What is dark energy, and have scientists finally detected it? | EXPLAINED

ASME IITR Chapter
4 min readOct 4, 2021

Dark energy, you must have heard its name somewhere, but do you know what it is? The more you will learn about it, the more interesting it gets. Intrigued by dark matter and dark energy for decades, it is still a mystery for scientists and physicists. But recently, a group of cosmologists suggested we don't need to dig more in the cosmos. It has been detected right here on earth. How much of it is white, and how much is black? Let us find out in this blog.

What is Dark Energy?

So, first things first, what exactly is dark energy? Physicists have known for years that the universe is expanding and growing larger every second. Some discoveries of the late 1990s suggested that the universe is increasing at an accelerating rate, which was strange to discover. It is weird because we all know that gravity is supposed to pull galaxies together with its attractive force, yet the universe is expanding. Sounds strange?

Well, that's how the theory of dark energy came into the picture. Much like dark matter, there are various theories for dark energy. What's more interesting about this thing is that it is dominant in the universe, but we still don't know about it. This 'invisible energy is supposed to cover 68% of all the mass in the universe.

Dark Energy vs Dark Matter

Dark matter is another strange thing that exists in this universe. It consists of about 27% of the mass of the universe. While dark energy is supposed to be the reason for the universe's expansion, dark matter is responsible for holding and attracting galaxies together. We know a lot more about dark matter than dark energy since it was discovered much earlier in the 1920s than the latter in the 1990s.

Many large-scale experiments are being conducted to detect traces of dark matter, but dark energy is a whole different story and hard to catch. It works by searching the sign of dark matter hitting ordinary matter. Some theoretical physicists believe there’s an entire dark realm of particles and forces out there, just waiting to be discovered

Experiment to detect dark energy

One experiment to detect dark matter is XENON1T, The XENON1T experiment is the world’s most sensitive dark matter experiment and was operated deep underground at the INFN Laboratori Nazionali del Gran Sasso in Italy. In this experiment, a tank filled with 3.2 metric tons of ultra-pure liquid xenon and fitted with arrays of photomultiplier tubes. It's completely sealed and utterly dark, so researchers can detect the flash of electroluminescence as particles interact, resulting in a tiny shower of electrons from the xenon atoms in what's known as electron recoil.

Recently, a XENON team reported some uncertainties in their experiment, and dark energy could be responsible for it. “Basically there’s some background noise and the electrons in XENON1T will on 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.” This suggests that experiments that detect dark matter could also work for detecting dark energy. "It was really surprising that this excess could in principle have been caused by dark energy rather than dark matter," Vagnozzi said in the release. "When things click together like that, it's really special."

Conclusion

Even though people are all excited over this discovery, we are still not 100 per cent sure whether it’s true or not. Some astronomers have their doubts too. “If it’s true, it’s a stunning discovery,” University of California, Berkeley astronomer Alexei Filippenko, who was not involved in the study, told inverse.com. “But a lot remains to be done to verify whether it’s true.” Now that we know that we can look for things in the detector. We can improve our techniques in future experiments. Although we all love this hypothesis, we need to wait for it get confirmed. One day, all these mysteries of the universe will reveal.

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ASME IITR Chapter

The ASME Student Chapter at IIT Roorkee is an undergraduate club of students majoring in various fields of Engineering.