Wikipedia:Reference desk/Archives/Science/2008 December 29

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December 29

consuption of electricity by refrigrator

when we have different speed of cooling on two same type of refrigrators ,is there any effect on the consuptions of electricity electricity .By adjusting the lower speed can we reduce our electricity bills. —Preceding unsigned comment added by Khubab (talk • contribs) 01:14, 29 December 2008 (UTC)

Since no one else has bitten yet. I'm not quite sure what you are trying to get at here. Please see Refrigeration. If we are talking standard refrigerator the setting you can choose is the temperature. The lower the temperature setting the longer and more often the pump will run to cool the air inside the fridge. This will cost more energy than selecting a higher temperature. A fridge with better insulation to the (warmer) ambient air and a more efficient pump can save energy. However the "speed of cooling" is not a term that can be applied here AFAIK. 76.97.245.5 (talk) 09:01, 29 December 2008 (UTC)

There could be two almost identical fridges, but where one has a more powerful compressor capable of cooling quicker. In that case, provided that the temperature was set the same, the energy usage should be about the same, although the more powerful compressor would use more power, but for shorter periods of time. StuRat (talk) 09:44, 29 December 2008 (UTC)

female virginity question

(Medical Advice request removed by JSBillings ) PitchBlack 03:38, 29 December 2008 (UTC)

Sounds like you're asking for Medical advice. Ask your doctor. -- JSBillings 03:52, 29 December 2008 (UTC)

Whilst I don't have an answer for you - if this question is really about you (or someone you've been sleeping with), please seek medical advice from a real, qualified, flesh and blood doctor. --Kurt Shaped Box (talk) 03:52, 29 December 2008 (UTC)

A woman I consulted, who was once a virgin, suggests you should see a doctor if the symptoms you cited are a concern. Edison (talk) 04:55, 30 December 2008 (UTC)

Differnece in growth of Neem tree and Banana tree

If we cut the stem of the Neem tree, Leaves and branches comes at sideways. but this is not in the case of the stem of banana. If we cut it new one grows near the banana tree. what is the reason. —Preceding unsigned comment added by 203.129.203.164 (talk) 05:54, 29 December 2008 (UTC)

Do look up Monocotyledon and Dicotyledon. Shyamal (talk) 06:29, 29 December 2008 (UTC)

What logical fallacy is this?

First, I know this is the science desk, and maybe this is more of a miscellaneous question, but science and logic are connected so... Is there a name for the following logical fallacy: "The earth is lucky, because it is in the perfect green zone, not too far and not too close to the sun, etc." The same mislogic is shown when a person says "you are lucky because some other sperm could have reached the egg and you would never have existed if that had happened." Is this a named logical fallacy? One thing, I am not here to discuss whether either example is a fallacy or not. You are not going to convince me either is not and I'm not interested in that debate. Thank you.--68.237.248.155 (talk) 06:46, 29 December 2008 (UTC)

Confirmation bias? Or is that backward? —Tamfang (talk) 08:09, 29 December 2008 (UTC)

Not specifically named as a fallacy, but it is an expression of the Anthropic principle - in particular, there are two ways of looking at it: you can either marvel at the fact that something as unlikely as a planet capable of supporting sentient life exists, or you can point out that if it didn't, we wouldn't be here to marvel at it so it's not really a surprise that it does exist. I suppose it's a little bit like confirmation bias as well, like Tamfang suggests. Confusing Manifestation(Say hi!) 10:39, 29 December 2008 (UTC)

Try here List of cognitive biases. I think it is probably more of a False analogy - usually these "you're lucky" are used to try compare apples and oranges. 194.221.133.226 (talk) 10:43, 29 December 2008 (UTC)

This is related to the argument from personal incredulity, which often comes up in discussions related to Intelligent Design. The argument that "the world is too complex so it must be designed" is similar to a puddle of water marvelling at the fact that it fits exactly in its container, so it must have been designed too. ~Amatulić (talk) 22:35, 29 December 2008 (UTC)

