Wikipedia:Reference desk/Archives/Science/2006 August 29

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A Plant

• 
  Smallest one
• 
  Largest one, the color is not right in this picture
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  Leaves

I saw this plant by a roadside in Eastern US. The flowers aren't opened yet but look like unopened Dandelion Flowers, maybe a little bit bigger. I saw six or seven, the smallest one was half way to my knee, the largest was up to my shoulders. The biggest leaves were longer than my foot. They were soft and smooth. Where is the right place to this question? Thanks! Flyflyfly 00:01, 29 August 2006 (UTC)

This is probably the right place for the question, but what exactly is the question ? Let me take a guess: "Will this plant shoot spores into my face and make me forget all my responsibilities, while I experience pure joy ?" :-) StuRat 03:15, 29 August 2006 (UTC)

What is the plant? Flyflyfly 13:39, 29 August 2006 (UTC)

It looks like a biennial - the sort of plant that spends 1st year growing flat and 2nd year growing tall & flowering - but I could be wrong.

It can be difficult to identify a plant from photos - you normally need to examine the plant in detail. Best way is with a flora with a key (simple qs - like 'does plant have simple or compound leaves?'). Buy a flora or maybe these can help. Rentwa 13:58, 29 August 2006 (UTC)

Antacid

Can one take too many antacid tablets and cause damage to the stomach? Can lack of acid in the stomach cause damage to the stomach (I didn't take any antacids, by the way)? --Shanedidona 00:07, 29 August 2006 (UTC)

Antacids typically contain very mild bases; they shouldn't damage the stomach even if taken to excess. In principle, a massive overdose of antacids may cause alkalosis: an increase in blood pH to unhealthy levels. If you find that you're taking antacids over a long period of time – weeks – then you might want to consult your physician; you may have a stomach ulcer or other medical problem that requires attention. TenOfAllTrades(talk) 01:13, 29 August 2006 (UTC)

I would think a lack of acid would slow down digestion, and perhaps make it less effective. StuRat 03:08, 29 August 2006 (UTC)

Stomach acid is not for digestion, it is to kill any foreign bodies (eg. bacteria etc.) that might be inhabiting your food, enzymes are used for digestion. Low stomach pH causes an increasedrisk of infection, which can be fatal is maintained at a low state, providing infection. Philc _T^E_C^I 12:48, 29 August 2006 (UTC)

Don't you mean high stomach pH (i.e., less acid)? —Keenan Pepper 03:55, 30 August 2006 (UTC)

If your stomach had no acid in it, would that hurt? --Shanedidona 03:47, 29 August 2006 (UTC)

Its hard to say. What happens if you eat lots of mild alkali-- does that hurt?--Light current 04:07, 29 August 2006 (UTC)

We have an investigation into antacids as a Yr 9 (13-14-year-olds) project for our pupils. The actual amount of base per tablet is minute, and cannot possibly neutralise all the acid in the stomach. Rather, the conclusion is that they are intended to neutralise excess acid above the sphincter, and thus reduce discomfort. Also, the slower they dissolve, and the slower they slip down, the more effective they are. --G N Frykman 11:26, 29 August 2006 (UTC)

Be careful about prescription medicatons. Certain ones (I don't know off hand which) require stomach acid to function properly. Lowered stomach acids due to antacids can cause the drugs to become ineffective, or may even result in potentially severe side effects. -- 14:49, 29 August 2006 (UTC)

Also, this isn't related to the stomach, but overuse of antacid products (Enos and baking soda more than antacid pills) can negatively impact heart function, due to the mineral salts' altering electrolyte levels. Anchoress 14:53, 29 August 2006 (UTC)

Excellent

I don't have a question--I want to pass on congratulations. I looked up Pluto on your site and was very happy to see that the information has just been updated. So often websites are created and never refreshed and kept up to date. You are doing a wonderful job. Thank you.

On behalf of our astronomy editors, thank you for your kind words. Rockpocket 01:51, 29 August 2006 (UTC)

You could count on seeing it updated within an hour of the decision. When the bombs went off in Bombay, I went straight to Wikipedia for the true, clear, concise information all in one place — [Mac Davis] (talk) (Desk|Help me improve)

Looks like you need to update your knowledge base, Bombay is now Mumbai. :-) StuRat 03:10, 29 August 2006 (UTC)

So do terrorists in Mumbai now explode "mumbs?"Edison 15:28, 29 August 2006 (UTC)

Another one of the goodies of Wikipedia - if you go to Bombay you automatically end up in Mumbai. DirkvdM 09:46, 29 August 2006 (UTC)

And if you've a date in Constantinople, she'll be waiting in Istanbul. Melchoir 14:35, 29 August 2006 (UTC)

And, with my luck, I'd be stuck in Byzantium. :-) StuRat 23:33, 29 August 2006 (UTC)

Seagulls!

