Sometimes when I plug in my headphones it seems as if I'm not receiving any vocals. Its still stereo, but I find that the headphone jack isn't completely in. What's going on here? And why does it work so effectively at removing vocals?

Simon

The quick answer: You're hearing the two stereo channels mixed, with one of them out of phase with the other.

I can't for the life of me figure out how this happened, though. In the interminable rambling below I talk about a couple of other crossed connections that can, and often do, happen, but unless there's a bit of wire stuck in the headphone socket or some other such oddity, I don't know how you could have the exact symptoms you report. Unless, of course, what you think you're hearing isn't what's actually happening, which is eminently possible since the ear is as easy to fool as the eye.

Anyway, mixing one stereo channel with an opposite-phase version of the other channel means that any component of the musical mix which is essentially monophonic - in the middle of the stereo "soundstage", the same on both channels - will be cancelled out.

Singing in popular music is, usually, pretty much in mono in the middle of the stereo mix. So mixing one side with a phase-flipped version of the other side will cancel out said singing; all you'll hear of the singer is any stereo reverb or difference in volume between the two sides (a.k.a. panning).

This technique, called Out Of Phase Stereo or OOPS, is used in this simplest form by old and/or cheap karaoke machines that let you "mute" the vocals on normal music, so you don't need a special vocal-less karaoke version of every song.

Simple OOPS doesn't work very well, because vocals are seldom exactly in mono (they usually have some stereo reverb, for instance), and if any other component of the mix - drums, bass, whatever - is also mono, then that'll be muted too. Smarter OOPS vocal-muting tries to identify and mute only the vocals, based on the pitch and possibly even the timbre of the sound.

This weirdness can come about because headphone plugs use TRS (Tip, Ring, Sleeve) connectors. TRS connectors come in a variety of sizes - the big old-fashioned 6.35mm (quarter-inch), the ubiquitous modern 3.5mm (eighth-inch), and the usually unnecessary and irritating 2.5mm (3/32 or 1/10 inch, depending on who you ask). All three-contact audio TRS connectors are, or should be, wired the same way; the tip of the plug is left channel, the ring is right channel, and the sleeve at the base of the plug is a shared ground.

(This sort of cylindrical plug connector should only be called "TRS" if it has these three contacts. Mono-audio cables with the same sort of plug, like for instance guitar leads, omit the ring contact and should therefore be called just "TS" connectors. Connectors with two ring contacts, as for instance used for stereo headsets with a microphone, should be called "TRRS". Sometimes you'll see any plug of this basic form called a "TRS" plug, though, regardless of how many contacts it actually has.)

Most headphones today have a 3.5mm plug; fancier ones...

...come with a 6.35mm adapter for it, too.

Some headphones mix it up a bit. One of these Sennheisers has a simple 3.5mm TRS plug on both ends of its cable, so you can very easily and cheaply replace the cable if it's damaged...

...but the other has a 3.5mm TRS on one end of its cable, and at the other end the cable splits into a pair of 2.5mm TS plugs, one for each side of the headphones.

If a TRS plug isn't fully inserted, contacts on the plug can touch the wrong contacts in the socket.

(This characteristic makes this shape of plug a bad fit for many applications. I once bodged up a two-voltage power-supply connection for an external SCSI drive box for, of course, my Amiga, using a 6.35mm TRS plug and socket. I avoided the dangers of connecting one voltage to the other's contact and the other voltage to the ground contact by only connecting or disconnecting the power supply when everything was turned off. Or, at least, connecting or disconnecting it really fast.)

A partially-inserted TRS plug could, for instance, leave the tip contact on the plug touching the ring contact of the socket, and the plug's ring contact not touching anything, and the sleeve of the plug still touching the sleeve of the socket, because the sleeve is much longer than the other two contacts. This sort of mis-connection will give you the signal meant for your right ear in your left ear, and no sound from the right side of the headphones.

(The sleeve of the plug is connected to the braided or foil shield of the cable, and any or all metalwork on the plug that is not the tip or ring contact will also be connected to the shield - it's all one big sleeve contact, basically. TRS sockets almost always work the same way; the socket has small tip and ring contacts, but the rest of the socket's metal is all sleeve. This makes it very easy for the sleeve of plug and socket to remain connected when the plug isn't all the way in, and if the plug's a long way out of the socket it also makes it pretty easy for the plug's ring contact to touch the socket sleeve contact.)

I encourage readers, by the way, to try this out yourselves; it's pretty much impossible to hurt your headphones or anything you plug them into by only plugging them in half-way. So do that, especially if you find my interminable blather confusing, or just want to see if you can create Simon's symptoms for yourself.

Another mis-connection could have the plug-tip touching the socket-ring, and plug-ring touching socket-sleeve. Now you'll hear the signal meant for the right side through both ears, but it'll sound weird, because it's out of phase, as mentioned above.

This is because the left and right "drivers" of the headphones (the electromagnetic transducers that actually make the sound) are, with this mis-connection, now wired in series, with the wire going "out" of the left driver that's meant to connect directly to the sleeve contact instead only being able to connect to the sleeve through the right driver and the plug's ring contact, thereby feeding the right driver "backwards".

This causes the right side to be out of phase - when the left driver is moving toward your head, the right one should be too, but now its phase is inverted and it's moving away.

There are two reasons why I'm rabbiting on about this stuff at such outrageous length. The first is that basic audio cabling like this is something that almost everybody has to deal with, and it pays to know what connects to what even if you don't intend to be soldering up any cables of your own - though basic soldering is easy to learn, cheap, and can save you quite a bit of money.

(Just yesterday, I turned a couple of not-that-cheap Apple laptop power supplies, one electrically dead and the other with a fractured and fiendish-to-repair MagSafe plug, into one working power supply with an extra-long cable. Even the dodgiest off-brand MagSafe power supplies are about $US20; a genuine Apple one is $79. With basic soldering skills and equipment, this sort of thing is a literal five-minute job.)

The second reason for this ridiculously large post is that phase problems are actually very common in home audio, and not only among people who fix their own headphones and get one set of Profanity-Allowance-consuming minuscule wires backwards.

People have been creating phase problems ever since the invention of stereo, occasionally by mis-connecting a turntable cartridge, but usually by wiring one of their stereo speakers the right way around (red terminal on the amplifier to red terminal on the speaker, and black to black) and the other the wrong way (red to black, black to red). In this case, each speaker actually is playing the signal that it should be, but one is phase-inverted.

(It doesn't really matter whether you've connected red-to-red or the other way around, as long as both speakers are the same. In theory, having both out of phase with the way they should be, but in phase with each other, could cause an audible difference, but in practice it's only detectable by golden-eared audiophiles who see no need for tiresome things like blinded tests.)

If you've got two working ears, you definitely can hear when stereo has one side out of phase. It's hard to describe, though; it's sort of like having a head cold that's blocked one of your Eustachian tubes but not the other, or how things sound when an air-pressure change has popped only one of your ears. Here's a page that explains this, with nifty audio samples including one (MP3 link) that should sound mono in the first half and out-of-phase pseudo-stereo in the second half.

