Science desk
< May 22	<< Apr \| May \| Jun >>	May 24 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

May 23

How heavy should a healthy, adult male captive-bred Budgerigar be?

I have been told that my budgie looks overweight. I managed to get him on some kitchen scales and saw that he weighs about 55g (that might not be 100% accurate tho). According to the budgerigar article, they should weigh 30-40g. I don't know if this figure is referring only to wild birds though. Captive bred budgies are larger anyway. Anyone know how much a pet bird should weigh?

I'm not even sure how you can really tell if a bird is fat under all those feathers. He looks fatter when he puffs them up. Any ideas? --81.79.249.53 (talk) 01:34, 23 May 2008 (UTC)[reply]

Left a note with our resident bird and budgie person so he might be able to help you. Julia Rossi (talk) 02:37, 23 May 2008 (UTC)[reply]

I got your message, Julia. Thanks.

Now, a 55g budgie *could* be overweight, depending on the size of the bird. A long, broad framed 'show bird' would probably be fine at that weight, whereas a smaller 'wildtype' bird would be rather fat indeed. One indicator of obesity in budgerigars is the amount of fat on the chest. Run a finger down your bird's keel (i.e. breastbone) if he'll let you - if the bird is fat, the bone will be indented into a furrow, with flabby flesh rising on either side (think of how an 'oven stuffer' turkey looks in the supermarket). A healthy budgie will all hard muscle and fairly flat in this area. Just FYI, if the keel bone is very prominent, he's underweight and probably ill.

If you're unsure, get your veterinarian to do it. Overweight budgies can suffer from a multitude of health problems, not least lipomas, which can grow to enormous sizes in this species. --Kurt Shaped Box (talk) 20:09, 23 May 2008 (UTC)[reply]

Philosophical science-related job?

For a science project in school, we need to write a report on a science-related job. I was wondering if anyone could help me choose a job that is related to philosophy. Maybe a job that studies the existence/non-existence of God/gods or something similar? I will elaborate if you need me to, which I can definitely do, thanks! Voyaging^(talk) 02:42, 23 May 2008 (UTC)[reply]

Bioethicist? [1] --zenohockey (talk) 03:19, 23 May 2008 (UTC)[reply]

God-wise, there's lots of interface with cosmology, though my impression is that this is elaborated upon by philosophers and theologians more than working cosmologists.

Also see philosophy of science and philosophy of technology. --zenohockey (talk) 03:22, 23 May 2008 (UTC)[reply]

Don't forget History and philosophy of science or history of science. Someguy1221 (talk) 03:29, 23 May 2008 (UTC)[reply]

Re cosmology—I should have mentioned this first—some writers think that they can prove (or at least bolster the argument for) the existence of God by examining the facts of the physical universe; some think just the opposite. --zenohockey (talk) 03:31, 23 May 2008 (UTC)[reply]

Unfortunately, the existence/non-existence of gods is outside the purview of science. It's unfalsifiable (see Russell's teapot). Bioethics is probably the best, current one; however, I could see a field on the ethics related to the use of robots, AIs and the like. — The Hand That Feeds You:^Bite 03:37, 23 May 2008 (UTC)[reply]

Thanks so much for the answers, guys! I'm now trying to decide between bioethicist and cosmologist. Which is more based in science, and thus have more factual information to write about? Which would you say is more important to the world and life in general? Thanks again! Voyaging^(talk) 03:56, 23 May 2008 (UTC)[reply]

I've always assumed medicine to be a good career for science and ethics ;) Regards, CycloneNimrod^Talk? 08:51, 23 May 2008 (UTC)[reply]

That said it doesn't really have anything to do with religion. That should be duly noted :P Regards, CycloneNimrod^Talk? 08:52, 23 May 2008 (UTC)[reply]

You'll deal with more actual science by going into philosophy of science. Even more science is involved in being a scholar in Philosophy of physics or Philosophy of biology. To see if you're really interested in those two subfields I'd suggest books like An Introduction to the Philosophy of Physics: Locality, Fields, Energy, and Mass by Marc Lange and Making sense of evolution : the conceptual foundations of evolutionary biology by Massimo Pigliucci and Jonathan Kaplan. Both are rigorous treatments of philosophical issues surrounding both sub-fields in philosophy. They also are good examples of the level of comfort you need to have with the associated science topics in order to make contributions to the sub-fields.--droptone (talk) 12:10, 23 May 2008 (UTC)[reply]

