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All I do is drink and wee, I'm gonna live forever!

18 April 2012 — dan

A reader writes:

Seeing lrwiman's comment on your post about how you can't lose weight by eating ice reminded me: Do you really need to drink eight glasses of water a day?

I guess it actually depends on who "you" are, how big or small, and how much you sweat and so on. Is eight 8-oz glasses just a one-size-fits-most amount for everyday urban humans?

Lana

There is no scientific basis for the "eight glasses a day" idea.

Eight eight-fluid-ounce glasses add up to, of course, 64 fluid ounces, or about 1.9 litres. That is rather a lot. If you're an office worker, you are very unlikely to need that much water (or equivalent other liquids, though the people who support the eight-glasses thing often say that no beverage other than water counts at all) to be perfectly hydrated. If you're a labourer in a hot climate, though, you're going to need a lot more than eight glasses.

(See also, people hiking in the desert who don't realise that you need to drink a lot more water, and keep your electrolytes up, when you're exercising in high temperatures and low humidity.)

Unless you drink a really amazingly large amount, it won't do you any harm to drink more water than you need, if you're not concerned about the amount of time you spend in the bathroom. 1.9 litres over several hours is well below the level needed to cause water intoxication in an adult, unless your kidneys are in bad shape.

Note that your total water intake can very easily be three or four litres a day, because other beverages, and water contained in food, count towards it as well. The eight-glasses people usually warn against consuming water when it's mixed with other substances that reduce its net hydrating effect, like caffeine or alcohol, which are both diuretics.

As usual, though, the dose makes the poison, or in this case the diuretic. A doppio ristretto or shot of Polish Pure Spirit is, like drinking seawater, going to have a net negative effect on your hydration. But if ordinary black tea didn't hydrate you, the entire British Empire would have died of thirst in about 1750. You can also remain well hydrated if all you drink is beer or weak wine; beer and diluted wine used to be staple beverages for whole cultures before the invention of sewer systems, when the available water was commonly contaminated with organisms that couldn't survive a few per cent of ethanol.

Drinking lots of water, often but not always this particular figure of eight glasses a day, pops up quite often as part of odd diet regimes.

The "Stillman diet", for instance, was an early low-carbohydrate diet which prescribed eight glasses of water a day in addition to any other fluid intake. And it sure did seem to pare away the pounds; it made a significant contribution to Karen Carpenter's downward trajectory of both weight and health.

Lorraine Day includes a lot of water-drinking in her list of things you can do to, immensely plausibly, cure yourself of cancer (unless of course you are Jewish, in which case she'd probably prefer that you die).

Back here on planet Earth, drinking water when you feel peckish can be a good dieting trick. Go ahead and throw in some ice cubes too, if you want something to (carefully...) chew on.

But apart from this, and from a few diseases for which drinking a lot of water is a treatment, there's no reason to drink water when you're not thirsty.

Psycho Science is a regular feature here. Ask me your science questions, and I'll answer them. Probably.

And then commenters will, I hope, correct at least the most obvious flaws in my answer.

Posted in Psycho Science, Science. 9 Comments »

Save on cigarettes: Let someone do the smoking for you!

16 April 2012 — dan

A reader writes:

How dangerous is second-hand smoke, really?

The bans on indoor smoking that've taken over the Western world suggest that it's REALLY dangerous. Here in Australia you can no longer smoke even in a pub, so apparently second-hand smoke is worse for you than alcohol.

But it stands to reason that second-hand smoke is much more dilute than the smoke sucked out of the actual cigarette. I can believe it'd be a big health hazard if you were in some 1925 basement speakeasy jazz club with no ventilation and everyone smoking like crazy until you could barely see your hand in front of your face, but the thickness of smoke in a pub before the ban wasn't anything like that. It still made your clothes and hair smell like an ashtray, but that's just disgusting, not dangerous. Was it really that bad?

Richelle

Nobody knows exactly how dangerous second-hand smoke, or "passive smoking", is.

This is partly because of the, well, smoke screens, produced by astroturf organisations with the usual hilarious Decent People Opposed to the Decapitation of Adorable Ducklings names and the similarly usual giant piles of funding from the tobacco companies.

But it's also partly because there is, as you say, such a wide range of possible exposure levels.

