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AST-L25-ch1920__3 - final exam Today we will discuss...

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1 final exam!!! Today we will discuss Cosmology and the Big Bang Wednesday we will finish the Big Bang, have a short discussion of Life in the Universe, and review for the final exam Remember: the Beginning & End of Time Today’s Lecture: purpose & goals AST 1002 Planets, Stars and Galaxies 1) The “Beginning” 2) The Age of the Universe 3) The “End of Time” 4) Life in the Universe 5) Review for Final Cosmological Redshift We now know 3 kinds of redshift Doppler shift due to motion Gravitational shift due to distortion of space-time by mass Cosmological shift due to stretching of space not due to relative motion as space stretches, the wavelength stretches and becomes longer
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2 Thinking Back in Time We can calculate the age of the Universe using Hubble’s Law I f H o = 70 km/(s . Mpc), what i s the age o f the Un i verse , T Hubble ? v = H 0 x d d = v / H 0 But distance = rate x time (the tim e here is how long the expansion has been going on The Age of the Universe ) t Hubble = 1/ H 0 t Hubble = 1/ H 0 ( Mpc ) = 1 sec . Mpc 70 km 10 6 pc ( pc ) 3.26 l.y. ( l.y. ) 10 13 km = 3.26x10 19 sec 70 = 4.657x10 17 sec ( 3600sec ) 1 hr ( 24 hr ) 1 day ( 365.25day ) 1 yr = 1.475x10 10 yr = 14.7 Billion Years!! At the Beginning Originally all the energy (and matter) of the Universe was condensed into an incredibly small region MUCH smaller than the size of a proton Energy , matter , space and time were all very different than today what we call matter was then almost entirely energy (gamma-ray photons) need a new “theory of everything” to understand not yet possible 11-dimensional space??? (models are very weird) During early expansion, space-time and gravity became separate from energy and mass particles and antiparticles were being created from energy and annihilating into energy all the time Glow of the Universe The early Universe was very hot and dense glowed with blackbody radiation but so dense the light kept getting absorbed ( opaque ) Eventually the Universe cooled
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