Wikipedia:Reference desk/Archives/Science/2011 December 11

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December 11

Load bearing capacity of 2x6 box beam

I'm thinking of making a building and using a box beam of 2x6s as the foundation. The box beam would be laid on top of 10 inch concrete posts, with an anchor bolt in the concrete. The span between the posts needs to be 8 feet. The box would be constructed by laying one 2x6 flat on the posts, with two 2x6s laid on edge on top of the first (the overlap would be on the bottom, not the sides, so that the beam would measure 8.5 inches high). The top of the box would be the sole (bottom) plate of the stud wall. The box beam would be screwed together, not nailed. Does this configuration have sufficient load-bearing capacity? From what I can tell, for example here, it would be okay, but I would like an expert opinion. B^e——C_ritical 01:14, 11 December 2011 (UTC)

I believe there's a problem with putting wood directly on concrete like that. Water finds it's way to the top of the concrete (not sure why), and that causes the wood to rot. StuRat (talk) 02:50, 11 December 2011 (UTC)

Box beams are rarely worth the trouble, especially for such a short span. You don't specify what is being borne (one story, two stories, tributary area, loading conditions, seismic zone, etc, so there's no way to evaluate adequacy (nor should we be giving specific engineering advice here anyway). The configuration you describe is not an efficient use of wood; you'd spend about the same amount of money and much less time using a properly sized engineered product like laminated veneer lumber in this condition and wouldn't have to worry about shear failure at bearing points, to which your box beam would be prone. Box beams are most efficient where the sides are thinner (as in plywood), but have trouble with shear force and are hard to satisfactorily fasten together. Screws are not satisfactory substitutes for nails - they're much weaker in shear than an equivalent nail (shear is the critical load here, not withdrawal, which is what screws are good at dealing with), take longer to install (making you prone to not using enough - you need a ton of closely spaced fasteners) and will prompt tough questions from the building inspector. Also, as StuRat points out, you have to use treated wood in contact with concrete, and treated wood tends to be wet and inconsistent in strength. There are metal connectors that will stand wood off the column and anchor it at the same time.

You have two shear conditions here: vertical shear, in which the weight of the building is transmitted to the column at each support, and horizontal shear, an internal stress that is generated by bending forces, which must be resisted solely by your fasteners: hence the concern about using screws. Box beams are more appropriate over very long spans where solid lumber can't be made long enough or deep enough - a typical box beam would be in excess of 24" deep, where it can maximize the benefit of a deep built-up assembly. Shallow box beams don't make efficient use of beam depth.

For the beam assembly you're better off using multiple 2x8s or 2x10s (7-1/2" and 9-1/4" high, respectively), or engineered lumber if that won't work. Way less work and much stronger and more consistent that way. Acroterion (talk) 03:13, 11 December 2011 (UTC)

Wow, people are here :D Thanks for the replies. Okay, to specify more: It's like a barn, 30 feet by 70 feet: the walls will be 12 feet high with 2x6 studs and OSB sheathing on both sides. Single story, with 2x4 scissor trusses spanning 30 feet between supports. Each truss weighs about 120 lbs, so the foundation beams would bear about 180 lbs for the trusses (3 x 60 for the weight carried by the 3 studs which are not sitting directly on the concrete posts, that's the weight to be actually carried), plus 19/32 OSB on the roof and metal roofing, siding and 7/16 OSB sheathing inside and out, and 1x paneling inside (no drywall), studs and insulation. There won't be any floor, at least not suspended from the foundation. The floor will be brick or maybe Compressed earth block laid on the dirt inside. I would guess about 300 lbs on each foundation beam, but I have no way to accurately calculate it. The rigidity of the wall probably plays into it a great deal, the 7/16 OSB will be screwed to the studs, and it will overlap and should distribute weight. I think I have a lot more strength in this building than most, but it is big and flat and will catch the wind (no earthquakes).

The suggestion about using Laminated veneer lumber or some other such product is excellent and I'll look into it. I'm a very green carpenter who has taken on a big project, and I don't have much help, just someone to hold the end of a board or something. Will also look into having the foundation beams set up from the concrete columns, as that would eliminate the need for treated wood (the bottom 2x6 was going to be treated in the box beam). I think you are saying I should use 4 of these nailed together? Question: would this nailed to the long (6 inch) side of this work? Or perhaps if I could get an OSB 6x6 beam and then nail a treated 2x6 on it, would that work?

