Wikipedia:Reference desk/Archives/Science/2007 March 30

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March 30

glasses

Why do some glasses lenses have white circles near the outside or white edges? —The preceding unsigned comment was added by 219.88.165.55 (talk) 04:32, 30 March 2007 (UTC).

White circles? I've never seen one of those. Are you referring to Glasses or Camera Lenses? The white edges you see are mostly Total internal reflection of the glass acting like a mirror and reflecting the incoming light, and thus make it look brighter and looks like white edges. --antilived^{T | C | G} 04:59, 30 March 2007 (UTC)

Why doe some of the lenses edges seem more noticeable and bigger than others

Maybe you're noticing the thickness of the lens. The edge that fits into the frame can appear white or grey. Dismas|^(talk) 06:09, 30 March 2007 (UTC)

Not talking about the bifocals lenses, right? --Wirbelwindヴィルヴェルヴィント (talk) 06:37, 30 March 2007 (UTC)

Nearsighted people wear concave lenses to correct their vision to normal. These are thinner in the center than at the edge, resulting in thick edges. If the person has astigmatism, there is an additional cylindrical component to the lens shape, which can make the edges even thicker in one axis of the lens. An extra cost option for lenses is to polish the edge, which otherwise has a "frosted" appearance and is more noticeable. Glass lenses are typically thinner than plastic lenses, but "high index" plastic lenses are thinner and lighter than cheaper plastic lenses. A stronger prescription for nearsightedness makes the edges of the lenses thicker, as does having larger "avaitor style" lenses. Edison 18:06, 30 March 2007 (UTC)

Well, no, because all eyeglass lens are "meniscus-shaped", whether the prescription is + or - D (RTFA :)

Is it possible to get rid of the white edges?

Terrormenace 07:33, 3 April 2007 (UTC)

How do compass work?

How do compass work? —The preceding unsigned comment was added by 134.139.194.18 (talk) 06:29, 30 March 2007 (UTC).

Wikipedia has an article about it, check it out at compass. Return if some questions remain unanswered. --V. Szabolcs 06:35, 30 March 2007 (UTC)

some organic stuff

File:Reaction.GIF

Can somebody tell me how to do these reaction? —The preceding unsigned comment was added by Bastard Soap (talk • contribs) 10:48, 30 March 2007 (UTC).

What do you mean by "do" ? Do you want a balanced equation, instructions on how to combine the reagents (temp, etc.) to get the desired reaction, or what ? StuRat 00:06, 31 March 2007 (UTC)

I would like to know the conditions and the reactants necessary for these reactionsBastard Soap 09:14, 31 March 2007 (UTC)

Blood Pressure

Suppose if a person does weight lifting excercise only with right hand and not with left hand, then blood pressure of only right hand will increase or there is increase in blood pressure in both the hands. Why? —The preceding unsigned comment was added by 203.94.214.34 (talk) 12:00, 30 March 2007 (UTC).

The blood system basically a long tube full of blood. It is very similar a hose with water flowing though it. So, you are asking a question similar to: If you put water in one end of the hose, will the water pressure only increase on the end you put water in? No. There is no restriction on the flow of the water. In the blood system, there is almost no restriction. Blood pressure increases throughout the body. If you've seen a power lifter before, you can see the pressure increasing all the way to the top of his head when he does a dead lift. --Kainaw ^(talk) 12:25, 30 March 2007 (UTC)

So, is the blood pressure in an erect penis the same as flaccid? [Mαc Δαvιs] (How's my driving?) ❖ 16:29, 30 March 2007 (UTC)

Hmm interesting that should come up! I think it must be higher, but look up penis and tumescence, and maybe hard on —The preceding unsigned comment was added by 88.110.49.118 (talk) 00:56, 31 March 2007 (UTC).

