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 ...

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

The shape of the universe is one of the most important questions in cosmology, with far-reaching implications, up to and including the ultimate fate of the cosmos. For decades, we've been measuring ...

Dark matter and gas in the universe. There may be more dark matter than we think. Credit: Illustris, CC BY-SA No matter how elegant your theory is, experimental data will have the last word.