Earth Science Motion in the Solar System

Teach Motion in the Solar System to Earth Science Class

The Contribution of Tycho

Tycho Brahe

His Contribution

Tycho Brahe was a dornish man who built an astronomical observatory that did not include a telescope because it had yet to be invented. it did however contain several instruments used measuring positions of objects in the sky. Which he used to make very careful measurements of the position of the stars and planets over a period of 20 years.

Quick Check

  • Brahe used six instruments to measure positions of stars and planets

Johannes Kepler and the Laws of Planetary Motion

Kepler inherited all of Brahe's books of data which he used to develop three laws of planetary motion.

First Law of Planetary Motion

All planets move about the Sun in elliptical orbits, having the Sun as one of the foci (plural of focus)

Second Law of Planetary Motion

Each planet moves around the sun in such a way that an imaginary  line joining the planets to the sun will sweep over the areas of space in equal periods of time.  Because a planets orbit is an eclipse with the sun at one focus, the equal area law means that the speed at which a planet travels around the sun is not constant. Kepler determined that planets move more rapidly when they are closer to the sun 

Third Law of Planetary Motion 

Regarding the time it takes a planet to travel one orbit around the sun is its period the  law states that the period of a planet squared is equal to the cube  of its distance from the sun the formula is used to find the distance between the sun and a planet if the period is known or to find the period if the distance is known to use the formula the period must be in earth years  and the distance from the sun must be in astronomical units

Photos of the second and third laws

Quick Check

 = plural of focus

Galileo and the Telescope

Galileo and the Telescope

  • Galileo first astronomer to have telescope 

  •   Allowed him to see millions of stars that had never been suspected to exist 

  • See Crater Mountains on the moon

  • .Discovered four moons in orbit around Jupiter 
  • Gave support to the heliocentric system

Isaac Newton and theĀ  Universal Law of Gravitational

Isaac Newton

Isaac Newton 

  • Identified gravity was the force to keep the planets in motion 
  • Identified  the force of gravity between any two objects is directly related to the masses of two objects but inversely related to the square of the distance between the centers of the two objects

Law of Gravitation

  • Change in force = 1/distance^2
  • The speed of a planet increases when it is closer to the sun because the gravitational pull is greater at this time 
  • This law explains why mercury which is the closest to the sun has a higher speed in its orbit than any other planet 


  • Explained the long orbits of comets and provided proof they are apart of the solar system

  • Law of gravitation is now used to determine escape velocity

Newton's law of gravitation video

Quick Check

  • Orbits of comets apart of the solar system