Can someone please explain to me why the Science RefDesk is so devoted to every possible aspect of seagulls? Once you're at it, are seagulls Hallal? Loomis 03:25, 29 August 2006 (UTC)

I thought we had banned them last week.--Light current 04:00, 29 August 2006 (UTC)

Followup question

How long can a joke go before it stops being funny? This is not homework. – ClockworkSoul 04:13, 29 August 2006 (UTC)

Who knows? Raul654 04:31, 29 August 2006 (UTC)

Bonus question: Arrange these six seagulls into one arrow. Anchoress 07:26, 29 August 2006 (UTC)

That's a trick question, they're already in an arrow. - Mgm|^(talk) 08:26, 29 August 2006 (UTC)

Which dance is the one in the front doing? DirkvdM 09:49, 29 August 2006 (UTC)

THe funky chicken?--Light current 15:08, 29 August 2006 (UTC)

He's not dancing, he's got gum stuck to the bottom of his foot. Oops, no, on further examination, he stepped in some guano. Anchoress 14:39, 29 August 2006 (UTC)

From now on, I'm not going to even bother to archive the seagull related questions anymore (: That should save a few hours of my time--VectorPotential^{71.247.243.173} 15:12, 29 August 2006 (UTC)

It is mostly User:Kurt_Shaped_Box's idea. He is constantly asking questions about seagulls bagels and catfish. — [Mac Davis] (talk) (Desk|Help me improve)

Do catfish masturbate? – ClockworkSoul 19:44, 29 August 2006 (UTC)

In Kurt Shaped Box's defense, I have observed him asking only serious questions about seagulls. Melchoir 06:07, 30 August 2006 (UTC)

In the seagulls' defense, I don't think I've ever observed them doing anything that deserved a banning.  freshofftheufoΓΛĿЌ  14:50, 30 August 2006 (UTC)

War-plane crash

Hi! which kind of war-plane has the highest frequency of crashing down ...NOT due to enemy-attack, but 'cause of technical-failure ? Also, what is the commonest technical problem that leads to a war-plane crash(in general) ?? --Pupunwiki 04:05, 29 August 2006 (UTC)

Probably some helicopter. Melchoir 04:09, 29 August 2006 (UTC)

I would guess that would be a plane with few production models, like the V-22 Osprey. StuRat 05:41, 29 August 2006 (UTC)

I would guess the reverse, if you only look at the total frequency (not the average per plane). DirkvdM 09:51, 29 August 2006 (UTC)

The most common cause is probably engine failure. Engines aren't designed to run at full power for long periods of time, but because of the speed required for dogfighting, and the power required for a bomber to take off with a full load, warplane engines are overstressed on a regular basis.

As for individual models, a number of World War I aircraft had problems with aerodynamic instability, where a pilot could easily find himself in a flat spin or other uncontrollable situation. In World War II, the B-26 Marauder had a reputation for crashing if an engine failed on takeoff. --Serie 23:08, 1 September 2006 (UTC)

I vaguely remember hearing of some Fokker, German, 1920's or 1930's, called a "widowmaker"; less than a hundred were made, and two-thirds of the pilots were killed. Google knows naught, though. linas 23:11, 2 September 2006 (UTC)

Optimal slope

This is not a homework!

If you are making a zigzagging road as on this picture from Machu Picchu [1] what is the optimal slope so that it requires the least amount of energy to walk to the top. I have thought about this that it is the same as the optimal slope of a ramp to elevate yourself to a given height without the zigzaggings and does not depend on the slope of the mountain. If we have a formula that gives the energy E(α) required by average person to walk up a slope at the angle α per meter of gained elevation then we want to minimize E(α). When α goes to zero this goes to infinity and when α goes to a right angle it will also go to infinity. Is this my reasoning correct? Are there formulae or tables for E(α)? Also I think the optimal slope may be different for bicycles and cars, is that slope known? Thank you for your attention. 199.3.224.3 07:11, 29 August 2006 (UTC)

For this to be realistic you'd have to calculate in the soil and the person. With a sturdy surface a steeper angle would proabably be more efficient. And I have walked up hill-tracks that were obviously built with less fit people in mind, with a very shallow slope. I tend to ignore them and go straight up. Then again, this may just 'feel' less tiring because the track is so boring. DirkvdM 10:51, 29 August 2006 (UTC)

(via edit conflict) In an ideal situation (negligible friction, etc), the energy required to raise a mass by a height of h is mgh, and is independent of the path taken, so in that case there is no optimum, and in fact the only problem case is if the angle is zero, when you will never reach the top and hence never expend any energy. On the other hand, the fastest comfortable angle is probably something like 30° or so (I seem to recall that's around the maximum grade for roads and such), but I don't know of any references or reasoning for that. Confusing Manifestation 10:53, 29 August 2006 (UTC)

Thats not true, you seemed to have failed to account for the fact moving uses energy. The optimal slope would be a straight line to the top at 90 degrees, that way you move the load the minimum distance, but the same height. Philc _T^E_C^I 12:44, 29 August 2006 (UTC)

Yes, but that energy can (in theory) be recovered at the end. The only energy that has to be used up is that which is converted into gravitational potential, which is independent of the path taken. EdC 17:03, 29 August 2006 (UTC)

Let's assume a paved road. Having hiked and negotiated some slopes, I can assure you that climbing at a steep angle uses up a lot more energy for the same height difference. And going downhill at a steep angle kills you. I found an online article claiming that for going uphill a slope of 15° is best, and for downhill 10°.[2] But no formulas or actual data of energy expenditure for different slopes. --Lambiam^Talk 18:30, 29 August 2006 (UTC)

THe potential energy at the top is independent of the route taken. So whats the real question?--Light current 19:52, 29 August 2006 (UTC)

Have you heard of metabolism? Animals (including humans) expend energy to move their muscles. That energy is not waiting for them at the top of the mountain to be reclaimed. It is lost, gone, pfft. --Lambiam^Talk 20:12, 29 August 2006 (UTC)

