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

http://astro.unl.edu/classaction/animations/light/dopplershift.html

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