Kepler's Laws

Kepler's Laws

Mr. Mendoza

How do Kepler’s laws describe Earth’s orbit?

Beginnings

Johannes Kepler, working with data painstakingly collected by Tycho Brahe (from 1576-1601) without the aid of a telescope, developed three laws which described the motion of the planets across the sky. 

Kepler’s First Law

Law of Orbits: All planets move in elliptical orbits, with the sun at 1 focus.

An ellipse is an oval shape centered on 2 points instead of 1 point.

The orbital period of a planet is how long it takes for it to travel a complete orbit around the Sun… a year!

Perihelion

Aphelion

Kepler’s Second Law

Law of Areas: A line that connects a planet to the Sun sweeps out equal (=) areas in equal (=) times.

Earth sweeps out a longer path when it is closer to the Sun.

Earth moves fastest when it is closest to the Sun

Kepler’s Third Law

Law of Periods: The square of the orbital period of any planet is proportional to the cube of the semi major axis of its orbit. 

P² = a³ If you know the distance of a planet to the Sun, you would be able to figure out its… orbital period. Basically… The closer a planet is to the Sun, the shorter its orbital period is. 

https://www.youtube.com/watch?v=AKbfR5KHUm4

Multiple Choice

Which term describes the time it takes for Earth to complete one circle around the sun.

• Rotation
• Revolution
• Kepler's 1st Law
• Barycenter

Multiple Choice

Which term describes when the Earth spins on its axis.

• Rotation
• Revolution
• Kepler's Laws
• Precession

Multiple Choice

Kepler's first law states that the orbits of the planets are oval in shape or 

• ellipses
• perfect circles

Multiple Choice

A planet moves __________ when it is farthest from the sun.

• faster
• slower

Multiple Choice

Kepler's 2nd Law deals with 

• the shape of the planets' orbits
• the speed/area the planet travels 
• the length of time it takes the planet to orbit the sun

Multiple Choice

The place where a planet is farthest away from the Sun in its orbit around the Sun is called the

• aphelion
• perihelion

Multiple Choice

The place where a planet is closest to the Sun as it orbits the Sun is called the

• perihelion
• aphelion

Multiple Choice

Planets orbit the Sun in a shape called a(n)

• circle
• ellipse
• focus
• perihelion