Dark matter is an invisible substance that makes up most of the universe's mass.
The Great Attractor is a mysterious region of space that seems to be pulling galaxies towards it.
In 1977, a radio signal was detected from space that was so unusual it was named the Wow! Signal.
The Pioneer spacecraft, launched in the 1970s, experienced an unexplained deviation from its predicted path.
The Kuiper Belt is a region of space beyond Neptune that contains thousands of icy objects.
Lunar swirls are bright and sinuous features on the moon's surface that are still a mystery.
In 1908, a massive explosion occurred over a remote region in Russia known as the Tunguska Event.
The Fermi Paradox asks the question: if the universe is teeming with intelligent life, why haven't we heard from them yet?
The Black Hole Information Paradox is the question of what happens to the information that enters a black hole.
The Cosmic Microwave Background Radiation is the afterglow of the Big Bang.