1. 4/23 & 4/24 - 8th Grade Agenda
Learning Objective: Learn about early model of the solar system
Collect HW: Reading & Notetaking p.233 – 234
Video: When we left Earth
Textbook Reading: p
HW: Reading & Notetaking p.236– 237

2. Daily Reflection
Prompt: Write 3 facts about early model of the solar system (2000 years ago)

3. Until about 500 years ago, people thought that the Earth was the center of the universe
What made them come to this conclusion?

4. Even the Greek Astronomers thought the heavens rotated around the Earth
In A.D. 140, Ptolemy had to explain the wobble in the planet’s motion by having the planets move in a circles with in a circle

5. Ancient Greeks believe in a geocentric system
They wrongly believed that the Earth was at the center of the Universe.
This view remained the accepted view until 1600.

6. What kind of a model did Copernicus propose in early 1500s?
Heliocentric Model with the Sun at the center
But most people still believed in the Geocentric model

7. Heliocentric system was accepted until the 1660s
In a heliocentric system, earth and the other planets orbit around the sun.
Copernicus first proposed the heliocentric model in 1543.
People (Galileo & Giordano Bruno) were jailed and burned for proposing the Heliocentric system.

8. What key observations did Galileo make in 1600s?
Moons of Jupiter
Phases of Venus just like the moon

9. How did Galileo’s observations help convince others that Copernicus’s was correct?

10. Kepler discovered that orbit of each planet is an e______ instead of a c______
llipse
ircle

11. Kepler’s Laws Kepler’s 1st Law: Planet’s obit is an elipse
Kepler’s 2nd Law: Planets move faster when it is closer to the sun
Kepler’s 3rd Law: Planets closer to the sun orbit the sun faster than planets that are farther from the sun

12. In what units do we measure distances around our solar system ?
AU (Astronomical Unit)
1 AU = Distance between the sun and the Earth
1 AU = 93 Million Miles

13. In what units do we measure distances between the stars ?
Light Year
Light travels about 186,000 miles per second
1 Light Year = 65,000 AU
1 Light Year = 6 Trillion Miles
Closest Star (Alpha Centari) is about 4.3 Light Years away

14. How much of the solar system’s mass is in the sun?
About 99.8%
Most of the mass of the solar system is in the sun

15. How does the sun generate it’s energy?
Nuclear Fusion
Hydrogen Atoms join together to from Helium
Some of the matter is converted into energy
The Sun’s core reaches about 15 million degrees Celsius