### Why is the gravitational pull stronger on Jupiter?

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### Answer from Peter Huang, PhD

Assistant Professor

Education: Bachelor of Arts in Physics, Cornell University; Doctor of Philosophy in Engineering, Brown University.
Research Areas: Fluid Mechanics, Nanotechnology and Cancer
Website
: http://www.ws.binghamton.edu/huangloft/

While Sir Isaac Newton may not have been thinking about Jupiter more than three centuries ago, his most famous falling apple and Law of Universal Gravitation provide us with an answer to this question. Why does an apple fall straight down onto the ground when it detaches from a tree branch, instead of flying off into the space? According to Newton’s Law of Universal Gravitation, any two objects with non-zero mass (mass is a measure of the amount of matter within an object) are always attracted to each other, and the strength of this attraction depends on the (multiplication) product of the two masses.

Typically, when the mass of one object is very large while the other has very small mass, we observe the smaller object being pulled toward the larger object. In the case of the falling apple, the mass of the apple is much smaller than the mass of the Earth. Therefore when the apple is no longer held by a tree branch, the attractive gravitational force brings the apple to the Earth. For a person observing this process nearby, it is perceived as seeing an apple being pulled or falling to the ground.

Few objects in the universe have masses larger than planets and stars. Jupiter, the largest planet in our solar system, has a mass that is 318 times that of the Earth. Consequently, the gravitational pull of Jupiter is a few hundred times larger than the gravitational pull of the Earth. One can imagine that a lot more stuff falls onto Jupiter from space than onto the Earth.

Last Updated: 9/18/13