Becoming an interstellar species

Traveling to other star systems poses some serious problems, the first of which is actually getting there. Ignoring things like plotting a correct trajectory, avoiding running into things, and the wear and tear that solar and cosmic radiation could cause on spacecrafts and people, distance and speed are our biggest impediments at the moment. It's generally accepted that the speed of light—299,792,458 meters per second—is a sort of “universal speed limit”. Based on our best knowledge, nothing (with the possible exceptions of some types of muons in very specific circumstances) can travel faster than the speed of light, and nothing can accelerate to the speed of light either. And even if we could, our best technology at the moment is light years away from the speed of light. (See what I did there?)

Let's take the Alpha Centauri system as an example. The Alpha Centauri system is a system of three stars, the closest of which is Proxima Centauri, orbiting about 4.24 light years away. What's especially interesting about Proxima Centauri is that it has an Earth-like planet, apparently within its habitable zone, which might be a good candidate for human colonization outside of our own solar system. But the 4.24-light-year distance means that even traveling at the speed of light, it would take over 4 years to get there. Traveling at ten percent the speed of light, it would take ten times that—over 42 years. Traveling at only one percent the speed of light, it would take 424 years to get there. Assuming we want to be able to make the trip in a single lifetime, it looks like ten percent the speed of light is the bare minimum speed we would need to be able to achieve.

To put all of this in perspective, Voyager 1, currently the fastest spaceship in existence, is traveling at about 17 kilometers per second. That's about 0.00567% the speed of light (half of one ten-thousandth the speed of light). Of course, Voyager didn't start off at that speed—it only got that fast after multiple gravity assists from the giant planets—but for the sake of this discussion, we'll ignore that. At its current speed, if Voyager were pointed in the right direction, it would take 74,780 years to get to Proxima Centauri. That's a long time. But let's say that we somehow managed to double our top spacecraft speed every decade. It would still take us 80 years to get to one percent the speed of light, meaning that it would only take 424 years to get to Proxima Centauri. (Actually, after 80 years, we'd be at 1.45% the speed of light, but at that speed it would still take 292 years to get there.)

Assuming we could continue the trend of doubling our top speed every decade, after 110 years, we would be capable of traveling at 11.6% the speed of light, meaning that we could get to Proxima Centauri in only 36 and-a-half years. This means that a spacecraft sent 80 years from now would actually get there after a spacecraft sent 110 years from now: 80 years + 292 years to get there = 372 years, compared to 110 years + 36.5 years to get there = 146.5 years. And this brings us to what I will call the space-farer's paradox: The longer we wait to send a spaceship, the less time it will take to get there.

The space-farer's paradox means that it may not be worth sending a spacecraft until we can arrive at a point where the technological gain from waiting no longer outweighs the temporal gain from sending a spacecraft earlier. If we continue our thought exercise of doubling our top speed every ten years, this balance is reached somewhere between 140 and 150 years from now. After 140 years, we would have arrived at the ability to send a spacecraft traveling at around 93% the speed of light, which means it would arrive at Proxima Centauri after a voyage of only 4.6 years. Shortly after 140 years  we would arrive at the ability to send a spacecraft traveling at the speed of light itself, beyond which any further progress is impossible, based on our current understanding of the universe. Even if it were possible, waiting another decade to double our speed from 93% the speed of light to 186% the speed of light would yield minimal returns, since the decade it would take to develop the technology would take longer than the difference in travel time—a spacecraft sent 140 from now at 93% the speed of light would arrive 145 years from now, while a spacecraft sent 150 years from now at 186% the speed of light would arrive 152 years from now.

Of course, this is all a little too hypothetical; doubling our speed every ten years is probably far too ambitious an assumption. Instead, let's use actual data to predict how fast our spacecrafts' speeds will increase. Voyager 1 launched in 1977, with a launch speed of 38,030 kilometers per hour. The New Horizons spacecraft that flew by Pluto in 2015 launched in 2006, with a launch speed of 58,536 kilometers per hour. Although their actual speeds at different points in their missions varied, the difference in launch speed between Voyager 1 and New Horizons gives us an idea of the progress we have made. This difference equates to an increase of speed of 154% over 29 years, an average about a 5.3% speed increase each year. With this more modest—and far more realistic—speed increase, we would arrive at 1% the speed of light 120 years from now, and would pass 10% the speed of light around 170 years from now. The benefit of waiting actually tapers off around 180 years from now, at which point we would be traveling at 18.5% the speed of light. At this speed, it would take only 23 years to travel to Proxima Centauri, meaning that a spacecraft launched 180 years from now (in 2197) could arrive as early as 2220. Once again, waiting to launch is no longer worth it after this point, since a spacecraft sent ten years later would only get there eight years faster, meaning that it would actually arrive two years later.

While 23 years might still seem like a long trip, it's a lot shorter than the nearly eighty thousand years it would take at current speeds. A 23-year voyage would mean that young astronauts could be sent to Proxima Centauri and arrive before turning 50. (At these speeds, the effect of time dilation is minimal; the 23 years as observed from Earth would equal about 22.9999608 years from the astronauts' perspective—a difference of only about 5.5 hours in a span of over two decades!) If colonization were the goal, young people could even be sent and arrive while still within child-bearing years.

Or course, we've only been talking about how long it would take to get to Proxima Centauri. Unfortunately, this doesn't take into account the difficulty of slowing down once we get there. Because of this, the first missions to Proxima Centauri would necessarily be fly-by missions (like the New Horizons mission to Pluto), without the ability to stop once we get there. Only later would we develop the ability to slow the ship down enough to orbit a target within the system, and only after that would we be able to develop the technology to land there. But those are discussions for another time.

Why I might (finally?) be switching to Opera

This is my first tech-related post. I work in software development and do web development on the side. I'm always on the lookout for new software, plugins, and services that will make my life easier and less complicated.

Most people install a browser once (or just use the default browser) and don't think about it much after that. As a software tester and web developer, I work with four or five browsers on a daily basis, so I'm constantly noticing the differences between them and seeing what I like and what I don't.

When Google Chrome came out in 2008, I was all-in from the first time I used it. At the time, it was revolutionary: It completely changed the look and feel of the web browser, and best of all, it was blazingly fast. The fact that most browsers now have all of those features shows just how needed they were. Over the years since, Chrome has had its ups and downs, but only one other browser has ever really tempted me to switch for good: Opera.

But with its own ups and downs over the years, I've gone back and forth between loving Opera and wondering why it still existed.

Opera was a different beast

Before version 12 (released in 2012—coincidence?), Opera really set itself apart. While all the other browsers were playing catch-up by cloning Chrome's UI—moving their tab-strips above the address bar, turning the address bar into an omnibar, allowing you to pull tabs off into their own window, hiding the File menu, etc.—Opera went a step further and added some really cool features.

On the UI side of things, Opera had all the same things as Chrome and the rest of the pack, but it also let you fully customize things, putting the tab-strip on either side or even on the bottom of the window, letting you hide the address bar, and even letting you tile, cascade, and stack tabs on top of each other as separate windows within the Opera window—almost like its own little desktop. (Since window-snapping wasn't yet easily accessible in Windows, the tab-as-window management was really pretty cool, and really helpful.)