I understand what you say, that screws have much less shear strength than nails. I'm planning to use screws to build the walls: assemble each piece on the ground and lift it up, using 3 inch screws (the gold kind, maybe some of the black ones, I guess they are drywall screws) through the plates into the ends of the studs. This was approved by a former contractor at Home Depot, but not sure they are expert. Is that okay, or do I really have to use nails? No nail gun. I have some steel straps and also hurricane ties for the trusses. B^e——C_ritical 18:56, 11 December 2011 (UTC)

So you're doing what amounts to a grade beam on piers around the perimeter. Bear in mind that live loads (even in snow-free places there's still a minimum live load requirement) need to be accounted for too. I'm not going to do an analysis for you (unless I get to send you a bill), but it appears to me that there needs to be internal lateral bracing between the long walls, particularly if you're in any kind of wind zone. Your grade beam can be done with multiple pieces of plain treated lumber with a 2x6 sill laid on top. If you use drywall screws (the black ones that the guy at HD says are OK) to do anything but install drywall, you will regret it Nobody ever uses drywall screws for anything but drywall on one of my projects more than once, assuming their employer doesn't fire them first for having to rip it all out and do it over. They're crap and will rust and fail, and the building inspector will make you take them all out and re-do it all. That alone is enough to discredit any advice the HD guy offers. Don't use screws. Nails are great, and for a project of this size a framing nailer and a compressor (a rented gasoline unit if you're away from power) will make the job infinitely easier and faster, and will allow you to use enough of the right fasteners. Worth every penny. Nails are cheaper, faster, stronger and more durable. I'd suggest running your plans by a local architect or structural engineer - an hour's review time would be worth it. Acroterion (talk) 19:50, 11 December 2011 (UTC)

Actually the screws are the yellow ones, they call them "gold screws." That's what he said would work, I was just thinking I might use some black ones where not exposed to water. But you've convinced me to use nails where there is a need for high strength. But question: if they aren't going to rust, could the gold screws be used instead of toenailing? What kind of internal lateral bracing could I use that doesn't involve walls? I want the wide open space. I could put some railroad ties in the ground and strap them to the wall at intervals on the outside. You don't think all the OSB and hurricane ties will be sufficient to prevent racking? Looking at barns on Google, they don't seem to need it. How is what I'm doing different? [1] Perhaps they are built where there isn't much wind? We do get fairly high and gusty wind, but not hurricanes or tornadoes or earthquakes. Trailer houses do not seem to blow over if you merely put them on blocks. I'm not meaning to ignore anything you say... but it would be difficult for me to get anybody local to help.

And BTW, I'm getting emails saying it's great I actually got an architect to comment, with which I completely agree :D B^e——C_ritical 23:33, 11 December 2011 (UTC)

Disclaimer note: All I'm going to do here is to respond to potential problems or misconceptions, not to say "OK". This is getting too far into engineering advice, and is moving past the remit of the reference desk. It is your responsibility to make sure things are right, which means getting your design checked by someone who is in a position to properly evaluate the circumstances.

The gold screws are marginally better than drywall screws, but not much. I can drive three 12-d toenails with a framing nailer in two seconds, accurately, while supporting the framing in place with my free hand. Three equivalent screws would take about a minute, both hands, a lot of battery power, and significant quantities of bad language, and they'd still be inferior to three good, galvanized nails. Structural-quality screws in solid lumber are hell to drive.

Barns tend to have internal frames every 15 or 20 feet, with a good bit of diagonal knee bracing. All those barn interiors in the link feature intermediate frames and diagonal bracing. They're really pretty rigid. You really can't build something and hope the wind won't blow. You can brace the walls to the roof trusses, but the trusses need to be specifically designed to take the stress. The truss fabricator should be able to point you to an engineer who can give your design the once-over and suggest improvements; such bracing is in fact something I'd refer to an engineer if I was doing the design, so you definitely should - it's a specialized skill. Bracing shouldn't amount to a significant amount of lumber or obstruction. Acroterion (talk) 02:46, 12 December 2011 (UTC)

I see. Yes, already have 16 d nails on the list. And that's a good idea to talk to the truss people about it. I hadn't actually thought of that, they are probably the only people I could ask (hundreds of miles away). One last question though, what kind of plans do I have to give an engineer so they won't be pissed off at me? Professional blueprints are pretty much out of the question. I can make a pretty understandable drawing with graph paper. I know this is all very irregular, but I do have an irregular situation and really can't help it. I could easily install knee bracing from the trusses to the studs I think, though I'd have to build the ceiling around it. Is that the kind of thing you're talking about?[2][3] It looks like it would be an extremely strong insurance against racking due to wind. I'm not concerned that the wind will be strong enough to move the entire house sideways. There is sufficient precedent in this area to preclude that as possible (it doesn't blow trailers off their blocking, even though they are just sitting on concrete blocks). But racking is what I don't know about, and if knee bracing is standard to prevent that, then I think the wind problem is solved. I would need to ask the truss people where to attach though. Sound right? Thanks for all your knowledge and help. B^e——C_ritical 03:54, 12 December 2011 (UTC)

Yup, that's an example of appropriate lateral knee bracing (in your building your OSB sheathing will substitute for the Y-bracing). 70 feet is much too long to build a hollow tube without bracing. I'm not concerned about the whole building moving, I'm concerned about the middle of the long elevation bowing (which would pull the end walls in and precipitate collapse from the middle out), since the end walls are too far away to be of any help. As for drawings, no architect or engineer will complain about a neat concept sketch on graph paper: it's way better than what we usually see. Professional drawings are our job, not yours, you need not worry about that. Acroterion (talk) 13:35, 12 December 2011 (UTC)

Cool. Acroterion, thank you so much you've really been an amazing help. It was exactly the info and correction I needed. B^e——C_ritical 22:33, 12 December 2011 (UTC)

Purple sky

Two questions in one, a twofer.

