What are some biggest mysteries of the universe from a long time?

1.What Is Dark Matter?

Astrophysicists are currently trying to observe the effect of dark energy, which accounts for some 70 percent of the universe. But it's not the only dark stuff in the cosmos: roughly 25 percent of it is made up of an entirely separate material called dark matter. Completely invisible to telescopes and the human eye, it neither emits nor absorbs visible light (or any form of electromagnetic radiation), but its gravitational effect is evident in the motions of galaxy clusters and individual stars.

2. The Moon’s Magnetic Field

One of the moon’s greatest mysteries—why only some parts of the crust seem to have a magnetic field—has intrigued astronomers for decades, even inspiring the buried mythical “monolith” in the novel and film 2001: A Space Odyssey. But some scientists finally think they may have an explanation.

Others, though, believe the magnetic field may be related to other smaller, more recent impacts.

3. Is There Anybody Out There?

In 1961, astrophysicist Frank Drake devised a highly controversial equation: By multiplying together a series of terms relating to the probability of extraterrestrial life

He surmised that the existence of intelligent life on other planets is extremely likely. One problem: Roswell conspiracy theorists notwithstanding, we haven’t heard from any aliens to date. Recent discoveries of distant planets that could theoretically harbor life, though, have raised hopes that we might detect extraterrestrials if we just keep looking.