Note4Students

From UPSC perspective, the following things are important :

Prelims level: Dark Energy, Dark Energy

Mains level: Theory of expansion of the universe

Last week, an international team of researchers has made the first direct detection of dark energy.

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.
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 is an unknown form of energy that affects the universe on the largest scales.
The first observational evidence for its existence came from measurements of supernovae, which showed that the universe does not expand at a constant rate; rather, the expansion of the universe is accelerating.
Prior to these observations, it was thought that all forms of matter and energy in the universe would only cause the expansion to slow down over time.
Measurements of the cosmic microwave background suggest the universe began in a hot Big Bang, from which general relativity explains its evolution and the subsequent large-scale motion.
Without introducing a new form of energy, there was no way to explain how an accelerating universe could be measured.

Since the 1990s, dark energy has been the most accepted premise to account for the accelerated expansion.
As of 2021, there are active areas of cosmology research aimed at understanding the fundamental nature of dark energy.

Everything we see – the planets, moons, massive galaxies, you, me, this website – makes up less than 5% of 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.

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