How to Spot a Psychopath

A reader writes:

I wash my hands after going to the bathroom. I do, honest! But... maybe if I've only had a wee, I might just sort of... splash them a bit.

I know I'm being disgusting. How disgusting am I being?

Patrick

Washing your hands without soap has almost no impact on the amount of bacteria on your skin. The only reason to do it is if all you want to clean off your hands is something, like, I don't know, sand or poster paint or something, that plain water easily removes.

But if your hands are covered with, for instance, garden soil, you may be able to get them apparently clean with plain water, but plenty of bacteria from the soil will still be there.

(UPDATE: It seems that it's a bit more complicated than that. Some researchers have found that you actually can wash your hands effectively without soap! You need to rub your hands together "purposefully" for at least 20 seconds under running water, though.)

Holding, not to put too fine a point on it, your penis while you urinate, probably will make your hand (or hands; I'm making no assumptions about your technique or dimensions) significantly more bacteria-laden. And the bacteria you pick up there can be nasty ones. Coliform bacteria, including ones that can cause an unpleasant stomach upset at the very least, are all over normal human skin in the approximate area that boxer shorts cover. You can't get rid of the buggers completely without bathing in antiseptic and scrubbing yourself with a wire brush.

(This is why no amount of bathing will prevent your armpits getting smelly when you start sweating again. The smell is the metabolic products of bacteria that thrive in sweat, and those bacteria live in the pores of your skin and can't all be killed without killing, or physically removing, the skin as well.)

Washing your hands with ordinary soap does, fortunately, get rid of coliforms on the surface of the skin, which is where they'll be if you've just been handing your privates. The soap doesn't kill the bacteria, but it gets rid of the oil on the surface of the skin, and washes most of the surface bacteria away with it.

(Hand sanitiser is usually based on alcohol, which also cuts the oil on your skin and actually does kill bacteria quite effectively. Washing with soap gives you live bacteria going down the plughole; hand sanitiser without washing gives you dead bacteria still sitting on your skin.)

And yet, persons in a normal state of health who don't wash their hands at all after going to the toilet will, demonstrably, not cause themselves, and everyone else they touch, to constantly get gastroenteritis. This is because bacterial transfer and growth is a statistical sort of thing.

Harmful strains of bacteria, and viruses for that matter, only become a problem when they get into your body, and can multiply faster than your immune system can get rid of them.

Let's say you've got a normal immune system, and you go to the bathroom, wash your hands in a perfunctory manner with no soap, and later on decide to eat some chips or perform some other activity that transfers bacteria from your hands to the upper portion of your gut.

You'll probably be fine, just as you will probably also get away with driving while mildly-illegally drunk.

But doing this buys you quite a lot of tickets in the Pathogen-Disaster Lottery. If you get a big enough dose of bad enough germs into yourself, your immune system won't be able to react and shut them down before they've multiplied into too large a population to stop, and then you'll be in trouble.

Which, again to not be over-dramatic, probably won't be the kind of trouble that kills you. But may be the kind that initially makes you afraid that you will die, and later on makes you afraid that you won't.

(Going around covered with nasty microorganisms also makes you a significant hazard for people with lousy immune systems - the very young, the very old, and the otherwise infirm. You don't even need to touch them; every time you leave a germy handprint on some non-antimicrobial surface, it'll wait there for quite some time to give the microscopic gift that keeps on giving to someone else.)

Any kind of hand-washing with soap will reduce the number of tickets you buy in the lottery you don't want to win, and washing your hands thoroughly with soap makes the risk essentially zero. (To do it properly you're meant to take at least 20 seconds, which can seem a rather long time while you're staring at yourself in the bathroom mirror.)

It's not just bacteria from your own body you have to worry about, of course. There are also pets, and rubbish bins, and all of those surfaces you have to touch any time you leave the house, and other people, and of course also other people's sticky, shrieking, waste-encrusted offspring.

My partner, a while ago, got really horrible gastroenteritis, the kind that sees you in hospital being intravenously hydrated on more than one occasion. I managed to get through the experience without getting the bug myself, and I didn't wall myself up in the attic and only touch her with robotic waldoes to achieve this. You'd better believe I washed my hands often, though.

Ever since, I wash my hands properly whenever I come home, and whenever I've handled anything that could plausibly be well-loaded with bacteria and/or viruses. And I've not had any tummy bugs since - though I didn't get them frequently enough beforehand for this to have generated any statistically significant data.

