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# PCS 181 class 4.docx

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School
Department
Physics
Course
PCS 181
Professor
Margaret Buckby
Semester
Winter

Description
PCS 181 PCS 181 Thursday, January-24-13 Class 4 Hubble and Humason’s Findings  All galaxies are red shifted and are receding from us Hubble’s Law:  Radial velocity of a galaxy is directly proportional to distance  Farther galaxies are receding faster  Vr α d  Vr = Hod  D = Vr/Ho  Ho = Vr/d 1. The universe is expanding…space itself is expanding Cosmic Microwave Background Radiation (CMB)  1965 Arna Penzias and Robert Wilson  Radio astronomers at Bell Labs NJ  They were in charge of signal of first communications satellite (Telstar)  Detected a persistent radio hiss from all directions in the sky  This had a wavelength of λ = 1.063*10^-3m  They found the temperature of the source  This was determined using the Wein formula CMB Temperature  The Wein formula  T = (0.0029m.k)/ (λdom)  T = 2.728±0.004k  T = 3k = CMB  This supported the big bang theory  This temperature is the resonate heat left over from the big bang  Proving that some event must have heated the universe Cosmology  Penzius and Wilson discovered the remnant heat from the birth of the universe 1. The universe is expanding (Hubble and Humason) Page 1 PCS 181 2. There was a heat event at the beginning of space and time as proven by the CMB (Penzias and Wilson) CMB Confirmation  1989 Cosmic Background Explorer Satellite (COBE) was launched in order to figure out the temperature of space  Provided an above atmosphere measurement of CMB  Confirmed that the CMB is 2.7±0.004k COBE Measurements Page 2 PCS 181 Further CMB Confirmation  2001: Wilkinson Microwave Anisotropy Probe (WMAP) was launched  It has a 30x greater resolution than the COBE satellite  It confirmed the temperature of the CMB The Cosmological Principle  The universe is: 1. Isotropic: looks the same in all directions 2. Homogeneous: matter is approximately evenly and uniformly distributed. Every region is the same as every other region 3. Universal: the laws of physics are the same everywhere  Any theory of cosmology cannot exclude these three principles  4 statement used to be that “the universe never changes”  There was a discovery two weeks ago which found that 20% of the universe is in one spot  This discovery is called Large Quazar Group  It is challenging The Cosmological Principal (1 and 2) The History of the Universe Time after the Big Bang: Event: 1. +
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