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abstraction > hypothesis > theory > law > gravity law > Kepler's Law

Kepler's Law
subject			fact

Kepler's Law	has discoverer Johannes Kepler
	has definition One of three orbital laws formulated by Kepler
	is a kind of gravity law
gravity law	has domain gravity
theory	has validity correct or incorrect with caveats
	has author or reasearch group
	has date or a range of dates for which the theory was active

Kinds of Kepler's Law :

• Kepler's first Law (2 facts) - Each planetary orbit is an ellipse with the Sun at one focus.
• Kepler's second Law (3 facts) (law of areas) - Equal areas are swept out in equal times.
• Kepler's third Law (4 facts) (harmonic law) - The square of the period is proportional to the cube of the distance.