Blood flow is restricted during an erection. I specifically stated that the blood pressure is pretty much the same in an unrestricted system. Inability to restrict blood flow in the penis is a common cause of erectile dysfunction. --Kainaw ^(talk) 14:35, 31 March 2007 (UTC)

Rhinitis vs. Cold

This is not a request for medical advise. I suffer from year-round rhinitis and it seems that, despite my suffering and dependence on Claritin, I do not contract the cold virus as much as the people who work or live around me. I wonder if that might have anything to do with my sinuses constantly draining making it difficult for the virus to flourish. Any thoughts? --Juliet 14:05, 30 March 2007 (UTC)Auto-Unsigned -->

how does a bidirectional turbine function?

I recently read that tidal barrages or other tidal energy converters, make use of bidirectional turbines that will spin and generate energy regardless of whether the water is flowing in or out past the blades. I believe that the turbines do not spin around in order to keep the blades in the same position relative to the movement of water, and they rotate in the same direction (ie. clockwise) regardless of the water flow. I understand why the rotors would move if the water is flowing in a single uniform direction, but my question is how does this work in this situation where the direction of water flow can reverse completely but still spin the rotor blades the same way? Is it completely due to the shape of the blades, and how is this accomplished? Is this a relatively new concept? 220.34.254.226 14:18, 30 March 2007 (UTC)

Well, a simple propellor-type turbine is equally (in-)efficient running in either direction. I would guess that the turbine itself does reverse direction. For AC power generation, rotation direction doesn't necessarily matter. -- mattb @ 2007-03-30T14:58Z

Are you sure the turbines rotate in the same direction regardless of the water flow direction ? That doesn't seem likely, since it isn't necessary to generate AC, as noted by the previous responder. If they did want to accomplish that without turning the entire turbine around, they could reverse the pitch on each blade. This would be rather complicated and you would need to go with flat blades instead of curved, however, so would reduce efficiency. I believe some helicopters have the ability to change their blade pitch, so it is possible. StuRat 00:01, 31 March 2007 (UTC)

"Some" helicopters?!? Read the helicopter article, there, Stu: they all do; it's central to the way they work.

The vehicles that merely sometimes have variable pitch propellers are prop airplanes and boats. "Rather complicated" it may be, but it's quite routine; it's done all the time.

(Aside: just a few days ago I heard about an accident in which some researchers working with an autonomous underwater vehicle in the water behind a support vessel asked the captain of the vessel to make sure his engines were at "all stop" so that the rotating propeller couldn't accidentally damage the vehicle in the water. Unfortunately the intent of this request wasn't communicated accurately, and as it happened, this boat had a fully variable-pitch prop that could drive the boat forward, or in reverse, or be in neutral, all by varying the pitch of the prop blades, and all while the propeller continued to rotate in the same direction. So when the captain put the controls at "all stop", the prop was still turning, and the AUV did accidentally come into contact with it, and was basically cut in half.)

—Steve Summit (talk) 00:36, 31 March 2007 (UTC)

I think you and Stu are talking about different pitches. Helicopters all have the ability to change the pitch, as in the way the entire blade tilts. Stu is probably talking about changing the angle of individual blades relative to the plane normally parallel to the blades. --Wirbelwindヴィルヴェルヴィント (talk) 17:26, 31 March 2007 (UTC)

I'm not seeing the distinction -- can you elaborate? —Steve Summit (talk) 18:02, 31 March 2007 (UTC)

In one, you're changing the angle of the entire rotor, and in the other, you're changing how sharp of an angle the blades of the rotor has in respect to the entire rotor. --Wirbelwindヴィルヴェルヴィント (talk) 18:27, 31 March 2007 (UTC)

I think you're misunderstanding how a helicopter works. When you say, "changing the angle of the entire rotor", are you imagining that the angle of the propellor shaft changes with respect to the body of the vehicle? Are you imagining that if the helicopter wants to go forward, the whole rotor tilts forward? That's not the way a helicopter works.

