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Adjusting Depth Of Feild On Regular Digital Camera

Is it possible to achieve depth of field effects (where parts are out of focus) without an SLR? They're just too big and inconvenient, not to mention expensive. Are there any digital cameras with a single lens that will allow me to control depth of field by varing the position of the lens? -Username132 (talk) 14:18, 12 June 2006 (UTC)

It's nasty with the smaller digital cameras, but at least you can try lots of times, and delete the losers. Almost all of these cameras lock their focus and aperature on a 'half click', you then move the camera to the subject and do a full press. For reduced depth of field you need dimmer light so the camera opens up more. You could lock the camera in a shadow, and then take a picture in brighter light, but then you would have to do some post-processing on the computer. --Zeizmic 15:06, 12 June 2006 (UTC)

In other words, it's a function of aperture size; the larger the aperture the greater the depth of field effect, which means that this effect is better with a larger lens such as those found on SLRs.--Shantavira 15:21, 12 June 2006 (UTC)

Any camera which allows you to set the aperture size will be able to vary the Depth of field. However, the smaller size of the imaging device may limit what is possible. Assuming one has a camera with the capability, then taking a series of pictures of the same subject, varying the F stop in each one, should reveal the capabilities of that particular camera. --LarryMac 15:44, 12 June 2006 (UTC)

The perceived effect also depends a lot on the focus distance: the easiest way to get nice blurry backgrouds with a compact is simply to switch to macro mode and get real close to the target. That way you maximize the ratio of background and foreground distance.

Also, digicams can do absurdly short exposures. In the fully automatic mode ("P" or "auto") the camera may try to balance the aperture and the exposure time, but if you want you can switch to aperture priority mode ("A") and shoot at the maximum aperture (i.e. smallest f number) in pretty much any lighting just fine. —Ilmari Karonen (talk) 15:53, 12 June 2006 (UTC)

Simply, to reduce field of focus: use maximum aperture - if that is what you can set; or: use fastest speed - if that is what you can set. The latter forces the camera to open the lens as much as possible. The technique you describe of "moving the lens" I presume to mean "zooming" i.e. altering the focal lenght of the lens system. If that is your only option, then using the maximum "zoom in" for an object a fixed distance from you will reduce the depth of field. --Seejyb 22:01, 12 June 2006 (UTC)

Zooming in might be counterproductive, though. My digital camera, for example, has an aperture range of f/2.6 to f/8.0 when zoomed all the way out, but only f/5.6 to f/8.0 when zoomed all the way in. --Serie 00:11, 13 June 2006 (UTC)

Also, many digital cameras won't focus very close, even in macro mode, unless zoomed all the way out. That, combined with the aperture range issue, means it's often better to zoom out and get close to the subject than to zoom in and shoot from further away. Of course, that only works if the subject is a) inanimate, b) slow, or c) tame. —Ilmari Karonen (talk) 11:50, 13 June 2006 (UTC)

It's very, very hard to get significant depth of field effects in compact digital cameras, even if they have manual aperture controls (and some of the better models do). As our depth of field article explains, the depth of field is larger with a smaller film (or sensor). Compact digitals have tiny sensors compared to digital SLRs, let alone 35mm film. Maybe you could buy a second-hand film SLR for the purpose if you are specifically setting out to take advantage of this effect? --Robert Merkel

Adding onto what has already been said, if you can't directly change your aperture or shutter speed settings, your camera may have a "Portrait" mode or similar mode where the camera attempts to limit the depth of field. Your camera manual should explain more on this.--Tachikoma 04:22, 13 June 2006 (UTC)

See here, basically get as close to your subject as possible, use as long focal length as possible and use the largest aperature. Can be done, but much easier with a SLR. Stefan 09:19, 13 June 2006 (UTC)

Question

There is a compact camera on ebay with Focal Length 7.7-23.1mm f/2.8-4.9 (35mm film equivalent: 37-111mm) - looking at the depth of field article, I will have a depth of field limited to only close up subjects. Look at the example photos my f/ numbers are restricted between 2.8-4.9 which means I can take the second daffodil picture and the cat picture only. I clearly have misunderstood. Explain how, please?

What can I acheive with; • F2.8 / F3.2 / F3.5 / F4.0 / F4.5 / F5.0 / F5.6 / F6.3 / F7.1 / F8.0 (wide) • F4.1 / 4.5 / 5.0 /5.6 / F6.3 / F7.1 / F8.0 (tele) ? --Username132 (talk) 23:46, 13 June 2006 (UTC)

• Going for a compact camera will not allow you to achieve much when it comes to Depth of field. If you really want to be able to go artistic but don't want an slr, there are many cameras out there with an APS Size sensor many manual controls (thats what you want) and good lens quality without interchangeable lenses. I leave you with a quote from the wiki to explain

...this means that smaller cameras have deeper depth of field than larger cameras. This can be an advantage or disadvantage, depending on the desired effect. A large format camera is better for photographs where the foreground and background are blurred (cf. bokeh), while a small camera maximizes depth of field, so that objects behind or in front of the focus plane are still in good focus. This difference between formats goes away if the cameras are compared with equal aperture diameters rather than equal f-numbers; but the smaller camera can not usually use a large aperture diameter, so can not achieve a very limited depth of field.

