1. ASTR 1020 – April 27 Last Lecture, next Thursday .
Final Exam: Monday May 8 4:30-7:00pm .
Website

2. Galaxies are Flying Apart
Galaxies remain same size. They just get farther apart.
Effect is the same no matter which position you occupy

3. Expanding Universe Current Universe The volume of the universe is
increasing.
Early Universe

4. The Age of the Universe Notice: At time zero, d = 0
All galaxies are at zero distance!
The universe has zero volume!
when t=1/H

5. Jets

7. Radio Galaxies
Very Large Array
Very Large Baseline Array

8. Cygnus A

9. Radio Lobes Lobes contain 1053 Joules of energy
in relativistic electrons.
Mass energy equivalent
of a million stars!

10. Wind Blows Jets

11. Full Model

12. Superluminal Expansion
Radio interferometers
see blobs emitted by
AGN’s from base of jet.
Watch them expand.
Know distance, so can
measure speed.
v = 900,000km/s
v = 3c
Superluminal ! ?
Is Einstein’s ghost worried?

13. Phase Velocity Point of impact can move v > c
Nothing traveling that fast.

14. Better Explanation Blob moves close to speed of light toward us.
Its closer later.
Makes sideways motion appear speeded up.

15. Quasar Absorption Lines

16. The Intergalactic Medium

17. Intergalactic Medium
70% of the regular matter in the universe is between the galaxies
Was probably neutral, then re-ionized
Somehow got oxygen and other heavy elements.
We didn’t know it was there 20 years ago.
Still don’t have any clue how it works.
Cutting edge of research.

18. The Cosmic Web

19. Structure of the Universe
Where is the center of the Universe?
Where are the edges?
What happens if you fly to the edge and stick your finger through?
Newtonian Universe must be infinite.
Cosmological Principle: The Universe is Everywhere the Same
(when averaged over grand scale)

20. Classical Universe Euclidean Geometry Infinite in Extent
Matter may or may not be everywhere
Universe infinitely old
always been here, always will be
Expansion still possible
2 x ∞ = ∞

21. Cosmological Principle
Cosmological Principle applied to expanding Euclidean Universe
New matter must be formed of nothing to keep density everywhere the same.

22. Olber’s Paradox If universe is infinite with stars everywhere,
then there an infinite number of stars.
Any line of sight will eventually intersect the
surface of star. Sky would be as bright as the
surface of the Sun.
Well it isn’t. So why not?

23. Universe Must Change Answer to Olber’s Paradox: Universe must change:
Space: ie the stars stop
This was the answer until mid 20th Century
Time: Universe hasn’t always been here, so can’t see forever.
Discovery of Big Bang leads us to this answer.

24. General Relativity GR provided an answer
The presence of matter warps space in on itself.
Space is actually DEFINED by the presence of the matter in it!!!
Solves the edge problem
But geometry is no longer Euclidean

25. Geometry of Universe
Space Curves
in on itself
There’s no path
out!

26. Curved Space Surface of Earth has no end, but it is finite.
There is no “edge” but the volume is finite.