short, silly

Halloween Hypotheticals (probably NSFW)

  • Is lycanthropy sexually transmissible? In the movies, if you get bitten by a werewolf, you become a werewolf. So if you have sex with a werewolf, do you become a werewolf? Can this be prevented by condoms or similar? Can you catch lycanthropy having sex with a werewolf if they’re in human form, or is it just when they’re in wolf form?
  • For that matter, can you catch lycanthropy from a werewolf in human form in general? What if a human-form werewolf gets high on meth and bites you? Do you catch it then?
  • What wavelengths in sunlight are vampires actually sensitive to? In general, they seem to be more or less okay with artificial lighting (candles, light bulbs, etc.). Is it ultraviolet? It seems like it’d be ultraviolet. Could you ditch the strings of garlic and protect your house with a blacklight in the foyer?
  • I always assumed vampires had hollow fangs they used to siphon blood out like hypodermics. Apparently, that’s a minority view. Do they just make puncture-holes and then suck the blood out with their mouths? I guess that makes sense, but on the other hand: vampire hickeys.
  • Exactly how full does the moon have to be for a werewolf to transform? Is there a range? Do they turn into wolves whenever the disk is more than 95% illuminated? Or is it just a once-a-month cycle, like a menstrual period or a fast-food chain releasing a bad chicken sandwich?
  • Legally-speaking, what’s the relationship between Dr. Frankenstein and the monster? Does the monster count as his son? Is the monster his dependent, for tax purposes? Could the monster theoretically inherit Frankenstein’s estate? Do the next-of-kin of the people whose graves Frankenstein robbed get part of the estate? Are they technically related to the monster?
  • Do you read Sutter Cane?
  • I’ve heard people make a big deal of the fact that, in The Thing (1982), an Antarctic research station has a flamethrower. Frankly, though, if I was stuck inside all day, facing months of darkness, and with access to a machine shop, a flamethrower is probably the first thing I’d build.
  • If vampires don’t show up in mirrors, what other weird optical properties do they have? Can they be recorded on film? What about digital image sensors? Can you X-ray a vampire? Are they transparent to neutrinos? Are they visible in the infra-red?
  • Have you read Peter Watts’s Blindsight? Because you probably should.
  • If the ancient Romans stole a valuable item from an ancient Egyptian tomb, and then a modern person stole that item from an ancient Roman crypt, would the person be cursed by the vengeful spirits of ancient Egypt and ancient Rome?
  • We already have sexy vampire costumes, sexy cat costumes, sexy cheerleader costumes, sexy police-officer costumes… Let’s expand! Sexy firefighters! Sexy elevator technicians! Sexy welders! Sexy coal miners! Sexy astronauts!
  • What if a werewolf moved to a colony on the Moon? When would they transform? And why hasn’t anybody made that movie yet?
  • Richard Matheson kind of beat me to this one, but: are vampires only repelled by crucifixes, or is it all religious symbols? Could you repel a vampire with a Star of David? With Islamic calligraphy? With a statute of Buddha? A carving of Mjölnir? A well-written essay on agnosticism?
  • Is it just the stab to the heart that kills the vampire, or does it absolutely have to be a wooden stake? Or could you just kill a vampire with an icepick or a knife or something?
  • What if you blew a vampire up with dynamite? Would that kill them permanently?
  • At what point in humanity’s evolutionary history did we become susceptible to vampirism? Were there vampire Homo habilis two million years ago? Can chimpanzees become vampires? Gorillas? Bonobos? Babboons?
  • You never see werewolves in wolf-form doing ordinary canine things. They’re always roaring and howling loping and eating people. You never see them sneezing or pooping or scratching their ears or eating grass for indigestion or sniffing people’s groins or doing that weird friendly face-biting thing that regular wolves do with each other.
  • How specific is a vampire’s sensitivity to garlic? Are they only repelled by Allium sativum, or could you repel them with shallots? Does it still work if the garlic is cooked? Could you use garlic salt?
  • What would’ve happened if the car in Christine ran out of gas on its way somewhere?
  • How come we never got our movie adaptation of The Long Walk? I was kinda looking forward to that.
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science, thought experiment

A Nugget of Electrons

A very long while ago, I mentioned in a post that it would probably be very bad news to collect all the electrons from a bucket of water and stick them together into a little nugget. And now, I’ve finally found the equations that will tell me exactly how bad an idea that would be.

But first, let’s specify just how much water we’re dealing with. Because I live in the United States, where we frown on convenient units of measurement, I’m going to be working with a five-gallon bucket (18.93 liters). That works out to 1,050 moles of water, or about 6.323e26 water molecules. Each water molecule contains two hydrogen atoms, contributing one electron each, and one oxygen atom, contributing eight. Therefore, we have ten electrons per molecule, or 6.323e27 electrons in five gallons of water. Each electron carries a charge of about -1.602e-19 Coulombs. So, how much energy would be required to squeeze that much charge into a sphere 1 centimeter in diameter? Fortunately, the equation for this isn’t as terrifying as I expected. It goes something like this

(1/(4 * pi * vacuum permittivity)) * (3/5) * ((total charge^2)/(radius)) [1]

Sticking the values we have into the ever-trusty WolframAlpha, we get 1.11e28 Joules. That’s in the neighborhood of one hundred thousand times the kinetic energy of the asteroid that caused the KT extinction, which killed all the non-avian dinosaurs.

