Actually the assumption that our visible "sliver" of the universe is expanding is based on the presumption of <i>cosmological redshift</i>, not a relativistic doppler effect. That and the <b>big clue</b> of increasing apparent angular diameter of galaxies with high redshifts.<br /><br />Only in the local supercluster are red and blue shifts assumed to be due to relativistic doppler effect, caused by the relative inertial motions of galaxies bound by gravity. Outside of that gravity bound cluster of galaxies, all the other clusters of galaxies are redshifted and this is assumed to be cosmological redshift, where the light we are seeing has been "stretched" by the expansion of the universe.<br /><br />Above redshifts of z=1.6 we see an apparent increase in a galaxies angular diameter and the dimmer and more redshifted the galaxy, the larger its apparent angular diameter is.<br /><br />The angular diameter of an observed object can be used as an indication of the distance to that object when the light was emitted, and some of the dimmest most highly redshifted galaxies we have seen have a angular size that puts them less than 4 billion light years away, 13 billion years ago! <br /><br />A brighter, less redshifted galaxy has an angular size that puts it over 5 billion light years away when it emitted the light we are seeing, but that light has only been travelling for around 10 billion years.<br /><br />Let me quantify those examples:<br /><br />Galaxy A<br />Redshift: z=7<br />Light travel time: 13 billion years<br />Angular diameter distance: 4 billion light years<br /><br />Galaxy B<br />Redshift: z=1.7<br />Light travel time: 10 billion years<br />Angular diameter distance: 5.8 billion light years.<br /><br />Are there other possible explanations, other than expansion, for these observations?<br /><br />Well, if dimness and redshift were <i>only</i> due to light travel time, we might live in a static universe, but that would mean that the further away in time a galaxy is, the larger it <i></i> <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>