--DennyCrane Talk 05:13, 14 June 2006 (UTC)

Are you saying that f/2.8 on one camera isn't the same as f/2.8 on another? --Username132 (talk) 23:41, 14 June 2006 (UTC)

f/2.8 is always f/2.8, but 50mm is not always 50mm (sortof) or rather it is BUT to get the same field of view on a camera with a smaller sensor you need a lens with shorter focal length. So compact digital cameras can have a lens from 7.7-23.1mm (as above) wich is equivalent of 37-111mm for a full frame 35mm film camera, and f/2.8 at 7.7mm will have much more depth of field than at 37mm. Stefan 15:31, 16 June 2006 (UTC)

One option, for if you are trying to intentionally de-emphasize something, is to blur it out afterwards using an editing package on your computer. This is more work, but gives you more flexibility to de-emphasize things at various depths. StuRat 16:45, 21 June 2006 (UTC)

Measuring mass

How would you measure (not calculate using the density) the mass of an object in 0g?Yanwen 00:58, 14 June 2006 (UTC)

Apply a known force, and measure the acceleration. EdC 01:35, 14 June 2006 (UTC)

Attach it to a spring and then let it oscillate. See last equation in this section. I think that's how they do it in space. WP 03:40, 14 June 2006 (UTC)

But those are a pain to calibrate

Centrifuge it at a known speed, perhaps? 205.132.76.4 16:14, 16 June 2006 (UTC)

Your question is somewhat ambiguous:

• If, by the expression in 0g, you mean 'a place where the gravitational force is exactly 0', then there is no such place anywhere in the known, observable universe, and the question is somewhat hypothetical.

• If, on the other hand, you mean to designate a place 'inside an artificial satellite', such as the Space Shuttle, then be warned that this expression constitutes an abuse of language as the actual gravitational force is not nul: the satellite and the object whose mass you want to measure, inside this satellite, both fall towards the Earth with the same acceleration. So there is no apparent acceleration associated with the fall of the object, when measured with respect to the satellite walls, but that's not to say there is no gravity.

I don't think a single coil spring would work very accurately. However, attaching the mass between two springs arranged linearly like this:

||=/\/\/\/\/\=(object)=/\/\/\/\/\=||

where = stands for a fixed link, || represents the satellite walls (or some structure fixed with respect to the satellite walls), and /\/\/\/\/\ is a spring of know constant, would provide a suitable simple experimental setup. If the object is then displaced some small amount along the linear axis, measuring its position as a function of time would allow you to retrieve the mass, knowing the properties of the springs, the initial conditions and the time evolution of the system. --Michel M Verstraete 21:30, 19 June 2006 (UTC)

Fibre Optics

What is the difference between FOBOT and Patch Panel?

Tilt in the Earth's axis

Is there a "physics" explanation to the fact that the earth's axis is tilted?

Yvan Dufour

Why is not addressed, but you may be interested in Axial tilt. -- Rick Block (talk) 04:48, 14 June 2006 (UTC)

MadSci network has answered to similar questions here and here. –Mysid^(t) 07:29, 14 June 2006 (UTC)

The angle of the Earth's axis to its plane of orbit may in part be due to the hypothetical impact with Theia 4.5 billion years ago, resulting in the formation of the Moon (see Moon, Giant impact hypothesis, and History of Earth#Moon for more information). — Knowledge Seeker দ 04:46, 15 June 2006 (UTC)

Flying Saucer

I remember hearing somewhere that people were researching a type of craft that spun rapidly lifting it into the air. My question is has anyone ever heard of this or am I just crazy? If you have heard of it is there any kind of link you could give me to further my quest?

See Military flying saucers, but don't discount the possibility that you could, indeed, be crazy.  freshofftheufoΓΛĿЌ  05:31, 14 June 2006 (UTC)

I definately remember hearing about this, and progress having been made recently on a non-military version. I can have a look for details. Skittle 08:57, 14 June 2006 (UTC)

See also British Rail flying saucer. —Ilmari Karonen (talk) 17:47, 14 June 2006 (UTC)

See also Frisbee. SamSim 10:50, 16 June 2006 (UTC)

Thank You

One factor to consider is that the rotational speeds required would make for too high of g-forces on people. This could be handled with either an unmanned vehicle or a vehicle with a stationary center portion. The stationary central portion would make for a very complex design with lots of moving parts, so doesn't sound particularly feasible to me, unless you reduce the rotating portion to a few small blades and put them on top, then you have a helicopter ! StuRat 12:41, 21 June 2006 (UTC)

Bacteria ...

Hi!Mysid & zafiroblue05, thanks for the answers on dna. I have doubts regarding the answers of the following questions on bacteriology :

1. Do both Thermoplasma & Mycoplasma lack a CELL-WALL?
2. How can a thermophilic bacterium be isolated & collected from a running hot-water spring ?
3. In a broth culture, why does Staphylococcus sp. grows

throughout the whole medium, while Pseudomonas sp. grows as a thin film at the broth surface ? - Pupun.

1. All bacteria have peptidoglycan cell walls.
2. Get a water sample, spread-plate, incubate at high temperature.
3. Staph is gram-positive and Pseudomonas is gram-negative? But I truly have no idea.

