More green ink by e-mail

A reader writes:

Dear Dan
I purchased some modulators from Mr Orchard and had one of the units tested using a machine called a PowerMate that is made in Adelaide.

The result was a 30% reduction in power consumption. The test was done over a 3 month period.

Mr Orchard is way ahead of his time. People just on get it!



The contents of this e-mail is highly confidential and for the intended recipient only and to the e-mail address to which it has been addressed to. It's contents may not be disclosed to or used by any other 3rd party other than this addressee, nor may it be duplicated in any way or format without prior consent by the sender. If received in error, please contact the sender by email quoting the name of the sender and the addressee and delete it from your email server and email client software. The sender does not accept any responsibility for any forms of viruses, spyware or malware. It is the responsibility of the receiver to scan all their incoming e-mails and all attachments that have been sent to them.

First, no, e-mail sent to a stranger is not confidential, and no disclaimer boilerplate at the end can make it so. (I'm not sure what the "commercial" part is supposed to mean, either.)

EMPower Modulator

That aside, I presume you're sincere about your statement about seeing the magical EMPower Modulator doing at least one of the numerous extraordinary things it's meant to, and I will also grant for the sake of argument that the test you saw was not rigged, or performed with a defective power meter. (The "Power Mate" is I think meant to be able to take reactive loads into account; cheap power meters like the ones I write about here cannot fully do this.)

In that case, all I can say to you is the same thing I say to everybody who says they know of some gadget that reduces electricity consumption, or improves fuel economy, or in some other way could save a lot of people a lot of money:

Why is the person who has been selling this thing for so many years or, in many cases including that of Harmonic Products, DECADES, not a billionaire Nobel-Prize winner?

You demonstrate your device informally. You talk journalists and a technical college or two into testing it. With that evidence, you talk serious test labs and/or universities into testing it. And then there you are with your proven invention that, because most of the world's population will want it, is not worth millions of dollars; it's worth billions. Hell, even if an evil corporate conspiracy steals your invention, rips up your patent and robs you of your rightful reward, you will still have greatly bettered the lot of humankind. Provided, of course, that the evil conspiracy doesn't tuck your gadget away in the same vast warehouse where they keep the Ark of the Covenant and the hundred-mile-per-gallon carburettor.

There are hundreds of these things. Fuel savers, power savers, perpetual-motion machines, things that allegedly enhance health or cure deadly diseases by means unknown to science, and of course persons distributing the wisdom of super-advanced aliens via channelling.

All could revolutionise the world, if true. None have ever managed it. They always just sell the gadgets, or tickets to their performances, one at a time to punters like you.

(And, notably, they do not mysteriously vanish when the abovementioned giant corporate Illuminati Freemason conspiracy catches up with them. A lot of these people have been selling the same scam pretty much all their lives, without any repercussions beyond getting serially busted by the government because they keep taking people's money and running.)

The closest these miracle devices and potions get to actual success is when they manage to be bought in quantity by someone who hasn't applied any proper tests to see if they work, or who are just hoping to turn a buck on resale or shares in the company. See the ADE 651 "bomb detector" and its various relatives, for instance, and the whole miserable Firepower saga.

If the EMPower Modulator works, it is a miraculous device, and I use that word advisedly. (The same goes for the pieces of purple aluminium jewellery that Harmonic Products told me protect the wearer from radiation, make beverages take better, make metal on your person invisible to metal detectors unless you intend to do something bad with that metal, et cetera et cetera.)

But apparently Harmonic Products are perfectly happy to frame a lottery ticket and hang it on the wall for visitors to admire.

They say it'd win a billion dollars, if they only cashed it in.

Why haven't they?

UPDATE: Peter replied to me, with the following cogent rebuttal:

Yes the world is flat and the Sun revolves around the earth.
Happy sleepwalking.

Sent from my iPhone

I'm not sure whether he's agreeing with me or not.

(There was no boilerplate confidentiality disclaimer this time. Presumably he's cool with his e-mail being published, provided he sent it from his phone.)

Supplementary statistical struggles

A reader writes:

First off, thank you for running such a great site. I love learning from you, and the comfortable way you write so well. (You are a net benefit to the planet, something not true of many of us.)

So I apologize for criticizing. But unless I'm seriously misunderstanding you, your bit on chances of getting hit by a rocket is off.