Out-of-phase audio sounds different on headphones and speakers, because of the basic differences between the two devices. Headphones deliver pretty much pure left-signal to your left ear and right-signal to your right, but each of your ears hears both members of a stereo speaker pair, plus umpteen reflections and resonances from the room you're in.

For this reason, if you're listening to stereo speakers with one side out of phase, there will be strangely little bass, because low-frequency sound has a long enough wavelength that the out-of-phase speakers can mix their sound even if they're separated by a few metres. Higher-pitched centre-mixed components of the music won't cancel as much, though.

Just to make things even more complicated, sometimes it's good to reverse the phase of a subwoofer or surround speakers, to compensate for subwoofer location or the distance of the surround speakers. There's often a hardware switch on a subwoofer or a configuration option on a surround receiver that'll let you do this, or of course you can just switch the wires around or make a crossover RCA cable.

There are also some stereo recordings on which phase reversal is undetectable, because the two channels share nothing at all. Many early stereo rock tracks are like this, and are pretty much intolerable to listen to with headphones because the stereo mix puts each instrument entirely on the left or right channel. Ringo and Paul on the left, John and George on the right. Nobody minded this very much at the time, because almost everyone heard this music in the mono mix, but to make these tracks listenable with headphones you need a fancy headphone amplifier, or music-playing software, that has a "crossfeed" control, to deliberately mix some right into the left and some left into the right.

Out-of-phase mono - the same signal on both sides, but one way round on the left and the other way round on the right - kind of sounds like stereo, because you genuinely are hearing something different on each side. So what I think you, Simon, are hearing from your partially-connected headphones is a mixture of left and right, with one side's waveform inverted, the resultant mono signal being heard one way round on the left side and the other way around on the right. I just can't figure out how you could electro-mechanically get this to happen by only partially plugging in the headphones. I presume there's one contact on plug or socket that's touching two contacts on socket or plug, but I don't know which.

It is, again, entirely possible that you're not perceiving what's going on correctly; psychoacoustic effects can be powerful. But perhaps I'm just insufficiently imaginative. Any ideas (or experiment reports!), commenters?

I recently saw a news article that linked to this government page:
http://ga.water.usgs.gov/edu/earthhowmuch.html
...which says if all Earth's water (liquid, ice, freshwater, saline) was put into a sphere it would be about 860 miles in diameter.

Now I understand an 860-mile sphere is massive, so even though that sounded small I could accept it, until they state the estimated volume of water on earth at 332.5 million cubic miles.

So how do you cram 332,500,000 cubic miles into a 860 mile sphere?

Matthew

Quite easily, actually!

The volume of a sphere is four-thirds pi times the radius squared. So if the radius is 1 unit, the volume is 4.19 cubic units.

The radius of an 860-mile sphere is 430 miles. 430 cubed is 79,507,000. Four-thirds pi is about 4.1888. Multiply that by 79,507,000 and you get about 333,038,143, a number less than 0.2% larger than 332,500,000. The difference is accounted for by variations in precision in working out the number, since this is really only a ballpark figure and taking it to nine significant digits is silly.

To "sanity check" this if, like me, you always feel mildly nervous about the order of operations for a calculation like 4/3Πr^3, consider the volume of a cube 860 miles on a side.

The volume of a cube is of course just its edge-length cubed, and an edge length of 860 miles gives a volume of 636,056,000, a nice sane-sounding 1.91 times the volume of the sphere that'd neatly fit in that cube.

My own second-favourite way-to-visualise-the-quantity-of-something is that all the gold in the world (not including gold we have yet to dig up or somehow extract from seawater) would make a cube only 20 to 22 metres on a side, depending on who you ask. To help visualise the size of the cube, 21-ish-metres is about the length of two city buses parked nose to tail.

Because gold weighs 19.3 grams per cubic centimetre, though (11.16 ounces, or 10.16 troy ounces, per cubic inch), a 21-metre-on-a-side cube of gold would weigh 178,737 tonnes. So I suppose you wouldn't have to worry too much about someone stealing it.

(Unless you are very wealthy, you probably can't buy a large enough lump of gold - especially at today's outrageous prices - to really appreciate its density. At current prices, one kilogram of gold would cost you more than $US51,000. Tungsten, however, is 99.7% as dense as gold - I'm sure counterfeiters have gilded tungsten for profit many times - and it's much more affordable, though still expensive. The good people of RGB Research {here on eBay US, here on eBay UK, here on eBay Australia} have their one-kilo tungsten cylinders on sale again for a mere $US220 plus rather pricey delivery. If you can afford one, and have the slightest interest in science toys, I urge you to buy one; my own tungsten cylinder is one of my most treasured possessions. And one of the most durable, too; if the house burns down the tungsten cylinder, like my Bathsheba Grossman Metatrino, will be sitting intact in the ashes.)

My most-favourite way-to-visualise-the-quantity-of-something is that if you breathe on an ordinary marble, the thickness of the layer of condensation from your breath on the marble is approximately to scale with the thickness of the atmosphere on the earth.

(And another one, that doesn't really make anything much easier to understand but is prime stoned-party-talk, is that a human is about as much bigger than an atom as a galaxy is bigger than a human.)

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.

How do the little rectangular anti-theft tags work?

I get how the big anti-theft stickers work. They've got an obvious square spiral antenna that I presume collects enough microwatts from an incoming signal to run a little transmitter that sends another signal out.

But the little tags don't have any circuitry inside. I cut one open, and there are just some tabs of springy metal in there - two pieces next to each other, and a smaller piece separated from the other two by a clear plastic membrane.

The metal sticks to a magnet, but that's the end of my ability to figure out what it does.

Is there invisible nanotechnology in these things, or something? Hey, maybe they're a placebo!

Kim

If they're a placebo, the alarm systems in shops seem to really believe that it works.

What you're looking at there (here's a more elegant cutaway picture on Wikipedia) is called a magneto-acoustic, or acousto-magnetic, tag. Which is one of those things that doesn't really sound as if it ought to work, but does.

The first two of the three tabs inside are, I think, a couple of pieces of amorphous metal - which is quite an exotic material to be stuck to commonplace consumer items just to stop people stealing them. Amorphous metal is, in a way, the opposite of nanotechnology; it's metallic glass, special because it lacks the microscopic crystal structure of normal metals.

The third tab is a piece of less exotic, medium-coercivity metal. When that third piece is magnetised, the two other strips, which are sitting loose in their little plastic coffin, become quite easily moved by external magnetic fields. (They're amorphous metal because that's already unusually easy for external fields to move.)

The security gateways as you leave the store emit a pulsed magnetic field up in the tens of kilohertz, at the resonant frequency of the amorphous-metal strips. When next to their mildly-magnetised buddy, this quite tiny field causes the amorphous-metal tags to buzz, and to continue to buzz for a very brief moment after each pulse of the external field. This very brief "ringing" period causes a tiny change in the magnetic field of the third strip, which an antenna in the security gateway, very implausibly, detects. And off go the sirens.

