Hubble Expansion Discrepancy
The Anomaly
We are able to determine the rate of expansion of the universe (Hubble's Constant) by measuring the red-shift of type 1A supernova. We are also able to determine the rate of expansion from the microwave background radiation. The problem is, if we assume the universe is flat, the measurements should be the same but they are not. The expansion rate derived from observations made locally, that is within a few hundred million light years of earth, is greater than the expansion rate derived from a region closer to the edge of our observable universe. From the more 'local' standard candles of type 1A supernova the expansion rate is determined to be 73.8 +/-2.4 km/s per megaparsec. While the WMAP mission had pegged the expansion at 69.32 +/-0.80 km/s per megaparsec, Planck has more accurately determined it to be 67.80+/-0.77 km/s per megaparsec. Even taking into consideration the error range to reduce the gap still leaves almost a 3 km/s per megaparsec difference.
We are able to determine the rate of expansion of the universe (Hubble's Constant) by measuring the red-shift of type 1A supernova. We are also able to determine the rate of expansion from the microwave background radiation. The problem is, if we assume the universe is flat, the measurements should be the same but they are not. The expansion rate derived from observations made locally, that is within a few hundred million light years of earth, is greater than the expansion rate derived from a region closer to the edge of our observable universe. From the more 'local' standard candles of type 1A supernova the expansion rate is determined to be 73.8 +/-2.4 km/s per megaparsec. While the WMAP mission had pegged the expansion at 69.32 +/-0.80 km/s per megaparsec, Planck has more accurately determined it to be 67.80+/-0.77 km/s per megaparsec. Even taking into consideration the error range to reduce the gap still leaves almost a 3 km/s per megaparsec difference.
The Argument
Having different values for universe's expansion, values that appear to be dependant on the distance from the observer, is not consistent with a flat universe. Either the measurements are incorrect or alternatively another model for the structure the universe is needed.