Opera stood out in other areas, too. It had a built-in mail and chat client, a built-in notes client, a turbo mode for slow connections, and even (unique among well-known browsers) a built-in torrent client. It also had pages and pages of cool setting for nerds like me to sift through and customize to our hearts' content. And for a number of years, Opera was consistently the most standards-compliant and one of the very fastest browsers out there. I loved Opera.

Just another Chrome clone

Then came Opera 13, which they named Opera 15 to avoid the bad luck connotations (there was already an Android-only mobile version named Opera 14, so they couldn't call it that either). In my opinion, the 13 would have been surprisingly appropriate. The Opera people switched to the same layout engine that Chrome used, and as they did, they took out virtually every feature that distinguished it from Chrome. Tabstrip customization? Gone. Windowed tabs within the browser window? Gone. Torrent client? Email client? Other cool stuff? All gone. They also got rid of the ability to synchronize settings between devices, and even did away with bookmarks! And with all of that, the slight advantages in standards-compliance were the only noticeable difference between Opera and Chrome—except of course for the features that Chrome had that Opera didn't. Before the release of Opera 13—err, 15—I had been just about ready to switch for good. I liked it so much, I actually reverted the update and kept using version 12 for a while as my primary browser, but with new vulnerabilities exposed all the time, I knew that couldn't last long. With Opera now just another clone of Chrome, I started to wonder why it even still existed. I finally gave up and turned my back on Opera for good... (Well, for a few years, anyway.)

For the next few years, Chrome was king for me. Since I use all of Google's services, the tight integration was just what I wanted. As an occasional Chromebook user, I used Chrome's apps and extensions extensively—especially Chrome's panel feature, which created little (ironically) chrome-less floating windows that could be docked to the bottom or side of the screen. I used the built-in “OK Google” voice queries and the custom search engines and the Chrome notification center and the app launcher and the fully-offline-capable apps and games and everything else. But the more features Chrome packed in, the slower it started to get. Pretty soon, I started noticing the slow-down; I started noticing that Chrome was using more than half of my memory; and I started noticing the battery-drain issues that went along with it.

I wasn't the only one who noticed. To fix the problems, the Chrome people started hacking out features that not many people were using. The Chrome notification center? Gone. Chrome app launcher? Gone. Chrome panels? Gone. And last year Google announced that Chrome apps are on their way out, too, with new apps already no longer available for anyone except Chromebook users and all app capabilities being phased out by early 2018.

Another chance for Opera

Meanwhile, Opera's people have been trying out a few new things. For years, Opera Turbo has bypassed slow web connections by running webpages through Opera's own servers and compressing them there. Since they had already figured out how to run all your web traffic through their own servers, Opera took the next logical step and recently added a free, full, unlimited VPN to the Opera browser, right at a time when many are becoming increasingly nervous about their online privacy.

Ever since Opera switched to being a Chrome-clone, Chrome extensions have technically worked in Opera, although the way to actually get them working was very hackish and inconsistent. But in the newest versions of Opera, many Chrome extensions work great right out of the box—there's even an extension that lets you install them straight from the Chrome web store. They've also reintroduced bookmarks and settings synchronization back into the mix, along with adding a built-in news aggregator, ad-blocker, and battery saver—all things I use anyway.

On top of all that, Opera feels snappy. It's really fast and still completely standards-compliant, all with an interface that's fresh, clean, and minimalistic. And while they've tried to keep to the essential with the main version of the browser, the Opera team has been trying out even more new things elsewhere, like their new browser, Neon, which packs in a few of the old features people have been missing (like splitting a single browser window between two tabs) along with some new ones that are pretty slick.

When all is said and done, I still don't know if I'm ready to fully ditch Chrome for Opera, but I'm getting really close. I'm using both right now, but I am mostly using Chrome as a handy shortcut to the Chrome apps that I still use, which won't even be available soon. And once they're gone from Chrome, there's a good chance that I will be, too.

Solar System Top Tens

I'm always trying to find new ways to wrap my head around everything that's out there in our solar system. We've got planets, dwarf planets, asteroids, moons, and a whole bunch of other things. It's enough that it can be hard to keep track of everything that's out there, and it can be even harder to become familiar with individual objects. This post is a list of top tens in the solar system. Most of these top tens deal with size—the ten biggest things orbiting the sun, the ten biggest dwarf planets, asteroids, etc. I made these lists for myself, so that I could get to know our solar system a bit better. Hopefully it will be interesting to someone else, too.

#1 Top ten biggest things around the sun

The sun is by far the largest object in the solar system (except for that one time when a comet's halo actually grew bigger than the sun for few days back in 2007). It's about ten times bigger than Jupiter (the biggest planet) and over 100 times bigger than the Earth. For the sake of this post, I'm going to be talking about everything except the sun.

Rank	Name	Diameter?	Size vs. Earth
1	Jupiter	139,822	11x Earth
2	Saturn	120,536	9.5x Earth
3	Uranus	51,118	4x Earth
4	Neptune	49,528	3.9x Earth
5	Earth	12,742	1x Earth
6	Venus	12,104	95% Earth
7	Mars	6,792	53% Earth
8	Ganymede	5,268	41% Earth
9	Titan	5,152	40% Earth
10	Mercury	4,879	38% Earth

The four confirmed giant planets (Jupiter, saturn, Uranus, and Neptune) are just that—giant. It turns out Earth is actually a good size to compare to, since it falls right in the middle of the list. Earth is a mid-sized planet, but still the biggest of the non-giants. Apart from the planets, you may have noticed a few less-familiar names in the list. Ganymede and Titan are both moons (of Jupiter and Saturn, respectively), but even though they are “just” moons, they are both bigger than the planet Mercury. The next runner up for the top ten list is actually another one of Jupiter's moons, Callisto, which is basically the same size as Mercury—literally 99% Mercury's size. If we don't include moons in our list, then Mercury comes in at number eight and Pluto and Eris are the ninth and tenth objects, at 19% and 18% the size of Earth. With moons included, Pluto and Eris rank as numbers sixteen and seventeen.

If Planet Nine exists, it probably fits in somewhere between Earth and the ice giants Uranus and Neptune, at around two to four times the size of Earth.