The thingy at the checkout that deactivates the tags is a degaussing coil. It more-or-less demagnetises the third strip, which both reduces the magnetic sensitivity of the other two strips, and removes the field which the other two strips modulate. So now the sirens don't go off.

I am entirely unable to think about any security system without immediately trying to figure out ways to defeat it. (I try to avoid airports nowadays. They make me feel like Jackie Chan in a deckchair factory.)

One obvious but impractical way to defeat magneto-acoustic tags would be to degauss them yourself; I don't know how strong the degausser needs to be to achieve this, though. You might be able to pinch stuff if you just smuggled a CRT-screen degaussing wand into the shop, and found somewhere to plug it in.

Swiping your own rare-earth magnet across the tag would, if anything, probably make it work better (by more strongly magnetising the third strip), but I wonder if leaving a magnet or three stuck to the tag, in a Halbach array if you're fancy, might silence it. Just chopping it bodily off with a potato peeler would probably do the job too, of course, but where's the fun in that?

(If you can magnetise tags yourself with a ten-cent eBay magnet, then you could pry them off things you've bought, reactivate them, and attach them inconspicuously to things which other people may innocently carry into shops. You could, is all I'm saying.)

The square-antenna type of tag, by the way, is also pretty simple. It doesn't actually have anything fairly describable as a transmitter in it, but is rather a tuned circuit that resonates somewhere in the low megahertz. This makes it detectable, if a nearby transmitter/receiver combo rapidly sweeps its output through the relevant frequency range and looks to see if something is managing to suck up some energy at the appropriate frequency.

This kind of tag is deactivated by, essentially, blowing out the capacitor essential to their resonance with a higher-powered signal. I think a shoplifter could probably defeat these tags by just dragging a knife across them a couple of times, though, breaking the circuit. I haven't actually tried this, though, because it'd mean missing out on all of the fun of a good old-fashioned armed robbery.

Perhaps someone who's worked in retail since fancy security tags came into vogue will enlighten us in the comments.

I would also like to hear from anybody who's successfully used the "just lob the item high over the security gate and into the hands of your partner in crime" technique.

From: "japan-best.com webmaster" <postmaster@japan-best.com>
Date: Mon, 07 May 2012 22:27:24 +0900
To: dan@dansdata.com
Subject: Inclusion in one of your articles

Dear Dan

I am Marc with japan-best.com

i read your article here

http://www.dansdata.com/contact.html

and would like the possibility of include my site in it.
I have also took note of yOur paypal adress :-)

You can check us here :
japan-best.com <http://japan-best.com/en/>

I am looking forward to hearing from you and discuss that further

Have a great day

Regards
Marc

Marc, buddy, your Spam-O-Matic might need a little recalibration, there.

My contact-and-donation pages may score surprisingly high for various panhandling Google searches, but that doesn't mean it'd be a good place for you to advertise your site full of allegedly Japanese merchandise.

Including, I now see, some front-page items whose description does not match their pictures.

At first glance, Japan-Best looks like a valid online store, but the more things I click on, the more I think it may actually be a 100%-machine-built lazy-dropshipper paradise. Or, conceivably, just a fancy way of stealing credit card numbers.

Or maybe it's legit, if clumsy, but massively overpriced. Look at this hideous wristwatch, for instance; from Japan-Best, including shipping, it costs twice as much as the same item on eBay.

Between eBay and legit dealers like HobbyLink Japan, I don't think there's much reason for anybody to buy stuff from weird machine-made sites like Japan-Best. But I'm sure a little PayPal baksheesh to get some crafty links inserted in random high-PageRanked Web pages will turn that right around for you, Marc!

Myself and a friend were just reading Big Clive's "Hack your solar garden lights", and we are unsure how he came to those amp readings and the conclusion that two LEDs use less amps than one.

I am assuming we are just missing something, could you please enlighten us?

Daniel

To oversimplify, two LEDs in series have more resistance, so less current flows. But halving the current passing through an LED doesn't necessarily halve its brightness. Standard high-brightness 5mm LEDs generally have a 20-milliamp current draw on the spec sheet, but will glow from much less, and may be considerably more efficient at small currents.

The reason why this is an oversimplification is that LEDs, unlike incandescent-filament lamps, aren't just a relatively simple resistive device.

(And the "relatively" is in that sentence because not even tungsten-filament bulbs are completely straightforward. They have, for instance, a much lower resistance when cold than when operating. And reducing the power of a filament bulb will generally give you a reduction in apparent brightness that's greater than the reduction in power, because the filament will be cooler and more of its output will be down in the invisible infrared. LEDs, in contrast, only know how to make one colour, even when they're only barely creating a tiny spark of light. This is the case for white LEDs too, because to date all of those are actually blue LEDs with a phosphor coating that turns some of the blue light into other colours.)

Instead of being resistors, Light Emitting Diodes are, yes, diodes, with a constant voltage drop across them at a given temperature. But when they're lit they get warmer, causing them to pass more current and glow brighter and get warmer again, which can rapidly lead to destructive thermal runaway unless the LED is restrained in some way, by for instance limiting the source voltage so the LED will just never be able to get hot enough. Or, more commonly, by limiting the maximum possible current.

You can see how this can get complicated. (Power-supply design in general is a surprisingly tricky field.) Just running LEDs from a simple DC source via current-limiting resistors can be a bit complex; proper efficient LED drivers that deliver a set current no matter what LED you plug into them are more complicated again. (The drivers in garden lights are elegant, but like the "joule thief", not actually very efficient.)

Don't let all this put you off monkeying with garden lights, though; as Clive says, they're both easy to modify and so cheap that it doesn't matter if you wreck something. Just add some of the incredibly cheap high-brightness LEDs you can get nowadays (which I mentioned the other day), and you can make all sorts of decorative, and even useful, solar LED lights for close to no money at all.

The Oatmeal recommends sites get more traffic and Facebook likes by writing an epic love story involving cage-fighting nuns and tanks, or if that is not possible, explaining why the sun and the moon appear to be the same size in the sky.

Both of these seem right up your alley, but frankly I for some reason find the second one more interesting. Why ARE the sun and moon the same size? Is it just a bizarre coincidence, or is there some astronomical orbit reason for it?

Lucas

I'm afraid it is indeed just a fluke. Which, furthermore, starts to look less amazing when you discover that the sun and moon don't actually have a particularly spooky similarity in size.

I remember reading some flaky book when I was a kid, possibly some von Däniken claptrap or other, that made much of the extraordinarily precise apparent-size match between the 0.55-Earth-diameter moon and the 109-Earth-diameters sun. Surely this cannot be mere coincidence, hence ancient astronauts and Nazi moon bases and the various Stargate series are all documentaries et cetera.

Unfortunately for these otherwise-very-plausible speculations, the sun and moon are not actually the same size in the sky. They can be, but they usually aren't.

The earth's orbit around the sun is not perfectly circular, but it's close. On average it's one astronomical unit (oddly enough), but we're closest, 0.983 AU, in early January, and furthest, 1.017 AU, in early July. The actual sun stays the same size, so from our point of view it ranges from 31.6 to 32.7 minutes of arc.

