If you think that the entire universe is made up of matter that can be seen or detected, you are dead wrong. In fact, almost 85 percent of the matter present in the universe is thought to be composed of “dark matter,” a form of matter that scientists are yet to directly observe.
Since dark matter has not been observed by human beings, many people wonder how we can be so sure of its existence. Dark matter is inferred to exist by observing its gravitational effects. In fact, some of the observed gravitational effects cannot be explained unless one considers the presence of dark matter in addition to the observable matter.
Without the existence of dark matter, most galaxies would have flown apart rather than rotate. Scientists classify dark matter into three categories — cold, warm, and hot. But these designations do not indicate the temperature of the dark matter, but its velocity.
“Dark matter is the scaffolding that holds galaxies together; they spin way too fast to hold themselves together… The stuff that makes up you and I makes up no more than 5 percent of the universe. We know of two big dark things that are out there; we’ve got dark matter holding things together and dark energy pushing things apart,” The Sydney Morning Herald quotes Tamara Davis, an astrophysics professor at the University of Queensland.
And as to the question of why dark matter cannot be observed, one needs to understand how human perception works. Human beings can only perceive matter that consists of charged particles. Dark matter essentially refers to particles that carry no electromagnetic charge. As a result, we are never able to see it no matter how advanced an optical detection instrument we use.
Many people assume that dark matter must be useless for human beings since we cannot perceive it. After all, how are we supposed to use something that we cannot sense? The fun fact is that there are large amounts of research going on to discover dark matter precisely because of its potential to revolutionize the way we live.
Applications of dark matter
An interesting way scientists hope to use dark matter is as a source of energy. A physicist named Jia Liu proposed in 2009 that dark matter can be used as a fuel to power spacecraft on long missions. This is largely dependent on the assumption that dark matter is composed of neutralinos, particles that have no electrical charge.
The neutralinos are also antiparticles. As such, when they collide in specific conditions, they produce a large amount of energy. As per estimates, just one pound of dark matter is sufficient to produce energy that is equivalent of 5 billion times the energy released by an average dynamite explosion.
“One advantage of the dark matter engine would be that a spaceship wouldn’t need to carry much fuel, because it could gather more along the way from the abundant dark matter in parts of the universe. And the faster that the rocket travels, the more rapidly it will scoop up dark matter and accelerate,” says an article at HowStuffWorks.
A dark matter engine that approaches light speed will change the fate of space travel since we will be in a position to cover large distances in a short period of time. While a trip to the nearest star, Proxima Centauri, would have taken thousands of years using current fuel technologies, a dark matter engine will make the travel possible in just five years.