Wikipedia:Reference desk/Archives/Science/2007 August 26

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August 26[edit]

Prozac and Weight Change[edit]

I was wondering what Prozac does to cause weight loss and weight gain in some people. Is it from a change in appetite or does it have to do with something else? Which is more common? Weight loss or gain?

Prozac is a psychoactive drug. "Weight loss" and "wieght gain" are terms usually used to describe human behaviors. Prozac can have major effects on human behavior. I cannot cite any specific studies, but I I would guess that any effect on weight is a secondary effect. For example, Prozac is apparently used to treat bulemia nervosa. -Arch dude 03:54, 26 August 2007 (UTC)
I don't know either but I think the answer is easy to guess. Change in appetite is a very common effect in depression. I suppose everybody knows people who start eating a lot when they are depressed or stressed or whatever, and other people who eat less and less in such times. So, given that our appetite is so much coupled to our mood, shouldn't it be obvious that any mood-influencing drug changes appetite and hence over time body weight? Simon A. 10:28, 26 August 2007 (UTC)
Yes many depressed people tend to eat more to comfort themselves and gain weight, but many also gain weight rather then lose weight when taking prozac. I don't think the answer is that easy.
I gained thirty pounds while taking Prozac in 1996, and forty more over the next two years. During that time I had no acute depressive episodes, and they came back when I stopped gaining weight, or vice versa. Draw your own conclusions. —Tamfang 07:37, 27 August 2007 (UTC)

Psychology[edit]

I am currently in grade 12 and thinking of entering the field of psychology, specifically criminal psychology and I was wondering what route I should take regarding schooling. And what schools in Canada would be best? 75.154.106.228 04:47, 26 August 2007 (UTC)

Don't make hasty decisions, just because you think CSI or Criminal Intent or whatever it is on TV these day is cool doesn't necessarily mean it's true (if you are one of the millions of 'kids' that decide your career on TV programmes). --antilivedT | C | G 05:54, 26 August 2007 (UTC)
Don't condescend. He/she's a senior in high school and asked a well-directed question, I think we can afford to take it seriously. Anyway CSI is all about forensic investigation, not criminal psychology, if I recall, so if you are going to cast aspersions about his/her motivations, you might as well get the reference right! --24.147.86.187 13:05, 27 August 2007 (UTC)

I have not made this career choice because of shows on TV I have never watched any of the CSI shows or anything like that. I have done extensive research on this career, and chose it because it interested me.

You'll presumably want a general sciences background, with perhaps some pre-law stuff thrown in. Keeping your education focused on fundamentals will afford you the greatest flexibility later on. As for schools, I personally would go to University of British Columbia, as it's a great school in a world-class city. --Sean 19:47, 26 August 2007 (UTC)

I don't think there's anything wrong to having a goal for your education to a specific goal career — we can't all be generalists, and most people who graduate from undergrad these days have so inspecific of skills that they can't do anything without an additional year or two of education. Unfortunately I don't know the specifics of what that particular career requires, and I'm averse to just speculating on it. My recommendation would be to find a university with a criminal psychology program (even one you are not planning to go to) and try to contact someone there for advice. Someone "on the inside" will be able to give you good advice as to what sorts of backgrounds are more desirable, what level of education is normal for a practitioner (does it require a master's degree?), and what universities have good programs for that sort of goal. --24.147.86.187 13:03, 27 August 2007 (UTC)

Two general routes to becoming a shrink; one via MD one not. If you don't have an MD, you're not allowed to prescribe drugs, which is kind of a big part of the biz these days. But, not everybody is cut out for med school, for sure. They have to send patients out to an MD to do the drug prescribing and periodic monitoring and so on. Anyway, something to think about when you're sort of thinking through your plans. Gzuckier 14:48, 27 August 2007 (UTC)
  • The MacLeans survey might help (most of it requires a subscription, sadly). --M@rēino 17:24, 27 August 2007 (UTC)

You might want to seriously consider something fairly local since it'll likely be cheaper and easier for you. I'm not a Canadian but I would assume most Canadian schools/universities are fairly decent from a general perspective. For a more specific perspective some might be better then others but often the student matters more then the university. As for what route, I would suggest you speak to a career counsellor in your current school and probably one in some of the prospective universities as well. The fact that you have a specific goal in mind makes it a lot easier since a lot of people have no idea. Also, you can likely find information on the university websites. Finally since your job is likely to be with your law enforcement, you might want to contact them for advice and particularly see if you can get in contact with someone working in the field to try and help you decide whether it's really the job for you (they can likely offer you advice on universities and stuff too). Nil Einne 00:51, 28 August 2007 (UTC)

Actually on second thought you don't really have to be working with law enforcement that much. You work could be more in the academic area so you could try talking to someone in that area too Nil Einne 00:59, 28 August 2007 (UTC)

Newtonian camera[edit]

