Clear acrylic and magnets doing odd things do indeed instantly start some red flags waving among those of us who're accustomed to independent thinkers like Steorn who, as you say, claim to break the laws o' physics but never quite manage to actually do it. But Correlated Magnetics are not in the physical-law-breaking business. You can make a less elegant contraption that does the same thing all of their products do, at home.
Take the "Hoverfield" thing, for instance. To make your own ugly version, all you need is a couple of large relatively weak magnets, plain ferrites, for instance, and two or more small strong rare-earthmagnets.
Now glue the rare-earth magnets onto the faces of the ferrite magnets so that when the ferrites are facing and attracting each other, the rare-earth magnets are facing and repelling. The large ferrite magnets have a big, weak field; the small rare-earth magnets have a little, strong one. So the ferrites attract until they're close enough that the stronger but smaller repulsive force of the rare-earth magnets equals the attractive force of the ferrites, and provided your contraption prevents the magnets from slipping sideways and ruining the demonstration, it'll oscillate to stability with the magnets close, but not touching.
Correlated Magnetics can make a magnet array that does this, but looks like an ordinary single magnet. They produce various other one-piece arrays too. "Coded" magnets that have matching pseudo-random pole patterns so they lock together very strongly but only in one orientation, for instance, and other patterns that reduce the size of the field but strengthen its holding force. (This is also how rubber fridge magnets work - rub a couple of them over each other and you can easily feel the "ridges" of polarisation that make the weak magnetic material able to actually stick to a fridge.) Correlated Magnetics have a few other such creations.
Calling these magnets "programmable" is I think a bit of marketing puffery, since they've got nothing to do with true programmable matter. If these things are really "programmable", then so are those big Edmund-Scientific-type junk-fishing magnets that you can "turn off" with a handle (which moves the magnet inside away from the external field-concentrating pole piece that the junk sticks to).
There's no perpetual motion claims here, though. leave your pitchforks stuck in the haystack, and your torches unlit.
If you're up for it, I'd really love an article on why the size of that meteorite varies from 10 tons to 10,000, why the rarity of it is 1 in 5 years to 1 in 100, and why the explosion is everything from 1 to 500 Hiroshimas (I hadn't realized that was a new standard measure until today).
Right after everybody started goggling at YouTube videos of lights in the sky over Chelyabinsk, and blessing once again the everlasting source of comedy and horror that is the Russian dash-camphenomenon, a lot of reporters were probably hitting the telephones. (Or just Twitter, now that having the first story is so much more important than having the first correct story.)
Anyway, early on there was an estimate allegedly from the Russian Academy of Sciences that said the meteoroid was only about ten tons. I don't know who at the Academy first said that to a journalist, since there doesn't seem to be an official press release or anything, but that mass estimate seems tied to them.
Since this estimate came before anybody had pulled together enough reports and readings to know for sure the size, velocity and explosion altitude of the rock, it's not surprising they were way off. I presume they just estimated a relatively low airburst of a relatively small rock, enough to do this sort of damage...
...without requiring the meteoroid to be a one-per-century size.
Around the same time, the European Space Agencysimilarly estimated the rock to be relatively small, with the caveat that they didn't yet have "precise information on the size, mass and composition of the object".
But then NASA estimated the rock was much bigger and heavier and blew up much higher. Since then, better readings have caused NASA to estimate it was a little larger again, putting it in the one-per-century category. I think this pretty conclusively overrules the early, low estimates.
This may also make it fortunate that this meteoroid came in at a grazing angle, and exploded so high up. I'm no expert on meteorite dynamics, but if the Chelyabinsk rock had managed to get down to ten kilometres or lower before it exploded, it would have Tunguska-ed the city, not just outshone the sun and then broken lots of windows.
This may have been impossible, especially if this meteoroid was one of the common stony types. Nickel-iron meteoroids are much rarer than stony ones, but also much more likely to make it to the surface without "exploding". The explosion effect when a meteoroid disintegrates in the atmosphere comes from the much greater surface area per mass of the fragments; they decelerate faster and heat up more, creating the kaboom. Whatever bits survive this process are generally small enough that they're only travelling at terminal velocity when they hit the ground.
I think gigantic dinosaur-killermeteorites can't help but make it to the surface largely intact, and ruin everybody's whole week. At the other end of the size chart are the tiny micrometeorites that drizzle down constantly, which anybody can harvest from the roof of a building.