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electronics, engineering, physics, science

Guide to Battery Sizes

D battery: 33.2 mm. in diameter x 61.5 mm. long. Minimum capacity (alkaline): 12,000 mAh

Was once commonly used in large flashlights, lanterns, and children’s toys.

C battery: 26.2 mm. in diameter x 50 mm. long. Minimum capacity (alkaline): 10,000 mAh

Was once commonly used in large and small flashlights and children’s toys.

B battery: 21.5 mm. in diameter x 60 mm. long. Minimum capacity (alkaline): 8,000 mAh

Used in the UK and the Russian Federation as the internal cells of 4.5-volt lantern batteries.

A battery: 17 mm. in diameter x 50 mm. long. Minimum capacity (alkaline): 4,900 mAh

Not commonly available as a primary (non-rechargeable) battery. Sometimes encountered as a rechargeable battery in battery packs.

AA battery: 14.5 mm. in diameter x 50.5 mm. long. Minimum capacity (alkaline): 1,800 mAh

Still in widespread use. Commonly available in alkaline, carbon-zinc, nickel-metal-hydride, and nickel-cadmium varieties. Used for small portable devices like flashlights and portable electronics.

AAA battery: 10.5 mm. in diameter x 44.5 mm. long. Minimum capacity (alkaline): 860 mAh

Still in widespread use. Commonly available in alkaline, zinc-carbon, nickel-metal-hydride, and nickel-cadmium varieties. Used for small portable devices like small flashlights, small portable electronics, and electronics with a low current draw.

AAAA battery: 8.3 mm. in diameter x 42.5 mm. long. Minimum capacity (alkaline): 500 mAh

Available, but not in common use. Used for slim-profile electronics such as laser pointers and penlights.

AAAAA battery: 7 mm. in diameter x 39.9 mm. long. Minimum capacity (alkaline): 330 mAh

Briefly considered for use in endoscopic surgical equipment in the early 1980s, because of its narrow profile, but rejected due to the risk of electrolyte leakage within patients.

AAAAAA battery: 5.6 mm. in diameter x 37.6 mm. long. Minimum capacity (alkaline): 190 mAh

Developed in the USSR in the mid-1970s, to be used as both the projectile and the power source for the guidance system in AK-48 cartridges. Saw limited mass-production, and continued to be used following the collapse of the USSR. Was rendered entirely obsolete by the development of the Zorg ZF-1 in 1997.

AAAAAAAAAA: 2.3 mm. in diameter x 29.5 mm. long. Minimum capacity (alkaline): 19 mAh

Showed promise powering ultra-portable and ingestible electronic devices. However, manufacturer Varta produced a battery in this size with the name shortened to A10, which resulted in a trademark dispute with Fairchild, manufacture of the A-10 “Warthog” attack aircraft, and caused Varta and other manufacturers to cease production out of fear of litigation.

AAAAAAAAAAAAAAA: 0.8 mm. in diameter x 21.8 mm. long. Minimum capacity (alkaline): 1 mAh

Not in common use, but favored by some for electric mechanical pencils, being about the same size as a pencil lead.

AAAAAAAAAAAAAAAAAAA: 0.31 mm. in diameter x 17.1 mm. long. Minimum capacity (alkaline): 0.11 mAh

Fell out of favor in the 1980s because it was frequently mistaken for a 30-gauge hypodermic needle. Was banned in the early 1990s after it was discovered teenagers were using them to inject themselves with intravenous POWER.

AAAAAAAAAAAAAAAAAAAAAAAAA: 0.085 mm. in diameter x 11.88 mm. long. Minimum capacity (alkaline): 0.00038 mAh

Were briefly considered for portable power applications in the 1980s, since they could easily be disguised as strands of hair, but were never mass-produced due to their low capacity.

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA: 0.0093 mm. in diameter x 6.48 mm. long. Minimum capacity (alkaline): 0.000013 mAh

Were briefly believed to be the power source for human cells, until the discovery of the mitochondrion in 1898.

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA: 0.001 mm. in diameter x 3.7 mm. long. Minimum capacity (alkaline): 0.00000000015 mAh

Were most likely first observed in 1943 in a bacterial mat from the northern part of the Dead Sea. Were misidentified as “funny-looking bacteria” until 2003.

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA: 0.000010 mm. diameter x 0.65 mm. long. Minimum capacity (alkaline): 0.00000000000049 mAh

Showed promise as a power source for ultraminiature cassette players in the 1980s, but fell out of favor due to its physical resemblance to particles of Ebola virus.

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA: 0.0000000054 mm. in diameter x 0.13 mm. long. Minimum capacity (alkaline): 0.000000000000000000001 mAh

An alkaline AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA battery manufactured by Panasonic held the world record for smallest alkaline battery from its introduction in 1990 until 2004. In 2004, it was discovered that the battery’s nominal diameter was smaller than that of a hydrogen atom, and its capacity was fifty times smaller than the fundamental charge of an electron. The battery was stricken from the record books for being “physically impossible”. Panasonic retired this battery size the following year.