As a side-branch of bioethics, have you thought about looking at genetic counselors? They have to deal with actual genetics all the time, and attempt to explain the implications of it to the "common man" in terms that don't actually predestine what choices are taken (they are, in theory, non-directive). The profession itself grew out of the old tradition of family counseling done for the purpose of eugenics, but tried explicitly to go in a different direction than the eugenicists did. Anyway, it is an interesting and thorny issue, in my opinion, with lots of potential science to be talked about. --98.217.8.46 (talk) 14:50, 23 May 2008 (UTC)[reply]

Of bioethics and cosmology cosmology is the more scientific by far, but I don't see how cosmology touches on religion or philosophy any more than any other science does. Maybe it gets more attention from religious groups than most sciences in the present era, but the interest isn't mutual. Cosmologists are far too busy right now coming up with precise numerical models and analyzing the flood of data from experiments like WMAP to philosophize about what it all means. Every field of science has intruded on religious territory in some historical era just as much as cosmology is doing now. Religions try to explain the same world that science does, and when scientists come along and find better explanations the religions are forced to retreat into figurative interpretations of texts they'd formerly interpreted literally. As a result religions become increasingly divorced from empirical reality, but it's not in the nature of religions to be like that, it's just a position they've been forced into. Modern cosmology would have been considered utterly at odds with the religious beliefs of a thousand years ago; today they coexist uneasily, with various religious groups trying to find confirmation of their beliefs in cosmology; in the future I suppose it'll be as uncontroversial (and unphilosophical) as the craters on the moon and the irrationality of the square root of 2. -- BenRG (talk) 20:30, 23 May 2008 (UTC)[reply]

Fields such as artificial intelligence and consciousness studies have a strong philosophical bent to them. ike9898 (talk) 17:07, 23 May 2008 (UTC)[reply]

Philosopher of science should be just fine for your purposes. Here are som folks involved in consciousness research to help give you an idea of what the field is about: Vilayanur S. Ramachandran, Patricia Churchland, Daniel Dennet, Benjamin Libet

Philosophers are a waste of space. They make wild guesses based on the flimsiest of arguments that last only until we have REAL scientists come in and provide a REAL answer. "God Exists" is a fundamentally unfalsifiable claim - but how many thousands of Philosphers have debated it over how many millenia? In the field of cosmology, they have absolutely nothing to contribute. In the field of Bioethics they are making arbitary distinctions - which are (at best) based solely on what the general public seem willing to tolerate - a simple opinion poll would be a better way to decide. It's becoming a case of the "Philosophy of the gaps" (analogous to the "God of the gaps"). Bah! Fire the lot of them and spend the money on a shiney new particle accellerator. 70.116.10.189 (talk) 13:55, 24 May 2008 (UTC)[reply]

Personally, I think dollar-for-dollar it'd be easier to argue philosophers are more useful than particle accelerators, if you're accustomed to thinking in terms of economic analysis. What have particle accelerators gotten us, lately? Not a whole lot, not since the 1940s anyway. Philosophers can at the very least sell books, and quite a few people have no doubt decided to pursue their lives differently on account of said books, not to mention the use of philosophy as a convenient step on the way to a legal career. (And let's not get into those border cases, the people who are labeled as "scientists" but would be nowhere without their knowledge of philosophy, like our friend Einstein.) In any case, I doubt firing all the philosophers and pooling all that money would pay for very much—philosophers are cheap, and there aren't all that many of them. The LHC is going to cost at least $5-10 billion USD—far more than all humanities research in the world put together, without question—and will we get anything from it other than a potential confirmation of a few esoteric theories that have no real-life consequences? (Other than, of course, helping to pay for a few thousand researchers for a few years, who may or may not turn out something useful over the course of their careers.) I don't read professional philosophy journals—they are unreadable to all but the most initiated—and I don't think it gets terribly close to any profound truths these days (but then again, neither does most science), but I think the idea that scrapping philosophy is foolish and ignorant. --98.217.8.46 (talk) 19:44, 24 May 2008 (UTC)[reply]