1. I just want to make sure this is true. Mars's sky is red because of light scattering, similar to the effects of light scattering on Earth's atmosphere, right?
2. What would it take for an atmosphere to appear light purple in colour? Would it need to be composed of more gasses, to have a distinct gas, to have a thicker atmosphere, to have a thinner atmosphere, for the planet to be closer to the sun than Earth, what?

99.242.47.208 (talk) 01:21, 11 December 2011 (UTC)

1) I don't think Mars atmosphere has much color to it at all. The planet itself is red because of iron oxide (rust), and some of that blows into the atmosphere, giving it a slight red appearance, I imagine. StuRat (talk) 02:38, 11 December 2011 (UTC)

2) The sky looks purple at dawn and dusk, so less light would presumable make it look that way all day long. Perhaps placing the Earth farther away would do the trick, although too far and the atmosphere would liquify. A much thicker atmosphere would also block out more light, but, again, too thick and the pressure would cause the lower parts to liquify and push the higher parts far enough up that it would no longer be held in place by gravity. Alternatively, if the Earth was the same as it is, but tidally locked to the Sun (one side always facing the Sun), then there would be a ring on the Earth where it would always be dusk, and always have purple skies. You would have temperature extremes to deal with, though. StuRat (talk) 02:40, 11 December 2011 (UTC)

2) Note that the above would produce a dark purple. If you insist on light purple, then you might want a planet with a slight amount of iodine gas in the atmosphere: [4]. StuRat (talk) 05:52, 11 December 2011 (UTC)

Just a few points and corrections to the OP's and StuRat's comments:

1. Mars's sky is indeed very red. This is due to, as Stu mentions, the large amount of iron-oxide dust which is constantly suspended throughout the atmosphere, even outside of its severe dust storms. Earth's sky is blue due to Rayleigh scattering, which is also present in Mars's atmosphere, but to a much lesser extent than on Earth due to its lower atmospheric pressure. If there were no dust in Mars's atmosphere the sky would be dark blue.
2. I don't believe I would describe the sky at sunset as appearing "purple". The sunset does not appear the way it does due to "less light". It is because Rayleigh scattering preferentially scatters the shorter wavelengths of light (towards the blue/purple end of the spectrum), so as the sun's light passes through more and more atmosphere towards sunset, the light appears more red, which is on the opposite end of the visible spectrum. Clouds may appear purple due to a combination of blue light from above and red light from the horizon, but there is no way that the sky itself at sunset can be purple.
3. I don't believe Rayleigh scattering alone can give you purple. The problem is the eye is much less sensitive to purple wavelengths than bluer wavelengths, enough blue light will always be there to make the sky appear blue rather than purple. This can be seen in high-altitude photos taken here on Earth (like this one). The sky just goes from blue to dark blue to black; as you decrease the amount of atmosphere to scatter the light, there is just no semblance of purple in there.

I can imagine some quite exotic planet with a large amount of gaseous iodine as Stu mentions, or some strange mixture of hydrocarbons that appear purple may be possible, but it does not exist in this solar system, and it would have to be quite an unusual set of circumstances to get an atmosphere like that. -RunningOnBrains^(talk) 07:03, 11 December 2011 (UTC)

1) I apparently made a distinction which you didn't, when I said the atmosphere of Mars has very little color but the rust particles suspended in it are red, while you lumped them together and said "the sky is red".

2) The sky looks dark purple to me at dusk. Why wouldn't it, since Rayleigh scattering would favor that end of the spectrum when sunlight passes through more air ? The ability to see red versus blue in low light levels might possibly vary by individual, skewing our perceptions. While red and purple are at the opposite ends of the spectrum, this is irrelevant to our visual perception, where they are adjacent on the color wheel.

