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: Physics
What I’ve Learned:

Relativity: you can't choose your family, but you can pick your physics.
Relativity: you can’t choose your family, but you can pick your physics.

I’ve learned a little about the theory — actually, theories — of relativity.

(Obviously only “a little”; I’ve never learned a lot about anything.)

Of course, I got a little confused about the word “relativity”. Seeing as how it sounds like “relatives”, I initially thought the physics professor was talking about my family. The parallels are so strong, in fact, it took me three lectures to figure out the problem. Maybe your relatives are different. Judge for yourself:

First, there are two kinds. You’ve got “general” relativity, and then there’s relativity that’s… “special”. Like Aunt Eunice, who leaves her girdle by the table after family dinners. Or cousin Gene, whose clan has watched “A Christmas Story” several thousand too many times.

(Apparently, there’s now a new-ish thing called “doubly special relativity” or “extra-special relativity”. Some physicists must have talked to Nana after her three helpings of rum fruitcake.)

Just as families make no sense, neither do the two names for types of relativity. “General” relativity actually only covers one specific thing: gravity. I thought this meant the gravitation of parents and grandparents around you when you visit for Christmas, asking things like, “You’re not wearing that, are you?” And “When are you going to find a job?” And “Who ate all my damned fruitcake?

I found out later it was a different kind of gravitation, and apparently it doesn’t work the way Isaac Newton or anyone else thought it did. The way Einstein figured gravity led to some pretty oddball predictions about the universe: spacetime must be curved rather than consistent, gravity can slow time and bend light, and black holes could exist that suck up all matter and light nearby.

These were all pretty outlandish notions when they were hypothesized back in the early 20th century. But as we’ve sorted out ways to precisely measure and explore such things, they’ve all turned out to be real. Who’s loopy on fruitcake now, classical physicists?

Of course, that leaves “special” relativity to explain everything else — a common occurrence at my family’s holiday parties. If you want to hear what’s wrong with kids today, where you ought to put your money or how the “gubment” ought to be run, just pull up a chair (and a tall stiff eggnog) and listen to the “special” relatives dish out a dose of “wisdom”.

(Naturally, they know as much about these topics as I know about… well, science. Which is scary. I’m surprised most of them manage to put on their pants in the morning.)

As I’ve mentioned before, special relativity isn’t about such things, though. (Thank goodness.) Instead, it’s a description of how spacetime — the woven-together fabric of time and three-dimensional space — works, and how things we used to believe were fundamental actually change based on perspective. Like an event happening at the same time according to two people, but sometime else to an observer in relative motion. Time slows down and objects seem shorter, the faster they go. And the big one that ties mass and energy and the speed of light (squared) all together: E = mc2.

Physicists glommed onto special relativity soon after Einstein first proposed it in 1905, because it fit with certain experimental observations better than Newton’s old laws — and it was useful in the bizarro, whacked-out, very “special relative” worlds of nuclear physics and quantum mechanics. General relativity took longer, but finding black holes and pulsars and other weird cosmic schmutz it predicted helped to solidify it, too.

So relativity isn’t about relatives, really. But a lot of it is strange, much of it is “special”, and most of it is, like, a hundred years old. So it’s really not that different. And it’s all around us in the form of spacetime and gravitation, so keep an eye out for relativity at your family gatherings over the holidays.

Just watch out for Nana. She’s a mean fruitcake drunk.

Image sources: Science News (relativity clocks), Southern Belle View (the family that Ralphies together…), Daily Mail UK (drunk grandma), Sur Fisika (Einstein v. Newton)

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· Categories: Physics
What I’ve Learned:

Special relativity: out with the aether, in with the aother.
“Special relativity: out with the aether, in with the aother.”

On the heels of the holiday season, you may have recently witnessed instances of “special relativity”. Grandma’s secret-recipe fruitcake pucks. Your uncle’s uncomfortably falsetto rendition of “O Holy Night”. Cousin Lem’s drunken faceplant into a bowl of Christmas bisque.

Happily, that’s not the only sort of special relativity. One hundred and ten years ago, Albert Einstein (with a little help from his friends) developed a theory that explained the behavior of things that travel near the speed of light. Like New York City taxis, or Usain Bolt. Or, you know, light.

This theory was needed because by the late 1800s, scientists had figured out that their plain old regular-speed relativity — based on work by Galileo and Newton, among others — wasn’t always getting the job done. This old school theory, called Newtonian relativity or Galilean invariance, because see the previous sentence, sport, said there is an “absolute space” and an “absolute time”, in which everything happens. And by that time, it also included an “absolute reference frame”, a universally unique point of view from which electromagnetic wave properties like the speed of light could be accurately measured.

Problem was, experiments suggested that if that uniquely-accurate reference frame (known as the “aether”) existed, all measurements made in labs were consistently in agreement with it. In other words, all those labs were stationary with respect to this spatial frame of reference. Which would be super, if we didn’t know that the Earth is constantly swooping around the sun (and the sun around the Milky Way, and the Milky Way hurtling through the universe), so it’s not really “stationary” compared to anything but itself.

