...of an impressive piece of antique finger-grabbing agricultural equipment, and suggested it as another illustration for the "pulley paradox". Again, if you don't know about crowned pulleys, contraptions like this look offensively impossible.
As a weekend project, I suggest commenters point to the most belt-and-pulley-infested machinery they can find on the Web.
I am also pleased to note that unless the corporate copyright enthusiasts manage to extend terms yet again, the works of W. Heath Robinson should pass into the public domain at the end of 2014.
(A few works illustrated by Robinson are already in the public domain, but I don't think any of the stuff for which he's most famous is, yet.)
why do some things glow brightly in colours OTHER THAN BLUE when illuminated by a blue LED flashlight? Is it fluorescence? But doesn't that only happen under ultraviolet light?
Does this mean my blue LED flashlight has UV output? it's incredibly bright, but is it actually even brighter and more dangerous than it looks?
Ant
First up: I highly recommend coloured LED flashlights. They let you do this!
The above animation accurately reproduces what it was like for me selecting the images to use to illustrate this post, except I was doing it fullscreen on a 30-inch monitor, and so almost neutralised my neurons.
(If you're using Chrome and are now hammering away on the escape key in a desperate attempt to make this brain-slapping animation stop, allow me to suggest the GIF Stopper extension.)
In the olden days, the only coloured portable lights normal humans could afford used an incandescent bulb, with a coloured filter over it. This was incredibly inefficient, and usually didn't even give you one tightly-defined wavelength of light. Your green-filtered flashlight probably still emitted some red and blue.
Today, you can get high-intensity coloured LEDs with a very tight band of output frequencies; no blue in your green, no green in your red. I think the best-value options are the coloured variants of the Ultrafire 501B lights.
I reviewed a white 501B years ago here, but this line of lights still sells well today, because they're basically just SureFire knockoffs with standardised lamps and battery compartments. So you can today buy a white 501B that's quite a bit brighter than the one I reviewed, or upgrade your old 501B with a newer interchangeable lamp, or stick a cheap coloured Ultrafire lamp in your old SureFire incandescent flashlight, et cetera. As long as you stick with a single 18650 lithium rechargeable or two rechargeable or non-rechargeable 123-size cells. Any cheap LED module that's meant to fit in a a flashlight like this should work.
(As Fallingwater points out in the comments, there are also lamps this same shape that want a very different input voltage, and the dirt-cheap lamps may not work very well for various reasons. I think all of the cheap coloured lamps are for one or two lithium cells, though, and they're low-powered by "tactical flashlight" standards so don't have heat problems either. These lamps work from one or two cells because they have a multi-voltage driver. Incandescent bulbs are not this tolerant. Standard small two-123-cell SureFire-type lights with incandescent bulbs will produce a dim orange light from a single 18650. If you somehow manage to drive an incandescent bulb from twice as many cells as it expects, it will die immediately.)
Here's an eBay search that finds a bunch of coloured Ultrafire flashlights and lamps. The lamps start at $US9.99 delivered, but a whole flashlight (without batteries) is under $US15 delivered.
A red, a green and a blue Ultrafire 501B, plus three 18650s and a charger from eBay will only cost you about $US50 all told. The cheapest dealers all have free shipping, too, so you can buy the lights one at a time and not lose any money.
I'd really get all of them, though, and I don't even go to raves. It's just so much fun chucking large amounts of coloured light around. And yes, you do get a pretty decent white-ish light if you shine them all at the same thing.
(See also the positively antiquated Technology Associates "Rave'n 2", which I reviewed more than ten years ago and which I think they still sell. It's still fun, too.)
So. Where was I? Oh yes, fluorescence.
Fluorescence happens when a substance absorbs some kind of radiation, usually light, and then emits light of its own.
It happens when the incoming energy, usually a photon, "excites" an electron to a higher quantum state. When the electron then "relaxes" back to its ground state, it loses some energy to heat and emits the rest as a new photon.
Since the energy and frequency of a photon are directly related, and the outgoing photon is less energetic than the incoming one was, one-photon fluorescence like this only works "downward" in the ROYGBIV spectrum. You'll only see visible-light fluorescence when you're illuminating a fluorescent object with light closer to the blue end of the spectrum than the colour the object fluoresces.
("Upwards" fluorescence is actually possible, when two photons are absorbed but only one emitted. I think this is pretty much unknown in everyday, visible-light fluorescence, though.)
Ultraviolet light is beyond the blue end of the visible spectrum, so it can cause fluorescence in any visible colour. But there's no rule that says the incoming light can't be visible; it just has to be further up the spectrum than the colour of fluorescence it creates.
So here are some brightly-coloured objects from around my house, illuminated by tungsten-filament bulbs. Some of the dyes used to colour many modern polymers are highly fluorescent; shining an ultraviolet light around your house is the best way to find them, but a blue LED flashlight will do a good job too.
A red flashlight's no use, though. It's probably possible for red light to cause visible fluorescence that's even deeper into the red, but you'd probably need a spectrometer to distinguish it from simple reflection of the illuminating light.
Here, we see what basic colour theory says we should. All we're seeing is the red light that bounces off the scene, so everything is shades of red, and the less red there is in the colour of an object, the less of the incoming light will bounce off it and the closer to black it will look.
Go to green light, though - not even blue! - and suddenly fluorescence is happening. The red Gakken mini theremin (as hard to play as a full-sized theremin, but with the mellow, soothing tone of a Stylophone! Buy one today!), and the red rubber Escher's solid (sold as a dog chew toy, of all things, at my local discount shop), and the red crooked dice, are behaving as basic colour theory says they should. There's no green in them, so they look black.
The orange parts of the Nerf guns, though, are cheerfully fluorescing under the bright green light.
(Actually, only the little "Secret Strike" is a Nerf product; the double-barrelled gun is a Buzz Bee Double Shot, which ejects the empty shells when you break it open!)
