Kepler's Laws Orrery

Also called

kepler's laws · keplers laws · orrery · law of orbits · law of areas · law of periods · ellipse · focus · perihelion · aphelion · equal areas in equal times · T squared proportional to a cubed · planetary motion · comet orbit · halley's comet · solar system model · gravitation · केप्लर के नियम · ग्रहों की गति · दीर्घवृत्त

Topics

• Kepler's first law: every planet moves on an ellipse with the Sun at one of its two foci.
• An ellipse is the set of points whose distances from the two foci add to the same total, the length of the major axis.
• Kepler's second law: the line from the Sun to a planet sweeps out equal areas in equal times.
• Equal areas mean the planet moves fastest at perihelion, nearest the Sun, and slowest at aphelion, farthest away.
• Kepler's third law: the square of the period is proportional to the cube of the semi-major axis, T² ∝ a³.
• A planet with 1.59 times the semi-major axis of another has 4 times the a³ and so twice the period.
• Points plotted as T² against a³ for all planets lie on one straight line through the origin.
• A comet on a long ellipse spends most of its time far from the Sun and whips round it quickly at perihelion.
• Gravity provides these motions: the Sun's pull on a planet varies as 1/r², which gives exactly these three laws.

About this model

A GLB file of about 384 KB, shown in Lably's 3D viewer and, on a phone, placed in your room with AR. Credit: Model, science and animation: Lably (built procedurally with three.js; no downloaded meshes). | CC BY 4.0. Original geometry and animation made for Lably.

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