You don't need to go completely Howard Hughes about all this, but you also don't need to work in a hospital for a greater than zero level of germ-consciousness to be worthwhile.

Note that unless you've got a bladder infection or something, urine itself is very close to sterile (not quite fully sterile, because even a healthy urethra can contribute a few bacteria to it). Nice and warm, too.

So if you just put a soap dish on top of the toilet, you could probably get the whole job done in one operation.

(The non-comedy version of this is the cistern-top sink, available in relatively modest and also huge expensive designer versions.)

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.

A reader writes:

A thought struck me while driving home one night: If relativity means the speed of light is absolute, how is it possible for there to be a Doppler shift of light?

As I understand it, Doppler occurs when a wave source is moving and the peaks/valleys of the wave get scrunched up/stretched out.

The theory of relativity states that light shining from a moving vehicle is NOT traveling c (light speed) plus the speed of the vehicle, because time slows down relative to the stationary observer.

If all the crests of the wave are traveling at c and Relativity implies that the point source can't go any faster than c, then it would seem there's no way for there to be any shortening of the frequency.

How does relativistic time dilation not cancel out the Doppler effect much like the added speed of a vehicle is canceled out?

Add in the wibbly-wobbly-timey-wimey grey area of light being both a particle AND a wave at the same time and my brain is hurting me for trying to visualize how the Doppler shift works for light.

Chris

You are, and this is not something that's often said to people coming to grips with Einstein's theories, overthinking this.

Yes, as special relativity says and as everybody who talked to Einstein about it firmly understood until the concept slithered out of their brain about ten minutes after the end of the conversation (relativity is even worse than tax brackets in this regard), the speed of light is indeed a universal constant. No matter how fast the observer, or the source of the light, are moving relative to each other or relative to anything else, everybody always sees the speed of light in a vacuum as the same 299,792,458 metres per second.

(Things get a little more complicated when the light is moving in a medium other than vacuum, but our universe, at least, is conveniently largely made of vacuum. This is a useful thing to remember if someone attempts to persuade you that the universe has been fine-tuned just for us; if this were actually the case, 99.9999-and-several-more-nines-per-cent of the universe might fairly be expected to not be instantly lethal to humans... but it is. Oh, and just to make things a little more confusing again, Einstein also came up with a theory of general relativity, which has to do with gravity and is different from special relativity.)

So, as you say, light doesn't go past you any faster if the light source is coming at you, or any slower if the light source is moving away.

But when the source of a sound is coming at you, the sound doesn't pass you any faster, either.

The speed of sound is much less constant than the speed of light. Sound travels faster the "stiffer" the material it's travelling through is, so it's zero in a vacuum, around 343 metres per second in dry air at sea level, but about 1500m/s in water. Unlike the speed of light, it is of course possible for things to travel faster than the speed of sound, especially in air. But even when a sound-emitting thing, like a jet fighter, is travelling faster than sound, the sound it emits still travels at whatever the speed of sound in that part of the atmosphere is.

(This is why you don't hear a supersonic plane, or a supersonic bullet, coming...

...until it's already gone past you. In the case of a bullet, the noise it makes is pretty much entirely the "sonic boom" created by pushing air out of the way faster than sound. The shock wave around a supersonic aircraft, bullet or explosion can travel faster than sound, but the shock wave slows as it spreads out, and soon becomes a regular sound wave.)

But, as you say, the Doppler effect clearly changes the pitch of sound made by an approaching, departing or...

...passing sound source.

The reason for this is that when a sound source is approaching you, each new oscillation of whatever sound it's making is emitted when the source is a bit closer to you than the last, which puts the compressions and rarefactions of the sound waves closer together. This is, from your point of view, exactly the same as if you were listening to a stationary sound source making a higher-pitched sound. And if the sound source is moving away, the opposite happens.

Light is, once again, a somewhat more squirrelly concept, because as you say, photons have characteristics of both particles and waves. In this case the analogy still works fine, though; once again, the source of each new particle-photon or wave-photon is closer to you, or further away from you, when each new photon is emitted, creating the same effect you'd see if the light were coming from a stationary source with a higher or lower frequency, respectively.