If you look at the pic of the iodine gas I provided, it's very purple, so you wouldn't need much to change the color of the atmosphere, perhaps parts per billion or trillion. Looking at your pic, I see a thin brownish-yellow layer. I wonder what causes that. StuRat (talk) 15:21, 11 December 2011 (UTC)

Guys, you're confusing purple with violet. There's no such a thing a a purple wavelength. Purple is made by mixing red light with blue (or violet) light. Violet doesn't look anything like red. Purple is adjacent to red in the color wheel because it has red light in it. Violet can be obtained by Rayleigh scattering. Purple cannot. Dauto (talk) 16:17, 11 December 2011 (UTC)

I'm not sure the OP is making the distinction. StuRat (talk) 19:07, 11 December 2011 (UTC)

To me, it doesn't matter. Purple and violet are similar enough in colour. In fact violet is probably better. 64.229.180.189 (talk) 01:47, 12 December 2011 (UTC)

I appreciate the idea behind this distinction, yet, a color is defined only as how something is perceived by human vision. Violet is more than simply blue - for some reason it seems purple despite the lack of genuine red. If you want to speak in terms of the real spectrum distribution then multispectral imaging is relevant, and you can't say that red is red or green is green because the individual spectral lines could be different. Wnt (talk) 04:42, 13 December 2011 (UTC)

The distinction is driven by human vision. Spectral violet looks similar to purple, but not exactly the same; you can tell the difference visually.--Srleffler (talk) 19:13, 14 December 2011 (UTC)

To me it seems like the clear sky in the eastern U.S. turns particularly beautiful shades of indigo-purple in late August or September, which are not apparent at other times of the year. But a source like [5] seems to be saying that any seasonal variation would be tiny. Is there a recognized difference in shading? Wnt (talk) 19:50, 11 December 2011 (UTC)

EKG question

I recently had an EKG done and it only took a minute or two after I was hooked up. Way in the past I had an EKG and if I remember correctly I had to lay there for quite a while after being hooked up to the machine. Is my memorized experience wrong or is there a possibility that it was done wrong at this recent check?

Thanks in front for any helpful answer.TMCk (talk) 01:52, 11 December 2011 (UTC)

The EKG that took longer (and was done longer ago) may have been done with an older EKG machine which had a single strip as an output, and had 5 leads (one for each arm and leg, and one for the chest.) This would mean that the chest lead (usually a suction cup coated with electrically conductive "goo") would have to be moved to 6 separate positions, turning the EKG machine on and off between each move. So after being hooked up, the operator would have to select and run brief strips for each of the 6 limb lead combinations and then the 6 chest leads, followed by a longer "rhythm strip". In the newer machines, there are 6 chest leads and 4 limb leads, so once positioned, they don't have to be repositioned. They record from all the leads simultaneously rather than one at a time, so the machine doesn't have to have a switch which the operator uses to select which one to record serially. They also store the information in memory so that output is on a normal 8x11" page rather than a 2" wide strip that has to be cut and pasted onto a single EKG page. - Nunh-huh 02:12, 11 December 2011 (UTC)

Thanks so much for your detailed and very helpful response. So my memory didn't trick me :) TMCk (talk) 02:32, 11 December 2011 (UTC)

the mininmal age for gender nonconformity in children?

in the behavioral context.

i know that it's 18 months. but, i have heard that it could appear earlier. is that so?. thanks. — Preceding unsigned comment added by 109.65.19.16 (talk) 09:46, 11 December 2011 (UTC)

FWIW, we do have an article on the topic, Childhood gender nonconformity, but it doesn't answer your question. Red Act (talk) 14:58, 11 December 2011 (UTC)

I'd expect that as soon as gender roles are established, then children could rebel against them. Perhaps the first indication might be them smiling or crying when presented with something that represents a gender role, like when given the classic doll versus fire truck. StuRat (talk) 15:14, 11 December 2011 (UTC)

But that's only possible if the child knows what the gender roles are and that he's not following them. I expect that to take more than 18 months. There's no way that a child who hasn't been exposed to society would care whether he gets a doll or fire truck, since neither existed for nearly the entirely of human evolutionary history. --140.180.15.97 (talk) 19:14, 11 December 2011 (UTC)

I disagree. The maternal instinct doesn't require any exposure to society, and this is what causes kids (mostly girls) to play with baby dolls. Similarly, an instinct to care about devices like fire trucks also exists in some children. If you place those toys in front of children in a population totally isolated from the rest of our society, I'd bet they would play with them (and the adults might, too). I'd also argue that you can reject something without fully understanding it's implications, just as kids often reject foods, having no idea where they come from. StuRat (talk) 21:15, 11 December 2011 (UTC)

I grant that it's possible that infants would react differently to dolls depending on gender, since the dolls look like human beings, and human beings have definitely existed for the entirety of human evolutionary history. However, I highly doubt that the same is true for fire trucks. If a child has no idea what a fire truck is, what it's supposed to do, or which gender is supposed to like it, why would you expect more boys to accept it than girls? Furthermore, the doll & firetruck is just one example of gender roles. The question is about gender nonconformity in general, and many other gender roles are obviously cultural inventions. For example, in many societies it is men who have long hair, not women. In French society, high heels were worn by nobility of both genders. Nowadays pink is associated with girls and blue with boys, but it used to be the other way round (see http://answers.google.com/answers/threadview?id=238733). --140.180.15.97 (talk) 01:20, 12 December 2011 (UTC)