Would it be possible to make a camera (lens) that uses the same principle as a newtonian telescope? I imagine it could be done simpler, with a mirror behind the lens (if any) that reflects the light to the side, where the sensor then should be. That would be a way to make the camera flatter, a solution to a substantial practical problem, especially with the better lenses, which are always too bulky to always carry around. Actually, come to think of it, why aren't photo cameras made the way film cameras are, with the lens at the narrow end? That would also get rid of the sticking out lens. Actually, some cameras are moving in that direction, but why don't they take the final step? DirkvdM 09:09, 26 August 2007 (UTC)

partial answer - newtonian telescopes don't make very good zoom lenses...that said some lens do utilise mirrors - Catadioptric systems
traditionally photo cameras were that shape because of the shape of the negative+film roll..
For maximum stability of a camera holding it with two hands helps - it could be argued that the classic shape is better for two hands holding than a cine-camera shape?87.102.44.85 10:41, 26 August 2007 (UTC)
It's actually quite difficult to make a 'fast' Newtonian reflector – that is, one with a small focal ratio that will fit in a short tube – that produces good images. Consider the workhorse zoom telephoto lens on my camera. It gathers light through an opening 72 mm across, and focuses it onto a film plane only about 150 mm away. In that length, I also get all the optics I need to focus, control my depth of field, and zoom the apparent focal length from 28 mm to 80 mm. In contrast, a typical Newtonian reflector will tend to have a length that is at least four to six times its diameter (and often quite a bit more). The highly curved mirror needed for a short body is costly and hard to manufacture precisely. The particular aberrations associated with the Newtonian optics (particularly coma) are also worsened with short focal ratios.
Telescope manufacturers have adopted (at least) three strategies to deal with this. 'Slower' optics with longer focal lengths relative to the telescope's diameter reduce the effect of the aberrations, but at the cost of a longer instrument. In astronomy, ignoring the problem is actually often an acceptable solution—stuff in the middle of the field is bright and sharp, and any weirdness can be confined to material off at the edges. Finally, telescope makers have started to add lenses to reflecting telescopes: catadioptric systems. It's that final solution that most often appears in the world of non-astronomical photography. Nevertheless, it's still only used where the cost and weight of glass lenses would be prohibitively high. TenOfAllTrades(talk) 11:23, 26 August 2007 (UTC)
Mostly agree - but.. (note not technically a newtonian - but still a reflector) consider this http://www.zenit-camera.com/rubinar_1000_lens.htm a 1000mm lens - note the short length to width ratio (especially when compared with the equivalent 'glass' lens).. also consider the reduced weight (not such a big factor nowadays with plastic lens) - I just wanted to pick up on that "length that is at least four to six times its diameter" bit - newtonians can be better than glass in this respect due the 'folded' nature of the light path.(and can get very wide for good light collection..
OK I admit I'm just trying to sell this lens (also available in other fittings!).87.102.44.85 13:14, 26 August 2007 (UTC)
You need to be careful with your terminology—while all Newtonians are reflectors, not all reflectors are Newtonians. All commercial (as opposed to home-built) reflecting camera attachments will contain lens elements as well as reflecting elements, both to correct the aberrations of the basic Newtonian design and to greatly reduce the length of the instrument. The focal ratio caveat obviously doesn't apply to catadioptric systems.
Finally, you can't 'fold' the light path in a Newtonian system down to much less than its focal length. The closer the secondary mirror is to the primary's surface (and the further it is from the primary's focal point) the larger the secondary needs to be to capture all of the light. This, in turn, increases the size of the central obstruction, reducing the telescope's light-gathering ability. TenOfAllTrades(talk) 14:39, 26 August 2007 (UTC)
Interesting - looks like I meant a Schmidt-Cassegrain telescope or similar - in my ignorance I assumed it would be considered just a variation on the newtonian - thinking all mirrored telescopes/lens were newtonians. Oops!.87.102.11.213 16:51, 26 August 2007 (UTC)
My oops. When I said newtonian telescope I meant reflecting telescope. So the title should read 'reflecting camera'. DirkvdM 09:23, 27 August 2007 (UTC)
87.102.11.213, you said that reflective telescopes don't make very good zoom 'lenses', but I get the notion that the opposite is true (or did you mean that reflective telescopes have a limited range of zoom?). They're very good at zoom (after all, that's what telescopes do) and are much more portable than comparable lenses. But I just realise there might be another problem here if the secondary mirror is in the path of the light, as indicated by the macro-limit of the Zenit 'lens' linked to by you. In a telescope that mirror being in the way doesn't matter too much because the objects are huge and far away, so it will only affect the overall light intensity. But for objects closer by there is a more serious problem. Take macro photography. If the object is small and only a cm away from the camera then its light might be completely blocked out by the secondary mirror. That is an extreme example, but for objects not that close but still close the 'blockage' of light would still be unevenly distributed. Does that make sense and from which distance would it no longer be a (serious) problem?
That would be solved by not having the secondary mirror in the path of the light, but I remember from a previous thread here that that would cause more problems in constructing the primary mirror. Then again, maybe economics of scale might solve this if the cost is largely in the development of the technique and the production of the machine that makes the mirrors. Telescopes are never mass produced, but cameras are. Once you have a (polishing) machine that can make this type of mirror then the production of each individual mirror would not be so expensive, so it's just a matter of how many you can sell. Right? DirkvdM 09:23, 27 August 2007 (UTC)
Re - zoom - by zoom I meant the ability to change the focal length. I never heard of a 'zoom' telescope as such, but I know different eyepieces can change the magnification - is that the same.. Otherwise I agree the other points. I think the question is (in the case of a camera) why use mirrored optics in preference to lenses - especially when the abberations due the the second mirror are avoidable with a lens system..?87.102.45.106 11:45, 27 August 2007 (UTC)
disclaimer I'm no optics expert - it's probably the thing I know least about - I think you DirkvdM should ask a new question about the reasons why we are not using newtonians in cameras - I'd be interested to see a proper answer. 87.102.45.106 12:10, 27 August 2007 (UTC)