#2 Top ten moons

As we've already seen, some of the solar system's moons are actually pretty big. Many pictures of the solar system include Earth's moon and no others, even though it's only the fifth largest moon in the solar system. Two moons (Ganymede and Titan) are both bigger than the planet Mercury, and a total of seven moons (Ganymede, Titan, Callisto, Io, “Luna”, Europa, and Triton) are all bigger than the dwarf planet Pluto. There are a total of eighteen moons in our solar system that are large enough to be round. Here are the top ten moons in the solar system:

Rank	Name	Diameter?	Size vs. Luna	Size vs. Mercury	Size vs. Pluto
1	Ganymede¹	5,268	1.5x Luna	8% > Mercury	2.2x Pluto
2	Titan²	5,152	1.5x Luna	6% > Mercury	2.2x Pluto
3	Callisto¹	4,821	1.4x Luna	99% Mercury	2.0x Pluto
4	Io¹	3,630	1.1x Luna	74% Mercury	1.5x Pluto
5	“Luna”³	3,474	1x Luna	71% Mercury	1.5x Pluto
6	Europa¹	3,138	90% Luna	64% Mercury	1.3x Pluto
7	Triton⁴	2,707	78% Luna	56% Mercury	1.1x Pluto
8	Titania⁵	1,578	45% Luna	32% Mercury	67% Pluto
9	Rhea²	1,529	44% Luna	31% Mercury	64% Pluto
10	Oberon⁵	1,523	44% Luna	31% Mercury	64% Pluto

^1 Moons of Jupiter
^2 Moon of Saturn
^3 Moon of Earth
^4 Moon of Neptune
^5 Moons of Uranus

Runners up are Saturn's moon Iapetus, at 62% the size of Pluto, and Pluto's own orbital companion Charon, at 51% the size of Pluto. (In fact, Charon is so big compared to Pluto that the two objects actually orbit each other, and are considered by some to be a double planet.) We often learn about the major planets and completely ignore their moons, but the reality is that the moons are much more like planets than many people think. Apart from many of the moons listed being large enough that they could have been planets, Titan has a full atmosphere with clouds, rain, rivers and seas, Europa and Enceladus both have subsurface oceans that are currently the most likely places we know of to look for life, and a number of the moons are also good candidates for human colonization.

#3 Top ten asteroids

When the first asteroids were discovered in the early 1800s, they were considered planets for around half a century and even given their own planetary symbols before being reclassified as asteroids. Although they're no longer considered planets, they're still interesting places to study and explore. Ceres, the largest asteroid, is the only round asteroid, and is currently classified as a dwarf planet. It was visited by the Dawn spacecraft in 2015.

Rank	Name	Diameter?	Size comparison
1	Ceres¹	946	1.3% Luna; 7.2% Pluto
2	Vesta	525	56% Ceres
3	Pallas	514	54% Ceres
4	Hygiea	435	46% Ceres
5	Interamnia	324	34% Ceres
6	Europa	313	33% Ceres
7	Davida	293	31% Ceres
8	Sylvia	292	31% Ceres
9	Cybele	267	28% Ceres
10	Eunomia	266	28% Ceres

^1 Classified as both an asteroid and a dwarf planet

The asteroids in this list are quite large, compared to the hundreds of thousands of other asteroids out there. Even so, there are a number of other larger objects—trojans, centaurs, and trans-Neptunian objects—that are sometimes considered asteroids. I've only included main-belt asteroid in this list, but I've separated the other large non-planets out into their own lists below.

#4 Top ten TNOs

TNOs (trans-Neptunian objects) are icy objects that orbit out beyond Neptune. Because ice isn't as hard as rock, many TNOs have been pulled into a round shape by their own gravity, making them dwarf planets. (Not all TNOs are dwarf planets, but the biggest ones—the ones in this list—are, although only five have officially been classified as such.) The most famous TNO is beloved old Pluto, but there are other worlds out there that are just as interesting. Because most of the TNOs we know about have been discovered during this century (i.e., after the year 2000), there is still a lot that we don't yet know about them. As such, there's a good chance this top ten list won't look the same even a few years from now.

Rank	Name	Diameter?	Size vs. Pluto	Size vs. Ceres
1	Pluto*	2,374	1x Pluto¹	2.5x Ceres
2	Eris*	2,328	98% Pluto²	2.5x Ceres
3	OR₁₀	1,535	65% Pluto	1.6x Ceres
4	Makemake*	1,447	61% Pluto	1.5x Ceres
5	Haumea*	1,403	59% Pluto	1.5x Ceres
6	Charon	1,212	51% Pluto	1.3x Ceres
7	Quaoar	1,046	44% Pluto	1.1x Ceres
8	Sedna	1,032	44% Pluto	1.1x Ceres
9	Salacia	883	37% Pluto	93% Ceres
10	MS₄	865	36% Pluto	91% Ceres

* Officially classified as dwarf planets by the IAU
^1 About ^1⁄_5 the size of the Earth (19%); 68% the size of the moon; less than half the size of Mercury (48.7%)
^2 Slightly smaller, but 29% more massive than Pluto

As I mentioned before, Pluto's orbital companion Charon is large enough to be a dwarf planet in its own right; some preliminary versions of the definition of “dwarf planet” actually included it as one. Runners up for the top ten are Orcus (35% the size of Pluto—88% Ceres') and 2013 FY_2_7 (34% Pluto's size—85% Ceres'). It's worth noting that of the top ten TNOs, all but Pluto and Charon were discovered after the year 2000, cementing the fact that this is a new era of solar system discovery, with plenty of new objects yet to be found.

Other things in the solar system

Most people know about planets, moons, and asteroids, and even people who don't know what TNOs are have at least heard about dwarf planets. But there are a number of other types of objects out there in the solar system that we hear less about. These include trojans—small bodies that share a major planet's orbit, centaurs—small bodies that orbit between the orbits of the outer planets, and near-Earth objects—small bodies that orbit (partially or completely) within the orbit of Mars.

#5 Top ten trojans

Rank	Name	Diameter?	Size comparison
1	Hektor¹	242	26% Ceres' size
2	2010 EN65 ²	200	82.5% Hektor's size
3	Agamemnon¹	166	69% Hektor
4	Diomedes¹	164	68% Hektor
5	Äneas¹	143	59% Hektor
6	Patroclus¹	142	59% Hektor
7	2006 RJ103 ²	138	58% Hektor
8	Achilles¹	136	56% Hektor
9	2011 HM102 ²	135	56% Hektor
10	2014 QO441 ²	130	54% Hektor

^1 Trojans that share Jupiter's orbit
^2 Trojans that share Neptune's orbit

Although there are thousands of other trojans—some of which orbit Earth, Mars, and Uranus—there are only eighteen others known that have diameters of 100 or larger.

#6 Top ten centaurs

Orbiting out between the giant planets, centaurs display some properties of regular asteroids and some properties of comets, with a few centaurs officially classified as both. On top of that, two of the largest centaurs, Chariklo and Chiron, both have rings, making them the only known objects other than the giant planets to have them. They are called centaurs due to their hybrid nature, after the half-man-half-horse creatures of Greek mythology.

Rank	Name	Diameter?	Size comparison
1	Chariklo	259	27% Ceres' size
2	Bienor	204	79% Chariklo's size
3	Chiron	188	73% Chariklo
4	Pholus	157	61% Chariklo
5	Amycus	90	35% Chariklo
6	Asbolus	75	29% Chariklo
7	Hylonome	70	27% Chariklo
8	Cyllarus	65	25% Chariklo
9	Crantor	60	23% Chariklo
10	Nessus	60	23% Chariklo

The three largest centaurs—Chariklo, Bienor, and Chiron—are listed as probable dwarf planets by Mike Brown. He also lists Pholus and Amycus as possible dwarf planets.

