They are a teaching aid for showing students how the various planets revolve and rotate. With an Earth/Moon/Sun system model you can answer all these questions by just turning the handle.. 1  Why we have day and night.  What a year is.
The precursor of any lightning strike is the polarization of positive and negative charges within a storm cloud. The tops of the storm clouds are known to acquire an excess of positive charge and the bottoms of the storm clouds acquire an excess of negative charge.
Lightning is a sudden high-voltage discharge of electricity that occurs within a cloud, between clouds, or between a cloud and the ground. Globally, there are about 40 to 50 flashes of lightning every second, or nearly 1.4 billion flashes per year.