We all know much about the sparkling galaxies, swirling planets, the sun, moons and other wondrous celestial objects. Don’t we? But, ever thought about what lies beyond these stuff? If not, then it’s the time! Let me tell you about something mysterious, something far beyond our imagination. Read along, maybe you could be the one unveiling the mystery in the future!
The visible universe which includes Earth, the sun, other stars, and galaxies is made of protons, neutrons, and electrons bundled together into atoms. You’ll be amazed but actually, this ordinary or visible matter sums up just 5% of the actual mass of the universe.
So, here comes the question, what’s the rest made of? Well, the rest of the universe appears to be made of a mysterious, invisible substance called Dark matter (25%) and a force that repels gravity known as Dark energy (70%). The reason both Dark Energy and Dark Matter have the label “Dark” in them is because they are apparently uncharged and therefore do not interact with light.
For the past 20 years, physicists have known that the expansion of the universe is accelerating. In 1998, cosmologist Michael Turner termed this acceleration as “Dark energy”.
Dark Energy was discovered in 1998 when two separate teams of astronomers studied “Type Ia supernovae”. Both groups found out that the actual distance to the galaxies which hosted the supernovae which they were observing, were farther than they had been found using other methods. And that would be possible only if the universe was expanding at a constant velocity.
There have been several theoretical concepts that have attempted to explain Dark Energy, but none of them satisfactorily describe its effects. In fact, most are incorrect by many orders of magnitude.
The galaxies seen by astronomers are not being torn apart as they rotate. It is probably because they are generating enough gravity to prevent this.
But that, again raises a question. Astronomers can see how much visible mass there is in a galaxy and when they sum it all up, it isn’t enough for the required amount of gravity. So something else must be generating this force. So, what is it?
The galaxies must be filled with matter that astronomers can’t see. And that’s what we call “Dark matter”. Astronomers Fritz Zwicky and Vera Rubin discovered dark matter. We know it certainly that it’s out there because of its powerful gravity.
We are much more certain “what dark matter is not”, than “what it is”. First, it is dark, which means that it is not in the form of stars and planets that we see. Second, it is not in the form of dark clouds of normal matter or matter made up of particles called baryons.
The presently most popular explanation for the puzzling observations is some kind of weakly interacting particle that doesn’t interact with light. They are known as “Weakly Interacting Massive Particles.” Another assumption is a particle called the axion, which is very light but leaves behind some kind of condensate that fills the universe.
Despite successes, there are a number of mysteries yet to be revealed. The questions of dark matter, dark energy, and other such riddles of the universe guarantees that astronomy remains an active area of research for years to come.