» Nerdery How to Spot a Psychopath

Building a better Bond

13 December 2012 — dan

I'm a bit disappointed in the recent semi-rebooted gritty James Bond movies.

They're good films, and they're far better than the burgeoning silliness of the last of the old run of movies (...an invisible car? Really?). But a lot of that silliness was just misapplication of one of the hallmarks of the classic Bond movies: Gadgets.

The gadgets played a large role in making Bond films what they were, but they sort of stayed phase-locked in the Seventies. Bond might have been remote-controlling his BMW [shudder] with a Nokia or something, but the Third Doctor had a frickin' remote-controlled car in 1971. Bond didn't even have a gadget with a cutting laser on it until 1983.

If you're going to have Bond gadgets again beyond the low-key stuff in the rebooted films, you have to make them truly impressive. Not something, like an invisible car, that could have been dreamed up in 1970 as easily as 2002.

This is the secretest of secret agents going on the most important missions ever, after all. He should be kitted out with and backed up by with the very best superblack reverse-engineered-from-crashed-flying-saucers ultra-technology that can be created by the distinguished successors to Bletchley Park (and all the other people whose discoveries went into Tizard's briefcase).

So, say:

Bond has been shepherded into a lift by Q, and they descend. For a rather long time.

On the way down, Q explains that MI6 and, ah, some higher-numbered agencies, rather suspect that certain developments in mechanical augmentation of human strength, for military and industrial purposes, may have fallen into the wrong hands.

And that there is no real reason for these systems to be limited to only a man-sized exoskeleton, or indeed for constructors to tolerate the weakness of a normal human body within it, if one is willing to take certain rather drastic steps to ameliorate this problem.

And that Her Majesty's Secret Services have been working on their own systems to combat this threat, but have faced certain ethical obstacles.

The lift doors open to reveal a warehouse-like space, harshly illuminated by overhead fluorescents, and dotted with computer installations, machine tools, and agglomerations of technology of unclear purpose.

The giant room is dominated, however, by a looming object in its centre. A mad profusion of cables and pipes and screens and scaffolding and catwalks surrounds, and obscures, a metallic shape about the size of a terrace house.

Q turns to Bond, and says, "For this project to succeed, 007, we needed someone with great familiarity with our most advanced systems; otherwise the training process would be impossibly difficult. There were several candidates, but owing to the... the nature of the project, none were acceptable."

"Pardon?"

"Well, not to put too fine a point on it, we needed their brain, and about six inches of spinal cord, which is rather-"

"You needed...?!"

"Which is, is of course, more than we were prepared to ask any servant of the Queen to volunteer. But then-"

"What the hell are you-"

"But then, the previous Q had, well, he had a car accident. And, fortuitously..."

He waves vaguely at the huge shape in the middle of that mass of pipes and cables.

With a subsonic hum, the shape changes.

It stands up.

Many of the cables and pipes drop away, as the giant machine takes a step forward. The concrete floor trembles noticeably as its foot comes down.

The machine stops.

It speaks.

"NOW PAY ATTENTION, DOUBLE-O-SEVEN."

Posted in Movies, Nerdery. 5 Comments »

12 AAs in the magazine, one in the chamber

4 December 2012 — dan

A reader writes:

I've read that the problem with ray guns is that as an energy delivery system, pieces of high-speed lead propelled by a chemical reaction work much better than photons propelled by battery power.

If you could dump all of the energy out of, say, a AA battery really fast, though, could you get bullet levels of energy out of each battery?

S.C.

Yes, you could.

Let's presume you're using nickel-metal-hydride AA batteries, which are somewhere between average-rifle-cartridge and average-pistol-cartridge in size. You can get a lot more current out of a NiMH or NiCd rechargeable than an alkaline or carbon-zinc battery, but, as you say, you still can't discharge them nearly fast enough for them to be useful replacements for firearm cartridges.

