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Evidence for a finite Universe

Evidence for a finite Universe. Stellar populations. Hertzsprung-Russell diagram. Clusters of stars. Stars can form in clusters. Perhaps most of them do, then get dispersed. Most stars in a cluster are approximately the same age. HR diagrams of clusters.

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Evidence for a finite Universe

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  1. Evidence for a finite Universe Stellar populations

  2. Hertzsprung-Russell diagram

  3. Clusters of stars Stars can form in clusters. Perhaps most of them do, then get dispersed. Most stars in a cluster are approximately the same age

  4. HR diagrams of clusters Different clusters have different turn-offs from the main-sequence, related to the stars’ ages.

  5. Main-sequence ages

  6. Population evolution

  7. Stellar populations • Hotter and more massive stars burn brighter, much brighter, for shorter lifetimes • Young stars can be red or blue • Young populations are blue because they are dominated by hot blue stars • Old populations are redder, red giants dominate much of the light

  8. Globular star clusters

  9. HR diagrams Oldest star clusters are 10-14 Gyr old

  10. Evidence for a finite Universe Redshift and the Tolman test

  11. The Redshift

  12. Spectral lines are shifted Quasar spectra at different redshifts 2QZ survey with Anglo-Australian T.

  13. Tolman test for surface brightness Pahre et al. 1996 BUT there is evolution …

  14. Evidence for a finite Universe Thermal spectrum of cosmic background radiation (CBR)

  15. Planck or ‘blackbody’ spectrum

  16. Evidence for a finite Universe Olbers’ Paradox

  17. Why is the night sky dark?

  18. Why indeed?

  19. Resolving Olbers’ Paradox • Universe is finite in age • Finite observable region • Redshift dims distance galaxies

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