Download Chapter 25.1: Exploring the Solar System and 25.5 The Origin of the

Chapter 25.1: Exploring the Solar System
& 25.5 The Origin of the Solar System
GeoCentric vs. Heliocentric Model
Geo = “Earth”
Centric =“in or at the Center”
Helio = “pertaining to the
Sun”
Aristarchus developed a
heliocentric model---
Most Ancient Greeks
thought that the EARTH • In this model, Earth
and the other planets
was the center of the
revolve around the
Universe.
SUN.
• In the 1500s, with
*In a GEOCENTRIC Model,
evidence supported by
Earth is stationary while
Copernicus and
other objects in the sky
Galileo, this
move around it.
Heliocentric Model
was proven Correct!
Heliocentric Evidence…
• The apparent motions of the sun, moon, and
stars result from Earth’s daily rotation on its
axis.
Planetary Orbits
What keeps the planets in their orbital
paths?
*Isaac Newton realized that the Sun
Exerts a Gravitational Force on the planets that
keeps them in orbit. Otherwise, the planets’
Inertia would cause them to fly off into space*
GRAVITY and INERTIA combine to keep the
planets in orbit around the SUN!
25.5 The Origin of
the Solar System
The
Nebular
Theory
This is the generally accepted
explanation for the
formation of the Solar
System.
*The Nebular Theory states
that the solar system
formed from a rotating
cloud of dust and gas.
A large, thin cloud of dust
and gas like the one that
formed our solar system is
called a Solar Nebula.
Nebular Image
Nebular Theory Continued….
• According to the Nebular Theory, the solar
nebula formed from the material expelled by
previous stars.
• Nearly all of the mass of the solar nebula, about
99.9% became concentrated near the center –
where the SUN would form in this region.
• 10 million years after this solar nebula formed,
Nuclear reactions began and OUR SUN was
born!
Additional Points about the
Nebular Theory
• It also explains how
the planets could
have formed--• The theory provides
Balls of dust collided
an explanation for
and grew larger &
the Current motions
larger and eventually
of the Sun, Planets,
these asteroid-like
and most Moons.
bodies combined to
form planets!