The HP ScanJet 4600 Flatbed Scanner

• http://reviews.digitaltrends.com/review_printerfriendly1694.html

How does it work? Where is its sensor array? -- Toytoy 08:21, 29 August 2006 (UTC)

same way as any other i'd say. the array will be on a track, and will currently be inside the casing, and will be dragged across when scanniong starts. Xcomradex 08:43, 29 August 2006 (UTC)

From the review: "The see-through window is a nice touch, as it is somewhat mesmerizing to watch the glowing scanner carriage work its way down your document." Normal scanner, though at 3 lb it probably uses an LCD array for its light source (which makes it a lot lighter than the bulb scanners). It just seems to not have an opaque cover. I wonder if that creates problems in certain types of environments—I've noticed that with my scanner if I try to use it with the cover open in a very sunny environment it can have a more washed-out feel on the colors, though I don't know if that is just me imagining things or not. --Fastfission 15:38, 29 August 2006 (UTC)

Intubation for blocked tear duct

--Fayray 13:05, 29 August 2006 (UTC)would like to know the risk factors and percentage success rate for this surgical procedure. If it is not successful, is the patient likely to be worse off than before undergoing the operation?Fayray 13:05, 29 August 2006 (UTC)

If this is a real and not hypothetical case your doctor will unquestionably be better placed to answer this question than Wikipedia. DJ Clayworth 15:23, 29 August 2006 (UTC)

My grandmother underwent what would likely be the procedure you're referring to, and that went well. :-) I know the sample size isn't too great but it's better than nothing. —Bromskloss 15:56, 29 August 2006 (UTC)

pH meter and buffer solutions

Why doesnt a pH meter work in a weakly buffered solution?

they do work. pH meter. Xcomradex 00:08, 30 August 2006 (UTC)

• If you calibrated the thing properly using at least 2 (preferably 3) standard buffer solutions, it should.- Mgm|^(talk) 07:48, 30 August 2006 (UTC)

Some pH electrodes have trouble with very low ionic strength solutions. There are electrodes on the market that are better designed to deal with this (I think mine is a STAR electrode from Fisher). ike9898 13:39, 30 August 2006 (UTC)

Movement

Why does movements create heat? Correct me if I'm wrong and please explain! Thanks!

Movement only creates heat where there is friction. An object moving thru a vacuum doesn't create heat. StuRat 13:42, 29 August 2006 (UTC)

But an object moving along the ground, or through air or water, does. So why does friction create heat? As you can read in the friction article, according to the law of conservation of energy, no energy can be lost when friction slows something down. The energy is therefore transformed into heat.--Shantavira 14:26, 29 August 2006 (UTC)

Perhaps because bonds are being formed and broken between the two objects as they move against each other, and energy is required to break the bonds? (Chemist's answer) Rentwa 20:15, 29 August 2006 (UTC)

The elevator broke

Hi,

An old physics question. A person is standing in an elevator on the 30th floor of a building holding a tennis ball. The chain/rope of the stationary elevator cracks and it starts falling down under free gravity. At that moment he releases the ball. Do you think the ball will hit the flor of the elevator before the elevator hits the ground 30 floors below?

Namit.

The old physics answer - No. If we assume there are no forces on the elevator or ball (such as friction or air resistance) both are under free fall, and are subject to just the force of gravity, and thus the same net acceleration. If we assume that both the elevator and ball start at rest, their downward velocities will always match, and will always track each other's position, ending up at the floor at the same time. -- 15:05, 29 August 2006 (UTC)

However, when we throw in air resistance, I expect the answer is "yes". I think the elevator is more likely to reach terminal velocity, as the tennis ball is falling through air that is (to some degree) also falling with the elevator. Less relative velocity should result in less drag on the ball. — Lomn | Talk 15:12, 29 August 2006 (UTC)

Man, why is physics so macabre? --Fastfission 15:16, 29 August 2006 (UTC)

This sounds like a homework, but I cannot know that so I'll give you the benefit of the doubt. My reasoning will be divided into the following parts:

1. Will the ball fall faster than the elevator? (Answer: Yes)
2. Will the ball fall so much faster than the elevator so that it will hit the floor before the elevator hits the ground? (Answer: I would guess so.)

Let's start with question 1. My personal experience tells me that the shaft is not an awful lot wider than the cage that moves in it. This means that as the cage falls downward and pushes the air under it aside, this air will have to squeeze through the rather narrow space between the cage and the shaft wall. By consequence, the speed of the cage will be slow compared to what it would be in empty space. The ball will of course not have much of this problem. Furthermore, since the air inside the cage will move at the speed of the cage (and thus nearly the speed of the ball), the ball will have a low speed relative to the air around it and will therefore not experience as much drag as the cage itself would, even if the latter wasn't confined to a shaft.

Now, to answer question 2, we need to know not only that the ball falls faster than the elevator, but how much faster and how long it will take before the cage is down. Well, I can't answer that, but intuitively, I would say Yes, I think the ball hits the floor before the cage hits the ground. —Bromskloss 15:20, 29 August 2006 (UTC)

I was actually thinking about falling elevators earlier today and wondered if they could be used for simulated weightlessness! :-) (I know you want it, everyone does, right?) You would need a high building for it to be any fun, and perhaps actively pushing the elevator downward (or even without actively pushing it, you might achieve moon like gravity). It could perhaps be cheaper than parabolic flight, don't you think? —Bromskloss 15:33, 29 August 2006 (UTC)

To nitpick: if the elevator is of a post-1857 design. it should have something like the Otis safety device which automatically applies brakes if the cable breaks, thriller movies notwithstanding. Edison 15:34, 29 August 2006 (UTC)

Real physicists use pre–1857 elevators! —Bromskloss 15:40, 29 August 2006 (UTC)

Theoretically, as soon as the cables of the elevator are snapped, the ball will start falling with the same acceleration as the elevator. In relation to the person, the ball will be at the same height as tht when the person drops it. This is a clear cut case of weightlessness. Now as soon as the elevator hits the ground , the ball shall take normal time as on land to hit the ground. Practically, taking air resistance into consideration, the speed of the elevator will reduce and thus also its acceleration. This will cause a disbalance in the acceleration of the ball and the elevator. And thus the ball will hit the ground before the elevator hits the ground.