The problem for me is that the planet has no preference for life or no life - it's a non-living, non-sentient thing. It doesn't care whether life forms upon it's surface or that it's barren. So 'lucky' doesn't really apply here. Sure, there is a statistical probability of it being in the 'green zone' - and that probability seems to be rather small. But if you imagine a planet that passionately didn't want to be infested with amoeba, ants, aardvarks, anchovies...and zebra then you'd say that it was "unlucky" to end up where that infestation could happen. So was the earth "lucky" or "unlucky"? You can't give an answer to that unless you know what outcome it "wanted" - and it's a big lump of rock that really doesn't care either way! So I think we have to 'unask' this question - it's meaningless. If instead you are asking "Was it lucky that the planet on which we humans developed was in the green zone?" then we most certainly have to defer to the "anthropic principle which says that if the planet hadn't done so, we wouldn't be here to ask the question - hence it's 100% certain that whatever planet we'd call "Earth" must be in the habitable zone. So I think the best answer for you is "The Anthropic Principle". SteveBaker (talk) 23:22, 31 December 2008 (UTC)

Multiple near-death experiences and emotions

I'll let the wind blow out the light
'Cause it gets more painful every time I die.

— Children of Bodom

In people who have had multiple near-death experiences, are the subsequent ones more likely to be strongly negative than the first one? NeonMerlin 13:31, 29 December 2008 (UTC)

I have had three near-death experiences (assuming you don't consider having my heart completely stop to be a "death-experience"). I don't remember any of them. They aren't positive or negative. I believe it is simply how memory works. When you nearly die, there is no transition of short-term memory to long-term memory. So, the short term memory of the events right before and including the event are not sent to long-term memory. I remember riding my bike and thinking "I need to get to the other side of the road" and then I remember waking up on the side of the road and not being able to move. I remember riding my motorcycle (while rather drunk) through the Mojave at night and suddenly realizing that there was no bike below me and then waking up in a bunch of rocks at the bottom of a steep cliff. I remember riding my motorcycle along a small road in the marsh and thinking that the headlights ahead appear to be swerving and then waking up when an paramedic grabbed my shoulder. So, the "experience" is gone. I could make up stories about bright lights and angels, but all I remember is one thing before the event and something after the event. -- kainaw™ 14:33, 29 December 2008 (UTC)

Yet you seem eager to have the same "non-experience" over and over again... Lova Falk (talk) 17:27, 29 December 2008 (UTC)

Far be it from me to imply unsolicited advice (*cough*) but were you aware that emergency room physicians – when they think no one is listening – tend to refer to motorcycle riders as 'organ donors'? TenOfAllTrades(talk) 17:54, 29 December 2008 (UTC)

I know. Even motorcycle riders say: It isn't "will I have an accident", it is "when will I have an accident." -- kainaw™ 20:35, 29 December 2008 (UTC)

Not sure I'd label the actual near-death experience as positive or negative, but - while I have never had one myself - I know a devout Christian who says that with his, he doesn't remember details, but what troubles him most is the fact that - after having been in a perfect state where he could feel no pain, there was no suffering, he wasn't tempted by his flesh, etc., now he's back here on earth, where it's just so difficult, because of the limitations.

So, I would posit that the feelings around the experience can be recalled; but it probably depends on how long one was *gone*, etc.. Which makes sense, because even then, as you say, it's not memories of things, but simply of emotions/feelings, to him.

I'll note that the Apostle Paul seems to share your view more - he says it is not lawful that a man may utter the things in the "third Heaven," not because it is illegal, but it is against the laws of nature; the nature of the one experiencing it doesn't permit him to recall or utter them.Somebody or his brother (talk) 13:47, 30 December 2008 (UTC)

chances developing same affliction

What are the chances that 2 brother's-in-law that are married to twin sisters develop acromegaly with the same type of pituitary tumor at the same time? These men live in different cities. Could foul play be involved? —Preceding unsigned comment added by CAElick (talk • contribs) 14:42, 29 December 2008 (UTC)