For visual learners, that's about this much of a range:

(I made this from this NASA picture depicting a gigantic magnetic filament erupting from the surface of the sun. The same filament would not, of course, be there in both January and July.)

The moon's orbit around us is more eccentric than the earth's orbit around the sun, so the moon changes in apparent size much more dramatically than the sun does. It ranges from 29.3 to 34.1 arc-minutes or, to the same scale as the above sun picture...

...this much.

(I took that moon picture myself. Residents of the northern hemisphere are invited to stand on their heads to make it look more familiar.)

(UPDATE: I forgot to mention the moon illusion when I first put this post up. Yes, the mooon, and the sun too for that matter, seems bigger when it's near the horizon. No, it actually isn't. If anything, it's smaller!)

Here's the two ranges compared.

The only time when ordinary people really compare the size of the sun and moon is, of course, when there's a total solar eclipse. Then it really does look as if the moon neatly covers the entire sun, helpfully giving us a nice view of the corona, which is normally washed out by the much greater brightness of the body of the sun. (You can actually view the corona from the surface of the earth at other times, but you need special equipment to block out sky-glare.)

At this point, you may be wondering whether the roughly-month-long lunar size cycle and the year-long solar size cycle can coincide with an eclipse in such a way as to put a minimum-size moon in front of a maximum-size sun (well, any size of sun, really, there's not that much difference), so that the moon fails to completely obscure the sun.

Yes, it can; it's called an annular eclipse, and there's one coming shortly, though I won't be able to see it from here in Australia.

Here is a lot more information about all of this.

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.

Pretty much your standard magical catalyst-or-something, it got pimped by the Sydney Morning Herald, and those guys who say every hokey fuel saver in the world works said it works too. And then the Herald article disappeared in a way that basically said THIS ARTICLE HAS DISAPPEARED IN A SUSPICIOUS WAY, even as the Australian Government department that was alleged to be testing the device told me they'd never heard of it.

And then the Herald covered their tracks with the professionalism of a small child attempting to rearrange eight cupcakes to conceal the fact that there used to be twelve cupcakes.

(If Asher Moses wants me to ever forget he wrote that piece, and more importantly that he or one of his Herald workmates then stumbled around incompetently trying to pretend the article never existed instead of just saying "whoops, sorry" like a sensible person, he's going to have to kill me. It would appear that Twitter and the SMH actually are a bit similar, dude.)

Aaaaanyway, rejoice, for the Moletech-or-whatever fuel saver still stands ready to relieve you of a few hundred bucks while for-a-certainty paying for itself really really soon with amazing mileage gains. Entirely according to the usual script for BS molecular-magic fuel savers, the Moletech people have opened new marketing vistas and evaded any disappointing online commentary from clearly crazy people who suggest their product might not work by changing the product's name, to "Greentech".

Any doubts you may have about this clearly-unassociated-with-that-Moletech-thing-that-didn't-work product are sure to be dispelled by the new Greentech Web site, whose FAQ page currently contains the following hard evidence:

Q: How does it work?
A: Immediately effect will be observed as soon as the contact between the fuel and Greentech Molecule Enhancer was established.

The Greentech doodad comes in two parts, too, one for the fuel and one for the air intake. I think the Moletech gadget only had one. This makes all the difference, I'm sure.

On the somewhat less... slender... "Main Functions" page, the Greentech people explain that their product does all of the things that magic quantum magnetic moonbeam fuel-saving devices are always claimed to do (plus, oddly, apparently the magical removal of pollen and tobacco smoke and other such things that human beings do not like breathing from the air going into the engine, even though an engine doesn't give two slim shits about whether a bit of pollen made it through the air filter).

How is the Greentech thingy meant to do this?

Why, by reducing Van der Waals forces between fuel molecules, of course! A Canadian distributor rabbits on about this at greater length.

This, as usual, would be either study-of-physics-revolutionising instant-Nobel-prize material, or cause a slow but inevitably apocalyptic unravelling of the very fabric of the planet, depending on whether your view of fuel-saver-company quantum flapdoodle tends more towards the Larry Niven/Iain M. Banks or Peter Watts/J. G. Ballard ends of the sci-fi spectrum.

If it didn't kill us all by next year and actually did what they claim - more power, less fuel consumption, lower exhaust emissions, just like all the rest - then the Greentech doodad would, yet again, be a zillion-dollar product for sale to every maker of internal combustion engines, not something sold to end-users on the Internet.

The Greentech people are proud that they've been selling this thing for more than a decade now, but in all that time they've neither inked monster contracts with Toyota and General Motors, nor been erased by the conspiracy that's the only thing that could possibly have stopped them from doing so.

The abovementioned Canadian distributor hoped for a Sydney-Morning-Herald-like response to their product from Wheels.ca.

They didn't get it.

Thought you'd get a laugh out of this one:

http://www.ascendedhealth.com/brown-recluse/bite-treatment.htm

The best part:

Healing Frequency Resonation: These oils have been imprinted with the
universal healing frequency of 728 Hz using a modified Lakhovsky/Tesla
multi-wave generator embedded with oscillators made from large
double-tipped lemurian crystal mined from Minas Gerais, Brazil.

Eric

Dear god, the "Ascended Health" site seems to be genuine. Well, if you click on their "Buy Now" links you do at least get a PayPal page, not a "Ha! We fooled you!" message.

The danger here is subtly greater than that usually posed by using holistic universal healing frequencies, which is to say a placebo, to treat illness. The Ascended Health people claim to be able to treat the usual long list of diseases, but this one page, about treating brown recluse spider bites, is

It is generally known that brown recluse bites are Bad News. Especially among Internet-comic fans who know that the exceedingly grody picture on the Wikipedia article for loxoscelism - the results of a decent dose of brown-recluse venom in humans - is of the leg of Jeffrey Rowland, the Wigu/Overcompensating/TopatoCo guy. His depiction of himself in his comics has had a leg-scar for as long as he has.

(Rowland's story was, of course, recently severely beaten by what happened to Peter Watts. Oh, and anybody who at this point is thinking about complaining about links to scary spiders and nasty medical pictures should bear in mind the way in which I have responded to such complaints in the past. I got a million of 'em, kids.)

The thing is, though, that the brown recluse is not actually very dangerous, and even if one bites you, placebo treatment is likely to be effective. And it's an excellent ailment for sellers of useless woo-woo treatments in other ways, too.

Brown recluse bites, you see, often hardly hurt at all at first. It's actually quite difficult to persuade a brown recluse to bite you at all; about the only way for it to happen unless you are a lunatic doing it on purpose is if you put on clothes with a spider inside and thus press it up against your skin. Some spiders are aggressive (including a few of those for which my country, Australia, is so famous), but brown recluses really aren't.

(The Australian version of the forcing-the-spider-to-bite-you situation is redbacks in your boots, or, classically, lurking under the seat in the outside dunny. Redbacks aren't tremendously aggressive, but they're still likely to become quite cross if you sit on them.)