Yeah, right we don't need a supercollider, we'll send our physicists to Europe. Oops, can we? And what about young people from abroad wanting to go study? U.S. or Europe - who's got the tools? Europe does. But who needs foreign students. Our own students will surely still want to go for physics with the nation so far "ahead" towards the bottom, won't they? Nope they're studying liberal arts and philosophy. I hope the Chinese will buy lots of books, because we'll have to sell them something to buy their engineering products. I know particle physics is a far cry from engineering, but things can't trickle down from the top if there is none. Just deliberating philosophically on how technologically advanced we are won't help keeping/getting us there. If we're not willing to build any monuments we can't bask in their glory. Sorry if this is a bit incensed, but you lit a very short fuse there! —Preceding unsigned comment added by Lisa4edit (talk • contribs) 08:05, 25 May 2008 (UTC) darn bot --Lisa4edit (talk) 08:07, 25 May 2008 (UTC)[reply]

If you want engineers, ask for engineers. Don't ask for particle physicists. If you want practical results, ask for people to study practical things. Particles physics is not, and has never been, practical. All of the things that were practical about it quickly were "reduced" to engineering questions. People love the idea of particle physics as a romantic scientific enterprise, but in terms of anything other than growth of esoteric knowledge, it is not very useful. People don't pine for chemists or civil engineers, but they have a lot more day-to-day effect on our lives than particle physicists do. Particle physics is not too far up from being very, very expensive philosophy, is all I'm saying. --98.217.8.46 (talk) 20:23, 25 May 2008 (UTC)[reply]

Who where the first people with acne?

I would like some information, possibly links to websites or names of specific books as to who the first people in human history, known/recorded history that is, with acne were. Thanks.75.163.86.247 (talk) 03:06, 23 May 2008 (UTC)Xolotl[reply]

Our article on acne says that several Egyptian pharoahs had the condition. It doesn't cite a source for that claim, unfortunately. — Dulcem (talk) 04:25, 23 May 2008 (UTC)[reply]

I doubt there's any evidence to support the idea that acne is anything "new"; it probably exists outside of our species as well, but there's not as much money to be made selling Stridex medicated pads to gerbils. That is, I think a question that asks when it originates is meaningless. A question that asks when it was first recognized, on the other hand...

Atlant (talk) 12:48, 23 May 2008 (UTC)[reply]

It's worth bearing in mind of course that humans are one of the only land mammals with very little hair/fur on most of their skin. Clearly even if a gerbil or whatever has acne, it's going to be a lot harder to see because of the covering of hair/fur and the hair/fur may retard the growth. Even apes which have significantly reduced fur covering the face may not have a smooth face and with a face like this Image:Pongo pygmaeus (orangutang).jpg, Image:Young male chimp.png, Image:Young male chimp.png, Image:Chimp.jpg acne is probably not going to make a big difference anyway (same with say, an elephant)... Also all (most?) animals lack the long puberty period humans go through where human levels fluctate widely and acne most commonNil Einne (talk) 21:38, 23 May 2008 (UTC)[reply]

They probably escape it due to nutrition[2] not having a culture that emphasises dairy intake. Julia Rossi (talk) 06:28, 24 May 2008 (UTC)[reply]

Would you care to post some proof that there's an acne/dairy link? --70.167.58.6 (talk) 15:01, 26 May 2008 (UTC)[reply]

Cats get it. So do dogs. --jpgordon^∇∆∇∆ 14:12, 24 May 2008 (UTC)[reply]

Plausible Theory

All right well I have set my sights on the beautiful dwarf planet, Pluto. And then I came to a theory of my own. Because Pluto has some terrestrial parts to it. I thought that maybe Pluto use to be either one part of another terrestrial planet or was a terrestrial planet that got knocked off orbit in the very early stages of the solar system. Would this theory be plausible?Rem Nightfall (talk) 04:37, 23 May 2008 (UTC)Rem Nightfall[reply]

Outside the orbit of Neptune is a belt of small rocky objects (like Pluto) called the Kuiper belt. Pluto is part of this belt and has similar origins to other objects in the belt, it just happens to be a particulary large object in the belt. These objects (like those in the Asteroid belt never coagulated like the terrestrial planets did. I'm not sure why this is, I think it has to due with ratios orbital radius and speed.. --Shniken1 (talk) 05:46, 23 May 2008 (UTC)[reply]

Pluto isn't even the largest, it's just the first one we found. As far as I know, that's its only claim to fame. --Tango (talk) 12:44, 23 May 2008 (UTC)[reply]

