Please Register or Log in to view the hidden image! Universe Age from Microwave Background Credit: WMAP Science Team, NASA The above sky map tells us the universe is 13.7 billion years old -- but how? At first look, one only sees the microwave glow of gas from our Milky Way Galaxy, coded red, and a spotty pattern of microwaves emitted from the early universe, coded in gray. The gray cosmic microwave background is light that used to bounce around randomly but came directly to us when the expanding universe became cool enough for nearly transparent atoms to form. A close inspection of the spots reveals a slightly preferred angular distance between them. One expects such a pattern to be generated by sound emanating from slightly over-dense regions of the early universe. Sound waves will take time to generate such a pattern, and the present age of the universe can then be directly extrapolated. The above universe age is estimated to be accurate to better than 0.2 billion years. The above map was taken by the WMAP satellite orbiting the Sun at the L2 point, just outside the orbit of the Earth.
A revealing picture. To estimate the age of the universe you have to measure the “Hubble constant”. The Hubble constant is a measure of the current expansion rate of the universe. you can use this measurement to extrapolate back to the Big Bang. This extrapolation depends on the history of the expansion rate which in turn depends on the current density of the universe and on the composition of the universe. "If the universe is flat and composed mostly of matter, then the age of the universe is 2/(3 Ho) -(where Ho is the value of the Hubble constant.). If the universe has a very low density of matter, then its extrapolated age is larger: 1/Ho. If the universe contains a form of matter similar to the cosmological constant, then the inferred age can be even larger. The current best value for the Hubble constant is about 72 km/sec/Megaparsec. In more familiar units, astronomers believe that 1/Ho is between 12 and 15 billion years." The lumpyness of the picture will indicate the density of the universe.