#7 Top ten NEOs

NEOs (near-Earth objects) are mostly very small objcts that orbit at least partially within the orbit of Mars. These are of particular interest to astronomers, both because they are close enough that we have plenty of opportunities to study them and because we want to make sure none of them are going to hit us any time soon. While NEOs may be small compared to other things out in space, some of those listed here are still much bigger than even the biggest mountains on Earth. I've included Mount Everest for size comparison, which is 8.848 high at its highest point.

Rank	Name	Diameter?	Size comparison
1	Ganymed	33	3.7x Mount Everest
2	Eros	18.4	2.1x Everest
3	Don Quixote	18.4	2.1x Everest
4	Eric	10.8	1.2x Everest
5	1998 QE2	10	1.1x Everest
6	Sisyphus	8.5	96% Everest
7	1990 TR	4.3	49% Everest
8	Geographos	3.5	39% Everest
9	Toutatis	3	34% Everest
10	1993 UC	2.7	31% Everest

#8 Top ten (or fourteen) SSOs with the most (known) moons

Earth has one moon, Venus and Mercury don't have any, Pluto has five (depending on how you count), and the giant planets each form their own little solar systems with dozens of moons each and probably more we haven't even discovered yet. It might surprise some people to learn that even a few otherwise-unremarkable asteroids have more than one moon.

Rank	Name	Moons
1	Jupiter	67
2	Saturn	62
3	Uranus	27
4	Neptune	14
5	Pluto¹	5
6	Mars	2
7	Haumea	2
8	Sylvia	2
9	Eugenia	2
10	Elektra	2
11	Minerva	2
12	Kleopatra	2
13	Balam	2
14	Litva	2

^1 Since Pluto and Charon orbit each other, they are sometimes counted as a double planet or double dwarf planet. Counted this way, they still rank fifth, with four moons orbiting the pair.

With nine solar-system objects that each have two moons, I can't include some in the list and not others, so this list ends up being a Top-14 list. For comparison, there are around 45 known objects in the solar system with a single moon and a few more that are harder to categorize (like two same-sized object that orbit each other and have an additional object orbiting both of them). The two-mooned objects in this list are listed from largest to smallest.

#9 Top ten furthest known objects

The question of which solar-system objects are the furthest from the sun is actually a bit complicated. Because orbits are not perfectly circular, some objects may be very distant from the sun at one time, but relatively close at another. For example, one object, 2014 FE₇₂, goes all the way out to over 3000 AU (1 AU is the distance from the sun to the Earth), but also swings in to less than 40 AU (around the average orbit of Pluto).

Some lists of the furthest objects in the solar system use the furthest distance an object goes, even if at other times it is much closer; others look only at objects that never get closer than a certain distance; and still others look at the semi-major axis—a sort of average distance. Because there are comets that go so far out we don't actually know their farthest distance, it seems that making the list based on farthest distance isn't the way to go, since we can't actually make any definitive judgments there. The semi-major axis seems like a good compromise, but if an object comes in so close that it spends part of its orbit in the main asteroid belt, it doesn't really make sense to call it one of the farthest objects in the solar system. Because of this, I've chosen to make my list based on where objects actually are right now. This means that there are objects that may go out further, but for the moment, these are currently the farthest known objects.

Rank	Name	Distance
1	v774104	103
2	Eris	96.2
3	“DeeDee”	91.6
4	OR10	87.6
5	2013 FS28	86.2
6	Sedna	85.6
7	2014 FC69	84.4
8	2006 QH181	83.6
9	“Biden”	83.3
10	2013 FY27	80.2

Because these regions of the solar system are so far away, there are likely many more objects out there that we haven't even found yet—we were only able to discover objects like Sedna and Biden because they happen to be at the closest part of their orbits! As such, there's a good chance that this list will change substantially within the next few years as our ability to peer farther out into space improves.

#10 Top ten places to look for life

For many, the most important reason to keep exploring space is to find out if there's life anywhere else out there. While other stars have planets that may be similar to Earth, the best place to start looking is right here in our own cosmic backyard. And although most people probably think first of Mars when they think of looking for life in the solar system, there are actually a few other places that may have even better chances of life.

Rank	Name
1	Europa
2	Titan
3	Enceladus
4	Mars
5	Venus
6	Io
7	Ceres
8	Callisto
9	Ganymede
10	Small bodies

While this is a top ten list like the rest, everything past the first four is a bit of a stretch. Europa, Titan, Enceladus, and Mars are all considered good places to look for life by a number of scientists. The subsurface oceans on Europa and Enceladus offer excellent possibilities for life, the surface oceans on Titan do as well, and Mars has always been a favorite choice due to its similarity to Earth and presence of small amounts of liquid water. The other objects listed here are sometimes listed as possible—though not probable—locations for life. And of course, while there are equations to predict the likelihood of different kinds of life in the universe, this top-ten list is clearly the least numerically-founded list I've included.

Final thoughts

As I said at the outset, I compiled these lists mostly for myself, because I wanted to get to know more than just the major planets and the official dwarf planets. By learning the names and a few properties of nearly 100 solar-system objects (10 lists × 10 objects, minus some repeats), I've expanded my understanding of what's out there, but the really interesting thing for me has been taking these lists and learning a bit more about each item individually.

With the now-tired debate about Pluto's planetary status still raging in just about every solar-system-related comment section on the internet, we sometimes lose sight of the fact that whatever they're classified as—planets, dwarf planets, asteroids, or just “small solar system bodies”—each object out there is an entire world, just waiting for us to learn more.

(The object formerly known as) Snow White and the Seven Dwarfs

With 2016 over and 2017 well underway, we'll soon be coming up on the 10th anniversary of the discovery of 2007 OR₁₀, a dwarf planet that orbits out past Pluto in the scattered disk. When OR₁₀ was first discovered in July of '07, it was bright enough that it was clearly either fairly large (i.e., a dwarf planet) or almost completely white, so Mike Brown and his associates assumed the latter and nicknamed it “Snow White”. Later observations made it clear that it was actually quite large and quite red, so the nickname no longer made sense, and was dropped. With OR₁₀'s discovery now ten years after the fact, it's time for this distant world to join the ranks of the named dwarf planets, and time is running out for Mike Brown's team to pick a new name.

Is OR₁₀ really a dwarf planet?

I've written before (and so has Mike Brown) about the fact that the IAU created the “dwarf planet” category, officially added a few members to the club, and then essentially closed the books on it, leaving an entire generation of children to learn that the solar system has eight real planets and exactly five official dwarf planets. The reality, of course, is that we now know about at least fifty dwarf planets, and possibly hundreds, with more being discovered all the time. There are lists out there of possible and probable dwarf planets, most of which agree on a number of objects that almost certainly are dwarf planets. One simple—and certainly the most conservative—solution to the question of what to call a dwarf planet is to say that since Ceres is officially a dwarf planet, anything larger than Ceres must also be a dwarf planet. If we use this overly conservative threshold for dwarf planets, OR₁₀—which is 63% larger than Ceres—clearly makes the cut, along with a total of seven other dwarfs (including Ceres).

