It is a belief that belongs to Lucas Lombriser, a theoretical physicist at the University of Geneva. It isn’t a new idea, but more of a comeback of a theory from two decades ago. The theory says that our galaxy, along with the surrounding ones, is just a lighter corner of the Universe. Lighter, because this bubble contains about half as much matter as the cosmic average.
This hypothesis might be the answer to the mysterious expansion of the Universe and its ever-accelerating pace. We know that it expands, but the discrepancies between the measurements made so far didn’t help unravel the mystery. The Hubble Constant might finally find its peace.
Hubble’s law is considered the first observational basis for the expansion of the Universe. The motion of astronomical objects due solely to this expansion is known as the Hubble flow. It is often expressed by the equation v = H0D. H0 is the constant of proportionality – Hubble constant. The law says that the velocity of an object is plotted concerning its distance from the observer.
The Hubble constant
Although attributed to Edwin Hubble, the notion of the Universe expanding at a measurable rate was first derived by Alexander Friedmann.
Georges Lemaître also derived that the Universe might be expanding and suggested an estimated value of the proportionality constant. When corrected by Hubble, the constant became known as the Hubble constant. Two years later, Edwin Hubble confirmed the existence of cosmic expansion and determined a more accurate value for the constant.
In 1931, Einstein made a trip to Mount Wilson to thank Hubble for providing the observational basis for modern cosmology.
The value of the Hubble constant is estimated by measuring the redshift of distant galaxies and then determining the distances to the same galaxies. Uncertainties in the physical assumptions used to identify these distances have caused varying estimates of the Hubble constant.
The possible solution
Now, Luca Lombriser sustains that those variations could be the consequence of an overestimation of how dense our corner of the Universe is compared to the average cosmic density of matter.
“More observations and surveys will help to improve these estimates, but also a better understanding of the distribution of dark matter will be required. With more such gravitational wave events, we should be able to reduce this uncertainty and get a better measurement of our local density,” said the physicist.