The Origin of the Universe

A survey of the evidence

Introduction
Measurement Overview
    Parallax Distances
    Star Sizes and Absolute Magnitudes
    Cepheid Distances
    Type 1a Supernovae Distances
    Redshift Velocities and Distances
    Age of the Stars in Globular Clusters
    The Oldest White Dwarfs
    The Cosmic Microwave Background
Conclusion

Light from galaxies is Doppler shifted - changed in wavelength by a factor related to galactic velocity. We understand the relationship between the velocity of a light source and the amount of Doppler shift. Astronomers have used this method to measure the velocity of millions of galaxies. In whichever direction we look, the light from the galaxies is shifted towards red. The galaxies are moving away. As well as velocity, distance can also determined from galactic redshifts. When Cepheid distance was plotted against velocity, astronomers noticed that galactic recession velocities and galactic distances are precisely related. They have used this relationship to determine the distance to millions of galaxies out to distances of billions of years.