Resonant Cavity Thrusters

EmDrive. Q drive. Cannae drive. All of these are a class of devices known as resonant cavity thrusters, and for the past few years they’ve been popping up in the media from time to time.

What’s the big idea?

Take an ordinary household magnetron (you’ll find one in every microwave oven). Use it to pump microwave radiation into a resonant chamber of a certain shape (a metal box that’s wide at one end and narrow at the other.)

Turn it on and voilà: even though nothing is emitted from the system, you’ll detect a very small anomalous force pushing the chamber.

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Smarter Cars

It’s the year 2015… a year that seemed to be the distant future when I was a kid. We partied like it’s 1999. We survived The End Of The World As We Know It™ in 2000. We made it!

We’re living in the future! We have smart phones, smart TVs, smart appliances. So… why hasn’t my car smartened up?

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Yocto- to Yotta-

Years ago, when I was a young American engineering student, I was taught to believe that the metric system is some kinda filthy hippie Euro-commie anti-freedom plot. Sorta like water fluoridation, the JFK assassination, and Crocs.

One thing I always liked about the metric system (or technically SI, the Système International d'Unités) was its usage of prefixes to scale its base units up or down. The addition of a simple prefix can scale the base meter down to a millimeter or up to a kilometer.

I spell it as meter rather than metre because… well… America.

But prefixes have their limits, which is why God invented scientific notation. (Ok, scientific notation was probably developed by a person, but Google wouldn’t give me a name.) So what are the limits of the metric prefixes?

The smallest accepted metric prefix is yocto-, which is a scaling by 10-24. A yoctometer is a pretty small distance. It’s nine orders of magnitude smaller than a proton, and unless you’re a particle physicist, you probably don’t consider a proton to be huge.

On the other hand, a yoctometer is still a hundred billion times larger than the Planck length, the scale where a theory of quantum gravity becomes necessary. The SI system would need four more prefixes to get down to this scale.

And yes, “SI system” is as redundant as “PIN number” and “ATM machine”.

At the opposite end of the scale is the yotta- prefix, which is a scaling by 1024. Forget stars, galaxies, and galaxy clusters: a yottameter is about the radius of an entire supercluster of galaxies. That’s a whole yotta meters.

I apologize for that lame pun.

On the other hand, (how many other hands do I have, anyway?) the universe is very, very, very, very, very big. How big? Possibly infinite. I can’t think of anything bigger than that.

How about a distance that’s pretty big, but not infinite? If (among other assumptions) the universe is infinite, then by traveling far enough, you would eventually come upon a region of space identical to our own observable universe. This is similar to the Poincaré recurrence theorem, but for space rather than time.

So how far would you need to travel? 10^10^115 meters. There’s no metric prefix remotely close to this number: it dwarfs the number of grains of sands in all the beaches, and all the atoms in the entire observable universe. You won’t get there anytime soon.

And there you have it. Yocto and yotta: two prefixes that allow the humble meter to remain relevant from scales smaller than subatomic particles, to scales larger than galactic superclusters.


Today’s A-to-Z Challenge is brought to you by the letter W.  W is for Wireless.

Today, the term wireless conjures up thoughts of smartphones, tablets, Bluetooth headsets, and the IEEE 802.11a/b/g/n/ac protocol. Wireless is the technology that lets us live our lives unburdened by a tangle of ethernet cables and curly telephone cords.

Wireless freed us from the tyranny of the phone cord… yet not from the phone itself.

But the concept of wireless goes back a lot farther than that. Back in what steampunk fans surely refer to as the good old days, wireless referred to the wireless telegraph, a means of keying Morse code messages over radio waves, and the earliest form of radio communication.

I downloaded this picture of Tesla using wireless technology.

Wireless isn’t just limited to communications. Famed inventor and mad scientist Nikola Tesla conducted experiments in wireless power transmission. Tesla hoped to be able to transmit electrical power worldwide, and while he didn’t quite succeed in that goal… a little over a century later, some of us do charge our smartphones using inductive charging mats.

Inductive charging of LG smartphone (2)
This is totally what Tesla had in mind, except the mat would’ve been a gigantic Tesla coil a hundred miles away. And the smartphone would’ve been a light bulb

Wireless communications might take place over radio, microwave, optical wavelengths, or infrared, but all of these are electromagnetic radiation. Tesla’s wireless power experiments were also electromagnetic in nature. This isn’t surprising, considering that our technology is based on electromagnetism and electronics.

Still, there are other means of causing action at a distance. Sound waves, for example, though we don’t generally refer to shouting as wireless communication. Gravitation is a force similar to electromagnetism, though it’s much weaker, and we have no means of controlling gravitational fields the way we can play with EM fields. Will civilization of the future refer to their advanced, precision gravity manipulation as “wireless”?


Day 17 of the A-to-Z Challenge. Q is for Quaoar, an object in the outer solar system. Discovered in 2002 and named after a deity from Tongva mythology, Quaoar arrived on the astronomical scene during a period of turmoil. You see, it was not alone…


In 1992 (right around the time I was in grade school, possibly learning the mnemonic “My Very Educated Mother Just Showed Us Nine Planets”), astronomers discovered an object that received the provisional name 1992 QB1. This object turned out to be the first Trans-Neptunian object discovered since Pluto (and its moon Charon).

