The astronomers at the Kit Peak Observatory in Arizona, USA, have begun with the most detailed observations of the universe ever made. The observations will take five years, their main goal is to get as much information as possible about the mysterious dark energy – the force that is believed to be responsible for the accelerated expansion of the universe. The instrument called DESI, with which observations are made, contains 5,000 built-in miniature telescopes. Each of them can capture light from galaxies every 20 minutes. This will allow scientists to study more galaxies in one year than any other telescope in the world. It is known that the telescope will observe 35 million galaxies. But can scientists learn about dark energy?
What is dark energy?
According to the big bang theory, the expansion of the universe slows down and it can start to contract due to the effect of the gravitational force. In 1998, however, astronomers were shocked to find that the universe was not only expanding but accelerating. The most prevalent opinion is that something counteracts gravity – later it was called dark energy. Estimates suggest that dark energy makes up most of the universe. In fact, the atoms that make up the stars, planets, and galaxies are probably only 5%. Twenty years have passed since the discovery of dark energy, but scientists still do not know about it. All modern knowledge of the universe is based on a negligible 5%. It is logical to assume that understanding the nature of dark energy can lead to a real revolution in physics.
How will you search for dark energy?
An international research team will use a device called the Dark Energy Spectroscopic Instrument (DESI) for dark energy search and investigation. It was mounted on the 4-meter Mayall telescope at the Kitt Peak Observatory in Arizona, USA. DESI has 5,000 optical fibers, each of which acts as a miniature telescope. In this way, the tool can simultaneously capture light from 5,000 different galaxies and accurately show their distance from Earth, as well as measure the expansion of the universe as the light reaches our planet.
Under ideal conditions, DESI is able to capture light from galaxies every 20 minutes. The further DESI looks into the room, the further back in time it sees. The device can see objects 10 billion light years from Earth, which means the objects were 10 billion years ago. There have been similar projects, but DESI will cover a much larger volume of space and measure the acceleration of the universe's expansion three times more accurately than ever before. The team used previous research to create a map guide to the universe, from which 35 million galaxies were selected as targets for DESI.
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What secrets of the universe can be revealed?
A key factor for dark energy, according to the generally accepted cosmological constant, is a force called vacuum pressure, which is caused by fluctuations in the space-time tissue at the subatomic level. Calculations show that the vacuum pressure must be displayed with an unimaginable number (1 with 120 zeros afterwards) than the force that astronomers actually see when "pushing the galaxies". The researchers also do not rule out that the vacuum pressure in the early universe was much, much higher and has now dropped to its current state. However, when astronomers realize that vacuum pressure remains the same, several speculative theories come into play. So we can assume that our universe is one of many in the "multiverse" – this can be explained by the fact that the vacuum pressure in our universe is small, while in other universes it is much larger. But matter – and ultimately life – can only exist in a universe like ours with low vacuum pressure.
That's interesting: is there a multiverse?
According to another hypothesis, the current theory of gravitation is incomplete. Unlike other fundamental forces, gravity does not have the opposite force – much like positive and negative electron charges. DESI can test the current theory of gravitation, which Albert Einstein developed more than 100 years ago, in unprecedented detail, because it can look far into the past. Astronomers can observe how gravity has worked for a long time and collect particles to shape the planets, stars, and galaxies we see. With this "film" cosmologists can check if Einstein's GRT is true. If not, the concept of dark energy may not be needed. Instead, we need a more complete theory of gravity that explains the acceleration of the expansion of the universe. Do you think Albert Einstein was right? Let us discuss this difficult topic in the comments and in our telegram chat.