Even if you don't care whether the battery survives the experience, the biggest bang you can get out of a battery is the feeble "explosion" of a laptop battery. That may give you nasty burns if it happens literally on your lap, and shorted batteries have been responsible for the destruction of quite a few cargo planes, but batteries are no more than firecrackers compared with proper explosive devices.

Never mind that for now, though, let's just look at the energy content.

The most generally useful kind of NiMH cell is the "low self-discharge" type, which unlike the older kind of NiMH, do not go flat in a matter of weeks whether you use them or not. (Low-self-discharge cells are often sold as "pre-charged", or "ready to use".) LSD cells have lower capacity, though, so let's say we're using non-LSD cells with the absolute bleeding edge maximum capacity today available, which is about three amp-hours (3000 milliamp-hours).

1.2 volts (the standard NiMH or NiCd terminal voltage) times three amp-hours gives 3.6 watt-hours. A joule is a watt-second, there are 3600 seconds in an hour, so 3.6 watt-hours is 12,960 joules.

Firearm muzzle energy is often measured in foot-pounds, not joules, but I'll keep it all in SI units here. You also couldn't get the entire capacity of any electrical energy source into your beam or projectile, because no laser or mass-driver is 100% efficient, but I'll handwave that as well.

12,960 joules is a pretty darn respectable chunk of energy, way more than any handgun cartridge can manage. 9mm rounds top out around 500 joules of muzzle energy, .44 Magnum is a couple of thousand joules at most, and even the ludicrous .500 S&W Magnum is only around 4000 joules.

Rifle cartridges that qualify as "high-powered" seldom exceed 4000 joules. You have to start looking at exotic specialised sniper and large-game rounds, or heavy-machine-gun ammunition, before you get above ten thousand joules. The .50 BMG round easily beats 12,000 joules, and the more ludicrous kinds of elephant-gun double rifle roughly equal the battery's energy...

...as you'd bleeding well want them to, for this kind of recoil punishment.

But all of this is, again, just fantasy, because you can't dump the energy out of any kind of battery anywhere near fast enough to make it useful in a gun.

You can, however, dump the energy out of a capacitor in a very short period of time.

The highest-capacity "supercapacitors" can't be discharged in a tiny fraction of a second without damaging them; they're usable in a flashlight or for regenerative braking, but not for one lightning-strike discharge, as in a firearm.

Normal caps certainly can be discharged fast, though.

This cap bank could be used to power some kind of kinetic or ray-gun weapon - but it takes all of those huge beer-can capacitors to hold a mere 11.3 kilojoules, roughly the same as our one AA NiMH cell. The one killing the watermelon above is only 9270 joules, and its caps are huge.

I have one beer-can electrolytic cap of my own; it featured in this...

...extremely practical assemblage.

If it still had its full original capacity - which it doesn't - then fully charged to its 850-microfarad, 450-volt redline, it would hold 86 joules of energy.

You can get firearm cartridges that are that feeble, or even weaker, and I certainly wouldn't want to be shot with them. But I'd take them over a humble .38 Special or .22 Long Rifle any day.

The miserable performance-per-size of electricity-storing devices is why electromagnetic railguns are of moderate interest to navies...

...but not to armies.

It's also why the only really workable technology for a military laser gun (as opposed to lasers only used to temporarily or permanently blind the enemy) is the chemical laser.

Chemical lasers can be usefully powerful without requiring capacitor banks the size of a house. They are generally very unpleasant to be near, though, because they either run on, or produce, horrible toxic compounds.

Which is why plain old deflagrating gunpowder, propelling a piece of metal down a tube, remains the standard way to do unto others at a distance.

Oh - and if you've never watched Kaboom!, you really ought to.

UPDATE: On the subject of ludicrous electrical things, there's this piece I did on what a AAA battery composed of nothing but electrons would be like.

(It would not be kind to nearby spacetime.)

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

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

Posted in Electricity, Nerdery, Psycho Science, Science. 10 Comments »

"Bug-zapper engaged."