The blades of a helicopter's main rotor are all variable-pitch, and they actually vary their pitch individually and continuously as the rotor rotates. If the helicopter wants to go forward, each blade moves so that it has a higher angle of attack when it's swinging over the rear of the helicopter (generating slightly more lift), and a lower angle of attack when it's swinging over the front (generating slightly less lift), and thus causing the entire helicopter to both pitch and move forward. If the helicopter wants to roll to the right, the blades move so that they have a higher angle of attack when they're swinging over the left side, and a lower angle of attack when they're swinging over the right, and this causes the whole helicopter to roll to the right. —Steve Summit (talk) 19:55, 31 March 2007 (UTC)

It's actually even more complex than that because when the helicopter is flying forwards, the rotors on one side are moving with the direction of flight and the ones one the other side are moving against it. This results in more airflow over each rotor as it moves forwards and less as it moves back. To stop the helicopter from rolling over, the pitch of the leading rotors has to be a little less than the ones on the other side. Only when the helicopter is hovering dead still are all of the rotors staying at the same pitch. The tail rotor also has variable pitch...but the blades don't change pitch as they rotate like the main rotor does. Because the tail rotor is geared from the main rotor, when you increase the engine RPM, the tail rotor would tend to push the tail around - so the pitch of the tail rotor has to change with engine RPM as well as when the helicopter needs to change direction. Helicopters are way more complex than most people imagine. SteveBaker 17:16, 2 April 2007 (UTC)

I said "some" because I'm not sure that all helicopters work that way. How about twin rotor helicopters ? How about other "fringe" designs ? Can you guarantee that all those designs employ the same rotor blade tilt mechanism ? StuRat 01:12, 3 April 2007 (UTC)

No - front/rear twin rotor designs like the CH-47 Chinook, side-by-side twin rotor craft like the V-22 Osprey and even the more dubious Coaxial rotor designs favored by the Russians (the Kamov Ka-50 for example) all work the same way as a 'conventional' helicopter with a swash-plate that continually adjusts rotor pitch. This is an absolute necessity in controlled forward flight. SteveBaker 05:54, 3 April 2007 (UTC)

At least some bidirectional turbines use cylindrical rotors (not like an aircraft propellor - more like the paddle-wheel on an old time steamship) these are called Savonious rotors - they are particularly popular for windmills because the turbine spins the same way no matter which direction the wind comes from so you can rely on the windmill no matter which way the wind blows from. The advantage for generators is that the blade in the same direction regardless of flow direction. This is useful because the shape of the blades and the subsequent generator stages may be optimised for a particular rotation direction. SteveBaker 17:16, 2 April 2007 (UTC)

The upside of smoking - less minor, annoying colds?

As an on-off heavy smoker, I have noticed that during my smoking periods, I tend to suffer from less minor colds, runny noses and sore throats (ashtray throat and smoker's cough in the morning excepted). It has been suggested to me that this is because the cigarette smoke kills off some of the cilia in my respiratory system and prevents the mucous from being brought up from the lungs. Does anyone know if there's any scientific basis for my observations - any studies, anything?

The downside, of course is that when I do get a cold, I get it bad. Which usually persuades me to stop smoking for a couple of months. --Kurt Shaped Box 15:52, 30 March 2007 (UTC)

I would guess that minor colds you've had you just dismissed as "smoker's cough", so you only noticed the serious ones. BTW, did any of the gulls you raised pick up your bad habit ? :-) StuRat 23:55, 30 March 2007 (UTC)

The gulls don't have the manual dexterity to hold the cigarette. Webbed feet, yaknow - it's like trying to smoke whilst wearing mittens. :)

I know the difference between smokers cough and a cold - I only get smoker's cough first thing in the morning. Just a few hacks to get everything moving and I'm good to go... --Kurt Shaped Box 00:25, 31 March 2007 (UTC)