stepped transmission[edit]

why geometric progression of speeds is preferred in stepped transmission systems? thank you210.212.24.7 09:55, 26 August 2007 (UTC)

you mean like gear ratios 1:1,1:2,1:4,1:8 etc?
a geometric progression gives a wider range of gear ratios than a linear progression cf 1:1,1:2,1:3,1:4
So that enables both slow crawls and high speed driving.
There may another reason I've missed?87.102.44.85 11:42, 26 August 2007 (UTC)
It's not just automatic transmissions, the gear ratios (reverse, 1st, 2nd, ...etc) for four manual transmission cars I've owned recently are:
  • 1963 Austin Mini (37hp): 13.66, 13.66, 8.18, 5.32, 3.77
  • 2003 BMW MINI Cooper S (165hp): 11.13, 11.42, 7.18, 5.40, 4.40, 3.66, 2.99
  • 2005 BMW MINI Cooper S (172hp): 11.94, 12.79, 7.79, 5.65, 4.61, 3.83, 3.13
  • 2007 BMW MINI Cooper S (178hp): 11.78, 12.06, 7.77, 5.41, 4.15, 3.46, 2.97
All of them have the property that the difference between consecutive ratios reduces by smaller and smaller amounts as you get into higher gears. I believe this is because they wish to move the optimum shift points closer and closer together (in RPM terms) so that the car may be kept running within narrower and narrower torque bands - allowing you to employ more torque at higher speeds when air resistance becomes a significant factor. They also seem to have been chosen to provide efficient cruising at typical speed limits. If you look at the differences in gear ratios between 2003 and 2005 - and note that the 2005 model had just 7hp more than the 2003, you can see that careful selection of gear ratios to match small engine changes is sufficiently important to car manufacturers that even a 4% engine performance improvement warranted redesigning the gearbox! This tells you that there is a lot of science going into picking those ratios. SteveBaker 12:48, 26 August 2007 (UTC)

Building a wall or fence to block traffic noise[edit]

A noisy road has been built about 70 metres away from my house. I was wondering if I could reduce or remove the traffic noise by building a wall adjacent to my house so that I would have a small enclosed courtyard area that was open to the sky yet comparatively quiet.

The main determinant of how silent the courtyard would be, I think, would be the noise coming over the top of the wall and diffracting into the space beyond it. Thus even though below the height of the wall, you would still hear noise because of the sound waves diffracting from the top of the wall. Does anyone know how to calculate this effect? A taller wall would be better, but I'd like to estimate if an acceptable height of wall (say two metres) would still reduce the noise enough to be worth building.

I'd be grateful for any practical ideas about how to reduce the noise - for example trellisses that may reduce noise by acting as diffractors and creating destructive interference of the sound waves. Thanks. 80.2.200.132 10:33, 26 August 2007 (UTC)

I can't give you an equation - but can confirm that a wall (taller than you) will significantly cut the noise.
The other methods are pretty much as you describe - anything that can absorb a sound wave - anything solid - trees may help.
A wall would definately be 'worth building' the sound reduction effects would be significant. A hedge or row of trees would also help - pines grow fast and tall.87.102.44.85 11:46, 26 August 2007 (UTC)
This page says: A noise barrier can achieve a 5 dB noise level reduction, when it is tall enough to break the line-of-sight from the highway to the home or receiver. After it breaks the line-of-sight, it can achieve approximately 1.5dB of additional noise level reduction for each meter of barrier height". I've also seen rows of fast-growing cypress trees that are very dense, nice to look at, and apparently good for noise abatement. --Sean 12:08, 26 August 2007 (UTC)
My first guess would be that trees (especially the thick cypress variety) would form a better sound barrier than a brick or concrete wall. The trees will block the line-of-sight as effectively, but will muffle the sound better. Also, they can grow to very tall heights, which has been empirically shown (as above - 1.5 dB per meter of height) to reduce the noise significantly. Nimur 18:16, 26 August 2007 (UTC)
  • Another way to reduce noise is rubberized asphalt. If this is a new road built near existing houses, your community might be able to force the use of a surface of rubberized asphalt. --JWSchmidt 00:04, 27 August 2007 (UTC)
There are many street-noise blocking walls where I live. They are 12-15 feet tall, corrugated steel walls. Very ugly, but work well. -- Kainaw(what?) 00:23, 27 August 2007 (UTC)
I've studied sound breaking and pretty much what you'd need is a really dense, solid wall with lots of mass. Brick and concrete probably. Traffic noise is often low frequency so the wall would need to be a ways into the ground (I think--anyone know for sure??) and then I know it'd need to be high and pretty fully surround your home at least in the noise's direction. Traffic noise is worst as loud engines and loud car stereos. Juanita Hodges 01:34, 27 August 2007 (UTC)
This question has been asked before, last year I believe. Alas I don't know of an easy way to search for that. But 'the answer' I believe was a plant-barrier. This might have the added advantage that you will be allowed to make it taller than a wall. For an obvious reason - it's not as ugly. I don't know how the costs would compare, especially if you don't want to wait and want to plant big trees (with plants below them). DirkvdM 09:31, 27 August 2007 (UTC)
You'll want to wait for winter when plants are dormant for a bio-solution, but a fence of living willow would work. You can use a species that grows at a rate to match your need. Bendž|Ť 09:42, 27 August 2007 (UTC)
I strongly support the tree idea, as well, for acoustic, aesthetic, and environmental reasons. One caution is to use evergreen trees, not deciduous, as bare trees wouldn't provide much sound protection in winter. Another idea is to create an earthen berm, possibly with bushes and trees on top:
     /\
    /  \ TREES/BUSHES
     || 
   +----+
   |    |
 +-+    +-+
 |  BERM  |
-+        +-
StuRat 02:09, 28 August 2007 (UTC)
Or maybe one of those wooden fences with thin 'planks' woven through them. Horribly bourgeois, but you can have climber plants cover it. DirkvdM 06:28, 28 August 2007 (UTC)