22 November 2012 — dan

All the serious MechWarrior Online players use voice chat to coordinate their team. The game has some kind of voice-chat thing built in, but I don't think anybody uses it, because the obvious feature of just making an ad-hoc chat group out of everybody on the team that has a microphone does not exist.

There is a much better reason to use voice chat, though.

It allows you to have a Bitching Betty voice actor actually playing on your team.

(She's in the red Gaussapult. She's also not the one who'll actually be doing the onboard-computer voice, when it returns to the game; they've apparently retained the services of Carole Ruggier again.)

Posted in Games, MechWarrior Online, Nerdery. 3 Comments »

On V-2s, Qassams, and conditional probability

20 November 2012 — dan

A reader writes:

Re "If it looks random, it probably isn't"; can I presume that I can apply the same logic instead of lightning to missiles ?

Meaning if a missile falls in a location is it highly probably that another will fall in the same area?

R.

From Israel.

Right at the top, I'm just going to say that I'm not going to say anything about the politics of this situation which has been particularly in the news, yet again, in the last few days, and I'd appreciate it if commenters didn't either. I sure do have opinions on this subject, but there are a million places people can have arguments about the Heroic Downtrodden Palestinians versus the Stoic Peace-Loving Israelis, and this blog post is not the time nor the place.

(Readers who feel an uncontrollable need to argue about something are encouraged to do so on that post about a free book that some guy argued against without even looking at the free book, that post about the existence or otherwise of "copper bullion" where a lady turned up to hotly argue that buying copper by the ounce is a great idea, and the few posts that sort of ended up being about Jock Doubleday and the floridly preposterous conditions of his "vaccine challenge". Bonus points for anybody who manages to persuade me to their religion, or that climate change isn't happening, or that every man secretly craves sex with other men.)

Speaking of time and place, though, both things are important here, because impacts of artillery over time have a distribution both in space and in time. This is a problem which has been addressed before, most famously in analyses of where the thousands of V-1 and V-2 missiles landed in and around London in World War II.

(That, by the way, is one of the approximately 300 themes of Thomas Pynchon's Gravity's Rainbow, which I read once, and finished, purely because I am susceptible to the sunk-costs fallacy. Forget Israelis and Palestinians - if you want to see true hatred, ask me what I think of Gravity's Fucking Rainbow. How can such dazzling ability to paint a whole scene with ten words be used to create such an indigestible housebrick of a book?!)

The British analysts in WWII wanted to know how good the guidance systems of the V-2, in particular, were. Since it turned out that V-2 hits conformed quite well to a random Poisson distribution, the analysts reached the correct conclusion that the V-2 did not have a guidance system capable of targeting particular areas of the city.

Even the V-1s did have some kind of guidance system, though. There's a popular belief that V-1s "flew until their fuel ran out", but they actually had an autopilot that counted the revolutions of a little propeller on the nose of the missile, and put the bomb in a dive after a predetermined flight distance. That dive happened to cut off the fuel flow and stop the engine in early V-1s, creating the out-of-fuel legend; this bug was fixed in later V-1s, most of which therefore managed to do their final dive under power, as originally designed.

Aaaaanyway, if you abstract it all out and presume that any arbitrary square metre of Sderot is as likely to be hit by a rocket from the Gaza Strip as any other over a given hour, then the lightning-strike conditional-probability situation applies. Whichever square metre you're standing in is, by these assumptions, as likely to be hit over the next hour as any other, but in order for a missile to next hit your particular square metre two hours from now, there must by definition not be a hit in the next hour. So, as in the lightning-strike example, you multiply the probability of no-hit next hour by the probability of a hit the hour after that, and get a slightly lower number. The probability of a hit in any given spot in any given hour is the same, but the probability of the next hit being separated from now by one, or ten, or a million, hours gets lower and lower as time wears on.

