Ch. 29 The Solar System

29.1 Models of the Solar System• Geocentric model: Earth centered model

developed by Aristotle– Did not fit observations such as retrograde

motion, the backward motion as some planets appear to reverse direction…..

• Epicycle model: Planets revolved around earth, but then planets moved in small chain like circles– This model considered the observations and

attempted to account for them!!!

Heliocentric Model

• Developed by Copernicus• Sun centered model of the Solar System– Planets orbit in the same direction– Each planet moves at a different speed and

distance from the sun

Kepler’s Laws: Ellipses

Kepler’s Laws: Ellipses

Kepler’s Laws: Ellipses

Kepler’s Laws

• First Law (Law of Ellipses): The orbits of planets are ellipses with the sun at one focus

Kepler’s Laws

• Second Law (Law of Equal Area): Planetary motion will cover the same area in a given unit of time.

• Third Law (Law of Periods): r3 ~ p2

The distance of a planet from the sun cubed (r3) is proportional to the square of the period (p2).

Period is defined as the length of time for one revolution around the sun.

Kepler’s 3rd Law

Notes

29.2 The Inner Planets

• Four Planets closest to the sun. • Terrestrial Planets : rock like planets, similar

to Earth– During the formation of the solar system,

materials with low boiling points where driven off.

MercuryPlanet closest to the sunPeriod: 88 daysLength of a day:

59 Earth Days!!!!• Minimal Atmosphere, and slow rotation =

HUGE temperature changes between night and day, 427C and -173 C

Venus

• Period: 225 days• Rotation: 243 days• Same size, mass, and density as Earth!• Dense Atmosphere (96% CO2)

Average surface temperature is 464C

Earth

• Third Planet from the Sun• Period: 365.24 days• Rotation: 23 hours, 56 minutes• Geological Activity• Because of the lower amounts of CO2, heat is

able to escape. • Average temperature: 14C

Mars

• Fourth planet from the sun. • Period: 687 days• Rotation: 24 hours, 37 minutes• 2 Moons• Geologically active– Volcanoes: Olympus Mons

• Water is trapped at ice caps

How old would you be on another planet???

In class math applications activity