II. Why Do We Dream?
Almost everyone dreams, but no one knows exactly why.
Some researchers believe dreams help organize memories. Others think they allow the brain to process emotions or prepare for future situations.
Although brain scans have revealed a great deal about sleep, the true purpose of dreaming remains uncertain.
III. The Wow! Signal
In 1977, astronomers detected an unusually strong radio signal from space that lasted only 72 seconds.
Despite decades of searching, the signal has never been detected again.
Its true origin remains unknown.
IV. Ball Lightning
For centuries, people have reported seeing glowing balls of light floating through the air during thunderstorms.
Although scientists have proposed several explanations, the exact cause of this rare phenomenon remains uncertain because it is so difficult to study.
