Dark matter is what keeps physicists up at night. First identified in the 1930s “dark matter” remains as elusive today as it was then. Dark matter is known to affect the movement of galaxies and other celestial bodies. While physicists can measure its effects, what it is made of is still undefined.
Not that physicists are not trying or they lack ideas, but none seem to completely explain dark matter.
Top 9 Dark Matter Explanations
- Sterile Neutrinos
- Mirror World Dark Matter
- Asymmetric Dark Matter
- Extra Dimensional Dark Matter
- Composite Dark Matter
The current front runner for explaining dark matter, WIMPs encompass many dark matter particles several of which are contained in this list. WIMP stands for “weakly interacting massive particles.” They are thought to interact with one another through the weak force of radioactive decay and only have 1 to 1000 times the mass of a proton.
Despite looking for them on both earth and in space, physicists are having a hard time finding clear connections to WIMPs and the effects of dark matter.
Physicists have a really good idea of how much dark matter exists based on galaxies observation, although they have never actually detected dark matter. Observations of inner regions of galaxies do not align with their models.
These models often assume that dark matter does not interact with itself. To remedy this, SIMPs were introduced. Strongly Interactive Massive Particles seem to eliminate the discrepancy of these inner versus outer galaxies. This would also explain the photon signal that comes from galaxy cluster.
Neutralinos come from the theory of Supersymmetry. Basically Supersymmetry says that every particle has a “super” partner that fills the holes in the standard model. But it has yet to be observed.
Some of these “super” partners like those of the Z boson and photon have characteristics similar to dark matter. Of these the Neutralino is most likely to be the neutralino and would solve two major issues in physics.
- Tell us the identity of dark matter
- Give us proof of Supersymmetry
However it also opens up a ton of new questions, essentially telling us there is a lot more particles to be discovered.
Neutrinos are odd enough being almost massless, the ability to shape-shift and pass through and entire planet without hitting anything, but they have an even more strange counterpart, the sterile neutrino.
These sterile neutrinos would be virtually unresponsive to particles around them. So much so that they may never collide in the entire age of the universe. This aversion to interaction would make them almost impossible to detect, but they may decay into photons, a particle we can easily detect. Hopefully the new ASTRO-H Japanese telescope will help shed some light on the decaying sterile neutrino hypothesis.
First discovered in the early 1980s, axions are experiencing a surge in popularity as the answer to dark matter. The University of Washington’s Axion Dark Matter Experiment (ADMX) is searching searching for these particles by using a strong magnetic field to try and turn them into photons. With a greater ability to detect these particles, scientists are dusting off this theory and searching for new ways to detect them.
Mirror World Dark Matter
While the mirror world dark matter theory will prove to make defining dark matter almost certainly impossible it does seek to explain the phenomenon. This theory basically says that dark matter exists in a separate universe will similar elemental particles but only exert the force of gravity. Thus exerting pull on our universe but no other signs. This works well with what we do know about dark matter (its gravitational pull) but does little to satisfy any why or how questions.
Asymmetric Dark Matter
Asymmetric dark matter is basically just the anti-matter, matter scenario. In this theory, dark matter, collided with anti-dark matter thus leaving behind what we see today as dark matter.
Extra Dimensional Dark Matter
A slight variation of the Mirror World Dark Matter Theory, Extra Dimensional Dark Matter would simply exist in a fourth spacial dimension that we have yet to see. This fourth dimension would be too small for us to see a particle’s movements with it, rather we would see multiple particles with the same charge but different masses. Proving this theory would support String Theory which needs extra dimensions to work.
Composite Dark Matter
Composite Dark Matter is very simply a combination of the above theories. Since none of them fill the bill completely it might be several of them actually being the answer to the question: “What is dark matter?”