It's a very interesting topic.. I don't have kids of my own yet and of course you can't run the experiment and isolate infants completely from society. I DO believe that there is a "nature" component to it, but no matter how "objective" parents think they are, their beliefs and expectations and influence would have an effect on whether the little girl chooses a doll or a fire truck. I believe that effect is greater then what most people seem to think, that's my impression anyway. Something like Clever Hans effect. Vespine (talk) 00:10, 12 December 2011 (UTC)

In the short-lived Day by Day (TV series), one character remarked that they were teaching stereotypical gender roles to the toddlers in their charge, at which point they made their girl give her baby doll to the boy and the boy gave his fire truck to the girl. The girl then proceeded to feed a bottle to the fire truck as she cradled it in her arms, while the boy pushed the doll around on it's face and made siren sounds. :-) StuRat (talk) 01:16, 13 December 2011 (UTC)

I'm not 100% what you mean by that, but it's precisely the kind of thing I'm talking about. It's a very compelling anecdote, but the children obviously didn't 'know' how to give the bottle or make siren sounds "completely isolated from society". From the earliest moments those "roles" and behaviors would be imprinted onto the children, no matter how objective the parents think they're being, especially these days with exposure to television which is completely saturated with stereotypes. I grew up in Europe and the majority of mine and my brother's toys were soft animals like teddy bears and monkeys and stuff, which was perfectly culturally "normal", we played "zoos" and "families" and all sorts of imaginary games, I never pushed them around making siren sounds. Vespine (talk) 05:09, 13 December 2011 (UTC)

Just one more thought. The strongest evidence I think for a genetic component would be that some kids who have Sex assignment end up rejecting the gender they were raised with. BUT, I wonder what the stats are for that. I don't have time right now, but i'll get back to it later. However, I still think this only points to a genetic component. Vespine (talk) 05:18, 13 December 2011 (UTC)

Layers of North Pole Ice for Google Earth?

Are there any downloadable layers for Google Earth that show the amount of North Pole ice? --CGPGrey (talk) 10:15, 11 December 2011 (UTC)

Yep. See here. (Searched for thickness of arctic sea ice "google earth") SmartSE (talk) 14:00, 11 December 2011 (UTC)

Interesting. This shows that the magnetic North Pole is still over the ice sheet, but the wikipedia article for magnetic North Pole claims otherwise. Which one is correct? --CGPGrey (talk) 17:19, 11 December 2011 (UTC)

Thesepeople rowed there, so the ice must be melting for at least part of the year. They only reached the 1996 North Pole though. The magnetic pole is something like 400 miles away from that point by now, and significantly nearer to the true pole. Dbfirs 21:12, 11 December 2011 (UTC)

In addition to variable ice patterns, the magnetic poles also move around a bit from year to year. StuRat (talk) 21:24, 11 December 2011 (UTC)

Sorry, Stu, I edited the above at the same time as you were making the important point about the pole moving. I estimate that the pole must be about 86 degrees north by now, so is more likely to be back on the ice sheet. Dbfirs 21:28, 11 December 2011 (UTC)

formula unit ions for sodium hydroxide

Are there three ions in the formula unit for sodium hydroxide, or two? 86.7.42.12 (talk) 19:52, 11 December 2011 (UTC)

Sodium hydroxide is NaOH, which is made up of a Na+ (sodium) cation, and a OH- (hydroxide) anion in equal proportion. This makes up the formula unit. Wnt (talk) 20:01, 11 December 2011 (UTC)

Thank you very much. 86.7.42.12 (talk) 20:39, 11 December 2011 (UTC)

hydroxide similarities to fluoride

The fluoride article states, "Structurally, and to some extent chemically, the fluoride ion resembles the hydroxide ion." Why is this? Does it have to do with the position of fluorine next to oxygen in the periodic table? Could this be explained in terms of electrons? 86.7.42.12 (talk) 21:44, 11 December 2011 (UTC)

I would hazard that it's because F- and OH- both contain 9 protons and 10 electrons. 67.185.1.213 (talk) 22:44, 11 December 2011 (UTC)

What this means is that fluoride and hydroxide have the same charge and similar size, and are somewhat comparable in electronegativity. So there are minerals like amblygonite where either F- or OH- can occur at the exact same spot in a regular crystal structure.^[6] Likewise, but more importantly to us, apatite (fluoroapatite), where fluoride can take over the spot held by OH-, namely in tooth enamel. Wnt (talk) 23:19, 11 December 2011 (UTC)

Your ideas are right the O(H) and F are roughly the same size because they are adjacent with similar charge. The shape of the electron shells is the same, perhaps with a slight distortion where the H atom is. The main difference would be due to the proton (H) that can be removed and do things with other molecules near by (hydrogen bond). Graeme Bartlett (talk) 11:47, 12 December 2011 (UTC)

occam's razor

I understand that occam's razor is more of a rule of thumb, not really a law for scientific findings. so can you guys give me example where occams razor failed big time. MahAdik _usap 22:41, 11 December 2011 (UTC)

