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 with comments, suggestions or wacky cold fusion ideas. Cheers!

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

Jeans instability: The fancy-pants stuff behind every star.
“Jeans instability: The fancy-pants stuff behind every star.”

Science is hard. Most of it is obviously complicated and full of tongue-twisty words that exist only so some eggbrain jerkass can school you at Words with Friends. But it’s sneaky, too. Whenever some small bit of science seems simple and straightforward, there’s always something way harder and full of Greek-letter math lurking underneath. That’s how science gets you.

Take Jeans instability, for example.

Everything physicists tell you up front about Jeans instability makes perfect sense. You’ve got this lumpy stuff called Jeans mass, and a size called a Jeans radius. If the Jeans mass exerts too much pressure for a given Jeans radius, the system flies apart and the mass spreads all over.

We’ve all been there. Like an hour after after Thanksgiving dinner.

On the other hand, if the Jeans mass has too little pressure, then Jeans instability occurs and the system collapses in on itself.

Presumably in a little pile around your ankles. I can’t say I’ve personally had experience with this phenomenon. It sounds like one of those tragic Euro supermodel problems. Oh, those poor twiggy bitches.

All of this is well and good, until the physicists then tell you that none of this has anything to do with distressed Calvin Kleins, Levis 501s or high-waist super skinny Jordache denim jeggings — and is that last one actually a thing? Merciful Darwin help us all.

To physicists — who mostly wear plain, practical polyester pants, it turns out — Jeans instability is a whole other thing entirely. It’s a phenomenon named after British physicist Sir James Jeans — personal legwear preferences unspecified — and describes the conditions under which interstellar gas clouds collapse to form stars.

On the bright side, most of the above reasoning still holds true. If the outward pressure of the gas in a cloud of a given size is too great — because the gas is especially hot, for instance — then the pressure will overcome gravitational force, and gas will spill out everywhere.

Like I said, usually an hour after Thanksgiving dinner. That happened to me twelve years ago, and Grandma still won’t invite me back for holidays.

But if the gas is sufficiently cool, or the mass of the cloud unusually high for the space it’s in, then gravity wins out and the gas will collapse in on itself, eventually forming a discrete object called a protostar, and later a star. It’s the Jeans instability that predicts under what conditions this collapse will begin to occur.

(Presumably, it includes declining seconds on pumpkin pie. Again, I wouldn’t know. That would require a stronger cloud of gas than I.)

That’s the good news, in terms of simplicity. The bad news is, the original equation for Jeans instability has been found by later researchers to not be completely accurate for real-world predictions. Which might explain why people try to fit into pants two sizes too small. Also, that equation for Jeans instability looks like this:

And to get the Jeans mass, you apparently solve this gibberish:

And the Jeans radius — more often called Jeans length — comes out the back end of this beast here:

I don’t know what any of that means. I have trouble enough figuring out the right inseam to put in the form on the Wrangler website. What if the gas cloud is wearing a belt? Is there more instability if you acid wash first? And how do I convert the units for the gravitational constant into boot-cut?

I’m telling you. Science is hard.

Image sources: Thinking Sci-Fi (baby protostar), Tenderfooting (gobbledy-Scrabbledy-gook), Denimology (serious jeans instability), LukeHamby (jeans + ankles = jankles), Wikipedia (scary equations)

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· 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.

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

Gravitational lensing: mirror, mirror in the sky; show me what's behind this guy
“Gravitational lensing: mirror, mirror in the sky; show me what’s behind this guy.”

If you’ve ever sat behind a really tall person at a movie, then you know the infuriating problem of not being able to see something on the other side of a solid object. At the theater, you probably deal with this in the usual ways — hoping the heighty person slouches in their seat, or spontaneously loses six inches of height, or their head explodes like in that Scanners movie.

But astronomy tells us there’s another viable option, known as gravitational lensing. All you have to do is push the movie a few million light years away, and make that big fat head in front of you as dense as a ten-billion star galaxy.

It’s a little complicated. I’ll explain.

One of the (now-famous) predictions of Albert Einstein’s general theory of relativity is that space (really spacetime, but who’s counting?) is curved, and that hugely massive objects with lots of gravitational force will further warp that curving. So if a celestial light source — like, say, a quasar — lies behind an enormous gravitational well such as a galaxy, the light from the quasar would get curved around the galaxy and slingshot out the other side.

It might appear that the light source lies beside the big heavy thing in the way, because the light doesn’t bend all the way back to the middle. And if the source is directly behind the obstacle, the light could take more multiple paths around it — left, right, up, down, south by southwest — and appear more than once on our side. It could even form a full ring of light all around the object in the middle, weirdly indicating that the thing producing the light isn’t anywhere around the obstacle at all, but directly behind it.

I know, right? It’s spooky. Real call is coming from inside the house stuff.

Because Einstein described relativity, and was a generally awesome dude, the light rings caused by gravitational lensing are called “Einstein rings”. There are very few complete rings — caused by a massive energy source directly behind a star or galaxy — but hundreds of partial rings, multiple-image systems and other gravitational lensing events have been observed. One of the most impressive, called Einstein’s Cross — because, again, cool smart guy — consists of four “bent” images of a way-distant quasar curved around a still-way-distant-but-not-as-way-distant galaxy in between.

It’s like having a head in the way, but still seeing the movie in double-stereo-vision. Because astronomy makes everything better.

So what do you need to make gravitational lensing work? First, a source of some kind of energy. Many of the known ones work in visible light, but any kind of electromagnetic energy will do in a pinch. The universe isn’t picky.

The energy source has to be ridiculously strong, though, because you’ll need to see the signal from way far away. Not just from down the block, or from that window in your attic, either. Instead, from billions of light years away. Which is kind of a big deal.

Why so far? Because you then need to find an incredibly massive object to plop between you and the energy source to produce the gravitational lensing. A bowling ball isn’t going to do it. A star might, if it’s in precisely the right orientation. A whole galaxy of stars would be better. Or you could try Nicki Minaj’s ass. It’s big enough to attract most of the pop culture paparazzi into a close orbit, apparently. Maybe it could work; I don’t know.

The point is, you’ll only see gravitational lensing by throwing that hypermassive whatever between you and and the signal. And then you can watch that gravity well bend electromagnetic waves like Beckham, off a straight line and down to your eyes.

So maybe it won’t help you the next time you’re blocked at the movies. But gravitational lensing could show you a star behind another star some day. And really, isn’t that how the movie industry works in the first place?

Image sources: Cosmic Chatter (Einstein ring), Slate (big head at movie theater), Disease Prone (Scanners head), SlamXHype (rocket-powered Minaj)

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