The balloon universe has a finite size but no edge. You walk in a straight line, you eventually arrive back at where you started! Pretend you areĬonfined to the surface of a balloon and you only know about ``front'', ``back'', Two-dimensional world curving into the third dimension. To help you understand what curved spacetime means, let's use the analogy of a You may want to refresh your memory of these concepts by reading the In General Relativity, four-dimensional spacetime isĬurved. General Relativity describes gravity as a warping or distortion of space and Other evidence for a changing universe is Increase in the number of quasars at large distances from us, is strong evidence ofĪ universe that DOES change, or evolve. This isĪpproximately one hydrogen atom/Houston Astrodome every year-a very small amount! Hydrogen atom per cubic centimeter every 10 15 years. Perfect cosmological principle to be true is quite small-only one However, the amount of new matter that would need to be created for the This law says that the totalĪmount of mass does not change-mass is not created from nothing or destroyed. This violates a central rule of nature knownĪs the law of the conservation of mass. Not change with time there is no evolution. The cosmological principle allows the universe to change, orĪn extension of the cosmological principle called the perfectĬosmological principle says that the universe also does Everyone at the same cosmological time will measure the same age of Means the time measured from some common event like the creation of the Same thing, such as the same Hubble-Lemaître law. Every observer at a given cosmological time will see the The cosmological principle is a Copernican idea. The structure of the universe as you look in different directions. There are two aspects of the cosmological principle: The idea of a uniform universe is called the cosmological One spoonful of pudding looks like any other spoonful, even though, there are It is like a large bowl of tapioca pudding, On large enough scales though, the universe has many
The discovery of the long superclusters may seem to endanger thisĪssumption. To understand the universe as a whole from observing our surroundings. We lived in an unusual part of the universe, then it would be almost impossible This makes the universe models simpler and ``more reasonable''-if
On size scales of billions of light years, the universe is assumed to be See my copyright notice for fair use practices. This material (including images) is copyrighted!. Cosmology Universe is Uniform on Large Scales Chapter index in this window
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