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Some quasars display changes in luminosity which are rapid in the optical range and even more rapid in the X-rays. This implies that they are small (Solar System sized or less) because an object cannot change faster than the time it takes light to travel from one end to the other; but relativistic beaming of jets pointed nearly directly toward us explains the most extreme cases. The highest redshift known for a quasar (as of December 2007[update]) is 6.43, which corresponds (assuming the currently-accepted value of 71 for the Hubble Constant) to a distance of approximately 28 billion light-years. (N.B. there are some subtleties in distance definitions in cosmology, so that distances greater than 13.7 billion light-years, or even greater than 27.4 = 2x13.7 billion light-years, can occur.)
The size of the universe paradox - Naked Scientists Discussion Forum1 post - 1 author - Last post: 38 minutes agoThe Naked Scientists science forum supports the naked scientists podcast and radio show. Ask and answer science questions on any subject.www.thenakedscientists.com/forum/index.php?topic... - 38 minutes ago - Similar
Today, tired light is remembered mainly for historical interest, and almost no scientist accepts tired light as a viable explanation for Hubble's Law.
But, if the universe is static, how come every galaxy in it is moving away from every other galaxy?What's the driving force? And why aren't some galaxies moving closer to others?