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