What Makes A Game A "Space Sim" Game?

[Alien]

So I am wondering, what is it about a game that makes it a space simulation game? When you break things down, is it
A: The vehicles?
B: Is it the background being black? (FEII was famous for space being blue, yet it was still a space game).
C: Is it jumping from system to system?
D: Is it docking at space stations?
E: Is it buying and selling items?
F: Is it encountering aliens?
G: Is it combat?

Because while you might say a space sim has all those elements, NASA have a simulation or two, and yet it doesn't have all of those elements, yet is still a space sim game.

A space sim game is not much different to a flight simulator, except that space is black and a flight simulator has sky. Other game have aliens and combat, and sometimes combat with aliens, yet are not space sims.

So what is it that makes a game a "Space Sim"?

 

[AJW]

It takes place in space?

 

[Knightshark]

It's a space sim if you fly a space ship.

- - - Updated - - -

It takes place in space?

But that would make Endless Space or Sin of a Solar Empire also Space Sims.
They are Space Games in a broader sense.

 

[Smiffoo]

What Makes A Game A "Space Sim" Game?

Elite Dangerous does IMO

 

[milligna]

Someone calling it one without too much strenuous disagreement? Shrug.

 

[gazzareth]

The ability to fly imaginary space ships in imaginary space.....

G

 

[kilvenny]

Flying in an environment that gives a "believable" representation of space

 

[cpbtrading]

For a simulation of space, probably Space Engine. For a simulation of being in space and flying a space craft, then it would have to be Rogue System for me.