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The First Question?

The First Question?. Was the Universe created? (Did it have a beginning?) OR: Has it existed for all eternity?. The Theories. The Big Bang Theory. (Option 1!) The Steady State Theory. (Option 2!). The First Steady State Theory.

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The First Question?

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  1. The First Question? • Was the Universe created? (Did it have a beginning?) OR: • Has it existed for all eternity?

  2. The Theories. • The Big Bang Theory. (Option 1!) • The Steady State Theory. (Option 2!)

  3. The First Steady State Theory. • “The Universe has always been the same and will always be the same – unchanging.” • 1900 – accepted by most scientists – Why? • No real evidence.

  4. The Expanding Universe. 1920s – Edwin Hubble’s measurements proved that : • Most galaxies are moving away from us • The further a galaxy is away from us the faster it is moving. So: • All the galaxies are moving away from each other! How do we know all this?

  5. The Red Shift.

  6. The Doppler Effect.

  7. Hubble’s Law. • “The speed with which a galaxy moves away from us is proportional to its distance away from us.”

  8. What You Need to Know! • Star spectra contain black (absorption) lines. • These should occur at particular wavelengths. • For galaxies these wavelengths are shifted towards the red end of the spectrum. (Longer wavelength) • This is the Red Shift. • This means the galaxies are moving away from us. • This is the Doppler Effect. • Hubble’s Law Expansion of the Universe.

  9. What Does This Mean? • 1927 – Georges Lemaitre realises that if you ‘rewind’ an expanding Universe you eventually get to “a day that has no yesterday”. • The expanding Universe is evidence for a ‘moment of creation’? • BUT the numbers didn’t work!

  10. The Return of the Steady State? • 1948 – Bondi, Gold and Hoyle suggest that matter is continuously being created in space to compensate for the expansion. • Universe grows but overall remains the same, eternal. • BUT no known mechanism!

  11. The Big Bang Theory – a Prediction! • 1940s – Gamow, Alpher and Herman realise that there was a huge burst of e/m radiation early on. • ‘Stretched out’ and cooled it would now be gentle microwave radiation.

  12. Discovery of CMBR. • 1965 – Penzias and Wilson – looking for the source of irritating microwave interference. • Discovered the origin was – SPACE! • Same wherever they looked.

  13. Cosmic Background Microwave Radiation.

  14. The Big Bang Theory. The Universe began as a sudden release of energy roughly 15 billion years ago. Evidence: • Expansion of Universe – Red Shift. • Cosmic Background Microwave Radiation. • Quasars – the Universe used to be different! • The amount of helium found in the Universe.

  15. The Final Question? What is the destiny of the Universe? Probable facts: • The Universe is expanding from the Big Bang. • All matter in the Universe is attracting all other matter – gravity. • So the expansion of the Universe is slowing down.

  16. Destiny of the Universe? • Sufficient mass in the Universe to slow down the expansion enough to stop it and pull it back together again. • The Big Crunch. • Also called a Closed Universe.

  17. Destiny of the Universe? • Could a Big Crunch be followed by another Big Bang and the creation of a whole new Universe? • The Oscillating Universe theory!

  18. Destiny of the Universe? • Not enough mass – Universe keeps on expanding forever – getting colder and darker. • The Big Freeze. • Also called an Open Universe.

  19. Can We Find Out? • We don’t know how much the expansion is slowing down. • We do know how fast it is expanding. (Hubble!) • So we know the critical density needed to stop it. • But how do we measure all the mass in the Universe?! • Problem – Dark Matter!

  20. A Final Problem? • The most recent measurements seem to show that the expansion of the Universe is speeding up NOT slowing down! • ‘Dark Energy’? • The Big Rip?

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