Continuing along the lines of world-building for science fiction settings, I had planned a post on just how much heat Coruscant (of Star Wars universe fame) would generate and the fact that the planet would almost certainly require giant polar heat radiators or something along those lines. Trouble is, I did the math and… it doesn’t work out that way.
Coruscant supposedly has a population of one trillion, which sounds like a lot, and is, but that’s only about 125x Earth population and in the end, if you figure something like 2500 watts per person of energy (above anything but Iceland on Earth today), you end up with about 1% of the energy received from the sun. That would likely cause noticeable global warming but nothing that couldn’t be dealt with easily in the Star Wars universe (like putting out umbrellas in space to reduce solar radiation by 1%). So, no need for super-duper lasers beaming hear from Coruscant.
As with all my posts on these sorts of things, I’m not saying authors can’t use tropes, in this case, the planet-wide city. But some of the overlooked details from such tropes can make for useful technical hooks for authors. Imagine if Coruscant did have huge polar laser beams. This would give the planet a very different look, wouldn’t it? Sort of like the polar jets on a black hole. Makes for an interesting aesthetic touch you could add. But take it further: the polar jets would be dangerous to fly through, so now you have a peril for an out of control ship to deal with (drama!). Or maybe you could envision space stations that harvest this waste heat, legally, or not. Or maybe this energy can be targeted via mirrors or the like and now you have a very high power weapon.
If you have planet wide cities and don’t want to deal with the waste heat, no problem. I don’t recall anyone complaining about it regarding Coruscant (other than me of course, but I’m weird that way). But if you do want to deal with it, the possibilities range from the aesthetic to the dramatic.
But let’s turn back to why I thought waste heat would be a problem for Coruscant. There are really two reasons:
- In the movies, the entire planet looks like it is covered by a continuous city
- The various on-line Star Wars resources indicate that at times: The entire surface of Coruscant was covered by sprawling kilometers-high ecumenoplis. (Wookieepedia, which provides references). The population is given as, variously, 1 to 3 trillion.
Let’s take that data and do some number crunching, something any worldbuilder should consider doing to “kick the tires” on their premise. Coruscant is basically earth sized, which means we can use Earth data for surface area, etc. We also have Earth data that a high-rise like the World Trade Center towers in NYC had about 20,000 people in them during the day. Let’s assume Coruscant has about 20,000 people in a 100x100m area, as a starting point. Now Coruscant probably has factories and various open spaces but it is supposed to be covered with “city” multiple kilometers thick so 20,000 people for the relatively short WTC tower is spread out over a taller Coruscant structure, as partial offset. This would yield a population of: one million trillion people.
Hold on you say, the poles aren’t necessarily populated and you have too little room for factories and such. Okay, scale it back by 10x or even 100x, this is still one to ten thousand times higher population than per the Star Wars cannon. Not that it really matters, the Star Wars setting is a lot of fun regardless, but the population estimate is just way out of whack. As a check, one trillion people seems like a lot but if spread over the earth, that’s about 2 people per square kilometer. For comparison, Hong Kong has a population density of 6500 per square km and applied across the world, would result in a population of 3300 trillion. You can scale that back for a lower population density but to get to the stated population of Coruscant, you’d have to scale it back by 1500x which doesn’t qualify as “city-wide planet” in my book since Wyoming has a population density of 2.3 people per sq. km. and the only US state less dense is Alaska, at 0.5.
Let’s assume a lot of the planet is factory and other “empty” space, it still seems like the population of Coruscant should be something more like 100 trillion or higher. Now, if you assume 2500 watts per person, and that might actually be a pretty paltry number for a super high technology society that seems to fly everywhere, the power dissipation per person is on par with the total energy received from the sun. Aside from that being a large amount of power to generate, that’s a lot of heat to dissipate: without heat radiators you are going to quickly fry the planet. And if population is 300 to 1000 trillion, now you talking about 10x solar power. The planet would burst into flames.
Of course, you can ignore this. The Star Wars guys do. But wouldn’t it be a cool setting that did not ignore it? You’re the author. The only limits you have are your imagination. How would you handle that much energy? The power conduits and power plants probably not as much a problem as it sounds: the planet is after all, entirely city. Plenty of room to ship power around and plenty of space for power planets. But how do you extract the waste heat and export it into space? Maybe all over the planet there are cooling towers. But these aren’t your nuclear power planet cooling towers: these extend out of the atmosphere and are in a vacuum within their walls. They literally pipe heat out from the surface of the planet into the space. Aside from being really cool because they would be really tall and really big, imagine how the planet would look: it would be studded with cylinders. Plus intersolar space is a not a total vacuum, there would be plenty of particles to “light up” in the path of these heat export beams: the planet would have hundreds or thousands of beams of light radiating from it. In short, it would look very different from how Coruscant is shown in the movies. Not a bad way to differentiate your planet-wide city from ones your readers have already seen, right?
Just to be clear, this is not something I’m demanding science fiction writers address. Instead, I’m just pointing out that if you take your worldbuilding to the next level, you might find ways to enhance your setting, even find a cool hook for an entire novel premise.
In addition to heat dissipation, a planet like Coruscant would have interesting issues with regard to food (where does it come from, how many planets does it take to feed Coruscant, how many food freighters per day would have to arrive?) and even simple oxygen replenishment: what is converting the CO2 back to O2? Could be oxygen processors but that will take yet more power. Would make for an interesting touch on your world though, wouldn’t it: vast oxygen regeneration plants to go along with the waste heat towers. And really big freighter ships to feed the planet, star destroyer size!
Happy world building!
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