And, I think, it's mainly because this is principally an epidemiological question, and epidemiology is a slippery area of study.

Given all these caveats, though, it's still clear, from numerous studies, that chronic exposure to second-hand smoke, even at relatively low levels, does significantly increase the chance of a non-smoker getting lung cancer and/or heart disease, plus a laundry list of other ailments that result from the inhalation of bad stuff.

If you're just waiting for a bus next to someone smoking and you get the occasional whiff of their Marlboro, nothing quantifiable will result. But being a child in a house with indoor-smoking parents, or regularly visiting a smoky pub as an adult, raises your lung cancer risk. Working in a smoky pub raises it more.

The important detail to remember here, though, is that the incidence of lung cancer in non-smokers is low. Only about 15% of all lung cancers are found in non-smokers, and most of those seem, once again within the statistical limits of what epidemiology can tell us, to have been caused by something other than second-hand smoke.

Chronic exposure to highly polluted air, for instance, will do it. A traffic policeman in Beijing, Mexico City or Ahwaz, Iran really ought to wear a gas mask, or possibly SCUBA gear, to work.

Numerous other kinds of smoke are also carcinogenic. If you work in a commercial kitchen with woks full of smoking overheated oil all over the place, that's bad. So is wood smoke; it may smell nice, but it's definitely carcinogenic. Incense is bad for you, too.

And then there's radon, a well-known danger in the USA, but almost completely unknown here in Australia, where very few houses have basements. You'll probably only have much exposure to radon if you're a miner, of if you spend a lot of time in a basement or other poorly-ventilated underground room dug into high-radon ground.

Sundry inhaled particulate matter is also bad news. This is another problem for miners, and various other industrial workers.

And there are lung-cancer-causing viruses, too.

And then there's asbestos inhalation, of course. But that's much more likely to cause the horrible-but-not-cancerous disease asbestosis than it is to cause mesothelioma.

Or you could just be fortunate enough to be genetically predisposed to develop lung cancer.

If you're a non-smoker and you can avoid all of these risk factors, then the chance that you'll get lung cancer - or, at least, that you'll get it a long enough before some other disease kills you of "old age" for the lung cancer to become an actual problem - is very small. Second-hand smoke exposure that doubles your risk of cancer sounds scary, but if there's only a one in ten thousand chance that you'll get it in the first place, then the doubling only raises it to a chance of one in five thousand, which probably won't keep you awake at night.

And the risk from different causes isn't necessarily cumulative, either. If you're a non-smoker who works without breathing protection in the Acme Smoke, Flame and Asbestos Dust Factory in the Land Occupational Health and Safety Forgot, and as a result have a 50% chance of getting lung cancer in the next ten years, then heavy exposure to second-hand smoke while you drink your way to amnesia on the weekends may only raise your cancer probability to 51 per cent.

Or it may do more. Again, epidemiology. Pick a hundred coloured marbles from the barrel of a million, try to figure out what colour the rest of them are.

Some scientists have argued that there's a somewhat unexpected public-health benefit from indoor smoking bans. Not only do they keep second-hand smoke out of the lungs of non-smokers, but the nuisance of having to go and stand outside with the rest of the Tobacco Lepers causes smokers to smoke less, and become healthier. The evidence presented for this is generally a reduction of hospital visits for smoking-related heart and pulmonary disorders after indoor-smoking bans go into effect, but this is yet more epidemiology, so it's eminently possible that the effect is from an entirely different cause, or smaller than it seems, or even nonexistent.

(Workers who hate having to go out into miserable weather to get their fix could easily, for instance, use their ten-minute break to suck down as much smoke as they possibly can in that time, to "stock up" and make sure that they can make it to the end of the day without cravings. They could, thereby, get a lot more crap in their lungs than if they were still allowed to have a leisurely cigarette or two at their desk.)

Psycho Science is a regular feature here. Ask me your science questions, and I'll answer them. Probably.

And then commenters will, I hope, correct at least the most obvious flaws in my answer.

Posted in Psycho Science, Science. 6 Comments »

Very very shiny rocks

12 April 2012 — dan

I couldn't really tell you which is my favourite item in my little element collection, but these recent additions certainly catch the eye.

(They're not actually all that recent, but I forgot to write about them until now.)

These are lumps of chromium. Solid chromium.

