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.
Positive lightning is less common than negative lightning, and on average makes up less than 5% of all lightning strikes. A Bolt from the blue lightning strike which appears to initiate from the clear, but turbulent sky above the anvil cloud and drive a bolt of plasma through the cloud directly to the ground.