Kepler’s Laws

Johannes Kepler Mars’ orbit is not a perfect circle, it is elliptical The speed of Mars’ orbit changes Closer to sun = faster Farther away from sun = slower Lead to Kepler’s 3 Laws

Kepler’s 1 st Law The path of each planet around the sun is an ellipse with the sun at one focus

Kepler’s 2 nd Law Each planet revolves so that the “imaginary line” that connects it to the sun sweeps equal amount of area in equal time intervals Closer to sun = faster Farther away = slower

Kepler’s 3 rd Law The square of a planet’s orbital period is proportional to the cube of its distance from the sun Orbital period - how long it takes to orbit the sun Astronomical Unit (AU) – average distance between Earth and sun – 150 million km T 2 = d 3 ; T = orbital period, d=distance from sun in AUs

Kepler’s 3 rd Law T 2 = d 3 Mars has period (T) of 1.88 years (T = 1.88) (1.88) 2 = 3.54 d 3 = 3.54 d = 1.52 AU

Kepler’s Laws Tri-fold Use a tri-fold/brochure to explain Kepler’s 3 Laws. There should be no words other than labeling each 3 rd as to which law you are demonstrating. You may also use the formula for Kepler’s 3 rd law.

Orbits Barycenter – point between two objects where they balance each other When a moon orbits planet, or planet orbits a star, both bodies are orbiting around a point that lies outside of the larger body (star/planet) dinates_(astronomy) 0WEU g8 (2:59)

Orbits The Sun is NOT a stationary object. Sun moves as the planets tug on it Sun orbits the solar system’s barycenter

Moon and Earth Relationship Earth pulls on the moon, and moon pulls on Earth This “tugging” from the moon can cause the Earth to bulge

Moon and Earth Relationship Earth’s solids cannot give, however water does, causing our tides Two high tides and two low tides a day 12hrs and 25 min between two high tides

Moon and Earth Relationship Rise and fall daily due to Earth, Sun, and Moon interactions Since earth is rotating, we experience two tides each day

Moon and Earth Relationship Spring Tides – when moon and sun interact together and form extreme tides. Occurs during full and new moons

Moon and Earth Relationship Neap Tides – moon and sun pull at right angles and cancel each other out...very weak tides fe9haMU NAA-9UE