Dark matter is as tangible as stars and planets to most astronomers. We routinely map it out. We conceive of galaxies as lumps of dark matter with dabs of luminous material. We understand…

Ask a group of physicists and philosophers to define “space” and you will likely be stuck in a long discussion that involves deep-sounding but meaningless word combinations such…

Physicists have always hoped that once we understood the fundamental laws of physics, they would make unambiguous predictions for physical quantities. We imagined that the underlying…

On the morning of Dec. 7, 1979, a 32-year-old Alan Guth woke up with an idea. It had come into his head the previous night, but now, in the light of a California day, he could see…

He is one of those dark matter people,” Mordehai Milgrom said about a colleague stopping by his office at the Weizmann Institute of Science. Milgrom introduced us, telling me that…

Even though we know that ordinary matter accounts for only about one-twentieth of the universe’s energy and a sixth of the total energy carried by matter (with dark energy constituting…

In his short story “The Garden of Forking Paths,” the Argentinian writer Jorge Luis Borges describes a present that can, at any moment, bifurcate into different futures—an endless…

For an empirical science, physics can be remarkably dismissive of some of our most basic observations. We see objects existing in definite locations, but the wave nature of matter…

Once you start poking around in the muck of consciousness studies, you will soon encounter the specter of Sir Roger Penrose, the renowned Oxford physicist with an audacious—and quite…

The nature of consciousness seems to be unique among scientific puzzles. Not only do neuroscientists have no fundamental explanation for how it arises from physical states of the brain,…