# The Unseen

The visible universe-including galaxies,stars and planets only make up 4 percents of the universe (REALLYYYY). What about another 96 percents of it? In reality, another 96 percents consists of the thing that is unseen. Besides, we can’t really identify or perhaps understand what that 96 percents is made up of. From the perspective of the scientists, they called it as a dark energy or dark matter. Why is it called as a dark matter/dark energy? (Say yes if you want to know more…kidding)

Dark matter is an unidentified type of matter and it does not interact with electromagnetic radiation (i.e. light), hence make it invisible to the electromagnetic spectrum. On the other hand, dark energy is basically an unknown form of energy which is have a direct relation with the accelerating rate of expansion of universe. However, it still remain as a hypothesis for the scientists.

According to the standard model of cosmology, dark energy contributes 68.3 percents of the total energy in the present observable universe. The mass–energy of dark matter  contributes 26.8 percents while ordinary matter contributes 4.9 percents. If I were to explain these dark matter and dark energy,it is going to take forever….(I’m not even a scientist but probably will).

Dark energy and Dark Matter

How do the dark energy have impact on the acceleration rate of the expansion of the universe? Dark energy has a unique property which is it has negative pressure which is distributed relatively homogeneously in space.

From this equation, it yields out a constant value for w (cosmic acceleration) thus prove that the universe is expanding with an accelerating rate. The derivation of this acceleration is shown in the link below.

Accelerating universe

The main point is we can work through a lot of mathematical formulas and do some estimation on the gravitational pull of these entities. However, there is no guarantee of proving what the unseen or so called invisible part of our universe is made up of but we do know that they are exist. Although it still remain as a hypothesis, the majority of the universe may still remain as a mystery. I provided a video in the link below which help to explain the dark matter and dark energy in a more intuitive way.

What is Dark Matter and Dark Energy?

## 7 thoughts on “The Unseen”

1. I had heard of dark matter before, but I did not understand what it was or what dark energy was. It is interesting that there are forces which can bend spacetime or cause the universe to expand faster, yet we cannot see or observe them. After looking at the links, it surprised me that scientists were so shocked about the universe’s accelerated growth, as seen in the equation above. Although we do not have the technology yet, it seems like humans should consider the potential long-term effects of these forces’ expanding presence and massive impact on the universe.

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1. Hey Victoria, it is a good thought process and I do understand about your concern.Basically, it has no impact to our universe since all the galaxies, stars and planets are held together by gravity. Intuitively, the properties of our universe would not change. However, scientists have listed all the possibilities and theories to discover more about this unseen matter. Hopefully, in the future, we could really understand how does dark matter and dark energy work.

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2. I find the idea that dark energy has negative pressure to be extremely interesting. Discussing how dark energy proves the constant rate of expansion of the universe was an interesting way to take the topic, but I also wish that there was more of a discussion of how dark matter affects the universe and its rate of expansions.

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1. Hey vandyastro, from my previous reading, the one who involves in the expansion of the universe is dark energy. Dark matter have several impacts to the universe (proof for existence of dark matter). One of them is dark matter creates a so-called gravitational lensing. Scientists can see light bent from the gravity of invisible objects and measure that stars are orbiting around in their galaxies faster than they should be. However vandyastro, I could not explain further since I might get wrong somewhere but thanks for the question.

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1. Thanks so much! This was extremely informative.

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3. What a mysterious yet exciting stuff this dark energy is. I think dark matter is interesting as we cannot see it yet it contributes majority of the total energy in the universe *sigh* . Also, the universe has always managed to intrigue me with its vastness and “what’s out there” because apparently we are only 4% of the whole universe! But then again, how do the scientists know that we are only 4%? Also, what do you mean that the dark energy has negative pressure?

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1. Hey Naz, to answer your first question, the scientists only make an approximation since there is something out there which have gravitational effects it have on galaxies and galaxies cluster. Besides, we know it is a lot out there and invincible and therefore scientists called it as dark matter. For dark energy, scientists saw the existence of force that repels gravity thus they called it dark energy. To put in a simple word, if you stare at the sky during the night time, you will see a lot of spaces between stars but you are not sure what is present there. The negative pressure has relation with the accelerated expansion of universe. Pressure is equal to force over area thus negative pressure indicates that the force is pointing the other direction thus cause the expansion of the universe. To give some simple example, if the sofa in your house expand, it exerts negative pressure since the expansion of the sofa is compared with the free space outside of the sofa.

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