Dark Matter Simplified – Explaining the Unknown Universe
First of all, let’s make one thing clear: nobody knows what dark matter actually is. As you will learn below, dark matter can not be directly seen visually. However, we do have some information by observing dark matter’s affect on its surroundings. So, let’s jump right in!
Words You Outta Know:
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Baryonic matter: The matter that makes up EVERYTHING we know and see. Stars, planets, food, animals and even people. Literally, anything existing in your human life is considered baryonic matter.
Gravity: The natural force in which all matter attracts other matter. And, the larger the object, the more matter it has, and the more it attracts other matter.
Mass: The amount of matter something has. Actually, mass is not the same as weight like most people think. Instead, weight is a result of gravity. For instance, if you took a 1-pound object to the Moon, its mass (matter it’s made of) would stay the same, but it would only weigh 1/6 of a pound because of the Moon’s lower gravity.
Dark Matter Simplified: What is dark matter?
First of all, nobody currently knows what dark matter is. Also, since it is currently invisible to our eyes and tools, we do not yet know how to study dark matter. However, by studying the things that we can see, we do know that dark matter is real and does exist.
Dark Matter Simplified: How is dark matter detected?
When we look out into space, we see stars, planets, galaxies and more. And, all of these objects are made of matter. Plus, the matter making up all of these objects causes them to attract other matter through gravity.
Astronomers can very accurately measure and predict the results of gravity. For instance, we know where and how a planet will orbit. Or, we know how one star will attract another star.
Furthermore, astronomers can observe the orbits of stars in a galaxy and use this information to very accurately measure the amount of matter (mass) in the galaxy. The speed of stars’ orbits is a direct affect of the gravity from other matter in the galaxy!
Now, the problem is that when astronomers use any galaxy’s stars to precisely add up its total mass, something is missing! Stars are moving much faster than they should be compared the matter measured. Basically, by observing the behavior of visible matter, we know some form of invisible matter must be present.
Astronomers have named this missing material “dark matter.”
Dark Matter Simplified: How much dark matter is out there?
Baryonic matter (definition above) is everything we have ever seen and known in the universe. All stars, planets, galaxies, people, plants, pets and everything else are baryonic matter.
Yet, through detailed measurements, astronomers have concluded that all baryonic matter accounts for 4.6% of the universe. Wait, let’s think about that. Literally, everything ever seen or sensed throughout the existence of life only makes up 4% of the universe!
So, what makes up the remaining 95%? Well, nearly 73% is thought to be dark energy, which is fully explained in its own separate article. But, around 23% is dark matter. In other words, the dark sky you see at night is far from empty space!
Dark Matter Simplified: What is dark matter made of?
Given that we have yet to see or directly observe dark matter, nobody knows what it’s made of. However, multiple theories now swirl around as we scramble to unlock science’s biggest mystery. Currently, a few of the leading theories are:
Weakly Interacting Massive Particles, or WIMPs for short, describe an overall type of particle. Presumably, WIMPs are much more massive than common particles, like protons. Yet, these heavier particles would only interact with each other through mild weak forces, making them tough to detect! As of now, WIMPs are, by far, the leading candidate for dark matter.
Neutrinos are tiny, almost massless particles. And, one neutrino could pass through our entire solar system and never bump into a single piece of matter!
However, scientist believe there is a neutrino counterpart, called a sterile neutrino. And, it’s even more elusive! In fact, a sterile neutrino could travel for the entire age of our universe (14 billion years) without bumping into any other matter! That would be like you walking blindfolded through New York City for an entire year without running into a single thing!
Though, it sounds like a quaint Italian restaurant, the neutralino is actually a of particle. Some theories believe each known particle has a “super” counterpart particle. The neutralino is one of these! Sadly, this theory is far too complicated to explore in-depth in this article. M.I.T. provides deeper details on this theory.
A long-standing sci-fi staple is the alternate universe. Now, once again, they emerge in predictions about dark matter. Some theories believe matter in entirely separate universes is the cause of dark matter. This other-worldly matter is unable to interact with our universe’s matter, yet still throws off measurements and calculations in our own world. Sure, it’s bazaar. But, can you prove it wrong?
Now, another sci-fi standby appears as probably cause for dark matter, the fourth dimension! This theory believes that if dark matter does not exist in a separate universe, it may exist in an unseen dimension of space. Unfortunately, this theory’s wild nature leaves it currently not well-accepted.