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.538 - 544 HW: Reading & Notetaking p.236– 237

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

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

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

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.

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

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.

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

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

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

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

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

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

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

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