96 percent of the universe is made of mysteries. The type of matter that we’re used to- things composed of atoms- makes up only 4 percent of the universe. When scientists were measuring the mass of galaxies they found weight that was unaccounted for even after they’d weighed stars, planets and other spacely things. We call the unknown substance responsible for the extra weight ”dark matter.”
Scientists began to look at galactic clusters, knots of galaxies, hypothesizing that the mass that was unaccounted for was hot gas. They found vast clouds of superheated gas but not enough to make up for the missing mass. They knew there was something else there because the gravity of the galactic clusters alone wasn’t enough to keep the gas from escaping the galaxies.
Scientists aren’t really sure what dark matter is but, they know for sure what it’s not. Scientists know for sure that dark matter isn’t red, white or brown dwarf stars. It also isn’t cold or hot gas. Neutron stars and black holes? Not those either. The term “dark matter” is just a placeholder for now, like the unknown variable of an algebra equation, the “X” or “Y” of the universe.
Scientists estimated the amount of dark matter and atom-based matter in the universe and entered it into a computer which drew a map of dark matter’s location in the universe based on the information provided. In the simulation, dark matter is shown as weblike material woven in with regular matter, it could be everywhere. Astronomers have worked to create a similar dark matter map based on direct observation of galaxies’ mass.
Based on the evidence, most astronomers agree that dark matter exists. But they have more questions than answers. The biggest question, dare we say one of the biggest in all of cosmology is: Is it an undiscovered type of matter, or is it ordinary matter that we have difficulty observing? There is a lot of difficulty in knowing what dark matter is. Some scientists even believe that dark matter doesn’t exist and that we could just be misinterpreting the laws of gravity. Astronomy researcher Stacey McGaugh came up with an alternative theory of gravity.
“We infer dark matter to be there. We infer it from its gravitational effects,” said McGaugh in an interview with Vice. McGaugh thinks that gravity’s effects might be different at different places in the universe.
In addition to the mysteries of dark matter, there is also dark energy. Contrary to scientists’ expectations, the expansion of the universe isn’t slowing down due to gravity, it is actually accelerating due to some unexplained outward force. Like dark matter, the term dark energy is used as a placeholder to refer to something we’re unsure of. We call the force that’s accelerating the expansion of the universe dark energy
96% of the universe is made up of things that we are still unsure of-73% dark energy and 23% dark matter. The rest is normal matter made up of atoms, such as stars, that we do understand. Credit: http://www.nasa.gov/vision/universe/starsgalaxies/Collision_Feature.html
The graph above shows the relationship between the time Earth was created and how the universe has expanded since then. Credit: http://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy/
In conclusion, maybe we don’t know what’s in our universe as well as we thought we did. There could be endless possibilities of what the universe holds. Most scientists agree with the statement that dark matter exists. Of course there are still some that doubt its existence and would even go as far as to question our perception of the laws of gravity. A rhetorical question that comes to mind is “You can’t see air but, does it not exist?” Whether you choose to believe in dark matter or not, there is still something thats fills the missing mass of the universe.