Cosmology

Equipped with his five senses, man explores the universe around him, and calls the adventure "science".

-- Edwin Powell Hubble

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Distance scales

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Cosmic Distance Scale

Hubble’s Measured Rate of Expansion

v=H0r

H0=72 km/(sec Mpc)

The Big Bang Framework

CMB Redshift z = 1089

Quasar Redshift z= 6.4 Change in size of space = z+1

Key Observations Explained

"NASA/WMAP Science Team” http://map.gsfc.nasa.gov/m_mm.html

• CMRB temperature and lumpiness

• flatness of space

Large Scale Structure

The distribution of galaxies in a slice of the SDSS spectroscopic survey. (A. Pope, JHUhttp://cas.sdss.org/dr2/en/astro/structures/structures.asp)

Geometry of Space

But how is the rate of expansion changing?

Astronomers set out to measure the recessional velocities of very distant objects to find out how the expansion rate may be changing.

If space is flat and the universe is dominated by matter, our rate of expansion should be slowing down.

closed open flat

exp

ansi

on

Evidence for Acceleration

An Accelerating Universe

Best Model of Mass-Energy Density

4% Visible matter 23% Dark Matter

73% Dark Energy !