This is of no use whatsoever in determining what location's going to be hit next, though; we assumed right at the start of our abstraction that the missiles were falling randomly. It just explains why clusters of hits, close in time and/or space, can and will occur - and encourage the statistically untutored to explain them in terms of aim and guidance systems - even if the actual distribution of events is random.

In the real world, of course, the distribution of Palestinian missile hits on Israel is only partially random. The basic garage-built missiles have no guidance system at all and variable performance characteristics, which predisposes them to land in a Poisson distribution just like the V-2s in WWII. But there are many launch sites and several other kinds of missile...

image source: Meir Amit Intelligence and Terrorism Information Center)

...making the overall situation extremely complex.

Many Palestinian missiles are just shot in the right general direction (in the opinion of the people launching them, of course). In videos of the Iron Dome missile-defence system in operation...

...you'll occasionally see the system not bothering to shoot an interceptor missile at some of the incoming fire, because the system calculates that that rocket isn't going to hit a populated area. (See also, mortar attacks by insurgents/terrorists/freedom-fighters, strike out whichever does not in your opinion apply, on military bases and police stations and various other targets in Northern Ireland, Afghanistan, Iraq, and a dismayingly long list of other places.)

But the more sophisticated actual military rockets definitely can be aimed, at least to some extent, so the distribution of their hits will be skewed toward populated areas, military targets, or whatever else the people launching them are trying to hit. You could probably protect yourself from those rockets by a considerable amount by going and living in a tent in the middle of the desert.

As regards avoiding getting blown up in the Israeli towns within rocket range of the Gaza Strip, though, I'm afraid conditional probability has nothing to offer you. All it tells you is that it's improbable that some particular location will not be hit for an extended period of time, which you already, unfortunately, knew.

Posted in Nerdery, Strange Tales. 17 Comments »

MechWarrioring, Online

15 November 2012 — dan

I've been spending entirely too much time playing MechWarrior Online.

If you've got a Windows PC with moderate graphics power, or something that can be tricked into acting like one, try it. It's free. And if you do not want to fight people from distant nations in a giant walking tank, I am not at all sure that I want to be friends with you.

(There will be a certain amount of BattleTech-y jargon in this post. I make no apologies, since all right-thinking people pored over Technical Readout: 3025 at the bus stop in 1987 as I did, memorising even the stupidest-looking 'Mechs, and thinking long and hard on the subject of internal-combustion Demolisher tanks only costing about 20% more than 25-ton scout 'Mechs. You are allowed to not have also played hundreds of hours of the unlicensed multiplayer-only tabletop-BattleTech knockoff Mechforce on the Amiga, but that's as far as I'm willing to go. Oh, and in case you care, the modern equivalent to Mechforce is MegaMek.)

MechWarrior Online is currently in open beta. It is not bugless, and right now the only game mode is eight-a-side team deathmatch on a small handful of maps, with a capture-the-base mechanic to avoid the "Where's Wally" problem in which the single survivor of one team goes and hides until his opponents quit in disgust.

But it doesn't crash very often, and stuff you earn in the beta will carry over into the full release, so it's well worth trying.

Because, again, it's free.

"Wait a minute," I hear you say, "this is actually an Allegedly Free Game, right? They want you to send them money if you want a 'Mech that can compete, don't they?"

Well, yes, Piranha Games would very much like you to whip out your credit card or PayPal account and pay for "MechWarrior Credits" ("MC"), which can be purchased in five tiers from $US6.95 for 1250 MCs (180 MCs per dollar) to $US99.95 for 25,000 MCs (250 credits per dollar). But you really can play, and play competitively, without spending a penny.

You can certainly play competitively without buying the first only-available-for-real-money "hero 'Mech", the "Yen-Lo-Wang" variant of the Centurion. That costs 3750 MCs, meaning you'd have to buy at least the $US29.95 6500-MC package (217 MCs per dollar), and its main selling point is that it multiplies all "normal" money, "C-Bills" you make in the game by 1.3. But that's about the only nice thing you can say about it.