I think the yellow parts of the toy guns may be fluorescing a bit under green as well. They mainly look yellow only in comparison with the fluorescing orange plastic (as per this amazing optical illusion), and my digital camera certainly isn't a calibrated colourimeter, but there's still a significant amount of red in there with the bouncing green. That adds up to at least a yellow-ish green.
The length of red paracord (useful for all sorts of things, and also the only flexible string I've found that Joey's little razor teeth don't go straight through) and the carapace of the crab Hexbug, aren't as fluorescent as the plastic, but they're having a go.
Oh, and check out the two HobermanSwitch Pitch balls. One is green and orange and is fluorescing a little and reflecting rather more in the green light; the other is blue and magenta, and is hardly fluorescing at all.
(The Switch Pitch is, I think, one of the greatest fiddle-toys ever invented. I know this post's littered with affiliate links, but seriously, buy a Switch Pitch, if you can. Not everything Hoberman make is a classic; the Brain Twist, for instance, is a worthy attempt at Hoberman-ifying a Rubik's Cube, but I reckon it's more of an ornament than a toy. But the Switch Pitch and the tougher, hard-to-find Switch Kick, are brilliant.)
OK, on to the blue light that started this interminable thing.
Now the lower-fluorescers from the green-lit shot are fluorescing with more enthusiasm, the things that never fluoresced in the green are still sticking to pre-quantum-physics colour theory, and the orange plastic has gone nuts. There's a pretty sizeable energy gap between LED-blue and that orange, so it's sucking up and spitting out electrons photons with great enthusiasm.
My own store of quantum energy ran out before I made an actual UV-lit version of the picture, but I could pretty much just Photoshop one up in less time. All of the fluorescing things in the blue-lit image would look much the same under UV, and everything else would be invisible. Or, more realistically, you'd see everything else in faint blue, because the ultraviolet compact-fluorescent lamps I've got here emit a fair bit of visible blue-violet light along with the UV.
You can get UV LEDs that emit proper near-UV light (not the more dangerous UV-B or even more dangerous "germicidal" UV-C) with very little visible output. Most "UV" LED flashlights use cheaper purple LEDs, though, which may have a bit of near-UV output but basically just do what a blue LED light does, only more so.
And yes, you can get UV Ultrafires, too, but I don't know which flavour of "UV" LED they contain.
If you see a welder marking out a piece of metal with what looks like chalk, or a tailor doing the same to cloth, they're likely to not be using standard blackboard chalk.
Plain chalk is calcite, one of the several forms calcium carbonate can take. Welders' and tailors' chalk, on the other hand, is "French chalk", a stick of solid talc, magnesium silicate. Ground up, talc is the base for talcum powder.
This was just another of the pieces of vaguely interlinked data that float around in my mind, until I discovered I could buy ten 125-by-12-by-5mm (about 5 by 0.5 by 0.2 inches) sticks of French chalk, plus a sliding metal holder with a pocket clip, for a grand total of 4.8 Euros including delivery to me here in Australia.
(As I write this, that's about $US5.90, £3.80, or $AU5.70. Here's the eBay listing, here's the seller's store, here it is on eBay Australia, and here on eBay UK.)
The talc sticks are unexpectedly beautiful objects. They're very smooth, despite visible sawblade marks on the sides...
...and they have the slippery feel of soapstone. Or, more accurately, soapstone has the slippery feel of talc, because soapstone is a metamorphic talc-schist.
They're moderately fragile, of course, but quite dense, and much harder-wearing than calcite chalk. And I think they've been cut from solid mined blocks of natural talc, because they all have slight marks and veins and other inconsistencies, which become more apparent...
I think there are two reasons why you'd want to use talc rather than calcite for marking out. First, the mark can be more accurate, because although talc is the definitive soft material (scoring one on the Mohs hardness scale), it's actually quite a bit harder and sturdier than a stick of blackboard chalk, and thus won't wear much in the course of one line across metal or cloth. Calcite itself is much harder than talc, but calcite chalk is deliberately made porous and weak; French-chalk sticks are solid and waterproof. A stick of solid non-porous white calcite would rip the paint straight off your blackboard.
The second and probably more important reason to prefer French chalk for marking steel or cloth is that when you draw with a talc stick, you get a line of freshly-created talcum powder. I think this will stick better to a surface than a normal chalk mark, and resist being rubbed or shaken off as you join and cut and otherwise handle your metal or cloth.
(There could be chemical reasons for the choice too, for welders at least. Magnesium silicate is used in some high-temperature pottery glazes, and it's also used as a welding flux, for gas welding at least.)
The ability to precisely draw talcum powder onto a surface could be mechanically useful, too. When I was a kid I used talcum powder to lubricate Technic Lego contraptions, because it doesn't make much of a mess and doesn't attack plastic. Graphite powder, which you can similarly topically apply with a soft pencil or artists' graphite stick, is a better dry lubricant - but it turns everything black and conducts electricity, which may or may not be desirable.
Talc is also a high-temperature electrical insulator. You could easily carve and drill small custom insulators out of French-chalk sticks, or use them unmodified as formers for heating elements or what-have-you.
What I'm actually likely to do with my sticks of talc, of course, is just fiddle with them aimlessly and admire them for their surprising beauty.
Yes, these are ranks of little pointy blades with angled chisel tips.
They're all about five centimetres long, and when you use the implement of which they are a part they protrude about 19mm (3/4 of an inch) into some flesh.
Which you later eat.
I don't like cooking. But I can cook a steak. High heat, short time, remember to turn off the smoke detector nearest the kitchen, job done. The less you muck around with it, the better.
(Actually, those annoying scientific-cooking people suggest that frequent turning of a steak is desirable. A religious war will clearly result. The losers get eaten.)