Aside from being awesome, of course. --98.217.8.46 (talk) 14:45, 23 May 2008 (UTC)[reply]

Xena can kick Pluto's butt anytime! It's bigger has a more sensible orbit and a proper sized moon. AND a stupid cartoon dog stands no chance against an Amazon princess when it comes to "awesome". 70.116.10.189 (talk) 02:56, 24 May 2008 (UTC)[reply]

Cartoon dog? Surely you jest! --98.217.8.46 (talk) 03:03, 24 May 2008 (UTC)[reply]

Yes, I do jest...and in any case, the dwarf planet Xena is now officially known as Eris - the Greek goddess of strife and discord...who'd stand no chance in a stand up fight against Pluto (whos' more familiar Greek name is 'Hades', the God of Hell). But Xena is still bigger than Pluto. 70.116.10.189 (talk) 13:39, 24 May 2008 (UTC)[reply]

Size matters little in the wars between Gods! --98.217.8.46 (talk) 19:55, 24 May 2008 (UTC)[reply]

What I meant was what if Pluto use to be a bigger planet. What if the Kuiper Belt had been together in the younger solar system, but something disrupted it only leaving a small size planet instead of the large planet. What if they couldn't form with each other or something. Also I love Pluto its a fascinating planet. Its maybe the only planet we don't know about. Pluto is a wonderful planet may it be small or not.Rem Nightfall (talk) 15:48, 24 May 2008 (UTC)Rem Nightfall[reply]

What will happen if a virus leaves its host cell for a long time?

and what will happen in terms of its chemical structure? - Justin545 (talk) 06:54, 23 May 2008 (UTC)[reply]

Presumably it wouldn't be able to replicate as it has no access to RNA, but i'm not sure if it would stop functioning (it certainly won't 'die' since it isn't alive in the first place).

A virus can surely "die", that is, lose the ability to replicate in a host. I believe most animal viruses live for very short periods--hours at most--outside the host, unless they are being coddled in a lab. Woodlore (talk) 11:03, 23 May 2008 (UTC)[reply]

Well, there is dispute in the scientific community to whether or not viruses are actually "alive" in the biological sense of the term. However, viruses can certainly be rendered inert or destroyed if they are left exposed outside of the body. Disinfectants, ethanol, bleach etc.. can certainly disrupt the lipid envelope of the virus and denature its protein coat and inner nucleic acids. Such things will also occur over time without the use of exogenous chemicals. Wisdom89 _{(_T / ^C)} 20:03, 23 May 2008 (UTC)[reply]

It's actually the lay community that's concerned with the notion of whether or not viruses are "alive"; scientists pretty much know that it's not a useful term to be using about viruses. As Wisdom points out, what happens to a virus is a direct result of its environment: many remain unchanged, and remain infective, for quite a period of time. Others rapidly become non-infective. But heat and the chemical environment can change the speed at which this happens. (The virus, btw, can't replicate because it lacks ribosomes and has no way to produce proteins - that (and not lack of RNA) - is the reason that viruses are obligate intracellular parasites.) - Nunh-huh 20:10, 23 May 2008 (UTC)[reply]

The "Tobacco Mosaic Virus" is the one they always teach about in school. When you extract it from it's host, it crystallises into rather gorgeous crystals of completely inert-seeming stuff. There you have something about as inert as you could imagine..."dead"...like a grain of salt. But let it dissolve in water and spray it onto a plant - and it's back to being an active, reproducing, disease-causing agent. It's right on the edge between being a "poison" and a "creature". Humans are very interested in putting up hard and fast barriers between one kind of object and another - where often, no real distinction exists. Consider "Planets"...is Pluto a "planet"? Well, the truth is, we shouldn't care - it's a big rock or a small world - but there is no hard line between rocks and worlds in nature - we see every possible value inbetween. The same is true for "life". Dogs and cats are obviously "alive" and crystals of NaCl (table salt) are "not-alive"...but the Tobacco Mosaic virus sure behaves like it's alive when it's taking over a plant...but when you crystalise it, you pretty much have to say it's a bunch of inert chemicals...but it's not "dead" because you can easily revive it. So viruses are to the "alive/not-alive" debate just as Pluto is to the "Planet/Not-planet" debate - whatever we decide to label them is entirely a linguistic convenience and tells you nothing whatever about what's going on in the universe. 70.116.10.189 (talk) 02:50, 24 May 2008 (UTC)[reply]

