28, 22 August 2008 (UTC)

Thanks. So, if the incapacitated person is on a cell phone and can't speak or offer any location clues ... how long would they have to wait for help to arrive? Minutes, hours, days, weeks? Thanks. (Joseph A. Spadaro (talk) 11:07, 22 August 2008 (UTC))


 * Depends where they are. Are they in a car accident on a major highway? Probably get found pretty quick. Are they hidden in somebody's basement? Might never get found. --98.217.8.46 (talk) 13:52, 22 August 2008 (UTC)


 * This hypothetical incapacitated person is just in a house, which he does not know the address of.   (Joseph A. Spadaro (talk) 15:25, 22 August 2008 (UTC))


 * I dispatch for an ambulance company on Long Island and, along with the calls that we receive from MEDCOM, we also get a print out. The paper, along with the complaint of the caller, has the phone number call came from, the name of who the phone is registered to, and approximate longitude and latitude of where the call came from, if it came from a cell phone. If someone calls 911 and immediately hangs up, the 911 operator calls the number back with a message saying that in order to receive help, they need to call 911 again and give an address. -- MacAddct &#xF8FF; 1984 (talk &#149; contribs) 18:50, 22 August 2008 (UTC)

Thanks for the input. Much appreciated. (Joseph A. Spadaro (talk) 03:57, 23 August 2008 (UTC))

Is that right? i heard reports that in the UK, if you dial 999 from a mobile you don't necessarily get put through to the right district (unlike if you rang from a landline). I.e. if you say you've been left for dead on George Street it's quite possible that an ambulance will show up in Edinburgh rather than London. Presumably if you didn't say anything the problem would be ten times worse. (i've also heard that this problem is solved if you dial 112 (the pan-european number) which doesn't quite seem right -have i been lied to?) 82.22.4.63 (talk) 20:25, 28 August 2008 (UTC)

Solutions and volume changes
In a typical solution of a crystal solid in a liquid e.g. salt in water, is there a change in the volume of the solvent as the crystal dissolves? - is any change the same as or proportional to the volume of solute? —Preceding unsigned comment added by Webb202 (talk • contribs) 20:34, 21 August 2008 (UTC)
 * I'm pretty sure there is a change in volume, but I can't confirm if that change is equal to the amount of solute added. Coolotter88 (talk) 20:47, 21 August 2008 (UTC)


 * This is certainly interesting. Would the break down of the salt crystals to ions cause the salt to occupy less volume? I think the answer is yes but it would be very insignificant change.--155.144.40.31 (talk) 00:58, 22 August 2008 (UTC)
 * Some materials have a very large volume difference when dissolving ("volume of solute A + volume of solvent B >> volume of solution of A in B"). It has to do with the dissolved particles (ions or solvated molecules) fitting into the existing spaces in the solvent rather than completely displacing solvent molecules. Doesn't even matter if the solute is a solid or not (alcohol+water is an easy experiment to do at home). DMacks (talk) 02:42, 22 August 2008 (UTC)
 * The concept you are looking for is called partial molar volume. --Heron (talk) 15:43, 22 August 2008 (UTC)
 * Ah yes. My engineering friends talk about volume of mixing, but we didn't have a page on that term. DMacks (talk) 16:50, 22 August 2008 (UTC)

Thanks for the info -Webb202 —Preceding unsigned comment added by Webb202 (talk • contribs) 13:24, 24 August 2008 (UTC)

Optical zoom
Does optical zoom refer to distances or area? If I have a *4 zoom and take a picture of a square "zoomed out" and it is 100*100 pixels, when "zoomed in" by *4 will it be 400*400 or 200*200? -- SGBailey (talk) 21:19, 21 August 2008 (UTC)


 * It's linear, so 400*400. It's the ratio of the focal lengths at the longest and shortest zoom positions.  -- Coneslayer (talk) 22:40, 21 August 2008 (UTC)


 * It's linear if you're focused at infinity, but (if I've worked it out correctly) the width of the visible area of the focal plane in general is dw(1/f − 1/d), where d is the distance from the lens to the focal plane, w is the width of the detector (CCD), and f is the focal length. That would imply that the magnification is somewhat more than 4× if you're focused in close. However experimentation with my point-and-shoot digicam has failed to back this up, so maybe I made a mistake. -- BenRG (talk) 00:20, 22 August 2008 (UTC)


 * Many photographic lenses have an effective focal length that changes as you focus closer, especially if they have floating elements for zooming or to reduce aberrations at close-focus distances; see, for example, the charts here. This property could confound your measurements.  -- Coneslayer (talk) 14:42, 22 August 2008 (UTC)


 * Ta -- sgb

For Chemistry Experts
What would result from the following?; If Methane (Ch4) is present in water (H2O) and Hydrogen Peroxide (H2O2) is introduced.Rukiddin (talk) 23:20, 21 August 2008 (UTC)
 * A solution of two gases in water. Need some activation energy to make something fun happen. In terms of organic mechanisms at least, you'd need to get the radicals going (H2O2 is often a difficult-to-start radical initiator unless there's something very reactive available to do something) and methyl radical is one of the least stable (hardest to form) ones:( DMacks (talk) 23:27, 21 August 2008 (UTC)