Let's imagine the composition of the universe
as a pie-chart.
How much of the universe do you think is made up of the elements in the periodic table?
100%? The truth is five.
Only 5%, is what we called, Normal Matter.
But, what about the rest?
Well it will be a very long story
to talk about the entire universe,
so we'll just talk about another 27% today
Dark Matter.
So what is dark matter? 
Are you talking about dark magic like in Harry Potter?
Well, no.
Dark matter really exists in the universe.
It is a massive substance, that
doesn't interact with light, or normal Matter.
This means they can travel through us,
but we cannot see it.
So, how do we know it exists?
Scientists discovered dark matter
when they're studying the rotation of galaxies.
Newton's Law of Gravity concludes
the farther a star is from the center,
the slower it moves.
This makes sense to us because
that's how our solar system works.
However, in 1960s, astronomer Vera Rubin
observed a galaxy and found that
the distance doesn't affect velocity.
But, wait a minute... Is Newton wrong?
Imagine swinging a ball,
if you swing too fast, the string will break,
and the ball will fly away.
If stars travel too fast,
the galaxy would be ripped apart.
So, there must be some force,
keeping the galaxy the way it is.
Rubin concluded, that there must be something invisible
5 to 6 times more than was visible in the galaxy
that provides extra force
to hold the entire galaxy together.
This invisible matter, was later named, 
Dark Matter.
Okay Dark Matter actually exists,
can it be detected?
Well, the answer is Not Yet.
Scientists have been trying to find Dark Matter in mainly three ways:
collision of dark matter particles;
collisions of normal matter particles;
and collision between both.
First when dark matter particles collide,
detectable particles like Neutrinos
and Gamma-ray Photons will be released.
Secondly, since dark matter is created after the Big Bang
just like any other matter,
CERN laboratory in Switzerland try to make
dark matter themselves with a particle collider.
Astronomers also found that
there's a tiny interaction between
dark matter and Xenon nuclei.
So scientists also build a detector for that.
However, after so many experiments,
scientists still don't know what dark matter exactly is.
They already ruled out candidates including
Black Holes, Dust or Dead Stars.
Now, they're testing on two hypothetical particles:
Neutralinos and Axions.
Neutralino weighs 100 to 300 times more than a proton.
It originated from supersymmetry theory 
which states that each particle we discovered,
has a partner, that has an opposite spin.
Neutralino, is one of the super partners that is stable.
So it became one of the candidates.
On the other hand, Axion weighs
one millionth of millionth of an electron.
It is a hypothetical particle proposed by the scientists,
that has mass, and doesn't interact with light
or normal matter.
Remember dark matter has the exactly same properties!
That is why Axion became the other candidate.
So why is dark matter important?
Well, remember the three experiments I talked about earlier?
All of them found signals of Anomalies, something that's not from ordinary physics.
Understanding dark matter, means
opening a new door to some
unprecedented physics concepts.
And this mystery, awaits for our generation,
to uncover.
Thank you for watching!