It's often misleading to apply observations in the everyday world of modest velocities, masses and timescales to the much greater velocities, far larger masses, and/or much longer timescales which cause Newtonian physics calculations to give you clearly wrong answers, so that Einstein's refinements become necessary. In this case, the trap lurking in the speed-of-sound to speed-of-light analogy is that if you move towards a sound source, the speed at which the sound waves pass you, in your frame of reference, really will increase.

Sound waves can also pass you faster, or slower, than the speed of sound in a given medium if that medium (air, for instance) is itself moving from your point of view (because you're standing still and the wind is blowing, for instance). If you and the sound source are both stationary and a steady wind is blowing from the source to you, you'll encounter the peculiar situation in which the sound waves are passing you faster than sound, but the pitch is staying the same!

If you assume a stationary listener, no wind and perfectly spherical and inelastic cows, though, the light-to-sound analogy works.

Time dilation is irrelevant, here. If you're in a spaceship with red headlights and you're travelling at close to the speed of light, time will pass slower for you, from the point of view of a stationary observer, and your headlights will look blue, to a stationary observer in front of you. But the time-dilation affects everything on and within your spaceship, including you, your headlights and the tiny 32,768Hz quartz tuning-fork resonator...

(Source.)

...in your wristwatch. So from your point of view, your wristwatch still counts one second per second, and your headlights are still red. (But the universe in front of you will look bluer, and the universe behind redder. The sound analogy works here, too; if you're in a car driving past a stationary car that's beeping its horn, the horn will sound higher as you approach and lower after you pass by.)

But if you assume a stationary listener, the speed-of-sound to speed-of-light analogy works OK. The sound, or light, passes you at the same speed no matter how fast the source is travelling, but the sound, or light, waves arrive closer together when the source is approaching, and further apart when it's departing.

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.

A reader writes:

Could you build a tabletop cathedral out of sugar cubes?

What I mean is, of course you could build one out of soapstone, or soap, or wax, or whatever, but all of those are so strong you can get away with pretty much anything. Snow is weak but so light you can build a shelter out of it with no particular concern for architecture (though I once had an unpleasant surprise when it got warm overnight - "wait, should I really be seeing stars? and what's this weight on my legs?"). But sugar cubes are both heavy and fairly crumbly.

So could you build a cathedral of reasonable size and have to deal with similar engineering difficulties to those medieval stone-cathedral builders did?

Anne

Never having tried it myself, and not even having any sugar cubes in the house, I reckon you could build something pretty impressive with them. I think they may indeed be quite good analogues for unreinforced historic masonry, at around a 1:100 scale. And yes, this could be quite instructive, like the classic spaghetti-bridge exercise that also forces the architect to work with a material that behaves in small scale not unlike real construction materials at full scale, neutralising the square-cube law that tends to make models unrealistically sturdy.

(Look at this enormous model, for instance. It's held together with glue, which may reinforce the cubes significantly, or may not.)

The compressive, and tensile, strength of materials is defined in pascals, one pascal being one newton of force applied over an area of one square metre. Because of this rather large area, even quite feeble materials achieve strength scores up in the kilopascals (kPa).

If your sugar cube is, for the sake of argument, one centimetre square, its share of a 1 Pa pressure over a square metre would be only one ten-thousandth of a newton, which is the kind of pressure a marshmallow could withstand without visible deformation. Crank the pressure up to 10,000 Pa (ten kilopascals, kPa) and the sugar cube will be supporting a whole Newton, equal to a weight of about 100 grams under normal Earth gravity. This seems a plausible sort of strength for a sugar cube to manage.

The compressive strength of modern bricks and concrete blocks is up in the single-digit megapascals (or considerably higher, if the bricks or blocks don't have the usual holes through them); some natural stones are much stronger (granite manages around 200 MPa), but natural stone is likely to contain cracks and fissures that make the safe load limit considerably lower.

If sugar cubes turn out to actually be feeble, it might not actually matter that much, because the full compressive strength of masonry is surprisingly unimportant a lot of the time. You could build the Empire State Building out of stone, or possibly even ordinary bricks, and be in no danger of crushing the bottom blocks with the weight of the rest. That building would be spectacularly unsafe - even with a big reinforced concrete foundation to prevent it from subsiding into the earth, tilting and then toppling, things like wind stress and very minor seismic events could destabilise a giant stone tower very easily. (There is a reason why the longest-lived colossal stone structures in the world are approximately the shape that collapsing stonework naturally creates.) But compressive strength, at least, would not be a problem.

