Name: Ryan S.
Gravity is always an attractive force. Is it conceivable
that there might be such a thing
as repulsive gravitational force? How would such a force react with other
objects? What would it be called?
Forces that comes to mind as being both attractive and repulsive are
electric force and magnetic force. These both have the property of being
based on two kinds of electric charge: positive and negative. How a
positive charge responds to electric and magnetic force is exactly opposite
to how negative charge responds. Like charges repel each other, and
opposite charges attract.
Gravity is based on mass. Two masses attract each other with gravity. I
suspect repulsive gravity would require a second kind of mass. As like
masses attract, opposite masses would repel. On the level of the universe,
this might cause all the "positive" mass to join together into one big set
of galaxies at one location with all "negative" mass pushed away, joining
together somewhere else. If such negative mass does exist, we are unlikely
to see it.
Dr. Ken Mellendorf
Illinois Central College
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Update: June 2012