Relativity

A timely Q&A with physicist Sean Carroll about how our one-way trip from past to future is entangled with entropy and the origin of the universe

Modifications to the theory of gravity could account for observational discrepancies, but not without introducing other complications

The ripples in spacetime predicted by general relativity remain one of the most sought-after prizes in physics, and new research narrows estimates of their prevalence

Acting Editor in Chief Mariette DiChristina introduces the August 2009 issue of Scientific American

The possibility of "swimming" and "gliding" in curved, empty space shows that even after nine decades, Einstein's theory of general relativity continues to amaze

An object hundreds or thousands of times the mass of the sun would represent an elusive class of black hole

Entanglement, like many quantum effects, violates some of our deepest intuitions about the world. It may also undermine Einstein's special theory of relativity

The gravitationally repulsive presence, thought to make up most of the universe, shows its effect on the development of galaxy clusters

New studies track the motion of stars to pin down what holds sway at the heart of our galaxy

Rumors of data mishandling in an historic eclipse study don't gibe

Proposed effect, to slow the fall of a rapidly vibrating molecule, faces skepticism