Dark Matter

Why is our universe so empty?

95% of the universe is missing, or rather, invisible.
When scientists try to calculate how much mass in in our galaxy (and other galaxies), they do so by adding up the weight of the stars, planetary bodies and everything else. But there's a problem: If galaxies are in constant rotation, why doesn't everything inside it fly away in different directions? It's similar to a merry-go-round that spins so fast the children playing on it are flying off.
Scientists have deduced that there is a non-visible force or matter that provides the extra gravity necessary to hold our galaxy together, which we call Dark Matter.

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What Dark Matter IS

Dark matter is a type of matter that possesses mass, but doesn't reflect light (hence, it is invisible).
It makes up 27% of the universe. Scientists themselves don't know what dark matter is made up of (so it's impossible for a science student like me to explain it to you fully), but the two major theories of what dark matter could be include:

• Weakly Interacting Massive Particles, or WIMPs for short: These are subatomic particles that pass through you, the Earth and everything else in the galaxy. They have mass (hence they also have gravity) but they don't reflect light (hence they are invisible).
• Axions: These are super-light particles whose existence was predicted way back in the 1970s. However, their existence is still hypothetical; scientists are yet to successfully catch them for study.

What Dark Matter ISN'T

As a firm believer in science (and a strong hater of rumours), I have also come to clear any rumours about what dark matter could be, even when it is NOT. Dark matter is not anyone of the following:

• A Black Hole: Black holes possess enough gravity to pull light into them; dark matter lets light pass through them.
• Dark Energy: Dark matter holds the universe together, whereas dark energy pushes galaxies apart. They are complete opposites. (More on Dark matter in my next post.)
• Antimatter: When antimatter touches regular matter, it explodes! Dark matter doesn't react with regular matter at all.

Evidence of Dark Matter

As a science student (and potential scientist), I would not have posted about dark matter if I did not have evidence about its existence. Some of the major proofs of the existence of dark matter include:

• It is extremely heavy: All the things we see in our entire universe, all the stars, planets and endless galaxies barely make up 5% of the universe in weight. A whopping 27% goes to dark matter, while the remaining 68% of the universe's weight is made up of dark energy.
• Gravitational Lensing: Dark matter has gravity, and as such it bends the path of light coming from distant stars (when I say distant, I mean a few light years away). When we look through telescopes, we see ghostly "arcs" of light. Similar to looking at the bottom of a glass cup of water, the water itself is clear, but the cup bends the light so that the outline is clear.

Want to hear me discuss about other mysterious parts of the universe, such as antimatter, black holes or dark matter? Make sure you give my post an upvote, I would really appreciate it.

References

NASA: https://science.nasa.gov
U.S. National Science Foundation: https://www.nsf.gov
AccessScience: https://www.accessscience.com