This entire post is a work of fiction. Any resemblance to real persons or entities is coincidental.

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Uncategorized

“Mostly Empty Space”

We hear it all the time: “Atoms are mostly empty space.” Sometimes, that factoid is even quantified: “Atoms are X % empty space.” And as part of my ongoing mission to exorcise nagging questions spawned by third-grade science books, I want to find out what X actually is. How much of an atom is actually empty space?

Well, atoms are just a nucleus of protons (and sometimes neutrons), with electrons sort of vaguely existing in their vicinity. They don’t really orbit. Because quantum mechanics is weird and terrifying, you can think of an electron as being smeared out in a haze of existence around the nucleus. There’s a probability cloud surrounding the nucleus, and at each point within that cloud, the density of the cloud determines how likely the electron is to be hanging out there. Depending on the electron’s energy level in the atom, the probability cloud might be spherical or it might be dumbbell-shaped or it might be a bit like an onion. But the probability cloud is always blurry.

Which means that, in record time, we’ve hit a damn stumbling block. Here’s an irrelevant-looking picture:

(Generated via fooplot.com)

That’s the graph of the function exp(-x^2), which doesn’t have a lot to do with electrons or atoms, but is a simple analogy for the probability density in a spherical electron cloud. How wide would you say that bump is? 2 units? 4 units? Just like with swear words, no matter where the fuck you draw the line, somebody’s going to disagree with you. But sooner or later, you’ve gotta buckle down and decide that A is over the line and B isn’t. Luckily, science is built to be sensible and rigorous, so as long as we pick a defined point where the bump (or electron cloud) ends, and as long as we all work from the same definition (or tell each other if our definitions are different), we can at least have concrete numbers to work from.

So, to answer the question “How much of an atom is empty space?” I’m going to use the covalent radius for the atoms in question. This is the radius of the atom as deduced from how far it sits from other atoms when it forms covalent molecular bonds. There are other definitions that come closer to our intuitive idea of radius (van der Waals radius, for instance) but covalent radii are easier to measure, and are often known with higher precision.

So now we have a way to look up one parameter: the radius of an atom, and therefore, its volume. The smallest and least massive atom is hydrogen, with a radius of about 25 picometers (0.025 nanometers, or 20,000 times smaller than a bacterium). Hydrogen is a nice atom. It has one proton and one electron. That’s it. And the probability cloud for its single electron is a pleasant spherical shape (at least in the ground state). The largest atom is cesium, with a radius of 260 picometers (0.26 nanometers, about 2,000 times smaller than a bacterium). And the most massive naturally-occurring atom is (arguably) uranium, with a radius of 175 picometers. It’ll make sense why I included two different “largest” atoms in a moment.

To figure out what fraction of an atom is empty space, we need to know how much of it is not empty space. (The missile knows where it is because the missile knows where it isn’t…) Since I spent the start of this post talking about electrons (and since the answer is nice and simple), let’s ask the question: what’s the volume of an electron?

Well, as far as physics can tell (as of January 2021), the answer is zero. The electron has no substructure that we know of—it has no internal parts. There’s just this infinitesimal speck that has all the properties of an electron, and that’s as much as we know about them. Quantum physics and experimental evidence suggest an electron cannot be larger than 10-18 meters—if it were, that’d cause observable effects. So, for our purposes, electrons are so small they’re not worth including.

That only leaves the nucleus. And hoo boy, if you thought the weird fuzziness of the electron cloud was frustrating, you ain’t seen nothin’ yet.

Let’s start with hydrogen, since it’s nice and simple. One zero-volume electron just sort of weirdly hanging out, in an unpleasant blurry (but spherically-symmetric) fashion in the vicinity of a single proton. Unlike the electron, the proton does have a measurable radius. It’s still a fuzzy, blurry, jittery thing that you can never quite pin down, but if you shoot, say, electrons at it and see how they bounce off, you can get an idea, and from that data, decide that the most sensible radius for a proton is 0.877 femtometers. That’s 0.000877 picometers, or 0.877 millionths of a nanometer. If a proton were the size of a 100-micron-diameter dust speck (right on the limit of naked-eye visibility; roughly the diameter of a hair), then a hair would be almost half the diameter of the earth. Did I mention that protons are really small? ‘Cause they are.

So a hydrogen atom is about 25 picometers in radius, and the proton, which is the only thing in it that takes up any space, has a radius of about 0.877 femtometers. The formula for volume of a sphere gives us a simple answer for “How much of a hydrogen atom is empty space?” 99.99999999999568%.

You guys know me, though—that’s too abstract a number. Too many digits. Let’s take, say, the United States. The USA is a big country. If it were a hydrogen atom, the whole thing would be empty space, except for a single patch about 24 inches (72 centimeters) across. Just big enough for an adult human to stand in. You probably wouldn’t be able to see it with the naked eye from an airplane. (I know I switched from volume to area here, but I used the same percentage to get the “area” of the proton, so the comparison is still valid, mathematically.)