UPDATE: As requested in the comments below, here are a couple of little (silent) video clips of the chromium lumps in the sun, plus a chunk of crystalline silicon carbide and a couple of enormous cubic zirconias:

As undisputed king of the element-collecting hobby Theo Gray points out, chromium is commonplace in the modern world, but only in ultra-thin electroplated layers on other substances. There's no need to use more than a super-thin layer of chrome to make some car-part shiny, because chromium in air protects itself from corrosion with a hyper-thin oxide layer, sort of like aluminium, but more so. The chrome oxide layer, unlike the aluminium layer, is so thin that you can't even see it, so chrome looks freshly-polished all the time.

This stuff is actually so shiny that it looks fake, like rocks spray-painted silver and given an outlandish name in an episode of Star Trek. It feels more real when you pick it up, though, because chromium is only a little less dense than iron. It's also nonmagnetic, and non-toxic.

Various chromium salts are bad news and can be made accidentally in the home, by for instance using a stainless-steel object as the sacrificial anode for electrolytic de-rusting. But the metal itself is benign.

This is more than can be said for what's next to the chrome on my display shelf, the block of Wood's metal I cast in a Lego mould. Wood's metal has both lead and the more dangerous cadmium in it.

(See also, mercury. Metallic mercury is not good for you, but there's no reason to call out the men in moon suits just because you broke a fluorescent light. Organic mercury compounds, however, are very dangerous. Methylmercury, which can get into your body via contaminated fish, is rather nasty, and dimethylmercury is absolutely pure unadulterated gold-medal-winning death on a stick.)

I got my chromium, and a few other trinkets over the years, from eBay seller "The Mists of Avalon" (on eBay Australia, on eBay UK). From their name, you'd expect them sell a lot of metaphysical wank - and yes, they do! But right next to their "Wiccan/new age/spiritual/pagan" and "Healing/metaphysical crystals" categories, though, they've got umpteen science collectibles, and the listings for those items don't even contain the traditional fanciful explanations of the supposed effects of the periodic-table sample you're considering buying on chakras and meridians.

At the moment, Mists of Avalon seem to be the only eBay dealer selling these nice rock-shaped chromium lumps. They've got one listing for chunks not unlike mine, and another listing for "more than 10" bags of smaller lumps. (They've also got a listing for some chromium powder, but you probably don't care about that.)

There are a few other eBay dealers selling chromium, and other element, samples of one kind or another (on eBay Australia, on eBay UK). There's SoCal Nevada, for instance; I've bought a few sciency knick-knacks from them, too. They currently have one tiny crystal of chromium, and a couple of big machined disks of the stuff.

Theo Gray's pals RGB Research will be pleased to sell you a hefty cylinder of high-purity chromium, of the same standardised 35 by 55mm size as the tungsten and magnesium ones I've got (they don't have any of the big tungsten cylinders for sale at the moment, though) for the trifling sum of $US325 plus delivery.

EBay seller iannhart (on eBay Australia, on eBay UK) has a selection of 35-by-55mm cylinders too (including some tungsten ones!), as well as other shapes and sizes of chromium.

I'd hold out for the rock-shaped lumps, though; they really show off the bizarre nature of this substance. Tungsten doesn't look like much; its special characteristic is its extraordinary density, making it a plausible stand-in for plutonium.

Chromium is more like frozen latinum.

Posted in Nerdery, Science, Toys. 6 Comments »

Point-and-shoot infrared random number generator

11 April 2012 — dan

A reader writes:

The last time I used an infrared thermometer it was in a lab at university, and the thing was the size of a shoebox and cost thousands of dollars. I don't know why it took me so long to discover that now they cost fifty dollars, but I did, so obviously I bought one because at that price why not.

I've been having a lot of fun seeing what temperature my walls and ceilings and floors and computers and pets are at, but some things confuse me. The sky, for instance, reads around 5°C when it's overcast (ambient ground-level temp about 15°C), but when it's clear the sky reads about -50°C, day or night. Thanks to the University of Wikipedia I know that the thermosphere is very sparse but can be very hot, and the mesosphere below it is around -90°C; is the minus 50 just averaging those out?