I agree that using the Hiroshima bomb as an explosion-size yardstick is a bit silly, since it's not as if many people now living have a personal, visceral understanding of what that means. You might as well say something like "the meteoroid weighed more than 9000 tonnes, as much as fifteen thousand adult bluefin tuna".
The two biggest explosions there, which happened almost simultaneously, added up to only about 2.7 kilotons of TNT. The Chelyabinsk meteoroid explosion was, according to NASA's corrected estimate, close to 500 kilotons.
UPDATE: Phil Plait, the moderately famous actual astronomer who you should obviously have listened to about this stuff before you wasted minutes of your life on the above, has a couple of articles about the Russian meteor here and here.
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?
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 rifleroughlyequal 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.
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.
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 deflagratinggunpowder, 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.
How did Felix Baumgartner break the sound barrier by falling? I've always thought there was some kind of maximum velocity because of drag, even for someone trying to minimize it, in the vicinity of 200km/h.... Is this simply because the atmosphere is sparser up there? (Which would explain the bother about getting 42km off the ground when the max speed is reached after 40 sec.)
In the same vein, to what extent could an astronaut bail out of the ISS, Kursk-style?
The usually-quoted human terminal velocity - as you say, around 200 km/h for a skydiver in "star" pose, well over 300 km/h for a skydiver in a head-down pose with limbs tucked in - applies only to normal skydives, which don't start at such a high altitude that the divers even need supplementary oxygen, much less an actual pressure suit.
15,000 feet (about 4.6 kilometres) is a high jump altitude for a recreational skydiver. At that altitude atmospheric pressure is still above 50% of what it is at sea level. Unacclimated people won't be able to get much done at that pressure and will probably start feeling pretty miserable if they stay there for a long time, but if you're just sitting in a perfectly good aeroplane out of which you shortly intend to jump, it's not a huge problem.
5,000 feet (about 1.5 kilometres) is a much commoner skydiving altitude. At that altitude you've still got 80% of sea-level air pressure. The excitement of the impending jump will have much more effect on you, at that pressure, than the thinning of the air.
(Katoomba, where I live, is about a kilometre above sea level, which is high for Australia; this country's pretty geologically inactive, so for a very long time erosion's been wearing the mountains down and nothing's been pushing them up. A thousand metres is still enough to drop atmospheric pressure to about 87% of that at sea level, though. I therefore get a very mild sort of altitude training any time I go to the shops, or take Alice the Wonder Dog, who needs more exercise than our friends who own her can quite manage to supply, for a walk.)
You need a pressure suit above the "Armstrong limit" (named for Harry George Armstrong, not Neil), which is the pressure where water boils at human body temperature. There is no way to survive for more than a minute or three above the Armstrong Limit, even if you've got pure oxygen to breathe.
The Armstrong limit is around 19.2 kilometres (about 63,000 feet above sea level, 2.2 Mount Everests), depending on the weather. Felix Baumgartner's Red Bull Stratos dive started from a little more than 39 kilometres above sea level.
At that altitude, the air pressure is about four thousandths of an atmosphere. That's 3.9 hectopascals, or 0.056 pounds per square inch. A home experimenter would be pretty pleased to own a mechanical vacuum pump able to pump down that low.
When the air is this tenuous, there is obviously not much air resistance to slow down a falling body. The terminal velocity of a skydiver (or a feather pillow, for that matter) will thus be far higher than it is for a human falling at normal skydiving altitudes.
The speed of sound in a gas, including air, depends on the gas's density, pressure and temperature. For the earth's atmosphere, this results in a rather odd variation of sound-speed with altitude, conveniently displayed in this graph I just ripped off from Wikipedia:
You can see that temperature is the major factor - the shape of the blue speed-of-sound line closely matches that of the red temperature line. This is because density and pressure decrease together with altitude, and cancel each other out.
You can also see, once again, that at 39 kilometres up where Baumgartner's dive started, there ain't much air left at all. The higher you go, the more perverse it therefore becomes to be concerned about the speed of sound at all, from the point of view of a skydiver.
Breaking the sound barrier at "normal" altitudes is a big deal. Even aircraft that only want to come vaguely close to the speed of sound, like jumbo jets, need special design features to prevent alarming things happening when they get above about Mach 0.75.
("Alarming things" include stuff like "the controls not working any more". Quite a lot of World War II airmen lost their lives when a power-dive pushed them fast enough that air was passing over certain parts of their aircraft at transonic speed. Some aircraft designs also helpfully went into a dive all by themselves if flown too fast.)
