Note (12/2015): Hi there! I'm taking some time off here to focus on other projects for a bit. As of October 2016, those other projects include a science book series for kids titled Things That Make You Go Yuck! -- available at Barnes and Noble, Amazon and (hopefully) a bookstore near you!

Co-author Jenn Dlugos and I are also doing some extremely ridiculous things over at Drinkstorm Studios, including our award-winning webseries, Magicland.

There are also a full 100 posts right here in the archives, and feel free to drop me a line at secondhandscience@gmail.com with comments, suggestions or wacky cold fusion ideas. Cheers!

X-Linked Inheritance


· Categories: Biology, Genetics
What I’ve Learned:

X-linked inheritance: sometimes chromosomes aren't X-actly as they should be.
“X-linked inheritance: sometimes chromosomes aren’t X-actly as they should be.”

We humans have a bunch of chromosomes — balled-up tangles of DNA — lying around our cells. Forty-six of them, in fact, in twenty-three pairs. We get one chromosome of each pair comes from our mother and one from our father — though they may smush together and intermingle during the fertilization process.

(That’s the chromosomes, not our parents. They smushed and intermingled right before the fertilization process, obviously. Also, Barry White was probably involved, which you don’t typically find at the chromosomal level.

Most DNA strands are more into Marvin Gaye.)

The last chromosome pair — the “sex chromosomes” — is special. Males get one copy each of an “X” chromosome and a “Y” chromosome. And females double up on “X” chromosomes, leaving out “Y” altogether.

(The chromosomes get those names because under a microscope, they look a little like the alphabet letters.

To whom, I don’t know. Maybe Elmo from Sesame Street is in charge of naming biological structures.)

Put another way, if a fertilized egg gets the “Y” chromosome from the father (and one of the mother’s “X” chromosomes), the child will be male. If it gets the father’s “X” (and a second “X” from the mother), it’ll be female. Genes on these chromosomes will kick in during development, to determine the sex of the child.

(That’s how it works in humans, anyway, and most other mammals. Some animals have different sex chromosomes — like chickens, where hens have ZW and roosters are ZZ. Or grasshoppers, where females get XX and males get one X, nothing else, and are told to suck it up and stop whining.

Or platypuses, which have ten sex chromosomes, because of course they do. Platypuses are freaking weird.)

The XX versus XY choice has consequences down the line. Many genetic traits are “recessive”, meaning if just one of your two chromosomal copies is defective, you’re fine. Only if both are screwy will you have the trait or disease. For genes on, say, chromosome 3 or 12, that’s okay — everyone’s got two copies, so it’s rare to get both mucked up at once.

But X chromosome genes are trickier. Males only get one copy of X — from their mothers, remember, because to even be male, they had to get a Y from their fathers. If a gene on that lonely X chromosome happens to be horked up, they’re out of luck. There’s no backup, no “chromosome on the cloud” or flash-drive file to recover. One X chromosome, one chance to get all of “X-linked inheritance” right.

Sometimes, it doesn’t happen. If a recessive trait is X-linked and the father has a wonky copy, his daughters will all inherit it — but one bad copy doesn’t hurt. They’ll still get a “normal” X from Mom, and hopscotch happily away. If the mother is affected, all her kids have a 50% chance of catching the bad copy — but again, in girls, it’s covered by a healthy X (this time, from Dad). Only the sons, with mother’s lone mangled chromosome, get dinged by recessive X-linked inheritance.

(Daughters can also get the diseases. But it takes both an affected father and mother — and a bit of bad luck — to be so dinged. It’s like the sperm and egg walked a black cat under a ladder or something.

There’s also “dominant” X-linked inheritance, where even a single defective copy of a gene causes a disease. Females are more likely than males to inherit these conditions, but they’re pretty rare. Overall, X-linked torpedoes still sink males more often.)

So what issues can X-linked inheritance cause? Common recessive disorders include hemophilia, color blindness and certain types of muscular dystrophy. And the rarer stuff includes even nastier syndromes and diseases you wouldn’t wish on your worst newly-fertilized enemy.

So however many X’s you happen to have, be happy that the dice of X-linked inheritance probability didn’t roll snake eyes for you. Unless they did, and then curse the cocked-up chromosomes that combined to mark the mutant-X spot. If only you’d been a platypus, this might not have happened.

