The Accelerating Universe Walid J. Azzam Department of Physics College of Science University of...
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Transcript of The Accelerating Universe Walid J. Azzam Department of Physics College of Science University of...
The Accelerating Universe
Walid J. AzzamDepartment of Physics
College of ScienceUniversity of Bahrain
Outline• A Little Cosmology
• Supernovae – the tool
• The Accelerating Universe
• The Nobel Prize
Historical Perspective of Cosmology
Anaximander
Plasma Universe
Functional Universe
The Official StoryModern Cosmology
Assumptions:
1- Homogeneity
2- Isotropy
3- Universality of the Laws of Physics
Cosmological Principle
Big Bang Theory
The Universe “exploded” from a singularity of infinite density, about 13.7 billion years ago, and has been expanding ever since.
Any Evidence, Sir?
• Doppler shift of the spectral lines of galaxies.
• Percentage of H and He (and trace elements).
• Cosmic Background Radiation
Will the Universe Expand Forever?
We need to compare the current density (matter + energy) to the critical density.
> c (0 > 1) : expansion will stop; this will be followed by contraction
= c (0 = 1) : expansion stops asymtotically at infinity
< c (0 < 1) : expansion continues
Supernovae
• Historical Supernovae
• Types
• Remnants
• Use in Cosmology
Historical SNe SN 1006 Around April 30.
Read by its light at night.
Faded after 1 yr.
Seen in: Egypt, Iraq, Europe, China, Japan.
Visible in daylight.
SN 1054
July 4, “guest star”.
China, Japan, Korea, and Arabic medical textbook.
Visible by daylight.
SN 1572 (Tycho’s SN)
SN 1604 (Kepler’s SN)
Types of SNe
Remnants
Use in Cosmology