Cosmic Microwave Background Radiation
The speed of light enables us to observe the universe’s earliest remnants—the cosmic microwave background radiation (CMB). This faint glow, detected in all directions, represents ancient photons emitted roughly 380,000 years after the Big Bang. Because light travels at a finite speed, we’re essentially looking back in time, observing radiation that has journeyed billions of years to reach us.
Analyzing the CMB has provided compelling evidence for the Big Bang theory, offering clues about the universe’s infancy, its subsequent evolution, and even its ultimate fate—making it one of cosmology’s most profound discoveries.