I'm not made of money, though. So the cheaper my steak-meat can be, the better.
I can get a kilo of thick-cut boneless chuck from the local Aldi for eight bucks Australian. That's good for two large steak dinners, or four more reasonable ones. And there's nothing wrong with the flavour of chuck, or what's locally known as "gravy beef" (boned shin), or any number of other cuts from less fashionable parts of the cow. The problem, of course, is that they're full of gristle and connective tissue.
It's surprising how tender even cheap steak can be if you don't overcook it, but the really cheap stuff goes way over the "just needs a lot of chewing" line up into the unacceptable realm where it seems that no amount of chewing is sufficient to actually disintegrate the stuff.
The traditional solution to this problem is, of course, the tenderiser. Which, according to most people, is some kind of mallet, generally resembling a miniaturised version of Kannuki the Giant's signature weapon.
Beating a steak senseless will indeed make it much less chewy, but squashing is not actually a very good way of breaking up gristle; it can take a surprisingly long time, and invariably leaves you with a mutilated beef pancake. That's perfectly acceptable for some dishes, but pulverised beef is pretty close to just being mincemeat ("ground beef", in US parlance). You might as well buy mince in the first place and make meatloaf or rissoles or something, if you ask me.
You can also tenderise meat chemically, with an enzyme or just by letting it go a bit rotten. I haven't tried enzyme tenderisation, but dry-aging my own beef and then shaving off the mould isn't my idea of an appetising activity.
A while ago, though, this Cool Tools post alerted me to the existence of tenderisers that use blades, instead of brute force.
Intrigued by the idea, I tried just laying a cheap steak out on a cutting board and stabbing the hell out of it, all over on both sides, with a couple of little paring knives.
I highly recommend any penny-pinching carnivore try this. It doesn't take very long, and the results are excellent. The meat looks, and cooks, much the same as it did before, but all the stringy stuff has been pre-separated into short pieces. And if you want to marinate your steak in something, the stab-wounds get a lot more flavour into the meat. (I also tried pouring marinade on the steak and then stabbing it, which worked even better but was somewhat messy.)
Satisfied that the technique worked, it was clearly time for me to purchase a kitchen gadget that does the stabbing in a more organised way. The Cool Tools post recommends a "Jaccard SuperTendermatic", with 48 blades in three ranks of 16, which lists on Amazon for $US23.76 ex delivery (cheap to free within the USA, expensive everywhere else), at time of writing.
I'll betcha one of the swish shops in the next suburb over from me has name-brand blade tenderisers too, and I'll also betcha they charge at least a hundred bucks for one.
Instead, I hit eBay and bought a brandless 48-blade unit for a princely $AU17.98 including delivery to Australia, from a Hong Kong eBay seller. That was almost two years ago now; I didn't want to write anything about it before I was sure that the cheap brandless version wouldn't fall apart, maim the user, commit the signature kitchen-gadget failure of being impossible to clean, et cetera.
It doesn't, and I can't imagine that the more expensive brand-name ones work any better.
(That eBay search doesn't seem to be geo-targeting very well for me here in Australia; here's one that ought to only turn up items that can be shipped here.)
UPDATE: As mentioned in the comments below, there are rotary blade tenderisers as well, that roll like a pizza cutter. Here's a search that I think finds them a bit more effectively than the above searches.
UPDATE 2: Renowned crapvendors DealExtreme also now have 48-blade tenderisers similar to the one I've got. There's a black one and a white one, each for $US17.40 including delivery to anywhere, which I think undercuts the eBay dealers by a little.
It's easy enough to use a blade tenderiser: You just put it on the meat and press down. The blades slide out of slots in a guard on the bottom, and when you release the pressure springs retract the blades again.
The tougher the gristle you're tenderising, the harder it'll grip the blades and resist them retracting. Basically, the more resistance to the blades a given location on the meat has, and the more impressive the crunching sound when you stab it, the more times that area should be stabbed.
The springs are the only weak point of this design, I think. The standard springs in the tenderiser I got were very stiff and heavily pre-loaded, which meant they retracted the blades out of the meat very well, but forced you to push down on top of the meat too hard in the first place, squashing the steak.
I removed the blades and took the handle apart (four simple screws), removed the standard internal springs, and added the natty external coil-over replacements you see in the picture:
They're shock springs for a model car, and they aren't strong enough to retract the blades by themselves, so I have to push the guard and handle apart a bit myself, but the steak is minimally squashed. I think that's a good trade-off.
The very cheapest blade tenderisers found by that eBay search have only 16 blades, and the spring setup might be better for those. The standard springs don't totally squish the life out of the meat, either; I am unsure how much of my motivation to modify the thing came from an actual need to do so and how much was just my desire to tinker with things.
Apart from that, though, I've had no problems with this thing at all. It works, and it keeps working. I've deliberately bought the toughest cuts of beef I can find - even when they're not actually any cheaper than a slab of chuck - and it's worked, quite quickly, on all of them.
The blade cartridge is removable for cleaning. You push the blue button on the handle to one side and press the tenderiser down on a breadboard, and the blade cartridge pops out the top. The guard at the bottom slides out for cleaning, too. Both of these parts can go in the dishwasher.
Actually, you can put the handle assembly, or the whole assembled tenderiser, in the dishwasher if you like. If you do, though, water will get into the handle, and not want to come out.
The only parts that contact the meat are the blades, the slotted guard and the edge of the guard-holding frame, though, so you can dishwash the removable parts and quickly scrub the frame by hand. As I said in my old review of the AeroPress coffee maker, "impossible to clean" is right up there with "does not actually work" in the list of Mortal Kitchen-Gadget Sins. My blade tenderiser does not have that problem.
Even if you don't have any trouble affording fancy naturally-tender steak, a blade tenderiser could come in handy to make meat more marinatable, or any other time you need a lot of little slits cut in something or someone.
