{"id":45411,"date":"2019-01-29T06:00:46","date_gmt":"2019-01-29T11:00:46","guid":{"rendered":"https:\/\/www.shamusyoung.com\/twentysidedtale\/?p=45411"},"modified":"2019-01-29T07:38:12","modified_gmt":"2019-01-29T12:38:12","slug":"andromeda-part-15-elaadens-orbit","status":"publish","type":"post","link":"https:\/\/www.shamusyoung.com\/twentysidedtale\/?p=45411","title":{"rendered":"Andromeda Part 15: Elaaden’s Orbit"},"content":{"rendered":"

I have no idea why the designers decided to make two of our five habitable worlds into orange deserts. Sure, the planets are a little different. Eos is a bit like the Mojave Desert and Elaaden is more an expanse of sand dunes like the Sahara. I wonder if their cobbled-together Frostbite offshoot wasn’t up to the job of depicting forests, meadows, and swampsYes, I realize the planets need to be uninhabitable. We could say these planets are low in oxygen. Fine for plants, not so good for animals.<\/span>. Even if we decide to have two different deserts, did they really need to be the same shade<\/i> of orange? It’s space! This science in this game runs on cartoon logic anyway, so why not go wild and give us a purple desert or whatever?<\/p>\n

Disastronaut<\/h3>\n

The tempest is currently flying through Elaaden's atmosphere in this shot, which means that gas giant is close and the other moons are REALLY close.<\/div>
The tempest is currently flying through Elaaden's atmosphere in this shot, which means that gas giant is close and the other moons are REALLY close.<\/div><\/p>\n

I have a confession to make. I’m really into astronomy. Not real<\/strong> astronomy, mind you. I like shallow pop-astronomy. I like having complex questions boiled down to simple answers that you can understand without any complex mathematics. What would it be like to stand on the surface of X? How many livable exoplanets are there? How long would it take to get a message to someone in another star system? How long would it take to fly there? Is the space elevator really possible? What are the odds that there’s a planet out there with sexy blue-skinned women who want to learn about this thing we earthlings call kissing<\/em>Actually, this question is easy. The answer is zero.<\/span>?<\/p>\n

This means that occasionally I feel the need to take my shallow, badly-understood middle school pop-science and try to use it to ask interesting questions. I’m afraid today is one of those days.<\/p>\n

You Tried<\/h3>\n

The local temperature is allegedly above boiling. We have environments on Earth that are way more hospitable than Elaaden, and we STILL consider them uninhabitable. Why is anyone bothering with this place?<\/div>
The local temperature is allegedly above boiling. We have environments on Earth that are way more hospitable than Elaaden, and we STILL consider them uninhabitable. Why is anyone bothering with this place?<\/div><\/p>\n

I’ll give credit to whoever designed Elaaden: They tried to base it on some kind of science. Sadly, they messed it up. I did the same thing in my orbital bombardment calculations<\/a> during the Mass Effect 3 analysis. A little bit of knowledge can be a dangerous thing. It’s easy to do hours of meticulous research but then stumble on one detail and turn the whole thing into a joke.<\/p>\n

The game explains that Elaaden is “tidally locked”, which means that it’s always daytime on one side of the planet, and night on the other. That’s good science! Except, Elaaden is also the moon of a gas giant. This means that it’s tidally locked to its host planet, not the sunYes, I know this star isn’t called the “sun”. You know what I mean.<\/span>. Which means it can’t always be daytime.<\/p>\n

This is a small detail and I doubt most people would notice. It’s not a terrible fault, and I actually appreciate that the writer made the effort. But just for fun let’s take a break from nitpicking Andromeda and explore this idea a little. Let’s ask ourselves…<\/p>\n

What Would Elaaden Be Like?<\/h3>\n

Was this place habitable before the vaults went wrong? It sorta looks like it's been a sand-blasted furnace for a long, long time.<\/div>
Was this place habitable before the vaults went wrong? It sorta looks like it's been a sand-blasted furnace for a long, long time.<\/div><\/p>\n

