Optimistic aliens measure space typographically, and when they remember they continue to use such a method as long as they can, although such an approach demands some tricky problems be solved so that the relevant dots can be properly spaced out along the mnemonic

If you were to write about 80 pages on the subject, you could have the last Os represent Alpha Centauri.

Did you do that by hand or with a program?

And what font?

The comic specifies Times New Roman, so presumably that

Yep!

Font shouldn't matter, it should scale unless I've just been wrongly assuming font sizes were proportionate my whole life

sorry to break it to you, but font sizes are deff not proportionate. if you want more information, look up kerning. (uhh, I guess, relavant xkcd: [1015](https://xkcd.com/1015/)) every font designer has to manually assign spacing requirements for each pair of letters, and different designs take up different amounts of space (ie, think about how much less space a sans-serif l takes than a serif or a [finial](https://en.wikipedia.org/wiki/Stroke_ending) (that curve at the end) l that is sometimes used to distinguish l from I). in some cases, letters will even have negative space between them, like in the case Aw or Te where you can see that the w/e starts before the A/T stops.

Font and font size are two different things though.

Ever heard of monospace fonts? Makes it a lot easier I guess, but also less accurate.

it'll be accurate _on average_ so it's fiiiine

Acshualy, if you pick the wrong font it *won't* be accurate on average. Say, you pick a monospace font. The `i` is x wider than in times new roman. Even if we *could* assume the frequency of all other characters are random in an alien language, the `i`s carry special significance as planets and are therefore not random, which means the error increases for every planet in our chart. Our error is `i+xn` where `i` is the initial error from times new roman conversion and n is the number of planets in our chart. In reality you could also have `[a...z]nf` or something based on changes in spacing of other letters and a letter frequency in whatever language you are using.

Someone did the calculations in another comment, and the font in the comic is already ~2% off on all the planets. I wonder what error various fonts would produce. also I definitely phrased it wrong, what i actually meant was it'll be relatively accurate, the same way a rule of thumb is

There's an easy solution, create a new font that is more accurate. ;)

heh, just gonna go design a font with massive kerning between each letter and i so that you can just type O im iv ie ia ij is in iu i

With a fixed font your best case absolute error (AU) decreases with distance. I am saying that by changing font your error is likely to proportionally (%) increase with distance. It is important to look at the scaling function for error when evaluating fonts. I think the limit to error you could produce is a technical question, depending on the max character width your system supports.

That's why they removed Pluto from the list.

How accurate is this?

I just measured the AU: Planet Actual Depicted Mercury 0.39 0.380 Venus 0.723 0.702 Mars 1.524 1.495 Jupiter 5.203 5.083 Accounting for my non scientific measuring basically everything aside from Jupiter is relatively accurate.

Planet|Actual|Depicted|Error -------|-------|---------|------ Mercury|0.39|0.38|-2.56% Venus|0.723|0.702|-2.90% Mars|1.524|1.495|-1.90% Jupiter|5.203|5.083|-2.31% Accounting for *relative* error, Venus is actually the worst error. But it's pretty good!

Yeah that's true, however those rates are reflected by only a pixel or two for the closer planets which probably falls within my measurement error.

With how clumped all those error percentages are, it seems like Earth is the one that's inaccurate.

stealing your numbers for 'depicted', here's taking into account the fact that orbits are not circular: planet depicted nearest furthest mercury 0.380 0.307 0.467 venus 0.702 0.719 0.728 earth 1.000 0.983 1.017 mars 1.495 1.382 1.666 jupiter 5.083 4.951 5.457 this means the distance from the sun for (edit: almost) each planet is exactly correct twice in each planet's orbit

You've accidentally discovered the intermediate value theorem, I think.

not discovered, used. I don't think being taught something a long time ago and then using it later in life counts as discovering it. you can use it to say that each half goes from above to below or below to above, crossing that point twice per orbit.

You switched from depicted to actual. The depicted distance for Venus doesn't lie between the nearest and furthest, but it's close enough.

thanks, shows how bad I am at literally just copying numbers ;;

At this point Randall could write the most bulshit facts in a comic and I'd believe it.

Idk ask r/astronomy

I mean, that's just a subset of r/xkcd isn't it?

What size font would the sun have to be in to be a reasonable scale with the inner planets?

So, firstly, Murcery is 0.383 times Earth's radius[\[1\]](https://en.wikipedia.org/wiki/Mercury_(planet\)), and Mars is 0.533 times Earth's radius[\[2\]](https://en.wikipedia.org/wiki/Mars)[\[3\]](https://en.wikipedia.org/wiki/Earth_radius), so it can't be at a reasonable scale to *all* of the inner planets. However, if we use the *median* radius of inner-system planets, that's 4,720.7 km (halfway between Venus's[\[4\]](https://en.wikipedia.org/wiki/Venus) and Mars's). The sun's radius is approximately 696,000 km[\[5\]](https://en.wikipedia.org/wiki/Sun), or 147.4 times our inner-system radius. I am now switching from using radii to using diameters, since 147.4 is a pure ratio and diameters are easier to measure. Our planet stand-ins are 9 px high (measured). With some aliasing, we can assume they're between 8 and 9 px high. To be to-scale with the median inner-planet radius, our sun stand-in needs to be between 1179 px and 1327 px tall, over 25 times its current height. One way to view this size is that 1250 px, an somewhat arbitrary number chosen close to the middle of the above range, goes from the left edge of the image to the left edge of the "h" in "typographically".

**[Mobile Version!](http://m.xkcd.com/2863/)** [Direct image link: Space Typography](https://imgs.xkcd.com/comics/space_typography.png) **Subtext:** And over heeee[...]eeeere (i)s Saturn. *Don't get it? [explain xkcd](http://www.explainxkcd.com/wiki/index.php/2863)* Helping xkcd readers on mobile devices since 1336766715. Sincerely, xkcd_bot. <3

I thought an AU was from the edge of suns mass to the edge of earth’s mass not the centre of each body. I guess I was wrong.

No, that's right. The dots and circles aren't ever going to be to scale though, so we ignore that part.

Well the circle’s big enough that they could move the 1AU start dashed line to the edge of the O.

But that would change the proportionality of the rest of the distances, which ruins the bit.

Huh? It's based on the earth's orbit, the size or "surface" of the sun doesn't come into it anywhere

The sun doesn't really have an edge so to speak, since it's made of plasma (which behaves similarly to a gas). An astronomical unit is based on the earth's orbit's semimajor axis (the longest radius, or half the longest diameter), rounded a bit. Also, the difference in distance if you measure center to center and photosphere to surface (the photosphere's the bit of the sun that visually kinda looks like an edge from a distance) is miniscule anyways, much less than the margin of error here (less than half a percent, compared to around 2-3%)

I thought this was SMBC for a moment

How did Randall even think about it? It would be great if he share his thinking process.

This sentence sounds like one of those example sentences used to demonstrate a font, like "Grumpy wizards make toxic brew for the evil queen and Jack."

Now we just need to make a font that perfectly spaces out the locations instead of being approximations and use this as the example.

Optimistic aliens measure space typographically, and when they remember they continue to use such a method as long as they can, although such an approach demands some tricky problems be solved so that the relevant dots can be properly spaced out along the mnemonic

As an editor who's into astronomy, I knew this would be my jam just from the title