I was just thinking about this over the winter, with everybody getting sick. I figure there must be some benefit to smoking, and it might be protection from colds. The usual thinking that smoking is for weak-willed, dirty, hedonistic people just doesn't convince me. There's a good reason for even the most questionable of habits. Vranak

This is interesting, because after I quit, I got sick 3 times in the period of 4 months, including a sinus infection. While I was smoking, in those 6 years (not even heavily), I got through some years without really getting sick. And I didn't smoke enough to have the smoker's cough either. --Wirbelwindヴィルヴェルヴィント (talk) 09:50, 31 March 2007 (UTC)

Maybe you gave your cold viruses cancer? Also, I've heard many ex-smokers aver that when they quit smoking they got the worst cold of their lives. One of them's doctor said it was because they had lesions in their lungs from smoking for so long, but a thick layer of mucus (a reaction to the smoke) was protecting them from the air, but when that went away, they were open sores. :( --TotoBaggins 14:40, 31 March 2007 (UTC)

I, too, have heard that when people quit smoking they tend to get bad coughs/colds for a while, then when those go away they tend to get healthier than they were. If the 'fewer annoying colds' were because of the mechanism Kurt suggested, this wouldn't actually be fewer minor colds, but fewer symptoms caused by your natural response to get rid of infection. So, some cilia die and the mucous hangs around in your lungs. Minor infections without so much coughing and hacking up mucous. Yay? No, because the infection hangs around for longer, since it is harder for you to get rid of it. Presumably, hence the worse colds when you actually get them. Note, all this is assuming the mechanism that Kurt described. Skittle 10:39, 1 April 2007 (UTC)

exemestane

i was reading (in wikkapiediea)about the effects of over use of testostrone and came across arotomase inhibitors, such as exemestane i read;

Irreversible steroidal inhibitors such as exemestane form a permanent bond with the aromatase enzyme complex

dose that mean if a person took exemestane then there production of estrogen would for the rest of there life be damaged/blocked? if so, how dose it work? —The preceding unsigned comment was added by 77.98.97.52 (talk) 16:04, 30 March 2007 (UTC).

The inhibitor works by forming a (strong, irreversible) chemical bond with the enzyme complex. Consequently, each drug molecule can permanently disable one complex. However, the body is capable of synthesizing new enzymes; in fact, this happens continuously. The old, disabled complexes will be disassembled and disposed of, and mostly be recycled into new proteins. New enzymes will be created, which are not blocked.

In other words, the drug can knock down the enzyme's activity, but eventually (barring other problems) the disabled enzyme machinery will be replaced. TenOfAllTrades(talk) 16:09, 30 March 2007 (UTC)

Suckling young

Humans generally have one baby at a time but the females have two teats. Doesn't make too much sense when viewed according to the numbers but it adds to symmetry of the body and allows for the baby to still get nourishment if there was something wrong with the one and only teat. Dogs and cats have many puppies or kittens in a single litter and the females have six (if I'm not mistaken) teats. More young, more teats, makes sense. So why do cows, who generally only have one calf at a time, have four teats? Is there an evolutionary reason? Dismas|^(talk) 16:37, 30 March 2007 (UTC)

Humans have a lot of left-right symmetry. This may have provided some useful redundancy (lose the use of an an eye, still not blind). Injury or infection to one breast still allows the mother to feed an infant. The breasts each produce a certain amount of milk (not tapping a common reservior) so there is more nutrition for the baby or babies. Twinning occurs in 1/89 of human pregnancies. Edison 17:57, 30 March 2007 (UTC)

But enough about humans, let's talk about the cows. Even though typing direct questions into Google usually isn't the best search method, I gave it a shot and found an explanation. There are several more relevant links using that search. --LarryMac 19:48, 30 March 2007 (UTC)

Interesting, thanks! I figured it had something to do with ancestors having more young. Dismas|^(talk) 20:01, 30 March 2007 (UTC)