Something much weirder, probably. But not this.

Actual Science:
Medline Plus – Sex-linked recessive
NCBI – An introduction to genetic analysis / human genetics
Science Primer – X-linked inheritance
NHS UK – X-linked conditions
Wellcome Trust – X-linked diseases

Image sources: Madical School (X-linked inheritance), AllMusic (White ‘n’ Gaye), Aussie Pete II (Elmo [and Norah Jones!] and Y), Try Nerdy (platypus sex [chromosome] appeal)

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Faraday Cage


· Categories: Physics
What I’ve Learned:

Faraday cage: If you can't keep your wavelength in your pants, keep it in your Faraday.
“Faraday cage: If you can’t keep your wavelength in your pants, keep it in your Faraday.”

They say too much of anything can be bad. Sunshine. Children. Tribbles. Jalapeno chili dogs, probably, though I frankly can’t imagine how.

Too much electromagnetic radiation can be a problem, too. Whether in the form of a devastating lightning strike, a searing high-voltage current or dangerously delicious microwaves, some sorts of electricity you don’t want zapping through you. Because it might sting. Or leave a hole.

When you need to avoid catastrophically harmful electric charges, you have a couple of options. You could train really hard to get fast enough to outrun electromagnetic waves. But they move at the speed of light — since light is an electromagnetic wave, after all — so that’s probably slightly impossible. You could swap yourself out with someone who doesn’t mind going through life extra-crispy. Or you could climb into a Faraday cage.

Let’s walk through that last option. It seems the easiest. Also the least murdery.

To climb into a Faraday cage, you’ll first need to build a Faraday cage. Or buy one; maybe somebody on Etsy sells them. What you’re looking for is an enclosure made of some material that conducts material, like metal. The cage can be solid or made of mesh, so long as the holes in the mesh are smaller than the wavelengths of radiation you’re trying to keep out. Make your mesh-holes too big, and you’ll still get cooked; you’ll just get cooked in an interesting pattern. Like a steak with crosshatch grill marks, or a sunbather with “friends” who drew on his back in Coppertone.

Faraday cages work by distributing electrical charge around the structure. Since the whole cage conducts the charge, a constant voltage is created all around. Electrons in the conducting material crowd to one side or the other, effectively cancelling the electrical field zapped in. Anything (or anyone) inside the cage is protected, as there’s no voltage differential in there to generate electrical current.

The contraption is named for British physicist Michael Faraday, who conducted experiments back in the mid-1800s to prove that cages work for protection. We’re not sure if he started with cages, but since you don’t see any Faraday aquariums or Faraday litter boxes around, it’s safe to say that cages probably worked the best.

There are lots of scientific uses for Faraday cages; any time it’s useful to block an electromagnetic signal of some kind, the cage comes to the rescue. They’re used to protect computer equipment — and also car and airplane passengers — from lightning strikes and electric surges, to eliminate electromagnetic interference from sensitive tests (including MRI readouts) and to screen electrical cables from outside signals.

In less-than-scientific applications, Faraday cages have been used to keep people from electronically spying on pope-picking sessions at the Vatican, by shoplifters to block RFID signals on swiped merchandise and by thousands of doomsday preppers, paranoids and conspiracy wingdoodles to line their wallets, bomb shelters and tinfoil hats, so “the gummint” can’t track them, read their thoughts or steal their secret varmint gumbo recipes.

(Or maybe it’s the aliens they protect against. Or the Illuminati. Hell, it could be the chili dogs. Whatever.)

Also, since Faraday cages can dissipate signals that originate inside the box as well as outside, they’re very useful for shielding potentially harmful electromagnetic energy sources. Like an electrical power plant or microwave ovens or Jamie Foxx in that Spider-Man sequel, maybe.

(Maybe a Faraday cage wouldn’t hold Electro. But electrical line workers do wear “Faraday suits”, which are modified cages that keep them from getting shocks while working on high-voltage lines.

So if Foxx’s character had just worn the proper safety equipment, nobody would’ve had to sit through that hodgepodge of nonsense for two hours.)

Anyway, Faraday cages are pretty simple, really useful and great for keeping nasty electromagnetic waves away from tender vulnerable computers, equipment and humans. And those gumbo recipes. I’m sure those were exactly what Michael Faraday had in mind.