Perhaps both sisters were attracted to their future husbands because the physical effects of the disease? Sometimes twins both have the same preferences in a partner. Either that or both sisters are injecting human growth hormone into their husbands. -- JSBillings 16:36, 29 December 2008 (UTC)

Regular, repeated injections of human growth hormone could cause acromegaly, but I'm not sure how the sisters could also produce a pituitary adenoma. (For that matter, I find it difficult to imagine how they would have been able to covertly give regular injections of HGH to their husbands.) Though the incidence of acromegaly is pretty small (call it about four cases per million people per year: [1]) someone has to get it. (A couple of factors do improve those odds slightly, however. Men are more likely to have somatotrophic adenomas than women, and if the brothers are still in early to middle age they're at the peak time for developing the disorder.) Meanwhile, acromegaly usually progresses very slowly, and it typically takes more than ten years from symptom onset to diagnosis unless the doctor is primed to look for it — as when the patient casually mentions his brother-in-law's case.

(From here on in, I'm going with the Fermi problem approach, so use these numbers with caution.) The naive estimate (based on disease incidence) of both brothers-in-law being diagnosed with acromegaly at roughly the same time is about 1 in 100 billion. Taking into account the factors I mentioned above, the actual odds may be a couple of orders of magnitude better: closer to 1 in a billion. (As JSBillings notes, the twins might also find similar mates attractive, which my imply an additional component of shared genetic risk and further increasing the odds.) That being said, before you congratulate the two gents on being so 'lucky', you might want to consider a slightly different question: What are the odds that two brothers-in-law happen to develop rare diseases within a year of each other? If you figure that there are a thousand 'rare' disease with roughly the same incidence as this one, you're up to (roughly speaking) a one-in-a-million shot at any given pair of brothers-in-law sharing some disease. Still not what I'd call good odds, but better than your shot at the jackpot in most lotteries — and people keep winning those.

To approach your question about foul play, I'd say the jury's hung (at best). It's an improbable coincidence, but still quite possible. And so far no one's come up with a likely method by which the disorder could be surreptitiously induced. Absent that, the twins are going to walk. TenOfAllTrades(talk) 17:19, 29 December 2008 (UTC)

Be careful with assigning causal responsibility where there may not be any. Detecting causality can be a good survival trait. (If the other guy who angered the big boss got whacked on the head, angering the big boss might be detrimental to health and long life.) But it's not unheard of for relatives to assign blame to the spouse if someone dies or suffers from a severe illness. People do statistically get ill and even at the very unlikely end of the curve. Nonwithstanding that I'll imprecisely quote a criminal investigator who said that our cemeteries are full of victims of undetected spousal murders. (aka. divorce alternative) [2] The question becomes one of cost vs. benefit when asking questions. Are you likely to prevent injury to yourself or others by accusing the twins of wrongdoing? On the other hand it is almost a given that your relationship with them will be impaired if you suspect them of anything ranging from the evil eye to criminal intent. In it's extreme such witch-hunts can lead to alienation and even kill people. No medical or legal advice intended other than to use ones head before pointing fingers. Lisa4edit (talk) 23:56, 29 December 2008 (UTC)

antibiotics

Are Antibiotics effective? —Preceding unsigned comment added by Shodson8 (talk • contribs) 16:56, 29 December 2008 (UTC)

With some caveats, most antibiotics – prescribed and used correctly – are generally effective against appropriately-diagnosed target organisms. When taken inappropriately (against a viral infection, for example) they don't do a damn thing that's useful and may cause a number of problems. TenOfAllTrades(talk) 17:25, 29 December 2008 (UTC)

Interesting question, I'd say yes when used properly. If everyone used their antibiotics correctly (specifically finishing the course given, going back if you need more and finishing again, and prescribed correctly by the doctor) then there's little chance that an organism will evolve to become resistant; however, there's always a chance that the bacteria will become resistant. The chance, however, is significantly reduced by correct use and prescription. —Cyclonenim (talk · contribs · email) 18:36, 29 December 2008 (UTC)

