5/6/15 1 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
Transcript
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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…