Actual Science:
National High Magnetic Field Laboratory – Faraday cage
CNet – This 30-foot-tall spiked Faraday cage helps satellites thrive
Computer World – Faraday cages
Popular Science – The Sistine Chapel is getting a high-tech bug-proofing with a Faraday cage
The Weather Channel – What happens when lightning hits your car? Here’s how to stay safe

Image sources: Life on the Blue Highways (Faraday cage demo), Drop the Beat on It (sucky sucky sunburn), The Telecom Blog (tinfoil Bart), Coop on the Scoop (Electro, crackling)

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Mitochondrial Eve


· Categories: Biology, Genetics
What I’ve Learned:

Mitochondrial Eve: Making DNA from an ooooooold family recipe.
“Mitochondrial Eve: Making DNA from an ooooooold family recipe.”

Imagine your DNA is a brown bag lunch. Your parents packed it with everything you need. A banana, if you like those. PB&J, maybe — unless your particular DNA makes you allergic to peanuts, in which case, I don’t know. Pizza? Fish heads? Who am I, Andrew freaking Zimmern?

The point is, your DNA comes from both your parents, in more or less equal amounts, and it’s stored in each of your body’s cells in something called a nucleus. That’s the bag in this analogy. Or the kick-ass Tardis lunch box, if you prefer.

Anyway, as she often does, your mother left you a little something extra.

But instead of a “love you” note or an extra Twinkie, our moms gave us something else: a bonus stretch of DNA, passed down only from mothers to children. This DNA is housed in a separate subcellular sack called a mitochondrion. Mitochondria do some pretty amazing things, but that’s a whole other bucket of lunches, so let’s stick to the DNA.

Because mitochondrial DNA is passed straight from mother to child, it can be traced back to earlier generations. Variations in DNA occur at a steady rate, and these get passed down, too. By comparing mitochondrial sequences between individuals, scientists can estimate how closely related they are — the more variations they share, the closer they are. If their DNA variations don’t overlap, it indicates they’re swinging on different branches of the old family tree. When a branch diverges enough to represent a unique DNA signature, it’s called a “haplotype” — a pattern of DNA variation shared by all the members of that branch.

Back in the 1980s, scientists tested mitochondrial DNA from more than one hundred people from different populations and found something unexpected: the variations between subjects suggested that they were all related, anthropologically speaking, by a common female ancestor who’d passed her mitochondrial DNA down the line. The research suggested that everyone in the entire human race shares the same great-great-great-lots-and-lots-more-greats grandmother. And we’re all rocking gently-used, slightly-mutated versions of her mitochondrial DNA.

This ancestral individual is technically called our matrilinear most recent common ancestor, or MRCA, but is more informally known as “mitochondrial Eve”; her maternal genetic makeup is represented in all of our DNA. She’s also been described as the “lucky mother”, since she wasn’t the only woman walking around and having babies at the time. Rather, her lineage — including mothers having daughters, since mitochondrial DNA is only passed by mothers, remember — is unbroken through history, while other childbearing ladies of the time had only sons, or no children, or their daughters didn’t produce more daughters down the line.

The idea of mitochondrial Eve shook science to its lunchtime Twinkies, because it implies a couple of things about human history. First, there was a time (or several) when our population must have been very small, maybe on the verge of extinction. For only one woman’s genetic imprint to have survived, rather than many, suggests there weren’t a whole bunch of humans running around the planet already, with haplotypes of their own. Our species went through some rough times, and only one branch of the tree survived.

The DNA also tells us roughly when this mitochondrial Eve existed. Based on the variability between contemporary humans’ DNA and the rate at which DNA glitches occur, mitochondrial Eve probably lived around 100,000 to 150,000 years ago. And since other evidence suggests that early humans didn’t migrate from Africa until about 95,000 years ago, our ur-granny most likely lived there. And cooked up some nice bits of DNA we’re still using today.

(For the record, we can also trace an “ultimate grandpa” via male lineages and the men-only Y chromosome. The “Y-chromosome Adam” may have lived around the same time as, or tens of thousands of years before, mitochondrial Eve. Their DNA’s early paths are completely independent.)

So next time you’re eating a sack lunch, root around in the bottom a little. Not only might you find a nice note — or a delicious snack cake — but you might discover some 100,000-year-old genetic material, courtesy of mitochondrial Eve. DNA appetit.