When the air's so thin that a paper plane would drop like a rock, though, all the same transonic shockwave stuff may be happening, but the forces involved are too feeble to worry about.
So yes, Baumgartner broke the speed of sound, but it wasn't that big a deal, because he was starting from so high up that he would probably have fallen at least a couple of hundred metres per second even if he'd opened his parachute the moment he jumped.
OK, on to bailing out from the International Space Station. This is problematic.
The ISS is in orbit, so if you jump out of it, you'll just be in orbit too. Whatever relative velocity you can give yourself with your legs will not be enough to make a significant difference. In order to actually fall into the atmosphere, you'll have to kill some of your orbital velocity with some sort of thruster - this is how spacecraft "de-orbit".
Let's presume you have a magical reactionless thruster doodad that lets you bring yourself to a halt relative to the surface of the earth directly beneath you, just as if you'd jumped out of a balloon that'd somehow made it to the ISS's altitude. Presumably you planned to further employ your reactionless lift belt or boots or whatever to float down majestically at whatever speed you wanted. But when you pressed the button to kill your orbital momentum, the device burned out, and now you're falling.
The ISS's low Earth orbit is about 400 kilometres above sea level. At that altitude, there's still enough of a trace of atmosphere to cause the ISS's orbit to decay by a couple of kilometres per month, so it requires frequent "reboosting" to stop it falling into the ocean ahead of schedule. From the point of view of someone who just told his fellow cosmonauts that he's just going outside and might be some time, though, it's a vacuum at 400 kilometres.
Low earth orbit is high enough that the Earth's gravity is somewhat attenuated, but only from about 9.8 metres per second squared to about 9.0.
So, starting at 400 kilometres and accelerating at nine metres per second per second, with both gravity and air density slowly rising as you fall. I don't know exactly how this'd work out, but I think that by the time you'd fallen 300 kilometres and passed the 100-kilometres arbitrary "start of space" altitude, you'd be falling at about 2.5 kilometres per second.
That's a pretty darn impressive speed, but it's much more manageable than actual orbital velocity. The ISS's orbital velocity is about seven kilometres per second; when the Shuttle Columbiabroke up into flaming particles, it had managed to slow down to around six kilometres per second. Since energy increases with the square of the speed, an object travelling at seven kilometres per second that's trying to slow down has 7.8 times as much energy to get rid of as one travelling at 2.5 km/s.
2.5 km/s at a hundred kilometres altitude would probably be survivable, perhaps with some sort of ribbon parachute or similar drag device to bleed off speed steadily as the air got thicker.
But all of this is a bit silly, because it assumes that you've somehow managed to get rid of the several kilometres per second of your initial orbital velocity. That, there, is the big problem. If an orbiting spacecraft had enough reaction mass to kill its orbital velocity while it was still in space, it could then use wings or pop a gigantic parachute or three and sail down quite serenely, with no need for troublesome heat shields at all.
(This is why the Virgin SpaceShipOne and Two don't need heat shields. They're suborbital spaceplanes, not "real" spacecraft. They go very high by aircraft standards, then they fall back down again, never gaining or having to dispose of actual orbital velocity.)
I was just catching up on your Psycho Sciences (write more!), and read in the one about passive smoking that "very few [Australian] houses have basements", versus houses here in the USA, where we usually do have basements which, as you say, serve as convenient radon-accumulators for householders in need of a higher cancer risk.
Why is this? Is Big Radon Detector Business conspiring with architects to maintain demand?
Some of the differences in dwelling styles between countries are purely cultural, with no very logical reasons either way. Then there are obvious ones like "our houses are made of stone, 'cos there's no bloody wood for 500 miles". And then there are others that make only a very small amount of sense, like the almost complete absence of European-style heat-retaining technologies in Australian houses. This creates the peculiar situation that although a Sydney winter is not unlike a northern-European summer, Sydneysiders spend more time being cold in winter than Finns do, because Sydney houses are usually poorly heated, draughty, and often surprisingly poorly insulated too.
(This applies to Katoomba, where I live, as well. Katoomba winters are still a joke by countries-where-it-snows standards, but overnight temperatures around freezing point are still quite common in winter, as are tourists from elsewhere in Australia gazing in surprise at the ice on their car windscreens and wondering what on earth to do about it. Yet many houses here are built no differently from houses in much warmer beachtowns, and their occupants suffer accordingly.)