Also, when I shoot the side of a saucepan with boiling water in it, I get a reading of only maybe 50 or 60°C, even if I'm shooting a part that's above the water line and clearly above 100°C because if I slosh the water around it hisses when it touches the inside of that part. What's up with that?

Pablo

The non-contact infrared thermometer is, indeed, a fantastic tool, and toy. Cheap ones usually aren't pinpoint accurate and may be quite severely inaccurate outside their specified temperature range; a -35-to-230°C cheapie, for instance, may still give numbers well outside that range, but shouldn't be trusted.

But as you say, point-and-shoot temperature measurement for under $100 is pretty darn fantastic, even with caveats.

Actually, the absolute lowball price for IR thermometers on eBay these days is less than ten US dollars, including delivery. (The same search on eBay Australia, for any Aussies for whom the "geotargeting" for the other search doesn't work.) You've got to wonder how accurate a $7.50 thermometer can possibly be, and the cheapest ones also run from little button batteries that may not last very long, but I still think a sub-$10 IR thermometer you can put on your keyring qualifies as Living In The Future.

(Most non-contact thermometers have a laser sight, too, allowing you to entertain your cat while you measure its temperature.)

What these thermometers actually measure is lower-frequency thermal radiation. Thermal radiation is light, and can be of high enough frequency to be visible to the human eye - red-hot metal, tungsten light-bulb filaments, et cetera. What people usually mean when they refer to thermal radiation, though, is invisible long-wavelength infrared light. Cheap non-contact thermometers all measure medium-to-long-wave IR, with wavelengths in the neighbourhood of ten micrometers (µm, often written as "um" to avoid the hard-to-type Greek letter Mu).

I think the most common wavelength specification is "8-14um", which includes, according to a common definition, the very bottom of the mid-wavelength band and almost all of the long-wavelength band.

(Medium-infrared is a few octaves below the 700-to-800-nanometre near-infrared that human eyes can actually detect, if it's bright enough. I've made both versions of those IR goggles, by the way; they work great!)

There are three factors that can throw off this sort of temperature reading.

The first is the emissivity of whatever you're pointing the thermometer at. There's no such thing as a pure black-body radiator outside Physics Experiment Land; for this reason, no real substance emits as much IR at a given temperature as it should, though many substances are pretty close. Consumer IR thermometers just make a guess about emissivity; I think most of them are calibrated for an emissivity of 0.95.

Fancier IR thermometers, like this $AU189 one for instance, not only have a wider temperature range and higher accuracy, but also let you correct for emissivity and even the distance to the target, which is the second factor that's affecting your temperature readings. The distance-to-target matters because air emits IR like everything else does; it doesn't emit much of it, because of its low density, but the more air there is between your thermometer and its target, the more the temperature of that air will skew the reading.

(The cheapest eBay thermometer I've found that claims to offer emissivity adjustment is the one found by this search, for £29.99 delivered, which is about $US48 or $AU46, as I write this.)

Emissivity is a much bigger factor than distance to target for most readings, though. Look, for instance, at the emissivity list here, or the bigger one in this PDF. Some things - unfinished wood, clay, human skin - have emissivity well above 0.9. Other things - polished metals, in particular - have extremely low emissivity, of 0.1 or less. Even rough-finished and/or oxidised metal commonly has an emissivity of less than 0.7.

What this means is that it's very difficult to get an accurate reading if you point an IR thermometer at metal cookware. Even if it's black cast iron you'll get too-low readings from a cheap IR thermometer that assumes an emissivity of 0.95, and if your cookware is shiny stainless steel, you'll have no chance.

The third confounding factor is that when you're not reading the temperature of the actual object - and if you're pointing your thermometer at a shiny stainless saucepan with an emissivity of 0.1, you're pretty close to not measuring the saucepan's temperature at all - you can easily be mainly reading the temperature of something else whose mid-IR emissions are reflecting off the actual object. Essentially, you have to treat all metal objects, in particular, as if they're plated with mirror-polished chrome, and think of what you'd see reflected in them if that were the case.

You can minimise this problem by always keeping the thermometer's line of sight as close as possible to perpendicular to the surface of any low-emissivity objects, but even this won't help much if the object is curved, like the side of a saucepan. For reflective low-emissivity targets, a perpendicular shot will mainly tell you the temperature of the thermometer itself.