For heavier elements, life gets more complicated. As I said, electrons are impossible to pin down for certain. They just exist in the nucleus’s general vicinity. Their existence is smeared out in a particular way around the nucleus. (That’s not exactly an accurate description of how it works, but I don’t know enough quantum mechanics to take you any deeper without the risk of misleading you.) The same is true for the nucleus, but because the protons and neutrons in a nucleus are much more massive, and because they’re so close together, and because they experience an additional very strong force (the strong nuclear force) that the electron doesn’t, their jittering is even more intense.

As a result, we know about the radii of atomic nuclei in the same vague way we know about the radius of a proton: we shoot particles at the nuclei and see how they bounce off. Most will just graze and barely deflect at all. Some will hit the nucleus closer to head-on, and some will hit it square enough to come back at you. By plotting how often electrons bounce off and at what angles, for a given electron speed, we can build up a pretty convincing picture of where all the matter in the nucleus is.

The radius of an atomic nucleus is roughly 1.5 femtometers times the cube-root of the element’s atomic number (for elements with atomic numbers above 20). For cesium, the largest atom by covalent radius, the nucleus has a radius around 5.7 femtometers. A cesium atom has a covalent radius of about 260 picometers, and therefore, is 99.99999999999895% empty space. If the United States were a cesium atom, the nucleus would be barely the size of one and a half sheets of standard printer paper. And uranium, the largest atom we’re concerned with (by mass) has a covalent radius of 175 picometers with a nuclear radius of 6.8 femtometers. 99.9999999999941% empty space. Compared to the United States, that’d be a circle about 34 inches (86 cm) across. Big enough to sit in, but not lie in comfortably.

You guys know me. I usually like to finish my posts with some clever coda. Some moral for the story. But there’s really not one this time. This time, the question was “How much of an atom is empty space,” and the answer is…well, it’s right up above.

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physical experiment, real mad science, silly

Morbid Curiosity: Wolf Urine

Ugh…

Normally, I’m of the “Curiosity killed the cat, but satisfaction brought it back” school. Very rarely have I regretted learning something new about the world, even if that involved tasting fermented fish. Today, though, I’m regretting my curiosity.

You can buy all kinds of crazy shit on the Internet. Real dinosaur fossils. Uranium ore. People’s bathwater. Politician-shaped inflatable dolls. Truck Nutz. Just the other day, I saw an apothecary bottle on eBay which was supposedly full of horrendously toxic mercury bromide.

Now, usually, I’m pretty restrained about buying horrible stuff. Not this time, though. Not this time…

WolfPee

I am now the (proud?) owner of twelve fluid ounces of wolf piss. According to PredatorPee.com, they get their wolf piss from the drains under captive wolves’ enclosures. So that’s one burning question answered. Another question: why would anybody sell wolf piss? Well, supposedly, since it smells like an apex predator, wolf pee scares away most other animals, like cats, dogs, foxes, and coyotes. But another burning question still remains: what the hell is wrong with me? I’m gonna file that one under “beyond the scope of this article.”

Smells are pretty hard to describe in text, and my nose doesn’t work that well anyway, but to save you guys from your own morbid curiosity, I’m going to try to convey to you just what wolf pee smells like.

Horrible is what it smells like. It’s absolutely rank. For some reason, I had it in my head that wolf pee would smell like a very sweaty lumberjack. Musky and animalistic, maybe, but not horrible. I was incorrect. Wolf urine is one of the worst things I’ve ever smelled.

The first scent that hits the nose is the rancid stink of a stagnant, rotting mud puddle. If you played in mud as much as I did as a kid, you know what I’m talking about. A boggy, anaerobic smell. The smell of the liquid that seeps out of a pile of rabbit droppings that’s just starting to decompose, or a chicken coop that badly needs shoveling out.

The second impression I get is just how pungent the smell is. It’s a penetrating, shocking smell. The kind of smell usually associated with “What the hell did I just step in?” or “God, something died in here.” The second it hits the nose, it takes a fast-track right to the brain and bashes you over the head. It’s the kind of smell that would be absolutely impossible to ignore.

(I would like to take a moment to point out that, for each of these descriptions, I’m taking a fresh sniff, which I’m really, really, really starting to regret.)

There’s another component to the smell that I’m finding it difficult to describe. If you, like me, went to a public high school, you will have encountered the intense, skunky, musty, musky, herbal smell of cannabis. There are other plants that smell kinda like that. Tomato leaves. Some strains of hops. Skunk cabbage. Some kinds of grass clippings. That’s the tail-end smell.

So, in all, I’d say wolf pee smells like someone made a mud-pie out of rotting mud, with cannabis, tomato leaves, and grass clippings as a binder, burnt the edges of that mud-pie, and then let it soak in scummy pondwater for a couple days.