If your grocery budget is tighter, though, one of these things can pay for itself the first time you use it for a family meal. You can even use it after you cook a steak, if there's a gristly bit you missed.
How come NASA spacecraft need all that heat shielding, but SpaceShipOne and Two don't? Does this have something to do with escape velocity - they don't go that fast, so they fall back down when the engines stop and don't have to re-enter. But they do get outside the atmosphere, right? Is there more than one kind of re-entry?
Cherie
There's no clear line where "the atmosphere" stops. By convention, the Kármán line at an altitude of 100 kilometres is treated as the end of the atmosphere; SpaceShipOne made it to 112 kilometres, and SpaceShipTwo is intended to do the same, but with more people on board. But satellites in low orbit well above the hundred-kilometre line need periodic re-boosting to compensate for the drag of the tenuous outer reaches of the atmosphere. Take the International Space Station, for instance; it orbits from 330 to 410 kilometres up, but still needs periodic re-boosting to prevent its orbit decaying. This goes for anything else delivered or serviced by the Space Shuttle, too; inability to reach high orbit was one of the Shuttle's numerous shortcomings.
(The Shuttle carried some satellites that ended up in high orbits, and even space probes that left earth behind entirely, but those payloads needed their own booster rockets for the second part of the trip.)
(Oh, and orbital decay also shows up in umpteen Star Trek episodes as another Acme Mechanically-Assisted Plot-Tensioner, even when the Enterprise seems to be orbiting way above the conceivable atmosphere of any earth-like planet. Presumably they deliberately keep themselves in a super-slow pseudo-orbit by use of engine power, because... tech tech tech.)
You could say that "re-entry" means any trip from orbital altitude back into the atmosphere, but what most people mean when they use the term is a trip from an actual orbit back into the atmosphere. That's where the big difference lies, because orbital velocity is high.
Low-orbital velocity is particularly high, because the closer an orbiting object is to the thing that it's orbiting, the stronger will be the gravitational pull on it, and the higher its orbital speed must be, for it to actually be in orbit and not just fall back down.
The earth, orbiting approximately 150 million kilometres from the (very large mass of the) sun, takes a year to go around it once, travelling at about thirty kilometres per second.
The moon orbits approximately 385,000 kilometres from the earth; if the earth had the mass of the sun then the moon's orbit would be extremely fast at that relatively small distance - Mercury, orbits the sun at an average distance of about 58 million kilometres, and travels at about 48 kilometres per second. But because the earth is much less massive than the sun, the moon takes 27.3 days to go around us once, travelling at only about one kilometre per second relative to us.
The International Space Station's low orbit takes it around the planet in only about ninety minutes; it therefore travels at about 7.7 kilometres per second, more than 22 times the speed of sound at sea level.
Re-entry is still a problem even if you're out in a very distant and slow orbit, though, because you can't just teleport from that distant orbit to the edge of the atmosphere. You have to use something - rockets, or some gravity-assist trick around some other body - to reduce your orbital velocity, putting you on a new orbit that intersects the planet's atmosphere, preferably in a survivable way.
That orbital adjustment reduces your speed relative to the planet, but then your new elliptical path means you fall toward the planet at greater and greater speed. Five hours before splashdown at the end of the Apollo 11 mission, the spacecraft was about 76,000 kilometres from the earth and approaching the planet at less than three kilometres per second. Five and a half hours later, as the spacecraft started to catch some real atmosphere and lose radio contact, they were still about 3,000 kilometres from their splashdown point (including a large diagonal component, since they weren't plunging straight down toward the planet), and were now moving at eleven kilometres per second.
(There's a lot more complexity to orbits and de-orbiting in the real world, of course, not least because many orbits are far from circular, with a slow portion further from the planet and a fast portion closer to it. Such orbits can be ratheruseful, and various advanced and less-advanced simulators exist to help you get a feel for them.)
So one way or another, a return to the earth from orbit or from a trip to some other part of the solar system involves very high speeds. Such high speeds, in fact, that friction with the air contributes little to the heating effect; it's air piling up in front of you and trying to get out of your way, and being heated by hypersonic compression, that creates the glowing plasma halo and glowing-hot heat shields on re-entering spacecraft.
You can avoid all of this if, like SpaceShipOne and Two and other "sub-orbital" vessels, you never get anywhere near orbital velocity, and just fly up until the sky is black and the earth is curved, then fall back down. When you start to fall there's little air resistance and almost as much gravity as at the surface of the earth (even the International Space Station is close enough to the earth that it's subject to gravity about nine-tenths as strong as at sea level), so you can get up to some moderately impressive speeds by aeroplane standards. But you're a long way from true re-entry speed.
For comparison, the fastest aircraft humans have ever managed to make that truly qualifies as an aircraft - takes off and lands under its own power, can be refuelled and re-used, has enough fuel to fly a reasonable distance, carries living humans and usually keeps them that way - is the Lockheed SR-71 spy plane. Most of the SR-71's technology remains impressive today and was nearly miraculous in 1964, but the thing was such a nuisance to operate (and was largely superseded by satellites and drones) that it's now been retired in favour of its 1950s predecessor, the glider-like U-2, maximum speed only impressive by World War II standards.
Flat out, with its skin hot enough to melt lead and five kilograms of fuel going into the engines per second, the SR-71 could manage about one kilometre per second.
That's nine times the speed of the fastest production car, three times the land speed record, and quite close to the muzzle velocity of the most outrageously fast rifle bullets. But any random piece of dead-satellite or rocket-casing space junk that fireballs its way to destruction in the atmosphere is pretty much certain to beat the SR-71 by a factor of at least ten. Space Shuttle re-entry was carefully controlled to get it under nine kilometres per second before it started really heating up, but you can see why it was such a big deal when Columbia had a hole the size of a saucer in one leading edge.
