Earthquake? Tremor?

     At exactly 5 a.m. today, I walked into my kitchen and there right in the middle of the floor was a white disc, about a foot in diameter. Kind of like a flying saucer, or a frisbee. I had no idea what it was or how it got there. A little eerie, since no one else had been in the house, that I knew of anyway. Not until I happened to look up did I see it was the light fixture that had fallen off. Also a little mysterious as that bulb rarely burns out and it's been a number of years since that light cover has been removed.