1. Johannes Kepler
(1571 – 1630)

2. Johannes Kepler Mathematically strong
Assistant to Tycho Brahe – used observatory and other instruments to measure more precisely than ever before (especially about Mars)
Discovered 3 laws of planetary motion

3. 1. The Path of Each Planet is an Ellipse
“The Law of Ellipses”
The sun is located at one focus
Nothing at the other focus of the ellipse
All of the planets orbit the sun in this pattern/shape

4. 2. Each Planet Revolves Equal Areas in Time
“Law of Equal Areas”
An imaginary line connecting the Sun to a planet will sweep over equal areas in equal time intervals
Planet’s speed is constantly changing!
Moves fastest when closest to Sun, slowest when farthest from Sun

5. 3. Length of Time and Distance are Proportional
“Law of Harmonies”
The length of time it takes a planet to orbit the Sun and its distance from the Sun are proportional
Comparison between motion characteristics of planets
Orbital Period (T)
Radius of Orbit/Distance from Sun (R)
T2/R3 ratio is the same for all planets
T2 = R3

6. Planet
Period (s)
Average Distance (m)
T2/R3 (s2/m3)
Earth
3.156 x 107 s
x 1011
2.977 x 10-19
Mars
5.93 x 107 s
2.278 x 1011
2.975 x 10-19
Planet
Period (yr)
Average Distance (au)
T2/R3 (yr2/au3)
Mercury
0.241
0.39
0.98
Venus
.615
0.72
1.01
Earth
1.00
Mars
1.88
1.52
Jupiter
11.8
5.20
0.99
Saturn
29.5
9.54
Uranus
84.0
19.18
Neptune
165
30.06
Pluto
248
39.44

7. http://unctv. pbslearningmedia. org/resource/npls12. sci. ess. eiu
dynamics-orbits-and-keplers-laws-nasa-planetary-sciences/