Cosmologists have spent decades trying to pin down exactly how fast the universe is flying apart and whether that rate is ...

Cosmological redshift depends upon a galaxy's distance. Credit: NASA/JPL-Caltech/R. Hurt (Caltech-IPAC) In 1929 Edwin Hubble published the first solid evidence that the universe is expanding. Drawing ...

Light released by a distant star does not simply wink out after crossing some threshold of space. In a vacuum, photons keep moving indefinitely, and astronomers routinely detect light that has ...

Do constants of nature—the numbers that determine how things behave, like the speed of light—change over time as the universe expands? Does light get a little tired traveling vast cosmic distances? It ...