One thing which that source implied, but didn't actually say, is that having extra nipples doesn't do much harm, but having too few does, as some offspring don't get to feed and die (usually the "runt" of the litter). So, if they had a good reason to have more nipples in the past, due to more offspring, there isn't much evolutionary pressure to reduce the number of nipples now that the average litter size has decreased to one. StuRat 23:52, 30 March 2007 (UTC)

Just a further comment with regards to humans. A hungry infant can easily drain both breasts completely of milk. Now, in theory, a single breast could be made to hold as much milk as a normal woman's two do, but the irritation caused by drawing from a single nipple would probably increase the risk of infection and would certainly increase the discomfort. Having two sources of milk also allows the mom to switch back and forth or to favour a sore side. Matt Deres 22:02, 31 March 2007 (UTC)

And then there are twins. What, you're a triplet? Tough luck. DirkvdM 18:07, 1 April 2007 (UTC)

Then you hire a wet nurse. (Unfortunately, the agency I keep calling for this service has now blocked my number, apparently they require that you actually have a baby.) :-) StuRat 01:03, 3 April 2007 (UTC)

or you could hire a baby to suckle your ... that's bound to get deleted DirkvdM 18:36, 3 April 2007 (UTC)

What's the average price to build a wind turbine?

Let say a 2-3 MWatt wind turbine. roscoe_x 18:35, 30 March 2007 (UTC)

I put "wind power 2 mw" into google and this was the first hit GE 2.5 MW WindTurbine There is an ordering information link that requires you address and contact information. I would suppose that a significant part of the price is delivery and installation, seeing as the technical specs say that the rotor blade diameter is 100 meters. That would explain those trucks you sometimes see on the road with what look like giant wings carried on their flatbeds. According to this article Wind Power FAQ there is a capitol cost of about $1.5 million per Mega watt for wind power. But that probably includes the economy of scale for a wind farm with many turbines. This company Home Turbine sells a 10 Kw home version with a 7 m diameter rotor for around $27,900. (tower extra)Czmtzc 19:53, 30 March 2007 (UTC)

The Hum

Does sensitivity to The Hum start at birth, or can it suddenly develop in adolescence or later? NeonMerlin 19:10, 30 March 2007 (UTC)

HMMMM! Good question ;-) —The preceding unsigned comment was added by 88.110.49.118 (talk) 21:02, 30 March 2007 (UTC).

Also, does it always affect both ears? NeonMerlin 00:47, 31 March 2007 (UTC)

Human sensititvity to real sounds at high and low frequencies generally decreases with age; see Hearing (sense). It's unclear whether any given report of The Hum is due to a real sound, or some internal biological phenomenon which may or may not depend on age. -- Beland 21:51, 31 March 2007 (UTC)

Finding Alien Intelligent Signals - So What?

It is often said that the day intelligent signals from outerspace are found, humanity will be somehow changed forever. But why? Quantitative evidence of alien intelligence would be, of course, a fantastic scientific discovery. But why would there be any changes on the way we live on Earth? (A face-to-face encounter with aliens would be entirely another ball game, but this is not the question here.)--JLdesAlpins 19:32, 30 March 2007 (UTC)

For one, it would discredit all the religious leaders who have claimed that we are their god's only children. Dismas|^(talk) 19:38, 30 March 2007 (UTC)

(Just a thought: It takes far less than alien intelligent signals to discredit some religious leaders--JLdesAlpins 19:46, 30 March 2007 (UTC))

Religious leaders would claim that the alien signals were fake. —Preceding unsigned comment added by Czmtzc (talk • contribs)

Or they could interpret the signals as being messages from heaven, that prove that their faith is correct. Religious leaders have a lot of creativity when it comes to explaining why contradictions with physical observations or even contradictions within the faith are no indication of the invalidity of the faith. I'm sure they would come up with explanations very quickly as to why signs of intelligent life elsewhere don't contradict any part of their faith. MrRedact 20:28, 30 March 2007 (UTC)