The host planet is a gas giant, like Jupiter in our solar system. The planet isn’t given a name within the gameWhy would you NOT name the planet? It’s totally free and you can use the name to do worldbuilding stuff. Like, give it a Krogan name to tell us about the Krogan who settled here. Not having a name for this planet is like living on Earth and not having a word for CLOUDS. It would come up constantly in conversation because it nearly fills the sky.<\/span>, so let’s name it after\u00a0Tinia<\/a>, an Etruscan<\/a> god that occupied a similar place as the god Jupiter on the org chart of their mythology. To keep things simple, let’s assume that Tinia is of similar size and mass to Jupiter.<\/p>\n

If Elaaden is tidally locked, that means one side of the planet always faces Tinia and the other side always faces away from it. However, this won’t result in “always day” or “always night”, because Elaaden must orbit around Tinia. (If it didn’t, it would fall into its host planet and vanish in the crushing depths.) This is the same relationship that the moon has with Earth. No matter when you look up at the moon, you’re always seeing the same side of it. One side of the moon always faces us, and the other side of the moon faces away, into empty space. We call the latter the “dark side” of the moon, but it’s only “dark” in the sense that we can never see it from Earth. It actually gets exactly as much sunlight as the “light” side of the moon. The new moon (the point of the month when the moon is dark to us) is when the moon is positioned such that the side facing us isn’t getting any sunlight, and the supposed “dark side” of the moon is getting it instead.<\/p>\n

I'm pretty sure SAM is talking crazy. I can't see how you can be tidally locked to two different bodies at once. That doesn't make any sense.<\/div>
I'm pretty sure SAM is talking crazy. I can't see how you can be tidally locked to two different bodies at once. That doesn't make any sense.<\/div><\/p>\n

So what would a day be like on Elaaden? That question is a lot more complicated on Elaaden than it is on Earth. Here, our day \/ night cycle is determined by Earth spinning on its axis. Elaaden doesn’t spin on its axisOr more precisely: It spins on its axis perfectly in sync with how fast it orbits Tinia.<\/span>, so our day \/ night cycle will actually come from how fast Elaaden orbits Tinia. So now the question is, “How long is Elaaden’s orbital period?”<\/p>\n

Going back to Jupiter for reference: Jupiter has 4 real moons and 75 more oddly-shaped rocks that we’re obliged to call moons because Jupiter is the biggest planet and we can’t risk pissing it off. The four main moons are Io, Europa, Ganymede, and Callisto. Because of orbital resonance<\/a>, moons can’t have arbitrary orbital periods relative to each other. If one moon had an orbital period of 100 hours and another had an orbital period of 101 hours, then they would quickly pull each other out of whack. Maybe they would crash and merge, or one would get thrown off, or they would pull on each other until they fell into a proper resonance.<\/p>\n

To keep this simple, let’s just borrow the orbital periods of Jupiter’s four main moons: Io does a lap around Jupiter once every 42 hours. Europa makes the trip every 85 hours. Ganymede does it in 172 hours, and Callisto in 17 days.<\/p>\n

All these pissed of Krogan aren't really helping the habitability rating of the planet.<\/div>
All these pissed of Krogan aren't really helping the habitability rating of the planet.<\/div><\/p>\n

42 hours wouldn’t be a bad day length. Sure, Humans would have a lousy time with it, but that’s going to be a problem no matter where we settle. 85 is somewhat more troublesome. That means the sun will be up for 42 straight hours, followed by 42 hours of darkness. At that point you have bigger problems to worry about than keeping a proper sleep schedule. You might be able to grow crops on that world, but they would need to be very tolerant of temperature extremesAnd so would your colonists.<\/span>. A 172 hour cycle would probably be uninhabitable, and a 17 day cycle would give you a rhythmic cataclysm to deal with.<\/p>\n

The problem here is that you’re heating up when you’re in direct sunlight and you’re cooling down when you’re not. On Earth that process is fast enough that we don’t suffer from too many extremes. It’s like cooking a hot dog over an open flame. If you turn constantly, then it’ll cook evenly. If you cook it for an hour on one side before turning it over, then one side will be scorched while the other remains raw.<\/p>\n