If as TenOfAllTrades and Cyclonenim indicated you are prescribed those antibiotics by a doctor, that would usually indicate that your body is battling an infection. Alternatively you might have been given the antibiotics as a prophylactic measure if your body is too weak to ward off infections (e.g. after an operation). In both cases there is an indication that your body needs help dealing with the invading pathogen(s) and would incur severe damage, or at the very least make you feel very miserable for an extended period, without. By comparison if the antibiotics are prescribed and taken correctly they will reduce the number of pathogens and give your body a chance to heal. As with everything in nature there are many factors affecting the efficiency of antibiotics and there are cases where they aren't effective or even make things worse. The best we can do is to keep such cases to a minimum. Nevertheless, even if there are more and more of the little buggers that develop resistance, and allergies are an ever growing problem, I'd say antibiotics are effective if taken as prescribed.76.97.245.5 (talk) 20:38, 29 December 2008 (UTC)

Genome: Both good and original, but...

Samuel Johnson is attributed with saying to an aspiring writer, "Your manuscript is both good and original, but the part that is good is not original and the part that is original is not good." Is it likely that my genome is like that manuscript? NeonMerlin 19:17, 29 December 2008 (UTC)

The analogy would be considered off from a scientific perspective (not counting these}. A writer follows a purpose when creating his/her work. Nature is generally considered to be a conglomeration of events that happen without an overall ulterior motive. Individual elements may pursue certain interests like survival, procreation and quality of life but the overall effect may actually be harmful rather than beneficial to either the individual, it's species or the environment. For writers there are people in certain positions that established guidelines as to what they considered "good". (One should note that even that is a qualification not everyone agrees on.) In order to draw this analogy you'd have to specify what makes a portion of your Genome "good" and by whose standards. Just a couple of pointers to illustrate: Noncoding DNA was considered "junk", however, we have since discovered that some of those portions serve a function. Some congenital disorders have "beneficial" side effects. Would you e.g. consider the alleles that cause Sickle-cell disease good because it protects the bearer from malaria or bad because it makes them die sooner? Is the superior immune system that seems to come with Huntington's disease worth the cost? The genes that enabled humans to store fat efficiently enabled our ancestors to make it though lean time, yet is currently causing millions of their descendants trouble. The list goes on.76.97.245.5 (talk) 21:36, 29 December 2008 (UTC)

Assuming you mean "good" as advantageous to your survival, then its not a particularly appropriate analogy. Your "not original" genome is the sum of that which you inherited from either parent. It can contain elements that are good or not good in this context. The original part of your genome is a result of genetic mutation. It can be good (a change that proffers an advantage) or not good (a change that proffers a disadvantage) or neutral. Rockpocket 21:41, 4 January 2009 (UTC)

Putting milk in coffee

Imagine you made two identical cups of coffee. Imagine you made them both at 2pm so that they started off at the same volume and temperature (say 300ml at 100C), and you added an amount of cold milk (say 30ml at 5C) to one of them at 2pm and the same amount of milk at the same temperature to the other at 2.10pm. At 2.20pm, I believe that the drink you added the milk to first would be warmer than the drink the milk was added to later (assuming that neither drink had yet reached room temperature). Is that correct? —Preceding unsigned comment added by Milk Please (talk • contribs) 20:18, 29 December 2008 (UTC)

For the milk-coffee cup, the start temp, T(0), may be estimated as 300*100+30*5/330.

The formula you want to calculate the temp at 10 minutes, t=10, is T(t) = Ta + (T(0) - Ta)e^-kt where Ta is the ambient room temperature.

Then, you have the temp of both cups at 10 minutes. Repeat the first step to calculate the change in the second cup's temperature.

Finally, recalculate the temp 10 minutes later using the formula from the second step. -- kainaw™ 21:01, 29 December 2008 (UTC)

(EC) The one you add the milk to last should be colder, yes. The reason is that the temp loss is proportional to the temp diff (relative to the environment), so the hot coffee will give off more heat than the cold coffee. Thus, keeping it hot as long as possible ensures the maximum heat loss. StuRat (talk) 21:04, 29 December 2008 (UTC)

We get this question (and variations thereupon) so often on the Science Reference Desk that I have decided to create a configurable Milk + Coffee Simulator.

