Dark matter is one of the unsolved mysteries in physics and astrophysics.

This hidden matter, which is believed to form as much as 85% of the total matter in the universe, was first introduced about 60 years ago by the astronomer Fritz Zwicky. He developed and later proposed his “missing matter” theory to explain why stars rotating far away from the center of a galaxy move much more quickly than expected, taking account of the visible mass of the galaxy.

What Zwicky had called missing matter is now commonly called dark matter. Dark matter cannot be directly observed by any scientific observation devices, but its existence has been suggested by its gravitational effects.

What Is Dark Matter?

As to the nature of the dark matter, there have been many debates and speculations by physicists and some candidates include:

  • Weakly Interacting Massive or Low-Mass Particles. They include particles that have a very weak interaction with the rest of the matter, but with a finite mass contributing to the overall mass of the galaxy or universe. Due to their nature, they cannot be “seen” or easily detected and so can be categorized as dark matter. A good candidate is a tiny ghost particle named neutrino that exists in large numbers throughout the universe. Neutrinos are weakly interacting low-mass particles that because of their abundance in the universe can be a good candidate.
  • Massive Astrophysical Compact Hollow Objects (MACHOS): They include any massive object that can contribute to dark matter. Black holes, including mini-black holes, that may exist in large numbers in the universe are categorized as MACHO. Contrary to the first candidate, they are very massive and have a high gravitational field. But due to the same reason, they cannot be easily seen as they swallow passing by beams of light.
  • Brown dwarfs are other candidates. They include objects with masses higher than Jupiter but lower than the Sun that virtually do not radiate any light. It is not yet clear how many of these bodies exist in the universe and if they contribute to dark matter.

New Discovery Sheds More Light on the Question of What Is Dark Matter

A new discovery suggests that dark matter may not be as dark as it was previously imagined. Indeed, for the first time and following comprehensive research on four colliding galaxies in a galactic cluster named Abell 3827, researchers claimed to have discovered dark matter to be “slowing down” after interaction with other dark matter.

This phenomenon that contradicts previous investigations suggests that dark matter may be capable of interacting with a force other than gravity. Last August, a team of astronomers led by Dr. Richard Massey of Durham University used the Hubble Space Telescope to take photos of a massive collision between four distant galaxies.

All galaxies are sources of dark matter and more or less the same ratio of %85 applies to every galaxy. The detailed analysis of the collision led the researchers to the conclusion that during the course of the collision, the existing dark matter ended up in a different place from the stars in their associated galaxy.

This suggested that the dark matter might have been influenced by a force other than gravity. Although dark matter is invisible, it can be detected by the way it bends the light beam emerging from an even more distant galaxy.

More Mysteries around Dark Matter

There are still many other secrets regarding the dark matter that are yet to be resolved. For example, some investigations suggest that colliding dark matter constituents, or so-called dark matter particles, may create an unknown type of radiation named “dark radiation”.

The nature of such radiation if ever exists is yet to be discovered, but the work to find this new radiation has already started and scientists have placed detectors in different underground locations of Earth for detecting dark radiation.

In order to answer the question What is dark matter? and have a clear idea of what its nature and constituents are, much more research has to be done, but the recent discoveries are promising and in the near future we may witness the final answer.


  1. Dark Matter Can Interact With Itself, Galaxy Collisions Show
  2. Are Supermassive Black Holes Hiding Matter?

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This Post Has 3 Comments

  1. mpc755

    Dark matter is not a clump of stuff that travels with the matter. Dark matter fills the space unoccupied by particles of matter and is displaced by the particles of matter which exist in it and move through it. Dark matter strongly interacts with matter. Dark matter is displaced by matter.

    [0903.3802] The Milky Way’s dark matter halo appears to be lopsided

    “the emerging picture of the dark matter halo of the Milky Way is dominantly lopsided in nature.”

    The Milky Way’s halo is not a clump of dark matter traveling along with the Milky Way. The Milky Way’s halo is lopsided due to the matter in the Milky Way moving through and displacing the dark matter, analogous to a submarine moving through and displacing the water.


    “Since 1954, when this passage was written, I have come to support wholeheartedly an hypothesis proposed by Bohm and Vigier. According to this hypothesis, the random perturbations to which the particle would be constantly subjected, and which would have the probability of presence in terms of [the wave-function wave], arise from the interaction of the particle with a “subquantic medium” which escapes our observation and is entirely chaotic, and which is everywhere present in what we call “empty space”.”

    “The interaction of the particle with a “subquantic medium”” is another way of describing a strongly interacting dark matter.

    In a double slit experiment the particle is always detected traveling through a single slit because it always travels through a single slit. It is the associated wave in the strongly interacting dark matter which passes through both.

    What ripples when black holes collide is what waves in a double slit experiment, the dark matter.

    Einstein’s gravitational wave is de Broglie’s wave of wave-particle duality, both are waves in the dark matter.

    Dark matter displaced by matter relates general relativity and quantum mechanics.

  2. Yasmine

    That’s why I such adore science : it’s constantly in evolution as human kind 🙂
    If I wasn’t such geneticly programmed to be a doctor I would really like to specialize myself into astrophysics which am attrected to since I was 5 🙂

    1. Bob

      You are right and the subject is so attractive and that is why I majored in it.

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