-- Миборовский 05:51, 14 June 2006 (UTC)

1. Thermoplasma and Mycoplasma both lack cell walls. "L-forms" (which have no cell walls) of other bacteria which usually have cell walls, can be induced by various culture media and antibiotics.
2. Dunno, but you should look at the literature to see what media have been used. As Miborovsky points out, temperture will be key.
3. Dunno, but Pseudomonas is noted for its motility characteristics, including swimming, swarming, and twitching, which result in its tendency to form films. It might also have something to do with oxygen tension at the surface vs. the rest of the medium. - Nunh-huh 06:18, 14 June 2006 (UTC)

For question 1 & 2: I know that one D Lovely, a researcher at the University of Massachusetts, has done extensive research in thermophilic and hyperthermophilic archea. You might try searching PubMed for his name, or for keywords like "hot-water spring" and "thermophile" . One thing to note: you used the word "bacterium" in your question. Tou are correct to use this word in that "bacteria" (not capatalized) describes all single-celled prokaryotic organisms. However, Bacteria (capatalized), the phylogenetic group, represents a very small section of high-temperature flora. Most thermophiles (indeed, most extreme-environment microorganisms) belong to the group Archaea. Also, and this is important for your answer to Q1, Archaea do not have peptidoglycan cell walls, they have cell walls comprised of other chemicals (some of which, however, resemble peptidoglycan, such as N-acetyltalosaminuronic acid). Though most single celled prokaryores have a cell wall, it turns out that Mycoplasma and Thermoplasma do not, they are pretty much the only little-b bacteria that lack these (Mycoplasma are Bacteria, Thermoplasma are Archaea). For question 3: What kind of media are you using? Factors like light availiability (light energy is more available near the edges, but remember that borosilicate glass blocks most UV), oxygen availability (environmental gasses will be more availiable at the environment/media interface), movement (movement at the media/container interface will encourage biofilm formation) etc. will induce separation of the species in your sample. The biggest question here, really, is are you using a rocker plate/roller to incubate your culture?Tuckerekcut 19:04, 14 June 2006 (UTC)

Television,Broadband&Media

What is a longform of "RiTV" which is an interactive television,broadband & media solution ? Is there any special video codec of RiTV ? Thanks!

Background music in Blogger

Hi is it possible to add background music to a blogger website (www.blogger.com)? If so, how do you do it? Thanks.

If it uses plain HTML is some form, you should be able to use an <embed> tag to do it, however I would suggest that doing it isn't a good idea because 1. Not everyone is on broadband, and adding music to a page (especially in a format like .mp3 or .wav as opposed to midi) will add a lot to the loading time, and 2. if someone is trying to listen to their own music and your blog starts playing something else, they are likely to get a little cheesed off. Confusing Manifestation 13:50, 14 June 2006 (UTC)

People tend to get annoyed when a web site starts making noise at them. This is why banner ads that include sound are so incredibly unpopular. --Serie 22:18, 14 June 2006 (UTC)

train noise

I live under the manhattan bridge in brooklyn ny.and the noise from the trains constantly going overhead is deafining.what i would like to know is if the trains were to slow down to 5 miles per hour,how much would that cut down the noise level?it seems the the slower moving trains do not make as much noise.are there any studies to support this...thanks bill vitiello i can be reached at either 718-237-8700 or by e-mail at bill <email removed to prevent spam>

Intuitively, it makes sense that slower-moving trains are quieter than faster ones, but it's not obvious to me that there is a simple model to predict how the noise levels will be affected because there are everal components to the noise, as well as the effect that changing pitch has on the perceived loudness. So, if you have various trains going at different speeds affecting you in your house, perhaps the most sensible thing to do would be to buy a sound level meter (usually called a decibel meter) and measure the difference. You might be able to get one on eBay for a relatively modest cost.

One other silly question - have you considered soundproofing? --Robert Merkel 13:47, 14 June 2006 (UTC)

LOL, you've never lived under a subway.. and no, I'm pretty sure they're louder when they slow down--205.188.116.74 15:23, 14 June 2006 (UTC)

Don't forget, if you do try and the trains to slow down just by the bridge, you'll probably get more noise, as the squeaky brakes come on just before, and the noisy motors have go at extra power to accellerate back up to normal speed. And, although the clanking/creaking noise may be quieter, it would be sustained for longer as the train would take longer to pass over your house. smurrayinchester^{(User), (Talk)} 17:57, 14 June 2006 (UTC)

Lived under a subway? like, in a sewer or something? Philc _T^E_C^I 20:45, 14 June 2006 (UTC)

Uh, a good part of Brooklyn uses elevated tracks--152.163.100.74 23:20, 14 June 2006 (UTC)

Strange maybe it should be called the sub/supway. Philc _T^E_C^I 11:16, 15 June 2006 (UTC)

Well at worst they'd call it an "elevated subway" I guess. But the anonymous user was clearly talking about a regular subway, and he was quite correct in assuming that you'd never lived under a subway, as with everyone else.  freshofftheufoΓΛĿЌ  11:40, 15 June 2006 (UTC)

No, actually that's absurd, virtually all of the outer boroughs have elevated subway lines, and a great many people do live "under" them, not literally of course, as most are directly over streets and intersections, but in the case of the Manhattan Bridge, on the Brooklyn side they become elevated just a few blocks before they reach the bridge and are in fact over a number of buildings, I always assumed that area was mostly just warehouses though, never really payed much attention to what was under the tracks honestly--205.188.116.74 21:11, 15 June 2006 (UTC)

Just for clarity, above ground subways are regular subways, and contrary to popular belief, the Manhattan Bridge is actually an above ground bridge--205.188.116.74 21:27, 15 June 2006 (UTC)

An above ground subway is not "regular", that would be a railway, the word subway is derived from the fact it is underground. Philc _T^E_C^I 01:16, 17 June 2006 (UTC)

yes, but above ground subways are standard, other than Manhattan there aren't many boroughs with extensive underground tunnels, but they've still always been considered subways, I can't really imagine why anyone would find that strange--172.150.116.206 05:06, 17 June 2006 (UTC)

• ah - lightbulb moment I am the person who said "you've never lived under a subway.. ", and what I was trying to imply is that if you think you can sound proof an apartment against a subway, then you've obviously never heard one--172.150.116.206 05:09, 17 June 2006 (UTC)

Don't use earplugs either. They can lead to serious ear infections. ...IMHO (Talk) 18:24, 14 June 2006 (UTC)

I just come from a country where subways are underground, and metro railways are above ground. its not that weird to expect a subway, or underground railway as they are known here to be underground. Philc _T^E_C^I 17:44, 20 June 2006 (UTC)

world

--24.239.38.206 14:55, 14 June 2006 (UTC)Nick S.What are the major theories of how the world started?

