ASTRONOMY What is the frequency of a wave? Which type of wave has more energy, high or low frequency waves?

THE BIG BANG  Within fractions of a second the universe grew from the size of a pinhead to 2,000 times the size of the sun  By the time the universe was one second old, it was a dense, swirling mass of elementary particles

THE BIG BANG  Matter began collecting in clumps. As matter cooled, hydrogen and helium gases formed.

THE BIG BANG  More than a billion years after the initial explosion the first stars were born

THE BIG BANG  The big bang theory states that the universe probably began about 13.7 billion years ago with an enormous explosion.  Even today galaxies are rushing apart from this explosion.

DO CLUSTERS OF GALAXIES MOVE APART?  Astronomers know that most galaxies occur in groups of galaxies called clusters. These clusters appear to be moving away from each other in space  How do we actually know that the fabric of space is stretching? Where is the proof?

THE EXPANSION OF THE UNIVERSE: WHERE IS THE PROOF?  What does it sound like when a train is blowing its whistle while it travels past you?  The whistle has a higher pitch as the train approaches you  What does the train sound like as it continues past you and gets further away?  The whistle seems to drop in pitch  This is Referred to as Doppler Shift

DOPPLER SHIFT  Red Shift –  Blue Shift -

RED SHIFT  In 1929 Edwin Hubble made a remarkable discovery about light coming from galaxies  When a spectrograph is used to study light from galaxies beyond the Local Group, a red shift occurs in the light  What does this tell us?

WHAT DOES THIS TELL US?  Galaxies must be moving away from the Earth  Thus, if everything outside the local group is moving away from the Earth, the universe must be expanding

EVERYTHING IS EXPANDING?!?!?!  This leaves us with more questions about the universe then we had before  What could some of those questions be?

DOES EXPANSION = CONTRACTION? DOES EXPANSION = INFINITE EXPANSION? DOES EXPANSION = AN EVENTUAL STOP?

GALAXIES  Galaxies – a large group of stars, gas, and dust held together by gravity  We live in the milky way galaxy, consisting of over 1 trillion stars  Galaxies are separated by huge distances, most times hundreds of millions of light years  Milky Way belongs to a cluster referred to as the local group which contains about 45 galaxies of various sizes and types

GALAXY TYPES

THREE MAJOR TYPES OF GALAXIES  Spiral Galaxies  Have spiral arms that wind outward from the center  Arms consist of bright stars, dust, and gas  The milky way galaxy is a spiral galaxy  It takes our solar system 225 million years to orbit the center of the milky way

THREE MAJOR TYPES OF GALAXIES  Elliptical Galaxies  Shaped like large, three dimensional ellipses  Many are football shaped while others are round  Some are so large multiple milky way galaxies can fit inside them

THREE MAJOR TYPES OF GALAXIES  Irregular Galaxies  Have many different shapes  Smaller then other types of galaxies

ON A WHITE SHEET OF PAPER  Using your textbook and your notes from todays class and previous classes:  On the front of the paper:  Draw a picture of what you visualize the “Big Bang” would have looked like The drawing should be no more then a half of a page  Write a detailed paragraph of what happened during the big bang and the moments shortly following under your picture.  On the back of the paper:  Draw all three galaxy types and place a name above each one of their pictures matching their type.  Write a brief description of each galaxy type below the picture.