You can avoid all this, too, if you've got a lot more engine power to play with. Come up with a sci-fi drive that can deliver lots of thrust for long periods of time with little vehicle mass (in technical terms, both large thrust and very high specific impulse; the closest we've managed to come to these goals has been strangely unpopular...), and you can leave the atmosphere as slowly as you like, accelerate to orbital velocity as slowly as you like, and generally Superman your way around the solar system without having to endlessly account for every joule and newton lest you end up drifting to Neptune while your air runs out, or turn into an array of orange streaks across the sky.
This is where "escape velocity" comes in, too. Escape velocity (more correctly, in physics terms, escape speed, since direction is irrelevant) is how fast you need to be going, from wherever you currently are, to break free of the gravity of a given body. If you're at sea level on an earth with a magic spaceship that is not subject to air resistance, then 11.2 kilometres per second is the speed you need. If you shoot off in any direction (even, theoretically, through the planet, if your magic spaceship is also not subject to ground resistance...) at 11.2 kilometres per second, you're not going to come back down.
Escape velocity on the moon (where air resistance really isn't a problem) is only 2.4 kilometres per second, but Alan Shepard's golf balls definitely did come back down. They probably wouldn't have on Phobos or Deimos, though, because those tiny bodies' escape velocities are only 11.3 and 5.6 metres per second, respectively.
Escape velocity isn't of much direct relevance to Earth-launched spacecraft, though, because something shot out of an 11.2-kilometre-per-second cannon at sea level will definitely come back down after atmospheric drag eats most of that speed. The great problem of getting things up out of our atmosphere and gravity well when all you have to propel them are poxy chemical rockets is finding a way to strike a balance between having lots of rocket power, and using most of that power just to launch the fuel and engines that you need to launch the fuel and engines that you need to launch... You get the idea.
I realize you're probably sick to death of hearing about PFCscams, but this might amuse you anyway: I just got a phone call from a heavily-accented call-center voice purporting to be part of an energy-saving campaign by my electricity provider, Hydro-Quebec. They promised to send me a gadget which I would plug into any outlet and which would reduce my electricity consumption 30-40%.
(Initially I thought it might be a Kill-A-Watt or similar, which I would actually use, or could if my ancient inefficient appliances didn't belong to my landlord.)
When I asked how it worked, they claimed it contained "three special capacitors" and that it reduced some sort of ill-defined stray currents in my wires, and that it would reduce what was read on my electricity meter by the above 30-40%. Initially they gave the impression they were going to just send it to me, which I would have gleefully accepted so that I could dissect it and demonstrate its non-function. But it transpired that they were actually offering me a "great deal" and a "once in a lifetime offer" - yes, those are the words they used - of 50% off on its $400 price.
Once it was clear I wasn't going to get a piece of hardware for skewering, I suddenly found I had better things to do. I called Hydro-Quebec and they know there are people doing this, they had a security department number to hand (which referred me to the Canadian Anti-Fraud Office, which isn't open), but I was kind of surprised to get it at my home number.
Anne
Yes, I am just a little tired of bogus power savers, having written about them here, here, here and here on Dan's Data, and here, here, here, here and here on this blog.
But it bears re-re-re-repeating, here and elsewhere, because people are still selling these things (and removing all doubt in the comments of relevant blog posts...), and innocent people are still buying them. The more frequently this message is repeated, the more of a public service it does:
Magic power savers that're somehow meant to substantially reduce your household (or small business) electricity bill by hazily-described means involving capacitors, power factor or even stranger allegedtechnology are, withoutexception, scams. Power factor is a real thing and so is power factor correction, but household and small-business electricity consumers are almost never billed by power factor - spinning-disc electricity meters can't even measure it - and magic one-size-fits-all power-factor-correcting gizmoes don't actually even do what they're supposed to. The components inside these things aren't necessarily even connected. So even if you were billed by power factor, these gadgets would not improve it.
I have, to date, not had the pleasure of some guy with an Indian accent trying to sell me a magic power saver over the phone. Indian dudes ringing the doorbell and trying to get me to change my electricity supplier, yes; phone solicitations for power savers, no.
(The door-to-door guys are probably having a pretty bad time. I presume someone's making out like a bandit hiring Indian kids for a "working holiday" in beautiful Australia, then leaving the unfortunate workers stuck in yet another of those godforsaken semi-scammish door-to-door sales jobs that only pay by commission and have all sorts of outrageous requirements designed to soak up what money the poor bastards do manage to make. The door-to-door electricity guys, here in Australia where the power industry is still well enough regulated that there are no real "scam" providers as far as I know, are kind of like the Kirbyvacuum or Cutco knife salespeople, selling a legitimate, if overpriced, product in an unpleasant way. They are, at least, not selling white-van loudspeakers, or fake health insurance to grandmas.)
My household has, however, been enjoying the attentions of another breed of Indian-accent phone-scammers. These guys, invariably identifiable thanks to the distinctive autodialer pause when you pick up the phone, were calling us a couple of times a week, though I think they've been quiet for a little while now. We may have finally persuaded them to stop, or perhaps they got busted. Or, more plausibly, they've submerged and departed for a while to avoid being busted.
Aaaaanyway, these guys usually say they're from Microsoft or something, and tell you there's something terribly wrong with your computer, and you need to go to their Web site and install some malware to fix the problem.
Anne (my Anne, not the Anne at the top of this post) has frequently asked these callers why they do not seek honest employment. The next time I pick up a call from them, I think I'll pretend to be racist.
"Is there, do you know, a single honest man anywhere in India? Clearly the British need to return and take you naughty little children firmly in hand once again. You silly little dusky monkeys, bless your souls, simply cannot grasp the white man's honour, can you? It's really not your fault; you simply cannot tell right from wrong. We blame ourselves, you know. It was foolish of us to trust you, with your tiny, adorable brains, to govern yourselves."
