I have a 100+ year old house with updated electrical on the lower level. I also have a motion sensor alarm that I arm every night as I go to bed. My lights down stairs have been turning on during the night. I have no explanation for it. I would like to reject the notion of a ghost as I've lived here for 3 years and never had any issues until the recent lighting events. Can anyone explain how these lights can be turning on?

Fish... you need to start your own thread... not jump on this one. And when you do, supply as much info as you can... type of switches, lights, any electronics involved... etc.

Separated from another thread to it's own thread.

Motion sensors can be affected by cold or warm drafts, as one possible reason.

As MB asked, provide more detail of the product, its location, etc.