Simulation Code, in MATLAB

clear;close all;
room_ambient_temp = 25;

tau_nlc = 60;   % Time constant (Seconds) for the cooling
r_nlc = 1/tau_nlc; % constant for Newton's Law of Cooling in the form dT/dt = -r(T-Tamb)

% Initial coffee and milk parameters
coffee_volume = 300;   % mL
coffee_temp0  = 100;   % degrees C
milk_volume   = 30;    % mL
milk_temp0    = 5;     % degrees C

% Initialize the coffee and milk parameters
coffee1_temp(1) = (coffee_temp0*coffee_volume + milk_temp0*milk_volume)/(coffee_volume+milk_volume)
coffee2_temp(1) =  coffee_temp0;

%%Loop over time, measured after 2:00 PM, in seconds
for t = [1:60*30]
    coffee1_temp(t+1) = coffee1_temp(t) - r_nlc*(coffee1_temp(t)-room_ambient_temp);
    coffee2_temp(t+1) = coffee2_temp(t) - r_nlc*(coffee2_temp(t)-room_ambient_temp);
    

    % At time 2:10, add milk to Coffee #2
    if (t == 60*10)
        coffee2_temp(t+1) = (coffee2_temp(t)*coffee_volume + milk_temp0*milk_volume)/(coffee_volume+milk_volume)
    end
    
end


%% Plotting, including time-stamped x-axis
time_labels = datenum(2008, 12, 29, 14, 0, 0) + 1/(24*60*60)*[0:60*30];
plot(time_labels,coffee1_temp, 'r'); hold on;
plot(time_labels,coffee2_temp, 'b');
datetick('x', 16);
xlim([datenum(2008, 12, 29, 14, 0, 0), datenum(2008, 12, 29, 14, 20, 0)]);
legend('Coffee 1 - Milk Added at 2:00', 'Coffee 2 - Milk Added at 2:10');
xlabel('Time');
ylabel('Temperature (Celsius)');
title(['Hot Coffee Simulation with \tau = ' , num2str(tau_nlc) , ' sec']);

I obtained this temperature curve set when I set the time-constant of cooling to 1000 seconds (just over 15 minutes). Nimur (talk) 21:53, 29 December 2008 (UTC)

Is this Matlab stuff supposed to do something? Not in my Safari browser. --VanBurenen (talk) 21:59, 29 December 2008 (UTC)

Now the show/hide thing is working Ok. Thanks. --VanBurenen (talk) 22:01, 29 December 2008 (UTC)

Well, I haven't yet written a web-interface, it's only been about ten or twenty minutes; maybe in the next few days I'll put a CGI site up where you can input initial milk and coffee parameters and auto-generate the temperature curves. In the meantime you will need to obtain MATLAB or the GNU Octave to run this code yourself. Nimur (talk) 22:01, 29 December 2008 (UTC)

Did you consider the cup when running the matlab? In case you are using a ceramic mug and not a styrofoam cup I would have expected the mug to absorb and retain heat and lead to a (very slightly) higher temperature for the milk added later.Lisa4edit (talk) 00:11, 30 December 2008 (UTC)

The cup is not modeled explicitly. If you check out the Newton's Law of Cooling article, you can see a formulation of the model which estimates the time constant as (Heat transfer coefficient x surface area)/(mass*heat capacity). You could then calculate an exact time-constant, accounting for conduction to the air and walls of the cup, if you know the dimensions of the mug. However, you would still need to estimate the heat capacity and heat-transfer-coefficients for the materials (or look them up from an empirical table). Instead I chose to simply estimate the time constant, because "coffee takes about 15 or 30 minutes to cool to room temperature," which I found a suitable estimate. I also found a Web Octave interface, so you can now run the code from your browser - you may need to modify some of the plotting parameters for MATLAB/Octave compatibility. Nimur (talk) 13:40, 30 December 2008 (UTC)