The Register had this story; it paraphrases a study from Pediatrics but includes this paragraph:
The incidents are no laughing matter, as a swallowed button cell can generate sufficient current to burn a hole in a child's oesophagus, from the inside, without the child displaying any obvious symptoms. Acid can also injure. Even batteries that appear depleted, inasmuch as they can no longer power electrical devices, can inflict these injuries.
Is it just me, or is the claim that a mostly-depleted button cell can "burn a hole in a child's esophagus" via electrical current a complete and obvious impossibility? By leaking strongly acidic or basic electrolyte I can buy, but by electrical action?
Charles
In brief: Yes, the problem here is burning, and it can be very serious. But it's not electrical burning, it's chemical burning, specifically as a result of electrolysis of tissue fluids. And if a battery makes it to the stomach, the swallower is likely to be OK; it's only if it lodges in the oesophagus that big trouble is likely to result.
Well, that's what I learned in the course of writing the following Wall O' Text, anyway.
Whenever you find yourself wondering about some oddball medical news, you should proceed directly to PubMed.
(This is particularly important if you got the news from a newspaper or TV show, many of which can be relied upon to get almost all science news solidlywrong. Mass-media science reporting is sometimes good, but it's veryoftenterrible, for surprisingly complex reasons. Whenever I hear some interesting-sounding science report on TV news, I try to remember the first five seconds of the report and expunge the rest of it from my consciousness, so I can look up what, if anything, has really been discovered, without wasting any neuron-connections on what some attractive ignoramus thinks is going on. See also, jazzed-up, dumbed-down reality shows, some of which make a real effort to get things right, and some of which don't.)
PubMed lets you search the Medline, and some other, medical research databases. You'll generally only get the abstract of each paper (and not even that, for some), and you're not tremendously likely to be able to find the whole paper for free anywhere (a situation which should change, and actually may). But a quick PubMed search will nonetheless give you a rough idea of the state of research on a subject.
If you lean on PubMed for evidence when you're having an argument with someone, the two of you are likely to end up playing what I call DuellingAbstracts, in which neither of you knows how good any of the research you're citing is, so you both just end up Bullshitting for Victory. All research is not of the same quality, and PubMed will cheerfully present you with numerous papers in support of almost anynuttyidea you like. (This is largely because Medline indexes many dodgy journals along with the respectable ones.)
Assuming you're not using the science for support, rather than illumination, you need to see how well a given piece of research was done, and how often it's been reproduced by other researchers, before you should cite it in a serious discussion. (At least few bad papers are the result of outright fraud. Unfortunately, though, a paper often has to be blatantly and quite famouslyfraudulent before it'll actually be withdrawn, though this situation is improving.)
But if you're just trying to see whether there's any research on, say, kids swallowing batteries, and you don't need more detail than you get from paper abstracts or letters written to medical journals (PubMed doesn't only index research papers), a couple of minutes on PubMed is all you need.
I was surprised to discover that there's actually quite a bit of literature on the subject of kids eating small batteries. I suppose it's the result of more and more consumer items that run from these tiny batteries. In 1980 you might have had a lithium coin or an alkaline LR44 in your calculator or wristwatch, or a silver-oxide cell if you were fancy, or a zinc-air battery in your hearing aid and maybe a mercury battery in your camera. But plenty of people didn't have one button cell in their house.
Nowadays, small remote controls, key-ring flashlights, laser pointers and umpteen other glowing tchotchkes run from miniature batteries, and it's easy to get the batteries out of most of these items. The only other thing you need to guarantee many tiny-battery-ingestion events is firm instruction from a parent that children must most emphatically not eat said batteries.
However it happens, kids are eating batteries, and the results can be quite serious.
I initially thought some danger might be posed by lithium batteries, which really do contain metallic lithium...
...which isn't as excitable as its relativesfurtherdowntheleftmost column of the Periodic Table, but which is still not something you want running around loose in your stomach. Lithium salts: Mood stabiliser. Metallic lithium: Mood ruiner.
In theory, stomach acid could eat through the casing of a battery, but in practice this doesn't seem to happen. Especially not with lithium cells, which are deliberately made very resistant to corrosion specifically to stop them from starting fires all over the place. The same goes for pretty much every other tiny battery; I don't know which of them have stainless-steel casings, but it seems they can be expected to pass through the gastrointestinal system pretty much intact, even if they do some damage on the way.
The mechanism for said damage does seem to be electrical, but not directly. Even a brand new button cell doesn't have a lot of power to deliver, and the harder you load a battery the less capacity you'll get, but swallowing a battery will give it a quite nice low-resistance pathway from one terminal to the other, and button cells all have terminals separated by only a millimetre or two. This means something close to the battery's full short-circuit current could flow through a quite small amount of tissue. The relatively large circumference of a coin cell will spread out the affected area a bit, unless the battery lodges in such a way that only part of its circumference has a good contact.
To see how much current that actually is, I threw together a battery-torturing apparatus...
...in which the twenty-amp current range of a multimeter, with about one ohm of resistance including the wires, stood in for the conductive lining of a human gut. I think one ohm is a pretty good figure to go with, here; human tissue is often not very conductive at all (put multimeter probes next to each other on your tongue and you can get a surprisingly high reading; more invasive test techniques are discouraged), but I think the internal mucous membranes, plus stomach acid or one or another salt, are both pretty conductive and pretty easy to damage.
My first victim was a tiny LR754 alkaline button cell, 7.9 by 5.4 millimetres in size, which had been sitting in my miscellaneous-battery drawer for a while but still had an open-circuit voltage above 1.5 volts. At the moment when I clicked the magnetic contacts onto the cell it produced more than 0.2 amps, but this fell to 0.1 amps after 30 seconds, 0.07 after a minute, and so on down the line until it was 0.01 amps at five minutes.
