80 percent of our universe is made up stuff
that doesn’t emit light or energy, and cant
be directly observed.
This is called dark matter.
Many scientists believe its there, because
there are, how to put this, hints that it
exists.
So what is dark matter?
That’s exactly what we are going to talk
about, right now on life’s biggest questions.
Hello and welcome back to LBQ, I’m charlotte
dobre.
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us know in the comments below what topics
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The visible universe includes planets, stars,
moons and galaxies.
But it makes up roughly 5 percent of the total
mass of the universe.
The other 95 percent…is stuff we cant see.
Around 75 percent is made up of a force that
repels gravity, its called dark energy.
And the remaining 25 percent is what scientists
call dark matter.
Though much of the scientific community agrees
it exists, scientists have not observed Dark
Matter directly.
Well… not exactly, but I’ll get to that
later.
Understandably, Its pretty difficult to observe
something that doesn’t interact with light,
or baryonic matter, or radiation.
So how do scientists know dark matter is there
if we haven’t been able to detect it?
One word.
Gravity.
Dark Matter has gravity.
Gravity that has an effect on galaxies and
clusters of galaxies.
I’ll give you an example.
According to our current understanding of
physics, the stars on the edge of a spinning
spiral galaxy should be travelling much slower
than those that are at the center of the galaxy.
But strangely, the stars at the edge of a
spinning galaxy orbit at almost the same speed
as the stars near the galactic center.
This leads scientists to believe that the
stars are being affected by some sort of other
gravitational pull that exists in a halo around
the galaxy.
The pull is believed to be created by dark
matter.
Furthermore, even though dark matter doesn’t
emit light…it does do some pretty weird
things to light.
Astronomers have observed certain optical
illusions in space.
Sometimes light from a galaxy is distorted
by some sort of invisible substance.
This phenomenon is known as gravitational
lensing.
So if there is an invisible substance that’s
affecting how we see distant galaxies, and
its gravity is also affecting the speed at
which stars orbit around galaxies…what the
heck is it?
Some scientists believe that dark matter is
made up of some sort of particle that we don’t
yet have an understanding of.
These particles do not interact with light
or matter, but they still have a gravitational
pull.
In order to find out what dark matter is,
scientists have to look back in time.
And they can look back in time because it
takes time for light to reach us.
Recently, while a team of astronomers at Arizona
State university were looking for the earliest
stars in our universe using radio signals,
they stumbled upon signals made by low mass
particles that dated to 180 million years
after the big bang.
The astronomers observed a change in the radio
signal coming from ancient hydrogen, which
signified an absorption of ancient light.
Much to their surprise, the radio signals
did not behave as expected.
The hydrogen gas was colder than expected,
which means that something must have cooled
it down.
And that something is, you guessed it, dark
matter.
These signals are the first direct proof that
dark matter exists.
According to Professor Barkana who lead the
study, dark matter is the key to unlickign
the mystery of what the universe is made of.
Yet it remains one of the biggest mysteries
in physics.
This study would suggest that dark matter
might actually interact with regular matter,
and would change our current understanding
of dark matter.
But of course other scientists must be able
to reproduce this new evidence.
In order to do so, measurements need to be
recorded by other independent groups, which
shouldn’t take too long.
Professor barkana claims that dark matter
could be detected with a large array of radio
antennas.
The biggest radio telescope in the world,
SKA, is currently under construction.
The study was published in the scientific
journal Nature.
And its not just dark matter scientists are
confused, and compelled by.
Back in the 1990’s scientists were completely
blown away by the discovery of dark energy.
Before its discovery, physicists hypothesized
that gravity slows down the expansion of the
universe.
But that is actually not the case.
2 independent teams measured the rate that
the universe was expanding and they both discovered
that the expansion of the universe is not
slowing down, its actually speeding up.
Space time is actually being stretched apart.
But perhaps the question, what is dark energy
is a topic for another episode of lifes biggest
questions.
For now, I’m charlotte dobre, and thank
you for watching.
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