Also, remember Galileo's Ecperiment frm the top of the Leaning tower of Pisa. When two objects are dropped frm a common height, they land in the same time duration. User : Veda, Sanchit

On the moon (without the air), you can even do it with a feather and a hammer. :-) —Bromskloss 16:58, 29 August 2006 (UTC)

Alarms during a thunderstorm

Why do car / house alarms activate during a thunderstorm? Someone told me that the static in the air sets them off but other electronic devices seem to work fine. 62.25.109.194 15:23, 29 August 2006 (UTC)

theyre not properly designed for EMC electromagnetic compatibility--Light current 15:28, 29 August 2006 (UTC)

Vibration of the house windows or of the car might set off the sensors. As noted above, the electrical field from the lightning, or electrical fields induced in the power circuits might trigger the alarm. Utility electric power may be momentarily switched off and back on by the utility high voltage lines to clear fault conditions when lightning strikes power lines, and some alarms may be set off by the power being removed and restored, especially if the alarm backup batteries are worn out. Edison 15:38, 29 August 2006 (UTC)

Or basically, they are too sensitive to unimportant thinks (a bit like some WP editors)--Light current 15:46, 29 August 2006 (UTC)

You're going to get yourself in trouble again! — [Mac Davis] (talk) (Desk|Help me improve)

This is not a personal attack! Also I include myself in that bracket) 8-)--Light current 19:39, 29 August 2006 (UTC)

Ah, but aren't you a person? Or me, who would like to point out that you don't indent properly? DirkvdM 09:04, 30 August 2006 (UTC)

How does that explain why car alarms go off for fireworks?  freshofftheufoΓΛĿЌ  13:13, 1 September 2006 (UTC)

Oversensitive door alarm. When a firework explosion shakes the car, it opens the door just a crack, and some car alarms interpret that as an attempt to break in. --Serie 23:25, 1 September 2006 (UTC)

shackle poisoning

Hello,

I was wondering what shackle poisoning is. I've heard that it is the constant rubbing of chains on peoples legs, mostly on chaingangs. I was just wondering what exactly it is and why does it kill people.

Thank you.

--Jerry

If you Google for it, you will find that the term only appears in two main instances - both authored by the same man, Wayne Perryman. It is possible that he is giving a term to this problem that nobody else uses. It is highly unlikely that shackles poison anyone. It is more likely that they have open wounds that get infected. --Kainaw ^(talk) 17:56, 29 August 2006 (UTC)

A hypothetical question about teleporters.

In films such as The Fly, teleporters work by 1. Identifying each individual cell in the body of the traveller; 2. Destroying the body of the traveller; 3. Transmitting the data to another machine and 4. Reproducing each individual cell in the precise order they were in earlier. To me, it seems that rather than teleporting a person from one place to another, they've just killed the person and replaced them with a clone. Thoughts? Corrections? Wouldn't this be the ideal way to commit suicide, as your consciousness ends but your family and friends are unaware of any change? Pesapluvo 17:16, 29 August 2006 (UTC)

If you believe that life and consciousness are solely a manifestation of a collection of physical, chemical and electrical processes, and those processes continue unabated after being teleported, then I think it follows naturally that your life continues. If you believe that life is more than a mere manifestation of material properties, as many people do, then I think that the answer would have more to do with faith than with science. Dragons flight 17:24, 29 August 2006 (UTC)

Yes, if you have sufficiently detailed knowledge of what you were teleporting, you can recreate the same thing at any other point in space. No need to destroy the original, but then there would be 2 copies of you. A better idea would be to create a wormhole between the 2 locations. The two locations then effectively become one and you can just walk thro it (intact)--Light current 17:28, 29 August 2006 (UTC)

In quantum teleportation you must destroy the original. — [Mac Davis] (talk) (Desk|Help me improve)

You mean to read some thing properly you must interfere with it to a destructive extent? Yes that could be right. That of course is what happens on WP! 8-)--Light current 19:36, 29 August 2006 (UTC)

There is also the problem of multi-dimensional existense. Sure, we know how we appear in 3 dimensions. How do we know there isn't some fourth or fifth dimensional extension of our being that, if we copy just the 3 dimensional view, is missing? That must be included in Light Current's "sufficiently detailed knowledge" disclaimer. --Kainaw ^(talk) 17:51, 29 August 2006 (UTC)

Yes I suppose it must but I think Im happy with my 3 dimensions ATM--Light current 18:42, 29 August 2006 (UTC)

This is a problem in what's called personal identity. In general, to answer this question, one must decide what makes one person the same person at two different times. For instance, what is it about me circa 2006 that makes me the same as me in 1995, but not the same as my father in 1995 (or anyone else for that matter)? Much of my constituent matter is different between the two times, but that doesn't seem to matter in personal identity. If your interested, the Stanford encyclopedia of philosophy article may provide some additional food for thought. --best, kevin [kzollman][talk] 19:30, 29 August 2006 (UTC)