For thousands of years, people thought the Earth was stationary and the Sun revolved around it. Everyone's experience of movement was that you felt movement (running, falling, riding a horse). It was quite reasonable, given the basic grasp of physics everyone had, to suppose that you could always feel when you were moving, and thus if you couldn't feel movement you must be still. The simplest explanation (to everyone it seemed like an unassailably obvious explanation) to what was moving and what wasn't was that the Earth (alone) was stationary. -- Finlay McWalterჷTalk 22:59, 11 December 2011 (UTC)

Think that was more of a unquestioned subjective viewpoint. The first Earth-centric scientific view required astral phenomena to exist in complex shells to account for their apparent movement in the heavens. Hardly simple. --Aspro (talk) 23:12, 11 December 2011 (UTC)

Although, when they actually tried to explain celestial observations using geocentric models, they ended up having to introduce all sorts of epicycles to get it to work. The heliocentric (ie. sun in the middle) theory is much simpler than a geocentric theory with lots of epicycles. A geocentric theory without epicycles just doesn't explain what we see (retrograde motion of planets has been known since ancient times). --Tango (talk) 23:14, 11 December 2011 (UTC)

The ancient saw that the Moon orbited Earth. By occam's razor, they extrapolated that all other celestial bodies also orbited Earth, and all calculations agreed, except a few wobbles in the orbit of some planets. Since every known celestial body orbited Earth, then Earth was the center of the universe (occam's razor again).

Until someone (Galileo?) noticed that Jupiter had little moons of its own that orbited Jupiter. This meant that not all celestial bodies revolved around Earth, and, by occam's razor, Earth's Moon could be just another moon. This time occam's razor was correct. Then someone (Kepler?) remade the planet calculations, realizing that the wobbles could be accounted for if the planets orbited the Sun instead of Earth. He made calculations that accuratedly predicted all the wobbles viewable from Earth. --Enric Naval (talk) 23:15, 11 December 2011 (UTC)

It was Galileo that discovered the first moons of Jupiter (now known as Galilean moons), but that was after Nicolaus Copernicus came up with the heliocentric model (and it had been proposed before that, but no-one had figured out the details until Copernicus). Galileo's observations just provided additional evidence for an already existing theory. --Tango (talk) 23:26, 11 December 2011 (UTC)

I also don't think that was an example of the failure of Occam's Razor. As already noted, Heliocentrism has existed for quite some time before its acceptance. It's actually a triumph in a way, as one of the reasons why Geocentrism was the accepted theory was the addition of the needless complicating factor of anthropocentric religions requiring Earth to be divinely special (hence it should be the center of the Universe and not anything else). This was also why Galileo's first direct observation of the phenomenon was viewed as blasphemous. Note however that this bias existed long before Christianity in other religions as well.-- Obsidi♠n Soul 00:12, 12 December 2011 (UTC)

Galileo's observations were not denounced as blasphemous. The Church astronomers all agreed with them pretty quickly. They just disagreed with his interpretation of them. --Mr.98 (talk) 01:22, 12 December 2011 (UTC)

What was his supposed 'interpretation' aside from Heliocentrism? Galileo was put to trial for heresy simply because he advocated Heliocentrism contrary to the scripture. He never spoke out against the Church itself and maintained that Christianity can be compatible with Heliocentrism.-- Obsidi♠n Soul 01:34, 12 December 2011 (UTC)

His interpretation included excluding the Tychonic model from his book that was supposed to consider all the evidence, despite it being observationally identical to his proposed model and it actually being the established model that his model was competing against; including the views of the very Pope that had approved his publishing the book, but making them ridiculous (he was, as I say, excluding the actual model of contemporary astronomers in favour of a simplified, outdated model that nobody supported) and putting them in the mouth of a strawman with a name that is a pun on 'stupid'; supporting his view with a bizarre and fairly nonsensical argument about tides, that suggests his motives for arguing this position were not disinterested observation and logic. Given the context of Hermeticism at the time (I do not think evidence exists at the moment to say whether he was a Hermeticist, but he certainly hung out with them, studied with them, and included Hermetic notation and terminology in his work), it's easy to see that this wasn't some purely academic argument with no religious connotation: it all had religious connotations, and he knew it. And this is not to say that he should have been prevented from publishing, but the context is clearly not just about science. If it were, he'd have included the Tychonic model and wouldn't have included the bizarre stuff on tides. 86.164.79.174 (talk) 09:57, 13 December 2011 (UTC)

