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The Evidence for the Big Bang

The Evidence for the Big Bang. Student Resource Sheet 5 Science and Religion in Schools: Unit 4a. Evidence for the Big Bang. The Big Bang model is a concise explanation for 3 independent observations: The red shift of light from distant galaxies

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The Evidence for the Big Bang

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  1. The Evidence for the Big Bang Student Resource Sheet 5 Science and Religion in Schools: Unit 4a

  2. Evidence for the Big Bang • The Big Bang model is a concise explanation for 3 independent observations: • The red shift of light from distant galaxies • The presence of large amounts of helium in the universe • The cosmic microwave background radiation • Each can possibly be explained in other ways, but the Big Bang model draws all of them together into a convincing story

  3. The red shift Fraunhoffer lines Spectrum of light from the sun Light from a cluster of galaxies 109 light years away

  4. Hubble’s original data • Red shift due to expansion • Further away, the longer the light has been traveling • Universe has expanded more • Red shift is bigger • The velocity (speed) is basically how much the distance to the galaxy has changed in the age of the universe

  5. Much improved data • Distance scale 250 x bigger • Much more convincing! • Implication - the universe had a start

  6. Expansion of the universe • Expansion of the universe is NOT a rushing to fill empty space • The WHOLE universe is expanding - there is no empty space

  7. Helium abundance • Universe is 24% He (by mass) • Stars fuse hydrogen into helium • In 14 billion years, stars have not burned hot enough, or long enough to make this much helium • The oldest stars (11 billion years) also have ~ 24% Heso this He cannot have been made in stars! • Big Bang - in early history the whole universe was the same temp as the inside of a star! • Fusion in the first three minutes of history made the helium • This shows that the universe was hot in earliest times

  8. Cosmic Microwave Background • Arno PenziasRobert W Wilson (Nobel Prize, 1978) • Persistent microwave noise independent of time and direction • Relic radiation from Big Bang • Thermal radiation now redshifted so it is in the microwave part of the spectrum

  9. CMB (Cosmic Microwave Background) for fun and profit • Dates to 300 000 years into history • Epoch of recombination (bad name!) • Before then, all matter ionized • At this time temp of universe down to the point at which atoms could form • All free electrons captured • Thermal radiation decouples from the matter • Imprint of matter density on temperature variations • The density fluctuations ‘seed’ galaxy formation WMAP whole sky map ±200 K

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