I’ve smelled some very nasty things in my time. Dead chickens in the heat of a Carolina summer. Wet, rotting soy protein. Roadkill. Improperly-disposed-of diapers. Dead fish. Surströmming. Mam ca loc. Axe body spray. Wolf piss is now a solid contender for the worst thing I’ve ever smelled. Perhaps it’s some sort of instinctive, primeval thing—a human who smells wolf and thinks “Gah! I’m outta here!” has a distinct survival advantage. Or perhaps I’m being trolled. I can’t say I’ve ever sniffed a wolf’s undercarriage (nor do I intend to start), so for all I know, I just bought a bottle of government-issue stink-bomb liquid.

But the longer I think about it, the more I’m sure: wolf urine is the worst thing I’ve ever smelled. I get genuinely queasy just remembering the odor. And I’m slightly worried that someone’s gonna smell what smells like rotting cannabis coming from my place and call the police. And I’m going to have to explain to a very confused officer that they’re just smelling my bottle of wolf piss, which is going to lead to some conversations I’m not looking forward to.

Did I say do not try this at home? ‘Cause you really, really shouldn’t. I wish I hadn’t.

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physics, short, silly, thought experiment

Late for Work

I work a pretty standard 9-to-5 job. Now I know 9 to 5 is actually pretty cushy hours. I’ve got friends whose hours are more like 6 AM to whenever-it’s-done. But my lizard brain won’t get the message that 9 AM isn’t that early a start. Apparently, my brain thinks that getting up at 8 AM is the same as getting up at 3:30 and having to walk ten miles to work (in the snow, uphill both ways).

Luckily, I really don’t like being late, so I manage to be on time by pure stubbornness. But sometimes, it’s a pretty close shave. And while I was driving to work the other day, I got to wondering just how late I could leave the house and have any chance of getting to work on time.

My commute to work is 23.1 miles (37.2 kilometers). According to Google Maps, it should take about 39 minutes, which seems about right. That means an average speed of 35.5 miles per hour (57.2 kilometers per hour). Considering at least half that distance is on the highway at 70 miles per hour (113 km/h), that seems a little slow, but to be honest, there are a lot of traffic lights and weird intersections in the non-highway section, so it probably works out.

But the question remains: how quickly could I possibly get to work? And, therefore, how late could I leave the house and still get to work on time?

The most obvious solution is to convert myself into a beam of light (for certain definitions of “most obvious”). Since there are no vacuum tunnels between here and work, I can’t travel at the full 299,793 kilometers per second that light travels in vacuum. I can only go 299,705. Tragic. Either way, by turning myself into a beam of light, I can get to work in 0.124 milliseconds. So as long as I’m dressed and ready by 8:59:59.999876 AM, I’ll be fine.

Of course, there’d be machinery involved in converting me to light and then back into matter again, and considering what a decent internet connection costs around here, it ain’t gonna be cheap to send that much data. So I should probably travel there as matter.

It’d make sense to fire myself out of some sort of cannon, or maybe catch a ride on an ICBM. The trouble is that I am more or less human, and even most trained humans can’t accelerate faster than 98.1 m/s^2 (10 g) for very long without becoming dead humans. I am not what you’d call a well-trained human. Sadly, I don’t have easy access to a centrifuge, so I don’t know my actual acceleration tolerance, but I’d put it in the region of 3 to 5 g: 29.43 to 49.05 m/s^2.

Figuring out how long it’ll take me to get to work with a constant acceleration is pretty simple. We’ll assume I hop in my ridiculous rocket, accelerate at 3 to 5 g until I reach the halfway point, then flip the rocket around and decelerate at the same pace until I arrive. And since the math for constant acceleration is fairly simple, we know that

distance traveled = (1/2) * acceleration * [duration of acceleration]^2

A little calculus tells us that

duration of acceleration = square root[(2 * distance traveled) / (acceleration)]

Of course, I have to divide distance traveled by two, since I’m only accelerating to the halfway point. And then double the result, because decelerating takes the same amount of time, at constant acceleration. So, at 3 g, I can get to work in 71.2 seconds (reaching a maximum speed of 1,048 meters per second, which is about the speed of a high-powered rifle bullet). So, as long as I’m inside my rocket and have the engines running by 8:58:48.8 AM, I’ll be at work exactly on time. Though after struggling with triple my usual body weight for a minute and twelve seconds, I’ll probably be even groggier than I usually am.

I have no idea if I can even physically tolerate 5 g of acceleration. I mean, I’m hardly in prime physical condition, but I’m not knocking on death’s door either. But I’m gonna venture to guess that anything above 5 g would probably kill me, or at least leave me needing a sick day by the time I actually got to work, which would defeat the whole point. At 5 g, I only need 55.06 seconds to get to work, reaching a maximum 1,350 m/s. So, if I’m in my rocket by 8:59:04.94, I’m golden!

Of course, that was assuming that, for some reason, I do all my accelerating along my usual route. And frankly, if you’ve got a rocket that can do 5 g for over a minute, and you’re not flying, you’re doing it wrong. According to an online calculator, the straight-line distance between home and work is 13.33 miles (21.46 km). Re-doing the math, at 3 g, I can make it to work in 38.18 seconds (meaning I can leave at 8:59:21.82 AM, and will reach 568.1 m/s). At 5 g, I’ll be there in 29.58 seconds (leaving at 8:59:30.42, reaching 936.4 meters per second).