Einstein dropped this “aether” concept down the nearest aelevator shaft, and that was just the beginning. He also decided that space and time were two great tastes that taste greater together, and mushed them together into something called “spacetime”. And he said no matter how fast you’re going (or not), the speed of light will always look the same. That let a whole bunch of crazy — but later experimentally verified — cats out of the physics bag. For instance:

Under special relativity, two people moving at different speeds may watch the same event happen, but observe it occurring at different times. And not just because one of them has TiVo, either.

If you watch two clocks — one moving and one sitting still — the moving clock appear to go slower. (And if it’s moving while you’re sitting in your office at ten minutes til five on a Friday afternoon, it’ll appear to go reeeeeeeeally slow.)

Mass and energy are equivalent, as given in Einstein’s famous special relativistic equation, E = mc2. This is obvious to anyone who’s eaten a four-ounce chocolate eclair and felt the kajillion-calorie jolt to their metabolism as the mass is converted to energy… and then seen six pounds of flab appear on their ass as it converts back to mass.

(I don’t know why it gets bigger in the conversion. What am I, some wild-haired German genius math guy?)

Basically, Einstein’s special relativity theory made some predictions crazier than drunk old Cousin Lem on an eggnog bender, but they turned out to be true where Newtonian relativity did not. Either theory will get you through the day for normal stuff — but if you’re zooming around near the speed of light, then you’d damned well better listen to Einstein.

He may not be your relative. But believe me — he’s special.

Actual Science:
LiveScienceWhat is relativity?
American Museum of Natural HistorySpecial relativity
HowStuffWorksHow special relativity works
io9Get pelted every day with particles that confirm special relativity
The Physics ClassroomRelativistic length contraction

Image sources: QuickMeme (it’s all relativity), Telegraph (UK) (blurry Bolt), Food Navigator (food faceplant), London Evening Standard (an eclair and present danger)

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

Exosphere: It's where the innie space becomes an outie.
“Exosphere: It’s where the innie space becomes an outie.”

The earth’s atmosphere is sort of like a family. Everybody stays pretty close… but some stay closer than others. So the troposphere, the nearest layer, is like that aunt who comes over every weekend you can’t get rid of. The mesosphere, you maybe see at holidays, and it sends you stupid-looking sweaters for Christmas.

Or pictures of itself in stupid-looking sweaters. The mesosphere’s side of the family was always a little weird.

But the exosphere? No. The exosphere is the black sheep of the atmospheric family — and it likes it that way. You might get the exosphere to RSVP “NO!” to a family reunion, but that’s about it.

In planetary (as opposed to familial) terms, the exosphere is the outermost layer of influence, where individual molecules are still bound by gravity, but there’s nothing you could call an “atmosphere” to be found. Around Earth, the exosphere contains hydrogen, with a little bit of helium, carbon dioxide and oxygen flitting around. But not in a crowded way. It’s less “Times Square at rush hour”, and more “fans at a Miami Marlins baseball game”.

The spot where the exosphere begins is called the thermopause. That might sound like a fancy name for “hot flashes” — and if you happen to be a planet, that’s not too far from the truth. The thermopause marks the boundary of the Earth’s energy system, and the exosphere doesn’t have enough molecular oomph to be part of that.

Of course, the planet has good and bad days, just like the rest of us. So on a high-energy day — maybe it’s summer, or the sun is flaring, or Earth got its ass out of bed early for yoga — the exosphere might start six hundred miles or more above the surface. On days with less energy — Sundays, I’m assuming, and the day after Thanksgiving — the exosphere might start half that high, around three hundred miles up. Some days it’s just harder to push yourself up against outer space, you know?

Where the exosphere ends depends on how you feel about outer space. Or at least how you feel about defining it. If you prefer your outer space to start where the radiation from earth ends — light, heat, the glow from Ryan Seacrest’s front teeth, all of that — then your exosphere ends six thousand miles above the earth, give or take a few hundred miles.

If you want to be all technical about it, and consider where the gravitational pull of the earth on atoms of hydrogen gives way to radiation pressure from the sun, letting those atoms escape out into the ether, that’s a different story. That happens a wee bit further out — say, a hundred and twenty thousand miles up the chute. Or halfway to the moon, if we’re getting other celestial objects involved now.

Speaking of which, other globs of space rock — including our moon — have exospheres, though at lot of them don’t have much of anything else. So an exosphere is sort of the bare minimum possible, in lieu of something more substantial.

Kind of like Ryan Seacrest, apart from his teeth — or the stands at a Marlins game. Neat.

Actual Science:
Universe TodayExosphere
University Cooperation for Atmospheric ResearchExosphere – overview
Science DailyHow the moon gets its exosphere
CBS NewsNASA moon mission targets lunar dust, “exosphere”
University College LondonDione’s thin oxygen exosphere

Image sources: Surfline (atmospheric layers), (Christmas sweater), Buzzfeed (Marlins fans [both of them]), The Richest (Tom Cruise’s shiny, angry, shiny teeth)

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