Many house-design differences have a quite simple rational basis, though. Like, here in Australia it's easy to find houses with flat, or only gently inclined, roofs. In countries where it snows in winter, there's pretty strong selective pressure...
...against people who choose to live under a flat roof. Here, not so much, and a flat roof is simple and cheap to build.
The snow/no-snow roof design holds for most countries. In very hot areas, a flat-roofed house can also be built to let you sit out on the roof in the breeze of an evening.
The basements/no-basements thing has a rational basis, too, which once again holds for a large number of countries.
Digging a big hole under a house is time-consuming and expensive, and asking for trouble from water seepage. If you want that much extra space in the building, and are not living in some godforsaken wasteland that's shaved flat by tornadoes every ten years, it's faster and cheaper to just build a taller house.
Unless it gets cold enough in the winter for the ground to freeze to a significant depth, and then warm enough in the summer for it to thaw again.
Frost heave makes shallow house foundations a terrible idea. So you have to dig a hole to put the foundations in, and you might as well make that hole into a basement while you're at it.
Some basement-equipped houses are built in places where frost heave never happens, for the abovementioned cultural reasons. But you generally find them in cold-winter locations.
In Australia, you usually have to build to minimise the effects of heat, not cold. This has given rise to the famous underground houses of Coober Pedy, and the much more common "Queenslander" house style...
...where the house proper sits as much as a whole extra storey high on "stumps", to catch the breeze and keep Queensland's trillion species of house- and/or human-eating arthropods that much further away.
...and was very impressed with the information provided.
Is it true that glass fibre batts in speakers can cause mesothelioma? I noticed you linked to the Wikipedia mesothelioma page when discussing polyester and glass fibre batts with the word "carcinogenic".
A ported speaker with glass-fibre wadding inside (it's there to dampen internal resonances) will spit little bits of fibreglass out of its ports in normal use. The cancer risk from these is essentially nil, essentially because the amount of glass emitted is very small. But even larger glass-fibre exposures are generally less dangerous than asbestos exposure, and there's some debate about why this is.
Fibreglass and asbestos are mechanically, and somewhat chemically, similar. Glass-fibre, like window glass, is about three-quarters silicon dioxide (quartz), with the rest being additives, chiefly oxides of light metals, to reduce the glass's melting point and increase its strength and/or chemical properties. All forms of asbestos are essentially silicate minerals too, but with different elements mixed in with the silicon and oxygen.
The most common form of asbestos is the white "serpentine" kind, which is magnesium silicate. Blue and brown "amphibole" asbestos are closer to window-glass, being complicated sodium, magnesium and iron silicate minerals.
Asbestos is so particularly nasty (and useful) because its fibres can be very, very fine, routinely below twenty micrometres (or microns) in diameter, and even down to small fractions of a micrometre, versus around 100 micrometres for a human hair. These ultra-fine fibres are too small to even see, and bits of them can float around in the air waiting to be inhaled. This is why they tent whole buildings and put workers in moon-suits to do asbestos abatement; building materials that contain asbestos can be safe to be near, but as soon as you start busting those materials up, they can product dangerous and invisible dust.
Fibreglass, also known as glass wool, is made in a similar way to fairy floss ("cotton candy", in the USA); extrusion of the molten material through tiny nozzles. The nozzle size determines the thickness of the filaments, so glass fibres can quite easily be made down to single-digit-micron thickness. As is the case for many other "whisker" materials, most of the desirable physical qualities of the fibres increase as the thickness drops. (This is explored in some detail in J.E. Gordon's classic "The New Science of Strong Materials, or Why You Don't Fall through the Floor", a book that I may not have mentioned on this site for as much as eight or nine minutes.)
This electron micrograph of dust from the wreckage of the World Trade Center (via the USGS) shows a thin glass fibre and a bundle of much thinner asbestos fibres.
(Nobody performed full asbestos abatement on the WTC towers while they were standing, because it would have been very expensive, the asbestos was largely safely bound up in building materials, and nobody anticipated that the buildings were likely to fall down any time soon...)
Glass fibres down in the single-digit-micron diameter range are a cancer risk, like asbestos, but glass fibre in general seems to be rather less carcinogenic than asbestos fibres of similar dimensions. Nobody's exactly sure why. Glass fibres don't seem to get stuck in the lungs like asbestos fibres do; this could be purely because of the size difference, or because they don't have the same rough, almost barbed sides...