This prompted a renewed effort to locate similar objects, which came to be known as cubewanos (QB1-ohs). It turns out, there are a lot of similar objects in the outer solar system. In 2000, astronomers discovered the object that was eventually named Varuna. Less than two years later, Quaoar was discovered, and it was pretty big. Bigger than QB1.

Many other Trans-Neptunian Objects were found during the first few years of the 21st century. Some of them rival Pluto in size — and the discoverers naturally wanted their discoveries classified as planets. “I discovered a planet” is an impressive quote: it fits on a business card or a t-shirt, and it’s a real hit as a pick-up line.

Were Quaoar, Ixion, Sedna, Haumea, Makemake, and the other objects on the growing list of Trans-Neptunian Objects really planets? No one could say, because the International Astronomical Union had never officially defined the word planet.

Then in 2005, the same group that discovered Quaoar discovered another object — and it was as big as Pluto, or bigger. Obviously, if Pluto is a planet, then the new object must also be a planet, right? (This object received the rather fitting name of Eris — the goddess of discord, who causes arguments.)

A similar crisis had arisen two centuries earlier: astronomers discovered Ceres, and decided it was a planet… then discovered Pallas, Juno, Vesta, etc. The solution then was to create a new classification: these objects would be known as minor planets, though most people just call them asteroids.

In 2006, the IAU decided to resolve the issue with a similar cop-out solution, creating a definition for planet that deliberately excluded these new objects — along with Pluto — but then creating a new classification of dwarf planet. Pluto and Eris (along with Ceres) were specifically called out as dwarf planets.

(As a consolation to Pluto, the IAU also created the classification of plutoid, which at the time they vaguely defined as anything kinda like Pluto.)

After the IAU vote, our solar system was one planet lighter, and astronomers were free to continue discovering inconveniently large objects without fretting over whether they were planets.

But really, Quaoar doesn’t care about the arguments, the disputes over definitions, or the glory of planethood. Quaoar doesn’t care whether we call it a planet, dwarf planet, Trans-Neptunian Object, cubewano, or late for dinner. Quaoar just is.

And 1992 QB1? It’s still just called QB1.

O’Neill Cylinder

For day fifteen of the A-to-Z challenge, I thought I would take a brief break from fiction and take a look at a type of space station. O is for O’Neill Cylinder, which some may know it as “Island Three,” where Island One and Island Two are the comparatively much smaller Stanford Torus and Bernal Sphere.

Interior of an O’Neill Cylinder. Public domain photo from Wikimedia.

Proposed by physicist Gerard O’Neill, the design was for two side-by-side counter-rotating cylinders, each five miles in diameter and twenty miles in length, connected by a support structure.

Each cylinder would consist of six alternating strips of “sky” (transparent windows and mirrors to allow sunlight into the cylinder) and “land,” providing a habitable surface area of over 100,000 acres. Maneuvering would be handled without thrusters, by taking advantage of the angular momentum of the cylinders.

Variants of the O’Neill Cylinder have been seen fairly often in science fiction.

Babylon 5
“Humans and aliens wrapped in two million, five hundred thousand tons of spinning metal… all alone in the night.” – From the Babylon 5 season 1 opening monologue

“The mass of Rama was at least ten trillion tons; to any spaceman, that was not only awe-inspiring but also a terrifying thought.” – Rendezvous with Rama, Arthur C. Clarke

Brian Versteed provides the Kalpana One space settlement concept. While it’s closer in size and design to a Stanford Torus, there’s some rather nice artwork of the concept.

Orion’s Arm has a page with concept art for a McKendree Cylinder. An enormously scaled-up version of an O’Neill Cylinder, a McKendree Cylinder can have as much land area as a small continent.

5 Spaceship-Free Ways Off-Planet in Sci-Fi

So you want to leave Earth, but the idea of traveling business class on Virgin Galactic just doesn’t appeal to you. Maybe you don’t like the roar of the rockets and the feel of 3g of acceleration as you’re blasted into the sky. Or perhaps you just don’t like being squeezed into a seat between Grunthos the Flatulent and the polypous creature who keeps asking if you’ve accepted Cthulhu into your heart.

Whatever the reason, here are five science fictional ways off the planet, without the need for a spaceship.

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5 Interesting Sci-Fi Weapons

Judging by the summer blockbuster movies, people love intense action and big explosions. Sometimes, though, you want something a little more interesting than just a slightly bigger gun or a moderately louder explosion. You want something different.

Science fiction explores the realm of the possible, so it should be no surprise that, aside from the typical Earth-shattering kabooms, there are plenty of interesting (and dangerous) weapons to be found within the science fiction genre.

Be warned — this list includes spoilers. So if you’re the type (like me) who still has a significant reading list backlogged from to the Golden Age of Science Fiction, continue with caution.
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5 Misconceptions about the Moon

The Moon holds a special place in our imaginations — and why not? Along with the Sun and the five classical planets, the Moon is one of the few celestial objects whose apparent motion in the night sky can be seen.

You can even see its disk with the naked eye — and unlike the blinding white-hot disk of the Sun or the barely-discernible-to-human-vision disks of Jupiter or Venus, what a disk is the Moon! Throughout history, we’ve stared at the shadows and highlights of the lunar surface and envisioned everything from a man to a magic rabbit.

In case you’re wondering, that’s Mercury, not the Moon.

It’s not surprising, therefore, that we’ve built up some misconceptions about the Moon. Here are the five misconceptions about the Moon that I find to be the most prevalent, most fun, most frustrating, or just the most annoying.
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