Our galaxy is inside a huge bubble where there is little matter

2024 Author: Seth Attwood | [email protected]. Last modified: 2023-12-16 15:55

We may be living in a bubble. But this is hardly the strangest thing that you have heard about our universe. Now, among the myriad of theories and hypotheses, another has emerged. The new study is an attempt to solve one of the most difficult mysteries of modern physics: why our measurements of the rate of expansion of the universe do not make sense?

According to the authors of the article, the simplest explanation is that our galaxy is in a low-density region of the Universe - which means that most of the space that we can clearly see through telescopes is part of a giant bubble. And this anomaly, the researchers write, is likely to interfere with measurements of the Hubble constant - a constant used to describe the expansion of the universe.

How did the universe develop?

Try to imagine what the bubble would look like on the scale of the universe. This is quite difficult, since most of space is space, with a handful of galaxies and stars scattered in the void. But just like the regions in the observable Universe, where matter is densely clustered or, on the contrary, is located far from each other, stars and galaxies gather together with different densities in different parts of the cosmos.

Background radiation (or cosmic microwave background radiation) - this thermal radiation that formed in the early Universe and fills it evenly - allows scientists to determine with almost perfect accuracy the uniform temperature of the Universe around us. Today we know that this temperature is 2.7K (Kelvin is a temperature scale, where 0 degrees is absolute zero). However, according to Space.com, on closer inspection, you can see small fluctuations in this temperature. Models of how the universe has evolved over time suggest that these tiny inconsistencies would eventually spawn more or less dense regions of space. And these kinds of low-density regions would be more than enough to distort the measurements of the Hubble constant in the way it is happening right now.

Absolute zero is a term that means the complete stop of the movement of molecules. Absolute zero temperatures cannot be reached. In 1995, Eric Cornell and Carl Wiemann tried to do this, but when the rubidium atoms were cooled, they did not succeed. That is why the unit of temperature change in Kelvin does not have negative values.

How is the Hubble constant measured?

Today there are two main ways to measure the Hubble constant. One is based on extremely accurate measurements of the CMB, which appears to be uniform throughout our universe since it was formed shortly after the Big Bang. Another way is based on supernovae and pulsating variable stars in nearby galaxies known as Cepheids. Recall that Cepheids and supernovae have properties that allow us to accurately determine how far they are from the Earth and at what speed they are moving away from us. Astronomers have used them to build a “distance ladder” to various landmarks in the observable universe. The same “ladder” was used by scientists to derive the Hubble constant. But as measurements of Cepheids and CMB have become more accurate over the past decade, it has become clear that the data do not converge. And the presence of different answers usually means that there is something that we do not know.

So, in fact, it is not just about understanding the current rate of expansion of the Universe, but also about understanding how the Universe developed and expanded and what was happening with space-time all this time.

Galaxies in a bubble

Some physicists believe that there is some kind of "new physics" that determines the imbalance - something in the universe that we do not understand and that is the reason for the unexpected behavior of space objects. According to study author Lucas Lombrizer, a new physics would be a very exciting solution to the Hubble constant, but it usually implies a more complex model that requires clear evidence and needs to be backed up by independent measurements. Other scientists believe the problem lies in our calculations.

The solution, proposed in a new article to be published in Physics Letters B in April 2020, is to assume that our entire galaxy, as well as several thousand nearby galaxies, are in a bubble where there is little matter - stars, gaseous and dust clouds. According to the author of the study, a bubble with a diameter of 250 million light years, containing about half the density of the rest of the universe, could reconcile different figures for the expansion rate of the universe.