We're travelling to other star systems via brachistochrone trajectories. We'd be travelling at a significant fraction of the speed of light. And yes significant relativisitc effects only take place at speeds like 0.8c or 0.85c, still I think it would be pretty cool if it simulated effects of time dilation. relativistic doppler effect would also be pretty nice, like when you're travelling at those speeds the stars in front of you would be very blue, and the stars behind you would appear very red (i.e blueshift and redshift) Another and the only other thing I could think of is relativistic kinetic energy, but I don't think the physics engine can handle stuff like two things colliding at 0.8c or even a rocket colliding with a planet at those speed lol.