I will digress about the "Wang", as everyone calls both it and anyone driving one, for a moment, because that 'Mech exemplifies an important piece of MechWarrior Online's design. (This may have debuted in some other MechWarrior game, by the way; I haven't played the last couple of them. I haven't played Crysis-based MechWarrior, Living Legends either.)

The Wang is not a very good 'Mech at all, because the only weapon "hardpoints" it has are two ballistic ones on the right arm, and two energy hardpoints in the centre torso. You only have two "slots" left over in any 'Mech's the centre torso after the gyro and engine, so you can't mount any big lasers or PPCs or whatever there. The best you can do is two Medium Lasers. Even a Medium Pulse Laser will take up both slots and leave you no room to install a second energy weapon.

Old-style tabletop BattleTech did not work like this. Per the original rules, you could strip any 'Mech down to the frame and rebuild it however you liked, provided it didn't end up overweight.

(Weight limits are one of the distinctive features of BattleTech. A "75-ton" 'Mech can be kitted out with less than 75 tons of gear if you're feeling perverse, but not so much as an ounce more. Since any 'Mech with hands can, per the original rules, also yank a two-ton tree out of the ground and whack another 'Mech with it, and since 'Mechs can operate on a variety of planets with different gravity strength, this makes no sense at all. But it's always been in the rules, and MechWarrior Online follows them.)

So by the old rules, you could take the LRMs off an Archer and put on lots of heat-sinks and lasers, or you could somehow cram an AC/20 into any scout 'Mech by downsizing the engine and stripping off armour and arm actuators, or you could stick jump jets on anything. You name it. The "fluff" may say that this 'Mech is prone to knee-joint problems and that one has especially fast torso twisting, but there was no actual difference in the game itself.

In MechWarrior Online, the hardpoints are fixed. If you buy the Catapult variant that has six missile hardpoints and nothing else, you will never be able to put a laser on it. And 'Mechs really do have different cockpit visibility, arm and torso movement ranges, and so on.

Which is why the Wang sucks. It comes with an AC/20, the heaviest-hitting gun in the game, on its right arm, but opponents with a clue will try to shoot that arm off any Wang they see. And if you're like me and playing from Australia, your 250-millisecond-ish ping time makes ballistic weapons very hard to use. Lasers and lock-on missiles (both long-range and Streak short range) work well enough, but even PPCs are hard to aim when the darn thing always goes off a quarter second after you press the button, and heavy autocannon are a huge pain.

The hardpoint system means Wang pilots are stuck with these problems, though. They can put two lighter autocannon in the right arm if they like, or even a couple of machine guns (which are almost harmless unless shooting a de-armoured location, in which case they become critical-hit monsters). But, to add insult to injury, the Wang's arms don't even have very wide movement arcs. So you almost get the restricted tracking of a torso-mount weapon, with the vulnerability of an arm-mount one.

OK, back to the "pay to win" problem, and why MechWarrior Online does not suffer from it, much.

You can buy some MCs with real money right at the outset, and buy your own 'Mech.

This isn't necessarily even very expensive; the cheapest 'Mech in the game so far is a Commando variant that goes for only 680 MC, giving you plenty of change from even the $US6.95 MC package.

(The most expensive 'Mech is an Atlas variant that costs 13.7 million C-bills, or 5480 MC. You'd need to buy at least the $US29.95 6500-MC package to buy it right off the bat. Oh, and you can't, at the moment at least, buy partially with C-Bills and partially with MC.)

Don't buy right away, though; maybe you won't even like the game! Instead, start out playing the "trial" 'Mechs, which are actually pretty good at the moment (they switch the trial 'Mechs around from time to time. The last batch weren't so great).

Do not jump into the trial Atlas and lumber around in befuddlement at your numerous weapons systems and limited speed and torso aiming envelope. Grab the trial Commando or Catapult, instead. The Commando is nippy and heavily armed for its size (it's exactly tall enough to headbutt an Atlas in the crotch); the Catapult has a simple and useful weapon loadout, and jump-jets, which may or may not reduce the amount of time a newbie spends grinding his face on the scenery.

