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Name: Ryan S.
Status: student
Age: 14
Location: N/A
Country: N/A
Date: 2001-2002


Question:
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?


Replies:
Ryan,

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
Physics Instructor
Illinois Central College



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