Twice on a recent Friday, the cosmos intruded rudely on us earthlings. A meteor exploded over western Siberia, shattering windows, injuring hundreds and scaring pretty much everyone else. That same day, an asteroid passed within 18,000 miles of us, close enough to arch many an eyebrow among astronomers.

One earthling, at least, looked on the bright side.

“It allows me, when I talk about asteroids, to reference an actual event where people got hurt,” said Neil deGrasse Tyson, an astrophysicist and the director of the Hayden Planetarium in Manhattan for going on two decades. Not that Dr. Tyson was glad that people had been injured. Far from it. All the same, he said over drinks in Lower Manhattan, this cosmic activity “gives punctuation to my sentence that the human race is at risk.”

“Think of it,” he said, “as a shot across our bow.”

A warning that the planet could be imperiled has a way of focusing the mind wondrously. So we asked about a huge asteroid called Apophis, whose name alone ought to give one pause.

“It’s from the Egyptian god of death and destruction,” Dr. Tyson said. “It was named knowing that it crosses Earth’s orbit.” Otherwise, he said, “we would have named it something less threatening, like Tiffany or Bambi.”