(Because I was using the super-low-resistance 20-amp range on the meter, the lowest current I could measure was 0.01 amps, and I wouldn't bet my life on the meter's accuracy either.)
Next I tried a CR2016 lithium coin cell, 20mm in diameter and 1.6mm thick. These cells are commonly used in Photon-type key-ring flashlights; red key-ring lights can run from one double-thickness CR2032, but blue, green and white LEDs need more voltage and so run from a series stack of two 2016s.
(Modern computer motherboards usually have a 20-series coin cell as their BIOS-setting backup battery. It'll probably be a CR2032, but in a pinch you can substitute a 2025 or 2016; the thinner cells should still fit the contacts. Don't stack thinner cells to fill the holder, though!)
The 2016's initial open-circuit voltage was 3.25V, but it managed less than 0.01 amps from the outset.
I thought I might have picked a defective or very old CR2016, but who cares, if the ceiling performance of shorted lithium coins isn't high enough to be a worry anyway? So I next tried to establish where that ceiling is by testing a beefy (by coin-cell standards) CR2430 (24mm wide, 3mm thick), which had also been on the shelf for rather a while and only started at 3.16 volts open-circuit, but which still should be able to easily beat any of the more common 2016s or 2032s.
The 2430's initial current was up around half an amp, but that lasted less than a second. It managed 0.16 amps after 15 seconds, 0.12 amps after a minute, 0.09 after two minutes, and kept going strongly (again, by coin-cell standards); it still managed 0.08 amps after four minutes, 0.06 after seven minutes, and was still managing 0.03A after thirty minutes, which was when I unshackled the prisoner from the wall and consigned him to eternity in the rubbish bin.
OK, so this cell managed to deliver something in the neighbourhood of a tenth of an amp for at least a few consecutive minutes. Voltage equals current times resistance, so if the current is 0.1 amps and the resistance is one ohm, there must be only 0.1V across the battery. (Voltage sag is normal in overloaded batteries.) Power equals voltage times current; 0.1 volts times 0.1 amps gives a miserable ten milliwatts of power, which even if it were concentrated in one small spot probably wouldn't, I think, directly singe even a baby's oesophagus.
My last victim was an alkaline LR44. I think this is the button battery most likely to end up inside a child, because it's both conveniently pill-shaped and very widely used. The one I chose started out at 1.57 volts open-circuit, and initially managed to deliver more than 0.3 amps into the short circuit. This, again, fell very rapidly, to 0.23 amps at 15 seconds, 0.21 at 30 seconds, 0.18 after a minute, and so on. At five minutes it was 0.12 amps, and just before ten minutes it suddenly fell from 0.07 amps to only 0.01, perhaps because of some internal failure caused by the short.
(The LR44 didn't get hot or leak, though. Modern batteries are extraordinarily good at not leaking, and only partly because we now use a lot of alkalines instead of carbon-zinc cells which corroded away their zinc casing as part of their normal operation. Un-leaking batteries are one of those things, like un-popping tyres, that now give so little trouble that people fail to even notice them any more.)
OK, let's suppose we've got a very beefy LR44 that manages to deliver 0.3 amps into one ohm for a significant amount of time. V equals IR, once again, I is 0.3, R is 1, therefore V is 0.3V, and V times I is a pathetic 0.09 watts. Again, this doesn't seem to me to be very dangerous.
One of the couple of kids who apparently managed to eat anLEDthrowie escaped without drama. This kid for some reason ate multiple magnets and batteries, but only the magnets then caused trouble.
Interestingly, there's a two-page guide to "Management of children who have swallowed button batteries", which was published in 1986 in Archives of Disease in Childhood, in PDF format here. It agrees with the newer papers that it's lodgement in the oesophagus that's the problem, but says thin lithium coin cells don't seem prone to lodge at all. And it also speculates that an increase in pH (an increase in alkalinity around the battery's anode) is what causes tissue burns, not simple electrical heating or leaking chemicals from inside the battery.
A swallowed battery is essentially electrolysing water wherever it comes to rest. That'll produce hydrogen bubbles on one terminal and oxygen bubbles on the other, but the salts that make saliva, gastric juices and tissue conductive will electrolyse too. Sodium chloride in water, or hydrochloric acid from the stomach, could give you chlorine bubbles along with the others, which would be bad news. Perhaps it's that, along with mechanical damage from the child trying to swallow the battery or cough it up, that causes fistulas and their life-threatening consequences.
Given the feeble numbers I got by short-circuiting miniature batteries, I agree that there really doesn't seem to be any electrical burning going on there. You'd just need more watts per conductive length than 1.5V and 3V miniature batteries can deliver. A twelve-volt A23 battery might do it; A23s have a stack of tiny button cells inside them, and used to be ubiquitous in small radio transmitters like car central-locking key-fobs and wireless doorbells, but are now being replaced by lithium coins. I bet a standard rectangular nine-volt battery could do it too, in the unlikely event that even a full-grown adult, let alone a child, somehow managed to ram one down their throat. There are rechargeable button cells as well, which like other rechargeables have a lot more current capacity than non-rechargeables of the same size, but they're rare enough that no child may ever actually have swallowed one.
There are variousotherindividualcasereports, ranging from the benign to the fatal, in the face of which one should remember that surely for every kid who ends up in hospital for battery-eating there must be a few who ate and later excreted a battery without any adult noticing. Or, at least, without any adult noticing until they changed that nappy.
Saving the best for last, here we have "an analysis of 8648 cases", the full text of which is available for free. The authors conclude, and also say in this slightly later paper (also online for free), that the severity of battery-swallowing injuries is getting worse, because of proliferation of 20mm-plus coin cells, which (in contradiction of the 1986 management guide) now seem to be the most dangerous. Misdiagnosis seems to be a major part of the problem, though, which shouldn't be too hard to fix since batteries show up loud and clear on an X-ray. Oh, and kids do manage to swallow AAA and AA batteries too; more than 5% of the 8648 cases involved "cylindrical cells".