Re personal identity: Assuming it's made possible by the progress of medical science, would you have a brain transplant when your brain fails? --Lambiam^Talk 20:20, 29 August 2006 (UTC)

I would have a body transplant instead! (before the brain failed)--Light current 20:31, 29 August 2006 (UTC)

The Emperor's New Mind is an interesting and accessable book with lots of speculation on this very question. MeltBanana 01:13, 30 August 2006 (UTC)

Another problem with this in Star Trek is that if it is just the transmission of information, then distance should be no problem, so why do they need spaceships? DirkvdM 09:11, 30 August 2006 (UTC)

The biggest problem in Star Trek was that they didn't require a station at the other end to reassemble the person. I would have made the Enterprise and other ships have the primary purpose of setting up transporter stations on other worlds. This would naturally have put them on the edge of the explored universe, so they still would have had a chance to encounter new life forms and green women, thus giving Kirk an opportunity to unzip his boots, among other things. :-) StuRat 20:45, 30 August 2006 (UTC)

I H8 EndNote

Does anyone else have problems using EndNote to search for references from the PubMed database? It's always saying that it can't find any results even though I'll eventually find exactly what I'm looking for using different search parameters, despite the thing I'm looking for matching the parameters I originally used. It's rubbish. --Username132 (talk) 17:53, 29 August 2006 (UTC)

I just use Entrez Pubmed at NCBI. Xcomradex 00:11, 30 August 2006 (UTC)

I've used EndNote for years, but I NEVER use EndNote to search for new references I don't already have. You are right, it is buggy and clunky, so I recommend just searching Pub Med directly as the last respondant suggested. ike9898 13:34, 30 August 2006 (UTC)

Hyperventilation

I read in a science book that some people think that hyperventilating will help them hold their breath longer, but really this doesn't help at all and might be dangerous. I was just wondering; if hyperventilating doesn't help you hold your breath, what does? What are you supposed to do in order to hold your breath longer? The hyperventilation article doesn't say anything about holding your breath. --Jonathan ^talk 18:17, 29 August 2006 (UTC)

Stopping breathing (or death). THe first sometimes leads to the second-- or vice versa--Light current 18:43, 29 August 2006 (UTC)

If you want to be able to hold your breath for longer, practice holding your breath. That's how the insane deep-sea divers do it. Would doing a lot of cardiovascular exercise help too? — [Mac Davis] (talk) (Desk|Help me improve)

The excersize I used when I was young (which worked well) was to breath out as much as you can, then blow out three more times. Then, breath in as much as you can, then gasp in three more times. Repeat. It doesn't only allow you to hold your breath for a long time, it also allows you to blow air (ie: through a trumpet or saxophone) for much longer. --Kainaw ^(talk) 19:00, 29 August 2006 (UTC)

I've actually been trying to train my lungs for swimming purposes. Should I hold my breath in/out for any length of time or is it good enough to just do the inhaling and exhaling?  freshofftheufoΓΛĿЌ  14:40, 30 August 2006 (UTC)

Yeah just tried that!. I think this would increase lung capacity and would therefore help to hold breath longer.--Light current 19:28, 29 August 2006 (UTC)

Regularly playing a wind instrument also increases your lung capacity and your ability to hold your breath. --Lambiam^Talk 20:24, 29 August 2006 (UTC)

I think you might be interested in reading Shallow_water_blackout, which was conveniently linked to at the very bottom of the hyperventilation article. --Borbrav 20:30, 29 August 2006 (UTC)

Yeah, thanks, that's just the article I needed. --Jonathan ^talk 23:47, 29 August 2006 (UTC)

Pardon the original research but in my youth I worked at breath holding, reaching a personal best of 3 minutes 45 seconds. There is no question, based on my experiments, that hyperventilating prior to breath holding extends the time one can hold the breath without passing out. Michael Faraday, the 19th century chemist and physicist, working with Humphrey Davy first isolated several gases and did much work in labs where lethal gases were sometimes produced. He wrote an experimental note in one of his books to the effect that if one wishes to rescue a person who has passed out in an atmosphere dangerous to life, it is a good idea to take several deep breaths before dashing into the room and pulling out the person who has passed out, being careful not to breathe in the noxious atmosphere. He noted that he had used the technique a number of times. As always, seek medical advice before trying anything you read about on Wikipedia. Edison 03:46, 30 August 2006 (UTC)

The urge to breathe typically comes from the elevated carbon dioxide which accumulates when you are not breathing. When you hyperventilate, you bring your carbon dioxide down to quite a low level. Therefore, it has a longer way to go to get to the level where you feel the extreme urge to breathe. Surprisingly enough, low oxygen is a much less potent stimulus to breathe. This is why hyperventilation allows you to hold your breath longer. InvictaHOG 08:39, 30 August 2006 (UTC)

Destructive interference, audio?

