Over the decades, mankind has gained a larger understanding of the many bodies that make up the universe. There is, however, one query that sends modern scientists into confusion: dark matter.

Dark matter is currently defined as “an invisible and hypothetical type of matter that doesn’t interact with light or other electromagnetic radiation.”(Wikipedia) This matter makes up about 27% of the universe but is exceedingly difficult to study as it doesn’t interact with light, which means that we are unable to see it. We are able to “see” it in a way, as it interacts with ordinary matter through gravity. 

There are currently many circulating theories about what dark matter could be, or even that it could be made up of many different things. There are a few that seem to be at the forefront of scientists’ minds.

One of these favored theories is called a WIMP. Many will think that it’s not exactly a name one would expect for such a mysterious subject, but it explains itself. WIMP stands for Weakly Interacting Massive Particles- these particles are candidates for dark matter because they don’t interact with light but are able to interact through gravity. WIMPs release gamma rays when they interact with each other, so scientists are keeping a close eye on any signs of gamma rays near dark matter that could prove their correlation. (NASA)

Another proposal for what this matter may be is a hypothetical particle called an axion that is thought to be high-mass and low-energy, like dark matter. Scientists have found evidence of their existence over the years, since they were first theorized in 1977 as a solution to the CP problem in particle physics.

Yet another theory, proposed by physicist Steven Hawking, is that primordial black holes, which vary greatly in size, formed at the beginning of the universe before collapsing and becoming dark matter. Scientists have theorized that a primordial black hole could pass through our solar system every ten years, which provides a rare but valuable instance to study them in a very direct manner. 

In stark contrast to ideas of dark matter being some kind of particle, one scientist Rajendra Gupta, believes that perhaps the answer to our questions about unexplained shifts in gravity isn’t the presence of dark matter, but the absence of something else. Gupta thinks that dark matter is actually that light loses energy and natural forces weaken over time. He says that the accelerated expansion of the universe is not because of dark matter or energy, but because of the weakening of forces. His theory also suggests that the universe is twice the age we thought it to be. 

Gupta’s theory is against our understanding of the universe, so much more evidence is needed to prove him right. This could, if proven correct, provide a different framework for thinking about the universe.

So, while we don’t have a straightforward answer to what this mysterious type of matter is, we are certainly on the right path to a breakthrough. Understanding dark matter is a fundamental piece of understanding how and why our universe is expanding at an accelerating rate(NASA) By knowing what particles are linked with dark matter, scientists can more effectively study our universe and map the areas of dark matter. This in turn allows us to create explanations for dark energy, much like dark matter but energy pushes things apart rather than pulls them together with gravity. Overall, there is much to be discovered about the universe from this question of what dark matter could be.