2 Jun 2019

What is dark matter and dark energy?

What is dark matter and dark energy?

Before 1998, one thing about expansion of universe was certain that the rate of expansion of universe is slowing down with the time, due to the gravitational force exerted by the universe. But, it depends on the energy density weather the universe will recollapse or remain expanding, whatever happens but the deceleration of universe is definite. Although the slowing down of universe was not been observed till the time, but it was theoretically fixed.

Then comes 1998, when Hubble Space Telescope observed very distant supernova, which showed that the universe is actually accelerating instead of slowing down, which was theoretically not possible. But, something was making it possible.

Maybe there should some kind of energy-fluid filling the space. Eventually, scientists still don’t knew the correct explanation about this energy-fluid but they named this solution as dark energy.

Now the question is, what actually the dark energy is?
It should be right to say more is unknown than is known. But we know how much dark matter is because we know how much it affects the universe's expansion.
Dark energy is roughly 68% and dark matter is 27% while normal matter is just 5% in this universe.

As we haven’t observed dark energy yet, so only we have explanations in the name of information. So, there is lot of explanations about it , which is given by different scientists.

One explanation says that it is a property of space. Albert Einstein was the first who realized that the space is not actually empty. The space has different amazing properties and one of them was discovered by Einstein, that it is possible for more space to came into existence.

Then comes another version of Einstein’s gravity theory, that contains cosmological constant which predicts that empty space posses its own energy. Because it is the property of space itself, that’s why this energy doesn’t dilutes with the expanding space.

As more space came into existence, more of this energy of space would appear, and as a result this energy would cause the universe to expand faster and more faster.

Another explanation about dark energy tells that dark energy is a different kind of dynamic fluid or field. Something that fills the universe but something whose effect on expansion of universe is opposite to normal matter.

Some theorist named it ‘quintessence’, but if quintessence is the answer, still we don’t know what it  is, with what it interact with and why does it exists. Mystery still continues.

Another explanation says that the space is full of temporary particles that continuously forms and disappears. When scientists tried to calculated the energy then the answer comes too much wrong.

Possibilities about dark energy are  :- this is the property of space, or a dynamic fluid or we needs new theory of gravity.

We talk a lot about dark energy, now lets know about dark matter.

According to theoretical model, dark matter consist of about 27%of total universe. Firstly dark matter should not be present in the form of planet or star, it must be present as very small particles. Another thing that it is not present in the form of dark clouds of normal matter.

As the normal matter is made up of particles called baryons and baryon is detectable due it absorbs radiation passing through so possibly dark matter is non-baryonic in nature. And it is not even possible that dark matter could be antimatter because antimatter on interaction with matter emits different gamma rays that not detected even now.

Does there is any possibility that there should be nothing like dark matter or dark energy?

There are some evidences that may prove this all.
First evidence about dark matter is that according to calculations there are many galaxies that would fly instead they are moving or rotating or formed, if they did not contain large amount of unseen matter.
Other evidences is about observations of gravitational lensing and this all is enough to show the existence of dark matter and dark energy.
Hope the mystery of dark matter should solved in future.

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