Solar System Cartogram
For sentimental reasons, every active Mars rover is counted as one person, although that's not enough to make Mars more than a dot.
For sentimental reasons, every active Mars rover is counted as one person, although that's not enough to make Mars more than a dot.
In this comic, Randall has made a cartogram showing the planets in the solar system. Cartograms are a type of map in which geographic area is displayed proportionately to some secondary characteristic - in this case, population. From the title text it is clear that the population in question is human (persons) (but even if all life forms where counted it it wouldn't matter, since the only confirmed life in the Solar System is on Earth). Thus the other planets have a population of 0 and are shown as nothing more than dots.
This comic is a joke about cartograms, which are used, for instance, to show electoral representation. A standard American electoral map is very misleading. Though the split between the two major parties, Democrats and Republicans, is about 50-50, most of the area of the U.S. map is shown in the color associated with the Republican Party, red. That's because many Democrats live in densely packed districts occupying little land area, while many Republicans live in rural districts with large land area but few people. This has led to the rise of electoral cartograms in which district areas are shown in proportion to population, correcting the misimpression that most of America is conservative.
Solar system diagrams are likely also to be misleading. Illustrators are overwhelmingly forced to use a far more scaled-down spacing between planets, compared to their scaled sizes, even if they can (or care to) maintain consistency in the relative distances and/or radii on linear scales. (The huge factors of difference involved instead may lend themselves to being physically modeled to better give some sense of the spacing and sizing differences.) Here, Randall has intentionally applied the wrong solution to the problem.
Interestingly, the side of the Earth shown includes China and India, two countries that alone account for over a quarter of all humans on Earth.
The title text states that Randall, who once worked on sensors for Mars rovers, counts every active one as a person for sentimental reasons. However, compared to Earth's roughly 7,900,000,000 persons, Mars is still nothing more than a dot. There are a total of five rovers at the time of the comic's publication; in chronological order, they are Sojourner, Spirit and Opportunity, Curiosity, and Perseverance. Only the latter two were functional at the time of the comic's publication, giving Mars a rover population of two. A third rover, China's Tianwen-1, landed on Mars on 2021 May 14, making for an all-time high of three active rovers.
Mars rovers are a recurring theme on xkcd and only a few weeks earlier, a comic named 2433: Mars Rovers was released. This is the fourth comic this year to reference Mars Rovers.