(If you want to use your IR thermometer to find hot spots around your car engine, or help you tune a tiny model engine with better thermal resolution than you can get from the spit test, you're not going to get good numbers by shooting the bare metal. A spot of matte-black paint or chalk on the head ought to give you decent results; high-temperature tape made from Kapton or Mylar won't curl up or melt at model-engine temperatures, but it has very low emissivity with most backing materials. Fibreglass tape might perhaps work, since glass generally has quite high emissivity.)

Water and ice have an emissivity above 0.9 and are opaque to medium- and longer-wave IR, so you'll get accurate temperature numbers if you point your thermometer into a pan of water, even if you can clearly see the bottom of the shiny pan in the visible spectrum. This goes for the water in clouds, too; there's a lot of air with invisible but high-IR-emissivity water vapour in it between you and the cloud, but if you point your thermometer at a cloud and get a reading of 5°C, that's probably pretty accurate.

(Clouds themselves can be seen because they're made of tiny liquid water droplets, not water vapour.)

When you shoot your thermometer at the empty sky, especially at night, you'll probably get the lowest reading that your thermometer can manage - commonly -50 or -60°C (-58 or -76°F). As I've mentioned before, all that's between you and the near-absolute-zero temperature of deep space, when the sky is clear, is air, and whatever dust and water vapour it happens to be carrying. The result is very little mid-IR light, and very low IR-thermometer readings. Even with the whole thickness of the atmosphere between you and space - or, if you're not shooting straight up, considerably more than the vertical thickness of the atmosphere - you'll still probably get as low a reading as your thermometer can deliver.

Digital cameras, by the way, can see near-infrared very well; their sensors are actually more sensitive to it than they are to visible light. (Film cameras are different; film tends to be more sensitive to ultraviolet than visible light.)

For this reason, all normal digicams have an IR-blocking filter in front of the sensor, to stop infrared, generally detected in counterintuitive ways by the differently-filtered photosites on the sensor, from giving all of your pictures weird colour casts.

Psycho Science is a regular feature here. Ask me your science questions, and I'll answer them. Probably.

And then commenters will, I hope, correct at least the most obvious flaws in my answer.

Posted in Psycho Science, Science, Toys. 1 Comment »

Horniness

13 March 2012 — dan

A reader writes:

Why do horns make things louder?

I mean, I accept that they do, on gramophones and megaphones and PA speakers at the train station and brass instruments and so on, but what's actually going on there? Why does the sound of your voice get louder just because you're holding a conical thing in front of your mouth? Is it just making it more... directional?

Dennis

The great problem of audio production, and audio reproduction too, is coupling the sound-producing thing to the sound-transmitting medium, which is usually air.

Air is very light. Most things that make sound are, in comparison, very heavy. The moving parts of loudspeaker drivers, the strings of a violin or piano, the lips of a trumpet-player who's blowing a sort of highly controlled raspberry into the mouthpiece of the instrument; all very very heavy, compared with air. All not good at moving lots of air, which is what you want your sound-making thing to do. Wave a brick around in the air and you'll invest a lot more energy in accelerating and decelerating the brick than you manage to impart to the air.

One way of solving this problem is to make your speaker driver very light too. Electrostatic speakers use a big flat sheet of super-thin plastic as a driver; the sound-producing element in a plasma speaker is made out of ionised air (or other gases, if you're a big wuss who doesn't want ozone poisoning).

Horns are a simpler way of solving, or at least reducing, the coupling problem. When you put a heavy-compared-with-air vibrating object at the small end of a horn, the only air it can move is the air right in front of it at the small end. Moving this air is still pretty easy, but the restricted air's mechanical "impedance" is nonetheless quite a bit higher than it'd be if it were unconfined.

As sound pressure waves move down the horn, the gradually widening shape of the horn (for loudest results, an exponential curve) allows the small amount of higher-pressure air next to the driver to transfer its energy to a large amount of lower-pressure air. The end result is that more of the energy of the driver ends up as sound waves.

A sealed-box loudspeaker has an acoustic efficiency - the amount of the input electrical energy that comes out as sound energy - of about one per cent, at best. Horn speakers can manage thirty per cent without much trouble, and quite a bit more if you design them for loudness rather than fidelity. Take the horn off a phonograph and you'll have to put your ear right next to the diaphragm to hear much of anything, but with a big horn on it, a wind-up phonograph making sound by scraping a needle over a disc of shellac can legitimately be described as quite loud.