Let's say two guys talk at the same time. One guy is talking in completely the inverse phase of what the other is, so that in theory, the audiowave peaks where the other audiowave reaches its bottom. Realistic restrictions part aside, would the two guys cause the sound to disappear at some place? Thanks! Henning 19:18, 29 August 2006 (UTC)

Yes. It happens here quite often!--Light current 19:25, 29 August 2006 (UTC)

Destructive interference is essentially what noise-cancelling headphones are designed to create. -- Scientizzle 00:22, 30 August 2006 (UTC)

If two points are generating inverse waves, then in 3d space, at some points they will destructively interfere (producing no sound), and at other points the overlap will produce contructive interference that will double the sound intensity. Raul654 00:23, 30 August 2006 (UTC)

To try this experimentally, one might take a monophonic recording, and reverse the leads to one of the 2 speakers. Then move along a line equidistant from the line connecting the speakers, perhaps plugging one ear, and se if there is a point where the sound in at a minimum. Edison 03:49, 30 August 2006 (UTC)

Pseudoscience

I know that Pseudoscience makes claims that its predictions are supported by experimental evidence. However, a pseudoscience concept put forth fails under the rigors of experimental testing within the framework of the scientific method. Often the methods of testing, data collection, and conclusions are flawed by a preconceived agenda. Can you give me an example of a pseudoscience concept or product and an explanation why it is based on false science or logic. I know alittle about this but not enough to give my son the right logic for his studies. THANKS

What about divining, seance, astrology to start.--Light current 21:13, 29 August 2006 (UTC)

Creation Science is one of the worst offenders. I have absolutely nothing bad to say about Christianity or Christians, but Creation Scientists come up with some of the most inexplicable, nonsensical garbage I've ever heard labeled as science. For example, one popular creation science theory says that the reason lizards grew so big (into dinosaurs) was because there was a shell of solid ice around the entire earth protecting them from harmful UV radiation. And that the rain for The Flood came from God melting the ice. Not only would such a construct be completely unstable (hasn't anyone read The Ringworld Engineers?), but it wouldn't do squat to raise O2 levels or make dinosaurs. --Froth 21:18, 29 August 2006 (UTC)

There is a list in our article on pseudoscience. Phrenology is always a popular example, and less controversial than creation science. It was generally considered bad because the practitioners often changed their predictions when they were falsified. I remember hearing about one case where they examined Rene Descartes skull and found that phrenology predicted he would be dumb. In response the phrenologists downplayed Descartes contributions rather than reject their theory. The last days of phlogiston chemistry are like this too. Phlogiston was a substance that supposedly left an object when it was burned. When experiments demonstrated that objects gained weight when burned, phlogiston chemists suggested that perhaps phlogiston had negative weight.

Often times, pseudoscience is so labeled because their claims are not falsifiable. That is, no experiment can ever disprove them. Conspiracy theories often fall into this category: "There is a government conspiracy. Anyone who tells you there isn't is just part of it." There is some debate in the philosophy of science over whether falsifiability is an appropriate criterion, however. If your interested, see Demarcation problem. --best, kevin [kzollman][talk] 21:40, 29 August 2006 (UTC)

I would include chiropractic, as terms like subluxation are vague and are used to diagnose and treat just about any condition, without any actual evidence. StuRat 22:27, 29 August 2006 (UTC)

I would add that the word itelf, subluxation, has a well defined meaning in medicine (it refers to a partially dislocated joint or eye). It is only in certain contexts that this word has an alleged vague meaning.Tuckerekcut 13:36, 30 August 2006 (UTC)

Alex Chiu's 'eternal life through the power of magnets' theory springs immediately to mind. --Kurt Shaped Box 02:54, 30 August 2006 (UTC)

String theory was recently criticized as non-falsifiable, but Brian Greene is extremely smart and he is a proponent of it so what can you do. Edison 03:52, 30 August 2006 (UTC)

Some suggest psychiatry is non-falsifiable and thus a pseudoscience (demarkation problems notwithstanding), see Anti-psychiatry and Biopsychiatry controversy for more information. Rockpocket 05:11, 30 August 2006 (UTC)

According to Karl Popper, psychoanalysis is non-scientific because it is not based on falsifiable hypotheses. However, I don't think he felt the same way about psychiatry in general. He did criticize Marxism along the same lines. Bhumiya (said/done) 05:12, 5 September 2006 (UTC)

Closed universe theory / edge of the universe

If it's correct, what will happen when expansion slows to a halt and starts contracting? For that matter, what will the universe look like when expansion slows enough to see light from the very edge of the universe?

Also, since the universe is expanding at only very nearly the speed of light (and not the speed of light), what is happening to those few photons that overtake the "edge"? Is that energy lost from the universe? Or is the expansion of the universe expansion through time, not space? I'm very unclear on this.

And if the universe starts contracting, what will happen? Will cohesive masses get smushed together (the galaxy being pulled into a gigantic quadrillion-galaxy ball of plasma in the center of the universe for example) or would atoms just get closer or something (us relativistic creatures never noticing until microcircuitry -and brains- stop working from the interference)?

--Froth 20:50, 29 August 2006 (UTC)

I believe we can already see light from the edge of the universe!. Also, its only the farthermost stars that are travelling fast according to Hubble's Law.--Light current 21:16, 29 August 2006 (UTC)

I know that only the farthest systems are travelling fast, what does that have to do with my question? After thinking about it some more, I think maybe I have a flaw in my first question- I had been thinking of the universe as a defined line, like the edge of an expanding sphere, with stars drifting into this newly-opened space at some later point, with the "edge" roaring onward, claiming more volume for the universe. But I guess what's really going on is that the "size" of the universe is defined by the presence of matter streaming outwards from the big bang- in other words that stars and photons and neutrinos can just move outward as far as they want -even if they were to suddenly jump a trillion light-eons forward- and just keep encountering space.. nothingness. Or was I right originally, and the presence of energy or matter "unlocks" space in a way, and with the first change that.. that location has ever experienced initiates the flow of time there and so the universe barrier isn't just arbitrary, it's real and measurable. I know I'm twisting words a little, especially with time -that is what time really means anyway, measurable change- but I'd be interested if there are any real scientifikal theereez on this topic. I don't subscribe to the theory of the big bang btw, im just curious about it --Froth 21:28, 29 August 2006 (UTC)