And yet, no matter how quickly I can get to work, I’m still gonna wish I could’ve slept in.

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engineering, physical experiment, physics, short, silly

Crappy Plastic Bags

Plastic grocery bags suck, and for many reasons. They’re light enough to be carried away by a particularly motivated fruit fly, which means they turn into litter very easily. And since they shred easily into tiny, tiny pieces, they’re probably an excellent source of plastic pollution, which is looking more and more like a major problem every day.

Luckily, the flimsy grocery bags I’m talking about are made of LDPE: low-density polyethylene. And while LDPE isn’t exactly the kind of thing you wanna put on a sandwich, as far as plastics go, it’s relatively mild. Chemically, it’s very similar to wax. Unlike, say PVC and polystyrene, LDPE is a lot less prone to breaking down into scary aromatic and chlorinated hydrocarbons. Plus, it’s not full of the slightly scary plasticizers found in many other plastics.

But my real issue with grocery bags is that they suck. They’re pretty shitty at the one thing they’re made for, which is holding groceries. This morning, on my way to work, I stopped to get some milk. The jug couldn’t’ve weighed more than three or four pounds, but that didn’t stop it from bursting right through the bottom and falling on the floor. I realize I’m making myself sound like a cranky old man when I say this, but I don’t remember plastic bags being quite that fragile when I was younger. And I would’ve noticed if they were, on account of the number of times I tied a grocery bag to a string and tried to fly it like a kite. They didn’t last a long time doing that, but I’d be willing to wager the modern ones would rip before you could get the kite string tied on.

But I’m going to do what crotchety old men never seem to: I’m going to back up my whining with evidence. Here is my evidence.

Crappy Plastic Bag

I’m sorry for the godawful picture, but it gets the point across. What you’re looking at is a pair of lower-mid-range digital calipers, which are pretty handy for measuring things to decent accuracy and precision. The calipers are clamped down around a flat strip of grocery-bag material which has been folded three times, giving eight layers. In the name of fairness, let’s assume that the actual thickness is 0.095 millimeters: just barely thin enough that the calipers didn’t round it up to 0.1. Divide 0.095 by eight, and you get 0.011875 millimeters, or 11.875 microns. For comparison, a human hair is usually quoted in the neighborhood of between 80 and 120 microns. The one I just pulled out of my own scalp (you’re welcome) measured 50 microns. Measuring ten sheets of printer paper and dividing by ten gave me 102 microns. A dust mite turd is apparently between 5 and 20 microns. (Wikipedia says that this book says so, and while I’ll do a lot of things for my readers, I’m not reading a thousand pages to find a passage on dust mite poop.) Human cells usually range between 10 microns and 50 microns (though some get a lot larger).

To get some more perspective, an American football field is 150 yards long and 55 1/3 yards wide. If we were to cover an entire football field with a single layer of grocery bag material, the whole damn thing would only weigh 162.9 pounds (73.9 kilograms). That’s less than me. Less than the average American football player. Hell, that’s less than my dad, and he’s built like a lean twig. Imagining the horrendous suffocation hazard that sheet will pose when it inevitably blows into the stands is making me nervous.

Now, this is only one data point, admittedly. I didn’t measure the thickness of plastic bags when I was a kid (I was too busy making kites out of them, or walking around the house with a mirror pretending I was walking on the ceiling). But that seems excruciatingly thin to me. In order for a soap bubble to be iridescent, it must undergo thin-film interference. This means that, in order to reflect violet light (the shortest wavelength visible to the eye: around 380 nanometers), the bubble can be no thicker than 71 nanometers. My grocery bag is only 167 times thicker than a damned soap bubble. No wonder my groceries fell out this morning, and no wonder every time I go to the hardware store, something pokes a hole in the bag and makes my tools fall out.

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nuclear, physics, science

Drop and Run

Drop and Run

(Cheers to @lukeweston on Twitter, who wrote the post that inspired this one.)

Radiation therapy is a lifesaver, because, unfortunately, cancer still exists. And sometimes cancers grow in places doctors can’t reach without poking a hole in something important. (The brain and pancreas are good examples. Don’t poke holes in those.) Luckily, instead of going after the cancer with pointy sharp things, a doctor can instead shoot the tumor with a radiation gun. (It’s weird that that counts as lucky, but it does.) You put the patient on a table, aim the beam at the tumor, and swivel the beam around the patient with the tumor as its pivot point That way the rest of the body only gets the beam swept over it briefly. The tumor, on the other hand, at the center of the beam’s pivot, gets the radiation constantly, and it gets radiation poisoning and dies, sparing the healthy tissue around it.

All good so far. But how the hell do you build a radiation gun? Most modern clinics use x-ray beams. A lot are starting to adopt proton beams, which don’t do as much collateral damage, if you plan things right. A few specialist clinics use beams of neutrons or carbon ions. And some clinics use gamma rays. Gamma rays aren’t exactly easy to make, but some radioactive isotopes produce them when they decay. Cobalt-60 is one of those isotopes. Stick a little slug of cobalt-60 in a tube inside a big lead block, at the far end of a narrow hole. The lead stops most of the gamma rays. The hole lets the rest out as a narrow beam. When you don’t need gamma rays, you cover the hole with more lead. Done! Gamma-ray gun! Cool, eh?