Snow White OR₁₀ and the seven (other) dwarfs

• Pluto–Charon
• Eris
• 2007 OR₁₀
• Makemake
• Haumea
• Quaoar
• Sedna
• Ceres

When astronomers realized that OR₁₀ was big rather than just bright, they also realized that it is actually one of the largest objects orbiting the sun, with initial estimates putting it between Makemake and Haumea—both “official” dwarf planets—in size. More recent estimates put OR₁₀ as possibly larger than Makemake, which would make it the third largest known dwarf planet, and place it within the top twenty largest objects in the entire solar system! (Even OR₁₀'s newly discovered moon is fairly large, beating out all but the top seven main-belt asteroids in size.)

A rose by any other name…

Despite being the third-largest known dwarf planet, 2007 OR₁₀ conspicuously lacks a name. In fact, it's the largest unnamed object in the solar system! In the ten years since its discovery, amateur astronomers and space enthusiasts have proposed plenty of ideas—everything from Norse, British, and Aztec deities to ‘Prince’ (Get it? The artist formerly known as Prince—the object formerly known as Snow White?) to a number of variations on ‘Orten’ (Orten, 'Orton, Horton, etc.—all based of course on the temporary designation OR₁₀). While it's true that not having a name doesn't really change anything about OR₁₀ itself, it definitely downgrades it in the eyes of the public, resulting in many lay publications happily mentioning Quaoar, Sedna, and Orcus as possible dwarf planets but completely ignoring OR₁₀, despite the fact that it is significantly larger than any of them. It's likely that this total silence around OR₁₀ is at least partially due to it's lack of a name.

The clock is ticking for Mike Brown's team to choose a name for OR₁₀; the IAU's official rule is that after ten years, anyone can submit a name for official consideration. Since OR₁₀ was discovered in July of 2007, there are only a few months left for a name to be submitted, considered, and approved. While I'd love to submit my own ideas and possibly even be the one to name a dwarf planet, what I'd really love would be for that honor to go to the discoverers instead. Both Mike Brown and Meg Schwamb (whose research under Mike Brown actually led to OR₁₀'s discovery) have stated publicly that they now have enough information to name OR₁₀; hopefully it won't be too long before the third largest dwarf planet finally has a name of its own.

We're going to need a new definition of what is and isn't a planet… Again.

Many people were understandably shaken when the International Astronomical Union rocked the world—err, solar system—by reclassifying Pluto as a dwarf planet in 2006. There were all sorts of opinions about it, even among scientists, but ultimately what the scientific community all agreed on was that our understanding of planets had changed drastically in the nearly eighty years since Pluto had been discovered, and our classifications needed to reflect that.

Some pushed for classifications that would include Pluto as a planet, while others (perhaps tongue-in-cheek) argued that worlds like Earth, Mercury, Venus, and Mars, aren't really planets either. The long and short of it is that any informed opinion recognizes that the concept of a planet is, in the mind of the public at least, very loosely constructed, and largely misinformed.

We now understand that there are multiple types of planet, including rocky inner planets, gas giants, ice giants, and—depending on how you classify things—dwarf planets. Beginning with the most familiar, we have Earth, a rocky, inner planet, and the only place in the universe confirmed to sustain life. Saying that the Earth is a rocky planet really just means that it has a solid surface to land on. Perhaps surprisingly for some, this isn't a fact that is common to all planets: Mercury, Venus, and Mars also have solid surfaces, as do Pluto, Eris, and the other dwarf planets, but the giant planets Jupiter, Saturn, Uranus, and Neptune do not.

In fact, the closest you could come to landing on any of the giant planets would be to land on one of their planet-sized moons. Jupiter's moon Ganymede is larger than the planet Mercury, as is Saturn's moon Titan, which has clouds, rivers, seas, sand dunes, and a fully formed atmosphere. All said, there are over a dozen moons in the solar system—including our own—that are large enough to be either planets or dwarf planets, and all of them have solid surfaces. (Two of them are larger than Mercury, a total of seven are larger than Pluto, and in all sixteen are larger than the dwarf planet Ceres.)

Planet-sized moons* in the Solar System:

Earth	1	“Luna”¹
Jupiter	4	Europa¹, Ganymede², Io¹, Callisto¹
Saturn	5	Tethys, Dione, Rhea, Titan², Iapetus
Uranus	4	Ariel, Umbriel, Titania, Oberon
Neptune	1	Triton¹
Pluto	1	Charon
Total	16

* All listed moons are larger than the dwarf planet Ceres
¹ Larger than dwarf planet Pluto
² Larger than planet Mercury

In many ways, these planet-sized moons fit the common idea of what a planet is better than the giant planets do. They are all large enough to be round. They have solid surfaces that we can land on. They have enough gravity to keep us from flying off into space, but not enough to kill us. A few of them even have vast oceans of liquid water, which would allow us to build underwater colonies, and perhaps even find life outside of our home world.

For a bit of contrast, Jupiter is made almost entirely of thick clouds of poisonous gas. At some point, the gas may transition to liquid, but the pressure and gravitational forces of the giant planet would crush any spacecraft long before it got that far. On top of that, it produces extreme levels of radiation, so much so that Jupiter actually puts out more heat than it gets from the Sun, scorching the faces of its nearby moons. Jupiter's gravitational pull is so strong that from nearly half a billion miles away (about 780 million kilometers), it pulls on the Sun itself, causing the gravitational center of the solar system to actually be an empty point in space somewhere between the Sun and Mercury. On top of this, Jupiter has 67 known moons orbiting around it—almost like its own mini solar system—complete with four that are planet-sized. The stories for the other giant planets are similar, with the key take-home message being that these are places to orbit around, not places to visit and land on. In this way, although they are clearly not stars, they are in some ways much more like stars than like the concept of planets that most people have.

In the coming decades and centuries, as we venture out further into the solar system and begin more in-depth exploration—and even colonization—of the planet-sized moons, these contrasts between the giant planets and the rest of the worlds out there will become even more apparent. As such, I propose that in the coming centuries, we will likely again adopt a new definition of a planet: A round object with a solid surface that humans can land on.

This new definition would bring the number of (known) planets up to around seventy, including four rocky planets³; one asteroid planet⁴; eighteen satellite planets⁵; and at least 50 icy planets out past Neptune⁶. Part of the debate at the time of Pluto's reclassification centered on the idea that allowing dwarf planets to be called planets would lead to an unwieldy number of planets—too many for school children to learn. Frankly, this argument is absurd. (Continued below.)

