About Dark matter

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Protons, neutrons, and electrons are grouped together to create atoms, which are the building blocks of the observable cosmos, which includes the earth, sun, stars, and other celestial bodies. These atoms make up the ordinary matter, which accounts for 5% of the universe's mass. About 25% of the universe is made up of dark matter, an invisible kind of substance. Dark energy, a force rejecting gravity, makes up the rest of the cosmos (Choi, 2016).

Theoretical particles known as "dark matter" are different from the neutrons, electrons, and protons found in conventional matter. Since this substance is non-luminous and doesn't emit or absorb energy, scientists have never directly observed it. Its existence explains several mysterious astronomical observations made throughout the universe. Its name is derived from its invisibility to the entire electromagnetic spectrum since it does not release or absorb any electromagnetic radiation like a light. This characteristic makes dark matter extremely had to observe. Researchers have been able to conclude its occurrence through the gravity effect it has on visible matter such as Baryonic matter motions, gravitational lensing, influence on galaxy formation, and the universe microwave background (Panek, 2011).

This matter is classified into the cold matter, warm matter and hot matter. This classification is based on the velocity, not the actual temperature. Since dark matter is not observable, the velocity is measured by how far the corresponding bodies moved by invisible activities in the ancient cosmos before slowing down due to expansion of the universe a distance known as FSL (Fast streaming length). Cold dark matter comprises of particles having a lower FSL lower than protogalaxy. Dark matter contents could be black holes, brown dwarfs, and axions. The warm dark matter is made of particles having a comparable FSL with the size of protogalaxy. The hot matter is composed of particles having larger FSL than the size of protogalaxy. Nutrinos is an example of a particle with these qualities. It interacts with observable matter through gravity as well as weak force thus hard to detect. Hot matter is not capable of supporting cluster formation in the universe and particles slow early

Example and evidence

Since scientists cannot see dark matter directly, they use indirect ways to investigate it such as the use of gravitational lensing. Any light going through the lens behaves the same way as the optical lens. Usually light from far bodies pass through the cluster, the gravitational pull of the matter in the cluster makes light to change direction making the light to look like its originating from another source instead of its actual source. The level of bending explains the presence of dark matter. Other scientists, us Hubble space telescope to observe the gravitational lensing. In addition to indirect ways, NASA uses Fermi gamma-ray space telescope. The telescope observes gamma radiations released during collision of dark matter component particles.

Vera Rubin made a groundbreaking discovery in the 1970s by measuring the rotation speeds of stars in the galaxies. The stars were orbiting too fast that the galaxy should have flung apart, but they were stable instead. This behavior implied there could be some invisible matter inside the galaxies gravitationally holding them together (Sutter, 2017).

Rotation curves

Winding cosmic systems revolves the galactic focus. The light emitting mass thickness of the spiral universe diminishes from the middle to the edges. If radiant mass makes the matter, at that point, we could consider the world as a middle point and assess mass orbiting it. According to Kepler's Second Law, the rotation speeds diminishes with the distance when originating from the center, like the universe. However, this is invisible since the cosmic orbit graph stays constant for far off from the center according to the available information. Assuming Kepler's rules, the approach to explain this condition is to infer that the density circulation in spiral galaxy differs from the solar system since there exist vast amounts of dark matter occupying the galaxy surroundings.

Velocity dispersions

Stars inbound frameworks must comply with the viral hypothesis. The hypothesis of the estimated velocity appropriation can be utilized to gauge the mass distribution in the framework like elliptical cosmic systems. With some few exemptions, the velocity dispersion estimates of elliptical galaxies don’t rhyme with the predicted dispersion based on the observed mass distribution even if we assume complicated stellar orbit distributions. These discrepancies are caused by the existence of invisible matter

B curve is the observed velocities instead of the expected A curve.