Newbies do that because MechWarrior Online, like all other "proper" MechWarrior games, has separate controls for your legs and your torso and arms. Using the default keyboard and mouse controls (which work well), W and S change throttle setting, and A and D turn your legs left and right. The mouse moves your arms and torso. Arms - and any weapons on them - get to where you've moved quickly, then the torso - and any weapons on it - catches up.

Since many 'Mechs have a quite wide torso traverse - many can aim directly behind them with their arms - it is easy to lose track of what you're doing and flail around randomly while nudging the scenery and being torn to shreds by heartless opponents. Thus far the game also lacks any sort of interactive tutorial, too, so you have to learn to drive under fire.

(On the subject of shooting behind you, by the way, MechWarrior Online does not allow rear-facing weapons, because they couldn't figure out a way to make them useful and fun at the same time. There are also no 'Mech collisions in the game at the moment; they took out the collision code after seeing how often a 'Mech would be knocked down in one place then stand up somewhere very different. Collisions, and Death from Above, are promised to be reinstated once they've sorted this out.)

Anyway, pick a trial 'Mech, and play. This will earn you the in-game "C-Bills" money, but not experience points. But you don't have to pay to repair or re-arm a trial 'Mech either, and you get money even when you lose a game.

Which you will, a lot, because the match-maker at the moment doesn't seem to see any difference between a new player in a trial heavy 'Mech and a hugely experienced player in a fully tricked-out heavy 'Mech. In about 20 to 30 games, you'll be able to afford to buy your own light 'Mech.

Which is what I recommend you do. A nice fast light 'Mech is the closest to a conventional first-person shooter you can get in this game, zooming around behind enemies spotting targets for your long-range shooters and generally making a nuisance of yourself is a lot of fun, and a light 'Mech with no fancy upgrades doesn't cost much to repair even if you're utterly blown to bits.

Ferro-fibrous armour, endo-steel interior structure, Artemis missile fire control and the extremely expensive XL engines are all available as upgrades; if you still frequently do not survive a battle, it's best not to bother with any of them. (Especially the XL engine, the cheapest of which costs more than the biggest plain engine. XL engines have extra critical-hit locations in right and left torso; any hit to any of those locations detonates the engine and your 'Mech, making it impossible to turn a profit on that match.)

When you play with an "owned", non-Trial 'Mech, you earn "Mech XP" experience points that can be spent on minor upgrades - 7.5% better heat dissipation, 10% faster turning speed, that sort of thing - specific to that 'Mech variant:

You can get the first eight upgrades by just saving up enough XP; you can only get the "Elite" and higher upgrades - and also double all of the basic-upgrade bonuses, which is rather nice - if you've bought all eight upgrades for three variants of that 'Mech model.

This is made easier by "General XP", which can be spent on upgrades for any 'Mech. You can convert Mech XP into General XP one-for-one, but it costs 40 MC per thousand XP converted.

You don't have to convert any points, though. You can just play with each 'Mech variant until you've earned enough points with it to upgrade it fully.

The Elite upgrades aren't that amazing, either; the double bonus to the Basic upgrades is much more exciting, if you ask me. Elite offers you 33% faster shutting down and starting up, 15% better weapon "convergence" (accuracy of aiming at the crosshair), 5% faster weapon firing and a 10% higher top speed, but that'll cost you 21,500 experience points, versus 14,250 for all eight Basic upgrades.

And, importantly, there is no way to just buy these upgrades; you can buy Mech Credits and use them to shift Mech XP from one 'Mech to General XP you can spend on tweaking another, but you can't buy experience points.

(You can also only buy pilot upgrades with GXP, but none of those are must-haves either.)

As you may have gathered, I could keep rabbiting on about this game indefinitely. In future posts, I may.

Just go and play it. It's fun.