The idea is that suddenly we wouldn't be (oh so) alone as the only life forms in the universe able to send signals into space. Oh to receive space signals from another form of life! It's like when you first a video phone but no one else had one, and then finding out someone in Japan has one too, so there's suddenly this potential to communicate with someone with your cool new device so your friends wont all think you're a dick for wasting money on a video conferencing phone when no one else has one, except that the distance is too far, the language barriers are too great and you don't really have anything to say anyway. Except this is a new life form that will be completely impractical to hold a conversation with inside the timeframe of a lifetime. That must be oh so much more thrilling than having a face-pulling competition with a chimpanzee, or having a sei whale look you in the eye, or have a dolphin know you're pregnant before you do, or having a parrot insult your rude guest with a phrase it's never used before, for now we have another form of space-signal-enabled lifeform to communicate with. And most excitingly, we wont have the practical means to destroy its habitat. Maybe I'm too cynical, and I'm maybe I haven't answered your question at all. —Pengo 00:31, 31 March 2007 (UTC)

I am of a similar opinion to the original poster: I don't know where the idea that the discovery of extraterrestial intelligence would result in a united humanity came from, but it seems pretty half-baked, and likely little more than plot device. It assumes that people are the way they are simply because of the contents of the heads, their beliefs and so on. The material conditions of life, geography, what we eat, the state of our bodies, are what really makes our lives what they are. By comparision, thoughts and beliefs are trivial, arbitrary, and capricious. If an alien signal were discovered, so what? Add one more species to the millions we already know about. Oh, I guess some people still think that animals are a seperate category of beings. How quaint. Vranak

Yes, and from the more expansive documentaries I've seen about the universe, even if there were Aliens transmitting a signal from some distant planet - not ony would it take us freakin' ages to get there making it completely unworth it - but most of the communication would be outdated - the signal would be several years old - and if the signal was by way of LIGHT - then we're really screwed, because then the communication is reallllllly old. So our best shot is actually if aliens come visit us personally - 'cos right now it's impossible to even think of visiting their planets. Sad, very sad Rfwoolf 11:36, 31 March 2007 (UTC)

I agree that it wouldn't change much. It's like in Hitchhiker's Guide to the Galaxy where all the dolphins in the world disappear, and it's all over the news and is a big deal for a while, but a year later, you can't still have headlines blaring "DOLPHINS: STILL MISSING!". Nuclear weapons are a similar example: they could kill us all due to adventurism or simple accident, but no one seems to mind too much. --TotoBaggins 14:30, 31 March 2007 (UTC)

There are many possibilities with regard to the acquisition of advanced technologies, which may or may not be described by the message. I can certainly imagine number of scenarios where major changes in military and scientific strategy and spending would be radically changed, as the possibility of extraterrestrial attack or visitation suddenly became more likely, or as the world suddenly had a pressing desire to communicate with or visit the new civilization in a reasonable amount of time. There are also possibilities for serious conflict as various parties disagreed over who had the right to send messages back to the aliens, and what the content of those messages should be, especially given the possibility of human extinction due to a hostile alien civilization or an accidental biological contamination. There are also potential implications for radio, television, cellular phone, and other forms of communication which leak signals into outer space. -- Beland 21:58, 31 March 2007 (UTC)

It's hard to guess what would happen. Some people claim it would be the end of religion - that science would be seen as pointless - that we'd all join together to form one world government...I don't buy any of those things. Major religions would have to finally decide whether these aliens are "Gods creatures" or not - whichever they decided wouldn't change a thing for them. Scientists might be left with a feeling of "What's the point in working on new stuff if the aliens already know it and are just going to tell us the answer?"...but any communication is going to have timescales of hundreds of years. If we asked them a bunch of questions about our biggest mysteries, it could take many generations before we'd get an answer. I don't think this changes much for science. As for everyone coming together to form "one world" - again - why? There would still be a bunch of people who would deny the existance of the aliens (if you can deny global warming and claim that the holocaust didn't happen - then denying that there was a "WOW!" signal from the folks at SETI would be a breeze!). I think it would be exciting for a while - but I doubt it would change much. Remember when that Mars Meteorite was discovered and they announced that life on Mars was proven conclusively. It was news alright...the President gave a short speech about it...it was on TV for a couple of days - then drowned out by the usual crap that fills our lives. The final denial that this was proof went pretty much unnoticed. Things might be different if the aliens sent us a copy of 'Encyclopedia Galactica' of course - but that's a different matter. SteveBaker 04:52, 2 April 2007 (UTC)

