What is dark energy? Have scientists detected it finally?

Syllabus: General Studies Paper 3

Context:

With the help of advanced technologies and newer experiments scientists have found certain clues about dark energy and made the first putative direct detection of dark energy.

Key Points

• 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.
• Scientists noticed certain unexpected results in the underground experiment and write that dark energy may be responsible for it.
• The finding also suggests that experiments like XENON1T, which are designed to detect dark matter, could also be used to detect dark energy.

Dark energy Vs Dark matter

• In the universe, about 27% is dark matter and 68% is dark energy.
• While dark matter attracts and holds galaxies together, dark energy repels and causes the expansion of our universe.
• Dark energy has been noted as “the most profound mystery in all of science”.

How did they make the detection?

• Last year, the XENON1T experiment reported an unexpected signal.
• Scientists say 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.
• Though these sorts of excesses are often flukes, once in a while, they can also lead to fundamental discoveries.

What if the signal was caused by some other force?

• Chameleon screening: The team constructed a physical model, which used a screening mechanism known as chameleon screening, to show that dark energy particles produced in the Sun’s strong magnetic fields could explain the signal seen in XENON1T.
• Fifth force: There are four fundamental forces in our universe, and speculative theories have proposed a fifth force – something that can’t be explained by the four forces.
• To hide or screen this fifth force, many models for dark energy use special mechanisms.
• Other Projects: Scientists are hopeful that upcoming upgrades to the XENON1T experiment and similar experiments such as LUX-Zeplin – a next-generation dark matter experiment located at the Sanford Underground Research Facility, and PandaX-xT – another project at China Jinping Underground Laboratory could help directly detect dark energy within the next decade.

The Indian Express Link:

https://indianexpress.com/article/explained/what-is-dark-energy-have-scientists-detected-it-finally-7534930/

Question: Write a short note on dark energy and dark matter.