(And do feel free to send me some money so, despite all the above, I can buy some more MCs with which to shift my XP points around. And buy more 'Mech bays, slots for owned 'Mechs so you don't have to sell one before you can buy another. Papa needs a new BattleMech carport, people!)

Posted in Games, MechWarrior Online, MiniReviews, Nerdery. 20 Comments »

More magnets

9 November 2012 — dan

The mysterious Professor X, from that post the other day about scaling up little toy sculpture magnet things to evade bans on such toys, has contacted me again:

Now that I'm not headed to bed and can really read the post, thanks again for such thorough and useful info. The comment to your post was useful, too.

I assume that if the sphere size stays the same and the flux factor goes down, they're just not going to be as effective for sculpting because they won't hold as well, and they won't have the same satisfying snap, etc. The lack of a workable alternative is just as good for me as a teaching point as a workable alternative would be; I'll have fun with this. I appreciate your assistance to total stranger.

I find it funny, after reading your post, that the CPSC in its Notice of Proposed Rulemaking says, "Thus, it might be possible for manufacturers to make magnet sets that contain strong magnets so long as the magnets are sufficiently large, although the large size could reduce their utility."

Well, that's an understatement, apparently.

Professor X

To get a, literal, feel for how these things behave, I do strongly recommend you hit eBay and get some cheap magnets there, both the little strong silver ones and the black shiny "rattlesnake egg" type (which can be had as spheres as well as elongated ovals).

The eBay seller I got some of my element samples from, "The Mists of Avalon" (here on eBay Australia, here on eBay UK) has some interesting magnets too, including irregular "tumblie" versions of the rattlesnake-egg type.

Plus, of course, these things really are some of the greatest fiddle-toys ever created. Just don't put them in the same pocket as your credit cards!

I used to also have to warn people to keep strong magnets away from CRT monitors and TVs, but that's way less of a problem these days, of course. To demonstrate rare-earth magnets' their ability to wipe other magnetised things, get a standard flexible rubber fridge magnet of the sort given away as promotional items, scrub it all over with a smallish rare-earth magnet, and behold that it now can't stick to a fridge at all.

This is because those rubbery magnets are set up with a "one sided" array of alternating parallel rows of magnetisation - that's why only one side of them sticks to the fridge, and also why they stick to each other in such an odd, "lumpy" way.

You can also use magnetic field viewing film (a small piece of which can be yours for less than $10 delivered) to see this oddness directly.

When a strong enough external field re-aligns these parallel poles so they all go one way, the essentially feeble magnetic material can no longer hold up own weight.

There's a lot to be said for ferrofluid, too.

The cheapest ferrofluid on eBay is in tiny squeeze sachets, for topping up the coolant in tweeters. But you can get thirty grams for less than $US25 delivered; that's enough to have some fun with.

There are also several dealers selling sealed vials with ferrofluid and possibly also some immiscible liquid inside, to keep the ferrofluid clean and, perhaps more importantly, prevent other objects, people and pets from being stained by it. Regrettably, you can only get some of a ferrofluid stain out of your clothes with a magnet.

Also, if physics demonstrations at all interest you, those little magnets can be great for those, too!

Posted in Nerdery, Science, Toys. Leave a Comment »

From crowbar to glowbar

4 November 2012 — dan

A reader alerted me to this video (which has embedding turned off - click through to YouTube to watch it). His subject line was "Progress in the field of vaporizing crowbars".

(He found it via Hack A Day, where I would eventually have seen it myself, but I've got 234 unread articles in the Hack A Day feed, so it could be a while before I get to it.)

In this video, there is a man.

The man has made a transformer.

The transformer's secondary winding looks like a suspension component from a large four-wheel-drive vehicle.

You could moor a ship with this stuff.

There is, I must warn you, a certain amount of profanity in the video.

I think it is entirely justified, given that in this gentleman's estimation thirty thousand amps does not qualify as "serious amps".

"I've got a screwdriver what goes round corners, now!"

