Lecture34_07 dark matter and dark energy .ppt

dark

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”