Help! Everything is falling through my mesh!

I have a really large planet model, and I mean really.
400000 units.
No matter what I do, no matter how big or small it is, everything if going any faster than a few meters per second will fall through it.
Every mesh has a mesh collider (The landmasses, which are the things that you can collide with,are two meshes.)
I am using this gravity script.
This planet weighs 1e+6, so not a lot for a planet.
The center of the planet is at origin, but even if the surface is at origin I still get this error. in-fact, it’s even weirder! I got sucked in, then spat out at thousands of kilometers per second!
And I just noticed that there is now a second, even stronger gravity point at origin for some reason, and nothing is creating it. But I’m pretty sure that’s not the reason why it’s all bugged, as it has been bugged like this even when there isn’t anything else in the scene aside from planet and player.
And this is a mesh collider issue, because if I put in a sphere collider, everything is fine.

Here is a pic of the planet, and here is a video!


Okay, that’s not in game, it’s even more beautiful in game.

One of your problems is, that those land sphere colliders have no thickness. Try changing the mesh so that it has thickness, or if you are on Unity 5.5 you can also inflate convex meshes.

As for the rigidbody of the player change
→ Interpolate to Interpolate
→ Collision detection to Continuous dynamic
This way it will interpolate collisions in between physics steps.

Another thing you can do is to go to the Physics Settings (Edit->Project Settings->Physics) and change the default contact offset to a larger value (Try something like 1-100 to see if that has the desired effect). Changing this value also means, that collisions will happen before the player is really touching the ground.

Last but not least I guess adding a simple sphere collider to earth would be the easiest solution. I don’t know what you want to achieve with the water thingy, but the sphere collider is really cheap performancewise and would make sure that you don’t glitch through the mesh.

As for the rigidbody of the player change
→ Interpolate to Interpolate
→ Collision detection to Continuous dynamic

This works wonderfully, thank you so much!
As long as I’m not going light speed, I’ll still collide with it.

adding a simple sphere collider to earth would be the easiest solution

The thing is, this planet is not perfectly smooth, it has hills and valleys. At some points it can drop down 6 or so kilometers. so that won’t work