Even if you are bitten by a brown recluse, though, most bites inject little to no venom and do little to no harm. Treatment of such a bite with prayer or reiki or homeopathic antimatter will be entirely successful.

If a brown recluse manages to envenomate you only slightly, the bite will over days develop into a nasty sore that'll take forever to heal, but will heal. Unless you were already rather frail, or the sore gets badly infected, or some other complication develops, you'll once again be fine in due course no matter what treatment, genuine or woo-woo, you get.

If a brown recluse manages to envenomate you really effectively, though, you're in trouble. But the symptoms will still take days to develop.

So what we've got here is a bite that's hard to receive and detect, which may or may not do you any harm at all, and which will be separated from the actual illness it causes, if it causes any, by a significant amount of time.

This is immensely fertile ground for people to fail to correctly figure out what's going on, in both illness and treatment. A given "brown recluse bite" may actually be a bite from some other, less dangerous spider or insect. Or it may be an infected wound, or it may be some random mosquito bite or pimple that's grown in the worried mind of the patient into a terrifying situation, on account of how they're pretty sure they saw a spider yesterday and it may have been brown.

And even if you do have a real and highly envenomated recluse bite, it's not going to eat your entire body in an afternoon like necrotising fasciitis (which, again, is what Peter Watts was lucky enough to get). Hospital treatment for recluse-bite loxoscelism is basically supportive medicine to keep the patient as healthy and happy as possible, and removal of any particularly distasteful dead flesh. If the necrosis is serious enough to threaten a whole limb then the whole necrotising area will be surgically removed, but this is seldom necessary. Basically, you just keep the wound clean and wait for it to go away.

OK, so now let's suppose you've got genuine loxoscelism and you decide to treat it with mental telepathy and the singing of hymns.

Well, if you've got the rare kind that'll take a limb, you'll lose a limb, and possibly your life, because having your arm rot off is not good for you.

If you've got the much more common, much less dangerous form of loxoscelism, though, you'll just be in a lot more pain than if you were doped up in the hospital, and you'll probably wind up with a worse scar. You may manage to get blood poisoning or something, but most likely the disease will follow its natural course, and you'll recover. And believe that you were cured, unpleasant though the process was, by whatever pointless placebo treatment it was that you tried.

(There's also the possibility that woo-woo alternative-medicine treatment will actually be bad for you in and of itself. A significant subset of folk medicines are actively poisonous in one way or another. The Ascended Health "powerful synergistic mixture of special natural magnetic minerals and oils" doesn't sound very likely to be toxic if you're only rubbing it on a wound, but who knows.)

This is the great problem with unscientific medicine, which was all medicine up until the late 19th century. You don't know what the disease is, you don't know how it works, you don't know what the treatment does, you don't know what the confounding factors are, and in the end you may by pure chance actually manage to do some good, but that's not the way to bet.

This is why homeopathy was such a success when Hahnemann invented it in 1796. "Conventional medicine" at the time was likely to involve almost nothing that actually stood a chance of making the patient better, and several things that could kill people who weren't even sick. Compared to that, harmless homeopathic placebos were a giant leap forward.

Today, though, we've got treatments for a vast array of diseases that're much better than placebo. Even when you've got something like a recluse bite for which there is no direct treatment (antivenoms for recluse toxins do exist, but they have to be administered very soon after the bite, which almost never happens when the bite is hardly noticeable), there are still numerous evidence-based things you can do which are proved to make the disease less severe, or at least less unpleasant.

It is, once again, vitally important to take pains to avoid fooling yourself, because you are the easiest person to fool.

(I am aware, by the way, that Lemuria does not really have anything to do with lemurs. Lemuria, hypothesised to be the homeland of the lemurs which [[Philip Sclater]] knew of in Madagascar and India but not places logically in between, is yet another new-age trope for which the world can thank the regrettably-not-inimitable-at-all Madame Blavatsky.)

I was wondering if you'd heard of the appearance of some pseudosciencey Power Balance-esque magnetic bracelets in the new Avengers movie - and that the bracelets are actually for sale for $200 (!), endorsed by Paramount and Marvel Comics.

I first read about this on a Hijinks Ensue comment post. As a fellow skeptic and longtime reader of your blog, I thought I'd alert you to this scummy product placement.

n

Yep, the Limited Edition Colantotte Magtitan Neo Legend really does seem to combine five forms of pseudoscience, doesn't it?

It's not at all like the admittedly worthless Power Balance wristband, though. Power Balance and similar "hologram" or "ionised" bracelets don't have any identifiable physical properties, or effect on users, that a non-"energy"-enhancing silicone rubber wristband doesn't have, as long of course as the user believes their bracelet is special.

But the Magtitan Whatever Edition has magnets in it. And, as we all know, magnets can do anything.

This is sort of like the problem with debunking psychics, where the true believers say "OK, Mr A proved to be a fake, but Ms B must be genuine!", and then move on to Mr C, Ms D and so on as each new prospect is debunked until the skeptics run out of un-wristband-enhanced energy. Nobody can ever prove that every single "quantum" talisman, psychotronic money magnet, mobile-phone antenna-booster sticker, ultrasonic mosquito repeller, magic electricity saver or miraculous fuel additive is a scam, so chronic credophiles always have a mew thing to believe in. And finding a new thing to believe in takes a lot less time than proving the thing doesn't work.

I agree that this product placement is weird, though. You'd think it'd be counterproductive.

"Do you find it entirely plausible that part of the Hulk's transformation invariably includes the manifestation of a pair of indestructible purple pants? Have you never wondered how Tony Stark can pull hundreds of gees and take hits like Superman without ever being turned to red chunky salsa inside his armour? Then do we have a health product for you!"

Well, not a little one, anyway.

Source: Flickr user Oblong

This fellow is quite magnificent, but...

Source: Flickr user lloydi

...I think something in excess of half-scale.

This smaller one's not bad either...

Source: Flickr user Neil Crosby

...(you'd want it to be good, since it's at Legoland), but the approximations are already creeping in.

Get just a little smaller and you're reduced to something like this...

Source: Flickr user pasukaru76

...of which the most one can say is that it's identifiable as a Dalek, if you squint.

If you want a Dalek roughly to scale with Lego minifigs, you're reduced to something more like...

Source: Flickr user Kaptain Kobold

...this.

I don't care how many of those you've got...

Source: Flickr user LostCarPark

...they're just silly.

Although I do give Kaptain Kobold credit for this one.

Source: Flickr user Kaptain Kobold

(Safe for work. NOT safe for work.)

These...

Source: Flickr user LostCarPark

...are silly too.

Source: Flickr user jjackowski

Nope.

Source: Flickr user pasukaru76

And this is a nice bit of microscale minimalism, but still not what you'd call faithful to the source material.

But, gentle reader, there is a solution. Though it carries a price - a price you may adjudge too high.

If you want a minifig-scale Dalek that actually looks like a Dalek, you can have it. All you must do is... I fear even to say it... is buy off-brand Lego.

I feel so dirty.

But just look at these little buggers.

Daleks! Made out of Lego-compatible blocks! Properly built up out of pieces, too, not just single-piece lumps!

