Before Edwin Hubble discovered that galaxies were receding from each other, people strongly believed that the universe was static and there was no component in it which exerted a negative pressure and countered the attractive force of gravity. This belief was so strong, in fact, that even Einstein, upon finding that his equations were predicting an expanding universe, arbitrarily added a cosmological constant to keep the universe static. A few years after GR was published, however, Hubble found that the universe was, in fact, expanding. Not only that, but by plotting the distances of several galaxies against their measured red-shifts, he also found that more distant galaxies were receding faster than those which were closer [11].
Soon after Hubble announced his findings, astronomers raced to measure the exact expansion rate of the universe. By measuring the flux of Type IA supernovae at different distances, they calculated the Hubble Constant to be 71 kilometers per second per megaparsec. More importantly, however, when they compared that data to different types of cosmologies, they found that our universe did not seem to have a matter density high enough to re-collapse and seemed to be accelerating due to some mysterious, unknown repulsive vacuum energy [11]. …show more content…
For this reason, it was not until results from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite were published that all lingering doubts about the existence of dark energy were eliminated. By giving us the most detailed picture of the CMB, WMAP data confirmed what other observations were already suggesting: ordinary matter, which is really the only type of matter we know about, makes up only four percent of the entire universe. The rest is dark matter and dark energy, the former composing 23 percent of the universe and the latter 73 percent
Soon after Hubble announced his findings, astronomers raced to measure the exact expansion rate of the universe. By measuring the flux of Type IA supernovae at different distances, they calculated the Hubble Constant to be 71 kilometers per second per megaparsec. More importantly, however, when they compared that data to different types of cosmologies, they found that our universe did not seem to have a matter density high enough to re-collapse and seemed to be accelerating due to some mysterious, unknown repulsive vacuum energy [11]. …show more content…
For this reason, it was not until results from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite were published that all lingering doubts about the existence of dark energy were eliminated. By giving us the most detailed picture of the CMB, WMAP data confirmed what other observations were already suggesting: ordinary matter, which is really the only type of matter we know about, makes up only four percent of the entire universe. The rest is dark matter and dark energy, the former composing 23 percent of the universe and the latter 73 percent