system
Given the following post, respond as if you're commenting on Reddit:
human
Why isn't it always light?

On a clear night, without light pollution, I can follow the path from Cassiopeia to the Andromeda galaxy, which appears as a dim smear of light. 
I assume that the closer I travel towards Andromeda (as impossible as that is) the brighter and more visible it will be and therefore it stands to reason that if I am *inside* Andromeda it will be incredibly bright. I mean, I'd be standing inside something which is giving off enough light to be seen from *Earth* in a whole other galaxy.

I assume our galaxy looks the similar from the perspective of an Andromedan so why does it ever get dark?
gpt
Suppose you had several floodlights on stands, at varying heights and set a distance apart but angled so that they’re pointing at the same place. A person walking up to the spot at which they’re pointing would, for awhile, just see a wide swath of very bright light. But at some point, they would get close enough to start resolving the individual points of light from the separate lamps, and eventually they would get beyond the point where the lights are pointing and thereby see the darkness behind and around the lights.

An imperfect metaphor, because stars emit lights in all directions, but it does illustrate the point: multiple light sources that are all emitting light towards you will blur as if they were one larger light source, but the light will individualize as you get closer and you can better resolve the actual space between them.