Post on 17-Jan-2016
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
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
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