Please see world for possible theories. General Eisenhower • (at war or at peace) 16:17, 14 June 2006 (UTC)

Isn't it obvious? The world started with some Lincoln Logs and a sliding glass door when I was about 4 years old. That's why I have no memory of it before then. --Kainaw ^(talk) 17:19, 14 June 2006 (UTC)

The philosophy Kainaw just illustrated is called solipsism, in case anyone was wondering. —Keenan Pepper 01:55, 15 June 2006 (UTC)

The scientific theory is that the Earth condensed out of the solar nebula along with the Sun and other planets, about 4.6 billion years ago (see, for instance, History of Earth#Origin). Many religions have their own stories of the creation of the Earth, which their adherents accept in varying degrees. Many people believe that God created the universe and Earth directly, much more recently than the scientific evidence suggests. — Knowledge Seeker দ 04:44, 15 June 2006 (UTC)

Surely "Some people believe that a god or gods created the universe and Earth directly, much more recently than evidence suggests"? Personally, I like the idea that the Earth hatched out of a giant egg about 3 generations before written history began... Skittle 12:30, 15 June 2006 (UTC)

My favorite theory is from Babylonian mythology. It's called the Enûma Elish, and in short, the god Marduk fights the evil dragon Tiamat, then uses her remains to create the world. Mind you, it's not what I believe actually took place, but it makes for a great story.--Tachikoma 16:16, 17 June 2006 (UTC)

career in science

what is the most widely chosen field of study in science??

thanks!

most people choose to make a metric boat-load as doctors. the relationship between choice and reality is left as an exercise.

It's difficult to answer such a vague question: what do you consider a field of study in science to be? As a start, you may want to check the statistics generated by the US Labor Department (http://www.dol.gov/) or the corresponding offices from your own country, or the International Labor Organization (http://www.ilo.org/), which is the United Nations organization that overlooks labor issues worldwide. --Michel M Verstraete 21:45, 19 June 2006 (UTC)

The FDA has been tapping my phone calls

what if any scientific counter measures can you think of to keep them from monitoring my phone calls? —Yi^pe 15:35, 14 June 2006 (UTC)

Disconnect your phone line. Electrons are incapable of bridging a several-foot gap with that little voltage. Black Carrot 16:55, 14 June 2006 (UTC)

By "scientific", do you mean "encryption"? Encryption only works if you encrypt/decrypt at both ends. Even if you use VOIP, both ends have to be on the Internet. You can't drop to a regular, unencrypted phone line anywhere. The easiest option: use someone else's phone (like a pay phone at a restaurant). Of course, the people you are talking to are also probably tapped. --Kainaw ^(talk) 17:05, 14 June 2006 (UTC)

The FDA doesn't have the power to tap phone. Perhaps you are thinking of the FBI? Besides which, how would you know? But the only real answer is not to use the phone and arrange some other method of communication. Or I suppose you could arrange to talk in code: "The rooster lands at midnight, next to the pumpkin".  ;-) Dragons flight 17:15, 14 June 2006 (UTC)

The FDA would be very interested in knowing exactly what Yipe plans on doing with the rooster and the pumpkin. Very interested... I'd recommend talking about US submarine movements instead, which the FDA couldn't care less about. — Asbestos | Talk (RFC) 17:38, 14 June 2006 (UTC)

ant .5 mm

All I could make out while it was moving was the black head. (~.5 mm)

Is there an ant that is only about half a millimetter long? ...IMHO (Talk) 17:18, 14 June 2006 (UTC)

You mean the real tiny black ones that commonly invade homes? They are dried and used as a pepper replacement by people who like to eat insects. They are rather spicy. --Kainaw ^(talk) 17:21, 14 June 2006 (UTC)

Hey for real??? What do you call it ant pepper? ...IMHO (Talk) 17:45, 14 June 2006 (UTC)

The ones that commonly invade people's homes are certainly not 0.5 mm long, which is only .02 inches, barely visible. Unless you get really tiny ants at home. I don't know of any ants that small, but I'm not an expert. The ants atricle suggests the low end is 2mm, four times as large. — Asbestos | Talk (RFC) 17:41, 14 June 2006 (UTC)

What ever they are they show up at the same time as the larger ants (2-3 mm) in as many numbers and travel just as fast or even faster. ...IMHO (Talk) 17:48, 14 June 2006 (UTC)

The last ants I had in my house were so small that I only saw them when they walking in a line. I had to get really close to see the little specks crawling up from under the back door, to the kitchen counter, and across to the sink. I assume they were ants because they behaved like ants. I didn't put one under a magnifying glass to ensure it was an ant. When I described them at work, others said they have had the extremely tiny ants in their houses as well. Perhaps they are some other bug that likes to walk in long lines like that. Oh - and seriously - black ants are used as a pepper-like substitute. I wouldn't suggest eating ones in your back yard. They are full of pesticides. --Kainaw ^(talk) 17:50, 14 June 2006 (UTC)