(Some phonographs let you remove the horn, or never had a horn in the first place, and allowed you to listen through one or more rubber tubes that went to a headset of some sort - essentially, primordial headphones. This allowed you to listen to your records in privacy, albeit with weird stethoscope-y sound colouration on top of the lousy fidelity of the phonograph system in the first place.)

Outside of Physics Experiment Land, acoustic horn design and implementation has many engineering tricks. For instance, modern horn loudspeakers usually have a horn throat that starts out much smaller than the diaphragm of the actual driver, which may be in its own actual rectangular speaker box stuck on the small end of the horn. There are also horn loudspeakers, like the legendary Klipschorn, that use various workarounds to fold something that acts somewhat like a horn into a speaker that can be mainly built out of flat wooden panels.

Also, the lowest bass frequency a horn can reproduce is determined by the size of the mouth of the horn; that's why public-address and hand-held megaphone speakers always sound tinny. Speakers like the Klipschorn have their horn mouth on the back of the enclosure, and are meant to be shoved into the corner of a room, so the walls behind them can provide a bit more effective horn size. Horn loudspeakers are also deliberately designed to be further away from an ideal horn shape than is strictly necessary, to balance the efficiency of the horn with the hard bass cut-off that a "pure" horn, with a mouth small enough to fit in a room, has at low frequencies.

The old phonograph horns have been reborn, too, as "amplifiers" for MP3 players and cellphones. The phone, MP3 player or ear-bud headphones plug into the small end of a horn, and suddenly the tsss-tsss-tsss of someone else listening to their iPod on the bus turns into actual music.

Some of these devices are very fancy and very expensive, but if you search eBay for "amplifiers" for MP3 players you'll find lots of cheerful-coloured horn doodads among the actual electrical amplifiers. The going rate for a combination iPhone stand and horn "amplifier" now seems to be about two bucks delivered.

Psycho Science is a regular feature here. Ask me your science questions, and I'll answer them. Probably.

And then commenters will, I hope, correct at least the most obvious flaws in my answer.

Posted in Music, Psycho Science, Science. 1 Comment »

"Sucrosa. It's a pill."

4 March 2012 — dan

A reader writes:

One of your recent posts got me thinking.

Everyone (or anyone who's ever had occasion to read any sort of scientific study), knows about the placebo effect. I'm curious as to whether the magnitude of said effect has ever been studied, in order to determine the extent to which placebo effect is an actual effect, or just the natural history of a disease (or whatever).

I'm thinking that a randomised, NON BLINDED study might be necessary.

Take a bunch of people with the same usually-harmless disease, say a simple cold, or something like Bell's palsy. Tell them that there's a trial of a new wonder drug to treat their condition, and would they enrol in said study. Tell some people that they are getting the 'drug', and tell the others they are getting placebo. Give everybody placebo.

If there's a significant difference between the two groups, then that would be an actual placebo effect (ie thinking you're going to get makes you get better), as opposed to things just getting better on their own.

Has something like this been done? Would there be any problem with it, other than the ethics of telling people they're in one study but actually studying something entirely different?

Ben

Yes, there have been some studies of this sort. Placebo hasn't achieved much.

It's popularly imagined that placebos can do all sorts of amazing things, just as adrenaline makes a tiny woman able to lift a crashed car off her baby, and acupuncture can be used for surgical anaesthesia.

None of these things are actually true.

The reason why the placebo-controlled trial is such a central tool of medical research is that placebos don't do much of anything. If placebo treatment really was effective for all sorts of things, then, one, doctors could save a lot of time and money by just giving patients placebos all the time, and, two, placebo response could be a confounding factor on the non-placebo side of placebo-controlled trials. There's nothing stopping someone from having a placebo response to a real treatment, on top of whatever the treatment itself does.

The reason why trials are placebo-controlled, rather, is so that they can be blinded properly - preventing at least the patients and preferably also the doctors from being able to tell whether they're administering the medicine or the placebo. Unblinded tests are terribly susceptible to all sorts of biases, and a number of practical problems as well, like for instance all of the subjects who discover they're not getting any medicine not bothering to turn up next week.