The centuries-old cathedrals that survive are, generally speaking, well engineered, but this is because they're the ones that didn't fall down. A lot did. Pre-scientific architecture was a trial-and-error, evolutionary process, in which people built things that looked as if they'd stay up, and then hoped that if the roof did fall in, it wouldn't be on a full Easter congregation. Sometimes there's evidence of a forced design review in the middle of a building's construction; the Bent Pyramid probably looks the way it does because it became clear to the builders half way through that they were making something too tall and pointy to stay up.

Very few collapses had anything to do with masonry being crushed by its own weight, though, except when some genius decided to use masonry like wood and, say, try to bridge pillars with a slab of stone (the ancient Greeks did this sort of thing quite often, which is why the Parthenon is as ruined as it is. There's a fabulous stack of broken lintels hidden inside the Great Pyramid, too; one broke, they put another one on top, it broke, they put another one on, that one burned down, fell over, and then sank into the swamp...).

Another great way to accidentally put masonry in tension is to put a darn great dome on your building, which will push down and out all around its base. Masonry must then be tricked into keeping force paths safely within the stone by contrivances like, for instance, flying buttresses. If you must have a huge dome, you either need a lot of these tricks, or a circle of very stout iron chain hidden inside the dome's base.

Getting back to sugar cubes, they're not actually all that dense, since they're a porous sintered aggregate of sugar particles (which is essential; a solid cubic crystal of sugar would look pretty neat, but you'd be waiting a while for it to dissolve in your tea). The density of sucrose is only about 1.6 grams per cubic centimetre in the first place.

So if we ballpark the mass of each once-centimetre cube as one gram, and set the ceiling supportable weight as 100 grams, we can stack 100 cubes on top of each other before the one at the bottom is under unacceptable strain. I've no idea how close these numbers actually are to reality, though, and there are no doubt considerable variations between different brands of sugar cubes (some of which are rectangular cuboids, not cubes at all), how they've been packed and otherwise treated, the same sugar cubes under different conditions (humidity, mainly), and so on. I invite actual experimental evidence from readers below; stack things on sugar cubes until they're crushed, and tell us how much weight your cubes can stand!

(In the above blather about historical architecture, any seeming brilliance on my part was actually just relayed from the author of two of my favourite books in the whole world, J.E. Gordon. The relevant book here is "Structures, Or Why Things Don't Fall Down", but "The New Science of Strong Materials, or Why You Don't Fall through the Floor" is also essential reading for anybody who, on reading those titles, realises that they don't really know why these unfortunate events do happen so seldom in the modern world.)

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.

A reader writes:

How does the "sugar rush" work?

My kids go crazy when they get candy and soda (which they usually don't, but I'm not so cruel a mom as to feed them carrot sticks on their birthday), and on the rare occasions when I drink non-diet soda I get about 15 minutes of energy followed by a miserable crash... but now my doctor tells me that the sugar rush doesn't actually exist at all, so it's all in my head. And my kids' heads, too, apparently.

The doctor's not very tactful, but he's always seemed pretty sharp to me. Is he right?

Judy

Yes, your doctor is right. There's no such thing as a sugar rush. Sugar is not a stimulant, whether it's glucose, sucrose, the High-Fructose Corn Syrup that continues to rain stickily down on the entire population of North America, or any of the other sweet-tasting whatever-oses.

If you eat something with simple sugars in it that all pass into the bloodstream quickly - glucose, which doesn't need any digestion, being the simplest of all - you can end up messing with your body's sugar metabolism. Presuming you're not diabetic, your pancreas will pump out a lot of insulin to cope with the sugar bomb and then, when all of that sugar is quite suddenly dealt with, your body may find itself with an insulin surplus and give you a low-impact version of diabetic hypoglycemia. Lots of non-diabetic people have symptoms like this; it's even possible to feel the shaky, mind-fogged symptoms of mild hypoglycemia when your blood sugar and insulin levels are perfectly normal.

(The most important difference between "real" diabetic hypoglycemia and this pseudo-hypoglycemia is that the second version isn't dangerous. Just have a lie down, and in due course your body will drift back into homeostasis and you'll feel better. If a diabetic tries treating hypoglycemia that way, they can end up very ill, or dead.)