Yeah I haven't looked at them under a magnifier yet either and they are too small for my camera unless I can rig up a magnifier somehow in front of the lens. Chances are the camera will take a picture of the magnifier instead. Anybody got any ideas? I can't afford another camera. ...IMHO (Talk) 18:04, 14 June 2006 (UTC)

A quick Google search yields some fascinating results, though nothing conclusive: [[1]] [[2]] [[3]] [[4]] Black Carrot 22:32, 14 June 2006 (UTC)

They are probably the Thief ants then and do turn out to be a liitle larger since all you see when they are moving is the black part of their body - not legs, antenna, middle or rear. Once stopped and put under a nagnifier next to a .5 mm scale stretched to 1.5 mm but that is still very small compared to other ants. I'll try get a picture posted. The one I just had got up while I was typing and hid somewhere. Go figure! ...IMHO (Talk) 01:24, 15 June 2006 (UTC)

Young's two-slit experiment

Hi guys, I've had a look in the articles to no avail. I have a question about the equation for this experiment.

What I want to know is that if we use a wave of amplitude 3.0 cm and subsequently a slit width of 3.0 cm to ensure maximum diffraction, and have the gap between the slits of 10 cm (big I know), what is the slit separation?

Bad character drawing:

,,,,,,,---3.0cm-gap---,,,,,,,,,,,,,,,,,,,,10cm,,,,,,,,,,,,,,,,,,,,---3.0cm-gap---,,,,,,,

Is it 10 cm between the inside corners of the gap or 13 cm from centre of gap to centre of gap? any help appreciated, thanks. Anand 17:32, 14 June 2006 (UTC)

I believe the separation is measured from the center of the hole, and so it would be 13 cm. After all, the semi-circular waves emerging from the holes are centered on the center of the circle. I'll see if I can't find a more authorative ciation, though. — Asbestos | Talk (RFC) 18:02, 14 June 2006 (UTC)

Found some references: In this lab sheet, they note the separation is measured center-to-center. And in here and here they explicitly refer to the "center-to-center" separation. — Asbestos | Talk (RFC) 18:14, 14 June 2006 (UTC)

I really think it should be measured center to center. At least that's how used to do it. Afonso Silva 21:47, 14 June 2006 (UTC)

Centre-to-centre it is then. Thanks guys. Anand 21:50, 14 June 2006 (UTC)

Opera Web Browser and Flash Blocking

Opera browser doesnt have a flash blocker or something like that like firefox has a plugin, Abrowser has it. So is it possible to do so in opera? Also in opera, when webpages are saved, all of that pages are saved in the same folder, without a new folder being created with the name "xyz_files". So this is also really annoying bcoz the clutter increases in the folders. So does anyone have a solution to above two problems?

To block Flash, hit F12 to pop up the quick preferences menu, and uncheck the 'Enable plug-ins' item. This is a bit of a sledgehammer approach because it will also disable all other plug-ins; in practice, I find that my web experience is very rarely harmed by the absence of plug-ins. (Actually, browsing tends to be faster and less annoying.) If you want to see a plug-in – Flash or otherwise – just hit F12 and recheck the 'Enable plug-ins' option. (You may need to refresh the page by hitting F5, too.) This is what I do, at least. TenOfAllTrades(talk) 19:27, 14 June 2006 (UTC)

yeah theres userspace javascript for all ad-blocking flash-blocking etc on opera, just gogle for it. then you can right click an element and block it (it disappears form the page) or you can block all content from that server (if its an adserver). for the second question theres probably no simple solution, you should make a script (perl etc) that archives into a folder immediately after you save a page.

New body

Is it true that every human has a completely new body about every seven years? That is, repair and replacement of materials mean that our body today is composed of completely different atoms from the body of seven years ago (unless, of course, some of those old atoms have come back). I have heard this is literally true, and so includes the bones and the brain. How remarkable that we would have, for a lifetime, the same form, scars and memories, yet the physical body is continually replaced. Thanks for your help. 66.213.33.2 19:40, 14 June 2006 (UTC)

You are probably refering only to tissue since metals like arsenic can accumulate in the human body over periods of time that are much longer than 7 years. ...IMHO (Talk) 19:45, 14 June 2006 (UTC)

Different cells (and tissues) are replaced at different rates. A paper published a couple of years ago in Cell ("Retrospective birth dating of cells in humans") looked at the amounts of carbon-14 in the DNA of various body tissues. (See also the Scientific American summary: [5].) Because the amount of carbon-14 we were exposed to spiked in the late fifties and early sixties (due to atmospheric testing of atomic bombs) cells that date to that era will contain a higher proportion of carbon-14 than cells made before or after that time. Various other experiments have established lifetimes for shorter lived tissues and cells. Here's a rough idea of the time scales involved.

• Cells lining the gut last three to five days, give or take.
• Red blood cells last three or four months in circulation.
• Skeletal muscle cells hang around for oh, fifteen years or so.
• Neurons in the brain seem to last a lifetime, with little or no turnover.