Each Dalek breaks down into six major pieces and three minor ones. The baseplate, the skirt, the sucker-and-gun section, the shoulders, the neck and the head are all separate and about as Lego-compatible as it's possible for them to be, given their shape. The minor parts are the sucker, gun and eyestalk, all of which fit in holes too small for any other Lego piece or sub-component I can think of right now. The three minor pieces all have to point straight out, not swivel, but the head turns. (So do the shoulder and neck pieces, but not the sucker-and-gun section, which was never able to turn on-screen either, until 2005.)

Thanks to all of those pieces, if you want to make a Special Weapons or Emperor Dalek, it's no problem. The skirts also, of course, provide the perfect plinth for the Lego Davros torso of your choice.

(You can also just stick the head piece on top of a minifig's head and get something that doesn't really look like, but is no more ridiculous than, those preposterous helmets worn by the Daleks' human underlings in Resurrection of the Daleks.)

These not-actually-Lego Daleks are made by Character Options, who make various other licensed action figures and playsets and such. (All eleven Doctors? Fifty quid as action figures, twenty quid as pseudo-Lego.) Their "Character Building" brand has a variety of Lego-compatible Doctor Who sets, mostly just minifig-scale Doctors and companions and monsters. I bought the "Dalek Army Builder Pack", which gives you five red Daleks and nothing else. There are yellow and white Daleks in other sets, and Character Building also has one of those gashapon deals going where you can spend two pounds on a minifig from, thus far, two series, but not know what one you're going to get. You can get a blue Dalek that way if fortune favours you; any other colours, you're thus far going to have to paint yourself.

(You're also going to have to break out the paint if you want the Dalek bumps on the skirts to be a different colour from the skirts. In this scale the bumps are only about four millimetres in diameter, so it's not surprising that Character Options, um, opted, to leave them the same colour as the skirt.)

The Character Options sites lists the Army Builder Pack for £9.99, which is around $16 Australian or US, as I write this. I got mine on eBay for only £10.70 including delivery to Australia from this UK seller (here on eBay US, here on eBay Australia), but they don't have any more for sale as I write this.

There are plenty of other eBay sellers who do have stock, though; this search ought to find them all. The cheapest ones are all selling one individual Dalek parted out from a kit; the cheapest Army Builder set as I write this is £7.99 plus postage. There are plenty of sellers on Amazon, too.

The Character Building Daleks do have one flaw, though, which may be even more of a problem than the fake-Lego problem:

They look a little like Teletubby Daleks.

The Teletubby, a.k.a. Power Ranger, Daleks are the ones last seen on TV in 2010's Victory of the Daleks, when the Doctor was, for once, conclusively outmaneuvered by his enemy, and tricked into reincarnating these purestrain "New Dalek Paradigm" monsters.

(And, incidentally, there were also Spitfires in space.)

I thought Victory was a good episode (and quite funny, which counts for a lot), except for some industrial-grade schmaltz involving an android. But the new colour-coded Daleks at the end, each with their own more or less peculiar name, were not well received by the fans. Especially the... really enthusiastic fans.

The New Paradigm Daleks are big and shiny and brightly coloured, and have a great hunchbacked extension on the rear of their bodies, which gave me the impression that the props had for some reason been designed to have two human operators inside. I'm sure that isn't actually the case - these were Daleks in 2010, not Jabba the Hutt in 1983 - but there the huge lump is, or at least was.

Perhaps the Teletubbies are never coming back. Perhaps they're coming back but along with the older kinds. Who knows. (Free plot idea: The new ones are fat because they are pregnant with a much better design of Dalek.)

Anyway, these little Lego-ish ones do look a bit like them. But they're clearly not the same. The hump is less pronounced, the head isn't positioned way forward on the shoulders, the weapon-and-sucker section doesn't bulge out from almost vertical sides, and they've got that odd zipper-like grille thing on the back, but who cares.

I don't think they quite match any Dalek that's ever been seen on screen, but the Dalek props have, over the years, also failed to match each other in various ways, even if you've managed to erase the Peter Cushing Dalekmania movies and their Daleks armed with fire extinguishers from your mind.

(The New Paradigm Daleks stand significantly taller than the old ones, too; the Character Building ones are about a head taller than a standard minifig with no hat on, but are I think about the same height as the Character Building pseudo-minifigs.)

So if your interest in the racial purity of Daleks is only exceeded by their own, then you may consider these ones unacceptable. But they're really not very Teletubby-ish.

And, c'mon. Lego-compatible Dalek parts!

Haven't you always wanted the Doctor and a companion to be desperately hiding as the sound, tic-tic-tic-tic-tic-tic-tic, of robotic spider-legs approaches, and stops, and then a spray of baleful blue eye-lights spotlight them and the Mark V Travel Machine rears up, twenty feet high, dozens of its blackly shining sense globes irising open to extrude claws and tentacles and saws and injectors and suction feeders and flensers and écraseurs and deglovers, even as its battery of far-too-merciful gunsticks retract, and in a voice that breaks windows it SHRIEKS-

...well, actually these things probably won't greatly help you make that.

But if you let your kid at 'em, imagination ought to fill the gaps.

Hello there Mr. Dan. I stumbled across your site whilst googling "can you get hurt making a potato battery". Yep, I googled that.

I (clearly) know little about the electronics/cathode/anode world... but could answer lots of questions about other things non electrical. :)

In planning my son's birthday party, I am considering a potato battery station (sounds odd for a party, but trust me, it fits with the theme).

I have seen several Youtube videos with instructions and examples, some done by children. My main question before I go buy a bag o potatoes and seek out the copper wiring aisle of Walmart is: Can children be hurt doing this? Yes, us grown-up types will be there too, but is there anything I should be concerned about?

Partying Mom

It is theoretically possible to kill yourself with potato batteries, but the chance of a kid managing to achieve this is much, much lower than the chance that one of them will fall over and crack his/her skull in your bathroom, and you probably won't lie awake at night worrying about that.

I could just leave it at that, but of course I won't. This is because I think an understanding of the basics of electrochemistry, which is what potato batteries are all about, is something that all modern humans should have, even if they never put it to use.

You should know why it's warmer in the summer (it's surprising how many people incorrectly say "because then we're closer to the sun", which, even if it were true, would make summer happen at the same time for both the northern and southern hemispheres...), you should know how tax brackets work, and you should also know the basics of the technology that envelops modern humans so completely that we hardly notice it at all.

Sorry, didn't mean to lecture you. This is just something I'm rather passionate about.

Getting back to potato batteries: The power output of an individual potato, or lemon, or what-have-you, "battery" is extremely low, which is why there are few-to-no things you can power from one spud with two pieces of dissimilar metal in it.

"Battery" is in quotes up there because one tuber and two bits of metal are a single electrochemical "cell"; technically, it's not a "battery" unless it has more than one cell in it. (So, of the things sold in the supermarket as "batteries", AAs and Cs and Ds are cells, but 9V or 6V batteries, composed of six and four 1.5-volt internal cells respectively, really are batteries.)