Glass is also slightly soluble in water, and - it is theorised - fibres in the lungs can thus be slowly eliminated via blood or sputum. For macroscopic objects the water-solubility of glass is essentially zero; you can run water through a glass tube in a laboratory for years with no visible change, and you don't need to worry about rain wearing through your windows. But the thinner the fibres, and thus the greater the risk, the greater will be the surface area of those fibres, so even extremely slight solubility can, the theory goes, get rid of the fibres usefully quickly.
It's important to realise that we're not just talking about cancer, here. Most people with asbestos-related lung disease don't have mesothelioma; they've got "asbestosis", a non-cancerous inflammatory disease which can, nonetheless, very effectively destroy your quality of life and in extreme cases kill you. Again, it's the super-fine fibres of asbestos that make it particularly nasty here, but you can get similar syndromes by inhaling various other particulate substances that get stuck in your lungs, like coal dust, and also little bits of fibreglass.
Realistically, even someone who stuffs fibreglass into speaker boxes for a living, without so much as a face mask, isn't at a huge risk of lung disease - cancer, or "just" an asbestosis-like condition. Usually it's people like surfboard manufacturers or insulation installers who get sick, and then only if they don't use a respirator while they're sanding boards or stuffing insulation batts into unventilated roof or floor cavities.
So if you've got ported speakers with fibreglass in them, don't worry about it. Even if you open the speakers up to replace a blown crossover or something, you're in no real danger. (And if you've got un-ported, sealed "infinite baffle" speakers, there is of course even less risk.) The loudspeaker industry switched to using cellulose acetate or polyester fluff...
...as the normal low-cost anti-resonance speaker-lagging material...
...some time ago, but I think the change was mainly because these fibres are easier to cut and place, and not a prickly skin irritant, rather than for health reasons.
Incidentally, white asbestos and talc, as in talcum powder and...
..."French chalk", are chemically the same, both magnesium silicate. Asbestos can metamorphose into talc, though I'm not sure if talc can go the other way. In any case, industrial-grade talc can be expected to contain some asbestos-like filaments.
This caused a certain amount of panic among people who've applied talcum powder liberally to their baby, or discovered that standard children's wax crayons contained a small amount of talc, which in turn did or did not contain - depending on who you asked - a tiny amount of actual identifiable asbestos.
In response to this, more than a decade ago the big-brand crayon formulations were changed to contain no talc. How crayon-talc was supposed to get into kids' lungs in the first place, I'm not sure. Embedding asbestos in wax strikes me as an excellent way of rendering the stuff harmless, even when kids stick crayons up their noses. Perhaps some asbestos could lodge in the digestive tract if they ate it, but I think the normal regeneration of the gut lining would carry it away. Unless you actually lit a crayon fire, I doubt any significant exposure was even theoretically possible.
The asbestos-in-talcum-powder scare was more rational, because people unquestionably do inhale some talcum powder when they use the product in normal everyday ways. There's a difference between bulk industrial talc and the super-fine stuff used for talcum powder, though. Major talcum-powder companies hotly protested that there was no asbestos in their talc at all.
It's rational to take at least some care to prevent you or your baby from inhaling talcum powder, because, as discussed above, inhaling fine insoluble powders in general is a bad idea. But there doesn't seem to be any serious reason to boycott the product entirely.
(There's also a popular belief that laser-printer or photocopier toner is deadly poisonous if inhaled. Actually, toner is just yet another insoluble fine powder. So, once again, you should avoid inhaling it if you can, and wear an appropriate mask if you have chronic exposure to it. But there's no need to panic if you snort a little of the stuff by accident.)
I have heard on the worksite (construction; I'm working through college as a part-time fetcher and carrier) that if a power line falls, or someone drives a crane into power lines...
...you should move away from the danger site by taking tiny little steps, or even jumps with your feet together.
But I have also heard that I need to go somewhere and ask for a bucket of compressed air, or a "long weight", or a box of right-handed pipe elbows, on account of we only got left-handed ones here.
Is the pogo away from the power line thing just another way to make people look stupid? Doesn't the electricity get grounded into the... ground?
Oddly enough, this is actually good advice. It may not be necessary in a particular situation, but better to look a bit of a dick and survive than stride away in manly fashion and die.