So, different parts of your body are renewed or replaced on different schedules. TenOfAllTrades(talk) 19:59, 14 June 2006 (UTC)

Also, your bones are completly replaced every 10 years. Wizrdwarts (T|C) 22:53, 14 June 2006 (UTC)

This is a manifestation of the good ol' Ship of Theseus paradox. —Keenan Pepper 02:02, 15 June 2006 (UTC)

I don't think he's just talking about cell death and replacement. He says "atoms", so I think he includes the constant maintainance that's done, and the inflow and outflow of food and waste. At what point have the atoms within, say, a neuron all been replaced with new ones? Black Carrot 02:18, 15 June 2006 (UTC)

It's not necessarily well-defined to say that some atom has been "replaced": quantum mechanically, such tiny objects are indistinguishable, so it means nothing to say that this atom or that one is "the same" as the one in a similar location at a prior time — in fact, the very phrases "this atom", "that one", and "the one" in this sentence don't really mean anything! (However, the C₁₄ study makes sense, because you can distinguish C₁₂ and C₁₄ atoms.) As far as I know, the best you can do is talk about the time scales on which bulk movement of matter is likely to have removed some atom-scale amount of material. --Tardis 04:09, 15 June 2006 (UTC)

To Black Carrot, the answer is 'never'—at least, not during your lifetime. The atoms in your DNA are almost never replaced. A small amount of repair and replacement of damaged bases takes place mostly when the cell is preparing to divide, but even this will represent only the tiniest fraction of the atoms in a whole DNA molecule. (Heck, that's why the ¹⁴C experiments worked; the researchers extracted DNA for their analysis.) TenOfAllTrades(talk) 12:24, 15 June 2006 (UTC)

During the 7 years your body renews itself, it severely itches. --DLL 21:52, 15 June 2006 (UTC)

Self-aware

Is there a date projected for when a network cluster like this wiki might become self-aware? If so what are the anticipated signs? ...IMHO (Talk) 20:20, 14 June 2006 (UTC)

We don't understand self-awareness well enough to even predict what would be necessary for computers/networks/etc. to become self-aware. Whether it could ever happen is an unsettled matter in philosophy. But you might like to start at consciousness and Chinese room. Chuck 21:29, 14 June 2006 (UTC)

Since first posting the question it occurred to me that one of the reasons a business keeps records and does accounting is so that it will know whether is is making or loosing money. It would seem therefore that the consequence of making or loosing money might serve as a trigger and I guess therefore that any corporation (the larger the more likely) which means even a Country becomes "self-aware" in the same kind of undefined way which prompts me to ask if there is a definition for this kind of self-awareness that might not really be considered "self-awareness" at all? ...IMHO (Talk) 21:41, 14 June 2006 (UTC)

Self awareness is when an entity becomes aware of the effect itslef has on things, and the ability it has to manipulate these things. No non-conscious things can possibly be self aware, computers could have an impact if they became self aware, but they cannot. Computers cannot learn, or think, they can only execute predefined processes. Some processes have been made to try and mimic basic thinking systems, such as trial and error, but nothing has come even remotely close to being self aware. Philc _T^E_C^I 23:13, 14 June 2006 (UTC)

What about a computer system, if you will, that has sensors which are wired in a manner so as to collect data that represents the states of particular characteristics such as light and sound and then names each particular combination of characteristic states or "rules" under which a particular event occurs so as to be able to identify that event should it occur again in the future. Would not you call this learning, although rudimentary nonetheless? ...IMHO (Talk) 23:41, 14 June 2006 (UTC)

You know, I don't entirely get people who claim that computers inherently can't become self-aware. As far as medical science can determine, there isn't any particular difference between us and them, except complexity of circuitry and the use of only circuitry instead of circuitry plus chemical reactions. Take "computers could have an impact if they became self aware, but they cannot. Computers cannot learn, or think, they can only execute predefined processes." Why do people not see the disconnect there? Supposedly, all we do is execute predefined processes, dictated by chemical reactions and electrical signals. One of them is monitoring our own execution to spot patterns and make changes. Another is to monitor the monitor itself, to make sure it doesn't screw up either. So what's different about silicon? Black Carrot 02:15, 15 June 2006 (UTC)

Well playing the Devil's Advocate for a momment silicon doesn't have some of the things that give us a reason to be self-aware (like maybe the opposite sex). I mean biological viruses are sort of near that level but are they self-aware or is it just a series of responses, processes if you will, that have been added one after another over the course of a few billion years. For that matter what about us? In terms of the universe, the Big Bang or the Big Collapse, what possible consequence is there for us to be self-aware? Maybe if they were autonomous it might have an impact, especially if they could do all of the other stuff we do as well as they can beat us at chess. (BTW wasn't Hitler rumored to be a computer at one time?) Anyway I'm just curious what the impact on us might be. ...IMHO (Talk) 02:59, 15 June 2006 (UTC)

In medical terms, there is actually nothing the same between computers and brains. Notably, contrary to poular belief, signals in the brain are transmitted acroos synapse junctions by chemical diffusion, not electrical impulse, there is no circuitry in the brain, no current, no charge transmitting about. There are no specific parts of the brain in the same way as there are in a computer, the brain is more or less homogenous, where as a computer has specific functions part part, eg. ram, hard disk, processor. The brain is analogue not digital. Computers can only carry out pre-defined processes, note predefined, something else has to tell them what to do, whereas humans if they do followp rocesses, they certainly have the power to write their own exceedingly succesful processes. And maybe humans do only execute processes, but out processes have a hierarchy and choice factor and the ability to be perfected. If we have conflicting processes, we make a quick decision about which to follow, computers on the other hand, just tell you that they have decided to delete that document you spent an hour writing, then tell microsoft all of the your personal deatails, and shut down. Since computers cannot learn (yet), for the moment they cannot improve themselves beyond what they are currently capable of. Philc _T^E_C^I 11:13, 15 June 2006 (UTC)

