Standing on the patio I was looking at the big dipper around 12:03am. There were two planes, both at high altitude one lower than the other. I could hear the distinct humming of their engines as they displaced air and they both had blue strobe lights which identified them as planes. Then I noticed another flying object at very low altitude. It consisted of three faint lights in a triangular formation. I can't estimate the altitude but using my house as a point of reference it was considerably close to the ground. It made no sound as it smoothly glided from south to north. . It moved at a constant speed until I lost sight of it in the dark sky. No humming of jet engines or a sound of propellers. It had no condensations on its trail. As it flew over, it felt as if it had a hollowed center but it was not transparent, yet I could not make the outline of its body. I cannot speculate on its exact dimensions as I had no point of reference in the sky, yet it seemed slightly smaller than a one-car garage as it flew over mine. I have seen drones flown around this time before but this was much larger than a drone and it lacked the whizzing sounds of propellers. I would like to add that I am an engineer and I believe there is a scientific explanation for everything but just cannot wrap my head around this one.