It seems perfectly reasonable that the distribution of rockets hits will be a Poisson distribution: i.e., for a given area and a given unit time, a Poisson distribution will model the probability of getting hit once there in that time, versus twice, versus n times, versus never. (And note that this varies linearly, as you would expect, in both area and period of time.)

But the thing about a Poisson distribution is that it is (as the statisticians like to say) memoryless. The chance of getting hit in some area in any unit time is independent of how many times that area's been hit in the past.

So, sure, the chances of not getting hit in the next hour and getting hit in the hour after that are lower, by multiplication of probabilities, than the chances of simply getting hit in the next hour. But that's not a question anyone cares about, is it? Answering what I understand to be the writer's question, he's asking whether, an area having been hit in the last h hours, it is more or less likely to be hit in the next, say, h hours, And the answer is, if the rockets are no more aimed than V-2s, that it doesn't matter whether or not the area's been hit before.

But, again, what a great site you do. With thanks,


You're exactly right about the characteristics of the Poisson distribution, and the fact that a chance of a future hit does not depend in any way on whether a hit happened in the past, presuming hits truly are randomly distributed.

But the NEXT [arbitrary time period] in which any [arbitrary location] is likely to be hit is still the VERY NEXT [arbitrary time period], if the distribution is random. Because, as per the lightning-strike analogy, for a hit to happen the [time period] after next, it must NOT happen in the next [time period]. This gives lower and lower probabilities of the next hit being at a given time the further that time is in the future.

(You said this too, but I'm repeating it yet again because it's one of the slipperier statistical concepts and has led to a lot of erroneous conclusions on a wide range of subjects. See also non-transitivity, mechanical failure stats, and tax brackets.)

As you say, this is still no help at all in figuring out where and who is going to get hit, or not. But it's the explanation for the "clusters" that often make random events look very NON-random, and my correspondent from Israel wanted to know whether this apparent un-randomness was of any predictive value. Which, as you say, it unfortunately is not.

(Also, in reality, human aiming of even unguided garage-built rockets may entirely swamp the random-clustering effect. So in reality a missile landing in some particular place probably does mean more missiles will land there, but not because of any abstract quirk of probability.)

So much for science. But at least we can get drunk!

A reader writes:

From: Ernest
Date: Fri, 28 Dec 2012
Subject: Wine Clip

Your review is entertaining but is not very helpful. I have used a Wine Clip for about 3 years, and frequently do a blind test on myself. Naturally, having some one else do the pouring.

After all, I don't really care whether some one else thinks the wine is better using the Clip. I am the only relevant person involved. And it works every time! Red wine is better when the Wine Clip is used. That is what is important to me; after all, I am the consumer.

There is a factor in the use of panels. The participants should never know it is a test. (I found this out when I was doing panel responses. Whether it be taste, smell or any other perception, translation by the brain of the perceptions received is influenced by the environment.

But you are right about one thing. Great magnets!

The Wine Clip

What would you do, Ernest, if someone sent you an e-mail that said, "Your commentary on the Psychotronic Money Magnet is entertaining but is not very helpful. I have used a Money Magnet for about 3 years, and always make more money when I have it hanging around my neck than when I leave it in the bedside drawer"?

Would you, in response to this, drop everything and dash out to buy a Money Magnet from one of the... differently-cognitive... people who sell them?

Would you turn your whole comprehension of the world upside down, because apparently it seems that the free will of other humans and the very workings of abstract probability can be distorted by a talismanic device that works by, uh, quantums, and stuff?

Or would you, rather, presume that the fellow e-mailing you might have not quite the right end of the stick?

I do not doubt that you believe the Wine Clip works. I am intrigued by your claim to have tested it in a controlled, though not double-blind, way. I do not consider your claim plausible, though, not least because if it's correct, then the whole of electrochemistry, indeed most of modern physics, is not. Countless carefully-assayed chemical mixtures are exposed to magnetic fields from the modest to the monstrous every day, with the assumption that those fields will not modify any molecules and mess up the experiment - and the fields never do.

Unless you stick some magnets on a wine bottle, apparently. Then, suddenly, physics goes out the window and "tannins" start getting broken up by magnetism.

