Written by: Jenn Xu
Image from wallpaperscraft.com
Every time when you wake up, you experience the world as we know it all around you. There are things you could see and feel, and besides the everyday things we encounter that we consider our normal, there’s always more to discover on our vast planet. All of this stuff is what we call “matter”—it’s what makes up the world. But what about the stuff beyond our world?
We live in this Unknown that we call the universe: the universe is everything. The universe itself is made up of more than just matter, and it’s split into 3 major categories. There’s the ordinary matter that we interact with everyday, making up around 5% of the universe. We define matter as anything that takes up space and has mass, and the building blocks for matter are atoms. Rocks are matter, skyscrapers are matter, and we are made up of this matter.
There’s also something called antimatter. Antimatter is the exact opposite of ordinary matter; however, its subatomic particles’ charges are reversed, and so are its properties. This component is very scarce throughout the universe and makes up very little of it. Antimatter is predicted to be composed of antiparticles. It is theorized that every particle that exists under the umbrella of matter has an antiparticle that exists under the umbrella of antimatter. For example, for positively charged protons, there exists an antiproton that is negatively charged, but the two have the same mass. When a particle collides with its antiparticle, the two destroy each other and vanish, emitting light in the process. The theory of antimatter was first developed by one Paul Dirac, a British physicist, who sought to merge two physics concepts: relativity and quantum mechanics. As a result, the idea of antimatter was conceived in the process.
An interesting theory in the works regarding antimatter is that the universe we reside in is not the only one out there, and that there exists a mirror universe made up of antimatter. It would be the same as ours, except everything was the opposite. In this theory, the antimatter universe runs backwards in time from Big Bang, while ours runs forwards.
Next, we have dark matter. This is a term that you may or may not have heard of before, but dark matter actually constitutes around 27% of our universe. That’s more than a quarter of the universe of stuff that we don’t know much about! Dark matter is a concept that even the top researchers in the world cannot fully explain yet. However, there are a few things we do know of. Dark matter isn’t made up of atoms, unlike ordinary matter. Moreover, the “dark” part tells us that it’s invisible. We can’t see dark matter, nor can we detect it using any kind of radiation on the electromagnetic spectrum. Despite this, the concentrations of dark matter throughout the universe can be mapped by studying its gravitational pull on the surrounding ordinary matter.
Evidence supporting the concept of dark matter has now mostly been credited to a female astronomer named Vera Rubin back in the 1970s. Following the theory of dark matter proposed by Fritz Zwicky in the 1930s, Rubin calculated that the center of galaxies rotated at the same speed as its edges, going against the concept of peculiar velocity. This is the concept of the relative velocity of an object to its rest frame. Rubin’s calculations can be visualized using a CD. Relative to the edges of the disk, the center of it spins faster; but not in the case of her calculations. It actually spins at the same speed, which was not expected. Rubin’s discovery indicated that galaxies were a part of an even larger structure—one that was made of dark matter.
What makes up the last 68% of the universe? Dark energy. Different from dark matter, dark energy is what is expanding the universe as we speak. The volume of dark energy is calculable because we know its effects on the universe’s expansion, but other than that, it remains mostly a mystery.
The idea of dark energy first came into existence through the mind of Albert Einstein. He proposed that empty space had its own type of energy, and that more space can come into existence (hence the expansion of the universe). Since this space-energy is a property of empty space, the more space that comes into existence, the more space-energy there is. In other words, this energy doesn’t get spread thin and distributed evenly as more space appears, but there simply is more of it. Although there is much to learn about all this dark stuff surrounding us, we’re starting to uncover the tip of the iceberg on this topic.
There will always be new things to look into, and perhaps we’ll simply never get to fully understanding this universe of ours. But regardless, knowing what we know now about what makes up this Unknown that our planet calls home, we may be one step closer to figuring it all out.
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