Lecture34_07 dark matter and dark energy .ppt
- 1. The universe: dark matter and dark energy
- 2. Cosmic Microwave Background was discovered in 1965 This really is a map of the sky, black zero emission, green that of a blackbody of 2.7K!
- 3. To see ripples in the CMB, you really have to go down in sensitivity Results from spacecraft WMAP, released on February 11, 2003
- 4. From these tiny fluctuations grew the structure we see in the universe today Clusters of galaxies, galaxies, and stars
- 5. So what kind of universe do we live in? open, closed…? Recall that it depends on the mean density Via the parameter
- 6. Determining the mean density of the universe
- 7. The answer is…. • For “bright matter” omega = 2.2E-03 • All “baryonic matter” (from abundance of light elements), omega = 0.02 – 0.05 • Taking account of dark matter in clusters of galaxies, omega = 0.33 • Best estimate is that omega < 1 • Abstract of Turner article
- 8. The truly weird feature of this is that most of the matter in the universe is not even Baryonic, and thus is of an unknown form. Taken at face value, this result indicates that omega is < 1, and we live in an open universe. This was the status a few years ago. Then things got even stranger
- 9. • For Omega =1, the fan out is the smallest • For Omega =0.33, it is larger • For Omega = 0, it is larger still, and the maximum for a Friedmann universe
- 10. Use cosmological model to calculate m of z
- 11. What is found for Type Ia SN
- 12. The Expansion of the Universe is Accelerating • Not explicable in terms of a Friedmann universe • Behavior requires addition of “Cosmological Constant” to the theory • Physically, corresponds to “Dark Energy”, an energy field the produces long range, repulsive force • Dark energy can contribute to Omega, make it 1
- 13. Contemporary “Precision” Cosmology • Omega of Baryonic matter = 0.02 – 0.05 • Omega of all matter = 0.33 • Omega of Dark Energy = 0.67 • Age of Universe = 13.7 Gyr • Inflation occurred 1E-34 sec after Big Bang, during which universe puffed up by factor of 1E+25 Total = 1
- 14. In spite of precision, still some (very) unsatisfactory aspects • Nature of the Dark Matter unknown. When (if ever) will we confirm its existence in a laboratory? • Nature of the “Dark Energy” is completely unknown
- 15. Implications for our view of ourselves “The Realization that the majority of the matter in the universe might be non-Baryonic is the ultimate Copernican viewpoint; not only are we in no special place in the universe, but we aren’t even made out of the same stuff as dominates the matter density of the universe.” Andrew Liddle – An Introduction to Modern Cosmology
- 16. “The Truth is out there”