Since I am surrounded every day by evidence that magnetic fields do not pull molecules apart, and a good thing too or writing this piece would almost certainly have killed me, I am afraid I can only conclude that there is probably something wrong with your testing regimen. Your collaborator is accidentally signalling you - without your conscious knowledge - or the Clipped pour is consistently the first or the second, or any of the hundreds of other possible variables for which a good test must control, which is why good tests are so difficult to do.

Note that James Randi told me, personally, that he has specifically requested that makers of magnetic wine-treatment devices demonstrate the truth of their claims in return for worldwide fame and a million dollars.

Not a peep.

(You are of course welcome to join the many other believers in paranormal events who say that the Randi Challenge is clearly some kind of scam. I would venture the opinion that a scam-challenge looks more like this.)

But wait a minute - why am I bothering to say all this to you, when you conclude by saying that tests that people know are tests aren't useful anyway?!

I'm currently writing a piece in response to yet another example of audiophile weirdness, and this "the participants should never know it is a test" thing comes up there, too.

I even managed to find someone claiming that the fact that blinded tests are objective makes them bad. Because, see, if a proper test shows you that a $900 audiophile widget does nothing, and you therefore save some money and don't buy that widget, you then won't be as happy listening to music, because even though you now know it was a placebo, you still need that placebo in order to fully enjoy the music. Or something.

But... didn't you say you frequently do blind tests on yourself, Ernest?

If objective testing doesn't work if the testees know they're being tested, I suppose you don't know when these blind tests are happening, right?

So is it something like, your wife sometimes doesn't use the Clip when you think she is using it, or something? And then asks you what you think of the wine, which for some reason doesn't alert you to the fact that another "test" is in progress? And then you turn out to be the first person in human history completely immune to cues from a non-blinded researcher with whom you have a personal relationship?

I'm really trying to not insult your intelligence here, Ernest, but you're not making it easy for me.

Of guns with, and guns on, rails

In the comments of my post the other day comparing electrical and firearm energy levels, commenter "hagmanti" was delighted to be informed that the blast of flame coming out of a rail-gun's barrel...

Railgun muzzle blast

...which makes it look more like a normal chemical firearm than most normal chemical firearms do, is vapourised rail and projectile material.

This is a serious problem for both military and... hobbyist... railguns. Damage to the projectile is not that big a deal as long as you're only firing "kinetic kill" lumps of metal, not explosive-filled shells. But a gun that needs to be torn down and have major components replaced every few shots is not a practical weapon.

There are actually analogous problems with a lot of other unreasonably powerful guns. Truly monstrous artillery like railway guns (often, confusingly, also referred to as "rail guns") could fire only a few hundred rounds - even with WWII technology - before the whole huge barrel had to be replaced.

Paris Gun

At least one of those railway guns, the World-War-One Paris Gun, had a series of shells of gradually increasing size to be shot in order, so the bullet always fit the barrel.

The same thing happens to small arms. A frequently-used rifle barrel will eventually be "shot out" and lose projectile velocity and accuracy, as the bullet bounces down the worn tube. It just happens a lot faster if you perversely insist on 120 million joules, or around 1.7 billion joules, of muzzle energy, for the Paris Gun and...

Schwerer Gustav

...Schwerer Gustav, respectively.

For comparison, the 16-inch guns on the Iowa-class battleships were good for a feeble 355 million joules or so, and three hundred or so full-power firings before the barrels wore out.

In their later life those mere 16-inchers became rather more destructive than any of the railway guns, though, on account of how they could toss fifteen to twenty kilotons of instant sunshine at the enemy.

And then there's the multi-chamber gun concept, where the initial propellant charge behind the shell is relatively small, and the barrel has branches containing subsidiary charges that are timed to go off after the shell has passed them. This design lets you have very high muzzle velocity without beating up the barrel, or the shell, with a single immense propellant explosion; multi-chamber guns could be used to launch satellites, as well as to kill people. But nobody's ever really gotten them to work, which is, I think, in most cases just as well.

12 AAs in the magazine, one in the chamber

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?


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... 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...

Ridiculous contraption

...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.

More magnets

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

Various magnets

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.

Fridge magnet field pattern

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!

Falling from the friendly skies

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?


(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:

Speed of sound vs altitude

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.

In New Zealand, the hobbits have them

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 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...

Carport snow collapse
(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...

Queenslander house
(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.