Astronomy Chapter 18.1

Astronomy People in ancient cultures used the seasonal cycles to determine when they should plant and harvest crops. They built observatories to study the night sky. Over time, the science of Astronomy (the study of the Universe) was developed.

Modern Calendar The modern calendar is based on the observations of bodies in our solar system. Day –Amount of time it takes Earth to rotate once on it’s axis Month –Amount of time it takes the moon to orbit once around the Earth Year –Amount of time it takes the Earth to orbit once around the Sun

Ptolemy Claudius Ptolemy: –Greek Astronomer – (140 A.D.) –Believed in an Earth- Centered Universe –Stated that the other planets and the sun revolved around the Earth –Helpful b/c he predicted motions of planets better than any other theory of the time

Ptolemy

Copernicus Nicolaus Copernicus: –Polish Astronomer –lived –Thought the sun is at the center of the Universe –All planets, including Earth, orbit the sun –Very controversial & caused major changes in science and society

Copernicus

Brahe Tycho Brahe –Danish Astronomer –Lived –Stated the Sun and Moon revolve around the Earth –But other planets revolved around Sun –Detailed astronomical observations –Very precise observations of planets and stars.

Brahe

Kepler Johannes Kepler –Lived –Brahe’s assistant –Did work on orbit of Mars (because he and Brahe did not get along) –Data ended up helping him prove that all the planets revolve around the sun in elliptical orbits –Stated the three laws of planetary motion, still in use today

Kepler

Kepler’s laws of planetary motion 1 st law: planets travel in elliptical orbits with sun at one focus 2 nd law: equal area law – 3 rd law: harmonic law P 2 = D 3

Galileo Galileo Galilei – –Italian scientist –One of the first to use a telescope Discovered:  craters and mountains on the moon  4 moons of Jupiter  Sunspots  Venus’s phases

Copernicus and Galileo

Kepler and Galileo

Newton Sir Isaac Newton – –English Mathematician and Scientist –Proved that all objects attract each other through gravitational force. –Force of Gravity depends on Mass and Distance of objects. –Gravity holds moons and planets in orbit. –Linked gravity & laws of planetary motion

Newton

Modern Astronomy Two milestones in modern astronomy –1. Invention of the telescope –2. Discovery of gravity Before the 1920’s, astronomers believed that our galaxy, the Milky Way, included every object in space.

Measuring the scale of the solar system

Hubble Edwin Hubble –American Astronomer –Proved that other galaxies existed, confirming that the universe is bigger than the Milky Way –DID NOT develop the Hubble telescope. It was launched in 1990, Hubble died in

Hubble Telescope

18.1 Read p. 554 – 557 Review: pg 557, #1-8 (in your notebook) Raise your hand when finished, I will check and put in the gradebook.