The Universe

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  • Created by: Hannah
  • Created on: 04-05-15 14:43
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  • The Universe
    • The Structure
      • The Solar System
        • Part of a GALAXY called The Milky Way
          • Spiral galaxy
          • There are billions of stars in a galaxy and billions of galaxies in the Universe
        • Sun is in the centre, holding everything else in orbit.
          • Around = Planets, Moons, Asteroids, Comets etc.
      • Life Cycle of a Star
        • Slightly denser areas of the universe have a slightly higher gravitational pull.
          • This pulls in material, making it denser and giving it a greater gravitational pull, so it pulls in more material.
            • As it collapses, temp increases as PE --> KE, star ignites and is now a PROTO STAR
              • Once hot enough, FUSION can occur, burning hydrogen to helium
                • This creates radiation pressure, when radiation pressure = gravitational force the star is stable
                  • Once there is no hydrogen left to burn, star collapses in and reignites burning helium etc.,  Red Giant= much larger and cooler
                    • Sheds outer layers of gas, eventually contracting to form a white dwarf
      • The Scale of the Universe
        • One astronomical unit is the distance from the earth to the sun 
        • A light year is the distance travelled by light in a year. Using distance = speed x time
        • Parsec Distance of object who's parallax is 2 seconds
      • Oblers' Paradox
        • The sky is dark at night, meaning there is a FINITE number of stars.
          • 1)The universe is not infinite/ 2) stars are not uniformly distributed/ 3) it is static.  1) generally accepted
      • Cosmological Principal
        • On the large scale the Universe is uniform, no where is special, it is isotopic and homogenous
    • Evolution of the Universe
      • The Big Bang
        • Approx 13 Billion year ago all of the matter and energy in today's universe was compressed to a singularity, from which it has expanded
      • Cosmic Background Radiation
        • We receive background radiation in the microwave region in all directions
      • Fate of the Universe
        • Open Universe
          • Density < Critical, continues to expand forever
        • Closed Universe
          • Density > Critical, eventually gravity causes collapse and BIG CRUNCH
        • Flat Universe
          • When density = Critical density, expanding more and more slowly, but never going into reverse
      • Critical Denisity
        • Corresponds to Flat Universe, given by
    • The expanding Universe
      • Red Shift
        • A version of the Doppler Effect, if a galaxy is moving away, its light is shifted towards the red spectrum.
        • Change in wavelength / original = speed of recession / speed of light
        • "Blue Shift" occurs when something is travelling towards us.
      • Hubble's results
        • Hubble plotted a graph of galaxies speed of recession, against distance from Earth
          • Found that the relationship was directly proportional.
          • Hubble Constant =Gradient( Ho)
        • Hubble's Law Speed of recession ? distance. V=H x
      • The age of the Universe
        • We can deduce the age of the Universe by using the Hubble constant.
        • Age=  1/Ho
          • Ho = 71 km/s/Mpc 1Mpc= 3x10^22 Ho=71000/ 3x10^22 1/Ho=age APPROX 13.4 Billion years old
        • Untitled
      • Hubble's law and Obler's paradox
        • Hubble's Law shows that the universe is EXPANDING
        • Hubble showed distant galaxies are moving very fast. Very distant galaxies have redshifts so large their light is shifted out of the visible spectrum. A reason why night is DARK


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