A transient hypoglycemic state does feel like a post-stimulant "crash", so there's solid basic biology behind that half of the "sugar rush" experience. There just isn't any actual rush at the start, unless you were hungry enough to feel faint when you ate that block of chocolate or drank that Humongous Gulp of fizzy sugar-water. And in that case, you again didn't get an actual rush, just a rapid return to normal function, which under the circumstances you could easily interpret as a rush.

(I'm ignoring, for the purposes of this discussion, the case of caffeinated drinks. Those certainly can give you some sort of "rush", followed by a crash, but it's not because of the sugar.)

So why do so many people swear that their kids go hyperactive when full of ultra-high-glycemic-index party food?

Well, it's partly because small children at birthday parties have a tendency to go nuts no matter what you feed them. And it's partly a placebo effect.

It doesn't seem as if it should be a placebo, though. If a child's had it drummed into them that they're expected to go hyperactive when they eat lollies, it wouldn't be terribly surprising if they did. But without such an expectation, sugar should have no particular placebo effect on the child.

But the placebo effect we're talking about here isn't happening to the child. It's happening to the adults who're observing the child. I don't know if there's been much research into this, but it's plausible for a couple of reasons. One is this study, which found that mothers who believed their young sons were "sugar sensitive" were more likely to perceive hyperactivity in their child if they're told the boy had been fed sugar, and less likely if they believed the boy had had an artificial sweetener, even though all of the children in the study actually got the artificial sweetener.

The second reason is that an analogous situation exists in veterinary medicine.

There are all sorts of nutty woo-woo alternative-medicine treatments available for animals, even openly preposterous activities like chiropractic adjustments for horses, performed by human beings with their bare hands. To actually shift the vertebrae of a horse around you'd need the assistance of the Incredible Hulk, or at least a very large mallet. But there the horse-chiros are, prodding and pushing and pretending something's moving (see also, "craniosacral therapy"...), and it's not hard to find horse owners who're convinced their animal's much healthier after the pantomime is complete.

So this is the placebo effect at one remove. The owner of the horse, or the parent of the child, can swear up and down that they see a clear difference, when one does not in fact exist.

(There can also be a direct placebo effect in veterinary medicine; an animal can be expected to change its behaviour if a strange person comes and messes with it, whether or not anything of real medical value is taking place. Animals are renowned for perking up when you take them to the vet, the usual explanation given being that they're in a scary environment and trying to look as strong and healthy as possible to avoid being selected for lunch by some unseen predator. This is a bit of a Just-So Story, though, because there's no way to prove it right or wrong until someone finds a talking dog. But never mind that for now.)

There are good reasons not to feed your kids a lot of sugar. But there's no reason to suppose, and several reasons to not suppose, that sugar has anything to do with hyperactivity.

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.

A reader writes:

Hey, I get cheese sweats too!

While we're on the subject, when I drink alcohol, especially spirits, it makes me feel warm, starting in the stomach and moving out. How "real" is this effect? I presume it's not actually changing my core body temperature, because that'd make a shot of Jack Daniels a life-threatening event. What's actually going on?

Derrick

Alcohol indeed does not change your core temperature, but it genuinely can change the distribution of heat in your body. Ethanol is a vasodilator; it causes the smooth muscle around blood vessels to relax and let more blood through. If the ambient temperature is cool, your peripheral blood vessels will naturally be somewhat constricted, reducing blood flow to your extremities; when the vessels dilate, more warm blood flows through those outer vessels, the tissue there thus warms up, and you feel warmer. Because some parts of you genuinely are.

In extreme situations, this can be dangerous. The reason why the body constricts outer blood vessels when it's cold is specifically to avoid losing valuable heat via the extremities. Knock back some Scotch when you're hypothermic and it'll make you feel better (because of both the vasodilatory warming effect, and the psychoactive effects of the alcohol), but you'll also accelerate heat loss and actually make the situation worse.

(For this reason, although St. Bernards are used for alpine rescue, they've never had little barrels of brandy hanging around their necks. Oh, and the whole vasodilator thing also made the traditional use of alcohol as a snake-bite remedy actually a really bad idea.)

In non-life-threatening situations, like when you're cold but not dangerously so and come in to sit by the fire in the ski lodge, alcohol may help you warm up by increasing blood flow through the extremities that're now being warmed by the fire. More prosaically, an alcoholic nightcap can help with that vicious circle where you get into bed with cold feet and your feet stay cold, because cold feet don't have the blood flow to produce much heat for the bedclothes to retain.

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.