I note that the transformer also seems to be running from a variac that makes my 500VA one look very, very inadequate.

The immense current capacity of the transformer causes anything shorting the outputs via small contact points to instantly lose those contact points in a most impressive explosion of sparks. But since the transformer in its present configuration tops out at only about four volts open-circuit, the hazard it (as opposed to its mains-voltage power supply) poses to its operator is only one of burning yourself on hot conductive objects, not electrocution.

"Don't touch anything electrified" is one of those general rules of thumb like "don't put metal in a microwave oven" that are easy to explain to people, but which do not actually apply in every situation.

I still wouldn't want to walk around this guy's house blindfolded, though.

Posted in Electricity, Hacks, Nerdery. 9 Comments »

Duelling flashlights

21 September 2012 — dan

As a postscript to my post about fluorescence, here are red, green and blue Ultrafire 501Bs attempting to create white:

They actually do a decent job of it if you just hold them together in a bunch, or hold one in each hand and one in your mouth so you can aim the light all into one pool, like the old EternaLight Rave'n:

Any one of the coloured Ultrafires makes a decent flashlight all by itself. Red if you're feeling sexy, ominous or both, green for maximum visibility, blue for a particularly unearthly look, including that unexpected fluorescence. I really do highly recommend them. Why use a boring white flashlight when you can have something fun instead?

(They also partner well with my...

...elderly "bullseye" flashlight. It's excellent for seeing where you're about to step at night with dark-adapted eyes; the much narrower and far brighter beams of the Ultrafire lights are great for seeing things further away.)

Coloured flashlights are completely unsuitable for some tasks, like reading maps; shine a red light on a multi-coloured map and any markings with no red in 'em will look black. For everyday flashlight tasks, though, why not do it the sci-fi B-movie way?

You can get these lights on eBay for $US9.99 delivered for just a lamp to put into any Ultrafire-or-other-branded SureFire clone, or for less than $US15 delivered for a whole flashlight with coloured lamp. As I said in the fluorescence post, a red, a green and a blue Ultrafire 501B, plus three 18650 lithium cells to power them and a charger, will only cost you about $US50 delivered, for the lot. Pretend you're getting them to educate your kids about additive and subtractive colour, if it helps.

Now I'm going to have to get an infrared and an ultraviolet one, too. Infrared Ultrafires sell for $US20 to $US30 delivered, and their beam will be clearly visible to any digital camera that doesn't have a good IR-cut filter in front of the sensor.

Actually, even cameras that do have such a sensor can see near-IR...

...but only with a long exposure that'll blur moving subjects:

You could cut the exposure time down quite a lot by lighting a small target with a high-powered IR LED flashlight like this, or using a dedicated IR flash (expensive) or a filter on a conventional flash. But you probably still won't be able to use a properly fast motion-stopping shutter speed unless you've got a camera with no IR filter, or make one yourself. (Or pay someone else to make one for you, complete with tweaking the autofocus so it works properly in the new waveband, but that's cheating.)

Ultraviolet Ultrafire flashlights cost little more than the visible-light ones, but the cheap UV models are barely UV at all. They emit a purple light with a wavelength up around 400 nanometres; this excites fluorescence in various objects quite well...

(Image source: Flickr user davecobb)

...but is clearly visible to the naked eye.

"True" UV LEDs exist too; they have an output wavelength of 370 nanometres or less. (I reviewed a Photon key-ring 370nm light years ago, here.) 370nm light is still visible to the naked eye, but is now a faint white (it's not a great idea to stare down the barrel of a bright near-UV LED flashlight, by the way). As the wavelength gets shorter, the visibility of the light from the LED itself, as opposed to whatever fluorescence it excites in other objects, fades away.

Searching for Ultrafire lights with "nm" in the listing currently turns up an alleged 365nm flashlight for $US19.96 delivered.

Buy one, before someone in government discovers that staring into the beam for minutes on end can damage your eyes, and bans them!

Posted in Nerdery, Toys. 7 Comments »

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