Understandably, the security around these little cobalt death-pellets is pretty tight. But people make mistakes. Sometimes, radioactive sources get stolen. Or they go missing. Or a nation goes through a revolution or a civil war, and the authorities who’re supposed to keep track of the death-pellets get swallowed in a coup. Or the sources simply get forgotten about. That’s what happened in 1987 in Goiânia, Brazil: A scrapper broke into an abandoned radiotherapy clinic, stole a cesium-137 gamma-ray source without knowing what it was, and took it home. Eventually, somebody broke the source capsule open with a screwdriver and got lethal cesium-137 chloride powder everywhere. People handled it. People touched it and then ate. People slept in beds right next to the source capsule. Four people died, 249 people got exposed, and a whole fucking village had to be decontaminated. Gamma-therapy sources are not to be trifled with.

So, if for some reason you’re breaking into radiotherapy clinics (please don’t do that) and you come across an ominous steel capsule that says “Drop and Run” on it, then for the love of everything holy, drop it and run.

Drop and Run Cropped

(You thought I was kidding about the “Drop and Run” thing, didn’t you? I wasn’t. 3500 Curies of cobalt-60 is enough that, if you put that source capsule it in your pants pocket, you’d drop dead in fifteen minutes flat. We’re not even talking about a “slow, miserable, rot-from-the-inside death from radiation poisoning” kind of dead. We’re talking “dead this time tomorrow” dead. Source: this online calculator, assuming 3,500 Curies of Co-60 at an average distance of 1.5 meters, and a rapid-death dose of 30 Sieverts, which, for gamma rays, equals 30 Gray.)

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physics, science

The Moment a Nuke Goes Off

Nuclear weapons give me mixed feelings. On the one hand, I really like explosions and physics and crazy shit. But on the other hand, I don’t like that somebody thought “You know what the world needs? A bomb capable of ruining the shit of everybody in an entire city. And you know what we need? Like fifty thousand of the bastards, all in the hands of angry buggers that all have beef with each other.”

That aside, though, the physics of a nuclear explosion is pretty amazing. Especially when you consider that nuclear bombs were developed at a time when: there was no vaccine for polio, commercial airliners hadn’t been invented, the big brains in Framingham hadn’t even started to work out just what causes heart disease, and a computer needed one room for all the vacuum tubes and another for its air conditioning system.

There’s an absolutely awesome 1977 paper by Glasstone & Dolan that describes, in great detail, and from beginning to end, the things that happen when a nuke goes off. The paper’s also surprisingly readable. Even if you’re a little rusty on your physics, you can still learn a hell of a lot just by skimming it. That’s the mark of a good paper.

To me, the most shocking thing in that paper is just how quickly the actual nuclear explosion happens. But first, a little background. This is what the inside of an implosion-type fission bomb looks like (This is the type that was dropped on Nagasaki, and seems to be the fission device used in modern arsenals. Correct me if I’m wrong.)

Fat_Man_Internal_Components (1)

(Source.)

It looks complicated, but it’s really not. The red thing at the center is the plutonium-239 that actually does the exploding. The dark-gray thing surrounding it is a hollow sphere of uranium-238 (I’ll explain what that’s for in a second). The light-gray thing is an aluminum pusher (I’ll explain that in a second, too). And the peach-colored stuff is the explosive that sets the whole thing off. The yellow things it’s studded with are the detonators.

When the bomb is triggered, the detonators go off. Spherical detonation waves spread through the dark-peach explosives on the outside. When they hit the light-peach cones, the shape of those cones forms the thirty-two separate waves into one smooth, contracting sphere. That spherical implosion wave then passes into the dark-peach charges surrounding the aluminum pusher. So far, the process has taken roughly 30 microseconds.

When the implosion wave hits the pusher, it crushes the aluminum inward, generating remarkable pressures. This takes something like 10 microseconds.  The pusher’s job is to evenly transfer the implosion force to the core.

The imploding pusher then crushes the uranium tamper in roughly 15 microseconds. The tamper serves two purposes: it helps reflect the neutrons generated by the plutonium-239 (thanks to commenter Brian for the correction: I somehow wrote plutonium-238 here and in a bunch of other spots below), and, being such a dense, heavy metal, its inertia keeps the core from blowing itself apart too quickly, so more of it can fission.

Speaking of the core, a whole bunch of crazy shit is about to happen in there. Normally, I don’t think of metals as the sort of thing you can compress. But when you’ve got hundreds of kilos of high explosives all pointing inwards, you can compress anything. The core is a whopping 6.4 kilos of plutonium (14 pounds). That’s how much plutonium it takes to wreck an entire city. But just having 6.4 kilos of plutonium lying around isn’t that dangerous. (Relatively speaking.) 6.4 kilos is below plutonium’s critical mass. At least, it is at normal densities. That implosion wave, though, crushes the plutonium down much smaller, until it passes the critical limit by density alone. (There’s also a fancy polonium-210 initiator in the center, to make sure the core goes off when it’s supposed to, but this post is already getting too rambly…)

Once the plutonium passes its critical limit, things happen very quickly. Inevitably, a neutron will be emitted from an atom. That neutron will strike a Pu-239 nucleus and cause it to fission and release a couple more neutrons. Each of these neutrons sets off another Pu-239 nucleus, and bam! We’ve got the right conditions for an exponential chain reaction.