The open-circuit voltage of any electrochemical cell is determined by the electrode potential of the materials you use for the electrodes. If you build the usual kind of potato battery with copper and zinc electrodes (like, a copper or copper-plated coin, and a zinc-plated galvanised nail), each cell will have an open-circuit voltage of 1.1V, but a current capacity into a short circuit of less than a milliamp.

The larger the surface area of the electrodes, the higher the current capacity will be. But even with really big electrodes you'll probably only get half a milliamp into a short circuit - and the more of the cell's current capacity you use, the lower its output voltage will be.

(For comparison, I just grabbed a rather old but unused off-brand "super heavy duty" - meaning, carbon-zinc, not even alkaline - AA cell out of my Drawer Of Many Batteries, and it still reads more than 1.6 volts open circuit, with a short-circuit current capacity of more than 1.5 amps. Here's a PDF datasheet for an Energizer carbon-zinc AA; they've got a sub-site devoted to these things.)

If you make multiple potato batteries and put them in series and/or parallel, you can increase the voltage and/or current capacity of the whole battery, respectively. Two cells in series (both of which can be stabbed into the same potato; just connect the copper of one cell to the zinc of the next) and you get 2.2 volts open circuit and the same miserably tiny current capacity. Two cells in parallel, and you get 1.1 volts but double the current capacity. Six cells, wired up as series strings of three with the two strings in parallel with each other, and you get 3.3 volts and double current capacity. And so on.

(Many people seem to find the concept of series and parallel circuits tricky to grasp. It's another of those bedrock pieces of information about the world that I urge everyone to learn, though, because it explains a great deal of everyday electrical things. Why does one bulb dying in a string of old Christmas lights kill the whole string? Because they're ten or twenty 12V bulbs {depending on your local mains voltage} wired in series to connect directly to the mains. Why, in contrast, can you have a couple of things turned on and a couple of things turned off all plugged into the same powerboard and have everything work? Because the powerboard's outputs are in parallel!)

Getting back to your actual question, this is how you could, if you tried very hard, kill yourself with a potato battery. 30 milliamps across the heart has a pretty good chance of stopping it, and even lower currents have upon occasion been fatal. Kids might be more susceptible, too; I don't know.

Even sweaty skin is a good enough insulator that sundry low-voltage current sources aren't dangerous - grab the terminals of a 12V car battery with bare wet hands and you probably won't even feel a tingle, though a tiny current really will be flowing through your arms and across your chest. But if you stab probes into yourself, into your hands or preferably into your chest right on either side of the heart, then an array of potato batteries big enough to deliver tens of milliamps really could, if connected to the electrodes, kill you.

(One reason why high voltage can be especially dangerous is that it can spark a hole right through the skin, giving it access to your wet salty conductive innards.)

Given, of course, that this particular means of death starts out with stabbing yourself, you could simplify the process by just stabbing your heart directly.

Hence: Not worth worrying about.

(There's also an outside chance that you could poison yourself by eating a potato or lemon or whatever that's been used as a battery for a while, because it'll now be contaminated with various metallic salts. It probably wouldn't do more than make even a small child slightly ill, though, presuming he or she somehow managed to choke the vile-tasting thing down. This situation is even less likely to happen than chest-stabbing, unless you use some particularly delicious fruit instead of a potato or lemon.)

The great problem with potato-battery demonstrations in the past was not, of course, kids somehow killing themselves, but that it was very difficult to do anything with the extremely feeble output of such a battery. Turning even a tiny motor, or lighting even a grain-of-wheat incandescent bulb, was impossible without a ridiculous number of cells. Getting a feeble glow from a grain-of-wheat bulb rated for 12 volts and 80 milliamps could perhaps be done with as few as 50 potato cells, though I suspect you'd need a hundred or more.

So potato batteries usually ended up doing something lame like powering a pocket transistor radio with a piezoelectric earpiece, which is a feat that you can more impressively achieve with no battery at all.

Today, you could similarly fail to impress the youngsters by potato-powering one of those little LCD clocks and kitchen timers that're meant to run from a couple of button cells. Two or three potato cells in series might, at a stretch, be able to run one of those. A far better target, though, is lighting a light-emitting diode (LED).

A modern high-intensity red or amber LED will only want about two volts and a couple of milliamps to light dimly, and will be quite impressively bright at only 10mA. Ten parallel strings each containing two potato cells ought to be enough to give a pretty bright light, and each two-cell "string" could be only one potato.

Here's a red LED...

(image source Flickr user trvance)

...just barely glowing from only three copper/zinc lemon cells in series...

(image source Flickr user s8)

...and here's an excellent example of multiple cells in one lemon...

(image source Flickr user s8)

...which works extremely well because it's cheating, and using a simple four-component circuit (counting the LED) called a "Joule Thief", which I learned about years ago on the excellent Web site of the inimitable Big Clive.

I recommend you provide sufficient spuds and/or lemons, electrodes and alligator-clip leads to make lots of cells, and also provide a grab-bag of water-clear high-intensity LEDs so the kids don't know what colour they've got until they get it to light up.

A lot of LEDs will not cost you a lot of money. I find it mind-blowing that the going price on eBay for a pack of a hundred mixed waterclear high-intensity LEDs has, for some time now, been under five US bucks, delivered. I suggest you get 5mm LEDs, not the 3mm ones that're the absolute cheapest, because the smaller ones are a bit fiddly even for kids' hands.

(I don't actually need any more LEDs, but I just felt morally obliged to buy this hundred-5mm-LED pack, from this seller, for $US2.99 delivered. At this price you could use these things, which were a miracle of the age in the 1970s and have for years now been revolutionising a significant portion of the lighting industry, as notice-board pins. They are literally cheaper than thumbtacks. Even the ones with three different-coloured dies and an invisibly minuscule controller chip built in cost damn close to nothing.)

You should play with this stuff yourself before the party, so you can introduce the kids to the series/parallel idea, and help them if they don't know to chain the cells nose-to-tail (copper to zinc or zinc to copper, not copper to copper or zinc to zinc), and also see which way round you have to connect the LEDs to make them work. (They're light-emitting diodes; they only work one way around. Long leg positive.)

It would also be a really good idea to get the finest, cheapest digital multimeter eBay has to offer, so you don't have to rely on licking the ends of wires to estimate how many volts your potatoes have managed to make. Every home should have a crappy ten-buck yellow plastic multimeter; you may not use it often, but it can be very handy at times. (Put it in the kitchen drawer with the screwdriver, the hammer, the random screws and washers and the polycaprolactone.)

Depending on age and disposition, the kids may figure this all out for themselves, of course. LEDs only work one way round, a battery setup that'll light a 1.8V red LED probably won't light a 3.6V blue or white one, a setup that'll light a blue LED may very satisfyingly turn a red one into...

...a friode, you can series- and parallel-wire LEDs as well as batteries...

While you're shopping for quantum-physics miracles on eBay for three cents each, you could add a couple more things that used to be super-tech and are now super-cheap: Lithium coin cells, and rare-earth magnets.

