Fiction Science #4: The Mystery of Meridian's Gravity

 

WELCOME

This series looks to take a deep dive into some of the events and places of the Halo franchise and determine how sciencey they are. I make a point to give as much leeway to the fiction, so long as it does not directly contradict with science, since this is, you know, fiction.  Occasionally I will discuss some aspect of Halo is science terms without actually looking at the truthiness of any particular event.  This is one of those times. I always make a point to warn people if there might be spoilers ahead, even if they are incredibly minor, because there are new people getting into the Halo lore every day, and what might be basic and obvious to a lore veteran, it may not for a new recruit.  If nothing else, this article might spur some interest in the extended Halo universe, so if at the end you want to learn more, check out the related media for a good place to start.

 

RELATED MEDIA (SERIOUSLY MINOR SPOILERS)

 
 

THE QUESTION

WHAT IS UP WITH THE GRAVITY ON MERIDIAN, THE COLONY VISITED IN HALO 5: GUARDIANS?

 

THE ANSWER

For those unaware, Blue Team and Fireteam Osiris visit the colony Meridian during the events of Halo 5: Guardians.  No big deal, right?  Well there isn't anything specifically odd about that, but something jumped out at me the other day that seemed weird, so I thought I would address it here.  Specifically, Halo Waypoint lists Meridian's stats as a diameter of 1,909 miles (3,073 kilometers), and a gravity of 1.1x that of Earth.  Meaning, Meridian is physically smaller than the moon at 2,159 miles diameter, yet the moon's gravity is 1/6th of Earth's, while Meridian's gravity is actually MORE than Earth's.  How is this possible?

Well to start, I am not going to address the WHY, because frankly I don't know, and 343 hasn't given us any explanation.  We know there is some Forerunner stuff down there, but you would think a facility underground would contain hollowed out areas for storage and stuff, which would lower the density not raise it.  Again, I don't know why, and I don't have anything to go off of to make more than a guess, so I am not going to address that right now.  I am only going to cover the actual data on Meridian, specifically how dense would Meridian have to be to support a gravity 1.1x Earth's with a diameter smaller than the moon.

So first off, how do you calculate gravity?  To determine this, you need to know the average density of the body (planet or moon), and the radius (or diameter).  This will determine how much "stuff" there is, and assuming you are standing on the surface, will also determine how far away from it you are.  Since we are making the assumption we are standing on the surface of the body, it simplifies the equations considerably.

For the purposes of this, we can use Earth as the baseline to figure out what the gravity of Meridian is relative to Earth.  This will make it considerably easier to understand, and works for what we need.  Using world-builders.org, I am going to use this simplified equation:

gravform.gif

This will let us plug in whatever numbers we want and figure out the gravity of a planet or moon relative to Earth.  For those wanting something more full of numbers, I would suggest this page, which lets you plug in exactly the numbers you want and gives you the gravity of the body.

For Meridian, we know the gravity (1.1 x Earth), and the radius (0.24 x Earth).  Earth's density is about 5.5 g/cc (cubic centimeter), so plugging in those numbers and solving for Meridian density gives us 25.1 g/cc.  Kinda denser than Earth at 5.5 g/cc.  For reference, the densest material on Earth is either Osmium or Iridium, both around 22 g/cc.  So the AVERAGE density of Meridian is denser than the densest material we know of.  That is pretty incredible.  If you are curious about the density of other bodies in our solar system, Earth is the densestThe Sun is denser than the gas giants, but is far less dense than any of the rocky worlds.

...solving for Meridian density gives us 25.1 g/cc... So the AVERAGE density of Meridian is denser than the densest material we know of.

So what does this mean?  I have no idea, but I do know that this is not a natural formation.  I would say this couldn't be just from a Forerunner structure inside Meridian, because no matter what it is made of, there would be more open space than actual "stuff", meaning the density would probably be lower than a solid body.  This thing isn't made out of pure Osmium, and even if it were, the density is still too low.  If I had to guess, I'd say something to do with slipspace since you can kind of do whatever you want on that front and pass it off as believable in the Halo universe.  Maybe we will never find out, but I do know that if humans came across a planet or moon with characteristics not just abnormal but outside the bounds of naturally possible, you'd better believe there would be a team of scientists trying to figure out what the hell is going on.  
 

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