Structure formation

After the big bang, density disruptions caused collapsing of galaxies and stars. Before structure formation, Friedman solution to Einstein’s relativity theory depicted a cosmos universe. Gradually small bodies developed will condense the uniform universe to form galaxies and stars. Normally radiation affects matter and radiation was the dominant component in the universe during the formation of the universe. They wash out density perturbations and don’t allow condensation to form structure. So if only ordinary matter occupied the universe, there would be no time for growing massive perturbations to form clusters and galaxies. Since Dark matter is unaffected by radiations, it allowed these perturbations to grow. This features created gravitational potential which attracted collapsing ordinary matter speeding up the formation of structures (Gates, 2011).

Redshift distortions

Substantial cosmic redshift surveys can be utilized to create 3D maps of the galaxy distribution. Slight distortions are observed in the charts since distance estimations are based on observed redshifts. The redshifts contain strange velocities in added to the Hubble expansion term. Super clusters are growing though slower than the cosmic mean because of their gravitational characteristics, and the voids also expand faster than the calculated average. In the redshift outline, galaxies ahead of a cluster have more radial velocity approaching it as well as having redshifts marginally greater than their distance suggests. Galaxies behind the clusters experience redshifts low based on their distance. These impacts make the squashing of super clusters and stretching of voids while angular positions maintain. These effects are not detected for structures because the exact shape is unknown but can be estimated by the effect it has on the surrounding visible objects.

Controversy in dark matter

Another approach to gravity which challenges Albert Einstein as well as suggesting that dark matter does not exist is in controversy with other scientists’ point of view. Many of scientists concur that gravity behaves according to the rules set by Isaac Newton’s law of gravity and Einstein’s relativity idea. Observations on the universe indicate that the motion of galaxies cannot be explained using gravity attraction of the ordinary matter thus the believing in invisible dark matter exerting its attraction (Anderson, 2016).

A team of scientists studying matter distribution in galaxies and explain their observations doing away with dark matter. Margot Brouwer of Leiden University with her colleagues explains the gravity lensing observed in the galaxies. How they deflect the light of far galaxies according to Einstein's theory in measuring their dark matter. They observed a gravity model could account lensing without using the dark matter idea.

Erik Verlinde of Amsterdam University developed a model of gravity that uses quantum mechanics, string theory, relativity, and information theory. It builds a diverging theory opposing the modified gravity. Verlinde’s calculations support the new arguments that don’t resort to free parameters. They insist the parameters are values that can be adjusted to match a theory and observation. Brouwer suggests the initial dark matter theory needs four free parameter adjustments to explain the data. Verlinde's theory does not have any metrics, but the dark matter has. This property makes Verlinde's prediction better performing.


Dark matter is a great mystery in the universe. It is believed to be invisible and makes up five out of six of all the matter in the universe. Its rarely interacts with the surrounding ordinary and observable matter. Scientists believe dark matter is not made of the same materials as the ordinary matter. It lies outside the standard structure of a physical particle. Currently, the composition of dark matter does not interact with other particles and also with themselves.

Works Cited

Anderson, Mark. "First Test of Rival to Einstein’s Gravity Kills off Dark Matter." New Scientist, New Scientist, 15 Dec. 2016, www.newscientist.com/article/2116446-first-test-of-rival-to-einsteins-gravity-kills-off-dark-matter/.

Choi, Charles Q. "Controversial New Theory of Dark Matter Could Rewrite History? PBS." NOVA Next, PBS.org, 13 Apr. 2016, www.pbs.org/wgbh/nova/next/physics/interacting-dark-matter/.

Gates, Evalyn. Einstein's Telescope: The Hunt for Dark Matter and Dark Energy in the Universe. 1st ed., W.W. Norton & Co, 2010.

Panek, Richard. The 4 Percent Universe: Dark Matter, Dark Energy, and the Race to Discover the Rest of Reality. 1st ed., Mariner Books, 2011.

Sutter, Paul. "The Matter with Dark Matter." Science and astronomy, Space.com, 5 Sept. 2017, www.space.com/37937-evidence-for-dark-matter.html. Accessed 13 Dec. 2017.

April 13, 2023

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