Are we in a hole in the universe? The possible explanation of a problem in astronomy – Yourweather.co.uk

Researchers are looking for an explanation for a problem called the Hubble tension. This is a problem that leaves the question: what is the expansion rate of the Universe? No answer.

The Universe is expanding rapidly. When we observe very distant galaxies we realise that they move away from us quickly. The first person to realise this was astronomer Edwin Hubble in the 1920s. Hubble introduced with observations that the Universe was expanding.

Decades of observations confirmed what Hubble had observed. In the 1990s, the Hubble telescope - named because of the astronomer - was launched with the main objective of answering the question: what is the rate of expansion of the Universe? Or how much is it expanding?

This is a question that to this day brings discussions within the field of Astronomy.This is because each measure gives a slightly different result that can have different consequences. A new study argues that these results differ because we are inside a void in the Universe with low density of galaxies.

The first observation that galaxies further away from us move away more quickly came with the work of Edwin Hubble. This meant that not only was the Universe expanding but also expanding in an accelerated way. A discovery for astronomers of the time who were still dealing with the fact that other galaxies existed.

The rate of expansion of the Universe took the name of Hubble constant, it measures the rate in units of km/s per megaparsec.

The first estimate of the Hubble constant was made by Edwin Hubble himself, who reached a value of 500 km/s per megaparsec. Nowadays, the value is close to 70 km/s per megaparsec despite the divergences of different observation tools.

Before the question of how much the Universe expands, it is more common to ask ourselves why it expands. And that's on the back of a concept called dark energy. Dark energy would be a component of the Universe that has the effect of the expansion we observe.

What dark energy is still remains a mystery. To this day we can only observe the effects it causes and the way it acts against the gravitational interaction that dominates at smaller scales. Many physicists and astronomers seek to answer the question of what dark energy is.

It is important to note that dark energy and dark matter are two different components and are not related in principle. While one acts on smaller scales through gravitational interaction (dark matter) the other has an action on cosmological scales and an opposite effect to that of gravitational interaction (dark energy).

The idea of measuring the Hubble constant seems to be simple: just calculate how far away the galaxies are and measure. However, the reality is a little more complicated. There are different methods to calculate the speed and distance of galaxies from the use of supernovae luminosity to the use of redshift and cosmic background radiation.

All measurements should give equal values but that's not what happens so the question that arises is: which measure is correct and why do the others fail?

In addition, some measures show that the Universe seems to be expanding faster closer to us, which is not true. This raises a problem called the Hubble voltage problem or the Hubble voltage crisis.

A group of researchers from the University of Bonn in Germany proposed an interesting idea to explain Hubble's tension. The group argues that errors in measurements are associated with our position in the Universe because we are in a low density region, in other words, we are more alone than we thought.

The research used observations of groups of galaxies located 600 million light-years from us. These galaxies are moving away faster than expected by the cosmological model, meaning that something else would be pulling them.

The cosmic network of the Universe looks like a spider web where galaxies tend to be attracted to regions with other galaxies through gravitational interaction. This forms a network with filaments with a high density of galaxies and voids with very low density.

The idea of the work is that we are located close to one of these voids and when we look at groups close to us we are seeing them being attracted by these filaments. This would cause the gravitational interaction to pull these galaxies into the filaments moving them away from us who are out of reach.

The study argues that the next observations should be made with this possibility in mind. Add the effect that nearby galaxies are being pulled by other galaxies and this affects the result.

In addition, the group also argues in favor of MOND that it is a modified theory of gravity and that it should be considered in future analyses as well.

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Are we in a hole in the universe? The possible explanation of a problem in astronomy - Yourweather.co.uk