OK, so this is not quite as straightforward as I thought it mighe be, I think this is because the cup can act as some kind of heatsink. So the coffee initially without milk, will lose heat more rapidly, but some of that heat will be stored in the mug. The coffee with milk will lose heat less rapidly, but less of that heat will be stored in the mug. As the two coffees cool some of the heat from the mugs will pass back into the liquid, slowing the overall rate at which it cools. In theory the amount of heat stored in the "non-milk" mug, and the rate at which it passes back into the liquid, might counteract the increased cooling caused by the greater temperature gardient between the "non-milk" coffee and the air. Is that right? Milk Please (talk) 11:11, 31 December 2008 (UTC)

Incidentally, I had to force myself to not use the heading "Hot Coffee", but I see that Nimur couldn't resist! :) Milk Please (talk) 11:17, 31 December 2008 (UTC)

I believe that this "heatsink" effect that you are mentioning would only change the value of the time constant of cooling. I don't think it would have any more complicated effect. Nimur (talk) 14:13, 31 December 2008 (UTC)

Well, as promised, I have delivered a totally unnecessary web interface to my Hot Coffee Simulator. It's a little bit clunky but I figured it was a good opportunity to try out Octave as opposed to MATLAB. Of course let me know if anything breaks... Nimur (talk) 21:50, 31 December 2008 (UTC)

Ni-MH Battery Behavior (Nikon EN-4 knockoff for D1 camera)

My batteries for my Nikon D1 are relatively new (a few months old), and have always given me trouble. They randomly stop working altogether after sitting overnight, and the battery meter often shows no sign of a low battery. To investigate, I ran the following experiment, and I would appreciate analysis. Please note that the experiment for battery #2 has not been completed yet, and please also note that the time intervals between tests is not regular. Thanks in advance for your help!

Experiment: Test battery's voltage at intervals starting from when it first comes off the charger and ending when it no longer powers the Nikon D1 camera. Voltage tests are performed immediately after each camera test. Batteries are stored outside of camera in between tests.

BATTERY 1 (Powermart DNK004, rated 7.2 V)

2008-12-23 18:53 EST - 8.63 V, powers camera. (straight off of charger from normal Charge cycle)
2008-12-23 21:18 EST - 8.43 V, powers camera.
2008-12-24 00:04 EST - 8.36 V, powers camera.
2008-12-24 11:31 EST - 8.26 V, powers camera.
2008-12-24 20:17 EST - 8.21 V, powers camera.
2008-12-24 22:47 EST - 8.20 V, powers camera.
2008-12-25 01:09 EST - 8.18 V, powers camera.
(Experimental procedure change: Battery 1 is kept in D1 camera with power turned off instead of disconnected from camera.)
2008-12-25 10:39 EST - 8.14 V, powers camera.
2008-12-25 21:56 EST - 8.10 V, powers camera.
2008-12-26 12:09 EST - 8.06 V, powers camera.
2008-12-27 01:45 EST - 8.03 V, powers camera.
2008-12-27 13:35 EST - 8.00 V, powers camera.
2008-12-29 15:08 EST - 2.97 V, fails to power camera.

BATTERY 2 (Powermart DNK004, rated 7.2 V)

2008-12-23 14:41 EST - 8.57 V, powers camera. (straight off of charger from overnight Refresh cycle)
2008-12-23 15:15 EST - 8.46 V, powers camera.
2008-12-23 15:44 EST - 8.41 V, powers camera.
2008-12-23 16:13 EST - 8.38 V, powers camera.
2008-12-23 17:47 EST - 8.31 V, powers camera.
2008-12-23 18:52 EST - 8.28 V, powers camera.
2008-12-23 21:19 EST - 8.24 V, powers camera.
2008-12-24 00:05 EST - 8.21 V, powers camera.
2008-12-24 11:32 EST - 8.15 V, powers camera.
2008-12-24 20:17 EST - 8.11 V, powers camera.
2008-12-24 22:48 EST - 8.10 V, powers camera.
2008-12-25 01:09 EST - 8.09 V, powers camera.
2008-12-25 10:41 EST - 8.06 V, powers camera.
2008-12-25 21:57 EST - 8.04 V, powers camera.
2008-12-26 12:09 EST - 8.01 V, powers camera.
2008-12-27 01:45 EST - 7.99 V, powers camera.
2008-12-27 13:36 EST - 7.98 V, powers camera.
2008-12-29 15:09 EST - 7.93 V, powers camera.

