Changes

== The size of the universe ==

== The size of the universe ==

 

The maximum distance that can be determined using parallax calculations is about 3300 light years<ref>[http://bccp.lbl.gov/Academy/pdfs/Parallax.pdf Parallax], site http://bccp.lbl.gov</ref>. Indirect measures, correlating the brightness of stars called ''cepheids'' with the period of their variability, estimate the [[Milky Way]] diameter of approximately 80-100,000 light years, although others estimate the size of the entire universe to be as narrow as only 12,000 light years across.<ref>Fangrad, Richard, 2007.</ref>

Using parallax calculations, the [[Milky Way]] galaxy alone can be estimated to have a diameter of approximately 80-100,000 light years, although others estimate the size of the entire universe to be as narrow as only 12,000 light years across.<ref>Fangrad, Richard, 2007.</ref>

Calculations based on the observed brightness of [[supernova]]e of known energy output can determine the distance to more distant objects.  The most distant object known is a galaxy cluster is estimated to be approximately thirteen billion light-years away from Earth, observed by the [[Hubble Telescope]] using gravitational lensing.<ref>Amos, 2004</ref>

Calculations based on the observed brightness of [[supernova]]e of known energy output can determine the distance to more distant objects.  The most distant object known is a galaxy cluster is estimated to be approximately thirteen billion light-years away from Earth, observed by the [[Hubble Telescope]] using gravitational lensing.<ref>Amos, 2004</ref>