The constancy of the speed of light is a pillar of modern physics, but questions persist about its absolute universality.

For hundreds of a millions of years, the universe existed in the dark ages—an epoch when only primordial gasses existed. Then, a period of reionization, cleared away this foggy existence an introduced ...

Light speed would allow instant trips across Earth and minutes to reach the Sun, but even at 300,000 km/s the expanding ...

The universe's expansion means its size is bigger than its age suggests. The universe's expansion doesn't have a speed limit like objects within it. Distant galaxies move away from us as space itself ...

Over billions of years, the universe's stars and galaxies shined their light into space, leaving behind an imperceptibly faint night light known as the cosmic optical background. NASA's New Horizons ...

My telescope, set up for astrophotography in my light-polluted San Diego backyard, was pointed at a galaxy unfathomably far from Earth. My wife, Cristina, walked up just as the first space photo ...

The first stars in the universe are theorized to be made of pure helium, hydrogen, and some lithium before seeding other metals through supernova explosions. Credit: NAOJ illustration If you've ever ...

Astronomers have discovered what could be the largest black hole ever detected. With a mass of 36 billion times that of our Sun, its gravity is so powerful that it bends the light of an entire galaxy ...

Here is the history of light, according to physics. Beyond what we can touch, taste, smell, and hear, we experience the universe through light. But how did we come to discover light, and how did we ...

Themiya Nanayakkara receives funding from Australian Research Council Laureate Fellowship FL180100060. About 400,000 years after the Big Bang, the cosmos was a very dark place. The glow of the ...

Banner image: Artist's depiction of the New Horizons spacecraft billions of miles from Earth. (Credit: NASA, APL, SwRI, Serge Brunier/ESO, Marc Postman/STScI, Dan Durda) Scientists have traveled to ...

What if the universe isn't as spontaneous as it seems? What if the galaxies, the laws of physics—even you—are all running on code? It's a theory that's captivated scientists and sci-fi fans alike. And ...