Take a look into the sky with or without a telescope and you will see stars, galaxies, planets, comets, asteroids; all those things just make 4 percent of the universe. According to the current model of cosmology, known universe; so far contains 4.9% of the matter, we are familiar with or you can say ordinary matter, 68.3% dark energy and remaining 26.8% is dark matter. Dark matter and Dark energy are the stuff that astronomers cannot see, comprehend or detect. What is dark matter and dark energy? The answer is simple, we don’t know. Below is the rough overview of dark matter and dark energy.
Dark energy can be defined as, "The hypothetical form of energy in cosmology and astronomy that invades all of space and tends to accelerate the expansion of the universe is known as Dark energy."
There is no way (so far) that we can see dark energy, but we can detect it by only one of its effect. As dark energy exists so it surely has an effect on other things, but with the help of our technology, we are able to detect it by only one of its effect and that is expansion of universe. According to the observations of Edwin Hubble; scientists believed that the universe must have a beginning and named it as a Big Bang. Astronomers observed a very far supernovae and it transformed the picture of Big Bang Theory in our minds. It had frequently been thought that the matter in the universe would probably slow the rate of its expansion. Mass produces gravity and the property of gravity is to pull everything near it and thus this pull can easily slow down the rate of expansion of the universe as we know it, but observations of a far away supernova showed that instead of slowing down the rate of expansion is rapidly increasing. We do not know what actually is causing this so in order to explain this, scientists introduced another term of “Dark Energy”. We do not know what dark energy actually is but we can easily see its effect on the universe mostly in the form of increasing the rate of expansion of the universe. The simplest description for dark energy is that it is basically the "cost of occupying space": that is, a volume of space has some essential and fundamental energy. This is also known as the cosmological constant.
We can define dark matter as a “Hypothesized form of matter to replace a large portion of the mass in cosmology and astronomy that seems to be absent from the universe and it cannot be seen directly with telescopes or any other technology created by man so far.” Dutch astronomer Jan Oort was the first person to interpret evidence and the presence of dark matter. In 1939, Babcock described in his PhD thesis measurements of the rotation curve for the Andromeda nebula which recommended that the mass-to-luminosity ratio upsurges centrifugally. Later more observation of galaxies and their luminosity showed that a large amount of mass is missing or is invisible to us. This invisible matter afterwards named as "Dark Matter". Scientists now believe that dark matter is made up of Weakly Interacting Massive Particles (WIMPs). These Weakly Interacting Massive Particles have negligible interactions with matter. Detecting Weakly Interacting Massive Particles is now a challenge for scientists and everyone is looking at scientists working in the Large Hadron Collider where scientist thinks that they can make WIMP.
