@Erimitus Said
Lets make the light battery operated and inside the sealed container.
Lets make the container a cylinder in open space somewhere between galaxies so there is little if any gravity.
Lets make the cylinder 300 million meters long with a mirror at each end.
A light pulse is emitted in front of mirror(A) at one end of the cylinder and lasts for one second.
Then the light source moves out of the way of mirror(A)
The light pulse travels the 300 million meters in one second and strikes mirror(B) at the other end of the cylinder.
Then the light pulse is reflected back at mirror(A)
When the light pulse reaches mirror (A) it is reflected back at mirror (B)
Will the light bounce back and forth between the mirrors for eternity?
I see what you're getting at. To be honest I know little about physics to that extent and outer-space never interested me because I thought someone was telling a porky.
I would assume, as told, the sun is a burning ball of gas and the light emitting from it lasts as long as that ball of gas has left to burn.
We only benefit from it because Earth is relatively close to the sun where the outer reaches of space would be pitch back because the rays would fade when that far away.
I've also heard that space is a vacuum but that tends to conflict with what I was told when I was a kid because I would assume in order for it to be such you have to add walls to outer-space and claim that space was not infinite but rather came to a rude halt in all four directions.
I've also considered that the best way to hide a city is to begin raising an Atlante-an society to a "world" that has no accurate history (or person) willing to give away the true name of the habitat.
In such an instance the clouds could be foam build-up while we rest precariously under a transparent ceiling as the land above is getting torched by whatever 'the son' turns out to be.
And I believe you had mentioned the stacked tortoises...