It's all about the voltage gradient. Connect a power line to ground by cutting it or leaning some metallic object against it and the electricity doesn't just magically vanish at the contact point. If the contact point were an actual earth stake driven deep into the ground then even a quite major power-line short pretty much would disappear right there, but if all you've got is some cable draped on the ground, or big voltages buzzing to earth in scary arcs from this and that part of the frame of a piece of construction equipment, then it's sort of like pouring water onto level ground. Some soaks in at the point where it hits, it spreads out and some more soaks in, it spreads out more and even more soaks in, et cetera.
In this analogy, voltage maps to the depth of water on the surface. The closer to the contact point(s) a given piece of ground is, the higher the electrical potential at that spot will be. This is where the analogy breaks down, though, because you will come to no harm if one of your feet is in two inches of water and the other is in one. If one of your feet is on a piece of ground charged to twenty thousand volts and the other is on a ten-thousand-volt spot, though, you'll have a ten-thousand-volt potential from foot to foot, and you'd better hope your shoes have thick rubber soles with no nails.
Here's an occupational-safety video, as cool and stylish as such videos tend to be, explaining this:
The best thing to do is stay in the vehicle and let the electricity pass around you; the metal frame of a truck is way more conductive than a human, and you're probably sitting on an insulating seat anyway.
...though, then hopping out of the vehicle so that you don't touch the vehicle and the ground at the same time, and then pogo-hopping away, is the best chance you have to avoid becoming a very crispy critter. (If you don't want to see the severely charred body of a fork-lift operator who lifted his fork into power lines, don't click here.)
Tiny mincing steps can work about as well as pogo-hops, and may be safer in construction-site terrain. The idea is to get away without falling on your face and enjoying the large potential difference that now exists between your knees and your nose.
Even an actual earth stake may become less and less effective as a current sink if a lot of power passes through it for long enough, because that'll heat the area and boil out the water that makes the ground usefully conductive. The same applies to vehicles that are shorting power lines to ground; as the arcing and burning progresses, the area under the vehicle gets drier and less conductive, and the danger zone expands. Usually the power's cut off pretty quickly, but not always.
(For this reason, dry sand and most kinds of desert-dry ground are a bad place to hammer in an earth stake. Since you'll find water just about anywhere if you dig deep enough - this is the Great Secret of Dowsing - you can get around this problem by using a really long earth stake, provided you have someway to pound it into the ground. Hammering in an ordinary earth stake and pouring water around it will work just fine... until the water drains or evaporates.)
My name is Adrian and I had a question for you and your fancy calculations:
What would happen if you cut an atomic bomb (or any variant of nuclear bomb) in half with a lightsaber, as that bomb was heading toward the ground? My guess is you would disable the detonator but would probably set off the plastic explosive contained within, yet still not detonating the bomb.
This rather depends on what a lightsaber actually is, and what it does. Which is hard to pin down.
Like various other aspects of the Star Wars universe, lightsabers don't really make a lot of sense. The blade apparently weighs nothing but has some air resistance (making a cardboardtube a most effective surrogate!) and, by canon, a strong gyroscopic effect. But that effect is hard to see when, for instance, Luke first twirls his father's lightsaber around in Ben Kenobi's hut. There's a notable absence of precession causing the blade to swing weirdly...
...and cut up Luke, or Ben, or at the very least some of Ben's furniture.
If you need to cut through huge metal doors on a Trade Federation ship it apparently takes a lightsaber a while to do it, but the armour of a seismic tank...
The more you think about this stuff, the less sense it makes. If the damn blade doesn't weigh anything, for instance, why not just do whatever's necessary to make a saber with a really longblade, then point said blade at your enemy, and invite him to impale himself upon it at his leisure? A Jedi asks not these obvious questions, nor does one wonder what the heck people were thinking when they made canonicallightsaber-ishweapons that are clearly more likely to kill the user than their enemy. (See also.)
Oh, and lightsaber blades seem to bind together when they touch, which is what you'd bleeding want to happen when you're fighting with swords that have, in almost all cases, no hand-guard of any kind.
The original lightsaber props had a real gyroscopic effect, because the blade was a spinning stick covered with retroreflective material. You can see and hear one of them in action at the beginning of this blooper reel:
This was originally hoped to provide an adequate lightsaber effect all by itself when illuminated by a light mounted next to the camera lens, for the same reason why retroreflective road signs glow when illuminated by headlights, which are relatively close, angularly, to the eyes of a driver. (If you're on foot and illuminate such a sign with a flashlight held next to your head or, better yet, right between your eyes, the sign will glow surprisingly brightly, on account of the near-perfect angular alignment of the illumination and your eyes.)
