The Greatest Mystery in the Universe
The universe is a mystery. What makes up most of it is its greatest mystery. In 2003, the National Research Council declared the question `what is the nature of dark energy?’ as one of the most pressing scientific problems of the coming decades. Michael S. Turner, a cosmologist at the University of Chicago and head of this council, described dark energy as the most profound mystery in all of science.
The universe we have always known. The stuff we can see. People, plants, buildings, stars, planets and galaxies only make about 4.9% of the universe. Another cosmic mystery known as dark matter makes up 26.8% of the universe. The largest part of the universe, 68.3% is made up of dark energy. This is according to the Planck mission team.
What Is Dark Energy?
Dark energy is the name assigned to the unknown force that is causing the acceleration of the expansion of the universe. It is a hypothetical form of energy that permeates all of space. It is a mysterious quantity that makes up most of the mass of the universe.
At least cosmologists know that dark matter could be exotic matter or ordinary matter that we haven’t detected yet. Dark energy is a complete mystery. More about it is unknown than is known. Neither its identity nor its origin is known. There are just possibilities of what it could be. Here are the ones that have been considered.
Dark energy could be a property of space. One version of Einstein’s gravity theory that included a cosmological constant predicted that one property of space is that empty space can have its own energy.
Another explanation of dark energy is derived from the quantum theory of matter. However, this theory came out wrong when astronomers attempted to calculate and explain it.
Dark energy could be a new kind of dynamical energy fluid or field. Something that fills all of space but whose effect on the universe is the opposite of matter in normal energy.
Dark energy could be exotic matter with a gravitational force that is opposite to the attractive gravity of ordinary matter.
How Dark Energy Was Detected
The universe is expanding. It has been expanding since the Big Bang. Astronomers expected that the rate of expansion of the universe would slow down due to the force of gravity. When they checked to confirm it was slowing down and find out the expansion rate, there were surprised to find out that it was accelerating.
This revelation only meant another force other than the force of gravity is the dominant force governing the expansion of the universe. It is this force that is known as dark energy.
How Do We Know Dark Energy Exists?
In the 1970s, astronomers came into an agreement that the universe is much more than what we know and see. They agreed that there is a fundamental fact about the universe that we don’t understand.
Computer simulation of our galaxy found that the center would not hold if the universe were made up of only what we know and see. There had to be something more.
The mass of the galaxy that we know is not enough to keep everything in place. As it rotates, it should disintegrate shedding stars and gas in every direction yet everything stays intact. Dark energy is the force that keeps everything in place.
The Known Properties of Dark Energy
Dark energy is anti-gravity. It has a cosmic repulsion property. It has the effect of accelerating the cosmic universe while the force of gravity is supposed to be slowing down the acceleration.
No one has ever seen dark energy. It is not visible directly. Its existence is inferred from its anti-gravitational effects on the expansion of the universe.
Dark energy remains the biggest mystery in the universe. Explorations continue to find out not only what it is but whether it changes with time and space or remains the same in all conditions. For now, dark energy remains the most acceptable explanation to the acceleration of the universe expansion.