My understanding is that in a true vacuum light will not be reflected or bent by particles. However, due to gravity bending space time itself, light will follow the curvature of space. It would depend on the observer if the path if light is straight. If you look at the light passing by, it would not be straight under influence of gravity. If light itself is the observer, it will travel in a straight line :)
In the case of gravitational lensing the observer is looking at light coming in. An outside perspective.
There is no perfect vacuum, even in deep space. In the space of our Solar System, there is on average 5 atoms in every cubic centimeter. In interstellar space, there is on average 1 atom every cubic centimeter. In intergalactic space, there is on average 1 atom every 100 cubic centimeters. It’s a gradient, but much like the perfectly straight lines and flat planes in the original question, perfect vacuum is a theoretical construct that is impossible to achieve in our reality.
Unless the light is in a vacuum like space
I asked my good friend gravitational lensing about light in space, and they said that light can go and get bent
My understanding is that in a true vacuum light will not be reflected or bent by particles. However, due to gravity bending space time itself, light will follow the curvature of space. It would depend on the observer if the path if light is straight. If you look at the light passing by, it would not be straight under influence of gravity. If light itself is the observer, it will travel in a straight line :)
In the case of gravitational lensing the observer is looking at light coming in. An outside perspective.
Light bends in space all the time. Our sun has enough gravity to bend light.
There is no perfect vacuum, even in deep space. In the space of our Solar System, there is on average 5 atoms in every cubic centimeter. In interstellar space, there is on average 1 atom every cubic centimeter. In intergalactic space, there is on average 1 atom every 100 cubic centimeters. It’s a gradient, but much like the perfectly straight lines and flat planes in the original question, perfect vacuum is a theoretical construct that is impossible to achieve in our reality.
Space is not empty