Dark Energy: A mysterious force

Does Dark energy really exist?

Dark energy is a mysterious force that's causing the rate of expansion of our universe to accelerate over time, rather than to slow down. After Big Bang, the universe began expanding outwards. Scientists once thought that it would eventually run out of energy and slow down as gravity pulled the objects inside it together. Our Universe is full of matter. As matter attracts other matter, the mutual interactions will slow down the expansion. But studies of distant supernovae revealed that the universe today is expanding faster than it was in the past, not slower, indicating that the expansion is accelerating. This would be possible if the universe contained enough energy to overcome gravity: dark energy. This energy is counteracting gravity.

It is speculated that 68% of the universe is made up of dark energy, while 26% makes up dark matter and 5% contains the normal matter that we are made up of. Dark energy is one of the greatest unsolved mysteries of cosmology whose nature and origins are unknown! Many people are found asking questions like," Will dark energy continue to accelerate the Universe?" Albert Einstein was the first person to put forth the fact that space isn't empty. As it expands, it is filled with energy, most of which is dark energy. 

There are three main theories that explain the existence of dark energy. The first one says that the Universe is filled with a changing energy field called Quintessence: a hypothetical form of dark energy postulated as an explanation for the accelerating of our Universe. The second theory straight up says that our interpretation of gravity has been wrong and there's more to it than humans know right now. The third theory states that dark energy is is a property of space that helps it to expand. "What is the nature of dark energy?" is the most pressing scientific problem of coming decades. 

For example, a spiral galaxy doesn't have enough mass to keep everything in place. As it rotates, it should disintegrate shedding stars and gas in all directions. Either the spiral galaxy violates the gravitational laws or it is the dark energy holding it in its place.