Black holes that formed before the Big Bang could still exist today as ‘cosmic fossils’, potentially helping to explain the mysterious dark matter that shapes galaxies across the Universe, according ...

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

Astronomers have long struggled with a troubling puzzle: a significant portion of normal matter in the universe appeared to be missing. Scientists knew this matter had to exist based on predictions ...

Gravity, as most people understand it, is the familiar force that pulls a falling apple toward Earth. But for astronomers and theoretical physicists, it is also a vexing invisible architect that ...

Penn physicist Patricio Gallardo and collaborators tracked the speeds of distant galaxy clusters to test the strength of gravity across hundreds of millions of light-years. The verdict? Gravity neatly ...