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

http://obs.nineplanets.org/psc/theman.html

Ptolemyhttp://player.discoveryeducation.com/index.cfm?guidAssetId=abd10202-edf5-434a-b525-03b3521088e9

Copernicus

• Nicolaus Copernicus:– Polish Astronomer– lived 1473 - 1543– 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

http://en.wikipedia.org/wiki/Copernicus

Copernicushttp://player.discoveryeducation.com/index.cfm?guidAssetId=abd10202-edf5-434a-b525-03b3521088e9

Brahe• Tycho Brahe

– Danish Astronomer– Lived 1546 - 1601– 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.

http://galileo.rice.edu/sci/brahe.html

Brahehttp://player.discoveryeducation.com/index.cfm?guidAssetId=abd10202-edf5-434a-b525-03b3521088e9

Kepler

• Johannes Kepler– Lived 1571 - 1630– 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

http://www-gap.dcs.st-and.ac.uk/~history/PictDisplay/Kepler.html

Keplerhttp://player.discoveryeducation.com/index.cfm?guidAssetId=abd10202-edf5-434a-b525-03b3521088e9

Kepler’s laws of planetary motion

• http://space.about.com/od/astronomybasics/tp/Keplers_Three_Laws.htm

• 1st law: planets travel in elliptical orbits with sun at one focus

• 2nd law: equal area law– http://physics.about.com/od/astronomy/p/keplerlaws.htm

• 3rd law: harmonic law P2 = D3

Galileo

• Galileo Galilei– 1564 - 1642– Italian scientist– One of the first to use

a telescopeDiscovered:craters and mountains

on the moon4 moons of JupiterSunspotsVenus’s phases

http://www-groups.dcs.st-and.ac.uk/~history/PictDisplay/Galileo.html

Copernicus and Galileohttp://player.discoveryeducation.com/index.cfm?guidAssetId=abd10202-edf5-434a-b525-03b3521088e9

Kepler and Galileo

Newton• Sir Isaac Newton

– 1643 - 1726– 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

http://www.horaz.com/horazyclopedia/Savoir/ARTICLES/Newton_Isaac.htm

Newtonhttp://player.discoveryeducation.com/index.cfm?guidAssetId=abd10202-edf5-434a-b525-03b3521088e9

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

• http://player.discoveryeducation.com/index.cfm?guidAssetId=abd10202-edf5-434a-b525-03b3521088e9

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 1953.

http://www.edwinhubble.com/hubble_bio_001.htm

Hubble Telescope• http://player.discoveryeducation.com/index.cfm?guidAssetId=abd10202-edf5-434a-b525-03b3521088e9

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.