Big Bang Theory PPT - Weeblygharibess.weebly.com/.../6/13466856/big_bang_theory_ppt.pdf ·...

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Unit  1:  History  of  the  Universe  

Lecture  1:  Big  Bang  Theory    

Cosmology  

•  Study  of  the  universe  

–  It’s  nature,  origin,  and  evolution    

Big  Bang  Theory  

•  Humans  have  always  gazed  towards  the  stars  

and  wondered  how  the  universe  developed  

into  what  it  is  today.    

•  One  of  the  most  famous  and  widely  accepted  

models  for  the  universe’s  development  is  the  

big  bang  theory  

Origin  of  Big  Bang  Theory  

Big  Bang  Theory      

True  or  False?  

•  Big  Bang  Theory  describes  the  origin  of  the  universe  

•  The  Big  Bang  was  an  explosion    

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Big  Bang  Theory  

•  Describes  an  expansion  of  space  itself  while  

gravity  holds  matter  in  check.    

Outward  Expansion  

•  The  Universe  has  two  opposing  forces  

– Force  of  Gravity    

– Momentum  of  expansion  

Rate  of  expansion?  

•  Rate=  speed  at  which  something  moves=  

distance/time    

•  When  rate  is  known  :  

– Can  calculate  time  since  expansion  started  

– Which  leads  to  age  of  the  universe    

Hubble  (Expansion)  Constant  

•  Also  known  as  H  

•  If  known,  then  the  age  of  the  universe  can  be  

determined  

Age  of  the  Universe  

Best  value  of  H  by  Hubble  Space  Telescope  data  +  

 Data  on  the  cosmic  background  radiation  =  

 Age  of  the  Universe  =  13.7  billion  years  

An  Accidental  Discovery  

•  1965    

•  Scientists  heard  constant  

background  noise  in  their  

radio  antenna    

•  Noise=  weak  radiation  

Cosmic  Background  Radiation  

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An  Accidental  Discovery  

•  https://www.youtube.com/watch?

v=hcds5Ob59Dg  

Cosmic  Background  Radiation  

•  Came  from  all  directions  in  space  and  

matched  with  another  emitting  object  having  

a  temp.  of  2.725  K  (-­‐270°C)    

•  So  the  radiation  is  leftover  from  the  Big  

Bang...  

Map  of  CBR  

Cosmic  Pie  Modern  Day  

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Outcomes  of  the  Universe  

•  Open    

–  Expansion  never  stops  •  Gravity  can’t  stop  it  

•  Closed  –  Expansion  stops  –  Starts  to  contract  

•  Flat  –  Expansion  slows  to  a  halt  in  an  infinite  amount  of  time  

Redshift    

•  Another  way  we  know  that  the  Universe  is  

expanding!!!  

•  Redshift  describes  how  light  changes  as  

objects  in  space  (stars  and  galaxies)  move  

farther  

•  http://youtu.be/FhfnqboacV0?t=11s  

The  Hubble  Distance  -­‐  Redshift  Relationship