For years, cosmologists have argued over a simple question with an awkward answer: How fast is the universe expanding right ...

The night sky deceives us. The universe should be ablaze with starlight, yet it isn’t. Discover how the finite speed of light, cosmic expansion, and invisible radiation from the Big Bang—the Cosmic ...

For decades, astronomers were certain that half of the ordinary matter in the universe — protons and neutrons, the building blocks of everything we see — had simply gone unaccounted for. The cosmic ...

Ripples in the fabric of space-time called gravitational waves may be the key to solving the Hubble tension — one of the biggest nagging problems in physics.

(via Sabine Hossenfelder) In the Big Bang Theory, the cosmic microwave background — microwave-range radiation that floats through the entire universe at a steady 2.7 Kelvin — is evidence that a hot ...

The events surrounding the Big Bang were so cataclysmic that they left an indelible imprint on the fabric of the cosmos. We can detect these scars today by observing the oldest light in the universe.

Scientists are reeling from an unexpected blow after news that a much anticipated future observatory—designed to decipher the earliest moments of cosmic history—won’t be able to proceed with its ...

Observations show the universe appears flat, yet its true size and global shape beyond the observable horizon may remain forever unknown.

The cosmic microwave background, shown at left in this illustration, is a flash of light that occurred when the young universe cooled enough for electrons and protons to form the first atoms. It ...