This is how we really know that dark matter and dark energy really exist in the universe.

What is matter? Easy one. Anything that has mass and occupies space. Good. You are a pile of matter constantly shifting shape — but you’re not a shape-shifter, okay! However, matter is easy to define, but scientists claim this stuff that’s all around us is just five percent of the entire universe. The remaining 95 percent? Some elusive substance they’ve theoretically dubbed dark matter, which make up 25 percent of the universe. While invisible or whatever, it does seem to have mass, and occupies space, and thus has gravity. That’s the only evidence scientists have about the existence of dark matter. But is that the real case?

Related media: Dark Matter and Dark Energy Explained!

 

I Only Exist In The Dark

This whole idea of dark matter started back in the late 1960s when Vera Rubin and Kent Ford discovered that galaxies appear to behave differently than they should. This made scientists to search for answers why, which led to the theoretical discovery of dark matter. The elusive invincible substance that’s lurking throughout the universe, undetectable by telescopes but shows effects of gravity on galaxies.

Of course, that’s all theoretical, but duh, what better way can you describe space which literally looks dark. Its believed that scientists just made it up to crunch the numbers and it seems to make the math convincing. If you recount from classic physics, the more mass an object has, the stronger it is. This means a planet with more mass has a stronger gravitational influence.

Here’s the catch: If galaxies were only made up of normal matter — the stuff that makes up you — there wouldn’t be enough gravity to hold them together. The stars in the sparse outer flanks wouldn’t orbit just as fast as the ones near the bulge. Aforementioned, scientists claim that normal matter only makes up less than five percent of the universe, dark matter holds 25 percent, and the rest is yet again another elusive mysterious force theoretically known as (you guessed it) dark energy. So what is all this about?

“People ask this question a lot,” says Katie Mack, a theoretical astrophysicist at North Carolina State University who studies dark matter. “You know, maybe dark matter is just a fudge factor or something.”

 

I See You When You Get Dark

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Image: NASA / ESA

In Einstein’s theory of general relativity, matter warps both space and time in the same way as a bowling ball sitting on top of a trampoline curves the fabric. As light travels towards the curve, it curves along the bend around the massive object in its path. This warp in space and time seems like a cosmic magnifying glass phenomenon, also known as gravitational lensing.

However, the effects of gravitational lensing produced by a galaxy or galaxy cluster is too great to be simply explained by normal matter. That’s another compelling evidence that dark matter exist. There are even signs of it in the cosmic microwave background — the radiation left over after the Big Bang, which point to the existence of dark matter.

“We see patterns in that that show there had to have been something at early times that brought matter together in a way that can’t work with just regular matter,” Mack said in a interview.

 

What Is Dark Matter?

“I’m not sure what it is that makes it more appealing to break general relativity and say that all these huge observations are wrong, versus there’s a particle we can’t see.” Mack says.

She explained the phenomenon better with this wind blowing analogy:

“It’s kind of like if you were walking down the street and you see a plastic bag sort of move across the street in front of you, and then you see some trees lean over, and then you hear this kind of rustling sound, and then you feel a little bit of cold coming from one direction, and then you see a street sign swing, and you’re like ‘That’s wind!’ You can’t see the wind, but there are all of these different pieces of evidence that air is moving.”

“It’s kind of the same with dark matter. We can’t see it directly, but there are so many pieces of evidence that it just makes more sense than any other explanation that we can come up with.”

 

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Written by: Nana Kwadwo, Sun, May 26, 2019.

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