7c big bang theorysjutsscience.weebly.com/.../7c_big_bang_theory_notes.pdfthe big bang theory •...

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THE BIG BANG THEORY

WHO REMEMBERS DOPPLER SHIFT? •  The Doppler Effect is the perceived change in wavelength of a wave that is

emitted from a source that is moving away or toward an object.

RED SHIFT •  When objects move away from us, they appear red •  When objects move toward us they appear blue •  Observations made in the early 1900’s revealed that most of the galaxies we

can see have Doppler shifts toward the red end of the spectrum •  The light waves are being stretched

•  The Earth and the source of light are moving away from each other

HUBBLE’S LAW •  Edwin Hubble wanted to explain why the galaxies appeared to be moving

away from us. •  Hubble realized that dimmer galaxies were most likely farther away from us

than were brighter galaxies. •  He tried to find a relationship between the distance to a galaxy and their red

shift. •  He found that galaxies exhibiting the greatest red shift are the farthest away

•  Greater red shift = greater speed

HUBBLE’S LAW •  Galaxies are retreating from us at a speed that is proportional to their

distance •  i.e. the farther away galaxies are, the faster they are moving away from us

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THIS MEANS THE UNIVERSE IS EXPANDING!

THE BIG BANG THEORY?

THE BIG BANG THEORY

•  The Big Bang Theory says that once the entire universe was confined in a hot, dense, supermassive ball

•  Approximately 13.7 billion years ago, a “violent explosion” occurred, hurling the material in all directions

•  Everything in our universe came from that ball

EVIDENCE OF THE BIG BANG

•  Red Shift – Hubble’s Law •  Cosmic Background Radiation •  Radio signals from all over the universe, could be

leftover from Big Bang (H-pg 848)

MORE EVIDENCE FOR THE BIG BANG •  Cosmic Microwave Background radiation (CMB’s) : the existence of an

isotropic radiation bath that permeates the entirety of the Universe •  In 1964, two young radioastronomers, Arno Penzias and Robert Wilson,

accidentally discovered the CMB using a well-calibrated horn antenna. •  They were trying to determine what was causing static in telephone

lines. They worked for Bell Telephone company. •  It was soon determined that :

•  the radiation was diffuse, •  emanated uniformly from all directions in the sky, •  had a temperature of approximately 3 Kelvin (2.73K).

COSMIC RADIATION BACKGROUND

Stephen Hawkins - Cosmic Background Radiation

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WHAT HAPPENS AT THE END?

•  Idea One: •  Universe expands forever •  Stars burn out, leaving many black holes and other matter

•  Idea Two: •  Universe eventually starts contracting (coming back

together) •  Galaxies collapse on each other forming the “Big Crunch”

•  Idea Three:

•  Steady State Theory proposes that the universe looks the same as it always has.

•  Right now, astronomers believe that Idea One is most likely…

SOURCES •  http://school.discoveryeducation.com/curriculumcenter/universe/activity2.html

•  http://aether.lbl.gov/www/science/cmb.html

•  http://space.about.com/od/astronomybasics/a/Origin-Of-The-Universe.htm