Unidentified disease of Marigold[edit]

I have a marigold plant. It was flowering really well. Suddenlty one day I saw cobweb like stuff had developed on the flowers. On close inspection I saw small dot like white things moving in that web. This web is more like a thin veil of cotton rather than a web actually. I wasn't sure what to do so I banished the pot to the fire exit and closed the window. I did not want my other plants to get whatever it is and I thought sun might be helpful. I live in NY but am used to a more tropical weather garden. The questions are:

What is this disease? Is it harmful to other plants or to humans? How do I cure it?

Some added information: It rained heavily and the plant was soaked. I brought it indoors so that it is not harmed by the cold rain. It remained indoors for 4 days before it developed this thing. --Kaveri 13:59, 26 August 2007 (UTC)

Sounds like red spider mite. Easy to get rid of if you spray with water mist daily. (Or possibly mealy bug.)--Shantavira|feed me 15:25, 26 August 2007 (UTC)
I agree, red spider mite. They love hot, sunny, dry places so giving them a fine water spray once or twice a day will certainly control them. Check your other plants because these little monkeys can spread round a greenhouse at the speed of light. Richard Avery 10:13, 27 August 2007 (UTC)
Uh oh, looks like we're going to have to augment our disclaimer: no medical, legal, or horticultural advice! :-) --Steve Summit (talk) 17:35, 27 August 2007 (UTC)

lenses[edit]

Can't seem to find a page on 'lens manufacture' other than history of lensmaking. Is there one? I'm thinking specifically on how plastic and glass lenses are made (cast, then ground ??) rather than lens design.87.102.11.213 16:55, 26 August 2007 (UTC)

Float glass details the process of float glass, but I think this is not the common procedure for small lenses. We seem to have the historical perspective well-represented, but I can't find much on modern lensmaking either. Nimur 18:19, 26 August 2007 (UTC)

????Does "ref desk collaboration of the week" still exist - if so I'd like to put this forward. Where is it. I've also made a requested article thing as well..87.102.11.213 19:23, 26 August 2007 (UTC)

Lenses are ground into the desired shape. One problem with the grinding of large lenses is that gravity deforms them to a significant degree, so that changing their orientation or the strength of the gravity field (say by launching them into space) between production and usage can cause significant distortion. StuRat 01:59, 28 August 2007 (UTC)

Acoustics[edit]

When, say a trumpet plays a note, and then a piano play a note of the same pitch, what is the difference between the sound waves that the two instruments make that allows us to distinguish between them? Imaninjapiratetalk to me 17:31, 26 August 2007 (UTC)

