Measuring the growth of the universe is extremely difficult. However, a group of astronomers has successfully made a measurement of the speed at which the universe is expanding, probably the most accurate measurement ever made. However, their measurements are different from those of other researchers, which is a mystery to all, as if there is something about the universe that scientists are not really aware of and that they can not predict.
"The community is really struggling with understanding the importance of this discrepancy," said Adam Riess, senior researcher, in a statement.
The team consists of researchers from John Hopkins University and the Space Telescope Science Institute. They explored the universe with the Hubble Space Telescope over the past six years. They used the measurements to calculate the speed at which the universe expands over time. This constant is called the Hubble constant.
The Planck satellite of the European Space Agency has made its own measurements mapping the cosmic microwave background and predicted that the Hubble constant value should be 67 kilometers per second per megaparsec. In short, for every 3.3 million light-years that a galaxy is farther away, the movement is 67 kilometers per second faster.
However, Riess's measurements contradicted those of the Planck satellite at 73 kilometers per second per megaparsec. These results indicate that the galaxies move faster compared to previous measurements.
Hubble telescope data has always been the most accurate data so astronomers can not ignore the distance between the two or ignore results as errors in the measurement method.
"Both results have been tested several times," said Riess, professor at Johns Hopkins and co-winner of the Nobel Prize in 201
Riess proposes several explanations why a mismatch occurred. He believes that the error has come about because the 95% of the universe is surrounded by darkness. He believes that could be one reason why the dark energy that is known to be the cause of the acceleration of the universe could cause galaxies of greater strength to move away from each other. If this is the correct explanation then the acceleration is not a constant value but changes with time instead.
He also points to a previously unknown subatomic particle that is almost as fast as light. Particles at such a rate are termed "dark radiation" and include particles such as neutrinos generated by nuclear reactions and radioactive decay. However, the new proposed particle could only be affected by gravity, unlike normal neutrinos that interact with subatomic force. The new particle is called a "sterile neutrino".
Riess and his team will continue to work to measure the growth of the universe and make the universe's rate of expansion more accurate. Their results will appear in the Astrophysical Journal. The work of Riess and his team is supported by NASA, the National Science Foundation and other donors.