Dark matter is probably the biggest existential question of our time.
And as scientists stare glossy-eyed into the dark matter abyss and ponder its nature, non-scientists are already trying to monetize it in their minds as the perfect fuel that would allow us to conquer space.
An honest physicist will tell you they have no idea what dark matter is, really. But what it could be is a vast world of potential that would lift the veil on a million universal mysteries - at the same time as potentially fueling our path to other planets.
What We Don’t Know About Dark Matter
Dark matter constitutes around 27 percent of the universe. This compares with just 5 percent for normal matter, which refers to the sort of matter we can see with the technology we have – from stars and planets to quasars and baryonic clouds, baryons being a type of subatomic particle that makes up normal matter. So, there is a lot more dark matter than normal matter.
The problem is, we can’t see it.
Dark matter, unlike normal matter, does not interact with its environment in any of the ways that are familiar to us. Scientists use light to detect normal matter, but dark matter does not absorb, reflect, or emit light, which makes it practically invisible to us.
But how do we know that dark matter is even there, then? We know because we can see the effect it is having on normal matter, and this effect is gravitational.
Galaxies in the universe have a certain behavior, and scientists have observed enough of this behavior to conclude that it cannot be entirely explained by the laws of physics, on which we have built our understanding of the universe. For starters, galaxies are spinning faster and faster, and the universe is expanding at a faster rate than it used to. Yet, if only the known rules of physics applied, these fast-spinning galaxies should fly away from each other. The conclusion is that there is a lot more mass in the universe than the objects that are visible to us: dark matter.
MACHOs Vs WIMPs
There have been many hypotheses about what this matter is made of, and to date, two seem to be dominant, one more than the other. The first hypothesis says dark matter is made of massive compact halo objects, or MACHOs, which, interestingly enough, are made up of normal matter.
They may include neutron stars, black holes, and brown dwarfs. The first two—neutron stars and black holes—are objects of immense mass, which makes them suitable candidates for dark matter, and they can also remain hidden from view if they are isolated. Brown dwarves, on the other hand, have been observed to interact gravitationally with objects made from normal matter, and that’s their only claim to dark-matter fame, yet to be substantiated.
The much more popular hypothesis involves WIMPs, or Weakly Interacting Massive Particles. These are not massive because of their size but because of, well, their mass. They are weakly interacting because dark matter does not interact with other matter. WIMPs include neutrinos, axions, and neutralinos – all types of subatomic particles.
The Perfect Fuel Dream
Yet while the subject of subatomic particles is certainly a fascinating one, the ultimate question for non-physicists is “Why should we care about dark matter?” The answer to this question, as given in a Forbes article by Ethan Siegel, is “Because we can turn it into the perfect fuel and conquer space.”
The problem with current rocket fuel is that it is terribly inefficient. Siegel puts its efficiency at 0.0001 percent and that’s the maximum we can achieve with present fuel technology. Dark matter, on the other hand, if the WIMPs hypothesis is true, could have 100-percent efficiency as a fuel. Related: A Bull’s Guide To Oil Markets
The explanation of how this could happen is lengthy and confusing for most non-physicists, involving terms like half-integer and integer spins, and bosons and fermions. Fermions are matter-making particles. Bosons are energy-making particles. Suffice to say that the particles scientists believe make up dark matter while not interacting with other component parts of the universe, can interact among themselves.
If, as the hypothesis goes, they are bosonic particles - so-called force carriers that glue other matter together - they might be able to be their own antiparticle. This, in turn, might make them able to conduct matter-antimatter annihilation between themselves, releasing huge amounts of energy in the process.
What is matter-antimatter annihilation? The representation of the most famous physics formula: E = mc2, turning mass into energy. It is 100-percent energy efficient, as Siegel notes, but it is problematic: the process needs antimatter and producing even a tiny amount of that requires enormous amounts of input energy and effort.
As Siegel puts it, “If you can collect two dark matter particles and make them interact with one another, there's a finite probability that they'll annihilate. When an annihilation occurs, they'll produce pure energy in a 100% efficient fashion: via Einstein's E = mc2. In other words, if we understand dark matter correctly, there's a free, unlimited source of energy everywhere humanity dreams of going.”
The problem here is spotting dark matter to begin with and work is being done on developing technology that is sensitive enough to do just that. The first experiment so far, the Large Underground Xenon, or LUX, began in 2012 and ended in 2016 without finding anything. Related: Aramco’s Breakeven Costs Are The Lowest In The World
Apparently, the physics community considered this nothingness a huge success and went on to develop a new version of the LUX particle detector called LUX-ZEPLIN. The LUX-ZEPLIN was lowered 1.5 km underground last month and will begin its detecting work in July next year. Why underground? To prevent false positive detection results from space radiation.
The LUX works by utilizing photosensors submerged in liquid xenon - a chemical element used in photography and flashlights. Researchers believe that when a WIMP meets a xenon atom, the collision will release photons, producing a spark of light that the photosensors will detect, essentially proving the existence of dark matter.
We are not there yet, but we are working on it. After all, besides revealing the secrets of the universe to us, dark matter could help us become true space travelers unrestricted by fuel needs.
By Irina Slav for Oilprice.com
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Irina is a writer for Oilprice.com with over a decade of experience writing on the oil and gas industry. More