Nuclear Steam Generator

I was wondering how much water could a bomb like Tsar Bomba convert into steam?67.127.97.111 23:05, 30 March 2007 (UTC)

Do you mean, if all of the energy released by said bomb was converted into heat, how much water could it boil? -- mattb @ 2007-03-30T23:27Z

The first part of the calculation is to put that energy into a useful unit. At 50 Megatons, and 4.184×10⁹ joule/megaton, I get around 200×10⁹ J or 2×10¹¹ J. Now we need to figure out how much water that will boil. The heat of vaporization of water is 40650 J/mol, so I get that we could boil about 5 million moles of water. The mole density of water is 55.49 mol/L, so I get about 90,000 L of water. Not really all that much, is it ? (Note that this assumes the water was already almost boiling temp, if it started at room temp even less would be boiled because more energy is needed to heat it up.) StuRat 23:33, 30 March 2007 (UTC)

The specific heat capacity of liquid water is about 75.327 J/(mol K), so it takes about another 5650 J/mol to get the water from room temperature up to boiling temp, or a total of 46300 J/mol to get the water up to boiling temp and then vaporize it. Otherwise doing the calculation the same way as above gives a more accurate answer of about 81.4 kL. —The preceding unsigned comment was added by MrRedact (talk • contribs) 01:16, 31 March 2007 (UTC).

So is this correct that 81.4 kL is 81.4 cubic meters of water, so it's like a cube of water ${\sqrt[{3}]{81.4}}\!$ == ~4.3 meters on the side? That seems amazingly small when you look at shots like Bikini Baker! --TotoBaggins 14:14, 31 March 2007 (UTC)

Umm ... 1 megaton is 4.184×10¹⁵ J, so I think you need to multiply the above volumes by a factor of 10⁶. Gandalf61 14:49, 31 March 2007 (UTC)

Yes, you beat me to the edit. StuRat above accidently used the conversion factor for Joules per megagram instead of Joules per megaton, and I just used his number without checking it. With that correction, the answer should actually be 81.4 GL, which is the volume of a cube 433 m on a side.MrRedact 15:13, 31 March 2007 (UTC)

Thanks for the correction, guys. StuRat 00:57, 3 April 2007 (UTC)

One has to be bold indeed to calculate out an answer like this and publish it, since it is so easy to use megagram instead of megaton, calorie instead of kilocalorie, or lightning bug instead of lightning bolt. Credits to StuRat for being the first to respond, and why is it so easier to find mistakes than to avoid them? Edison 16:29, 31 March 2007 (UTC)

Awesome thank you StuRat for that immediate responce everytime I post a thought experiment question you are one of the few who always answers it, and thank you everyone for your answers.68.120.81.220 04:38, 1 April 2007 (UTC)

The trouble is that with most of these 'back of envelope' calculations one may refer to common experience to tell you whether you are in the right ballpark - but with a problem like this one, common experience just fails you. I find correct answer just as impossible to believe as the correct one! Common sense fails when you think of something as powerful as a nuclear weapon. But jeez - a block of water half a klick per side...*WOW*! Checking your results in a problem like this is really tough. Qudos to StuRat for giving it a shot, qudos to Gandalf61 for finding the booboo! SteveBaker 04:43, 2 April 2007 (UTC)