Ask A Scientist General Science Archive

Question:  What is lightning?  How is it caused?
 hasinoff

Answer:
Lightning is the result of the separation of electical charges
that can occur in clouds.  The process is not completely
understood, but negative ions collect near the bottom of
clouds and positive ions near the top.  The positive and
negative ions attract each other.  If enough of them collect
in a cloud lightning will strike between the top and the
bottom of the cloud.  The negative ions at the bottom of the
cloud also attract positive charges in the earth's surface.
This causes lightning strikes between the ground and the
cloud.
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