Scientists have a knack for mathematically predicting the secrets of the universe. In physical form, Gravitational waves were detected 100 years after the prediction of their existence. Now, 22 years after their prediction, early signs suggest that Dark Energy has been discovered.
Dark energy detected
A study led by Cambridge University suggests that there is finally physical proof of the existence of dark energy. In 2020, researchers working on the XENON1T project in Italy detected a signal. This was detected despite the fact that the experiment had been designed very carefully so that no microscopic interference from the outside world could interrupt it. Minimal interference in the experiment has the potential to change the final result by thousands of percentages. This signal was not being expected by anyone involved in the experiment, so they started their research on the origin and effects of this signal.
Firstly, scientists thought that this signal had been caused by dark matter. To test their hypothesis, they conducted an experiment in which they modulated interaction between dark matter and the sun in such a way that the speed of dark particles could be slowed down and measured on the earth. But, the experimental data collected from the experiment made scientists realise that signals may have been caused by dark energy and not dark matter.
This experiment is known as chameleon screening. Dr Sunny Vagnozzi explains it as “Imagine two people carrying something, one heavy object and other one a light object. The person with the light object will most likely make it further. Similarly, here the fifth force carried by this heavy chameleon in a dense environment doesn’t make it far.”
Dr Sunny Vagnozzi, the author of the paper explained how scientists derived this conclusion. He said- “Basically there’s some background noise and the electrons in XENON1T will on the average move a bit on their own even with no dark matter or dark energy around simply by virtue of “kicks” due to this background,”. Describing the exact mechanism of detection of the signal, he said-“We saw that at energies around ~2 keV there are way more events than one expects simply due to noise and this could be due to dark energy”.
Composition of our universe
Cosmologically, our universe is made up of three kinds of particles. Ordinary matter which consists of me, you, your mobile/laptop screen on which you are reading this and every other observable particle. Ordinary matter is only 5 per cent of this universe. The other 95 per cent is divided into dark matter and dark energy.
Dark matter
Dark matter is basically a non-luminous (which does not emit light) material that exists in space around us. They are not visible to me and you, because they do not emit light. They could exist in various shapes and sizes. Either they are very small particles or they are extremely large in size. If they are extremely small in size then they are infinite in number and exist everywhere around us. On the other hand, if they are large in size, then their quantity can be counted. Dark matter is responsible for attracting and holding the galaxies together. Dark matter consists of about 27 per cent of the rest 95 per cent of the universe.
Dark energy
Dark energy is said to be a form of energy that acts exactly opposite to attractive gravitational forces operating between different particles in the universe. For the better part of the 20th century, scientists believed that the universe is expanding, but at a point, gravitational forces will bring galaxies together in the future. But, late 1990s data suggested that the expansion of the universe has caught acceleration over a period of time negating the effect of gravitational force. Scientists postulated in 1998 that powerful energy must be creating greater repulsive force than the attraction of gravitational force. This energy was termed dark energy. Dark energy comprises about 68 per cent of the universe.
The Universe runs on the balancing wheel of order and chaos
Dark energy makes the universe expand its length and breadth. If left alone, the dark energy will disrupt everything as it will take away everything it has its effect on. That’s where dark matter comes in. Dark matter does not allow stars, galaxies etc to fly along with the influence of dark energy. Dark energy accelerates the expansion of the universe, while dark matter slows down the expansion. Simply put, dark energy is the chaos constantly pushing the limits of the universe, while dark matter is the order keeping the things in their proper form and place. Both the dark matter and dark energy together provide a balance to the universe.
While dark matter had been predicted way before in 1920, dark energy was predicted only in 1998. Various other researches have been conducted by scientists to understand the significance of both dark matter and dark energy. Sanford Underground Research Facility called LUX-Zeplin and Panda-XT, another project at China Jinping Underground Laboratory are some of the key projects involved in decoding the universe.