The second,third,fourth etc harmonics differ. Overtones is probably the easier/better article to read here and both give you the answer.87.102.11.213 17:37, 26 August 2007 (UTC)
Also you are listening to different waveforms. See the various articles linked from that one, some of which have samples of what different waveforms sound like. The only thing the two notes have in common is their wavelength.--Shantavira|feed me 17:45, 26 August 2007 (UTC)
It's worth noting (as it's not in the article waveform) that the waveform consists of the (wavelength) fundamental frequency plus all the overtones or harmonics - bringing all three articles together.
Effectively the presence of harmonics or overtones is means that the 'note' consists of multiple pure tones - there are multiple notes being played simultaneously when a piano key is pressed - the note (on the musical score) corresponds to the first harmonic.87.102.11.213 18:07, 26 August 2007 (UTC)
Also, "imperfections" in each instrument (such as breathy noise in the trumpet) result in non-harmonic elements of the sound spectrum. You might want to investigate psychoacoustic perception, which is an ongoing research topic. Nimur 18:22, 26 August 2007 (UTC)
Then there is also the rate of attack and decay (how quickly the sound reaches max volume and how quickly it ends), which tends to vary by instrument. A grand piano, for example, will have a slower decay rate than an upright piano. StuRat 22:13, 26 August 2007 (UTC)
And the technical term for it is timbre. Confusing Manifestation 22:26, 26 August 2007 (UTC)
And Stu is referring to the adsr envelope (at least, that's the simplified model used in electronic musical instruments). Note that during attack, the pitch may also be different. DirkvdM 09:37, 27 August 2007 (UTC)
Also, the relative amplitude of the overtones can change with time. Also, some partials can be more or less out of tune (as per the 7th on a piano).
In truth, this question is being asked backwards! There is almost nothing the same between the acoustic waveform of a trumpet and a piano playing the same note. Just about all you can say is that the majority of the energy present in the sound is delivered at some specific frequency for most of the duration of both notes. All else is up for grabs and will be different. It's interesting that our brains are able to discern any similarity between the two notes at all! I suspect that some aspect of the way we percieve sound is responsible for that - but I'm no audio expert. My domain is in the world of light and eyes - and our ability to see hundreds of shades of red as all being fundamentally more or less the same "colour" is perhaps a similar ability. If so, it's an artifact of the approximate way we percieve such things ("It's a bug - not a feature!") SteveBaker 16:30, 27 August 2007 (UTC)
I'd say it's rather different for light. Calling different shades of red red is a linguistic thing - we can't have a name for every discernible shade. And perceiving a band of similar colours as one colour is a matter of lack of precision. But picking out the frequency of a note is more like a mathematical thing, probably some fourier analysis. Also note that we designed the instruments to make those notes. Non-living nature rarely produces them and then usually only a vague hint of a note. We put nature in a straightjacket to make it produce pure notes. So it's not so much that there was something there for which we developed a sense, but we had this sense for which we manipulated nature, so it would produce something for us to perceive. DirkvdM 06:39, 28 August 2007 (UTC)
The tiny hairs in the Cochlea are each tuned to a different frequency - the hairs that vibrate the most will be those tuned to middle-C - and those exact same hairs will vibrate for both the trumpet and the piano. The other hairs that respond to the overtones will also vibrate (differently in the case of piano and trumpet) - but those aren't "shouting the loudest" as the information goes to the brain. If we concentrate on the biggest signal from the cochlea - we'll hear the piano and the trumpet "playing the same note" - if we pay attention to the lesser signals, we'll hear the more subtle tonal differences between the two instruments. Our eyes only see at three different frequencies (unlike our ears which can hear all frequencies within our audible range) - but the result is the same. When the red sensor shouts the loudest - we can see that pink and red are varieties of the same thing. If we concentrate on 'overtones' from the green and blue sensors then we can tell that there are a variety of shades and brightnesses of 'red'.
I agree with you that orangy-red and red don't differ in the same way that a trumpet and a piano playing middle-C differ - an orangy-red would be analogous to an out-of-tune trumpet. But the difference between a bright red and a pinkish-red is very similar. The fourier series for pink has a peak at 'red' and 'overtones' of blue and green. But we still think of 'pink' as being 'a kind of red' - we don't imagine it to be 'a kind of green' even though there is plenty of green in there. This is not dissimilar to the idea that the overtones of a trumpet and in a piano being relatively unimportant to our hearing it as a middle-C.
SteveBaker 15:06, 29 August 2007 (UTC)

If a tree falls in the woods, does it make a sound?[edit]

answer the question!!!!--arab 20:56, 26 August 2007 (UTC) —Preceding unsigned comment added by TerrorSonghai (talkcontribs) 20:56, 26 August 2007

