‘Crisis in Cosmology’: How fast is the universe expanding, scientists are confused
The new observation comes after scientists used a new method to measure the Hubble Constant under a new study.
According to scientists, there is a 'Crisis in Cosmology'. The rate at which scientists think the universe is expanding -- which they call the Hubble Constant -- seems to be varying when they measure it using objects close to Earth, compared to those that are far away.
The new observation comes after scientists used a new method to measure the Hubble Constant under a new study, which was based on observations of “local” objects such as Type Ia supernovae or gravitationally-lensed systems.
Earlier measurements were based on “distant” observations of the cosmic microwave background (CMB) which were billions-of-year old leftover radiation from the Big Bang.
“When I first started working on this problem more than 20 years ago, the available instrumentation limited the amount of useful data that you could get out of the observations,” says co-author of the new study, Chris Fassnacht.
For these observations, his team used Keck Observatory’s Adaptive Optics (AO) system, a ground-based AO technology, in combination with NASA’s Hubble Space Telescope (HST). “I have felt for many years that AO observations could contribute a lot to this effort,” he said.
The results from the new observation suggest that there is a problem with the standard model of cosmology, which suggests that the expansion of the universe has slowed down due to gravitational pull of dark matter and now it has started speeding up due to dark energy.
This traditional theory of expansion is based on traditional Hubble Constant measurements, taken from “distant” observations of the cosmic microwave background (CMB) that came from the Big Bang, which happened 13.8 billion years ago.
Crisis in Cosmology:
“Therein lies the crisis in cosmology,” says Fassnacht. “While the Hubble Constant is constant everywhere in space at a given time, it is not constant in time. So, when we are comparing the Hubble Constants that come out of various techniques, we are comparing the early universe (using distant observations) vs. the late, more modern part of the universe (using local, nearby observations)". he says.
The author says that this might be happening because of two reasons, first, either there is a problem with the CMB measurements or the standard model of cosmology needs to be changed so that we can use the new physics to correct the discrepancy.
Scientists suggest that the new method of observation of Hubble constant can be added as a technique to measure Hubble constant.
“We can now try this method with more lensed quasar systems to improve the precision of our measurement of the Hubble Constant. Perhaps this will lead us to a more complete cosmological model of the universe,” says Fassnacht.