In the mid-1990s, I studied mathematics. I wasn’t really sure just what I wanted to do with my life, but I was awed by the power of mathematics to describe the natural world. After…

The name of the image—the “Flammarion engraving”—may not ring a bell, but you’ve seen it many times. It depicts a traveler wearing a cloak and clutching a walking-stick;…

Before there is life, there must be structure. Our universe synthesized atomic nuclei early in its history. Those nuclei ensnared electrons to form atoms. Those atoms agglomerated…

How do you feel about the multiverse?” The question was not out of place in our impromptu dinner-table lecture, yet it caught me completely off-guard. It’s not that I’ve never…

Experimentalists are the cowboys of physics,” says Melissa Franklin, an experimental particle physicist at Harvard University. They have to be able to tell theorists, “I don’t…

When they met, Einstein wasn’t Einstein yet. He was just Albert Einstein, a kid, about 17, with a dark cloud of teenage angst and a violin. Michele Besso was older, 23, but a kindred…

At 2:40 a.m., my phone woke me up. At least one of us was always on shift, and that night in September of 2010, I had volunteered to respond to automated text messages from our alert…

Of all the bizarre facets of quantum theory, few seem stranger than those captured by Erwin Schrödinger’s famous fable about the cat that is neither alive nor dead. It describes…

I doubt that any phenomenon, real or imagined, has inspired more perplexing, convoluted, and ultimately futile philosophical analysis than time travel has. (Some possible contenders,…

As a cosmologist, some of the questions I hear most frequently after a lecture include: What lies beyond our universe? What is our universe expanding into? Will our universe expand…