Whether weather

Climatologists have stated in the past that global warming will bring about an increase in hurricanes, as documented for this year by the NOAA (approx. 9 to 12). Yet Knutson says that global warming may well bring about fewer hurricanes. Who's right, and how can such arguments be proven?--WaltCip (talk) 14:53, 23 May 2008 (UTC)[reply]

Such things can't be proven - even waiting and seeing won't work, since there's no way to know it's global warming and not something else, or even just coincidence. The best we can do is gather evidence to support one view or another, but proof doesn't exist in science. --Tango (talk) 15:16, 23 May 2008 (UTC)[reply]

Scientist run weather models (see Numerical weather prediction) But weather is such a complex, chaotic system that, as Tango says, you can't be sure what happened or is going to happen. It's not like you warm air here, it's going to get warm. The warm air may rise and change some arctic flow pattern and all of a sudden it gets a lot colder instead of a bit warmer. You can look at lots of measurements but it's pretty much impossible to say if A caused B and B then caused C or if A caused C directly and B just happened at the same time. So it's not like one scientist fed the correct data into his model and is right and the other made a mistake and is wrong. Both models are probably "correct" and either one has a bigger influence or they may even both apply in alternate years or months. Forecasters have become pretty good at finding patterns and coming to a conclusions about what might happen next that then actually applies. But we can never be sure that it wasn't something else that caused the observed results, or just coincidence. --71.236.23.111 (talk) 18:03, 23 May 2008 (UTC)[reply]

Global warming means more hurricanes: Global warming puts more energy in the atmosphere, leading to warmer water in the hurricane-forming regions. Warmer water makes it easier for tropical storms to form and reach hurricane strength, so there are more hurricanes.

Global warming means fewer hurricanes: Global warming puts more energy in the atmosphere, allowing non-hurricane methods to distribute heat efficiently. The water in the hurricane-forming regions doesn't get as warm as it does now, and it's harder for tropical storms to form and reach hurricane strength, so there are fewer hurricanes.

There's no way to know which will happen. There are numerical simulations that support both, and it's entirely possible that something else entirely will occur. --Carnildo (talk) 19:40, 23 May 2008 (UTC)[reply]

Incidentally, could someone take a look at Political effects of Hurricane Katrina and Alternative theories regarding Hurricane Katrina. These two sources appear to present the idea that global warming has contributed to an increase in the number and intensity of hurricanes in recent years as fringe theories. Yet from Effects of global warming from what I can tell this is not the case, global warming having a contributing effect is definitely accepted as a possibility by a number a scientists and there was even more acceptance of the idea at the time, in particular from Kerry Emanuel et al's research (although he has now done further research which has lead to a rethink, this was not the case at the time of Hurricane Katrina) Nil Einne (talk) 21:23, 23 May 2008 (UTC)[reply]

It's tricky - we can predict 'climate' but we can't predict 'weather'. We know for 100% sure that CO2 traps sunlight. We have a reasonable estimate of how much - so we can say with an amazing degree of certainty that the earth will get hotter if there is more CO2 up there than there should be. But then we get into the ugly details. We know (for example) that increasing temperatures will melt polar ice. But know exactly how much is tricky because it depends on how the extra heat is distributed - will it get a lot hotter at the equator - but hardly any hotter at the poles - or will it be the other way around? It's tough to figure out because it depends on wind patterns, ocean currents and deep ocean currents - and once things get hotter, those will move around. If we don't know accurately how the heat will be distributed, we can't easily calculate the rate of polar ice melting. But worse still, as the polar ice does melt, it makes the planet less 'shiney' so yet more energy from the sun is absorbed by the dark oceans - and now you have solar heat intake going up much faster than you'd predict from CO2 levels alone. These lesser details get harder and harder to predict. We constantly hear about how the polar ice sheets are retreating much faster than scientists predicted...and that's because this math is hard. We knew that they WOULD be melting - that much was for sure - but exactly how much is almost impossible to know. The situation with hurricanes is even worse - those depend on even more subtle things - and there are numerically so few of them each year that randomness can easily overwhelm the underlying trend of increase or decrease. If there were (say) 15 of them last year and 18 this year - is that a 20% increase in one year - or is it just luck? So scientists make their computer models and run them to figure out what might happen - but if someone misses a key factor (like maybe the amount of salinity brought up from deep ocean super-haline layers by the change in ocean currents due to some yet other effect) - then their model won't predict things accurately. So it's true to say that science doesn't have a DETAILED picture of what will happen. However, we can be absolutely certain of the basic fact - which is that more CO2 means more heat being absorbed - which MUST mean that the planet will heat up. Exactly how fast and with what measure of impact on human society and biodiversity...those are open to debate. 70.116.10.189 (talk) 02:36, 24 May 2008 (UTC)[reply]

