Judy Martinez Deep space objects > Dark matter and dark energy
About 80% of the space is represented by material that is hidden from direct observation. We are talking about dark matter – a substance that does not produce energy and light. How did the researchers know it was dominant?
In the 1950s, scientists began to actively study other galaxies. During the analyzes, they noticed that the Universe is filled with more material than can be captured by the “visible eye”. Dark matter advocates showed up every day. Although there was no direct evidence of its presence, theories grew, as did the workarounds of observation.
The material we see is called baryonic matter. It is represented by protons, neutrons and electrons. It is believed that dark matter is capable of combining baryonic and non-baryonic matter. For the Universe to remain in its usual integrity, dark matter must be in the amount of 80%.
Elusive matter can be incredibly difficult to find if it contains baryonic matter. Among the contenders are brown and white dwarfs, as well as neutron stars. Supermassive black holes can also add to the difference. But they should have made more impact than what scientists saw. There are those who think that dark matter should be composed of something more unusual and rare.
Composite image of the Hubble telescope showing a ghostly ring of dark matter in the Cl 0024 + 17 galaxy cluster
Most of the scientific world believes that the unknown substance is represented mainly by non-baryonic matter. The most popular candidate is WIMPS (Weakly Contacting Massive Particles), whose mass is 10-100 times that of a proton. But their interaction with ordinary matter is too weak, which makes it harder to find.
Neutralinos are now very carefully considered – massive hypothetical particles that exceed neutrinos in mass, but differ in slowness. They have not been found yet. The lesser neutral axiom and untouched photons are also taken into account as possible options.
Another option is outdated gravity knowledge that needs updating.
Invisible dark matter and dark energy
But, if we do not see something, how to prove that it exists? And why did we decide that dark matter and dark energy is something real?
The mass of large objects is calculated by their spatial displacement. In the 1950s, researchers looking at spiral-type galaxies assumed that material close to the center would move much faster than distant material. But it turned out that the stars moved at the same speed, which means there was much more mass than previously thought. The studied gas in elliptical types showed the same results. The same conclusion suggested itself: if one were guided only by the apparent mass, then the galactic clusters would have collapsed long ago.
Model of the distribution of dark matter in the Universe 13.6 billion years ago.
Albert Einstein was able to prove that large universal objects are capable of bending and distorting light rays. This allowed them to be used as a natural magnifying lens. By investigating this process, scientists have managed to create a map of dark matter.
It turns out that most of our world is represented by a still elusive substance. You can learn more about dark matter if you watch the video.
If we talk about matter, then the dark one is undoubtedly the leader in terms of percentage. But in general, it takes up only a quarter of everything. The universe is rife with dark energy.
Since the Big Bang, space has launched a process of expansion that continues today. The researchers believed that eventually the initial energy would end and it would slow down. But distant supernovae demonstrate that space does not stop, but picks up speed. All this is possible only if the amount of energy is so huge that it overcomes the gravitational influence.
Clarification of the riddle
We know that the universe is mostly dark energy. It is a mysterious force that causes space to increase the rate of expansion of the universe. Another mysterious component is dark matter, which maintains contact with objects only with the help of gravity.
Scientists cannot see dark matter in direct observation, but the effects are available for study. They manage to catch light bent by the gravitational force of invisible objects (gravitational lensing). They also notice moments when the star orbits the galaxy much faster than it should.
All this is due to the presence of a huge amount of elusive substance that affects mass and speed. In fact, this substance is shrouded in mystery. It turns out that researchers can rather say not what is in front of them, but what “it” is not.
This collage shows images of six different galaxy clusters taken with NASA’s Hubble Space Telescope. Clusters were discovered while trying to investigate the behavior of dark matter in galactic clusters when they collide
Dark matter … dark. It does not produce light and is not observed in direct view. Therefore, we exclude stars and planets.
It does not act as a cloud of ordinary matter (such particles are called baryons). If baryons were present in dark matter, then it would manifest itself in direct observation.
We also exclude black holes, because they act as gravitational lenses that emit light. Scientists don’t observe enough lensing events to calculate the amount of dark matter that should be present.
Although the Universe is the largest place, it all started with the smallest structures. Dark matter is believed to have begun to condense to create “building blocks” with normal matter, producing the first galaxies and clusters.
To find dark matter, scientists use various methods:
- The Large Hadron Collider.
- instruments like WNAP and the Planck Space Observatory.
- direct view experiments: ArDM, CDMS, Zeplin, XENON, WARP and ArDM.
- indirect detection: gamma-ray detectors (Fermi), neutrino telescopes (IceCube), antimatter detectors (PAMELA), X-ray and radio detectors.
Delve into the mystery
More than once, scientists have not been able to literally see dark matter, because it does not come into contact with baryonic matter, which means it remains elusive for light and other types of electromagnetic radiation. But researchers are confident in its presence, as they observe the impact on galaxies and clusters.
Standard physics says that stars at the edge of a spiral galaxy should slow down. But it turns out that stars appear whose speed does not obey the principle of location in relation to the center. This can only be explained by the fact that stars are influenced by invisible dark matter in a halo around the galaxy.
The presence of dark matter is also able to decipher some of the illusions observed in the depths of the universe. For example, the presence of strange rings and light arcs in galaxies. That is, light from distant galaxies passes through the distortion and is amplified by an invisible layer of dark matter (gravitational lensing).
So far, we have a few ideas about what dark matter is. The main idea is exotic particles that are not in contact with ordinary matter and light, but have power in the gravitational sense. Now several groups (some use the Large Hadron Collider) are working on creating dark matter particles to study in the laboratory.
Others think the influence can be explained by a fundamental modification of gravitational theory. Then we get several forms of gravity, which is significantly different from the usual picture and the laws established by physics.
The expanding universe and dark energy
The dark energy situation is even more confusing and the discovery itself in the 1990s became unpredictable. Physicists have always thought that the force of gravity works to slow down and may one day suspend the process of universal expansion. Two teams took up the measurement of speed at once and both, to their surprise, revealed acceleration. It’s as if you are throwing an apple into the air and you know that it must fall down, and it moves farther and farther away from you.
It became clear that acceleration was influenced by some force. Moreover, it seems that the wider the universe, the more “power” this force gets. Scientists decided to designate it as dark energy.
If dark matter can be somehow explained, then there is nothing at all about dark energy. Some people really believe that this is the fifth fundamental force – the quintessence.
However, the known properties of dark energy are consistent with the cosmological constant created by Albert Einstein in general relativity. The constant acts as a repulsive force that counteracts gravity and keeps space from destruction. Later, Einstein abandoned it, because observations revealed the expansion of the Universe (it was calculated for a static one).
But, if now we add dark energy as a constant to accelerate the expansion of the Universe, then this process can be explained. But all this does not give an understanding of why this strange force exists at all.
