Just a point of clarification... Sam, as an astronomer, is familiar with a tool used many decades before for observing distant objects, called a camera obscura. It works very much like an overhead projector, but it has no light source of its own. A lens and/or prism receives an outside image and projects it upon a flat wall of a darkened room using the light from the outside image. See http://brightbytes.com/cosite/what.html
On several occasions in the film when the girlfriend and the boyfriend are moving about in the other apartment, you will notice Maggie or Sam turning the camera obscura to follow the action, and it moves the projected image.
The use of this astronomical tool adds much needed depth to the Sam character, and the "projector" is perhaps the only metaphysical allusion in the whole film.
On several occasions in the film when the girlfriend and the boyfriend are moving about in the other apartment, you will notice Maggie or Sam turning the camera obscura to follow the action, and it moves the projected image.
The use of this astronomical tool adds much needed depth to the Sam character, and the "projector" is perhaps the only metaphysical allusion in the whole film.