Yeah-- theres no 'space' w/o mass--Light current 21:31, 29 August 2006 (UTC)

Partial answers/comments: Keep in mind the difference between the universe and the observable universe. If a star is sufficiently far away that its distance relative to use is growing at faster than the speed of light, its light will never reach us. The limit of the observable universe is the region just close enough that objects there are moving farther away at just less than the speed of light. If the universe starts shrinking, it just means that all the matter will stop moving away from us and start coming together. The forces inside atoms that keep electrons away from the nucleus will continue to hold, so the atoms themselves won't shrink (same reason atoms aren't being slowly pulled apart by the expansion of the universe: the distance from the electron orbits to the nucleus might be very slowly increasing, but the orbits just get pulled back at the same time). digfarenough (talk) 22:06, 29 August 2006 (UTC)

Also, I would like for everybody to note that expansion theory proposes that spacetime is expanding, and not anything else. The distances are increasing, causing cosmological redshift/blueshift. Distinguishing between coherence and decoherence is vital when discussing "the expanding universe idea."— [Mac Davis] (talk) (Desk|Help me improve)

What do you mean by "distinguishing between coherence and decoherence"? --Lambiam^Talk 04:36, 30 August 2006 (UTC)

For the notion of expanding space (not spacetime) see Metric expansion of space. The latest news is that cosmologists appear to agree that the universe will not eventually contract, but that the expansion is instead accelerating; see Dark matter. For the universe having no edge, see Shape of the Universe. For all we know, it may be infinite. --Lambiam^Talk 04:46, 30 August 2006 (UTC)

In particular, don't assume that "finite universe" = "universe has an edge", at least in the dimensions familiar to us. Spacetime doesn't have to be flat, even asymptotically, so it can curve in on itself. Consider the good old balloon analogy. The surface of the balloon is finite, but in its own geometry it has no edge - travel far enough along it in one direction and you'll end up back where you started, or fairly close to it. Certainly it has a boundary when it's considered as a sphere embedded in familiar 3D geometry (in fact in that case it's all boundary), but that requires leaving the geometry native to the balloon and, if we expend our analogy to the universe, is not something we could easily detect. Confusing Manifestation 14:09, 30 August 2006 (UTC)

Epilepsy

why would some sorts of fast flashing lights and/or random high pitch sounds, supposedly cause an epileptic seizure?. --Cosmic girl 21:20, 29 August 2006 (UTC)

I'm not exactly sure why, but realize that epileptic seizures are a complex thing, cause by some pretty wacky triggers- hot water on the head for example. The correlation between rapidly changing images/sounds and rapidly jerking limbs while seizing may be just a coincidence. See also Photosensitive_epilepsy, though it's not ver y appropriate to your question --Froth 21:36, 29 August 2006 (UTC)

thank you!!!!! :D I didn't know about hot water! interesting... --Cosmic girl 21:47, 29 August 2006 (UTC)

Well, seizures occur when there is too much excitation of neurons: if too many neurons start firing, then they drive other neurons (or themselves) to fire too much, which in turn drive others, etc. and soon way too many neurons are firing (sort of like microphone feedback where all you get is the feedback and no real signal anymore). If some of those neurons are motor neurons, then limbs go a-flailing. The reason high frequency flashing lights can lead to a seizure is that many neurons in the visual system are sensitive to changes in their input. A steady light means no changes, so some cells would only fire when the light is first turned on (and other cells fire when the light goes off). If the light is flashing, then those change-signally neurons start firing pretty much constantly, which leads to the cycle described above. Normally there's a system of feedback inhibition in place, which makes it harder for cells to fire if many are firing, but if that system fails for some reason, you get epilepsy. digfarenough (talk) 22:00, 29 August 2006 (UTC)

Note that flashing lights and advertisements are intensely annoying to many without epilepsy, for the same reason, it's an excessive level of visual input stimulus. StuRat 22:08, 29 August 2006 (UTC)

Chinese pheasant

While researching for Denver Zoo, I came across a reference to "Chinese pheasants." Does anybody have any idea what species these are? Neither Wikipedia nor ITIS have answered this question. Could it be the Chinese Monal? --Ginkgo100 ^{talk · e@} 21:28, 29 August 2006 (UTC)

Peacocks? Just a wildfowl guess 9-)--Light current 21:51, 29 August 2006 (UTC)

No, I doubt it. The source (from a reliable local historian) went on to say the pheasants populated the eastern plains of Colorado and are enjoyed by hunters, and I know for a fact there are no wild peacocks hunted on the plains of Colorado! --Ginkgo100 ^{talk · e@} 22:35, 29 August 2006 (UTC)

Golden pheasants says they are chinese pheasants and the picture at Golden pheasant looks like what I have heard called chinese pheasant. If you search for them on google you find that they are good with onions. MeltBanana 01:07, 30 August 2006 (UTC)

LOL: I kept getting that same link about the onion recipe, which is why I gave up on Google! Thank you for finding the information; I bow to your superior Wikipedia-searching skills. I'll create appropriate redirects now. --Ginkgo100 ^{talk · e@} 20:38, 30 August 2006 (UTC)

Space

Can space exist on its own, or do you need mass to create it?--Light current 22:11, 29 August 2006 (UTC)

lol, space can exist on its own. Mass does not create it, it can only affect it. — [Mac Davis] (talk) (Desk|Help me improve)

