12

Feb 20

Dark matter – the hidden part of the Universe

Dark matter - the hidden part of the Universe

Dark matter or black matter, sometimes called transparent matter, is one of the greatest mysteries for today’s science, a concept advanced by astrophysicists, a concept that denotes a hypothetical type of matter and which is supposed to represent the bulk of matter existing in the Universe.

More specifically, research over time led to the unanimously accepted conclusion that visible matter in the Universe represents about 4%, while 96% of what Universe represents is impossible to perceive, it’s dark matter and energy. As dark matter doesn’t absorb nor emit light or electromagnetic radiation, it can’t be seen with the naked eye or telescopes.

Higgs boson or the “God particle”

From the Big Bang to the present day, the universe has been continuously expanding and millions of galaxies were created, formed. How long will this process take? Does it slow down? Does it accelerate? When it will come to an end? The phenomenon of expanding universe is treated in Einstein’s space-time model, but between the reality of the cosmos and the theoretical models there are a lot of mysteries.

A step forward in understanding and explaining cosmic phenomena was made in 2013 when researchers at CERN (the European Organization for Nuclear Research) announced that they had discovered a subatomic particle, the Higgs Boson (named after physicist Peter Higgs who postulated its existence when he formulated the elementary particle theory, the “Standard Model”). The Higgs boson was called the “God particle”, without any religious connotation, but only to point out that if this elemental particle, the Higgs Boson, wouldn’t exist, matter wouldn’t exist, as the Higgs Boson gives things mass, it therefore gives them gravity.

the higgs boson

Elementary / fundamental particles, the basic units of the Universe, are fermions (leptons, quarks) and bosons. For example, the photon is part of the boson category. It is assumed that the boson is the result of the collision of two very high energy protons; the lifetime of such a particle being very short, hence the difficulty of proving its existence.

Therefore, if the “God particle” wouldn’t exist, it wouldn’t give objects mass; the perceptible Universe, as we know it today, wouldn’t exist either. A second conclusion, derived from this, is that dark matter is not made up of neutrons, protons, or electrons.

Joseph Lykken, one of the physicists involved in the CERN project, said that it’s quite possible that at some point, at the speed of light, another “explosion” such as the Big Bang would take place, giving rise to an “alternate” universe that would destroy the existing one.

Dark matter and the accelerated expansion of the Universe

Dark matter and the accelerated expansion of the Universe

So, about 15 billion years ago, just a hundredth of a second after the Big Bang, atomic particles – neutrons, protons, electrons appeared. At the end of a second, the nuclei of deuterium (stable isotope of hydrogen) were formed by associating a proton with a neutron and an electron, then the helium nuclei (two protons and two neutrons); subsequently, the creation slowed its pace.

In the 1990s, however, several teams of researchers have announced that, as a result of various measurements and analyzes, it’s certain that the universe appears to be expanding at an increasing rate and not as previously believed that the expansion of the cosmos will gradually slow down, after which the Universe will enter a contraction process. An invisible force seems to generate another evolution of the Universe than anticipated by scientists.

On the other hand, the observations related to star and supernovae clusters (supernovae are stellar explosions with stronger luminous effects than of an entire galaxy, releasing as much energy as the Sun over its lifetime), the tendency to decrease gravitational force and so on, all lead to the dark matter and to what Einstein had intuited when he introduced the “lambda constant” / “the cosmological constant” – the energy of vacuum into his equations. Obviously, dark matter should not be mistaken for dark energy, but both notions fall into the category of hypotheses that determine the accelerated expansion of the Universe. If the visible matter represents 4.9% of the universe, the rest is assumed to be dark matter (about 26.8%) and dark energy (68.3%).

Dark matter – several hypotheses

Dark matter - several hypotheses

No theoretical model, so far, is convincing enough, in the absence of evidence, about what dark matter means. But with all the unknowns, the fact that it exists is supported by most of the researchers, which means that the Universe is even more surprising, more fascinating than the astronomers have described it or than we could ever have imagined. Here are some of the explanations given by experts in astrophysics on the composition of dark matter.