Models have to be tested against reality, for which you need enough observations. Hurricanes have been observed by satellites for 35 years and there are only a few every year. That gives a way too narrow statistical basis, unless there is a really strong change. Such as hurricanes appearing where they have not appeared before, which I've heard has happened off the coast of Brazil. Anyway, abovementioned Kerry and another researcher have both made a model that seems to be (partially) supported by the observations, and both predict fewer hurricanes in the Caribbean, especially small hurricanes. But they also predict that the big ones will become bigger. My layman's interpretation is that hurricanes form less easily, but when they do, they suck in more energy. However that may be, that is bad news. The little ones we and nature in general have adapted to. We can live with those. But it's the big ones that cause the trouble. And if they get bigger, they're megadisasters waiting to happen. Maybe Katrina was jut a foretaste. DirkvdM (talk) 19:06, 24 May 2008 (UTC)[reply]

Record Cumulonimbus

What is the highest top recorded for a cumulonimbus cloud? Sancho 19:05, 23 May 2008 (UTC)[reply]

Carpet / R-value (insulation)

Here we say that "per inch" values are not allowed and here they give thermal conductivity (not R-value) "per meter". In R-value (insulation) we link to [3], where they claim that a not further specified "carpet with fibrous pad" has more than 50% of the R-value of 2.54cm thick "Rock Wool Batt", although carpets are so thin and allow air exchange... Why dont they put carpets on the roof then? Can someone explain me what I understood wrong here? --Homer Landskirty (talk) 19:20, 23 May 2008 (UTC)[reply]

The problem is that the measurement for bulk material is not linear. Twice the thickness doesn't necessarily give you twice the amount of insulation. Imagine (for example) aluminum kitchen foil that's much less than a hundredth of an inch thick. It reflects a lot of heat back to the source and thus performs the task of home insulation reasonably well (my roof is decked inside using a product called "CoolPly" which is plywood laminated with some kind of reflective metal foil). But a solid slab of inch thick aluminum is not significantly better than 100th of an inch of the stuff. So describing the R-value of aluminium foil "per inch" is horribly deceptive because it would make it seem 1000 times better than it really is. However, other materials (insulating glass wool for example) have insulation properties that do get better the thicker they get. My house has three layers of the usual 4" thick wool insulation - and my roof's R-value is three times better than my neighbours house which has only one layer. In that case, you most certainly want to specify the R-value per inch of thickness. Expressing "thermal conductivity" in "per-meter" (or "per-inch") units is fine because thermal conductivity (even for aluminium) is directly proportional to the thickness of the material. The problem is that "R-value" is NOT a direct measure of thermal conductivity because it includes things like infrared reflectivity and the ability to limit heat loss by preventing the physical movement of air (convection).

Now - as to the question of carpet...remember that 2.54cm (an inch) of rockwool doesn't give you much insulation. As I said - I have the stuff stacked literally a foot thick in my attic. To do that with carpet, assuming it's 50% as good as rockwool as you say. I'd need 24 layers of the stuff with "fibrous pad" also 24 layers thick. But carpet is heavy and it's a lot more expensive than rock wool! Even cheap carpet is a couple of bucks per square foot. At 24 layers thick, that would add 50 bucks per square foot to the cost of my 3,000 sq.ft house - that's $150,000 on roof insulation! That's more than the entire house cost to build!

So that's why they don't use carpet! 70.116.10.189 (talk) 02:20, 24 May 2008 (UTC)[reply]

I thought is was because of this guy! But nicely explained. I'd also add the concept of air infiltration; this is one of the things that makes spray foam insulation so effective: It has myriad air spaces, but no or very limited mobility for all that air.

Atlant (talk) 15:51, 27 May 2008 (UTC)[reply]