jeudi 28 novembre 2019

What is dark matter and dark energy?

What is dark matter and dark energy?

Matter, as we know it: atoms, stars, galaxies, planets and trees stones and we This subject accounts for less than 5% of the known universe About 25% is dark matter and 70% dark energy both are invisible.

It's quite strange because it suggests that all we know is really a very small part of reality.
But that's not the worst: We have no idea what matter and dark energy are or how they work. But we are almost sure of their existence.

dark energy

So what do we really know?
Dark matter is that thing that makes the existence of galaxies possible. When we calculate why the universe is structured as it is, It quickly becomes clear that there is not enough normal matter. The gravity of the visible material is not strong enough to form
galaxies and complex structures. The stars are more likely to scatter everywhere but not to form galaxies.

We know that there is something inside and around them. Something that neither emits nor reflects light. Something black . But failing to be able to calculate the existence of dark matter,

we can see it ... in a way.
Places with high concentration of dark matter bend light nearby.So we know that there is something that interacts with gravity. For now, we have more ideas about what dark energy is not just what it really is. We know that dark matter is not just clouds of matter without stars,because that would emit particles that we could detect.Dark matter is not antimatter,
because antimatter produces unique gamma rays when it reacts to normal matter.Dark matter is not made of black holes either,very compact objects that violently affect their surroundings,while dark matter seems scattered everywhere.

In fact, we are sure to know three things:

1. Something is there, outside.
2. It interacts with gravity.
3. There are many.

Dark matter is probably made of complicated exotic particles that do not interact with light and matter in a way that you would expect, but for now, we just do not know. Dark energy is even stranger and mysterious.We can not detect, measure or taste it.
But we see these effects very clearly.

in 1929, Edward Hubble examined how the wavelength of light emitted by distant galaxies, shifts to the red side of the electromagnetic spectrum during his journey in space. He discovered that the weakest and distant galaxies had a larger redshift; galaxies closer, not so much.

Hubble has established that this was due to the very expansion of the universe.
The red shift is explained because the wavelengths of light stretched at the same time as the universe.

Recent discoveries have shown that this expansion of the universe is accelerating.
Before that, it was taught that the gravitational attraction would be caused by either
to slow down or even retract it to the point of collapsing on itself. Space does not change its properties as it expands; there are just more. Extra space is constantly being created everywhere galaxies are compact clusters of things held together by gravity so we do not realize it in our everyday life. But we see it everywhere around us. Wherever there is empty space in the universe, more is formed at each moment. So dark energy seems to be a kind of intrinsic energy to emptiness.

This energy is stronger than anything we know and believe over time. Void has more energy than all the rest of the combined universe. We have several ideas about the nature of dark energy. One of these ideas is that dark energy is not palpable but just a property of space.
The emptiness is not nothing but has its own energy. It can generate more emptiness and is rather active.

So as the universe expands, more and more space may be available appears to fill the gaps, this leading to faster expansion. This idea is close to an idea put forward by Einstein in 1917, of the concept of a cosmological constant, a force contrary to gravity. 

The only problem is that when we tried to calculate the value of this energy the results have been so bad and unexpected that it only increases the confusion. Another idea is that the void would actually be filled with temporal, virtual particles that spontaneously and continually appear from nothing and disappear again. The energy of these particles could be dark energy. Or maybe black energy is a kind of fluid or field dy.

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