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Matter as we know atoms, dust, rocks, trees, living organisms, planets, stars and even galaxies forms only 5% of our known universe. This doesn’t seem right does it? Then what makes up the remaining 95%, emptiness??? The answer is dark matter and dark energy, 25% is dark matter and remaining 70% is dark energy. What do you mean by dark matter and dark energy, how does it appear, or what properties does it exhibit? Scientists have not yet observed dark matter directly. It doesn't interact with baryonic matter and it's completely invisible to light and other forms of electromagnetic radiation, making dark matter impossible to detect with current instruments.

This means it does not absorb, reflect or emit light, making it extremely hard to spot. But scientists are confident it exists because of the gravitational effects it appears to have on galaxies and galaxy clusters. Dark energy is the name given to the force that is believed to be making the universe larger. Distant galaxies appear to be moving away from us at high speed: the idea is that the universe is getting bigger and has been since the Big Bang. Measurements are now accurate enough to allow astronomers to tell that these galaxies seem to be accelerating away from us. The universe is expanding at an increasing rate.

This faster and faster expansion is not understood by scientists. There are many ideas for what might be causing the rapid expansion. However, at the moment, cosmologists who study it do not have an answer. It is as if there was something there in
empty space providing a repulsive force (Anti- gravity) that makes the universe expand. This has been named dark energy. In the 1930s, Swiss-born astronomer Fritz Zwicky studied images of the roughly 1,000 galaxies that make up the Coma Cluster — and he spotted something funny about their behavior. The galaxies moved so fast that they should simply fly apart. He speculated that some kind of “dark matter” held them together. Decades later, astronomers Vera Rubin and Kent Ford found a similar phenomenon when they studied the rotation rates of individual galaxies. The stars at a galaxy’s outer edge should circle slower than stars near the centre. That’s the way planets in our solar system orbit. Instead, they noticed that the stars on a galaxy’s outskirts orbit just as fast — or faster —than the stars closer in. Rubin and Ford had found more evidence that some invisible form of matter is apparently holding the universe together. Two astronomers have devised a method that let them “see” dark matter with the light from rogue stars. The pair has shown how images of faint starlight taken with the Hubble Space Telescope can be used to map dark matter’s distribution in galaxy clusters.

Albert Einstein was the first person to realize that empty space is not nothing. Space has amazing properties, many of which are just beginning to be understood. The first property that Einstein discovered is that it is possible for more space to come into existence. Then one version of Einstein's gravity theory, the version that contains a cosmological constant, makes a second prediction: "empty space" can possess its own energy. Because this energy is a property of space itself, it would not be diluted as space expands. As more space comes into existence, more of this energy-of-space would appear. As a result, this form of energy would cause the universe to expand faster and faster. More deeper understanding and research is yet needed to be carried out in order to fully explore the endless possibilities of dark matter and dark energy.
Adrian Dsouza