2016 (20mm diameter, 1.6mm thickness) and 2032 (3.2mm thick) coin cells aren't as cheap as LEDs; if you buy them in a supermarket or pharmacy you can pay dollars for one. Again, though, just hit eBay and you can find fifty for less than 15 US cents each.

Rare-earth magnets can be even cheaper. If you restrict this search to Buy It Now items more suited to the impatient, you can get twenty 8mm-diameter 1mm-thickness neodymium-iron-boron disks for less than ten cents each; hundred-packs drop it to about seven cents apiece.

Why am I suggesting you buy these items?

Because you can light an LED by just pressing its legs to either side of a coin cell...

(image source Flickr user spike55151)

...and if you put LEDs (preferably diffused 10mm ones, but any with legs will work), coin cells and magnets together, you get...

(image source Flickr user c3o)

..."LED throwies".

(image source Flickr user chopsueyphoto)

Which are easy to make, and awesome.

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.

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.

Bit of an early warning, but OK, fair enough, off we go to the AUSkey site, which I leave open for a while as I enter stuff for my next BAS in the other special software that apparently a few other governments inflict upon their populace. (As is traditional with such things, this program likes to pop up dialog boxes telling you to enter a date for something, when you've entered data in some other field first, and then click on the date field intending to do the thing it is haughtily preventing you from doing until you click "OK".)

A few minutes later, I come back to the AUSkey site and click "login", whereupon it tells me my session has timed out and I have to go back to the home page, which is exactly where I already was.

What session? I don't have a session yet! I haven't logged in!

OK, argh, whatever, I log in again and it tells me I don't have the special AUSkey software which I thought I had but OK, again whatever, click the thing to download the software and... back I go to the home page again.

Go through that loop again until I realise that the site is attempting to tell me via mental telepathy that it does not support Chrome. Try Firefox instead, which to the government's credit does actually work and lo, now I do have the software that I installed whenever I went through this palaver the last time, and it doesn't even seem to need 283 updates since I last used it!

Righto, off we go, let's renew our certificate...

Hang on - there doesn't seem to be an option to do that anywhere.

Gee, could that perhaps be because the AUSkey does not, in fact, ever actually expire?

Why yes, that is the case.

Did the other program really tell me to update my AUSkey?

I quit it and run it again, and it doesn't say shit this time. I could have sworn it said I had to renew my AUSkey certificate but... now I... I just don't know.

You know, part of the reason why I wish Australia didn't have any submarines is that I'm not sure anyone's ever clearly explained what purpose they're expected to serve. (They apparently performed quite well in war games against the USA, which I'm sure will make all the difference if we decide to go to war with America. Or, marginally less crazily, with China, whose attack subs only outnumber ours 59 to six, not counting their entirely insignificant five nuclear ballistic missile submarines.)

Most of the reason, though, is that I don't think an institution that can create a system like this should be be allowed anywhere near explosives.

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.

Regarding that second criterion, though, I think pretty much everyone should be interested in polycaprolactone. I'd actually go so far as to say that every home should have some, even if you're not at all "handy". Just put it in that kitchen drawer with the screwdriver, the hammer, the dried-up epoxy and the random screws and washers.

Well, put it there when you've finished playing with it, anyway.

As I explained in this rambling 2010 post about the construction of...

...this, um, thing, polycaprolactone (which is sold under several easier-to-remember brand names) is a remarkable substance.

It can be moulded like rather sticky, see-through clay when hot (its melting point is about 60°C, but it's comfortable to handle at quite high temperatures, thanks to low thermal conductivity). When it cools, it turns into a smooth opaque white plastic about as strong, and tough, and easy to shape with other tools, as nylon. You can use it to do anything you could do with nylon, except of course withstand temperatures above 60°C.

And, unlike Sugru and various other putties and clays, polycaprolactone is reusable - just heat it up again. It'll also last forever on the shelf, and isn't even toxic, unless you set it on fire and inhale deeply.

You need hot water to soften polycaprolactone, but that's the only thing remotely dangerous or difficult about this stuff. Any child old enough to boil water without supervision can use polycaprolactone to make, fix or modify things. Because you can reuse it as much as you like, polycaprolactone is also an excellent do-it-yourself material for klutzy adults.

I spent a while in the 2010 post talking about where to find polycaprolactone, and what it cost. At the time, it wasn't hard to find the stuff here in Australia, but it was a bit expensive.

Now one Peter Edmunds, the proprietor of plastimake.com, is selling polycaprolactone locally for good prices.

Plastimake-branded polycaprolactone comes as the same white granules as pretty much every other brand. ("Friendly Plastic"-branded polycaprolactone is rather more expensive, but can be had in numerous colours and finishes.) As I write this, there are only two package sizes available from Plastimake; a hundred grams is $AU10 including delivery anywhere in the country, and 800-gram jars are $AU30, plus a flat fee of $AU10 delivery for as many jars as you like. They accept PayPal or credit cards for payment.

(Plastimake sell on eBay as well. Prices are the same.)

For comparison, Jaycar are still selling Polymorph-branded polycaprolactone in Australia. Their pricing starts at $AU11.50 for 100 grams - plus delivery, if you're buying mail-order - and drops to $AU8.95 per hundred grams if you're buying a kilo or more.

So if you're building your own Plastic Pal Who's Fun to Be With and want four kilos of the stuff - which is quite a lot, because polycaprolactone is only slightly denser than water - Jaycar will relieve you of $AU368 including road-freight delivery, versus only $160 delivered from Plastimake.

The UK eBay dealer (on ebay.com, on ebay.co.uk) that I recommended in the last post is still selling Polymorph-branded polycaprolactone, too. A kilo from them is £15.10 (about $AU23, as I write this) plus international delivery, which currently isn't specified for this largest size. If four one-kilo bags cost the same to send to Australia as four kilos worth of their 750-gram bags, though, the delivered price for four kilos would be about a hundred quid, or $AU153.

So Plastimake are ahead by a bit for small amounts - and if you've never played with polycaprolactone before, a hundred-gram bag will be plenty to give you the idea - and they charge about the same for large amounts delivered to Australian customers as the best eBay dealer I've found.

(If you want to place a really big order, you can also contact Plastimake for a further discount.)

Plastimake have a good site, too. In addition to the usual simple instructions, there's a big page of example projects, containing the various simple repair projects you'd expect, plus...

...eyelets for a rustic fishing rod...

...an item of headwear which many Australians will recognise...

...some quite impressive sculptures...

...and that most prosaic of all kitchen accessories, the form-fitted salami cap.

Plastimake also have a page of techniques, including colouring the plastic (as seen in the rose sculpture), making thin sheets, and alternative heating techniques.

Plastimake are brand new, so I suppose it's possible that Peter Edmunds will turn out to take your money and run, or something. Presuming he is not a rip-off artist or crazy person, though, there's really no excuse any more for Australians to remain polycaprolactone-less.

The stuff really is very fun, very useful and very easy to work with, and it tremendously appeals to the large penny-pinching lobe of my brain. It'll never go stale or dry out, and if you drill or carve something you've made out of it, you can collect and reuse even tiny shavings.

Highly recommended.