Hi I was wondering if someone could help me, I am busy making like a space station for my game and I would like to know what the dimensions of Earth are so that I can make it look realistic, when looking at earth from the station.
any help would be greatly appreciated.
Well, the Earth has a diameter of about 12730km. So you’d need something on the order of 127300 units wide.
But that probably isn’t feasible…
you can scale down as float e.g. 12.7300
Depending on your situation, if it’s just a space station and you’re not moving away from it then you could render the earth to a skybox.
To make something realistic you can use the Angular Diameter formula: Angular diameter - Wikipedia. You have only create something with the same angular diameter of the earth seen from your space station. So, in practice, you don’t need to create something big far far away, but, for instance, something 100 times smaller but 100 times more close.
However, this value usually creates very small objects. In game you have to emphatize a lot the angular diameter in order to have something with a big emotional impact. 
127 300 units is perfectly doable in the engine.
However 12730 KM translates to 1,273,000,000 Unreal Units, and that is never going to work no
If earth is just a backdrop for your space station you make it whatever size feels right. You won’t get a realistic size in (space is so super huge) so you will need to fake all of this anyway.
Thanks for all the replies I really appreciate it, ok so after I have created the planet how do I render the lighting should I put the huge mesh also inside a lightmass importance volume?
No, you might not even need to lightmap it. It depends how you will do your space scene, but I would probably do it full dynamic lighting only + part of the lighting handled via a complex material setup. Possibly all of it entirely done via the material (unlit).
That is not that easy if you are new to the engine though. But definitely don’t make a huge lightmass importance volume. That volume should cover only your actual space station.
Well I was planning on making the stars emmisive and give them some glowing effects for some realism, at the moment i’m only concerned about the planet, I will test out it with full dynamic lighting only and see how that works out. thanks for the tips.
The amount of light that reaches our solar system from distant stars is so small it isn’t worth having them cast light into the scene.
Yeah, but in UE4 emmisive doesn’t cast any lighting it just glows so i’m happy for that at least.