The placebo effect, insofar as actual empirical science has been able to quantify it, is a delusion. That's "delusion" in the technical psychological sense - a counterfactual belief. But if you're given a placebo as a treatment for pain, or anxiety, or depression, and it works, then you have a delusion that your illness is not as severe. Which, for all practical purposes, is the same as "real" medicine for conditions like this that're all about what you perceive and how you think, rather than empirically measurable phenomena.

This is not the case for most illnesses, though. If you're given a placebo treatment for diabetes, or cancer, or yellow fever, you may if you're particularly amenable to positive delusions sincerely and unshakably believe you're getting better. But you won't be. Just as some dangerously thin anorexic people can literally see a fat person when they look in the mirror, some people undergoing worthless treatment for, say, cancer, can literally feel the lump getting smaller. Until they die.

(The flip-side of this is the not-terribly-well-documented situation in which someone is given a "nocebo", something inert which they believe to be poison or black magic or what-have-you, and then develop real symptoms or even die. There's no very persuasive evidence that people who believe themselves poisoned or cursed in one way or another actually can "worry themselves to death", but it's uncontroversial that someone who sincerely believes themselves to be in a nonexistent deadly situation can worry themselves into a state requiring serious real medical treatment. Note that it doesn't count if the patient just has a fatal car accident while driving frantically to the hospital after, say, being bitten by a non-poisonous spider.)

To really tell how effective placebos are, you need to do a three-pronged study, with one group getting a treatment, one group getting a placebo, and a third group getting nothing at all, if you can persuade that last group to stick around. (Or you can do a two-pronged study with placebo and no-treatment, if you can get such a thing past your Ethics Committee.)

When people do this, testing placebo against nothing at all, there tends to be little difference, and no objectively measurable difference at all.

There are lots and lots of real individual clinical observations (as opposed to friend-of-a-friend stories) of placebos creating real physical changes in real diseases like irritable bowel syndrome, asthma, ulcers and quite a lot of other conditions. These changes are hard to pin down, though; they exhibit the same deadly weakness seen in claims of paranormal powers, in which the harder you look to see if the effect is real, the smaller it becomes.

Useful placebo effects are, at best, highly variable between patients. And, again, you can't really tell what's going on without running a pretty big study of one kind or another, testing placebo versus no treatment at all. This is ethically difficult, and probably not a great use of researchers' time, compared with trying to develop non-placebo treatments that work whether the patient believes in them or not.

I could continue to ramble on here, but I've really got nothing much more to say about placeboes than actual-medical-doctor Harriet Hall says in this excellent article.

(The title of this post is from this Onion article.)

Psycho Science is a regular feature here. Ask me your science questions, and I'll answer them. Probably.

And then commenters will, I hope, correct at least the most obvious flaws in my answer.

Posted in Psycho Science, Science. 3 Comments »

Sproing

2 March 2012 — dan

A reader writes:

If you take a spring - a metal one I suppose (I know nothing about springs other than they're fun to play with) - and hang it by one end, with no weights or anything attached to the other end, and just leave it hanging there, will it eventually (like really eventually) become completely straight? Or what will happen? Does it matter what kind of spring it is? Will it's own weight straighten it out, or is there something about its structure that would prevent that from happening? And the follow-up, if the answer is yes, is, let's say it's a Slinky; about how long would it take?

I wish I could say I had a beer riding on this, but the truth is I'm just geeky and thought you might know.

Michael

No, a hanging spiral spring won't straighten.

The key concepts here are elasticity and plasticity. The whole idea of a spring is that it's elastic - you can stretch and/or compress it, and when you let go, it returns to its original shape. If the force applied to an elastic object exceeds the limits of its elasticity then the object will be permanently deformed (or just break), but you'd need a pretty darn long, but skinny, spring for that to happen just from the spring's own weight.

Slinkies are an extreme case, here, because they're a quite unusual kind of spring, with peculiar dimensions compared with most spiral springs. Dangling a brand new Slinky may actually give it a slight permanent stretch, but it clearly doesn't stretch it very much, and you can leave it hanging as long as you like without getting any more stretch than happens in the first few minutes.