Still, from the outside, it doesn’t look like much has happened. It’s been approximately a hundred microseconds since the detonators detonated, but next to none of the plutonium’s fission energy has been released. Here’s a graph to explain why:

Nuclear Explosion

(Generated using the excellent fooplot.com)

Here, the x-axis represents time in nanoseconds. The y-axis represents the number of neutrons, expressed as a percentage of the number needed to release 21 kilotons-TNT of energy (the amount of energy released by the Fat Man bomb that destroyed Nagasaki). At time-zero, the neutron that initiates the chain reaction is released. And by time 240, all of the energy has been released. But the thing to notice is that it takes all of 50 nanoseconds for the vast, vast majority of the fissions to happen. That is to say, the plutonium core does all the fissioning it’s going to do–releases all of its energy–within 50 nanoseconds.

21 kilotons-TNT released over 50 nanoseconds is equivalent to a power of 1.757e21 Watts. That’s ten thousand times more power than the Earth receives from the sun. That’s roughly 5 millionths of a solar luminosity, which sounds small, until you realize that, for those 50 nanoseconds, a 14-pound lump of gray metal is producing 0.0005% as much power as an entire star.

The nuclear explosion happens so fast, in fact, that by the time it’s finished, the x-ray light released just as the chain reaction took off has only traveled 15 meters (about 49 feet). Everything happens so rapidly that the bomb’s components might as well be stationary. The casing might be starting to bulge outward from the detonation of the implosion device, and the bomb, while still bomb-shaped, is rapidly evaporating into plasma as hot as the core of the fucking sun. But even at those temperatures, the atoms in the bomb haven’t had time to move more than a couple centimeters. So, by the time the nuclear detonation has finished, the bomb and the surrounding air look something like this:

Fat Man End of Detonation.png

But perhaps the wildest thing of all is that we’re not limited to hypothetical renderings here. We actually know, thanks to the incomparable Harold Edgerton, exactly what those first moments of a nuclear explosion look like. Doc Edgerton developed the rapatronic camera, whose clever magneto-optic shutter is capable of opening and closing with an exposure time of as little as 10 nanoseconds. The results of Mr. Edgerton’s work speak for themselves:

Glowing Shot Cab

The thing above is the “shot cab” for a nuclear test. It’s a little shack on top of a tower, with a nuclear bomb inside. In this picture, the bomb has already gone off. Those white rectangles are actually the cab’s wall panels, being made to glow brightly by the scream of X-rays bombarding them. And those ominous-looking mushroom-shaped puffs are where the X-rays have just started to escape into the air and make a nuclear fireball. A moment (probably measured in nanoseconds) later, the fireball looks like this:

Very Early Fireball

I take my hat off to Mr. Edgerton for having the guts to say “Oh? You need a photograph of the first microsecond of a nuclear explosion? Yeah. I can probably make that happen.” (Incidentally, both those photos are taken from the paper “Photography of Early Stages of Nuclear Explosions”, by Edgerton himself, which is, regrettably, behind a fucking paywall. Grumble grumble.)

And, thanks to sonicbomb.com, we can see the evolution of one of these nightmare fireballs:

Hardtack_II

Progressing from left to right and top to bottom, we can see the shot cab glowing a little. Then glowing a lot. Then erupting in x-ray hellfire. And after that, just sort of turning into plasma, which things that close to a nuclear explosion tend to do.

Soon enough, this baby fireball evolves into a nightmarish jellyfish from the deepest pit in Hell:

Tumbler_Snapper_rope_tricks.jpg

(Source.)

The horrifying spikes emerging from the bottom of the fireball are caused by the so-called “rope-trick effect”: they’re the guy wires supporting the shot tower vaporizing and exploding under the onslaught of radiation from the explosion.

And soon enough (after about 16 milliseconds), the fireball swells into a monster like this:

Trinity_Test_Fireball_16ms.jpg

(Source. Note, this is the fireball from the Trinity test, humanity’s first-ever nuclear explosion.)

It’s worth noting that, at this point, 16 milliseconds after the bomb goes off, your retinas have barely had time to respond to the flash. In the roughly 75 to 100 milliseconds it takes the retinal signal to travel down the optic nerves and reach your brain, you are already being exposed to maximum thermal radiation. And after a typical human reaction time (something like 150 to 250 milliseconds), about the time it takes to consciously react to something, you’re probably already on fire.

So nuclear explosions are cool, and they’re awe-inspiring, but I must pose the question once again: who the hell saw the plans for these hell-bombs and thought “Yeah. That’s a thing that needs to exist. We need to have that nightmare hanging over humanity’s head forever! Let’s build one!”

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