Actual Science:
io9 – How mitochondrial Eve connected all humanity and rewrote human evolution
How Stuff Works – Are we all descended from a common female ancestor?
LiveScience – Genetic Adam and Eve uncovered
New Scientist – Found: closest link to Eve, our universal ancestor
Nature – Genetic Adam and Eve did not live too far apart in time

Image sources: Alvin’s Enviro Blog (mitochondrial Eve map), Sierra Club (fishy Zimmern), ThinkGeek (Tardis lunchbox), PlanetKris (mitochondrial mom joke)

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Orbital Decay


· Categories: Astronomy, Physics
What I’ve Learned:

Orbital decay: Life's a drag, and then you burn. Or worse.
“Orbital decay: Life’s a drag, and then you burn. Or worse.”

Gravity is scary. Like, horror movie monster scary.

Think about it; gravity is relentless. Just when you think you’ve lost it, there’s gravity behind you, shaking its chainsaw or hockey mask or Lee Press-On fingerblades at you. And it’s sneaky; even if you make it to the abandoned cabin where the lights don’t work and the caretaker killed a busload of nuns exactly fifty years ago tonight, gravity will be inside, lurking in the shadows. You can hide under the covers, but gravity is already under the bed.

Face it — you’ll never escape gravity. If it weren’t the earth yanking you down, it’d be the sun or Jupiter or a rogue black hole. The pull is inevitable, like iron toward a magnet. Or Paula Deen toward butter.

But you can reach a truce with gravity — temporarily. With just the right velocity, your momentum will exactly counteract the force of gravity toward, say, the planet below. You don’t fly away, and gravity doesn’t splat you onto Earth; instead, you achieve a “stable orbit” and circle around and around.

But like Jenga towers and Facebook relationships, things aren’t really as “stable” as they seem. The truce falls apart over time, leading to something called orbital decay. Gravity wins, and the orbiter takes a nose-dive toward the orbitee.

When orbital decay happens to artificial satellites — like space station Mir or the Hubble telescope — one of two things comes next: some space scientist will push the satellite further up to counteract gravity, or it will plummet toward Earth, incinerating (we hope) in the atmosphere on the way down.

Other bodies experience orbital decay, too. Moons, for instance, can get sucked into their planets and destroyed; no Death Star laser beam required. Stars collide, and really wish they hadn’t. Even galaxies and black holes, circling for millions of years, can eventually experience orbital decay and smush each other stupid.

So what causes orbital decay? And why can’t we have nice things, cosmically speaking?

A few reasons. The balance between “orbiting” and “plunging toward destruction” is precarious; the slightest nudge can throw it off. Near a planet like Earth, tiny molecules of gas making up the sorry excuse for a high-altitude atmosphere will do it.

Satellites plow through these specks of gas, no problem — but they do get slowed down, infinitesimally. Those orbital brake-taps add up, and eventually cause a slight drop in altitude — down to where the atmosphere’s thicker, which leads to more slowing, and further dropping, and so on. It’s a vicious spiral, ending with a satellite faceplant from ten thousand miles high.

But there’s more than one way to decay an orbit. A lumpy orbitee, for instance — if the mass of a planet or star isn’t distributed consistently, orbiting bodies will get whanged around by the irregularities until they finally cut loose. And if the orbiter is large enough, it can bring this fate on itself by creating tidal forces on the larger body that squeeze it out of shape.

(This is why most satellites take spin classes, just to stay trim.)

Really huge orbiters have another problem: gravitational radiation. When supermassive objects like neutron stars orbit each other, Einstein’s general relativity theory predicts that gravitational energy waves streaming away from them should cause orbital decay over time. In recent years, astronomers have found binary stellar systems that appear to behave just the way predicted by the theory, which some didn’t expect. Even dead for sixty years, Einstein’s still smarter than a lot of physicists. But even he couldn’t escape gravity.

And neither can you; even if you negotiate with it, gravity has friends who will sneak up and kneecap you, just so gravity can finish you off. It’s like Freddy Krueger, backed by gremlins. Or Chucky with a nest of facehugging aliens. Or Jason Voorhees with a horde of zombie henchmen. And that’ll put the “decay” in your “orbital decay”, let me tell you.