If a tree falls in a forestMatt Eason (TalkContribs) 21:05, 26 August 2007 (UTC)
And this entire discussion, from June 30. Without doubt, sound is produced. Nimur 21:54, 26 August 2007 (UTC)
Without doubt? That's not the answer. The answer depends on what kind of question you are really asking, as the normal one requires qualification to be precise. --24.147.86.187 22:00, 26 August 2007 (UTC)
Not really. Nobody was able to come up with any kind of reasonable version of the question in the June 30th discussion that produced a tree that falls in a forest without making a sound. The nearest anyone came (IMHO) required a redefinition of the word "sound" in a way that fits no dictionary definition. What do you think is unclear? SteveBaker 23:47, 26 August 2007 (UTC)
OK, I made many comments that I removed now. Science simply cannot answer any question, including this one, as the article on science correctly states. A.Z. 03:11, 27 August 2007 (UTC)
This thread is at grave risk of turning into the kind of debate which the reference desks frown on, but: this last is of course nonsense. Science can answer many (if not most) questions, and it can answer them to an arbitrary degree of accuracy. There are, to be sure, untestable philosophical questions which science cannot answer, and it's also true that "an arbitrary degree of accuracy" is not synonymous with "absolute accuracy". But if science can't answer anything, then how is it we're not all still living on nuts and berries? —Steve Summit (talk) 03:42, 27 August 2007 (UTC)
I'm sorry, but I do not know if we are living on nuts and berries. I do not know absolutely and unquestionably that a berry or a nut have ever existed. If you can't realize that science is nothing, and that it doesn't make you know nothing and that no truth comes from it, you are just fooling yourself. A.Z. 03:44, 27 August 2007 (UTC)
Yes, yes, it's fun to play the I-can't-prove-that-all-of-observable-reality-isn't-a-figment-of-my-imagination game. We've all played that game before. But if you want to cure disease or feed the masses or travel faster than you can walk, it's not a useful game to play. The "practical everyday purposes" which you seem to be pooh-poohing are (for practical everyday purposes) the only purposes that matter. Scientific truths may not be isomorphic with philosophical truths, but neither one has a monopoly on the concept of truth.
To A.Z.: This will be my last post in this thread. To everyone else: I apologize for prolonging a philosophical debate on this science desk. —Steve Summit (talk) 03:57, 27 August 2007 (UTC)
I profoundly disagree with you. I'm not playing a game, and I'm sorry you're mocking me. Believing in science is like believing in the Bible. You don't know if there are masses, you don't know if there is food, and that does matter. I feel really sorry to see a question that does matter being mocked here, and philosophers who are just people that don't have a blind faith in science or the Bible being called pathetic. You should admit that no, you don't know if a tree makes a sound or not when it falls, either in the forest or in front of you. I think we should feed the masses and live our practical ignorant everyday life, and I belive there should be science, but I won't pretend to know truths, and pretend I'm not ignorant. A.Z. 04:07, 27 August 2007 (UTC)
Here's the problem for the "nothing can be proven to be real" folks. If nothing were real outside of your thoughts then you could simply cease to interact with this phoney world. So shut off your sensory inputs and just sit inside your mind and all should be well. The trouble is that after you have thought a significant number of thoughts (what we scientists would describe as "a few hours of time passing"), your "fake" sensory devices are going to start making some alarmingly real demands on your thoughts. You'll find that you get sleepy, hungry and thirsty. There is simply no way to shut out those demands no matter how unreal you believe them to be. So whether or not these things are real, you have to act in pretty much every way as if they were. If the demands of food and sleep were illusions brought about by our senses - why are your thoughts so utterly dependent on them? If you go for 48 hours without sleep - you'll find your "inner thoughts" become very hard to keep on track...which would be a surprising thing if the real world were utterly illusionary. So the value of an unprovable (and unfalsifiable) hypothesis such as yours drops to zero within a surprisingly short period of time. The "real world" (as I would prefer to describe it) is 100% compelling - you can't shut it out no matter how hard you try. Time passes in your mind at a rate not too dissimilar to the real world - you can't count to 100 in your head (or think 100 interesting thoughts or...whatever) without at least (say) half a minute or so passing in the real world. Increasingly, we scientists out here in the real world can tell (in the form of various brain scanners) approximately what's going on in your 'inner thought world' - we can see regions of your brain relating to vision light up when you think about pictures and regions related to reasoning light up when you think about math problems. In an increasingly real sense, I can compare what's going on in your mind with what's happening in mine - and find some sharp correlations. So your personal 'inner world' is also increasingly able to be viewed from within my personal 'inner world' - and as far as can be discerned, they work the same way. So what is the point (other than to annoy Steve Summit - which, I agree may be entertaining!) in holding the bizarre view that the outside world is fake and your thoughts are all there is - when the reverse seems to be the only thing that actually works for you? You have absolutely no evidence for the view that your inner world is all that there is and that the real world is faked - yet there is a mountain of evidence that says the opposite. If all of that evidence was out here in the 'real' world - you'd have some grounds for regarding that evidence as illusionary - but it's not - some of the evidence for the existance of a real world exists inside your inner world. Your absolute inability to keep your inner world from turning to thoughts of food, drink, sleep, etc as the real world places demands on it reveals evidence that is totally independent of your senses. Sure the 'feeling' of hunger is a sensory input from your stomach - but if it were illusionary, you could have it not affect your inner world...but you just can't do that. Try this: Try counting to 100,000 in your head without getting hungry. If the world were illusionary, you'd be able to do it...you can't. You just can't. Ergo, the real world is...real. QED. SteveBaker 16:21, 27 August 2007 (UTC)
I fail to see how the fact that I apparently cannot choose not to feel hungry implies that the real world is real. A.Z. 23:55, 1 September 2007 (UTC)
[response to now-deleted prior comment referring to our article on Science]
While the statement, "Science does not and can not produce absolute and unquestionable truth" is certainly true in the context of the philosophy of science, it's profoundly misleading in the context of everyday life. If you've heard that scientific truths aren't absolute, you can easily conclude that (say) biblical truths are just as good as scientific ones. In a way, it'd be really great if we could publicly claim that scientific truths are absolute.
For everyday purposes, saying that scientific truth is not absolute is like saying that falling trees do not produce sound, or that the sky is not blue, or that 1+1=3, or that gasoline doesn't power automobiles, or that heavy objects fall faster than light ones, or that death from cholera is inevitable, or that easy transmutation of lead into gold might be possible tomorrow. —Steve Summit (talk) 03:31, 27 August 2007 (UTC)
But the tree question couldn't care less about everyday life. It's a question about truth, not a ridiculous question about whether your recorder will record something if you place it next to a tree that is about to fall. And, yes, I admit not to have a clue about whether the sky is blue. When I say it's blue, I'm assuming everyone knows that's just for practical everyday purposes. A.Z. 03:38, 27 August 2007 (UTC)
If you take the view that you cannot trust your senses then you have deeper problems. It's not just that you have to doubt that the tree makes a sound - you have to say that the words "tree", "fall", "forest" and "sound" are completely neutral audio signals that your senses are feeding to you with no verifiable meaning whatever. You don't know that you read the question correctly (or at all) or that you did in fact answer it. You don't know whether you are reading what I wrote - you don't even know that anything exists. If that is indeed your belief - then why are you trying to answer this question? In any not-believing-ones-own-senses situation, the question may never have been asked.
The truth is that the question (like everything else we do or say in the real world) is merely shorthand for: "If 'trees' (defined as the following bundle of possibly-illusory sensory inputs....) existed in the way our senses depict them - and if one 'fell' (defined as...) in a manner subsequently seemingly revealed to our senses but not reported directly to our senses at that time..."...and so on for about another four pages. The answer is: "If all of those things were hypothetically true then the answer would be (with many, many more caveats) - Yes!"...which is all you can ever answer about any question on any topic. The point being that you have to understand that the question is wrapped around with all manner of unwritten caveats and assumptions about the real world existing as perceived - and it is implied and understood that your answer should strictly be wrapped in the same unwieldy bundle of linguistic torture. If you accept the question under those terms then the answer is unquestionably "Yes" under those same terms. If you don't accept the question because you refuse to accept those layers of implied meaning then why are you answering it? If the sound of the tree might not exist - then neither might the question be about trees in forests at all - so you can't have a valid answer either way. SteveBaker 18:38, 27 August 2007 (UTC)
Actually in a number of ways you can't trust your senses. I'm not referring on the level of religious zealots who refuse to believe in science but simply that they have numerous limitations and a lot of things things are subjective in ways we often don't realise. I'm not saying this to be contrary and I suspect SB realises this, simply pointing it out for the general reader. Any philosophy of science book is likely useful to get an idea of the limitations of observation, one that I've read before and found good is What is this thing called science? by A.F. Chalmers. Nil Einne 22:34, 27 August 2007 (UTC)
That 1+1=2 is an absolute and unquestionable truth, not discovered by science. A.Z. 03:42, 27 August 2007 (UTC)
I don't know about that. It's (essentially) an axiom built into mathematics - and math (done that way) happens to be useful. But there are other ways that don't come out with that. Suppose you did all of your math in logarithmic domain or perhaps if math were invented by creatures who lived their lives moving at speeds close to the speed of light relative to each other and who learned to add velocities, times and masses using the Lorentz transform: 1c+1c doesn't equal 2c, it equals 1c. Sure they'd have to come up with some new, fancy representation for counting apples - but then we had to go to quite a lot of trouble to bend our math to do relativistic stuff that would come naturally to them. That doesn't make either their or our math 'wrong' - it just doesn't apply. Just as we say that the three angles of a triangle add to 180 degrees - that's not true in a severely warped gravitational field and beings who lived in proximity of a black hole would never have believed what Euclid had to say. It's not entirely obvious that every imaginable culture would see addition of integers as particularly useful. We can imagine beings who can only count to three (one, two, three, many) - who would have an entirely different arithmetic system. 1+1=2 and 1+2=3 but 2+2=many and 2+3=many. Also 2-1=1 but many-1=undefined. You would say that 1-1=0 was also an absolute, unquestionable truth - but the ancient Greeks had an entire system of arithmetic that didn't even contain the concept of zero. You could come up with an entire self-consistent (but not very useful in our world) set of mathematics based around denying our basic rules of arithmetic - in which 1+1=2 would not be quite the slam-dunk you think it is. SteveBaker 18:08, 27 August 2007 (UTC)
Besides, in most axiomatizations of basic arithmetic, 1 + 1 = 2 isn't an axiom (although something closely related, such as 2 = succ(1) in Peano arithmetic, may be taken as the definition of 2). For an example of how one might go about proving it while constructing arithmetic based on axiomatic set theory, see Principia Mathematica#Quotations and particularly this image there. (Ps. What all that old-fashioned set-theoretic notation in the image basically says is that, given two disjoint sets of one member each, their union has two members. Addition is later defined based on the union of sets.) —Ilmari Karonen (talk) 00:23, 29 August 2007 (UTC)
To the Original Poster: the answer to your question is, "yes". (Why do you ask?) —Steve Summit (talk) 02:56, 27 August 2007 (UTC)

