People often talk
about the microcosm
and the macrocosm.
The microcosm is a world of elementary particles,
the scales are very small,
and it is impossible to visualize them.
The other extreme is the macrocosm.
This cluster of galaxies,
the universe - a completely different language,
different scales.
When we talk about the world of elementary particles,
we put an experiment
when we talk about the world of galaxies,
we make observations.
Over the Galaxy,
over the universe,
the experiment is difficult to put.
Nevertheless,
the information is approximately similar,
we get data
that you need to somehow comprehend.
Now we will tell you
a few facts about dark matter.
Observations:
In the field of astrophysical observations,
it was observed
that the world probably consists not only of what we see,
but we see stars,
nebulae,
intergalactic gas
in general, astronomical objects.
By rotating stars around the center of the Galaxy,
you can determine
what the mass of the Galaxy is.
So, the mass is greater
than what we see as a glowing galaxy.
For example,
the Milky Way:
he has a certain number of stars,
which can be calculated
from astronomical observations.
It is approximately known
what their mass is.
And you can see
how the Sun rotates around the center of the Galaxy:
approximately at a speed of 220 km / s.
If one starts from visible stars,
then it should rotate more slowly.
Theories:
Two assumptions were made:
either the laws of gravity are wrong;
Or there is some hidden
invisible mass.
The most popular point of view
is the theory of a hidden mass,
one that we do not see,
because it does not emit light.
That matter that does not emit light
was called dark matter.
On the other hand,
there is not just astrophysics,
but also general cosmological views of the universe:
the curvature of space,
the speed of expansion,
and so on.
In recent years,
great progress
has been made in measuring the temperature fluctuations
of microwave cosmic radiation
that permeates the entire Universe
and is a relic of the Big Bang.
From these cosmological observations it follows that,
firstly, the curvature of space is zero,
and secondly, that visible matter
stars, intergalactic gas
is only 4% of the total energy balance of the universe
24% is dark matter.
And more than 70 percent
of what is codenamed "dark energy."
Why share dark energy and dark matter?
The matter is that supposedly dark matter
is ordinary matter with the usual equations of state:
the pressure is proportional to the density
and so on.
But what is called dark energy,
and what is responsible for the expansion of the universe,
is a substance that does not obey the usual laws for particles,
for it the pressure is proportional to the density with the minus sign.
This does not happen in the case of ordinary matter.
Cosmological constant:
In the process of creating the general theory of relativity,
Einstein first wanted to build a static model.
Later, when it became known that the universe was expanding,
the cosmological constant was abandoned
and it was assumed that it was zero.
And now the views are changing again.
This cosmological constant
perhaps,
is dark matter.
The mystery for physicists
is its origin and why it is so small.
Although 73% seem to be a very large fraction in the entire energy of the universe,
but if we recalculate the cosmological constant
into units we operate with in particle physics,
then this is a fantastically small quantity.
One could expect that the cosmological constant
has a scale of the order of the masses
of elementary particles,
but it is several orders of magnitude smaller.
There is no explanation for this fact so far.
What does dark matter consist of?
It is still unknown what the dark matter consists of.
If we take the usual particles
of the standard model and say:
"But can not it consist of the same particles?"
- the answer is negative.
Therefore, we have to invent some new particles.
There are quite a few options,
but none of them has been experimentally confirmed.
One of these options,
which is now very popular,
is the assumption that in the world there is supersymmetry,
it predicts new particles
and, in particular,
a particle that is a "partner" of a photon.
A photon is a quantum of an electromagnetic field, light.
His "partner" (this particle is called fotino)
is a candidate for the role of a particle of dark matter.
It is a neutral particle,
it does not have an electric charge,
it is heavy - one hundred tons of a proton,
maybe more
- and it participates in a weak interaction.
In astrophysics there is such a term: WIMP.
It is a weakly interacting massive particle.
For example, fotino is WIMP.
And these WIMPs presumably
form the basis of dark matter.
They form a halo
that is, the halo of our galaxy.
The halo is about five times larger
than the visible size of the Galaxy,
and on it these particles are running
at a speed of about 300 kilometers per second.
We try to find them experimentally.
There are special underground installations in order for these WIMPs to "catch",
but so far the result is negative.
If it is caught by interacting with ordinary matter,
then, probably,
the next step will be an attempt to get it at the colliders.
We are trying to identify
what is born at the colliders,
with what we catch from space
in the form of particles of this dark matter.
And if these two ways converge,
then we will understand the nature of dark matter.
We hope that you liked the video,
so put "like",
write comments
and subscribe to the channel!
We have a group in the social network
the link will be in the description.