Actual Science:
Medium / Starts with a Bang! – Ask Ethan #43: decaying gravitational orbits
Space.com – Phobos: facts about the doomed Martian moon
Universe Today – Workaholic Hubble telescope will eventually burn to death
Gizmag – NASA tests parachute-like space brakes to de-orbit satellites
Science Daily – Einstein’s gravity theory passes toughest test yet

Image sources: A-Level Physics Tutor (orbital decay), Houston Press (Paula Deen, butterface), Me and My Bread Knife (Facebook relationships), PsychoBabyOnline (Jason with machete, no zombies)

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Glial Cells


· Categories: Biology
What I’ve Learned:

Glial cells: you're gonna think lightning; you're gonna cogitate thunder!
“Glial cells: you’re gonna think lightning; you’re gonna cogitate thunder!”

We can’t all be the star of the show.

Think about it — sports tournaments don’t nominate Most Valuable Plethora. Only one actor in a movie gets to be the headliner, pretty much by definition. And no matter how smart those “meddling kids” are, it’s still the Scooby Doo show.

(And don’t you forget it, Fred, ya scarf-wearing frat-boy bossypants.)

Still, there’s nothing wrong with working in the background. Playing cheerleader for the star. (But not head cheerleader, of course.) Being the best darn supporting actor you can be. That’s true everywhere in life — even in our own brains. Most people think of their skulls being filled — or mostly filled, in some cases — with neurons, the cells we use to think and add and learn and compose bawdy limericks about buckets.

But that’s not quite true. Actually, our headbones are only half — or mostly-half — full of neurons. The other half are filled with something called glial cells, which are not neurons, but do help the neurons do their various jobs. And sometimes more.

Consider Rocky Balboa.

(I know. Not a name often associated with matters of the brain, for good reason. But stick with me here; I can make this work.)

Rocky was, of course, the star of the Rocky movies. Sure, he’d get his bloodied butt handed to him for a while by Ivan Drago or Mr. T. or that shifty CIA dude from Predator, but then he’d train up, grunt some stuff and punch them stupid. So it’s his name on the marquees.

But he didn’t do it alone. His trainer Mickey was there to help him — keep him on track, give him advice and yell gibberish at him every once in a while.

That’s what the glial cells in the brain do, more or less, for their diva neurons. First, the glial cells provide physical support and structure. You can’t box on a playground; you need a gym. So the glial cells make the gym our neurons work out in.

And some types of glial cells wrap around neurons, leaving something called a “myelin sheath” behind. This is like strapping the gloves and shoes onto a boxer — the myelin makes neurons quicker and more efficient. Real float-like-a-butterfly stuff.

But that’s only the beginning; glial cells also provide nutrients for neurons. I don’t know what kind, exactly — oxygen, probably, and vitamins; maybe a glassful of raw eggs on heavy logic days? That sounds right.

Another thing glial cells are important for is keeping neurons away from each other. Like professional fighters — especially Hollywood movie professional fighters — neurons like to get in each others’ faces. Or synapses, I guess. But the point is, they’ll talk trash at each other — unless the glial cells get in there and keep them apart. Because you’ve got to save all that cerebral violence for the ring. Or the SATs.

And there’s more; glial cells help neurons by keeping out distractions. Like infections, for instance. Or dead cells. Sleazy fight promoters. Talia Shire, maybe; I don’t know who’s banging around in your head. But whatever butts in, the glial cells boot it out, so the stars can shine. Sting like a bee, baby.

And just like Mickey — a former fighter himself — there’s evidence that some glial cells might even do their own mental “boxing” in the form of releasing transmitters, just like neurons. Not bad for a few billion has-beens and some never-weres, eh?

So the next time you’re thinking about thinking, or anything brains do, give a nod to the glial cells. Neurons are great and all, but without their glia, they’d be a bunch of bums. Bums, Rock! Bums!!

Actual Science:
Network Glia – Glial cells
Science Daily – Neurons listen to glial cells
NPR – To make mice smarter, add a few human brain cells
Scientific American – Know your neurons: what is the ratio of glia to neurons in the brain?
KurzweilAI – More than glue: glia cells found to regulate synapses

Image sources: The MedSchool Project (glial cell), Real Truth About Life… (frowny-faced Fred), Robakers (Mickey lightning, Mickey thunder), Monster’s Movie Mayhem (Rocky on top)

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