The answer is yes. Those kids at the Humanities desk may tell you something different, but here we value objective reality and empirical verifiability. Unless you ask the quantum people, who will likely disagree as to whether the falling tree even hits to ground... Plasticup T/C 03:31, 27 August 2007 (UTC)

Sound of a bong bubbling* *Cough* Wow, like, you guys just totally blew my mind. 24.22.163.169 06:58, 27 August 2007 (UTC)


This requires the true definition of the word "sound" in a way that newer dictionary nolonger use. According to Webster's new international dictionary published 1931 2620 pg. Definition "Sound": 3. To Speak; utter; express "audibly". Now Rare. Definition of audibly which is an adv. form of "Audiblo" its definition is "Audiblo"- Capable of being heard. Not the word capable, as in if present or not present! key. it will be capable of being heard., it is capable of being heard even if no one there. Key word capable so it someone happens to be there it can be heard but does not require someone to be there, then it would be heard, not just capable.... Sound waves being produced,, case solved!!! Q.E.D. --Aaron hart 09:50, 27 August 2007 (UTC) so the ansuer is yes no matter how you twist your modern definitions......

Like in any debate, the person who defines the terms wins the argument. -- JSBillings 10:22, 27 August 2007 (UTC)

Answer=yes.87.102.45.106 13:19, 27 August 2007 (UTC)

Crack a tree, leave a tape recorder near it, and wait until it falls. Then listen to the tape to see if it made a sound.

