Rossana Rugeri: The universe is expanding since the big bang almost 14 billion years ago, and astronomers believe that a kind of invisible power called Dark Energy is accelerating faster.
However, new results from the Dark Energy Spectroscopic instrument (Desi), which is released today, suggest that dark energy can change over time.
If the result is confirmed, it can destroy our current cosmology theories – and have significant consequences for the final fate of the universe. In extreme scenarios, evolving dark energy could accelerate the expansion of the universe to the point to tear it apart in a “big crack” or to ensure that it collapses in a “big crunch”.
As a member of the Desi cooperation, which includes more than 900 researchers of 70 institutions worldwide, I was involved in the analysis and interpretation of the dark energy results.
A new image of dark energy
First discovered in 1998, Dark Energy is a kind of essence that seems to penetrate space and grow the universe at an ever -increasing speed. Cosmologists have generally assumed that it is constant: it was the same in the past as in the future.
The assumption of constant dark energy is baked generally accepted Lambda-CDM model of the universe. In this model, only 5% of the universe consists of the ordinary issue that we can see. Another 25% is invisible dark matter than can only be detected indirectly. And by far the majority of the universe – no less than 70% – is dark energy.
The results of Desi are not the only thing that gives us instructions about dark energy. We can also look at evidence of a kind of exploding stars called type ia supernovae, and the way in which the path of light is twisted while traveling through the universe (so -called weak gravity lens).
Measurements of the vague afterglow of the big bang (known as the cosmic microwave background) are also important. They do not immediately measure dark energy or how it evolves, but they provide clues about the structure of the universe and the energy content of the universe – help to test dark energy models in combination with other data.
When the new Desi results are combined with all this cosmological data, we see hints that dark energy is more complicated than we thought.
How desi maps the universe
The Desi project is located in the Kitt Peak National Observatory in Arizona. The goal is to make the most extensive 3D card of the universe ever.
To do this, it uses a powerful spectroscope to precisely measure the frequency of the light of a maximum of 5,000 distant galaxies at the same time. This allows astronomers to determine how far the galaxies are and how quickly they move.
By mapping out galaxies, we can detect subtle patterns in their large -scale distribution called Baryon Acoustic Oscillations. These patterns can be used as cosmic rulers to measure the history of the expansion of the universe.
By following these patterns over time, Desi can be mapped out how the expansion of the universe has changed. Desi is only halfway through a planned five -year survey of the universe, releasing data in batches as it goes.
The new results are based on the second party data, which includes measurements of more than 14 million galaxies and brightly glowing galactic cores called Quasars. This dataset includes a cosmic period of 11 billion years – from when the universe to this day was only 2.8 billion years old.
New data, new challenges
The new Desi results are an important step forward compared to what we saw data in the first party. The amount of data collected has more than doubled, which has improved the accuracy of the measurements and has made the findings more reliable.
Results of the first series of data gave a hint that dark energy may not act as a simple cosmological constant – but it was not strong enough to draw strong conclusions. Now the second series of data has made this proof stronger.
The strength of the results depends on which other data sets it is combined, in particular the type of supernova data. Until now, however, no combination of data meets the typical “five Sigma” statistical threshold that physicists use as the marker of a confirmed new discovery.
The fate of the universe
Nevertheless, the fact that this pattern becomes clearer with more data that something is going on. If there is no error in the data or the analysis, this may mean that our understanding of dark energy – and perhaps the entire standard model of cosmology – must be revised.
If dark energy changes over time, this can have a major consequences for the ultimate fate of the universe.
If dark energy becomes stronger over time, the universe can face a “big rip” scenario, where galaxies, stars and even atoms are torn apart by the increasing expansion percentage.
What is the following?
Desi wants to collect data from a total of 40 million galaxies and quasars. The additional data will improve statistical precision and further refine the dark energy model.
Future Desi releases and independent cosmological experiments will be crucial to determine whether this represents a fundamental shift in our understanding of the universe.
Future data can confirm whether dark energy is indeed evolving – or whether the current hints are just a statistical anomaly. If dark energy is found dynamically, it may require new physics that go beyond Einstein’s theory of general theory of relativity and open the door for new models of particle physics and quantum gravity.
https://www.youtube.com/watch?v=FQKFS5YOT5I
Rossana Ruggeri, teacher and ARC Decra Fellow, Queensland University of Technology
This article has been re -published from The conversation Under a Creative Commons license. Read the Original article.