These authors also say it's alkalinity - formation of hydroxide ions in tissue fluids next to one terminal of the battery - that "is now appreciated as the most important mechanism" in batteries damaging flesh.
So yes, swallowed batteries can "burn" the swallower, but chemically, not via resistive heating, which barely happens at all because these batteries can't deliver much power.
In the absence of complications like swallowed magnets, there only seems to be a danger if the battery lodges in the oesophagus. But 20mm and larger lithium coin cells are a good size to do exactly that, and if one does, there appears to be a good chance of very bad results. The authors of thosetwo meta-analyses says there's a 12.6% chance that a child younger than six swallows a 20mm-plus coin cell will "experience serious complications or death", but they base that primarily on the records of the US National Poison Data System and National Battery Ingestion Hotline (who knew?), which of course don't get to hear about battery-consumption that doesn't cause any problems and passes unnoticed.
Still, in the million-item list of things for parents of young children to freak out about, this doesn't seem like a silly one. I think parents could do worse than scan their house for remote controls, kitchen scales, toys and so on that have small and easily-removed batteries.
What the hell is going on in this "photo finish" picture?
Two sprinters are perfectly tying for third place and creating new track and field rules, but what I mean is what's going on with runner #2's Sideshow Bob foot, and runner #1's RobLiefeld foot. Runner #7 in the background looks pretty weird, too.
According to the New York Times, "the finish line cameras capture up to 3,000 frames per second". Do all of those frames look like this?!
TimT
The obvious way to implement a finish-line camera is, as the NYT say, to just run a movie camera at a huge number of frames per second.
This is not actually how most finish-line cameras work, though, primarily because of how shutters work.
A perfect camera shutter uncovers the film or sensor all at once, stays open for however long it's supposed to, then blocks the light, again all at once. You can try to implement something that works like this in electronics, or evade the problem by opening the shutter with the subject in darkness, briefly illuminating the subject with a high-speed flash, and then closing the shutter in darkness again. But that's no use for everyday photography or photo finishes, and making a physical object that works as an ideal shutter is pretty much impossible.
Instead, still and video shutters are implemented with "curtains", sliding plates, rotating discs, and various other things, none of which behave much like an ideal shutter when you need very brief exposure times, as is necessary if you need to see which runner, horse or car got over the line a hundredth of a second before the next one.
Most all-electronic cameras don't come anywhere near having an ideal shutter, either. Instead, they have a "rolling shutter" that scans across the frame, line by line or column by column, in a short but distinctly non-zero amount of time.
Rolling shutters aren't great for video, because things moving across the frame - because they and/or the camera are moving - will be in a different place as each new line or column of the frame is detected. This creates distinctive forms of distortion.
A rolling shutter will cause things that move through the frame relatively slowly to...
Things moving very quickly, like aircraft propeller blades, look far more disturbing if the exposure time is short enough that they aren't just a blur:
OK, so here we have examples of distortion created because the "hole" that lets light into the camera is changing in size, shape and location over a long enough period of time that it visibly interacts with moving objects in the scene being photographed. This is bad for everyday photography, when you don't want things you're shooting to look weird.
Looking weird is acceptable in finish-line photos, though, as long as you know what the weirdness means. The picture can be as freaky and distorted as you like, as long as you can tell who got to the finishing line first. (Or, in the case of the picture you're asking about, who got there third. Third place was, in this race, good enough to qualify the runner who got it for a place in this year's US Olympic team.)
For this reason, most finish-line cameras aren't super-high-speed movie cameras, but instead a kind of slit camera. A slit camera has a line-shaped lens, which exposes the film or electronic sensor line by line or column by column, not unlike the way a rolling shutter works. The critical difference, though, is that a slit camera can keep on going indefinitely. You can keep collecting image data, or keep spooling film past the slit, for as long as you have memory or film. The shutter never closes as long as the film or memory lasts, so it's impossible to miss any action between the frames.
Flatbed scanners are a kind of slit camera, and with modification can in fact be used as one; anything that moves around while the scan's being made, though, will look distorted. Move an object in the oppposite direction of the scanner head's motion, and that object will look shorter than it really is. Move it in the same direction, and it'll look longer. (Move it at the exact same speed as the scanner head, and the scanner will just keep seeing the same bit of the object for the whole scan, making the object look like an endless stripe.)
OK, so now imagine taking a flatbed scanner sensor and setting it up vertically, looking across a racetrack at the finish line. Start a "scan", and it'll authoritatively tell you when every body-part of every runner makes it to the finish, by simply showing that part of that person before any part of anyone else. The speed of the scan should be set to roughly match the speed of the runners, so they look generally the right shape, but any part of any runner that stays stationary relative to the scan rate - a foot on the ground, for instance - will seem long. Any part that's moving forward relative to the scan rate - a hand or foot coming forward, for instance - will seem short. Even if you mess up the scan rate so everyone looks wide or narrow, whatever part of whatever runner shows up first in the scan is the first to cross the finish line.
So let's look at this picture again. You can see that runner #4 got second place (whoever got first is off to the left somewhere), and #7 in the background is going to get fifth. Runner #2's foot got to the finish first, and because it was then planted on the ground it looks ridiculously elongated. Runner #1's left foot was moving forward as it crossed the line, and so it's shrunk.
Unfortunately for #2, the foot doesn't count. To win, your torso has to cross the line first. #2 has the first foot, #1 has the first hand and then knee, #2 has the first head... and then the foremost part of each of their torsos hits the line, so far as can be seen, at exactly the same time.
is a Nerf product; the double-barrelled gun is a 
for Victory. All research is not of the same quality, and PubMed will cheerfully present you with numerous papers in support of almost 
