Cold gas does not look dramatic at first glance. Neither does dust. Yet those two quiet ingredients sit at the center of a ...

Scientists know that the elusive substance called dark matter makes up most of all the matter in the universe, but have never ...

By studying galaxy clusters separated by hundreds of millions of light-years, Penn physicist Patricio Gallardo and ...

Gravity has been tested extremely well inside the solar system. On cosmic scales, direct tests are harder. This study pushes ...