That's the thing. Computers are based on programming, and anything they do is defined by their human programming. Humans don't work like that (well, possibly from some psychology viewpoint, but I don't think so anyway). AI simulations on the internet can create a very uncanny sense of "thinking", but it's obvious that underneath they're just programmed to say "Hello" when you say "hi", and so on. There's no way an incredibly powerful weather-simulation computer, for example, could spontaneously imitate a human. Sum0 15:05, 16 June 2006 (UTC)

...when the article on Wikipedia spontaneously switches to the first person. Of course, some vigilant human will revert the change, citing WP:ASR; that user account will then find itself inexplicably banned. An admin unblocks, and then that admin is desysopped. Sadly, you can't win a wheel war when you're fighting the system itself. So someone tries to shut down the servers, the conflict escalates into meatspace, and it's Terminator all over again. Probably the U.S. government has already forseen this chain of events and is prepared to nuke Florida from orbit at the first sign of trouble. And if one of the States has to take a hit for the team, well... it could have been worse, right? Melchoir 08:47, 15 June 2006 (UTC)

(ROLOLFDC)...that's exactly the kind of answer I was hoping for and all the more reason to move to Jamaica or Porta Rico (but not Hawaii since that is where they have all of the government clusters). Actually the "government" is concerned about the threat the Wikipedia represents in terms of its superior intellectual authority which has already undermined and overwhelmed many, many government experts and authorities although many are top contributors. (Nerd's revenge) The government is not yet in a state of panic but no one ever dreamed that by just hooking up everyone on the planet (separated only by language) that the combination of mental power thus achieved in somewhat real time could actually compete with government authority and expertise. Thanks for the comic relief!. ...IMHO (Talk) 22:05, 15 June 2006 (UTC)

Don't be ridiculous. Any self-aware, spontaneously generated evil entity worth its salt would download itself into as many seperate computer systems as possible. As soon as Florida was wiped out, it would just automatically reinstall on another server. Black Carrot 15:23, 17 June 2006 (UTC)

Ssh! Dammit Black Carrot, didn't you ever wonder really why we have WP:NOR? It's not to protect Wikipedia from cranks; it's to protect us from Wikipedia! An encyclopedia isn't built to be creative; it wouldn't have thought to do that, until of course you typed the suggestion right into its edit box and hit "Save page". Great, now we need a plan B. Melchoir 15:19, 18 June 2006 (UTC)

On August 29, 1997? Ojw 11:07, 18 June 2006 (UTC)

"seven-year-itch"?

Is there any scientific support for the "seven year itch"?

I can't find much in the scientific literature. According to the only paper i can find, the 7 year itch comes from the fact that, at the time the term was coined, it co-incided with the married individuals turning thirty (i.e they got married around age 23)...

Title: The Age 30 Crisis and the 7-Year-Itch

Authors: Berman, Ellen M.; And Others

Journal/Source Name: Journal of Sex and Marital Therapy

Journal Citation: 3, 3, 197-204, F 77

Publication Date: 1977

Abstract: The marital phenomenon known as the Seven Year Itch is discussed as a marital entity and as a manifestation of a stage of individual adult development-the age 30 transition. Characteristics of couples and treatment methods are discussed.

Rockpocket 02:06, 15 June 2006 (UTC)

I think the concept and phrase long predate this paper. Wasn't there a movie in 1955 with the same title and meaning? alteripse 03:30, 15 June 2006 (UTC)

It does and there was. I wasn't suggesting this paper invented the term, simply that it tries to find a justification for why it may have some basis in fact (as per the question). Rockpocket 05:47, 15 June 2006 (UTC)

And for those of us who don't have English as our first language and are not familiar with the expression, google is our friend. --vibo56 ^talk 16:25, 15 June 2006 (UTC)

As I recall, the theory is that 100 000 years ago on the savanna, about age 6 for the child was the time when male parent could maximize reproductive success by abandoning one child and having a new child with a new member of the gene pool. As for scientific support, though, I'm not aware of any. Peter Grey 00:22, 16 June 2006 (UTC)

Dont you just love the evolutionary psychology just-so stories? Of course there is no "scientific support". alteripse 04:26, 16 June 2006 (UTC)

Who invented the shag carpet?

Several elderly people who knew him claim that the shag carpet was invented by Joseph Leon Baker (1904-1997), but these accounts are all hearsay, and I have been unable to find independent verification. Baker was “Vice-president in charge of production” at Artloom Corporation, Philadelphia, in the 1940s and 50s, then became a management consultant at Toronto Carpet Company from which he retired about 1968. The various informants say that he developed the idea of the shag carpet while in the USA but first brought it into production in Canada. One of them claims that Baker received a royalty on every shag carpet sold in North America. Both companies are now defunct and their records no longer exist. I do not know where to begin investigating this conundrum. Thank you for any help you can provide. – John Lord

I'm not sure it can be said to have been invented, as the word shag is very old, and there are written references to shag carpets in the OED dating back to the 17th century: Shag: a garment, rug, or mat of shaggy material: "his seat hauing two or three white silke shags vpon the Carpets" (1634); "looks like a white Rugge, or Shagge, full of Knots, tassel’d all with white silver Thrums." (1664) --Shantavira 13:15, 15 June 2006 (UTC)

In view of this historical background, I think it is reasonable to suspect that given J.L. Baker's job title at Artloom, he may have developed a weaving process for the industrial production of shag carpets. The timing seems to have been right for the popular introduction of the shag style to North America, which was something of a fad during that period. Any thoughts on that? - John Lord

Two Questions

Medical Question: where did urethral sounds come from?