But doesn't that actually prove the point? The Copernican system was not accepted "pretty quickly", it was the Tychonic system that they accepted. And while almost observationally identical with the Copernican system, it had one thing that failed Occam's razor - it catered to religious interpretation in having to keep the Earth motionless to avoid contradicting scripture despite having to sacrifice reliability in doing so. Galileo's avoidance of the Tychonic system and having to put the prevailing church-approved geocentric arguments in a mock strawman dialogue might even be symptomatic of the fact that scientific works had to pass the Catholic censor and yet he had to include them. Mentioning the actual people involved in those theories would most probably have resulted in far harsher punishments by the Inquisition. -- Obsidi♠n Soul 10:00, 14 December 2011 (UTC)

Occam's razor fails every time evidence is found that rules out what was previously thought to be the simplest explanation. It happens all the time. Dauto (talk) 23:09, 11 December 2011 (UTC)

That's not really a failure of Occam's razor unless there was a competing, more complicated, theory known before those additional observations were made that is verified by those observations. --Tango (talk) 23:14, 11 December 2011 (UTC)

Some people, as Dauto above, misunderstand the rule. It doesn't say accept the simplest explanation, that would hardly be possible. It says accept the simplest viable explanation without resorting to all set of imaginary beings (god, gods, spirits, magic, and such). — Preceding unsigned comment added by 88.9.111.78 (talk) 00:32, 12 December 2011 (UTC)

It doesn't say that at all. Read the page on it if you don't know what it says: Occam's razor. --Mr.98 (talk) 01:23, 12 December 2011 (UTC)

Explicitly not, but it's implied. It's not meant to exclude imaginary beings, but it brings us there. It also excludes awkward, lengthy and unnecessary new concepts. — Preceding unsigned comment added by 88.9.111.78 (talk) 03:19, 12 December 2011 (UTC)

A very interesting question! My first thought is Steady State theory vs Big bang theory. They were competing theories to explain the apparent expansion of the universe shown by red shifted galaxies. Arguably, Steady State theory is the simpler - it just says the universe is as it always has been and always will be, which is pretty simple. Big Bang theory involves a big bang, which is an extra complication. Steady State does require some mechanism for the constant creation of matter, but the big bang requires a one off creation of matter, so that kind of cancels out. It's hard to say which is really the simpler theory, but evidence discovered since (primarily the cosmic background radiation) has shown conclusively that the big bang is the correct theory. --Tango (talk) 23:14, 11 December 2011 (UTC)

I don't see the steady state as being any simpler than the Big Bang. Steady state doesn't have a bang but it stiil has to come up with some ad hoc explanation for the existence of matter which is less intuitive than Big Bang's explanation. Dauto (talk) 23:22, 11 December 2011 (UTC)

In Steady State, matter has always existed, so you don't really need to explain it. All you need to explain is the creation is additional matter to fill in the gaps caused by the expansion. The same kind of explanation is required for a Big Bang, it's just a one off creation rather than a continuous one. I could support a case that Steady State and Big Bang are equally simple, but I can't see how Big Bang is simpler (in which case, Occam's razor was useless, rather than wrong). --Tango (talk) 23:31, 11 December 2011 (UTC)

As a side note, scientists hardly ever invoke Occam's razor any ways. The somewhat similar but much more elaborate concept of Bayesian statistics on the other hand is often used. Dauto (talk) 23:22, 11 December 2011 (UTC)

Bayesian statistics requires a prior distribution. It's hard to come up with a good one when you are comparing two completely different theories (qualitatively, that's what Occam's razor tries to do, but it can't put any numbers on it). Bayesian statistics is normally used to determine the parameters of a theory, rather than determine if a theory is right at all. --Tango (talk) 23:29, 11 December 2011 (UTC)

I would just note, as is evident above, questions about what's "simpler" are largely in the eye of the beholder. For Einstein the luminiferous ether was a stupid and unnecessary addition to the universe. For most of his contemporaries, it was an elegant solution to the bridging of the electromagnetic and material worlds. We live in a thoroughly Einsteinian world now, so it's hard to see the older view as anything other than inadequate, but from a classical point of view, the ether is tremendously elegant, tremendously fruitful, and, in a sense, terribly obvious. From an Einsteinian view, the classical world has all sorts of unnecessary entities in it.

Similarly with the geocentric and heliocentric views. From a classical philosophy standpoint, the geocentric universe made the most sense. It was undeniably elegant. The epicycles and other cruft that grew onto it were seen as a little unfortunate, but the original heliocentric models had all of that cruft as well, but lacked the obvious philosophical benefits of the Earth being the center. Today we see that philosophical benefit (humanity at the center) as just being medieval pap, but that's in part because we've been living in a heliocentric world for a very long time, and we tend to see it as obvious, natural, elegant, etc. --Mr.98 (talk) 01:22, 12 December 2011 (UTC)

Phlogiston theory? --ColinFine (talk) 21:43, 12 December 2011 (UTC)