³ In order from the Sun: Mercury, Venus, Earth, and Mars

⁴ Ceres, currently classified as a dwarf planet

⁵ Earth's moon “Luna”; Jupiter's moons Europa, Ganymede, Io, and Callisto; Saturn's moons Mimas, Enceladus, Tethys, Dione, Rhea, Titan, and Iapetus; Uranus's moons Miranda, Ariel, Umbriel, Titania, and Oberon; Neptune's moon Triton; and Pluto's orbital companion Charon

⁶ This includes the currently official dwarf planets Pluto, Haumea, Makemake, and Eris, along with OR₁₀, Quaoar, Sedna, and many others.

With over seventy planets, the difficulty of learning them all could indeed become an issue, but as we come to explore and colonize these worlds, they will each develop their own unique histories and cultures, much like the countries of our own world, of which there are many more than seventy. Just as children learn a few facts about major countries and regions of the world today in their geography classes, they would learn the principle facts about the major planets and groupings of planets in their classes on solar system “geography”. Planetary populations—such as the planets orbiting Jupiter, or those orbiting Saturn or those orbiting within the Kuiper belt—would become the new continents, and interplanetary and other regional alliances would be studied and understood just as well as other countries, regions, and continents are understood today.

The principle “continental” regions of the solar system:

• Inner system
  • Mercury
  • Venus
  • Earth & Luna
  • Mars
  • Near-Earth objects
• Asteroid belt
• Ceres
• Vesta, Pallas, and the other asteroids
• Jupiter system
  • Europa
  • Ganymede
  • Io
  • Callisto
  • minor moons and trojans of Jupiter
• Saturn system
  • Mimas
  • Enceladus
  • Tethys
  • Dione
  • Rhea
  • Titan
  • Iapetus
  • rings and minor moons of Saturn
• Uranus system
  • Miranda
  • Ariel
  • Umbriel
  • Titania
  • Oberon
  • rings, minor moons, and trojans of Uranus
• Neptune system
  • Triton
  • minor moons and trojans of Neptune
• Outer system
  • Pluto & Charon
  • Haumea
  • Quaoar
  • Makemake
  • OR₁₀
  • Eris & Dysnomia
  • Sedna
  • many others

To be perfectly clear, I'm not proposing a new definition of planet for right now, or for a decade or even a century from now. I'm simply making the observation that as we step out into the solar system, our current idea of what is and isn't a planet will likely naturally shift as we gain specific experience with the various worlds of the solar system. As this happens, it will become more and more clear that the giant planets are more things to orbit around than things to land on, and as such, it is likely that we will begin to think of them as essentially different from the solid bodies of the solar system.

The Hebrew Alphabet is a Mess

For the past week or so, I've been learning modern Hebrew on Duolingo, just for fun. Hebrew is a fascinating language, and an amazing example of a nearly-dead language taking on new life to become a flourishing part of everyday life for millions of people. But as my title already says, the Hebrew alphabet is a mess.

The Hebrew alphabet—or alef‑bet—officially has 22 letters, but five of these letters have separate forms at the end of a word. If that were all, it might be OK. But that's not all—not by a long shot. First of all, vowels aren't written in Hebrew, so when you see a word for the first time, even if you know the consonants, there's no way to know what the vowels are, which can completely change the meaning of a word. And knowing the consonants isn't a trivial matter either!

Letters with more than one sound

There are six consonant letters that can each make more than one sound. So bet sometimes makes a b sound and sometimes a v sound; he is sometimes pronounced like an English h and is sometimes not pronounced at all; vav is sometimes pronounced as a v, sometimes as an o, and sometimes as u; yod can either be the y sound or the i sound; kaf can either make a k sound or a kh sound (like Scottish ch in ‘loch’); pe makes either a p or f sound; and shin/sin is either pronounced sh or s. Of course, it's possible to use special dots on the letters to show the exact pronunciation, but this is only common in dictionaries and very basic children's books. This means that as an adult learning Hebrew, when you see a new word, you really have to guess how to pronounce it. For example, seeing the word שכב (shin/sin-kaf-bet) for the first time, there's absolutely no way to know whether it's pronounced sakab, sakav, sakhav, sakhab, shakab, shakav, shakhav, or shakhab. (It's shakhav.) And once again, that's assuming you know the vowels as well. There are some patterns—like that pe, bet, and kaf are more likely to be pronounced as p, b, and k at the start of a word and as f, v, and kh everywhere else—but there are no guarantees!

Letter	Sound(s)
א	(silent)
ב	b or v
ג	g
ד	d
ה	h
ו	v, o, or u
ז	z
ח	kh
ט	t
י	y or i
כ, ך	k or kh
ל	l
מ, ם	m
נ, ן	n
ס	s
ע	(silent)
פ, ף	p or f
צ, ץ	ts
ק	k
ר	r
ש	sh or s
ת	t

Sounds with more than one letter

On top of all this, when you hear a new word for the first time, there's often no way to tell how it should be spelled. It seems like with twenty-two letters, six of which have multiple pronunciations, there should be around twenty-eight different consonant sounds in Hebrew, right? Well, actually there are only twenty consonant sounds. This is because seven of the consonant sounds of Hebrew can be written in multiple ways, so even with multiple pronunciations for some letters, there are still fewer sounds than letters. The v sound can either be written with bet or with vav; the kh sound is either kaf or khet; the t sound is either tet or tav; the k sound is either kaf or kof; the s sound is either samekh or sin; and to top it all off, in spoken Israeli Hebrew, there are two letters (alef and ayn) that are always silent and one (he) that is usually silent at the end of a word, and sometimes silent at the start of the a word. This means that if someone tells you the word for cake in Hebrew is ooga, there's no way to know whether it's אוגה, אוגא, אוגע, עוגה, עוגא, or עוגע. (It's עוגה.) Even for a seemingly straightforward word like katav (“he wrote”), there are eight possible spellings (כתב, כתו, כטב, כטו, קתב, קתו, קטב,  or קטו—the right one is כתב)!

Sound	Letter(s)
(silent)	א, ע, (ה)
b	ב
v	ב, ו
g	ג
d	ד
h	ה
z	ז
kh	ח, כך
t	ט, ת
y	י
k	כך, ק
l	ל
m	מם
n	נן
s	ס, ש
p	פף
f	פף
ts	צץ
r	ר
sh	ש

The vowels are even worse

Of course, these lists don't even include the vowels. They're rarely written, but when they are, they have the same problem as the consonants. By most accounts, there are only five vowel sounds in modern Israeli Hebrew: a, e, i, o, and u, which are pronounced the same as in most European languages. That seems fairly straightforward, except that for those five vowels, there are fourteen different sets of niqqud (the little dots used in children's books and dictionaries). So when you hear the a sound, it could be אַ or אָ or אֲ or אֳ (all of these examples are given with alef as the base letter); when you hear an e sound, it could be אֵ or אֶ or אֱ or אְ; and the i, o, and u sounds can all be written either with or without a helping consonant (yod for i and vav for o and u). In older dialects of Hebrew, all these different symbols made different sounds—some were long and others were short, one a was pronounced further back than the other, etc.—but in modern Israeli Hebrew, there's really no way to tell which of the four a sounds someone is actually pronouncing, or whether or not to write a vav for an o sound. Because of this, hearing a word like zot for the first time, there's no way to know whether the o is just written as a dot (i.e., usually not written at all) or written with a vav. (In this case, it's actually not written at all, and there's a silent alef where the 'vav' would be: זאת [zayin-alef-tav].) A word with multiple vowel sounds ends up having multiple possible spellings, like lehitraot, which has sixty-four (!) different potential spellings, depending on the different versions of e, i, a, and o used. (And that's assuming you already know the right consonants to use!)