Are you sure?? How would you define space? Is it something or nothing?--Light current 23:51, 29 August 2006 (UTC)

Mass needs space, otherwise there'd be nowhere for matter to fit. JackofOz 00:37, 30 August 2006 (UTC)

No! Space needs mass to exist!--Light current 03:14, 30 August 2006 (UTC)

If you're so sure of this, why did you ask your original question? JackofOz 04:41, 30 August 2006 (UTC)

It seems obvious to me now that since you cannot truly escape the bounds of the known universe, you cannot actually get into real space. THis needs moving to talk:space --Light current 11:29, 30 August 2006 (UTC)

No-one knows. But space does have geometry and energy. Now, if we had an extra universe and we took all the mass out... Peter Grey 03:56, 30 August 2006 (UTC)

Your question kind of relates to mine: is a universe without mass or energy really a universe at all, or is it just nothingness, a non-universe, what surrounds this tiny expanding region of matter and energy to infinite depths into the beyond.. --Froth 02:50, 30 August 2006 (UTC)

Its less than nothing. it doesnt exist!--Light current 03:14, 30 August 2006 (UTC)

In quantum field theory the vacuum has energy, and therefore mass. --Lambiam^Talk 05:09, 30 August 2006 (UTC)

Lets ask another question: Is it possible to accelerate your space craft beyond the limits of the universe?--Light current 03:19, 30 August 2006 (UTC)

If that was possible, they wouldn't be truly the limits, would they? --Lambiam^Talk 05:09, 30 August 2006 (UTC)

There isnt even a vacuum. This discussion should be moved to talk:space--Light current 11:29, 30 August 2006 (UTC)

You mean the ZPE field? — [Mac Davis] (talk) (Desk|Help me improve)

There is a vaccum in my closet.. --Froth 14:33, 31 August 2006 (UTC)

THe question is whether you can have ZPE somewhere where ther is no mass around at all. Anyway this discussion should not be here now and I have copied it to talk:space . Pls resume any discussion thers. Thanks

Global warming

Do Americans believe that global warming is occuring and if so why do you believe it is occuring? In the UK we are constantly presented with the idea that you USAers think that global fossil fuel consumption and industrial pollutants do not directly contribute to atmospheric pollution. Instead we are are told that the US does not believe that pollutants directly contribute to the greenhouse effect but that is an aspect of natural climatic change and that our opinon is incorrect. I have seen many Americans on the telly who believe that climatic change is as a result of our use of fossil fuels and industrial processes, but we are constantly lead to believe that the administration does not want to affect change becase of dubious scientific evidence linking them. --russ 22:27, 29 August 2006 (UTC)

I wouldn't be surprised if Bush and friends don't believe in global warming. I wouldn't lump every American him. --liquidGhoul 22:52, 29 August 2006 (UTC)

Most people around the world I think believe in anthropogenic global warming hypothesis. However when a real scienfic discussion arises there can be debate between sketpics and "global warmers"/believers. — [Mac Davis] (talk) (Desk|Help me improve)

I think most Americans and the Bush admin believe in global warming. The admin, however, chooses to suppress the science in order to protect the powerful oil industry, in which they have a personal financial interest. StuRat 23:29, 29 August 2006 (UTC)

That is probably why, although I think it should be noted many aspects of the anthropogenic hypothesis are disputed. — [Mac Davis] (talk) (Desk|Help me improve)

I don't think many serious scientists dispute that carbon emissions are affecting global warming (only those paid off by the oil industry directly, or indirectly via the Bush admin). Exactly how much of global warming is due to carbon emissions, however, is a subject of lively scientific debate. StuRat 05:02, 30 August 2006 (UTC)

According to this, about 1/2 of Americans are concerned about global warming versus 2/3 of UK citizens. Dragons flight 00:10, 30 August 2006 (UTC)

You might ask User:Ed Poor on the subject. User:Zoe|(talk) 01:46, 30 August 2006 (UTC)

Bush says global warming is not based on good science. Many of his fundamentalist followers also do not believe in evolution and think nothing is older than about 6000 years. Edison 03:55, 30 August 2006 (UTC)

Its the sun that causes global warming. Always has been. Always will be!--Light current 03:56, 30 August 2006 (UTC)

Right. And by increasing our burning of fossil fuels, we will block more sunlight due to more particulates in the atmosphere, thereby blocking more of the sun. See? Bush really does believe in, and is working to reduce, global warning! Hmm...guess I better clean this up and submit a manuscript to Ann. Improb. Res DMacks 04:30, 30 August 2006 (UTC)

Don't omit from your manuscript the plan to bomb as many sandy, dusty countries as possible, in order to produce fine silica particulates. this is an international program, with assistance from great britain, israel, hamas, hizbollah... Xcomradex 05:02, 30 August 2006 (UTC)

Is this a Bush-joke section of the desk? Global dimming was something that some scientists were concerned about not long ago. — [Mac Davis] (talk) (Desk|Help me improve)

we all know the real cause: http://uncyclopedia.org/wiki/Global_Warming#Causes Xcomradex 06:29, 30 August 2006 (UTC)

No, no, it's the terrorists who cause global warming. During the days after 11-9 all planes were grounded in the US. As a result there were fewer clouds, resulting in more sunshine and hence more warming. So there you go! :) DirkvdM 09:27, 30 August 2006 (UTC)

I heard that too. Its a very complex subject indeed.--Light current 14:40, 31 August 2006 (UTC)