How to Spot a Psychopath

A reader writes:

OK so this looks really cool:

Alabama-Based CMR Demos Programmable Magnets That Changes Polarity And Strength On A Whim

As long as they don't violate the laws of physics that is. What do you think, scam or not?

Peter

I don't see any reason to think that Correlated Magnetics are doing anything snake-oil-y. They've just got a way of making single magnets which contain multiple differently magnetised regions.

Take the above "Hoverfield" demonstration unit gizmo, for instance...

...which you can buy for a hundred bucks if you like.

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-earth magnets.

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.

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.

A reader writes:

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).

Timothy

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-cam phenomenon, 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 Agency similarly 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-killer meteorites 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".

I propose we use the PEPCON explosion instead.

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.

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.

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?

Florian

(Everybody's seen the real video.)

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.

EDIT: As per ix's comment below, 13,000 feet is actually quite a common skydiving altitude for, as arkikol's comment explains, regulatory-loophole reasons.

(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 Columbia broke 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.)

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

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

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?

Luz

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 beach towns, 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...

(Image source: Flickr user HoundCat)

...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.

If that's the case, then "frost heave" (which, coincidentally, is yet another thing Matthias Wandel has had to deal with) will slowly push anything sitting in the freezing and thawing earth up into the air.

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...

(Image source: Flickr user Crazy House Capers)

...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.

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

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