Cosmologists fail to determine an expansion rate of our universe following a disagreement among two latest sets of precise measurements.

It is a well-known fact that our universe is expanding since its beginning but the pattern of this expansion always had some mysteries attached to it. Probably the strangest fact about our universe is that all the galaxies are moving away from each other. It will be much easier to understand this concept if we consider the example of our galaxy, the Milky Way. From the perspective of humans, most galaxies of our universe are growing away from us but that’s not entirely true because you will feel the same if you are located in any other galaxy. If that was not enough to make you swirl, a recent observation will surely surprise you. According to a research published in the ‘Astrophysics Journal’, the rate of expansion of our universe is variable and it depends on how far back you want to see in time.

This finding holds immense significance to the scientific community because we may have to upgrade our understanding of the cosmos to believe this theory. Traditionally, cosmologists make use of the Hubble’s Law to explain the expansion of our universe which states that more distant galaxies are moving at a faster rate in comparison to the ones that are close by. ‘Hubble’s Constant’ is used for making these calculations as it establishes a relationship between the distance of the galaxy and its speed of expansion. The value assigned to it is 70 kilometers per second per Mega Parsec. Therefore, the size of a galaxy increases by 80,500 kilometers per hour for every million light years it is away from us.

The explanation that closer galaxies are expanding at a slower rate than the far-off ones is quite efficient in describing the expanding cosmos with dark energy and dark matter. Dark energy is the reason why the expansion rate of the universe is accelerating all the time while dark matter in an invisible form of matter that is present anywhere and everywhere in space. The process of measuring Hubble’s constant has always been a difficult one. Similarly, the results have been surprising all the time. Even Edwin Hubble, the man behind its discovery, failed to make an accurate estimate of its value in 1929. He thought that it must be somewhere around 342,000 miles per hour per million light years but the results showed that his prediction was ten times larger than the actual results.

Things haven’t changed much since then and the challenges in measuring Hubble’s constant are still there. Just when the cosmological measurements have become so precise that the scientists expected to know the value of the Hubble’s constant once and for all, a new precise measurement has pushed us back into the uncertain territory. The ‘Cosmic Microwave Background’ is an extremely precise measurement which found that the value of Hubble Constant must be around 67.4 kilometers per second per Mega Parsec. On the other hand, new precise measurements of ‘pulsating stars’ in local galaxies show that the value of Hubble Constant is 73.4 kilometers per second per Mega Parsec. The fact that these local galaxies are much nearer to us, this value should have been less.

Cosmologists believe that the reason for this disagreement is the tension between these measurements. According to their views, both these measurements are moving in different directions and there is something impulsive about it. They proposed that we may have to reconsider our cosmological model because the Cosmic Microwave Background doesn’t measure the local expansion directly. Rather, it relies on the cosmological model to deduce these results. Having said that, they acknowledged that our cosmological model has been amazingly successful in describing a lot of observational data in our universe. They also mentioned that no one has managed to develop a convincing model that could explain the disagreement as well as everything else we observe.

Scientists mentioned that whenever they try to explain this with a new theory, some of the other observations go wrong. This leads them to a point where they might need ‘new Physics’ to resolve this tension. Due to these reasons, they are unclear, as of now, about the combination which will give them the solution but cosmologists from all parts of the world are in a race to find an explanation for these results. In this situation, one thing that can be said with authority is that the result will be a showstopping change to our understanding of the cosmos if new Physics is needed.