I took a few shots yesterday night while the roomies cooled down by the Herb Garden adjacent to our unit.
If the rising and setting of the Sun doesn't cut it for you, this is further proof that the Earth is spinning.
Star trails occur because of the Earth's rotation.
This 30min (max) exposure created a lot of noise at ISO 200 (lowest). The original image was grainy with a slight washed out look while some trails weren't obvious because the stars weren't bright enough. Oddly enough, the trails emitted different hues (orange, blue, white).
I suspect the soft contrasts came from fluorescents around the garden area which might explain the noise. I'm going to have to find darker spots next time. Goes against my instincts though. I shouldn't be hanging out in the dark even if I have company. Muggers here are ruthless, so I've been told.