It's actually normal for a new spring to distort somewhat when put to use. This is called "taking a set", and has to be accounted for in the design of devices that use springs, from the huge ones in heavy vehicle suspensions to the incredibly delicate ones in mechanical wristwatches. It's unusual for a spring to take a set just from its own weight, though.

If you made a spring out of, say, tin/lead electronics solder, then it wouldn't need to be very long in order to straighten out under its own weight. It'd probably continue to straighten for some time, too - meaning hours, though, not years. Tin/lead alloy is of course a terrible material for springs, since it's highly plastic and hardly elastic at all.

Apropos of this, there's a really neat guide to making your own springs here. Home handypersons usually regard spring-making as a black art and just end up with a parts box full of springs cannibalised from other items, but you really can make them yourself without being a master metalworker.

(Oh, and I know I sound like a broken record, but J.E. Gordon's "The New Science of Strong Materials, or Why You Don't Fall through the Floor" and "Structures, Or Why Things Don't Fall Down" both have a lot to say about the springiness of actual springs and of many other objects, and about the foundational concepts of stress and strain.)

Psycho Science is a regular feature here. Ask me your science questions, and I'll answer them. Probably.

And then commenters will, I hope, correct at least the most obvious flaws in my answer.

Posted in Psycho Science, Science. 3 Comments »

Pretty, but smelly

24 February 2012 — dan

A reader writes:

Why is "cloudy ammonia" cloudy?

I've used household ammonia for decades now, for cleaning windows and floors and so on, and never really questioned why it has that swirling cloudy look. But the other day I realised that this stuff is just a solution of ammonia (NH3) in water, and I don't think there's any reason why that shouldn't be clear, like a solution of many other simple chemicals in water.

Where do the clouds come from?

Jennifer

Some readers may be confused at this point, because different parts of the world have different kinds of supermarket ammonia-water. I think cloudy ammonia is the standard kind in the Commonwealth, with the non-cloudy version being normal in the USA, but don't quote me on that.

For those who haven't seen the cloudy kind...

...here some is. It's really quite pretty; you can see a similar pearlescent swirling effect in various shampoos that're trying to persuade you they're not just detergent.

Jennifer's right, though: There's no reason why ammonia in water should look like this. Bubble ammonia into water and you get a solution of ammonium hydroxide, which is clear.

The reason why cloudy ammonia is cloudy is simple enough: The manufacturers put soap in it. I've also read that there can be some oil or other instead of, or in addition to, the soap. In any case, the additive makes the substance look interesting, and may also make it a better cleaner. Probably not a better window cleaner, though, since straight ammonia-plus-water will evaporate to nothing and not leave marks, while ammonia-plus-water-plus-soap can leave streaks.

The ammonia in the above picture had been sitting undisturbed for some time, so it wasn't actually very cloudy at first...

...because a lot of its "clouds" had settled out. I took this photo first, then shook the bottle up and took the other one.

While we're on this pungent subject, I have recently accidentally created an ammonia-water generator.

We have, you see, four indoor cats. They use cat litter fast enough to make "flushable" litter a pretty quick ticket to a drain blockage, if you're dumb enough to actually flush it, which, at one point, I was.

Now, next to the phalanx of litter trays, there's a flip-top rubbish bin that I shovel the nasty stuff into for later, non-plumbing disposal.

Urine, left to sit, generates ammonia from the breakdown of urea.

(If your surname is "Fuller", then someone in your ancestry was probably rather familiar with this phenomenon.)

All that ammoniacal goodness is contained very effectively by the bin's fitted lid. It only comes out to say hello to my sinuses when I've got the bin open. It's less gross than you'd think, too; it doesn't really smell like wee and poo at all, because the wall of harsh ammonia-smell covers everything else.

When the litter stays there a bit longer than usual, it warms up a bit from its own slow decomposition. When the ambient temperature was about 20°C, I measured the temperature in the middle of the litter at around 26°C.

When this has happened and I open the bin, the ammonia-smell is really strong, and the underside of the lid is covered with droplets of quite clear, clean-looking liquid. Which is ammonium hydroxide; a solution of ammonia in water. It's probably got a high enough pH to be pretty much sterile, too; if I were more dedicated to perversity, I could bottle it and use it as a cleaner.

Oh, and while we're on the subject of well-aged urine, if you're unhinged enough to boil down aged urine, you can isolate phosphorus.