  • WIMPs, the acronym for Weakly-interacting massive particles might be translated as “massive particles that interact poorly”, hypothetical particles that possess mass and interact very poorly with baryonic (ordinary) matter. In today’s cosmological models, the concept of matter is defined in two hypostases: baryonic matter (protons, neutrons, electrons) and non-baryonic matter (dark matter / transparent matter) which only interact through gravity with the other components of the universe. Various devices have been designed to capture the moment of interaction between a WIMP particle and ordinary matter, but no results yet.
  • ADMX (The Axion Dark Matter Experiment) is an ongoing project of researchers at the Center for Experimental Nuclear Physics and Astrophysics (CENPA) at the University of Washington, based on the idea that axion is a hypothetical elemental particle of dark matter. Experts hope they will find this very light particle which interacts very poorly with baryonic matter, hence the difficulty of detecting it.
  • According to other theories, dark matter would come from the primordial black holes. In order to verify this hypothesis, the Kepler telescope was designed to measure the brightness variation of the different stars, because when a hypothetical primary black hole would pass in front of a star, the gravitational lens effect, manifested by the sudden increase of the brightness of that star, might be created. Over 150,000 stars are monitored, but no notable results yet.

CERN – Dark Matter, a three Nobel Prize mission

CERN - Dark Matter, a three Nobel Prize mission

Experts at CERN (European Organization for Nuclear Research) believe that trying to prove the existence of matter and dark energy is far more difficult than the discovery of the Higgs boson, that is a mission of modern physics not for one, but for three Nobel Prizes.

When the search for the Higgs Boson (the God Particle) began, the deputy director of the institution confessed, they knew the way research should be directed, while dark matter and dark energy are only known to exist and to greatly influence the expansion of the universe.

According to CERN, a path of searching this mysterious dark matter is the so-called “dark massive photon A”. Common photons are known to represent elemental particles of electromagnetic radiation with mass and zero electrical charge that cannot exist in a rest / static state. According to recent theories on dark matter, there must be another photon with a mass that would make visible matter communicate with the invisible matter, but such a particle has not yet been identified, although research has begun since 2016.

A Chinese satellite looking for dark matter

A Chinese satellite looking for dark matter

The research activity of Chinese specialists in astrophysics is increasingly intense. The first Chinese satellite launched for this purpose in 2015 – DAMPE – provided the first results in detecting, in the first 18 months in orbit, over 1.5 million electrons and positrons (anti electrons – elementary, unstable particle having the same mass as an electron and with a positive electric charge equal in absolute value to the electron charge), high energy, at an altitude of 500 kilometers, and a strange decrease in the number of particles beyond a certain amount of energy, a kind of “rupture” whose cause has not been deciphered.

About the source of cosmic rays that continuously bombard the Earth, it is known that they partly originate from massive stars (supernovae) explosions, others from pulsars (extremely dense stars that rotate very fast around their axis). Or perhaps another source could be dark matter, which is why the satellite was launched and scheduled for such measurements.

International competition in deciphering the mystery of dark matter

In 2015, 100 kilometers from Rome, Italy, under the Abruzzo mountain range, in an underground laboratory in Gran Sasso, protected by 1400 meters of rock in height, a device for measuring particles of dark matter was installed, over 100,000 particles of such hypothetical matter crossing one square centimeter each second.

It is believed that this device, Xenon1T, would have the best chance to identify WIMPs because it is equipped with a kind of isothermal bath containing a ton of liquid and gaseous xenon in order to eliminate any jamming originated from natural radioactivity. The advantage of xenon is that it’s the heaviest gas on the earth, it’s inert and very dense, it does not interact with photodetectors, it has no natural isotope. The Gran Sasso tool cost $ 15 million, while other similar tools are also in use in 21 other laboratories around the world, in the US, Japan, China, Colombia, etc.

The fact that about 96% of the Universe is currently almost unknown, assuming that the Universe is only dark matter and energy, besides the other aspects of the birth of the Universe, the primordial explosion, the evolution of the galaxies, the planets , the expansion of the cosmos, which are rewritten in our age, shows how spectacular and mysterious the Creation is.  For the human mind, all this is a huge challenge, in an attempt to imagine the unimaginable and perhaps move to another level of knowledge.

Be Sociable, Share!

No comments yet, be the first.

Leave a Reply

Time limit is exhausted. Please reload CAPTCHA.