Why dark matter continues to astound scientists
The idea of dark matter was discovered in the same way as many other celestial bodies - at least since Newton’s laws of gravity were forged. After Isaac Newton, scientists understood the kind of orbital activity they should observe from objects in the universe, based on their mass.
The birth of dark matter
During the 1930s, an astronomer named Fritz Zwicky from Switzerland saw distant galaxies in a cluster were orbiting each other too fast for the visible mass they were carrying. He concluded that this discrepancy could only be explained by unseen material exerting additional gravitational forces on these galaxies. He later called it ‘dark matter.’
Since that time, researchers have often confirmed that this elusive substance has to exist throughout the cosmos. Amazingly, it is estimated to be six times more abundant than the ordinary matter that makes up everyday things like stars and even human beings.
Dark matter questions
Although dark matter is scattered all through the universe, it continues to confound the brightest minds in all of science. Let us examine five of the most fascinating questions about dark matter that remain a mystery.
So what exactly is dark matter?
Believe it or not, even though experts are quite sure of its existence, they are not sure what dark matter even is. Initially, scientists thought that the absence of mass in the universe was due to black holes and distant, faint stars. But observations have found nowhere near enough of them to account for the influence of dark matter.
The one leading contender to describe dark matter is a hypothetical particle known as the Weakly Interacting Massive Particle (WIMP). A WIMP would act as a neutron but would be some 10 to 100 times as heavy as a proton. Unfortunately, this conjecture only leads to more questions.
Does dark matter consist of more than one particle?
The ordinary matter that we are familiar with is comprised of several particles like electron and protons. Furthermore, all ordinary matter has an entire bevy of exotic particles like neutrinos, pions, and muons.
Needless to say, several researchers see no reason not to believe that dark matter is just as complicated as normal matter. Seeing how it makes up some 85% of the total matter within the universe.
It would be presumptuous and reckless to assume that just one type of particle makes up all of dark matter. A more likely scenario would begin with combining dark protons with dark electrons to make dark atoms. And from there, an infinite number of configurations could exist.
As one might imagine, physicists have considered countless possibilities, but trying to find a way to confirm or deny any of them is another story altogether.
Can we detect dark matter?
If WIMPS makes up dark matter, which many believe, they are all around us, yet continue to be barely detectable and invisible. While they don’t interact with regular matter very often, there is a possibility that a single dark-matter particle might collide with an ordinary particle while traveling through space.
Scientists have been conducting experiment after experiment to examine and better understand vast numbers of ordinary particles. They perform these studies deep underground, where they would be protected against interfering radiation that would yield a false dark-matter-particle collision. The only problem is that they haven’t made a single credible discovery after decades of searching.
In 2018, the Chinese PandaX experiment observed a WIMP nondetection⁴. It seems very possible that dark-matter particles are either considerably smaller than WIMPs or don’t have properties that make them easy to observe.
Does dark matter have an electrical charge?
A signal that originated from the beginning of the universe leads some physicists to conclude that dark matter has an electrical charge. During the universe’s early stages, radiation from the stars had a wavelength of 21 centimeters - which was around 180 million years after the Big Bang occurred.
At about the same time, the starlight radiation was absorbed by cold hydrogen. When the WIMP radiation was observed in 2018, its signature indicated that the hydrogen was considerably colder than scientists had thought.
A possible explanation is that dark matter possessing an electrical charge might pull heat away from the hydrogen.
Can normal particles decay into dark matter?
Let’s consider neutrons, which are particles from ordinary matter that has a limited lifetime. After about 14.5 minutes, a single neutron that has been freed from an atom will decay into an electron, a proton, and a neutrino.
However, two different experiments have reported slightly different lifetimes for this decay. They were different from an average of around 9 seconds.
Some physicists claim that if neutrons would decay into dark matter particles about 1% of the time, it could possibly account for this anomaly. And as with most dark matter experiments, research teams have not detected a dark matter signal from neutrons. But many still believe that the particle decay theory should be further examined in different scenarios.