Mysterious dark matter makes up 85 percent of matter in the universe, and of the remaining 15 percent, scientists couldn’t ...

Cosmic microwave background data support cosmology’s standard model but retain a mystery about the universe’s expansion rate.

For decades, astronomers have known something didn’t add up in our universe. The amount of “normal” matter—stars, gas, and ...

The cooled remnant of the first light that permeated the universe is known as the cosmic microwave background—leftover radiation from the Big Bang that can still be detected in the distant universe.