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your daily expresse till the edge of the space
and today we will talk about what is a dark
matter?
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Galaxies in our universe seem to be achieving
an impossible feat.
They are rotating with such speed that the
gravity generated by their observable matter
could not possibly hold them together; they
should have torn themselves apart long ago.
The same is true of galaxies in clusters,
which leads scientists to believe that something
we cannot see is at work.
They think something we have yet to detect
directly is giving these galaxies extra mass,
generating the extra gravity they need to
stay intact.
This strange and unknown matter was called
“dark matter” since it is not visible.
By fitting a theoretical model of the composition
of the universe to the combined set of cosmological
observations, scientists have come up with
the composition that The universe contains.
68% dark energy, 27% dark matter, 5% normal
matter.
we talk about dark energy in our last video,
you can check link down below.
First, we have to answer question
What's the difference between dark energy
and dark matter.
Although the names seem to imply that they
are similar, dark energy and dark matter are
not directly related.
Dark energy is the force responsible for the
acceleration of the expansion of the universe
at an ever-increasing rate since the Big Bang.
Dark matter, on the other hand, consists of
the unseen particles that bind our universe—and
even our own bodies—together.
Although astronomers can't see dark matter
through a telescope, they can locate dark
matter by its gravitational effects on its
surroundings and the detectable X-rays, it
emits, as explained by Craig Freudenrich.
Where dark matter is the force that keep the
universe together and explains how the cohesion
of the stars, galaxies and more is even possible,
dark energy pushes it apart.
Let's go back to our basic question.
What is Dark Matter.
Unlike normal matter, dark matter does not
interact with the electromagnetic force.
This means it does not absorb, reflect or
emit light, making it extremely hard to spot.
In fact, researchers have been able to infer
the existence of dark matter only from the
gravitational effect it seems to have on visible
matter.
Dark matter seems to outweigh visible matter
roughly six to one, making up about 27% of
the universe.
Here's a sobering fact: The matter we know
and that makes up all stars and galaxies only
accounts for 5% of the content of the universe!
But what is dark matter?
One idea is that it could contain "supersymmetric
particles" – hypothesized particles that
are partners to those already known in the
Standard Model.
Experiments at the Large Hadron Collider (LHC)
may provide more direct clues about dark matter.
Many theories say the dark matter particles
would be light enough to be produced at the
LHC.
If they were created at the LHC, they would
escape through the detectors unnoticed.
However, they would carry away energy and
momentum, so physicists could infer their
existence from the amount of energy and momentum
“missing” after a collision.
Dark matter candidates arise frequently in
theories that suggest physics beyond the Standard
Model, such as supersymmetry and extra dimensions.
One theory suggests the existence of a “Hidden
Valley”, a parallel world made of dark matter
having very little in common with matter we
know.
If one of these theories proved to be true,
it could help scientists gain a better understanding
of the composition, of our universe and in
particular, how galaxies hold together.
Studies of other galaxies in the 1950s first
indicated that the universe contained more
matter than seen by the naked eye.
Support for dark matter has grown, and although
no solid direct evidence of dark matter has
been detected, there have been strong possibilities
in recent years.
"Motions of the stars tell you how much matter
there is," Pieter van Dokkum, a researcher
at Yale University, said in a statement.
"They don't care what form the matter is,
they just tell you that it's there."
Van Dokkum led a team that identified the
galaxy Dragonfly 44, which is composed almost
entirely of dark matter.
The familiar material of the universe, known
as baryonic matter, is composed of protons,
neutrons and electrons.
Dark matter may be made of baryonic or non-baryonic
matter.
To hold the elements of the universe together,
dark matter must make up approximately 80
percent of its matter.
The missing matter could simply be more challenging
to detect, made up of regular, baryonic matter.
Potential candidates include dim brown dwarfs,
white dwarfs and neutrino stars.
Supermassive black holes could also be part
of the difference.
But these hard-to-spot objects would have
to play a more dominant role than scientists
have observed to make up the missing mass,
while other elements suggest that dark matter
is more exotic.
Most scientists think that dark matter is
composed of non-baryonic matter.
The lead candidate, WIMPS (weakly interacting
massive particles), have ten to a hundred
times the mass of a proton, but their weak
interactions with "normal" matter make them
difficult to detect.
Neutralinos, massive hypothetical particles
heavier and slower than neutrinos, are the
foremost candidate, though they have yet to
be spotted.
Sterile neutrinos are another candidate.
Neutrinos are particles that don't make up
regular matter.
A river of neutrinos streams from the sun,
but because they rarely interact with normal
matter, they pass through the Earth and its
inhabitants.
There are three known types of neutrinos;
a fourth, the sterile neutrino, is proposed
as a dark matter candidate.
The sterile neutrino would only interact with
regular matter through gravity.
"One of the outstanding questions is whether
there is a pattern to the fractions that go
into each neutrino species," Tyce DeYoung,
an associate professor of physics and astronomy
at Michigan State University and a collaborator
on the IceCube experiment, said.
The smaller neutral axion and the uncharched
photinos are also potential placeholders for
dark matter.
According to a statement by the Gran Sasso
National Laboratory in Itally (LNGS), "Several
astronomical measurements have corroborated
the existence of dark matter, leading to a
world-wide effort to observe directly dark
matter particle interactions with ordinary
matter in extremely sensitive detectors, which
would confirm its existence and shed light
on its properties.
However, these interactions are so feeble
that they have escaped direct detection up
to this point, forcing scientists to build
detectors that are more and more sensitive."
A third possibility exists — that the laws
of gravity that have thus far successfully
described the motion of objects within the
solar system require revision.
Maybe in future.
we will come out with the better theories
of gravity.
Don't forget to comment, your what do you
think, which of this hypothesis are more close
to reality.
For a theorist, an observer or an experimentalist,
dark matter is a promising target for research.
We know it exists, but we do not yet know
what it is at a fundamental level.
The reason we do not know might be obvious
by now: it is just not interacting enough
to tell us, at least so far.
As humans, we can only do so much if ordinary
matter is essentially oblivious to anything
but dark matter's very existence.
But if dark matter has some more interesting
properties, researchers are poised to find
them.
There are lots of questions left so don't
space out and live some space in your brain
for answers.
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