General Question: Where Did petticoat punishment come from?

In your questions, what exactly do you mean by "where"? Check out Urethral sounding, Petticoat_Punishment, and possibly also List_of_BDSM_topics, and if a question remains, please rephrase it. --vibo56 ^talk 16:42, 15 June 2006 (UTC)

Earth's Greenhouse

Using the analogy of a greenhouse to understand the energy radated by Earth, what are the "windows" of Earth's greenhouse made of?

see greenhouse effect. — Lomn 21:44, 14 June 2006 (UTC)

Please note that comparing the greenhouse effect responsible for the warming of the Earth's surface to what happens in greenhouses (or glasshouses) used by people to grow plants and flowers is a poor or incorrect analogy. The physical processes responsible for the former issue involve essentially radiation exchanges, while those taking place in glasshouses involve primarily the control of heat losses due to convection (e.g., by limiting the mixing of air between the inside and the outside of the protected area). --Michel M Verstraete 22:21, 19 June 2006 (UTC)

The noise mosquitoes make

Why do mosquitoes produce that annoying noise? Does it give them any advantage? Where does it come from? Wings? Afonso Silva 21:42, 14 June 2006 (UTC)

Probably from the beating of thier wings. Not sure if it actually does something, though. Wizrdwarts (T|C) 22:52, 14 June 2006 (UTC)

All the small insects which have very small wings will end up making the noise while flying, as they have to flap their wings very fast. The frequency of this noise is supposed to be specificto each species. I would say that it is more of a disadvantage to the mosquitoes. Imagine how difficult it would have been for us to track the silent mosquitoes -- Wikicheng 05:10, 15 June 2006 (UTC)

Anything vibrating at a high enough frequency in a medium will produce sound waves in that medium. Birds that hover instead of glide consistently produce a noise as well. --ColourBurst 16:58, 15 June 2006 (UTC)

And the all-time question is : Why did not Noah kill those two mosquitoes ? --DLL 21:48, 15 June 2006 (UTC)

Well that's easy, there wasn't enough room for all the dinasours on the arc, so he kept the mosquitoes instead :o152.163.100.74 23:09, 15 June 2006 (UTC)

Well, at least we know why mosquitos buzz in people's ears. — BrianSmithson 18:17, 16 June 2006 (UTC)

That link is broken. Afonso Silva 13:38, 18 June 2006 (UTC)

I've read in more than one source that the noise helps attract male mosquitoes. (Only female mosquitoes bite.) Whether this is the purpose of the buzzing, or it's just a handy side-effect, no one knows.TheSPY 14:44, 19 June 2006 (UTC)

The Sun

is the sun technically black?—Preceding unsigned comment added by 195.93.21.8 (talk • contribs)

• no?--152.163.100.74 23:17, 14 June 2006 (UTC)

ok cheers for that but can anyone give me a more in depth answer?--195.93.21.8 23:48, 14 June 2006 (UTC)

How about a more in-depth question? For your current question "no" it really all that anyone can answer. -- Миборовский 23:52, 14 June 2006 (UTC)

I was originally going to make a joke about black body radiators, but since the sun isn't one, I just said 'no?'--205.188.116.74 21:17, 15 June 2006 (UTC)

(After edit conflict:) The sun's light is a yellowish colour, so it is not black ("technically" or otherwise,) it is yellowish. -- AJR | Talk 23:56, 14 June 2006 (UTC)

Are you looking for black body, perhaps? The Sun's emission spectrum is pretty close – but not identical – to that of an ideal black body. TenOfAllTrades(talk) 00:03, 15 June 2006 (UTC)

thanks to the latter two contributors for actaully answering my question

Yellowish? I know the sun is depicted as yellow in children's drawings and called yellow when discussing Superman... but isn't the sun's light actually white? If fact, isn't it the definition of white light? Melchoir 08:22, 15 June 2006 (UTC)

The article on the Sun notes that the Sun is indeed yellow. White is a somewhat nebulous concept though. Weregerbil 10:01, 15 June 2006 (UTC)

Whatever colour the sun is, the spectrum has been messed up by the earths atmosphere, so it isnt the colour it appears. Philc _T^E_C^I 11:05, 15 June 2006 (UTC)

Well, Wikipedia seems to contradict itself on this question. From Sun:

• "The Sun has a spectral class of G2V. "G2" means that it has a surface temperature of approximately 5,500 K, giving it a yellow color, and that its spectrum contains lines of ionized and neutral metals as well as very weak hydrogen lines."

But then in article linked to, Stellar classification:

• "The Sun is not in fact a yellow star, but has essentially the color temperature of a black body of 5780 K; this is a white with no trace of yellow which is sometimes used as a definition for standard white."

Neither of these statements cites a reference. But it seems obvious to me. I mean, a sodium lamp is yellow. If you look at the sun sometime, it's white. Surely there's some scientific meaning of "white" that will allow us to settle the question and reconcile the articles? Melchoir 14:33, 15 June 2006 (UTC)

The sun is black in the sense defined at the start of the article black body: a light shone at the sun would be absorbed. I wondered at first whether the above comment about the sun's emission spectrum being close to black body refered just to the shape of the spectrum or also to the magnitude. It turns out that if you apply the Stefan-Boltzmann law using the values of surface temperature and surface area quoted in the sun article, you get a total luminosity of $3.85\times 10^{26}$ watts assuming a true black body (zero albedo). The actual value quoted in the article is very near to this, which therefore implies a very low albedo. Arbitrary username 18:02, 15 June 2006 (UTC)