1 Cosmic Microwave Background (CMB), initially detected in the 1960s in the form of a radio noise, it was misinterpreted as a signal from an extraterrestrial life form.
2 Micro black holes, there's a new "braneworld" theory of gravity, according to it, there are thousands of tiny black holes scattered throughout our solar system, how tiny? Imagine an atomic nucleus.
3 Dark matter, scientists have theorized that it accounts for 85% of matter in the universe. Unfortunately, modern technology is not advanced enough to detect dark matter. As a result, it has remained elusive to the entire science community, because of this uncertainty, many scientists have even doubted its existence.
4 Galactic cannibalism, sometimes galaxies can "eat" each other, by "eating", we mean two galaxies colliding and to some extent merging with each other.
5 Gravity waves, in his theory of general relativity, Einstein talks about ripples in the fabric of space time, these are known as gravity waves.