64 possible ways to write lehitra'ot:
לֵהִיתרָאוֹת, לֵהִיתרָאֹת, לֵהִיתרַואֹת, לֵהִיתרַאֹת, לֵהִיתרֲאוֹת, לֵהִיתרֲאֹת, לֵהִיתרֳאוֹת, לֵהִיתרֳאֹת, לֵהִתרָאוֹת, לֵהִתרָאֹת, לֵהִתרַאוֹת, לֵהִתרַאֹת, לֵהִתרֲאוֹת, לֵהִתרֲאֹת, לֵהִתרֳאוֹת, לֵהִתרֳאֹת, לֶהִיתרָאוֹת, לֶהִיתרָאֹת, לֶהִיתרַאוֹת, לֶהִיתרַאֹת, לֶהִיתרֲאוֹת, לֶהִיתרֲאֹת, לֶהִיתרֳאוֹת, לֶהִיתרֳאֹת, לֶהִתרָאוֹת, לֶהִתרָאֹת, לֶהִתרַאוֹת, לֶהִתרַאֹת, לֶהִתרֲאוֹת, לֶהִתרֲאֹת, לֶהִתרֳאוֹת, לֶהִתרֳאֹת, ל`הִיתרָאוֹת, ל`הִיתרָאֹת, ל`הִיתרַאוֹת, ל`הִיתרַאֹת, ל`הִיתרֲאוֹת, ל`הִיתרֲאֹת, ל`הִיתרֳאוֹת, ל`הִיתרֳאֹת, ל`הִתרָאוֹת, ל`הִתרָאֹת, ל`הִתרַאוֹת, ל`הִתרַאֹת, ל`הִתרֲאוֹת, ל`הִתרֲאֹת, ל`הִתרֳאוֹת, ל`הִתרֳאֹת, לֱהִיתרָאוֹת, לֱהִיתרָאֹת, לֱהִיתרַאוֹת, לֱהִיתרַאֹת, לֱהִיתרֲאוֹת, לֱהִיתרֲאֹת, לֱהִיתרֳאוֹת, לֱהִיתרֳאֹת, לֱהִתרָאוֹת, לֱהִתרָאֹת, לֱהִתרַאוֹת, לֱהִתרַאֹת, לֱהִתרֲאוֹת, לֱהִתרֲאֹת, לֱהִתרֳאוֹת, לֱהִתרֳאֹת

Vowel	niqqud, etc.
a	אַ, אָ, אֲ, אֳ
e	אֵ, אֶ, אְ, אֱ
i	אִ, יִ
o	אֹ, וֹ
u	אֻ, וּ

Time for a reform?

When you add the vowels' ambiguity to the consonants' ambiguity, you end up with even more possible spellings for any new word you hear. The reformist in me wishes we could just pare it down to one sound per letter, and one letter per sound. So, for example, instead of bet sometimes being pronounced as b and sometimes as v, and vav also sometimes being pronounced v, bet would always be pronounced b and vav would always be pronounced v. As long as we're thinking about changing things, there's really no reason for five letters to have different word-final forms while the other letters don't, so we could get rid of the word-final forms, too. This would give us exactly twenty consonant sounds and twenty letters:

Sound	Letter(s)
(silent)	א
b	ב
v	ו
g	ג
d	ד
h	ה
z	ז
kh	ח
t	ט
y	י
k	ק
l	ל
m	מ
n	נ
s	ס
p	פ
f	ף
ts	צ
r	ר
sh	ש

If we did this, we could keep the word-final form of pe for the f sound. This is the only alternate sound that can't be written with a separate letter, so keeping the final form would be a reasonable thing to do. Also worth noting is that kaf, ayn, and tav would be removed completely, since their sounds are covered by other letters (kof, alef and tet).

This all seems well and good. If we did this, a word like shakhav could be unambiguously written as שחו (shin-khet-vav), and a person who's never seen the word before would know exactly how to pronounce it. (Well, the consonants, anyway.) But our spelling reform would have some unfortunate unintended consequences. Just like English, Hebrew's weird spelling system actually has one benefit: it makes it easier to see the relationships between words. A good example of this in English is the word electric and the related word electricity. If we got rid of the letter C and just used k or s instead, we could spell these words elektrik and elektrisity, making the pronunciation more closely tied to the spelling, but also making it ever so slightly less obvious that these words are related. This is the case even more in Hebrew, where words like pa'al and nif'al are less obviously related when the p and the f are completely separate letters.

A compromise

For this reason, along with a host of others, Hebrew speakers haven't implemented any major alphabetic reforms. But they have introduced a few conventions that make it ever so slightly less impossible to figure out the correlations between spelling and pronunciation. One of these conventions—using yod for the I sound and vav for the o and u sounds—actually dates back centuries. Without it, a word like ooga (which means ‘cake’, from a few paragraphs back) would simply be written עגה (ayn-gimel-he), and we would have absolutely no idea what the vowels were. With the vav, we can at least narrow the first vowel down to one of two possibilities. Along with this, when vav does make a v sound instead of a vowel sound, it's often written as a double vav, as in the word barvaz (ברווז) ‘duck’, which, without the double vav could be confused for barooz or baroz. Similarly, when yod makes an ay or ey sound, it's often written as a double yod, as in tsaharaym (צהריים) 'noon'.

While these conventions don't solve the problem—it still feels very much like the Hebrew alphabet was designed for a completely different language—they help a little. And short of convincing every Hebrew speaker everywhere to change the way they do things, I don't think there's much I can do other than just view reading and writing in Hebrew as a special sort of challenge. After all, if I can figure this out, that's saying something, right?

Meters, Feet, and the Speed of Light

A first proposal

The speed of light is currently defined as exactly 299,792,458 meters per second. A better way of saying this is that we define the length of a meter by how far light travels in one second: One meter is defined as being exactly 1/299,792,458 the distance light travels in one second. The idea of defining our units of measure based on actual physical properties of the universe is a good one, and clearly much better than using variable-sized objects like body parts or other things. What bothers me though, is that as long as they were officially redefining what a meter is, why didn't they just use the much more round number of 300,000,000? This would be infinitely easier to remember, doing so would make a lot of sense, and not much would actually have to change.

