1. Cosmology & The Big Bang Theory Dr Alex Calverley

6. Cartesian coordinates Polar coordinates

7. Special relativityGeneral relativity

8. In 1915... In 1917... Using the GR metric from the last slide Friedmann solved the equation in 1922 to get...

9. k > 0 k < 0 k = 0

10. Demonstrating the relationship between comoving (i.e. coordinate) distances and physical distances a = 1 today (a 0 ), and a(t) < 1 at earlier times

11. In 1929...

12. However, in 1927... If D(t) is the proper distance between two objects at time t and D 0 is the proper distance now, then: and Then combining these So Lemaître had predicted

13. EVIDENCE FOR THE BIG BANG THEORY (1) An expanding universe where the recessional speed is proportional to the distance away

14. In 1948... George Gamow predicts the ratio of light elements due to Big Bang Nucleosynthesis Ralph Alpher and Robert Herman predict the glow from the Big Bang will still be visible in the microwave spectrum with a temperature of about 5 K

22. Colours represent fluctuations of size ΔT/T ~ 10 -5

23. EVIDENCE FOR THE BIG BANG THEORY (2) A near perfect blackbody spectrum at T ≈ 2.7 K, suggesting the Universe was once much hotter and denser

26. EVIDENCE FOR THE BIG BANG THEORY (3) BB Nucleosynthesis can explain the observed ratios of light elements in pristine primordial gas

27. In 1999... The Universe’s expansion is accelerating! Need an extra component to the Friedmann equations called Dark Energy – which acts just like Einstein’s Λ term!

28. Colours represent fluctuations of size ΔT/T ~ 10 -5