1. Lectures on galaxies and cosmology
Astronomy II, Fall 2005
Lectures on galaxies and cosmology
Dr Martin Hendry
University of Glasgow, UK
(Basler Chair, 2005)
Tel: 94252
Brown Hall, Room 373
Office Hrs: Mon – 11.30
Tue – 15.30

2. Cosmology: the Nature of Spacetime
Olbers’ Paradox:
Why is the sky dark at night?

3. Cosmology: the Nature of Spacetime
Olbers’ Paradox:
Why is the sky dark at night?

7. The Cosmological Principle
At any time, the Universe is isotropic and homogeneous

10. Hubble’s Law: 1929
Distant galaxies are receding from us with a speed proportional to their distance

11. Hubble’s Interpretation
‘Recession of the Nebulae’ caused not by the motion of galaxies through space, but the expansion of space itself between the galaxies
Cosmic scale factor increases as the Universe expands

12. Einstein’s General Relativity
“Matter tells space how to curve, and space tells matter how to move”

13. In General Relativity even
light is affected by the
curvature of spacetime.
We call this effect
Gravitational Lensing
GL is now routinely observed
throughout the universe

14. Gravitational lensing observable during a total solar eclipse

18. Will the Universe continue to expand forever?
In simple cosmological models this depends on how much matter there is in the Universe (or more precisely, what is the density of matter?)
If the density is more than a critical value, the Universe will recollapse

20. Answer related to the curvature of the Universe

21. Answer related to the curvature of the Universe
Positive

22. Answer related to the curvature of the Universe
Positive
Negative

23. Answer related to the curvature of the Universe
Positive
Negative
Zero

26. We can measure this using Supernovae and the background radiation

27. Hubble diagram of distant supernovae
We need a good standard candle, to probe the geometry of the Universe
Type I Supernovae
Distant SN fainter than expected.
Suggests Universe expanding even faster today than in the distant past
Expansion is accelerating!

29. What is driving the cosmic acceleration?…
Dark Energy

30. State of the Universe – Nov 2005
Dark Energy
Cold Dark Matter
Atoms