In the news last week was the announcement of the death of Stephen Hawking (8 January, 1942-14 March, 2018). A renowned Physicist who defiled all odds to distinguish himself in the world of physics. I am not writing about Hawking, I only took a detour to mention him and pay my respect for him, as his contributions to our current understanding of the universe is phenomenal. May his soul rest in peace. This article is about something fascinating. Let’s get right to it. Shall we?

THE UNIVERSE

The universe is composed of matter and energy. Matter includes stones, stars, galaxies, trees you just name it. Matter as we know it(as in all the examples you can think of), account for only about 5% of the entire universe. Strange right? What now account for the remaining 95%?
Today I will be discussing that.

About 25% of the universe is made up of dark matter while 70% is dark energy. Everything we see is just a little fraction of what is, that is, what we do not see is of greater magnitude than what we see.

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WHAT IS DARK MATTER?

Dark matter is made up of complex particles that may interact with matter and light in ways we do not know yet.
Without dark matter, the universe will not exist the way it is. As a matter of fact, the universe owes its structure to the existence of dark matter.
The gravity of normal matter is not sufficiently strong enough to form galaxies and complex structures. It is not sufficient to hold things in place. Everything will just be scattered all over the place. Stars will just be anywhere and there will be no galaxies.
There must be something around them that keeps the structure in place, something that we cannot see, something that will not reflect light, something dark!
We know for sure that the something is dark matter. How and what it is, is what we are yet to fully elucidate. We actually know what dark matter is not than what it is.

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WHAT DARK MATTER IS NOT

1. Dark matter is not just clouds of normal matter without stars, because it would have made particles which can be detected. And as we know, we still do not know how to detect or measure dark matter.
2. It is not anti-matter (opposite of matter) we know that when anti-matter comes in contact with matter, they annihilate each other producing unique gamma rays (energy).
3. It is not also made up of blackholes which are very complex and compact object, but dark matter is scattered all over the universe.
   Therefore, three things are for sure about dark matter:

1.They are out there
2.They interact with gravity (places with high concentration of dark matter bends light. This is evidence that dark matter interacts with gravity).
3.There are lots of it scattered all over the universe.

WHAT IS DARK ENERGY?

Dark energy is even more strange and complex than dark matter. Although it can’t be detected or even measured, but there are a lot of evidences pointing to its existence. Its effect is also very obvious.

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In 1929, Edwin Hubble investigated how the wavelength of light emitted by distant galaxies shift towards the red-end of the electromagnetic spectrum as it travels through space. He discovered that more distant galaxies show a large degree of red-shift than the closer ones. This he then concluded is as a result of the continuous expansion of the universe. Galaxies are still drifting apart. The red-shift occurs because the wavelength of light is stretched as the universe keeps expanding. Recent discoveries have also proved that the universe is expanding at an accelerating rate.
It was initially thought that gravity would have slowed it down, and eventually brings it to a halt for the reverse process to take place. This is not the case (At least not yet). Instead, the expansion is still accelerating. More spaces just keep appearing where it doesn’t seem to exist before, and its properties didn’t change whatsoever.
Galaxies are tightly bound clusters of matter held together by the force of gravity, so we do not observe or notice this expansion in our daily life. How weird will it be if I tell you that the space between you and the person sitting next to you is increasing by the passing of time and yet you cannot observe it? Wherever there is empty space in the universe, more of it is being formed every second.
Dark energy is a form of energy intrinsic (inherent) to empty space. It is stronger than any form of energy we know and it keeps getting stronger with time. This implies that empty space has more energy than everything else in the universe combined.

WHAT DARK ENERGY MAY BE

There are a lot of ideas on the plausible nature of dark energy:

Dark energy is not a thing, but a property of space. Empty space is not at all empty; it has an enormous amount of energy and can generate more space.
So, as the universe expands, more empty spaces are created which lead to a ripple effect. This in fact, might be responsible for the accelerating expansion of the universe.


Empty spaces might actually be full of temporary virtual particles which spontaneously and continually form from nothingness and disappear to nothingness. The energy of these particles could be dark energy.


It could also be that dark energy is a configuration of energy that permeates the universe, having the opposite effect on the universe than normal energy and matter.

CONCLUSION

We still do not know how to measure or detect dark energy and matter. Everything we know is still but theories. In fact, there are a lot of questions begging for answers than what we know right now. If there is anything to go by, it is that there are so much out there that we are still oblivious of.

References:
Dark energy,Dark matter
Dark matter and Dark energy