The reflective saber effect didn't actually work very well, though, so the sabers were dressed up further in post-production. This left a few telltale signs in the original versions of the early Star Wars movies, especially A New Hope. Before Lucas started "improving" that movie, a saber pointed straight at the camera pretty much disappeared. See also the variable-length, "dual-phase", lightsaber, which was invented to explain why the special effects for Vader's schwartz didn't make it the same length in every shot.
Oh, and lightsabers also tend to be used by telekinetic wizards who can predict the immediate future, so all the arrant Flynning you see lightsaber fighters doing (apparently trying to hit the enemy's sword, not the enemy himself...) is of course entirely explained by... tech tech tech.
Lightsabers seem to be able to cleave through most things instantly (there are several lightsaber-Kryptonite substances in the Star Wars universe to make this less of a problem for storytelling, a la the widely-used sci-fi convention that faster-than-light drives don't work if you're too close to a planet or star, so goodies and baddies can't effortlessly evade each other all the time). The material that was in the kerf of a lightsaber's cut just seems to... disappear. If the blade were actually the stick of ultra-hot plasma that it's meant to be, it'd create a strong wind of superheated air just sitting there stationary making its cool noise, and there'd be a serious explosion whenever you hit anything solid with it, blasting some of that solid into gas at the very least, and possibly more plasma. But nope, doesn't happen. Lightsaber-cut matter just vanishes.
Heck, lightsabers don't even seem to cast any light, a lot of the time. You can see them with your eyes, but no photons from them seem to encounter anything but the audience's eyes. This was of course also a special-effects limitation; the original lightsaber effect was just painting on the film frames, and painting realistic illumination of other objects by the lightsabers was too hard. When it isn't too hard to depict, lightsabers light stuff up just fine.
All of these niggles are, of course, not important. Nobody's pretending Star Wars is even slightly hard sci-fi, so sound in space, and crappy Stormtrooper marksmanship, and ray-guns that shoot beams that travel much slower than bullets, and magic laser swords, are all perfectly acceptable space-opera components. The only time this stuff annoys me is when someone creates yet another of those awful The Science Of Star Wars or Star Trek or Probably Even Bleeding Doctor Who By Now books or TV shows.
The idea always seems to be to trick students who don't like science into learning something, but the result always looks to me like the Lego kits for kids who don't like Lego. This idea is a fundamentally bad one, even if you do manage to wring some actual scientific relevance out of Star Wars, which is about as easy as wringing it out of Jack and the Beanstalk.
If you actually apply something resembling real science to lightsabers, you get a weapon that kills everyone in the building if you ever hit anything with it.
Here's a much more important example of the hopelessness of this The Science Of Some Fantasy Show idea, which arises whenever you try to apply real science to any space-opera scenario that has faster-than-light travel:
Absolutely definitely, no question about it. Doesn't matter if you use hyperspace or a warp bubble or teleportation or jump-gates left by ancient aliens. FTL plus relativity equals time travel.
The usual way to get around this is to subject your fictional universe to an Acme Hydraulic Universe-Flattener and explicitly or implicitly erase relativity entirely. You pretty much have to do this to have FTL in the first place, so it's not that much of a loss.
The only other way out is to boldly declare that the same future technology that created the FTL drive also proved Einstein Was Wrong. Saying that, in the face of the large amount of experimental and practical evidence that both general and special relativity are, in our universe, real, is about as plausible as a physicist today saying Newton Was Wrong.
(Newtonian physics is wrong when speeds, mass and/or time values are very large, but relativity refines Newtonian physics, it doesn't overturn it. Space-opera FTL technology can only plausibly overturn relativity with the help of godlikeentities, the discovery that we live in a simulateduniverse with variable rules, or some similarly cheap trick. Otherwise you might as well be saying that new discoveries have revealed that four is prime.)
A significant amount of modern literary space-opera acknowledges the FTL-equals-time-travel problem, but time travel only happens occasionally in shows and movies whose names start with "Star", and it's usually a great surprise to the cast when it does. (And an even greater one, to the characters at least, when they travel from the future back into the same year, and usually the same city, when the show was actually filmed.)
This is all just a teeny bit of a long walk to my answer to "what would happen if you chopped a nuke in half with a lightsaber?", but I hope it explains why my answer is "damned if I know, but the special effects would be good, and the acting lousy".