The new meter (exactly 1/300,000,000th the speed of light) would be almost exactly the same length as the current meter—0.99930819333 current meters, in fact. For daily use, almost nothing would have to change. A standard meter stick used today would still be accurate enough for all basic measurements, as the difference of less than one current millimeter would be imperceptible for most individuals. Larger scales at which the small difference would actually matter would be calculated by computers, as they already are today, and individual people really wouldn't be affected by the change at all in their daily lives. With a new kilometer equal to exactly 1/300,000 the speed of light, driving 100 km/h in new kilometers would be the same as driving 99.930819333 kilometers in the current system, meaning that for the most part, current speedometers and road signs would not need to be changed. Although most maps and atlases would need to be changed, the use of digital maps by a growing number of individuals and businesses would make the transition mostly painless.

Another option

Another option is to use a unit of measure that's even easier to remember. Why use a unit equal to 1/300,000,000 the speed of light when we could create a new unit equal to exactly 1 billionth the speed of light? This would be exactly 0.299792458 current meters, or about 0.3 meters. If you're anything like me, you'll realize right away that there already is a unit of measure that's close to 0.3 meters—it's a foot, currently defined as exactly 0.3048 meters. In fact, one foot is almost exactly equal to the distance light travels in one nanosecond. Why not redefine the foot so that it is exactly equal to the distance light travels in one nanosecond? A new foot—which we could call a “light-foot” and abbreviate as 𝓁𝒻—would equal exactly 0.98387105643 current feet.

Of course, the main objection most people have to the foot as a unit of measure has nothing to do with the foot itself, and everything to do with other related units of measure, such as the inch (¹⁄₁₂ of a foot) and the mile (5,280 feet). In comparison with the metric system, in which a meter is subdivided into centimeters (¹⁄₁₀₀ of a meter) and multiplied into kilometers (1,000 meters), the use of feet, inches, and miles seems ridiculous. For this reason, the “light foot” could be defined as a decimal unit of measure, meaning that it would be subdivided by a unit equal to exactly ¹⁄₁₀ of a light-foot: the light-inch. The current inch is equal to 2.54 centimeters. The light-inch would be only slightly larger at 2.99883898 cm. In metric units, I am 187 cm tall. In current inches and feet, I am 6 feet, 1⅝ inches tall—I usually just say I'm 6′2″. In light-feet and inches, I would be exactly 62.3574660884 light-inches tall, or around 6 light-feet, 2.35 light-inches—I could still tell people I'm 6′2″. Because a light-foot is slightly smaller than a current foot, but ¹⁄₁₀ of a foot is slightly larger than ¹⁄₁₂ of a foot, once again, most daily measurements wouldn't change noticeably. A standard 10-inch light-foot ruler would be almost the same length as a current 12-inch ruler. But this is as far as the seemingly good idea goes.

Along with changing from duodecimal to decimal inches as a subdivision of the light-foot, it wouldn't make sense not to change larger measurements as well. These changes would be more drastic and more difficult to implement. Instead of using a mile as a larger unit of measure, we would probably want to use a unit equal to 1000 𝓁𝒻 (one kilolightfoot). There are currently no common comparable units of measure. A kilolightfoot would be equal to 0.18633921523 current miles (not quite ⅕ of a mile) or 299.792458 current meters (not quite ⅓ of a kilometer). Using 10,000 𝓁𝒻 instead (one myrialightfoot?) would give a unit equal to 1.86339215233 current miles, or almost exactly 3 current km (2.99883897999937 km—a difference of 1.16 meters). While these distances seem more reasonable, either multiple of a light-foot would require changes to all existing road signs and vehicle speedometers, as well as all maps and atlases. Because of this, although the coincidence that light travels approximately one foot in one nanosecond is interesting, the idea of using a decimal light-foot as a basic unit of measure would cause many more problems than it would solve.

The Astronomical Unit as a unit of measure

A third possibility is that we could define the meter using some other natural property of the universe, such as the astronomical unit (AU—the average distance from the sun to the Earth), which is currently defined as exactly 149,597,871 km. If we instead defined one kilometer as equal to exactly 1/150,000,000 the average distance from the sun to the Earth, a new meter would once again be nearly the same size as a current meter—0.99731814 current meters, to be exact. Once again, a standard meter stick would have only a negligible difference—less than three millimeters—meaning that for most purposes, the old meter stick could still be used. Differences at larger scales would be more pronounced, so driving 100 new km/h would be equivalent to driving 99.731814 current km/h, but even these differences wouldn't be enough to necessarily warrant a change in speedometers or road signs.

The AU-mile?

Of course, we could go the other way, and define the mile using the AU, which is currently equivalent to 9,295,581 miles. Adjusting the length of the mile so that 1 AU would equal 10,000,000 miles instead would make each mile about seven percent shorter than it currently is, but this would also face the problem of deciding what to do with feet and inches. If the AU-mile were used as the standard unit of measure, a subdivision equal to 1/1000th of an AU-mile could be used as a smaller measure, and would be equal to 4.90818624014 current feet or 1.63606208005 current yards. A unit equal to 1/10,000th of an AU-mile would be equal to about half of a current foot, 5.88982348817 current inches, or about 15 current centimeters (14.9601516599). In any case, these new measurements would necessitate changes in all aspects of measurement, since even mile markings on road signs and speedometers would need to be changed. Once again, using miles and feet does not seem like a good idea.

What about light-years?

While it might seem tempting to use the light-year as a basis for units of measure, it doesn't lend itself as easily to nice round numbers. One light-year is about 9.5 trillion kilometers (9,460,730,474,334). Redefining the kilometer so that one light-year would equal exactly 10 trillion kilometers would result in a new meter equal to about 0.946 current meters. This difference, though still not enormous, is large enough that all current measurements would have to be changed, including meter sticks, speedometers, road signs, maps, and atlases. The disparity, even for everyday use, would be noticeable to even individuals in non-technical fields.

Redefining miles based on light-years would make even less sense. In current measurements, one light-year equals 5,878,625,374,273 miles, which doesn't adjust nicely to any multiple of ten. Adjusting the definition of a mile so that one light-year would equal exactly 5 trillion miles would cause similar problems to a light-year-based meter, resulting in a large enough disparity that all existing measurements would have to be changed.

My final proposal

Ruling out the two proposals for light- and AU-based imperial units, we're left with the two proposals for metric units. While either would be a reasonable change requiring minimal difference in everyday life, the light-based system is demonstrably superior. To begin with, the AU is currently defined as the average distance from the sun to the Earth. Because the Earth's orbit is not a perfect circle, the actual distance varies from around 0.983 AU to 1.016 AU—a total potential difference of nearly 5 million current km (4,936,729.743 ) between the two extremes. This means that although we have set a defined length for the AU, it isn't easily verifiable, and it's almost never the actual distance between the sun and the Earth. In addition to this, the possibility that humankind will expand beyond Earth in the coming centuries makes any geocentric measurement system non-ideal. In contrast, the speed of light is a universal constant, measurable from anywhere in the universe. Because of this, I propose the light-based meter, defined as being exactly equal to 1/300,000,000 the speed of light, as a new international standard of measure.

TL;DR
One meter is currently defined as exactly 1/299,792,458 the distance light travels in one second. Changing this to exactly 1/300,000,000 instead would make a lot of sense and wouldn't even require us to change our current meter sticks, speedometers, or road signs. We should do it.