What are the most mysterious unexplained phenomena in the universe?
Here is a list of some of the most mysterious unexplained phenomena in the universe:

*  Fast Radio Bursts: Mysterious and powerful pulses of radio energy that have been detected from distant galaxies.

*  Dark Matter: A mysterious form of matter that makes up around 84 percent of the universe but cannot be seen or measured.

*  Gamma-Ray Bursts: High-energy explosions that occur in distant galaxies, releasing more energy than the Sun does in its entire lifetime.

*  Cosmic Inflation: An accelerated expansion of the early universe that happened in a fraction of a second, but had a profound effect on the universe's structure today.

*  Dark Energy: A mysterious form of energy that is thought to make up around 68 percent of the universe and is responsible for its accelerating expansion.

*  Neutrino Oscillations: The mysterious ability of neutrinos to switch between different forms, which is still not completely understood.