Steevven1 ^{(Talk) (Contribs) (Gallery)} 20:36, 29 December 2008 (UTC)

Are you sure they are supposed to last for more than 6 days without charging ? The batteries for my walkie-talkies seem to only last a day or so off the charger, and my cell phone lasts maybe about a week. So, you seem to be right in that range. StuRat (talk) 20:57, 29 December 2008 (UTC)

Your walkie-talkie and cell phone batteries are completely exhausted after being off of the charger for one day and one week respectively, while the devices are turned off? This seems strange to me. Steevven1 ^{(Talk) (Contribs) (Gallery)} 21:35, 29 December 2008 (UTC)

Your results for battery 1 are surprising. If the battery is not under load, why would it drop from 8.00 volts on 12-27 to 2.97 volts on 12-29. Was here some load on the battery in the meantime? Otherwise I would call it a "dud." For battery 2, you did not provide a report of a voltage at which it did not operate the camera ok. More and better characterized data is needed. Edison (talk) 04:39, 30 December 2008 (UTC)

Since the experimental method for battery 1 was changed to leaving it in the camera midway through, I'd be inclined to suspect that the camera does not in fact turn "off" but instead has a vampire (standby) current that results in depletion of the battery. Depending on the physical state of the battery, it could deliver rated voltage then rapidly decline. If it's still in the warranty period, I'd say take it back with "doesn't show low-charge before it stops working". Franamax (talk) 01:13, 31 December 2008 (UTC)

Optimal Eyepiece Diameter

Hello. I read the binoculars article and wondered: What is the optimal eyepiece diameter for 7×50 binoculars so that I am not seeing two small dots and too much environment outside the binoculars? Thanks in advance. Have a happy new year. --Mayfare (talk) 20:53, 29 December 2008 (UTC)

Your question is unclear: "two small dots????" Why wouldn't you want the eyepiece diameter to match the dark-adapted iris?Edison (talk) 04:34, 30 December 2008 (UTC)

When you look at the eyepieces closely, the eyepieces should not be so small that they are two small dots. Matching the dark-adapted iris - that leads me to an idea. --Mayfare (talk) 17:34, 30 December 2008 (UTC)

The holes in which the light exits is called the exit pupil. It is calculated by dividing the lens diameter by the magnification[3]. So, your binoculars' exit pupils should be about 7 mm. However, the optimum size for an exit pupil should be around 5 mm, depending on what you're viewing. It doesn't have much to do with the eyepiece diameter, because adjusting it would affect the madnification of the binoculars. Actually, that's the telescope formula, but maybe try searching the website for more info. I'm thinking either they put rings in the eyepiece, or the prism affects it, or you're just underestimating what the exit pupil actually is. Either way, hope this helps. Thanks. ~AH1^(TCU) 23:33, 31 December 2008 (UTC)

What is this??????

Really cool invertabrae. http://www.flickr.com/photos/pokerchampdaniel/3136421527/

Looks like a sort of ribbon worm. Nemertea is the phylum, but I have no idea of the genus, or species. ~Amatulić (talk) 22:21, 29 December 2008 (UTC)

So when it "squirts" out of its...uh...skin?..is that its method for moving quickly? --71.117.36.29 (talk) 00:34, 30 December 2008 (UTC)

From the German page: The proboscis lies dorsal of the colon in a coelom (in this case rhynchocoel). It can be everted frontally if needed. [4]Lisa4edit (talk) 01:06, 30 December 2008 (UTC)

Looks to me like an animal from the Hemichordata.