How do you demolish a skyscraper?[edit]

What is the normal non-terrorism way to demolish a skyscraper? Mapper of the streets 22:54, 26 August 2007 (UTC)

Tall buildings are typically demolished using excavators. Controlled implosion has been used on buildings ~40 stories tall, although the danger and environmental hazards make this a non-prefered method of doing it (and this would imaginably be impossible in sufficiently dense urban areas). The tallest building ever demolished (not by terrorists) was only 47 stories tall. See also, demolition, high-reach excavator. Someguy1221 23:13, 26 August 2007 (UTC)
Explosives are planted in the base of the tower and then the tower falls vertically rather than on its side. It takes a lot of planning to get a tower to fall vertically. Juanita Hodges 23:25, 26 August 2007 (UTC)
Occasionally, buildings are dismantled piece by piece, in sort of the reverse order they were built. I watched this being done to the top floor or two of a building in Seattle that was being remodeled, and the same thing is currently and notably being done to the damaged Deutsche Bank building next to the WTC site. Presumably manual dismantling is more timeconsuming, more expensive, but less disruptive than either explosive demolition or excavator demolition. —Steve Summit (talk) 02:55, 27 August 2007 (UTC)
It is also noticeably less exciting. Plasticup T/C 03:33, 27 August 2007 (UTC)
Well, except for a couple of recent incidents at the Deutsche Bank building. :-( —Steve Summit (talk) 03:37, 27 August 2007 (UTC)
You can find a very good article on building_implosion at [1] -- WikiCheng | Talk 04:11, 27 August 2007 (UTC)
If you're (understandably) worried about the building falling to its side during demolition, think about the New York WTC (the terrorist thing you refer too, I presume). Both those towers fell straight down, despite the fact that they had been hit violently in the side. I can imagine that skyscrapers are even designed to fall like that if explosive demolition is so much cheaper than excavator demolition. Btw, funny that you specify non-terrorist. Loads of skycrapers must have been demolished (makes me wonder - how many?) and only once by terrorists. But the images have been repeated on tv so often that indeed I also instantly thought of the New York WTC when I read the header. We've been brainwashed. :) DirkvdM 07:13, 27 August 2007 (UTC)
A lot of people say there were explosives planted in the twin towers and people heard explosions at the base of the towers, too. Juanita Hodges 11:05, 27 August 2007 (UTC)
That would of course be the controlled demolition hypothesis. Worth noting is that – aside from a tiny minority of conspiracy theorists – it is widely acknowledged as bunk. Beware the 'major events must have major causes' trap in human psychology: [2]. TenOfAllTrades(talk) 13:27, 27 August 2007 (UTC)

You might enjoy David Macaulay's book Unbuilding, in which he descrbes the hypothetical dismanteling of the Empire State Building.

Atlant 12:00, 27 August 2007 (UTC)

The lesson the twin towers does bring is how relatively easy it is to bring buildings down more or less vertically. In that case, both essentially unplanned collapses happened fairly close to vertically. Demolition experts who are trying to achieve this kind of effect ought to be able to produce it on demand. One wonders how much thought about the ultimate demolition of the building goes into the original design process. Are architects inadvertantly making buildings that are going to be costly to demolish when the time comes? SteveBaker 15:49, 27 August 2007 (UTC)
Don't mean to brag, but I already said that. :) DirkvdM 19:09, 28 August 2007 (UTC)
Twin towers spilled debris out all over the place, presented a major health hazard, and rained concrete on the city. I doubt it is a good model for how things ought to work, demolition-wise. It superficially came straight down (under the massive weight of the top bits of it) but it was nowhere near a model for a safe demolition, and if you look at the footage/pictures you can see that there is a tremendous plume of materials as the buildings comes down (i.e. Image:South WTC Collapse.jpg). --24.147.86.187 18:22, 27 August 2007 (UTC)
Ok, so I definitely wasn't bragging. :)
A way to prevent this debris-damage is to make the building sag in the middle first, so the outer walls collapse inwards. Don't know how well this would work for skyscrapers, though.
But this brings me to a reply to TenOfAllTrades: A respectable Dutch tv programme, Zembla, debunked a lot of those 'conspiracy stories', but when they showed the film of the imploding adjacent CIA building (which was much smaller) to the major Dutch demolitioner he instantly said that that was without a doubt a controlled demolition job - it sagged in middle first, just the way demolitioners do it, and that couldn't possibly have happened in an uncontrolled collapse. Which fits in with the idea that the CIA knew about the attacks beforehand and decided this provided them with a nice excuse to 'counterattack' 'rogue states'. The collapse of their own building supposedly got rid of evidence. It was also oddly already evacuated before there was sufficient reason to do so. And after it became apparent that there was something wrong with those flights, normal procedure was not followed - they should have been instantly intercepted, but were left free to finish their 'job'. And there's more evidence pointing that way, I believe. DirkvdM 19:09, 28 August 2007 (UTC)
Btw, all references to this appear to have been removed from Wikipedia. They used to be somewhere, but I can't find them anymore. All there is is debunking of controlled demolition of the twin towers, but that's not the main issue, as I understand it. I wouldn't be surprised if the CIA started those stories themselves - create a lot of confusion with bull stories to distract from the real issue. DirkvdM 19:21, 28 August 2007 (UTC)