Occam's razor never fails, but people fail to apply it properly. Occam's razor is really very specific: if there are two explanations which explain all your observations, and one of them is simpler in that it has fewer factors, then choose the simpler one. But Occam's razor can be abused when a more complex theory has greater explanatory value, but the Razor is invoked to try and avoid acceptance. Occam's razor only applies where the different theories explain everything equally. The Razor doesn't speak to whether one theory is more likely to be true than another: plenty of times, a more complex explanation has turned out to be true. Example: they used to think that sickness came from various humours in the body being out of balance (if I remember right). But as it turns out, the sickness was really caused a few among millions of different kinds of microscopic life forms interacting with DNA relative to the immune system in a Darwinistic fight for survival, but also different chemical reactions influenced by food choice... etc. If a more complex theory explains more, then it's inappropriate to talk about Occam's razor. Historically, we were shown over and over again that phenomena were more complex than we though, and required more complex explanations. B^e——C_ritical 01:54, 14 December 2011 (UTC)

Radiation guns

How practical (in terms of design, manufacturing, and usage as a weapon) would "radiation guns" (portable devices that give off directed blasts of ionizing radiation) be? Since they're not in everyday use like firearms are, I assume there are limitations making them less than practical; can someone elaborate? —SeekingAnswers (reply) 23:07, 11 December 2011 (UTC)

A soldier could, right now, carry a dental-sized X-ray generator, with a backpack full of car batteries to run it. Enemies shot with this radiation gun (over a range of say 100m) would develop a slightly increased probability of developing cancer over the following few decades. Increasing the "kill power" from "health and safety violation" to "instant death" is going to require orders of magnitude more energy, and so lots more car batteries. -- Finlay McWalterჷTalk 23:16, 11 December 2011 (UTC)

Radiation sources give off radiation in all directions. You can't really reflect radiation, so you would need to absorb the radiation that's going in directions you don't want it to (such as, towards the person carrying the weapon). If the source is radioactive enough to do damage at a distance, then whatever shielding you use to absorb the rest of the radiation is going to get extremely hot. You would need some very complex cooling system to keep the gun from melting, which seems impractical to me. The easiest way to use radiation as a weapon is a dirty bomb. --Tango (talk) 23:19, 11 December 2011 (UTC)

The best radiation "gun" the military has is mobile radars. They shoot a small "beam" of radiation compared to fixed radars. While the word "beam" is used in the field, it isn't a narrow fixed width beam as those outside the field would expect. It is more like a cone that expands quickly as it leaves the radar. It is possible to use this as a weapon of sorts. The following are things that I've seen radars do, and how that could be a weapon:

• Fluorescent lights glow when in the beam from the radar. So, if you hit a building with fluorescent lights, you can make them light up all night long. That would annoy the enemy.
• Metal gets hot very quickly when hit by the beam from the radar. I was hit once and noticed it because it felt like I was stung by a wasp on my chest. It was my dog tags heating up. Hitting troops with a beam will make all their metal heat up. That would be annoying and, possibly, cause the enemy to stop functioning until the problem is resolved.
• A standard spark plug will fire when hit by the beam from the radar. If you shoot cars with a radar, all the spark plugs fire at once and the engine dies. That would stop an enemy car, but it could be restarted. So, you have to keep shooting it over and over to keep it stopped.

The fact that this isn't used means that it is too expensive and/or illegal. I suppose it is a bit of both. -- kainaw™ 23:42, 11 December 2011 (UTC)

How close do you need to be to get those effects? I would imagine you would need a very large and heavy energy source to get those effects at ranges useful as a weapon, which means you would need static radars, not mobile ones. --Tango (talk) 23:52, 11 December 2011 (UTC)

I was never more than 100 feet from one of the radars. So, you have to be very close. But, that doesn't mean that it couldn't be used. For example, a roadside box could be used to disable a vehicle (as opposed to the roadside explosives now being used). I don't think it would be very useful since the vehicle could be restarted and moving the power supply and radar box would be necessary each time to keep the enemy from taking note of where it is located. -- kainaw™ 00:00, 12 December 2011 (UTC)

It may also be important to note that the radars I worked with were made in the 1960s. I'm positive that the newer ones are smaller and more powerful. Still, I don't think a weaponized radar gun would be very useful. -- kainaw™ 00:01, 12 December 2011 (UTC)

one spark will not stop the car as the engine inertia will keep it turning and subsequent sparks will fire the cylinders at the right point, it would be like pinging. However such a powerful pulse could wreck the other car computers and electronics. To kill with radiation it would be much easier to inject a tiny radioactive pellet of polonium or radium. (as has happened before) Graeme Bartlett (talk) 11:40, 12 December 2011 (UTC)

See: laser#As weapons and Directed-energy weapon, and in fiction: raygun. I imagine a sufficiently powerful X-ray laser (or xaser) would be pretty deadly. Or maybe something like that being researched for inertial confinement fusion would do. The obvious problem in all these cases is making enough power available in a portable device. Astronaut (talk) 16:27, 14 December 2011 (UTC)