Are these trees leftover from before the broken vaults ruined the climate, or are they adapted to this environment?<\/div>
Are these trees leftover from before the broken vaults ruined the climate, or are they adapted to this environment?<\/div><\/p>\n

Think of the temperature climb you get on a typical day between sunrise and midday. Now imagine that process kept going<\/i> for several more hours. The day side of the planet would quickly become dangerously hot and the night side would get dangerously cold. Humans have a hard time surviving above 49C \/ 120F, and plant lifeFor example, the crops you’re hoping to grow.<\/span> can’t take prolonged periods below freezing. A long day \/ night cycle will take you beyond these two extremes in a single day. Maybe a nice thick cloud cover could level out the temperature extremes. That might insulate enough to slow down both the heating and cooling. Sadly, Elaaden has clear skies.<\/p>\n

But Shamus, why couldn’t Elaaden have an orbital period of 24 hours?<\/b><\/p>\n

I think<\/i> it’s possible? If you’re willing to accept Universe Sandbox2<\/sup><\/a> as a legitimate depiction of celestial bodies, then the Earth could indeed orbit Jupiter once every 24 hours. If you want to orbit Jupiter in 24 hours, then you need to orbit it at a distance of 180,000 miles. Jupiter has a spherical radius of 43,441 miles, which means you’d still be above the planet’s surface. (And not caught in its atmospheric cloud of doom.) This would also put you well above the roche limit<\/a>, so your planet won’t get torn apart by tidal forces and turned into a pretty planetary ring. <\/p>\n

But I’m not sure what the ramifications would be of orbiting something that big, that close. Your moon is going to get hammered<\/i> with radiation. Tinia would loom quite large in the sky. On the other hand:<\/p>\n

Boy howdy, that is CLOSE.<\/div>
Boy howdy, that is CLOSE.<\/div><\/p>\n

Visually, it does appear to be quite close. Elaaden is clearly closer to Tinia than Io is to Jupiter, so a near 24 hour cycle might be possible. Then again, this image also shows the other moons being incredibly close to Elaaden and this is obviously an image designed with artistic, rather than scientific, concerns in mind.<\/p>\n

If Elaaden orbited Tinia at the distance suggested by the above image, then it would make for a very strange day. On Earth, eclipses are rare because the moon only goes around the Earth once a month, and it’s pretty small in the sky so it doesn’t always line up just right to block the sun. Here on Elaaden we’re going around once a day, and Tinia looms so large in the sky that a daily eclipse would be unavoidable.<\/p>\n

On earth, a lunar eclipse<\/a> is when the Earth is positioned directly between the sun and the moon. (This is different from the more exciting solar<\/i> eclipse, when the moon blocks our view of the sun.) During a lunar eclipse, the moon passes into the shadow of Earth. You might expect the moon to go dark, but what ends up happening is that the moon turns orange. If you picture yourself standing on the moon and looking up at the Earth, it’s easier to understand where the orange comes from. The Earth is in front of the sun, and Earth’s atmosphere is backlit. Essentially, you’re seeing a sunset that goes all the way around Earth so it’s ringed in orange-red light. On Elaaden, this would happen every single day.<\/p>\n

Here is a simulation of Earth orbiting Jupiter in Universe Sandbox 2. The Earth would pass into Jupiter's shadow for part of every orbit.<\/div>
Here is a simulation of Earth orbiting Jupiter in Universe Sandbox 2. The Earth would pass into Jupiter's shadow for part of every orbit.<\/div><\/p>\n

Let’s assume we’re on the side of Elaaden that faces Tinia, positioned so that our host planet is directly overhead. The sun would rise in the east in the morningEast \/ west is a bit arbitrary, but you get the idea.<\/span>, and then sometime before mid-day the sun would duck behind Tinia. (Remember, from our point of view Tinia is in a fixed spot overhead.) This would result in an eclipse that would last for hours. Sometime in the afternoon we’d exit the eclipse, and then we’d have sunlight again until nightfall. Given the size of Tinia, this would make for a sort of two-phase day cycle. A 24 hour orbit might go something like this:<\/p>\n